Application of satellite remote sensing to North Carolina. Development of a monitoring methodology for trophic states of lakes in North Carolina

NASA Technical Reports Server (NTRS)

Welby, C. W.; Holman, R. E.

1977-01-01

Conjunctive study of four shallow coastal plain lakes in northeastern North Carolina and their LANDSAT-2 images demonstrates that it is possible to differentiate between the lakes and their respective trophic states on the basis of the multispectral scanner imagery. The year-long investigation established that monitoring of the trophic states of the lakes on a seasonal basis through application of color additive imagery enchancement techniques is possible. Utilizing a standard setting of the color additive viewer, an investigator can normalize the imagery to an internal standard of constant reflectance characteristics. By comparison of the false color renditions with a standard interference color chart combined with brightness measurements made on the viewer screen, one can relate the lake reflectances to their trophic states. Two or more bands of the imagery are required, and the present study established that for the lakes studied, Band 5 and Band 6 form a good combination.

Optical properties and composition changes in chromophoric dissolved organic matter along trophic gradients: Implications for monitoring and assessing lake eutrophication.

PubMed

Zhang, Yunlin; Zhou, Yongqiang; Shi, Kun; Qin, Boqiang; Yao, Xiaolong; Zhang, Yibo

2017-12-26

Chromophoric dissolved organic matter (CDOM) is an important optically active substance in aquatic environments and plays a key role in light attenuation and in the carbon, nitrogen and phosphorus biogeochemical cycles. Although the optical properties, abundance, sources, cycles, compositions and remote sensing estimations of CDOM have been widely reported in different aquatic environments, little is known about the optical properties and composition changes in CDOM along trophic gradients. Therefore, we collected 821 samples from 22 lakes along a trophic gradient (oligotrophic to eutrophic) in China from 2004 to 2015 and determined the CDOM spectral absorption and nutrient concentrations. The total nitrogen (TN), total phosphorus (TP), and chlorophyll a (Chla) concentrations and the Secchi disk depth (SDD) ranged from 0.02 to 24.75 mg/L, 0.002-3.471 mg/L, 0.03-882.66 μg/L, and 0.05-17.30 m, respectively. The trophic state index (TSI) ranged from 1.55 to 98.91 and covered different trophic states, from oligotrophic to hyper-eutrophic. The CDOM absorption coefficient at 254 nm (a(254)) ranged from 1.68 to 92.65 m -1 . Additionally, the CDOM sources and composition parameters, including the spectral slope and relative molecular size value, exhibited a substantial variability from the oligotrophic level to other trophic levels. The natural logarithm value of the CDOM absorption, lna(254), is highly linearly correlated with the TSI (r 2  = 0.92, p < .001, n = 821). Oligotrophic lakes are distinguished by a(254)<4 m -1 , and mesotrophic and eutrophic lakes are classified as 4 ≤ a(254)≤10 and a(254)>10 m -1 , respectively. The results suggested that the CDOM absorption coefficient a(254) might be a more sensitive single indicator of the trophic state than TN, TP, Chla and SDD. Therefore, we proposed a CDOM absorption coefficient and determined the threshold for defining the trophic state of a lake. Several advantages of measuring and estimating CDOM, including rapid experimental measurements, potential in situ optical sensor measurements and large-spatial-scale remote sensing estimations, make it superior to traditional TSI techniques for the rapid monitoring and assessment of lake trophic states. Copyright © 2017 Elsevier Ltd. All rights reserved.

Science for a wilder Anthropocene: Synthesis and future directions for trophic rewilding research.

PubMed

Svenning, Jens-Christian; Pedersen, Pil B M; Donlan, C Josh; Ejrnæs, Rasmus; Faurby, Søren; Galetti, Mauro; Hansen, Dennis M; Sandel, Brody; Sandom, Christopher J; Terborgh, John W; Vera, Frans W M

2016-01-26

Trophic rewilding is an ecological restoration strategy that uses species introductions to restore top-down trophic interactions and associated trophic cascades to promote self-regulating biodiverse ecosystems. Given the importance of large animals in trophic cascades and their widespread losses and resulting trophic downgrading, it often focuses on restoring functional megafaunas. Trophic rewilding is increasingly being implemented for conservation, but remains controversial. Here, we provide a synthesis of its current scientific basis, highlighting trophic cascades as the key conceptual framework, discussing the main lessons learned from ongoing rewilding projects, systematically reviewing the current literature, and highlighting unintentional rewilding and spontaneous wildlife comebacks as underused sources of information. Together, these lines of evidence show that trophic cascades may be restored via species reintroductions and ecological replacements. It is clear, however, that megafauna effects may be affected by poorly understood trophic complexity effects and interactions with landscape settings, human activities, and other factors. Unfortunately, empirical research on trophic rewilding is still rare, fragmented, and geographically biased, with the literature dominated by essays and opinion pieces. We highlight the need for applied programs to include hypothesis testing and science-based monitoring, and outline priorities for future research, notably assessing the role of trophic complexity, interplay with landscape settings, land use, and climate change, as well as developing the global scope for rewilding and tools to optimize benefits and reduce human-wildlife conflicts. Finally, we recommend developing a decision framework for species selection, building on functional and phylogenetic information and with attention to the potential contribution from synthetic biology.

Science for a wilder Anthropocene: Synthesis and future directions for trophic rewilding research

PubMed Central

Svenning, Jens-Christian; Pedersen, Pil B. M.; Donlan, C. Josh; Ejrnæs, Rasmus; Faurby, Søren; Galetti, Mauro; Hansen, Dennis M.; Sandel, Brody; Sandom, Christopher J.; Terborgh, John W.; Vera, Frans W. M.

2016-01-01

Trophic rewilding is an ecological restoration strategy that uses species introductions to restore top-down trophic interactions and associated trophic cascades to promote self-regulating biodiverse ecosystems. Given the importance of large animals in trophic cascades and their widespread losses and resulting trophic downgrading, it often focuses on restoring functional megafaunas. Trophic rewilding is increasingly being implemented for conservation, but remains controversial. Here, we provide a synthesis of its current scientific basis, highlighting trophic cascades as the key conceptual framework, discussing the main lessons learned from ongoing rewilding projects, systematically reviewing the current literature, and highlighting unintentional rewilding and spontaneous wildlife comebacks as underused sources of information. Together, these lines of evidence show that trophic cascades may be restored via species reintroductions and ecological replacements. It is clear, however, that megafauna effects may be affected by poorly understood trophic complexity effects and interactions with landscape settings, human activities, and other factors. Unfortunately, empirical research on trophic rewilding is still rare, fragmented, and geographically biased, with the literature dominated by essays and opinion pieces. We highlight the need for applied programs to include hypothesis testing and science-based monitoring, and outline priorities for future research, notably assessing the role of trophic complexity, interplay with landscape settings, land use, and climate change, as well as developing the global scope for rewilding and tools to optimize benefits and reduce human–wildlife conflicts. Finally, we recommend developing a decision framework for species selection, building on functional and phylogenetic information and with attention to the potential contribution from synthetic biology. PMID:26504218

Mapping of trophic states based on nutrients concentration and phytoplankton abundance in Jatibarang Reservoir

NASA Astrophysics Data System (ADS)

Rudiyanti, Siti; Anggoro, Sutrisno; Rahman, Arif

2018-02-01

Jatibarang Reservoir is one of the Indonesian Reservoirs, which used for human activities such as tourism and agriculture. These activities will provide input of organic matter and nutrients into the water. These materials will impact water quality and eutrophication process. Eutrophication is the water enrichment by nutrients, especially nitrogen and phosphorus which can promote the growth of phytoplankton. Some indicators of eutrophication are increasing nutrients, trophic states, and change of phytoplankton composition. The relationship between water quality and phytoplankton community can be used as an indicator of trophic states in Jatibarang Reservoir. The aim of this study was to analyze the effect of nutrients concentration and phytoplankton abundance to the trophic states and mapping trophic states based on nutrients concentration and phytoplankton in Jatibarang Reservoir. This study was conducted in June and July 2017 at 9 stations around Jatibarang Reservoir. The results showed that average concentration of nitrate, phosphate, and chlorophyll-a in Jatibarang Reservoir was 0.69 mg/L, 0.27 mg/L, and 1.66 mg/m3, respectively. The phytoplankton abundance ranged 16-62,200 cells/L, consists of 21 genera of four classes, i.e. Chlorophyceae, Cyanophyceae, Bacillariophyceae, and Dinophyceae. Cyanophyceae was a dominant phytoplankton group based on the composition of abundance (>80%). High nutrient concentrations and phytoplankton dominated by Anabaena (Cyanophyceae) which indicated that the waters in Jatibarang Reservoir were eutrophic.

The trophic role of a forest salamander: impacts on invertebrates, leaf litter retention, and the humification process

Treesearch

M. L. Best; H. H. Welsh

2014-01-01

Woodland (Plethodontid) salamanders are the most abundant vertebrates in North American forests, functioning as predators on invertebrates and prey for higher trophic levels. We investigated the role of Ensatina (Ensatina eschscholtzii) in regulating invertebrate numbers and leaf litter retention in a northern California forest. Our objective was...

The hormone prolactin is a novel, endogenous trophic factor able to regulate reactive glia and to limit retinal degeneration.

PubMed

Arnold, Edith; Thebault, Stéphanie; Baeza-Cruz, German; Arredondo Zamarripa, David; Adán, Norma; Quintanar-Stéphano, Andrés; Condés-Lara, Miguel; Rojas-Piloni, Gerardo; Binart, Nadine; Martínez de la Escalera, Gonzalo; Clapp, Carmen

2014-01-29

Retinal degeneration is characterized by the progressive destruction of retinal cells, causing the deterioration and eventual loss of vision. We explored whether the hormone prolactin provides trophic support to retinal cells, thus protecting the retina from degenerative pressure. Inducing hyperprolactinemia limited photoreceptor apoptosis, gliosis, and changes in neurotrophin expression, and it preserved the photoresponse in the phototoxicity model of retinal degeneration, in which continuous exposure of rats to bright light leads to retinal cell death and retinal dysfunction. In this model, the expression levels of prolactin receptors in the retina were upregulated. Moreover, retinas from prolactin receptor-deficient mice exhibited photoresponsive dysfunction and gliosis that correlated with decreased levels of retinal bFGF, GDNF, and BDNF. Collectively, these data unveiled prolactin as a retinal trophic factor that may regulate glial-neuronal cell interactions and is a potential therapeutic molecule against retinal degeneration.

Bottom-up processes influence the demography and life-cycle phenology of Hawaiian bird communities

Treesearch

Jared D. Wolfe; C. John Ralph; Andrew Wiegardt

2017-01-01

Changes in climate can indirectly regulate populations at higher trophic levels by influencing the availability of food resources in the lower reaches of the food web. As such, species that rely on fruit and nectar food resources may be particularly sensitive to these bottom-up perturbations due to the strength of their trophic linkages with climatically-...

Incorporating anthropogenic effects into trophic ecology: predator-prey interactions in a human-dominated landscape.

PubMed

Dorresteijn, Ine; Schultner, Jannik; Nimmo, Dale G; Fischer, Joern; Hanspach, Jan; Kuemmerle, Tobias; Kehoe, Laura; Ritchie, Euan G

2015-09-07

Apex predators perform important functions that regulate ecosystems worldwide. However, little is known about how ecosystem regulation by predators is influenced by human activities. In particular, how important are top-down effects of predators relative to direct and indirect human-mediated bottom-up and top-down processes? Combining data on species' occurrence from camera traps and hunting records, we aimed to quantify the relative effects of top-down and bottom-up processes in shaping predator and prey distributions in a human-dominated landscape in Transylvania, Romania. By global standards this system is diverse, including apex predators (brown bear and wolf), mesopredators (red fox) and large herbivores (roe and red deer). Humans and free-ranging dogs represent additional predators in the system. Using structural equation modelling, we found that apex predators suppress lower trophic levels, especially herbivores. However, direct and indirect top-down effects of humans affected the ecosystem more strongly, influencing species at all trophic levels. Our study highlights the need to explicitly embed humans and their influences within trophic cascade theory. This will greatly expand our understanding of species interactions in human-modified landscapes, which compose the majority of the Earth's terrestrial surface. © 2015 The Author(s).

Incorporating anthropogenic effects into trophic ecology: predator–prey interactions in a human-dominated landscape

PubMed Central

Dorresteijn, Ine; Schultner, Jannik; Nimmo, Dale G.; Fischer, Joern; Hanspach, Jan; Kuemmerle, Tobias; Kehoe, Laura; Ritchie, Euan G.

2015-01-01

Apex predators perform important functions that regulate ecosystems worldwide. However, little is known about how ecosystem regulation by predators is influenced by human activities. In particular, how important are top-down effects of predators relative to direct and indirect human-mediated bottom-up and top-down processes? Combining data on species' occurrence from camera traps and hunting records, we aimed to quantify the relative effects of top-down and bottom-up processes in shaping predator and prey distributions in a human-dominated landscape in Transylvania, Romania. By global standards this system is diverse, including apex predators (brown bear and wolf), mesopredators (red fox) and large herbivores (roe and red deer). Humans and free-ranging dogs represent additional predators in the system. Using structural equation modelling, we found that apex predators suppress lower trophic levels, especially herbivores. However, direct and indirect top-down effects of humans affected the ecosystem more strongly, influencing species at all trophic levels. Our study highlights the need to explicitly embed humans and their influences within trophic cascade theory. This will greatly expand our understanding of species interactions in human-modified landscapes, which compose the majority of the Earth's terrestrial surface. PMID:26336169

State and regional water-quality characteristics and trophic conditions of Michigan's inland lakes, 2001-2005

USGS Publications Warehouse

Fuller, L.M.; Minnerick, R.J.

2008-01-01

The U.S. Geological Survey and the Michigan Department of Environmental Quality are jointly monitoring selected water-quality constituents of inland lakes through 2015 as part of Michigan’s Lake Water Quality Assessment program. During 2001–2005, 433 lake basins from 364 inland lakes were monitored for baseline water-quality conditions and trophic status. This report summarizes the water-quality characteristics and trophic conditions of those monitored lake basins throughout the State. Regional variation of water quality in lake basins was examined by grouping on the basis of the five Omernik level III ecoregions within Michigan. Concentrations of most constituents measured were significantly different between ecoregions. Less regional variation of phosphorus concentrations was noted between Northern Lakes and Forests (50) and North Central Hardwoods (51) ecoregions during summer possibly because water samples were collected when lake productivity was high; hence the utilization of the limited amount of phosphorus by algae and macrophytes may have resulted in the more uniform concentrations between these two ecoregions. Concentrations of common ions (calcium, magnesium, potassium, sodium, chloride, and sulfate) measured in the spring typically were higher in the Michigan southern Lower Peninsula in the Eastern Corn Belt Plains (55), Southern Michigan/Northern Indiana Drift Plains (56), and Huron/Erie Lake Plains (57) ecoregions. Most ions whose concentrations were less than the minimum reporting levels or were nondetectable were from lakes in the Michigan northern Lower Peninsula and the Upper Peninsula in the Northern Lakes and Forests (50) and North Central Hardwoods (51) ecoregions. Chlorophyll a concentrations followed a similar distribution pattern. Measured properties such as pH and specific conductance (indicative of dissolved solids) also showed a regional relation. The lakes with the lowest pH and specific conductance were generally in the western Upper Peninsula (Northern Lakes and Forests (50) ecoregion). The Michigan Department of Environmental Quality classifies Michigan lakes on the basis of their primary biological productivity or trophic characteristics using the Carlson Trophic State Index. Trophic evaluations based on data collected from 2001 through 2005 indicate 17 percent of the lakes are oligotrophic, 53 percent are mesotrophic, 22 percent are eutrophic, 4 percent are hypereutrophic, and less than 5 percent are classified into transition classes between each major class. Although the distribution of lakes throughout Michigan or between Omernik level III ecoregions is not uniform, about 85 percent of the lakes classified as oligotrophic are in the Northern Lakes and Forests (50) or North Central Hardwoods (51) ecoregions. Nearly 28 percent of all the lakes in each of these two ecoregions were classified as oligotrophic. Historical trophic-state classes were compared to the current (2001 through 2005) trophic-state classes. Approximately 72 percent of lakes remained in the same trophic-state class, 11 percent moved up a partial or full class (indicating a decrease in water clarity) and 18 percent moved down a partial or full class (indicating an increase in water clarity).

Nerve-dependent factors regulating transcript levels of glycogen phosphorylase in skeletal muscle.

PubMed

Matthews, C C; Carlsen, R C; Froman, B; Tait, R; Gorin, F

1998-06-01

1. Muscle glycogen phosphorylase (MGP), the rate-limiting enzyme for glycogen metabolism in skeletal muscle, is neurally regulated. Steady-state transcript levels of the skeletal muscle isozyme of MGP decrease significantly following muscle denervation and after prolonged muscle inactivity with an intact motor nerve. These data suggest that muscle activity has an important influence on MGP gene expression. The evidence to this point, however, does not preclude the possibility that MGP is also regulated by motor neuron-derived trophic factors. This study attempts to distinguish between regulation provided by nerve-evoked muscle contractile activity and that provided by the delivery of neurotrophic factors. 2. Steady-state MGP transcript levels were determined in rat tibialis anterior (TA) muscles following controlled interventions aimed at separating the contributions of contractile activity from axonally transported trophic factors. The innervated TA was rendered inactive by daily epineural injections of tetrodotoxin (TTX) into the sciatic nerve. Sustained inhibition of axonal transport was accomplished by applying one of three different concentrations of the antimicrotubule agent, vinblastine (VIN), to the proximal sciatic nerve for 1 hr. The axonal transport of acetylcholinesterase (AChE) was assessed 7, 14, and 28 days after the single application of VIN. 3. MGP transcript levels normalized to total RNA were reduced by 67% in rat TA, 7 days after nerve section. Daily injection of 2 microg TTX into the sciatic nerve for 7 days eliminated muscle contractile activity and reduced MGP transcript levels by 60%. 4. A single, 1-hr application of 0.10% (w/v) VIN to the sciatic nerve reduced axonal transport but did not alter MGP transcript levels in the associated TA, 7 days after treatment. Application of 0.10% VIN to the sciatic nerve also did not affect IA sensory or motor nerve conduction velocities or TA contractile function. 5. Treatment of the sciatic nerve with 0.40% (w/v) VIN for 1 hr reduced axonal transport and decreased MGP transcript levels by 50% within 7 days, but also reduced sensory and motor nerve conduction velocities and depressed TA contractile function. 6. Myogenin, a member of a family of regulatory factors shown to influence the transcription of many muscle genes, including MGP, was used as a molecular marker for muscle inactivity. Myogenin transcript levels were increased following denervation and after treatment with TTX or 0.40% VIN but not after treatment with 0.10% VIN. 7. The results suggest that MGP transcript levels in TA are regulated predominantly by muscle activity, rather than by the delivery of neurotrophic factors. Intrinsic myogenic factors, however, also play a role in MGP expression, since denervation did not reduce MGP transcript levels below 30% of control TA. The dominant influence of activity in the regulation of MGP contrasts with the proposed regulation of oxidative enzyme expression, which appears to depend on both activity and trophic factor influences.

Convergent, Parallel and Correlated Evolution of Trophic Morphologies in the Subfamily Schizothoracinae from the Qinghai-Tibetan Plateau

PubMed Central

Qi, Delin; Chao, Yan; Guo, Songchang; Zhao, Lanying; Li, Taiping; Wei, Fulei; Zhao, Xinquan

2012-01-01

Schizothoracine fishes distributed in the water system of the Qinghai-Tibetan plateau (QTP) and adjacent areas are characterized by being highly adaptive to the cold and hypoxic environment of the plateau, as well as by a high degree of diversity in trophic morphology due to resource polymorphisms. Although convergent and parallel evolution are prevalent in the organisms of the QTP, it remains unknown whether similar evolutionary patterns have occurred in the schizothoracine fishes. Here, we constructed for the first time a tentative molecular phylogeny of the schizothoracine fishes based on the complete sequences of the cytochrome b gene. We employed this molecular phylogenetic framework to examine the evolution of trophic morphologies. We used Pagel's maximum likelihood method to estimate the evolutionary associations of trophic morphologies and food resource use. Our results showed that the molecular and published morphological phylogenies of Schizothoracinae are partially incongruent with respect to some intergeneric relationships. The phylogenetic results revealed that four character states of five trophic morphologies and of food resource use evolved at least twice during the diversification of the subfamily. State transitions are the result of evolutionary patterns including either convergence or parallelism or both. Furthermore, our analyses indicate that some characters of trophic morphologies in the Schizothoracinae have undergone correlated evolution, which are somewhat correlated with different food resource uses. Collectively, our results reveal new examples of convergent and parallel evolution in the organisms of the QTP. The adaptation to different trophic niches through the modification of trophic morphologies and feeding behaviour as found in the schizothoracine fishes may account for the formation and maintenance of the high degree of diversity and radiations in fish communities endemic to QTP. PMID:22470515

Categorization of the trophic status of a hydroelectric power plant reservoir in the Brazilian Amazon by statistical analyses and fuzzy approaches.

PubMed

da Costa Lobato, Tarcísio; Hauser-Davis, Rachel Ann; de Oliveira, Terezinha Ferreira; Maciel, Marinalva Cardoso; Tavares, Maria Regina Madruga; da Silveira, Antônio Morais; Saraiva, Augusto Cesar Fonseca

2015-02-15

The Amazon area has been increasingly suffering from anthropogenic impacts, especially due to the construction of hydroelectric power plant reservoirs. The analysis and categorization of the trophic status of these reservoirs are of interest to indicate man-made changes in the environment. In this context, the present study aimed to categorize the trophic status of a hydroelectric power plant reservoir located in the Brazilian Amazon by constructing a novel Water Quality Index (WQI) and Trophic State Index (TSI) for the reservoir using major ion concentrations and physico-chemical water parameters determined in the area and taking into account the sampling locations and the local hydrological regimes. After applying statistical analyses (factor analysis and cluster analysis) and establishing a rule base of a fuzzy system to these indicators, the results obtained by the proposed method were then compared to the generally applied Carlson and a modified Lamparelli trophic state index (TSI), specific for trophic regions. The categorization of the trophic status by the proposed fuzzy method was shown to be more reliable, since it takes into account the specificities of the study area, while the Carlson and Lamparelli TSI do not, and, thus, tend to over or underestimate the trophic status of these ecosystems. The statistical techniques proposed and applied in the present study, are, therefore, relevant in cases of environmental management and policy decision-making processes, aiding in the identification of the ecological status of water bodies. With this, it is possible to identify which factors should be further investigated and/or adjusted in order to attempt the recovery of degraded water bodies. Copyright © 2014 Elsevier B.V. All rights reserved.

Demographic and Phenotypic Effects of Human Mediated Trophic Subsidy on a Large Australian Lizard (Varanus varius): Meal Ticket or Last Supper?

PubMed Central

Jessop, Tim S.; Smissen, Peter; Scheelings, Franciscus; Dempster, Tim

2012-01-01

Humans are increasingly subsidizing and altering natural food webs via changes to nutrient cycling and productivity. Where human trophic subsidies are concentrated and persistent within natural environments, their consumption could have complex consequences for wild animals through altering habitat preferences, phenotypes and fitness attributes that influence population dynamics. Human trophic subsidies conceptually create both costs and benefits for animals that receive increased calorific and altered nutritional inputs. Here, we evaluated the effects of a common terrestrial human trophic subsidies, human food refuse, on population and phenotypic (comprising morphological and physiological health indices) parameters of a large predatory lizard (∼2 m length), the lace monitor (Varanus varius), in southern Australia by comparison with individuals not receiving human trophic subsidies. At human trophic subsidies sites, lizards were significantly more abundant and their sex ratio highly male biased compared to control sites in natural forest. Human trophic subsidies recipient lizards were significantly longer, heavier and in much greater body condition. Blood parasites were significantly lower in human trophic subsidies lizards. Collectively, our results imply that human trophic subsidized sites were especially attractive to adult male lace monitors and had large phenotypic effects. However, we cannot rule out that the male-biased aggregations of large monitors at human trophic subsidized sites could lead to reductions in reproductive fitness, through mate competition and offspring survival, and through greater exposure of eggs and juveniles to predation. These possibilities could have negative population consequences. Aggregations of these large predators may also have flow on effects to surrounding food web dynamics through elevated predation levels. Given that flux of energy and nutrients into food webs is central to the regulation of populations and their communities, we advocate further studies of human trophic subsidies be undertaken to evaluate the potentially large ecological implications of this significant human environmental alteration. PMID:22509271

Trophic and neurotrophic factors in human pituitary adenomas (Review).

PubMed

Spoletini, Marialuisa; Taurone, Samanta; Tombolini, Mario; Minni, Antonio; Altissimi, Giancarlo; Wierzbicki, Venceslao; Giangaspero, Felice; Parnigotto, Pier Paolo; Artico, Marco; Bardella, Lia; Agostinelli, Enzo; Pastore, Francesco Saverio

2017-10-01

The pituitary gland is an organ that functionally connects the hypothalamus with the peripheral organs. The pituitary gland is an important regulator of body homeostasis during development, stress, and other processes. Pituitary adenomas are a group of tumors arising from the pituitary gland: they may be subdivided in functional or non-functional, depending on their hormonal activity. Some trophic and neurotrophic factors seem to play a key role in the development and maintenance of the pituitary function and in the regulation of hypothalamo-pituitary-adrenocortical axis activity. Several lines of evidence suggest that trophic and neurotrophic factors may be involved in pituitary function, thus suggesting a possible role of the trophic and neurotrophic factors in the normal development of pituitary gland and in the progression of pituitary adenomas. Additional studies might be necessary to better explain the biological role of these molecules in the development and progression of this type of tumor. In this review, in light of the available literature, data on the following neurotrophic factors are discussed: ciliary neurotrophic factor (CNTF), transforming growth factors β (TGF‑β), glial cell line-derived neurotrophic factor (GDNF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), vascular endothelial growth inhibitor (VEGI), fibroblast growth factors (FGFs) and epidermal growth factor (EGF) which influence the proliferation and growth of pituitary adenomas.

Predator-prey trophic relationships in response to organic management practices.

PubMed

Schmidt, Jason M; Barney, Sarah K; Williams, Mark A; Bessin, Ricardo T; Coolong, Timothy W; Harwood, James D

2014-08-01

A broad range of environmental conditions likely regulate predator-prey population dynamics and impact the structure of these communities. Central to understanding the interplay between predator and prey populations and their importance is characterizing the corresponding trophic interactions. Here, we use a well-documented molecular approach to examine the structure of the community of natural enemies preying upon the squash bug, Anasa tristis, a herbivorous cucurbit pest that severely hinders organic squash and pumpkin production in the United States. Primer pairs were designed to examine the effects of organic management practices on the strength of these trophic connections and link this metric to measures of the arthropod predator complex density and diversity within an experimental open-field context. Replicated plots of butternut squash were randomly assigned to three treatments and were sampled throughout a growing season. Row-cover treatments had significant negative effects on squash bug and predator communities. In total, 640 predators were tested for squash bug molecular gut-content, of which 11% were found to have preyed on squash bugs, but predation varied over the season between predator groups (coccinellids, geocorids, nabids, web-building spiders and hunting spiders). Through the linking of molecular gut-content analysis to changes in diversity and abundance, these data delineate the complexity of interaction pathways on a pest that limits the profitability of organic squash production. © 2014 John Wiley & Sons Ltd.

Determination of Trophic State Changes with Diel Dissolved Oxygen: A Case Study in a Shallow Lake.

PubMed

Xu, Zhen; Xu, Y Jun

2015-11-01

Current trophic state indices (TSI) have been reported to have limitations in assessing changes in eutrophication status of shallow waters. This study aimed to use intensive measurements on dissolved oxygen (DO) to improve the determination of tropic state changes. The authors deployed an environment monitoring buoy in a eutrophic shallow lake and recorded water temperature, DO, and chlorophyll-a concentrations at 15-minute intervals for two 1-year periods: from August 2008 to July 2009 and from August 2013 to July 2014. In addition, they recorded water levels over the same periods and collected water samples for nutrient analysis. The authors analyzed the high-time resolution DO records, compared the diel DO trends between the two 1-year periods, and proposed a new TSI using DO. They found that analyzing the change in diel DO ranges can improve commonly used methods for classifying trophic states and assessing the change of eutrophication status of waterbodies.

Combined Influence of Landscape Composition and Nutrient Inputs on Lake Trophic Structure

EPA Science Inventory

The concentration of chlorophyll a is a measure of the biological productivity of a lake and is largely (but not exclusively) determined by available nutrients. As nutrient inputs increase, productivity increases and lakes transition from low trophic state (e.g. oligotrophic) to...

Changes in food web structure under scenarios of overfishing in the southern Benguela: Comparison of the Ecosim and OSMOSE modelling approaches

NASA Astrophysics Data System (ADS)

Travers, M.; Watermeyer, K.; Shannon, L. J.; Shin, Y.-J.

2010-01-01

Ecosystem models provide a platform allowing exploration into the possible responses of marine food webs to fishing pressure and various potential management decisions. In this study we investigate the particular effects of overfishing on the structure and function of the southern Benguela food web, using two models with different underlying assumptions: the spatialized, size-based individual-based model, OSMOSE, and the trophic mass-balance model, Ecopath with Ecosim (EwE). Starting from the same reference state of the southern Benguela upwelling ecosystem during the 1990s, we compare the response of the food web to scenarios of overfishing using these two modelling approaches. A scenario of increased fishing mortality is applied to two distinct functional groups: i) two species of Cape hake, representing important target predatory fish, and ii) the forage species anchovy, sardine and redeye. In these simulations, fishing mortality on the selected functional groups is doubled for 10 years, followed by 10 years at the initial fishing mortality. We compare the food web states before the increase of fishing mortality, after 10 years of overfishing and after a further 10 years during which fishing was returned to initial levels. In order to compare the simulated food web structures with the reference state, and between the two modelling approaches, we use a set of trophic indicators: the mean trophic level of the community and in catches, the trophic pyramid (biomass per discrete trophic level), and the predatory/forage fish biomass ratio. OSMOSE and EwE present globally similar results for the trophic functioning of the ecosystem under fishing pressure: the biomass of targeted species decreases whereas that of their potential competitors increases. The reaction of distant species is more diverse, depending on the feeding links between the compartments. The mean trophic level of the community does not vary enough to be used for assessing ecosystem impacts of fishing, and the mean trophic level in the catch displays a surprising increase due to the short period of overfishing. The trophic pyramids behave in an unexpected way compared to trophic control theory, because at least two food chains with different dynamics are intertwined within the food web. We emphasize the importance of biomass information at the species level for interpreting dynamics in aggregated indicators, and we highlight the importance of competitive groups when looking at ecosystem functioning under fishing disturbance. Finally, we discuss the results within the scope of differences between models, in terms of the way they are formulated, spatial dimensions, predation formulations and the representation of fish life cycles.

Trophic cascades in rocky shore tide pools: distinguishing lethal and nonlethal effects.

PubMed

Trussell, Geoffrey C; Ewanchuk, Patrick J; Bertness, Mark D; Silliman, Brian R

2004-05-01

The effects of predators on the density of their prey can have positive indirect effects on the abundance of the prey's resource via a trophic cascade. This concept has strongly influenced contemporary views of how communities are structured. However, predators also can transmit indirect effects by inducing changes in prey traits. We show that the mere presence of predator risk cues can initiate a trophic cascade in rocky shore tide pools. In large (mean surface area =9 m2), natural tide pools, we manipulated crab density and their foraging ability to examine the relative importance of lethal (density-mediated) and non-lethal (trait-mediated) predator effects to algal community development. We found that perceived predation risk reduced snail density as much as the direct predation treatment, showing that green crab predation was not an important factor regulating local snail density. Instead, snail emigration away from resident crabs appears to be the most important factor regulating local snail density. As a result, the abundance of ephemeral green algae was similar in the predation risk and direct predation treatments, suggesting that the consumption of snails by crabs plays a minimal role in mediating the trophic cascade. Increased attention to trait-mediated effects that are transmitted by predator-induced changes in prey behavior may change our view of how predators exert their strong influence on community structure.

Mesenchymal stem cell therapy ameliorates diabetic nephropathy via the paracrine effect of renal trophic factors including exosomes

PubMed Central

Nagaishi, Kanna; Mizue, Yuka; Chikenji, Takako; Otani, Miho; Nakano, Masako; Konari, Naoto; Fujimiya, Mineko

2016-01-01

Bone marrow-derived mesenchymal stem cells (MSCs) have contributed to the improvement of diabetic nephropathy (DN); however, the actual mediator of this effect and its role has not been characterized thoroughly. We investigated the effects of MSC therapy on DN, focusing on the paracrine effect of renal trophic factors, including exosomes secreted by MSCs. MSCs and MSC-conditioned medium (MSC-CM) as renal trophic factors were administered in parallel to high-fat diet (HFD)-induced type 2 diabetic mice and streptozotocin (STZ)-induced insulin-deficient diabetic mice. Both therapies showed approximately equivalent curative effects, as each inhibited the exacerbation of albuminuria. They also suppressed the excessive infiltration of BMDCs into the kidney by regulating the expression of the adhesion molecule ICAM-1. Proinflammatory cytokine expression (e.g., TNF-α) and fibrosis in tubular interstitium were inhibited. TGF-β1 expression was down-regulated and tight junction protein expression (e.g., ZO-1) was maintained, which sequentially suppressed the epithelial-to-mesenchymal transition of tubular epithelial cells (TECs). Exosomes purified from MSC-CM exerted an anti-apoptotic effect and protected tight junction structure in TECs. The increase of glomerular mesangium substrate was inhibited in HFD-diabetic mice. MSC therapy is a promising tool to prevent DN via the paracrine effect of renal trophic factors including exosomes due to its multifactorial action. PMID:27721418

Regulation of Microglia by Ionotropic Glutamatergic and GABAergic Neurotransmission

PubMed Central

Wong, Wai T.; Wang, Minhua; Li, Wei

2015-01-01

Recent studies have indicated that constitutive functions of microglia in the healthy adult CNS involve immune surveillance, synapse maintenance, and trophic support. These functions have been related to the ramified structure of “resting” microglia and the prominent motility in their processes that provide extensive coverage of the entire extracellular milleu. In this review, we examine how external signals, and in particular, ionotropic neurotransmission, regulate features of microglial morphology and process motility. Taken together, current findings indicate that microglial physiology in the healthy CNS is constitutively and reciprocally regulated by endogenous ionotropic glutamatergic and GABAergic neurotransmission. These influences do not act directly on microglial cells but indirectly via the activity-dependent release of ATP, likely through a mechanism involving pannexin channels. Microglia in the “resting” state are not only dynamically active, but are constantly engaged in ongoing communication with neuronal and macroglial components of the CNS in a functionally relevant way. PMID:22166726

Pulsed flows, tributary inputs, and food web structure in a highly regulated river

USGS Publications Warehouse

Sabo, John; Caron, Melanie; Doucett, Richard R.; Dibble, Kimberly L.; Ruhi, Albert; Marks, Jane; Hungate, Bruce; Kennedy, Theodore A.

2018-01-01

1.Dams disrupt the river continuum, altering hydrology, biodiversity, and energy flow. Although research indicates that tributary inputs have the potential to dilute these effects, knowledge at the food web level is still scarce.2.Here we examined the riverine food web structure of the Colorado River below Glen Canyon Dam, focusing on organic matter sources, trophic diversity, and food chain length. We asked how these components respond to pulsed flows from tributaries following monsoon thunderstorms that seasonally increase streamflow in the American Southwest.3.Tributaries increased the relative importance of terrestrial organic matter, particularly during the wet season below junctures of key tributaries. This contrasted with the algal-based food web present immediately below Glen Canyon Dam.4.Tributary inputs during the monsoon also increased trophic diversity and food chain length: food chain length peaked below the confluence with the largest tributary (by discharge) in Grand Canyon, increasing by >1 trophic level over a 4-5 kilometre reach possibly due to aquatic prey being flushed into the mainstem during heavy rain events.5.Our results illustrate that large tributaries can create seasonal discontinuities, influencing riverine food web structure in terms of allochthony, food web diversity, and food chain length.6.Synthesis and applications. Pulsed flows from unregulated tributaries following seasonal monsoon rains increase the importance of terrestrially-derived organic matter in large, regulated river food webs, increasing food chain length and trophic diversity downstream of tributary inputs. Protecting unregulated tributaries within hydropower cascades may be important if we are to mitigate food web structure alteration due to flow regulation by large dams. This is critical in the light of global hydropower development, especially in megadiverse, developing countries where dam placement (including completed and planned structures) is in tributaries.

Ecosystem context and historical contingency in apex predator recoveries.

PubMed

Stier, Adrian C; Samhouri, Jameal F; Novak, Mark; Marshall, Kristin N; Ward, Eric J; Holt, Robert D; Levin, Phillip S

2016-05-01

Habitat loss, overexploitation, and numerous other stressors have caused global declines in apex predators. This "trophic downgrading" has generated widespread concern because of the fundamental role that apex predators can play in ecosystem functioning, disease regulation, and biodiversity maintenance. In attempts to combat declines, managers have conducted reintroductions, imposed stricter harvest regulations, and implemented protected areas. We suggest that full recovery of viable apex predator populations is currently the exception rather than the rule. We argue that, in addition to well-known considerations, such as continued exploitation and slow life histories, there are several underappreciated factors that complicate predator recoveries. These factors include three challenges. First, a priori identification of the suite of trophic interactions, such as resource limitation and competition that will influence recovery can be difficult. Second, defining and accomplishing predator recovery in the context of a dynamic ecosystem requires an appreciation of the timing of recovery, which can determine the relative density of apex predators and other predators and therefore affect competitive outcomes. Third, successful recovery programs require designing adaptive sequences of management strategies that embrace key environmental and species interactions as they emerge. Consideration of recent research on food web modules, alternative stable states, and community assembly offer important insights for predator recovery efforts and restoration ecology more generally. Foremost among these is the importance of a social-ecological perspective in facilitating a long-lasting predator restoration while avoiding unintended consequences.

Ecosystem context and historical contingency in apex predator recoveries

PubMed Central

Stier, Adrian C.; Samhouri, Jameal F.; Novak, Mark; Marshall, Kristin N.; Ward, Eric J.; Holt, Robert D.; Levin, Phillip S.

2016-01-01

Habitat loss, overexploitation, and numerous other stressors have caused global declines in apex predators. This “trophic downgrading” has generated widespread concern because of the fundamental role that apex predators can play in ecosystem functioning, disease regulation, and biodiversity maintenance. In attempts to combat declines, managers have conducted reintroductions, imposed stricter harvest regulations, and implemented protected areas. We suggest that full recovery of viable apex predator populations is currently the exception rather than the rule. We argue that, in addition to well-known considerations, such as continued exploitation and slow life histories, there are several underappreciated factors that complicate predator recoveries. These factors include three challenges. First, a priori identification of the suite of trophic interactions, such as resource limitation and competition that will influence recovery can be difficult. Second, defining and accomplishing predator recovery in the context of a dynamic ecosystem requires an appreciation of the timing of recovery, which can determine the relative density of apex predators and other predators and therefore affect competitive outcomes. Third, successful recovery programs require designing adaptive sequences of management strategies that embrace key environmental and species interactions as they emerge. Consideration of recent research on food web modules, alternative stable states, and community assembly offer important insights for predator recovery efforts and restoration ecology more generally. Foremost among these is the importance of a social-ecological perspective in facilitating a long-lasting predator restoration while avoiding unintended consequences. PMID:27386535

Assessment of the trophic status of four coastal lagoons and one estuarine delta, eastern Brazil.

PubMed

Cotovicz Junior, Luiz Carlos; Brandini, Nilva; Knoppers, Bastiaan Adriaan; Mizerkowski, Byanka Damian; Sterza, José Mauro; Ovalle, Alvaro Ramon Coelho; Medeiros, Paulo Ricardo Petter

2013-04-01

Anthropogenic eutrophication of aquatic ecosystems continues to be one of the major environmental issues worldwide and also of Brazil. Over the last five decades, several approaches have been proposed to discern the trophic state and the natural and cultural processes involved in eutrophication, including the multi-parameter Assessment of Estuarine Trophic Status (ASSETS) index model. This study applies ASSETS to four Brazilian lagoons (Mundaú, Manguaba, Guarapina, and Piratininga) and one estuarine delta (Paraíba do Sul River), set along the eastern Brazilian coast. The model combines three indices based on the pressure-state-response (PSR) approach to rank the trophic status and forecast the potential eutrophication of a system, to which a final ASSETS grade is established. The lagoons were classified as being eutrophic and highly susceptible to eutrophication, due primarily to their longer residence times but also their high nutrient input index. ASSETS classified the estuary of the Paraíba do Sul river with a low to moderate trophic state (e.g., largely mesotrophic) and low susceptibility to eutrophication. Its nutrient input index was high, but the natural high dilution and flushing potential driven by river flow mitigated the susceptibility to eutrophication. Eutrophication forecasting provided more favorable trends for the Mundaú and Manguaba lagoons and the Paraíba do Sul estuary, in view of the larger investments in wastewater treatment and remediation plans. The final ASSETS ranking system established the lagoons of Mundaú as "moderate," Manguaba as "bad," Guarapina as "poor," and Piratininga as "bad," whereas the Paraíba do Sul River Estuary was "good."

Biomass changes and trophic amplification of plankton in a warmer ocean.

PubMed

Chust, Guillem; Allen, J Icarus; Bopp, Laurent; Schrum, Corinna; Holt, Jason; Tsiaras, Kostas; Zavatarelli, Marco; Chifflet, Marina; Cannaby, Heather; Dadou, Isabelle; Daewel, Ute; Wakelin, Sarah L; Machu, Eric; Pushpadas, Dhanya; Butenschon, Momme; Artioli, Yuri; Petihakis, George; Smith, Chris; Garçon, Veronique; Goubanova, Katerina; Le Vu, Briac; Fach, Bettina A; Salihoglu, Baris; Clementi, Emanuela; Irigoien, Xabier

2014-07-01

Ocean warming can modify the ecophysiology and distribution of marine organisms, and relationships between species, with nonlinear interactions between ecosystem components potentially resulting in trophic amplification. Trophic amplification (or attenuation) describe the propagation of a hydroclimatic signal up the food web, causing magnification (or depression) of biomass values along one or more trophic pathways. We have employed 3-D coupled physical-biogeochemical models to explore ecosystem responses to climate change with a focus on trophic amplification. The response of phytoplankton and zooplankton to global climate-change projections, carried out with the IPSL Earth System Model by the end of the century, is analysed at global and regional basis, including European seas (NE Atlantic, Barents Sea, Baltic Sea, Black Sea, Bay of Biscay, Adriatic Sea, Aegean Sea) and the Eastern Boundary Upwelling System (Benguela). Results indicate that globally and in Atlantic Margin and North Sea, increased ocean stratification causes primary production and zooplankton biomass to decrease in response to a warming climate, whilst in the Barents, Baltic and Black Seas, primary production and zooplankton biomass increase. Projected warming characterized by an increase in sea surface temperature of 2.29 ± 0.05 °C leads to a reduction in zooplankton and phytoplankton biomasses of 11% and 6%, respectively. This suggests negative amplification of climate driven modifications of trophic level biomass through bottom-up control, leading to a reduced capacity of oceans to regulate climate through the biological carbon pump. Simulations suggest negative amplification is the dominant response across 47% of the ocean surface and prevails in the tropical oceans; whilst positive trophic amplification prevails in the Arctic and Antarctic oceans. Trophic attenuation is projected in temperate seas. Uncertainties in ocean plankton projections, associated to the use of single global and regional models, imply the need for caution when extending these considerations into higher trophic levels. © 2014 John Wiley & Sons Ltd.

Estimation of Chlorophyll-a Concentration and the Trophic State of the Barra Bonita Hydroelectric Reservoir Using OLI/Landsat-8 Images

PubMed Central

Watanabe, Fernanda Sayuri Yoshino; Alcântara, Enner; Rodrigues, Thanan Walesza Pequeno; Imai, Nilton Nobuhiro; Barbosa, Cláudio Clemente Faria; Rotta, Luiz Henrique da Silva

2015-01-01

Reservoirs are artificial environments built by humans, and the impacts of these environments are not completely known. Retention time and high nutrient availability in the water increases the eutrophic level. Eutrophication is directly correlated to primary productivity by phytoplankton. These organisms have an important role in the environment. However, high concentrations of determined species can lead to public health problems. Species of cyanobacteria produce toxins that in determined concentrations can cause serious diseases in the liver and nervous system, which could lead to death. Phytoplankton has photoactive pigments that can be used to identify these toxins. Thus, remote sensing data is a viable alternative for mapping these pigments, and consequently, the trophic. Chlorophyll-a (Chl-a) is present in all phytoplankton species. Therefore, the aim of this work was to evaluate the performance of images of the sensor Operational Land Imager (OLI) onboard the Landsat-8 satellite in determining Chl-a concentrations and estimating the trophic level in a tropical reservoir. Empirical models were fitted using data from two field surveys conducted in May and October 2014 (Austral Autumn and Austral Spring, respectively). Models were applied in a temporal series of OLI images from May 2013 to October 2014. The estimated Chl-a concentration was used to classify the trophic level from a trophic state index that adopted the concentration of this pigment-like parameter. The models of Chl-a concentration showed reasonable results, but their performance was likely impaired by the atmospheric correction. Consequently, the trophic level classification also did not obtain better results. PMID:26322489

Effects of Sewage Discharge on Trophic State and Water Quality in a Coastal Ecosystem of the Gulf of California

PubMed Central

Vargas-González, Héctor Hugo; Arreola-Lizárraga, José Alfredo; Mendoza-Salgado, Renato Arturo; Méndez-Rodríguez, Lía Celina; Lechuga-Deveze, Carlos Hernando; Padilla-Arredondo, Gustavo; Cordoba-Matson, Miguel

2014-01-01

This paper provides evidence of the effects of urban wastewater discharges on the trophic state and environmental quality of a coastal water body in a semiarid subtropical region in the Gulf of California. The concentrations of dissolved inorganic nutrients and organic matter from urban wastewater primary treatment were estimated. La Salada Cove was the receiving water body and parameters measured during an annual cycle were temperature, salinity, dissolved oxygen, nitrite, nitrate, ammonia, orthophosphate, and chlorophyll a. The effects of sewage inputs were determined by using Trophic State Index (TRIX) and the Arid Zone Coastal Water Quality Index (AZCI). It was observed that urban wastewater of the city of Guaymas provided 1,237 ton N yr−1 and 811 ton P yr−1 and TRIX indicated that the receiving water body showed symptoms of eutrophication from an oligotrophic state to a mesotrophic state; AZCI also indicated that the environmental quality of the water body was poor. The effects of urban wastewater supply with insufficient treatment resulted in symptoms of eutrophication and loss of ecological functions and services of the coastal ecosystem in La Salada Cove. PMID:24711731

Trophic state in Voyageurs National Park lakes before and after implementation of a revised water-level management plan

USGS Publications Warehouse

Christensen, Victoria G.; Maki, Ryan P.

2015-01-01

We compiled Secchi depth, total phosphorus, and chlorophyll a (Chla) data from Voyageurs National Park lakes and compared datasets before and after a new water-level management plan was implemented in January 2000. Average Secchi depth transparency improved (from 1.9 to 2.1 m, p = 0.020) between 1977-1999 and 2000-2011 in Kabetogama Lake for August samples only and remained unchanged in Rainy, Namakan, and Sand Point Lakes, and Black Bay in Rainy Lake. Average open-water season Chla concentration decreased in Black Bay (from an average of 13 to 6.0 μg/l, p = 0.001) and Kabetogama Lake (from 9.9 to 6.2 μg/l, p = 0.006) between 1977-1999 and 2000-2011. Trophic state index decreased significantly in Black Bay from 59 to 51 (p = 0.006) and in Kabetogama Lake from 57 to 50 (p = 0.006) between 1977-1999 and 2000-2011. Trophic state indices based on Chla indicated that after 2000, Sand Point, Namakan, and Rainy Lakes remained oligotrophic, whereas eutrophication has decreased in Kabetogama Lake and Black Bay. Although nutrient inputs from inflows and internal sources are still sufficient to produce annual cyanobacterial blooms and may inhibit designated water uses, trophic state has decreased for Kabetogama Lake and Black Bay and there has been no decline in lake ecosystem health since the implementation of the revised water-level management plan.

Missing lynx and trophic cascades in food webs: A reply to Ripple et al.

Treesearch

John R. Squires; Nicholas J. DeCesare; Mark Hebblewhite; Joel Berger

2012-01-01

Ripple et al. (2011) proposed a hypothesis that the recovery of gray wolves (Canis lupus) may positively affect the viability of threatened Canada lynx (Lynx canadensis) populations in the contiguous United States through indirect species interactions. Ripple et al. (2011) proposed 2 key trophic linkages connecting wolf restoration with lynx recovery. First, recovering...

The trophic fingerprint of marine fisheries.

PubMed

Branch, Trevor A; Watson, Reg; Fulton, Elizabeth A; Jennings, Simon; McGilliard, Carey R; Pablico, Grace T; Ricard, Daniel; Tracey, Sean R

2010-11-18

Biodiversity indicators provide a vital window on the state of the planet, guiding policy development and management. The most widely adopted marine indicator is mean trophic level (MTL) from catches, intended to detect shifts from high-trophic-level predators to low-trophic-level invertebrates and plankton-feeders. This indicator underpins reported trends in human impacts, declining when predators collapse ("fishing down marine food webs") and when low-trophic-level fisheries expand ("fishing through marine food webs"). The assumption is that catch MTL measures changes in ecosystem MTL and biodiversity. Here we combine model predictions with global assessments of MTL from catches, trawl surveys and fisheries stock assessments and find that catch MTL does not reliably predict changes in marine ecosystems. Instead, catch MTL trends often diverge from ecosystem MTL trends obtained from surveys and assessments. In contrast to previous findings of rapid declines in catch MTL, we observe recent increases in catch, survey and assessment MTL. However, catches from most trophic levels are rising, which can intensify fishery collapses even when MTL trends are stable or increasing. To detect fishing impacts on marine biodiversity, we recommend greater efforts to measure true abundance trends for marine species, especially those most vulnerable to fishing.

Trophic habits of mesostigmatid mites associated with bark beetles in Mexico

Treesearch

M. Patricia Chaires-Grijalva; Edith G. Estrada-Venegas; Armando Equihua-Martinez; John C. Moser; Stacy R. Blomquist

2016-01-01

Samples of bark and logs damaged by bark beetles were collected from 16 states of Mexico from 2007 to 2012. Fifteen bark beetle species were found within the bark and log samples and were examined for phoretic mites and arthropod associates. Thirty-three species of mesostigmatid mites were discovered within the samples. They were identified in several trophic guilds...

Statewide lake classification utilizing LANDSAT imagery for the state of Wisconsin

NASA Technical Reports Server (NTRS)

Martin, R. H.; Merideth, R. W., Jr.

1981-01-01

A cooperative program between the Wisconsin Department of Natural Resources and the University of Wisconsin-Madison resulted in the assessment of the trophic condition of approximately 3,000 significant inland lakes in Wisconsin. The feasibility of using both photographic and digital representations of LANDSAT multispectral scanner data for lake classification was investigated. The result was the development of a nearly automated system which, with minimal human interaction, locates and extracts the lake data, then corrects the data for atmospheric effects, and finally classifies all the significant lakes in the state as to trophic condition.

The TNF receptor and Ig superfamily members form an integrated signaling circuit controlling dendritic cell homeostasis

PubMed Central

De Trez, Carl; Ware, Carl F.

2008-01-01

Dendritic cells (DC) constitute the most potent antigen presenting cells of the immune system, playing a key role bridging innate and adaptive immune responses. Specialized DC subsets differ depending on their origin, tissue location and the influence of trophic factors, the latter remain to be fully understood. Stromal cell and myeloid-associated Lymphotoxin-β receptor (LTβR) signaling is required for the local proliferation of lymphoid tissue DC. This review focuses the LTβR signaling cascade as a crucial positive trophic signal in the homeostasis of DC subsets. The noncanonical coreceptor pathway comprised of the Immunoglobulin (Ig) superfamily member, B and T lymphocyte attenuator (BTLA) and TNFR superfamily member, Herpesvirus entry mediator (HVEM) counter regulates the trophic signaling by LTβR. Together both pathways form an integrated signaling circuit achieving homeostasis of DC subsets. PMID:18511331

Contributions of 5-HT neurons to respiratory control: neuromodulatory and trophic effects.

PubMed

Hodges, Matthew R; Richerson, George B

2008-12-10

Serotonin (5-hydroxytryptamine; 5-HT) is a neurotransmitter produced by a small number of neurons in the midbrain, pons and medulla. These neurons project widely throughout the neuraxis, where they release 5-HT and co-localized neuropeptides such as substance P (SP) and thyrotropin-releasing hormone (TRH). Each of these chemicals produce effects largely through G protein-coupled receptors, second messenger systems and subsequent neuromodulatory effects on target neurons. Emerging evidence suggests that 5-HT has additional modes of action during development and in adult mammals, including trophic effects (neurogenesis, cell differentiation, proliferation, migration and maturation) and influences on synaptic plasticity. Here, we discuss some of the neuromodulatory and trophic roles of 5-HT in general and in the context of respiratory control, as well as the regulation of release of modulatory neurotransmitters from 5-HT neurons. Future directions of study are also discussed.

Ecological-network models link diversity, structure and function in the plankton food-web

NASA Astrophysics Data System (ADS)

D'Alelio, Domenico; Libralato, Simone; Wyatt, Timothy; Ribera D'Alcalà, Maurizio

2016-02-01

A planktonic food-web model including sixty-three functional nodes (representing auto- mixo- and heterotrophs) was developed to integrate most trophic diversity present in the plankton. The model was implemented in two variants - which we named ‘green’ and ‘blue’ - characterized by opposite amounts of phytoplankton biomass and representing, respectively, bloom and non-bloom states of the system. Taxonomically disaggregated food-webs described herein allowed to shed light on how components of the plankton community changed their trophic behavior in the two different conditions, and modified the overall functioning of the plankton food web. The green and blue food-webs showed distinct organizations in terms of trophic roles of the nodes and carbon fluxes between them. Such re-organization stemmed from switches in selective grazing by both metazoan and protozoan consumers. Switches in food-web structure resulted in relatively small differences in the efficiency of material transfer towards higher trophic levels. For instance, from green to blue states, a seven-fold decrease in phytoplankton biomass translated into only a two-fold decrease in potential planktivorous fish biomass. By linking diversity, structure and function in the plankton food-web, we discuss the role of internal mechanisms, relying on species-specific functionalities, in driving the ‘adaptive’ responses of plankton communities to perturbations.

Extent and ecological consequences of hunting in Central African rainforests in the twenty-first century

PubMed Central

Abernethy, K. A.; Coad, L.; Taylor, G.; Lee, M. E.; Maisels, F.

2013-01-01

Humans have hunted wildlife in Central Africa for millennia. Today, however, many species are being rapidly extirpated and sanctuaries for wildlife are dwindling. Almost all Central Africa's forests are now accessible to hunters. Drastic declines of large mammals have been caused in the past 20 years by the commercial trade for meat or ivory. We review a growing body of empirical data which shows that trophic webs are significantly disrupted in the region, with knock-on effects for other ecological functions, including seed dispersal and forest regeneration. Plausible scenarios for land-use change indicate that increasing extraction pressure on Central African forests is likely to usher in new worker populations and to intensify the hunting impacts and trophic cascade disruption already in progress, unless serious efforts are made for hunting regulation. The profound ecological changes initiated by hunting will not mitigate and may even exacerbate the predicted effects of climate change for the region. We hypothesize that, in the near future, the trophic changes brought about by hunting will have a larger and more rapid impact on Central African rainforest structure and function than the direct impacts of climate change on the vegetation. Immediate hunting regulation is vital for the survival of the Central African rainforest ecosystem. PMID:23878333

Extent and ecological consequences of hunting in Central African rainforests in the twenty-first century.

PubMed

Abernethy, K A; Coad, L; Taylor, G; Lee, M E; Maisels, F

2013-01-01

Humans have hunted wildlife in Central Africa for millennia. Today, however, many species are being rapidly extirpated and sanctuaries for wildlife are dwindling. Almost all Central Africa's forests are now accessible to hunters. Drastic declines of large mammals have been caused in the past 20 years by the commercial trade for meat or ivory. We review a growing body of empirical data which shows that trophic webs are significantly disrupted in the region, with knock-on effects for other ecological functions, including seed dispersal and forest regeneration. Plausible scenarios for land-use change indicate that increasing extraction pressure on Central African forests is likely to usher in new worker populations and to intensify the hunting impacts and trophic cascade disruption already in progress, unless serious efforts are made for hunting regulation. The profound ecological changes initiated by hunting will not mitigate and may even exacerbate the predicted effects of climate change for the region. We hypothesize that, in the near future, the trophic changes brought about by hunting will have a larger and more rapid impact on Central African rainforest structure and function than the direct impacts of climate change on the vegetation. Immediate hunting regulation is vital for the survival of the Central African rainforest ecosystem.

The protozooplankton-ichthyoplankton trophic link: an overlooked aspect of aquatic food webs.

PubMed

Montagnes, David J S; Dower, John F; Figueiredo, Gisela M

2010-01-01

Since the introduction of the microbial loop concept, awareness of the role played by protozooplankton in marine food webs has grown. By consuming bacteria, and then being consumed by metazooplankton, protozoa form a trophic link that channels dissolved organic material into the "classic" marine food chain. Beyond enhancing energy transfer to higher trophic levels, protozoa play a key role in improving the food quality of metazooplankton. Here, we consider a third role played by protozoa, but one that has received comparatively little attention: that as prey items for ichthyoplankton. For >100 years it has been known that fish larvae consume protozoa. Despite this, fisheries scientists and biological oceanographers still largely ignore protozoa when assessing the foodweb dynamics that regulate the growth and survival of larval fish. We review evidence supporting the importance of the protozooplankton-ichthyoplankton link, including examples from the amateur aquarium trade, the commercial aquaculture industry, and contemporary studies of larval fish. We then consider why this potentially important link continues to receive very little attention. We conclude by offering suggestions for quantifying the importance of the protozooplankton-ichthyoplankton trophic link, using both existing methods and new technologies.

Biodiversity loss and turnover in alternative states in the Mediterranean Sea: a case study on meiofauna

PubMed Central

Bianchelli, Silvia; Buschi, Emanuela; Danovaro, Roberto; Pusceddu, Antonio

2016-01-01

In the Mediterranean Sea hard-bottom macroalgal meadows may switch to alternative and less-productive barrens grounds, as a result of sea urchins overgrazing. Meiofauna (and especially nematodes) represent key components of benthic ecosystems, are highly-diversified, sensitive to environmental change and anthropogenic impacts, but, so-far, have been neglected in studies on regime shifts. We report here that sedimentary organic matter contents, meiofaunal taxa richness and community composition, nematode α- and β-biodiversity vary significantly between alternative macroalgal and barren states. The observed differences are consistent in six areas spread across the Mediterranean Sea, irrespective of barren extent. Our results suggest also that the low biodiversity levels in barren states are the result of habitat loss/fragmentation, which is associated also with a lower availability of trophic resources. Furthermore, differences in meiofaunal and nematode abundance, biomass and diversity between macroalgal meadow and barren states persist when the latter is not fully formed, or consists of patches interspersed in macroalgal meadows. Since barren grounds are expanding rapidly along the Mediterranean Sea and meiofauna are a key trophic component in marine ecosystems, we suggest that the extension and persistence of barrens at the expenses of macroalgal meadows could also affect resilience of higher trophic level. PMID:27708343

Biodiversity loss and turnover in alternative states in the Mediterranean Sea: a case study on meiofauna.

PubMed

Bianchelli, Silvia; Buschi, Emanuela; Danovaro, Roberto; Pusceddu, Antonio

2016-10-06

In the Mediterranean Sea hard-bottom macroalgal meadows may switch to alternative and less-productive barrens grounds, as a result of sea urchins overgrazing. Meiofauna (and especially nematodes) represent key components of benthic ecosystems, are highly-diversified, sensitive to environmental change and anthropogenic impacts, but, so-far, have been neglected in studies on regime shifts. We report here that sedimentary organic matter contents, meiofaunal taxa richness and community composition, nematode α- and β-biodiversity vary significantly between alternative macroalgal and barren states. The observed differences are consistent in six areas spread across the Mediterranean Sea, irrespective of barren extent. Our results suggest also that the low biodiversity levels in barren states are the result of habitat loss/fragmentation, which is associated also with a lower availability of trophic resources. Furthermore, differences in meiofaunal and nematode abundance, biomass and diversity between macroalgal meadow and barren states persist when the latter is not fully formed, or consists of patches interspersed in macroalgal meadows. Since barren grounds are expanding rapidly along the Mediterranean Sea and meiofauna are a key trophic component in marine ecosystems, we suggest that the extension and persistence of barrens at the expenses of macroalgal meadows could also affect resilience of higher trophic level.

Biodiversity loss and turnover in alternative states in the Mediterranean Sea: a case study on meiofauna

NASA Astrophysics Data System (ADS)

Bianchelli, Silvia; Buschi, Emanuela; Danovaro, Roberto; Pusceddu, Antonio

2016-10-01

In the Mediterranean Sea hard-bottom macroalgal meadows may switch to alternative and less-productive barrens grounds, as a result of sea urchins overgrazing. Meiofauna (and especially nematodes) represent key components of benthic ecosystems, are highly-diversified, sensitive to environmental change and anthropogenic impacts, but, so-far, have been neglected in studies on regime shifts. We report here that sedimentary organic matter contents, meiofaunal taxa richness and community composition, nematode α- and β-biodiversity vary significantly between alternative macroalgal and barren states. The observed differences are consistent in six areas spread across the Mediterranean Sea, irrespective of barren extent. Our results suggest also that the low biodiversity levels in barren states are the result of habitat loss/fragmentation, which is associated also with a lower availability of trophic resources. Furthermore, differences in meiofaunal and nematode abundance, biomass and diversity between macroalgal meadow and barren states persist when the latter is not fully formed, or consists of patches interspersed in macroalgal meadows. Since barren grounds are expanding rapidly along the Mediterranean Sea and meiofauna are a key trophic component in marine ecosystems, we suggest that the extension and persistence of barrens at the expenses of macroalgal meadows could also affect resilience of higher trophic level.

Patterns in Benthic Biodiversity Link Lake Trophic Status to Structure and Potential Function of Three Large, Deep Lakes

PubMed Central

Hayford, Barbara L.; Caires, Andrea M.; Chandra, Sudeep; Girdner, Scott F.

2015-01-01

Relative to their scarcity, large, deep lakes support a large proportion of the world’s freshwater species. This biodiversity is threatened by human development and is in need of conservation. Direct comparison of biodiversity is the basis of biological monitoring for conservation but is difficult to conduct between large, insular ecosystems. The objective of our study was to conduct such a comparison of benthic biodiversity between three of the world’s largest lakes: Lake Tahoe, USA; Lake Hövsgöl, Mongolia; and Crater Lake, USA. We examined biodiversity of common benthic organism, the non-biting midges (Chironomidae) and determined lake trophic status using chironomid-based lake typology, tested whether community structure was similar between the three lakes despite geographic distance; and tested whether chironomid diversity would show significant variation within and between lakes. Typology analysis indicated that Lake Hövsgöl was ultra-oligotrophic, Crater Lake was oligotrophic, and Lake Tahoe was borderline oligotrophic/mesotrophic. These results were similar to traditional pelagic measures of lake trophic status for Lake Hövsgöl and Crater Lake but differed for Lake Tahoe, which has been designated as ultra-oligotrophic by traditional pelagic measures such as transparency found in the literature. Analysis of similarity showed that Lake Tahoe and Lake Hövsgöl chironomid communities were more similar to each other than either was to Crater Lake communities. Diversity varied between the three lakes and spatially within each lake. This research shows that chironomid communities from these large lakes were sensitive to trophic conditions. Chironomid communities were similar between the deep environments of Lake Hövsgöl and Lake Tahoe, indicating that chironomid communities from these lakes may be useful in comparing trophic state changes in large lakes. Spatial variation in Lake Tahoe’s diversity is indicative of differential response of chironomid communities to nutrient enrichment which may be an indication of changes in trophic state within and across habitats. PMID:25594516

The use of ERTS imagery for lake classification. [turbidity due to phytoplankton

NASA Technical Reports Server (NTRS)

Scarpace, F. L.; Wade, R. E.; Fisher, L. T.

1975-01-01

The feasibility of using photographic representations of the ERTS imagery to classify lakes in the State of Wisconsin as to their trophic level was studied. Densitometric readings in band 5 of ERTS 70 mm imagery were taken for all the lakes in Wisconsin greater than 100 acres (approximately 1000 lakes). An algorithm has been developed from ground truth measurements to predict from satellite imagery an indicator of trophic status.

Axonal Degeneration Is Regulated by a Transcriptional Program that Coordinates Expression of Pro- and Anti-degenerative Factors.

PubMed

Maor-Nof, Maya; Romi, Erez; Sar Shalom, Hadas; Ulisse, Valeria; Raanan, Calanit; Nof, Aviv; Leshkowitz, Dena; Lang, Roland; Yaron, Avraham

2016-12-07

Developmental neuronal cell death and axonal elimination are controlled by transcriptional programs, of which their nature and the function of their components remain elusive. Here, we identified the dual specificity phosphatase Dusp16 as part of trophic deprivation-induced transcriptome in sensory neurons. Ablation of Dusp16 enhanced axonal degeneration in response to trophic withdrawal, suggesting that it has a protective function. Moreover, axonal skin innervation was severely reduced while neuronal elimination was increased in the Dusp16 knockout. Mechanistically, Dusp16 negatively regulates the transcription factor p53 and antagonizes the expression of the pro-degenerative factor, Puma (p53 upregulated modulator of apoptosis). Co-ablation of Puma with Dusp16 protected axons from rapid degeneration and specifically reversed axonal innervation loss early in development with no effect on neuronal deficits. Overall, these results reveal that physiological axonal elimination is regulated by a transcriptional program that integrates regressive and progressive elements and identify Dusp16 as a new axonal preserving factor. Copyright © 2016 Elsevier Inc. All rights reserved.

The evolution of trophic transmission

USGS Publications Warehouse

Lafferty, Kevin D.

1999-01-01

Parasite increased trophic transmission (PITT) is one of the more fascinating tales of parasite evolution. The implications of this go beyond cocktail party anecdotes and science fiction plots as the phenomenon is pervasive and likely to be ecologically and evolutionarily important. Although the subject has already received substantial review, Kevin Lafferty here focuses on evolutionary aspects that have not been fully explored, specifically: (1) How strong should PITT be? (2) How might sexual selection and limb autotomy facilitate PITT? (3) How might infrapopulation regulation in final hosts be important in determining avoidance of infected prey? And (4) what happens when more than one species of parasite is in the same intermediate host?

Effects of Environmental Factors on Nutrients Release at Sediment-Water Interface and Assessment of Trophic Status for a Typical Shallow Lake, Northwest China

PubMed Central

Hou, Dekun; He, Jiang; Lü, Changwei; Sun, Ying; Zhang, Fujin; Otgonbayar, Khureldavaa

2013-01-01

Surface sediment and water samples were collected from Daihai Lake to study the biogeochemical characteristics of nitrogen and phosphorus, to estimate the loads of these nutrients, and to assess their effects on water quality. The contents and spatial distributions of total phosphorus (TP), total nitrogen (TN), and different nitrogen forms in sediments were analyzed. The results showed that concentrations of TN and TP in surface sediments ranged from 0.27 to 1.78 g/kg and from 558.31 to 891.29 mg/kg, respectively. Ratios of C : N ranged between 8.2 and 12.1, which indicated that nitrogen accumulated came mainly from terrestrial source. Ratios of N : P in all sampling sites were below 10, which indicated that N was the limiting nutrient for algal growth in this lake. Effects of environment factors on the release of nitrogen and phosphorus in lake sediments were also determined; high pH values could encourage the release of nitrogen and phosphorus. Modified Carlson's trophic state index (TSIM) and comprehensive trophic state index (TSIC) were applied to ascertain the trophic classification of the studied lake, and the values of TSIM and TSIC ranged from 53.72 to 70.61 and from 47.73 to 53.67, respectively, which indicated that the Daihai Lake was in the stage of hypereutropher. PMID:24023535

Mercury cycling in stream ecosystems. 3. Trophic dynamics and methylmercury bioaccumulation

USGS Publications Warehouse

Chasar, L.C.; Scudder, B.C.; Stewart, A.R.; Bell, A.H.; Aiken, G.R.

2009-01-01

Trophic dynamics (community composition and feeding relationships) have been identified as important drivers of methylmercury (MeHg) bioaccumulation in lakes, reservoirs, and marine ecosystems. The relative importance of trophic dynamics and geochemical controls on MeHg bioaccumulation in streams, however, remains poorly characterized. MeHg bioaccumulation was evaluated in eight stream ecosystems across the United States (Oregon, Wisconsin, and Florida) spanning large ranges in climate, landscape characteristics, atmospheric Hg deposition, and stream chemistry. Across all geographic regions and all streams, concentrations of total Hg (THg) in top predator fish and forage fish, and MeHg in invertebrates, were strongly positively correlated to concentrations of filtered THg (FTHg), filtered MeHg (FMeHg), and dissolved organic carbon (DOC); to DOC complexity (as measured by specific ultraviolet absorbance); and to percent wetland in the stream basins. Correlations were strongest for nonurban streams. Although regressions of log[Hg] versus ??15N indicate that Hg in biota increased significantly with increasing trophic position within seven of eight individual streams, Hg concentrations in top predator fish (including cutthroat, rainbow, and brown trout; green sunfish; and largemouth bass) were not strongly influenced by differences in relative trophic position. Slopes of log[Hg] versus ??15N, an indicator of the efficiency of trophic enrichment, ranged from 0.14 to 0.27 for all streams. These data suggest that, across the large ranges in FTHg (0.14-14.2 ng L-1), FMeHg (0.023-1.03 ng L-1), and DOC (0.50-61.0 mg L-1) found in this study, Hg contamination in top predator fish in streams likely is dominated by the amount of MeHg available for uptake at the base of the food web rather than by differences in the trophic position of top predator fish. ?? 2009 American Chemical Society.

Developmentally Regulated Expression of the Nerve Growth Factor Receptor Gene in the Periphery and Brain

NASA Astrophysics Data System (ADS)

Buck, C. R.; Martinez, Humberto J.; Black, Ira B.; Chao, Moses V.

1987-05-01

Nerve growth factor (NGF) regulates development and maintenance of function of peripheral sympathetic and sensory neurons. A potential role for the trophic factor in brain has been detected only recently. The ability of a cell to respond to NGF is due, in part, to expression of specific receptors on the cell surface. To study tissue-specific expression of the NGF receptor gene, we have used sensitive cRNA probes for detection of NGF receptor mRNA. Our studies indicate that the receptor gene is selectively and specifically expressed in sympathetic (superior cervical) and sensory (dorsal root) ganglia in the periphery, and by the septum-basal forebrain centrally, in the neonatal rat in vivo. Moreover, examination of tissues from neonatal and adult rats reveals a marked reduction in steady-state NGF receptor mRNA levels in sensory ganglia. In contrast, a 2- to 4-fold increase was observed in the basal forebrain and in the sympathetic ganglia over the same time period. Our observations suggest that NGF receptor mRNA expression is developmentally regulated in specific areas of the nervous system in a differential fashion.

Volcanic nutrient inputs and trophic state of Lake Caviahue, Patagonia, Argentina

NASA Astrophysics Data System (ADS)

Pedrozo, Fernando L.; Temporetti, Pedro F.; Beamud, Guadalupe; Diaz, Mónica M.

2008-12-01

The strategies for eutrophication control, remediation, and policy management are often defined for neutral to alkaline freshwater systems, as they are most suitable for human use. The influence of nutrients on eutrophication in a naturally-acidic lake is poorly known. The main purpose of the present work is to evaluate the significance of volcanic nutrients in the control of the trophic state of the acidic Lake Caviahue, located at North Patagonia, Argentina. Acidic water systems were most studied on artificial acidified lakes, such as mining lakes in Germany or pit lakes in the United States. Lake Caviahue received a very high P load (42-192 ton P/yr) and low N load (14 ton N/yr), mainly as ammonium with quite low N:P ratios (< 1.0). The magmatic activity of the Copahue volcano represents the main natural contribution of nutrients and acidity to the Lake Caviahue. The lake is oligotrophic in terms of CHLa. Neither the transparency nor the nutrient, dissolved or particulate, contents are to date representative of the trophic state of the lake. High P loads do not imply the eutrophication of the lake. We suggest that nitrogen and not phosphorus represents the key control nutrient in volcanically acidified lakes as TON was better related to CHLa observed (0.13-0.36 mg/m 3) in the lake. The pH increased around one unit (pH 2.0-3.0) during the last five years suggesting that the lake has not yet returned to a stable state.

Sensitivity of secondary production and export flux to choice of trophic transfer formulation in marine ecosystem models

NASA Astrophysics Data System (ADS)

Anderson, Thomas R.; Hessen, Dag O.; Mitra, Aditee; Mayor, Daniel J.; Yool, Andrew

2013-09-01

The performance of four contemporary formulations describing trophic transfer, which have strongly contrasting assumptions as regards the way that consumer growth is calculated as a function of food C:N ratio and in the fate of non-limiting substrates, was compared in two settings: a simple steady-state ecosystem model and a 3D biogeochemical general circulation model. Considerable variation was seen in predictions for primary production, transfer to higher trophic levels and export to the ocean interior. The physiological basis of the various assumptions underpinning the chosen formulations is open to question. Assumptions include Liebig-style limitation of growth, strict homeostasis in zooplankton biomass, and whether excess C and N are released by voiding in faecal pellets or via respiration/excretion post-absorption by the gut. Deciding upon the most appropriate means of formulating trophic transfer is not straightforward because, despite advances in ecological stoichiometry, the physiological mechanisms underlying these phenomena remain incompletely understood. Nevertheless, worrying inconsistencies are evident in the way in which fundamental transfer processes are justified and parameterised in the current generation of marine ecosystem models, manifested in the resulting simulations of ocean biogeochemistry. Our work highlights the need for modellers to revisit and appraise the equations and parameter values used to describe trophic transfer in marine ecosystem models.

Detecting Potential Water Quality Issues by Mapping Trophic Status Using Google Earth Engine

NASA Astrophysics Data System (ADS)

Nguy-Robertson, A. L.; Harvey, K.; Huening, V.; Robinson, H.

2017-12-01

The identification, timing, and spatial distribution of recurrent algal blooms and aquatic vegetation can help water managers and policy makers make better water resource decisions. In many parts of the world there is little monitoring or reporting of water quality due to the required costs and effort to collect and process water samples. We propose to use Google Earth Engine to quickly identify the recurrence of trophic states in global inland water systems. Utilizing Landsat and Sentinel multispectral imagery, inland water quality parameters (i.e. chlorophyll a concentration) can be estimated and waters can be classified by trophic state; oligotrophic, mesotrophic, eutrophic, and hypereutrophic. The recurrence of eutrophic and hypereutrophic observations can highlight potentially problematic locations where algal blooms or aquatic vegetation occur routinely. Eutrophic and hypereutrophic waters commonly include many harmful algal blooms and waters prone to fish die-offs from hypoxia. While these maps may be limited by the accuracy of the algorithms utilized to estimate chlorophyll a; relative comparisons at a local scale can help water managers to focus limited resources.

Response in the trophic state of stratified lakes to changes in hydrology and water level: potential effects of climate change

USGS Publications Warehouse

Robertson, Dale M.; Rose, William J.

2011-01-01

To determine how climate-induced changes in hydrology and water level may affect the trophic state (productivity) of stratified lakes, two relatively pristine dimictic temperate lakes in Wisconsin, USA, were examined. Both are closed-basin lakes that experience changes in water level and degradation in water quality during periods of high water. One, a seepage lake with no inlets or outlets, has a small drainage basin and hydrology dominated by precipitation and groundwater exchange causing small changes in water and phosphorus (P) loading, which resulted in small changes in water level, P concentrations, and productivity. The other, a terminal lake with inlets but no outlets, has a large drainage basin and hydrology dominated by runoff causing large changes in water and P loading, which resulted in large changes in water level, P concentrations, and productivity. Eutrophication models accurately predicted the effects of changes in hydrology, P loading, and water level on their trophic state. If climate changes, larger changes in hydrology and water levels than previously observed could occur. If this causes increased water and P loading, stratified (dimictic and monomictic) lakes are expected to experience higher water levels and become more eutrophic, especially those with large developed drainage basins.

The basic helix-loop-helix transcription factor Nex-1/Math-2 promotes neuronal survival of PC12 cells by modulating the dynamic expression of anti-apoptotic and cell cycle regulators

PubMed Central

Uittenbogaard, Martine; Chiaramello, Anne

2006-01-01

The basic helix-loop-helix transcription factor Nex1/Math-2 belongs to the NeuroD subfamily, which plays a critical role during neuronal differentiation and maintenance of the differentiated state. Previously, we demonstrated that Nex1 is a key regulatory component of the nerve growth factor (NGF) pathway. Further supporting this hypothesis, this study shows that Nex1 has survival-inducing properties similar to NGF, as Nex1-overexpressing PC12 cells survive in the absence of trophic factors. We dissected the molecular mechanism by which Nex1 confers neuroprotection upon serum removal and found that constitutive expression of Nex1 maintained the expression of specific G1 phase cyclin-dependent kinase inhibitors and concomitantly induced a dynamic expression profile of key anti-apoptotic regulators. This study provides the first evidence of the underlying mechanism by which a member of the NeuroD-subfamily promotes an active anti-apoptotic program essential to the survival of neurons. Our results suggest that the survival program may be viewed as an integral component of the intrinsic programming of the differ entiated state. PMID:15659228

Individual diet variation in a marine fish assemblage: Optimal Foraging Theory, Niche Variation Hypothesis and functional identity

NASA Astrophysics Data System (ADS)

Cachera, M.; Ernande, B.; Villanueva, M. C.; Lefebvre, S.

2017-02-01

Individual diet variation (i.e. diet variation among individuals) impacts intra- and inter-specific interactions. Investigating its sources and relationship with species trophic niche organization is important for understanding community structure and dynamics. Individual diet variation may increase with intra-specific phenotypic (or "individual state") variation and habitat variability, according to Optimal Foraging Theory (OFT), and with species trophic niche width, according to the Niche Variation Hypothesis (NVH). OFT proposes "proximate sources" of individual diet variation such as variations in habitat or size whereas NVH relies on "ultimate sources" related to the competitive balance between intra- and inter-specific competitions. The latter implies as a corollary that species trophic niche overlap, taken as inter-specific competition measure, decreases as species niche width and individual niche variation increase. We tested the complementary predictions of OFT and NVH in a marine fish assemblage using stomach content data and associated trophic niche metrics. The NVH predictions were tested between species of the assemblage and decomposed into a between- and a within-functional group component to assess the potential influence of species' ecological function. For most species, individual diet variation and niche overlap were consistently larger than expected. Individual diet variation increased with intra-specific variability in individual state and habitat, as expected from OFT. It also increased with species niche width but in compliance with the null expectation, thus not supporting the NVH. In contrast, species niche overlap increased significantly less than null expectation with both species niche width and individual diet variation, supporting NVH corollary. The between- and within-functional group components of the NVH relationships were consistent with those between species at the assemblage level. Changing the number of prey categories used to describe diet (from 16 to 41) did not change the results qualitatively. These results suggest that, besides proximate sources, intra-specific competition favors higher individual diet variation than expected while inter-specific competition limits the increase of individual diet variation and of species niche overlap with species niche expansion. This reveals partial trophic resource partitioning between species. Various niche metrics used in combination allow inferring competition effects on trophic niches' organization within communities.

Context-dependent consumer control in New England tidal wetlands.

PubMed

Moore, Alexandria

2018-01-01

Recent studies in coastal wetlands have indicated that consumers may play an important role in regulating large-scale ecosystem processes. Predator removal experiments have shown significant differences in above-ground biomass production in the presence of higher level consumers, or predators. These results indicate that predators play an important role in regulating biomass production, but the extent to which this regulation impacts additional ecosystem functions, such as nutrient cycling and organic matter accumulation, is unclear. This study evaluated the impact that consumers have on large-scale ecosystem processes within southern New England tidal wetlands and contributes to the general understanding of trophic control in these systems. I established enclosure cages within three coastal wetlands and manipulated the presence of green crab predators to assess how trophic interactions affect ecosystem functions. Findings suggest that although these consumers may exert some top-down effects, other environmental factors, such as other consumers not studied here or bottom-up interactions, may variably play a larger role in the maintenance of ecosystem processes within the region. These results indicate that the loss of top-down control as an important mechanism influencing ecosystem functions may not hold for all wetlands along the full extent of the New England coastline.

Context-dependent consumer control in New England tidal wetlands

PubMed Central

2018-01-01

Recent studies in coastal wetlands have indicated that consumers may play an important role in regulating large-scale ecosystem processes. Predator removal experiments have shown significant differences in above-ground biomass production in the presence of higher level consumers, or predators. These results indicate that predators play an important role in regulating biomass production, but the extent to which this regulation impacts additional ecosystem functions, such as nutrient cycling and organic matter accumulation, is unclear. This study evaluated the impact that consumers have on large-scale ecosystem processes within southern New England tidal wetlands and contributes to the general understanding of trophic control in these systems. I established enclosure cages within three coastal wetlands and manipulated the presence of green crab predators to assess how trophic interactions affect ecosystem functions. Findings suggest that although these consumers may exert some top-down effects, other environmental factors, such as other consumers not studied here or bottom-up interactions, may variably play a larger role in the maintenance of ecosystem processes within the region. These results indicate that the loss of top-down control as an important mechanism influencing ecosystem functions may not hold for all wetlands along the full extent of the New England coastline. PMID:29771961

40 CFR 35.1620-5 - State work programs and lake priority lists.

Code of Federal Regulations, 2010 CFR

2010-07-01

... lakes according to trophic condition (§ 35.1630) and to set priorities for implementing clean lakes... 40 Protection of Environment 1 2010-07-01 2010-07-01 false State work programs and lake priority... Publicly Owned Freshwater Lakes § 35.1620-5 State work programs and lake priority lists. (a)(1) A State...

One year outcomes in patients with acute lung injury randomised to initial trophic or full enteral feeding: prospective follow-up of EDEN randomised trial.

PubMed

Needham, Dale M; Dinglas, Victor D; Bienvenu, O Joseph; Colantuoni, Elizabeth; Wozniak, Amy W; Rice, Todd W; Hopkins, Ramona O

2013-03-19

To evaluate the effect of initial low energy permissive underfeeding ("trophic feeding") versus full energy enteral feeding ("full feeding") on physical function and secondary outcomes in patients with acute lung injury. Prospective longitudinal follow-up evaluation of the NHLBI ARDS Clinical Trials Network's EDEN trial 41hospitals in the United States. 525 patients with acute lung injury. Randomised assignment to trophic or full feeding for up to six days; thereafter, all patients still receiving mechanical ventilation received full feeding. Blinded assessment of the age and sex adjusted physical function domain of the SF-36 instrument at 12 months after acute lung injury. Secondary outcome measures included survival; physical, psychological, and cognitive functioning; quality of life; and employment status at six and 12 months. After acute lung injury, patients had substantial physical, psychological, and cognitive impairments, reduced quality of life, and impaired return to work. Initial trophic versus full feeding did not affect mean SF-36 physical function at 12 months (55 (SD 33) v 55 (31), P=0.54), survival to 12 months (65% v 63%, P=0.63), or nearly all of the secondary outcomes. In survivors of acute lung injury, there was no difference in physical function, survival, or multiple secondary outcomes at 6 and 12 month follow-up after initial trophic or full enteral feeding. NCT No 00719446.

Integrin-Mediated Transforming Growth Factor-β Activation Regulates Homeostasis of the Pulmonary Epithelial-Mesenchymal Trophic Unit

PubMed Central

Araya, Jun; Cambier, Stephanie; Morris, Alanna; Finkbeiner, Walter; Nishimura, Stephen L.

2006-01-01

Trophic interactions between pulmonary epithelial and mesenchymal cell types, known as the epithelial-mesenchymal trophic unit (EMTU), are crucial in lung development and lung disease. Transforming growth factor (TGF)-β is a key factor in mediating these interactions, but it is expressed in a latent form that requires activation to be functional. Using intact fetal tracheal tissue and primary cultures of fetal tracheal epithelial cells and fibroblasts, we demonstrate that a subset of integrins, αvβ6 and αvβ8, are responsible for almost all of the TGF-β activation in the EMTU. Both αvβ8 and αvβ6 contribute to fetal tracheal epithelial activation of TGF-β, whereas only αvβ8 contributes to fetal tracheal fibroblast activation of TGF-β. Interestingly, fetal tracheal epithelial αvβ8-mediated TGF-β activation can be enhanced by phorbol esters, likely because of the increased activity of MT1-MMP, an essential co-factor in αvβ8-mediated activation of TGF-β. Autocrine αvβ8-mediated TGF-β activation by fetal tracheal fibroblasts results in suppression of both transcription and secretion of hepatocyte growth factor, which is sufficient to affect phosphorylation of the airway epithelial hepatocyte growth factor receptor, c-Met, as well as airway epithelial proliferation in a co-culture model of the EMTU. These findings elucidate the function and complex regulation of integrin-mediated activation of TGF-β within the EMTU. PMID:16877343

Integrin-mediated transforming growth factor-beta activation regulates homeostasis of the pulmonary epithelial-mesenchymal trophic unit.

PubMed

Araya, Jun; Cambier, Stephanie; Morris, Alanna; Finkbeiner, Walter; Nishimura, Stephen L

2006-08-01

Trophic interactions between pulmonary epithelial and mesenchymal cell types, known as the epithelial-mesenchymal trophic unit (EMTU), are crucial in lung development and lung disease. Transforming growth factor (TGF)-beta is a key factor in mediating these interactions, but it is expressed in a latent form that requires activation to be functional. Using intact fetal tracheal tissue and primary cultures of fetal tracheal epithelial cells and fibroblasts, we demonstrate that a subset of integrins, alpha(v)beta(6) and alpha(v)beta(8), are responsible for almost all of the TGF-beta activation in the EMTU. Both alpha(v)beta(8) and alpha(v)beta(6) contribute to fetal tracheal epithelial activation of TGF-beta, whereas only alpha(v)beta(8) contributes to fetal tracheal fibroblast activation of TGF-beta. Interestingly, fetal tracheal epithelial alpha(v)beta(8)-mediated TGF-beta activation can be enhanced by phorbol esters, likely because of the increased activity of MT1-MMP, an essential co-factor in alpha(v)beta(8)-mediated activation of TGF-beta. Autocrine alpha(v)beta(8)-mediated TGF-beta activation by fetal tracheal fibroblasts results in suppression of both transcription and secretion of hepatocyte growth factor, which is sufficient to affect phosphorylation of the airway epithelial hepatocyte growth factor receptor, c-Met, as well as airway epithelial proliferation in a co-culture model of the EMTU. These findings elucidate the function and complex regulation of integrin-mediated activation of TGF-beta within the EMTU.

Trophic cascades linking wolves (Canis lupus), coyotes (Canis latrans), and small mammals

USGS Publications Warehouse

Miller, B.J.; Harlow, H.J.; Harlow, T.S.; Biggins, D.; Ripple, W.J.

2012-01-01

When large carnivores are extirpated from ecosystems that evolved with apex predators, these systems can change at the herbivore and plant trophic levels. Such changes across trophic levels are called cascading effects and they are very important to conservation. Studies on the effects of reintroduced wolves in Yellowstone National Park have examined the interaction pathway of wolves (Canis lupus L., 1758) to ungulates to plants. This study examines the interaction effects of wolves to coyotes to rodents (reversing mesopredator release in the absence of wolves). Coyotes (Canis latrans Say, 1823) generally avoided areas near a wolf den. However, when in the proximity of a den, they used woody habitats (pine or sage) compared with herbaceous habitats (grass or forb or sedge)- when they were away from the wolf den. Our data suggested a significant increase in rodent numbers, particularly voles (genus Microtus Schrank, 1798), during the 3-year study on plots that were within 3 km of the wolf den, but we did not detect a significant change in rodent numbers over time for more distant plots. Predation by coyotes may have depressed numbers of small mammals in areas away from the wolf den. These factors indicate a top-down effect by wolves on coyotes and subsequently on the rodents of the area. Restoration of wolves could be a powerful tool for regulating predation at lower trophic levels.

Heavy metal transfers between trophic compartments in different ecosystems in Galicia (Northwest Spain): Essential elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gonzalez, X.I.; Aboal, J.R.; Fernandez, J.A.

2008-11-15

In the present study, we determined the concentrations of Cu, Fe, Mn, and Zn in soil and several trophic compartments at a total of 16 sampling stations. The trophic compartments studied were primary producers, represented by two species of terrestrial mosses (Pseudoescleropodium purum and Hypnum cupressiforme) and oak trees (Quercus robur or Q. pyrenaica); primary consumers, represented by the wood mouse (Apodemus sylvaticus) and the yellow necked mouse (A. flavicollis); secondary consumers, represented by the shrew (Sorex granarius); and finally, detritivores, represented by slugs (Arion ater). Thirteen of the sampling stations were located in mature oak woodlands (Quercus sp.); twomore » of the sampling stations were located in the area surrounding a restored lignite mine dump, and the other in an ultrabasic area. The analytical determinations revealed a lack of significant correlations among trophic compartments, possibly caused by effective regulation of metals by organisms and/or spatial variation in availability of metals from soil or food. Furthermore, the only element that showed a clear pattern of biomagnification was Cu; as for the other elements, there was always some divergence from such a pattern. Finally, the patterns of bioaccumulation in contaminated and woodland sampling stations were very similar, although there was enrichment of the concentrations of Cu, Mn, and Zn in the mice viscera, which, except for Mn, were related to higher edaphic concentrations.« less

Are all temperate lakes eutrophying in a warmer world?

NASA Astrophysics Data System (ADS)

Paltsev, A.; Creed, I. F.

2017-12-01

Freshwater lakes are at risk of eutrophication due to climate change and intensification of human activities on the planet. In relatively undisturbed areas of the temperate forest biome, lakes are "sentinels" of the effects of rising temperatures. We hypothesise that rising temperatures are driving a shift from nutrient-poor oligotrophic states to nutrient-rich eutrophic states. To test this hypothesis, we examined a time series of satellite based chlorophyll-a (a proxy of algal biomass) of 12,000+ lakes over 30 years in the Canadian portion of the Laurentian Great Lakes basin. From the time series, non-stationary trends (detected by Mann-Kendall analysis) and stationary cycles (revealed through Morlet wavelet analysis) were removed, and the standard deviation (SD) of the remaining residuals was used as an indicator of lake stability. Four classes of lake stability were identified: (1) stable (SD is consistently low); (2) destabilizing (SD increases over time); (3) unstable (SD is consistently high); and (4) stabilizing lakes (SD decreases over time). Stable lakes were either oligotrophic or eutrophic indicating the presence of two stable states in the region. Destabilizing lakes were shifting from oligotrophic to lakes with a higher trophic status (indicating eutrophication), unstable lakes were mostly mesotrophic, and stabilizing lakes were shifting from eutrophic to the lakes with lower trophic status (indicating oligotrophication). In contrast to common expectations, while many lakes (2142) were shifting from oligotrophic to eutrophic states, more lakes (3199) were showing the opposite trend and shifting from eutrophic to oligotrophic states. This finding reveals a complexity of lake responses to rising temperatures and the need to improve understanding of why some lakes shift while others do not. Future work is focused on exploring the interactive effects of global, regional, and local drivers of lake trophic states.

Skeletal and cardiac muscle pericytes: Functions and therapeutic potential

PubMed Central

Murray, Iain R.; Baily, James E.; Chen, William C.W.; Dar, Ayelet; Gonzalez, Zaniah N.; Jensen, Andrew R.; Petrigliano, Frank A.; Deb, Arjun; Henderson, Neil C.

2017-01-01

Pericytes are periendothelial mesenchymal cells residing within the microvasculature. Skeletal muscle and cardiac pericytes are now recognized to fulfill an increasing number of functions in normal tissue homeostasis, including contributing to microvascular function by maintaining vessel stability and regulating capillary flow. In the setting of muscle injury, pericytes contribute to a regenerative microenvironment through release of trophic factors and by modulating local immune responses. In skeletal muscle, pericytes also directly enhance tissue healing by differentiating into myofibers. Conversely, pericytes have also been implicated in the development of disease states, including fibrosis, heterotopic ossication and calcification, atherosclerosis, and tumor angiogenesis. Despite increased recognition of pericyte heterogeneity, it is not yet clear whether specific subsets of pericytes are responsible for individual functions in skeletal and cardiac muscle homeostasis and disease. PMID:27595928

Concentrations and trophic interactions of novel brominated flame retardants, HBCD, and PBDEs in zooplankton and fish from Lake Maggiore (Northern Italy).

PubMed

Poma, Giulia; Volta, Pietro; Roscioli, Claudio; Bettinetti, Roberta; Guzzella, Licia

2014-05-15

Following the release of the international regulations on PBDEs and HBCD, the aim of this study is to evaluate the concentrations of novel brominated flame retardants (NBFRs), including 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), decabromodiphenyl ethane (DBDPE), hexabromobenzene (HBB), and pentabromoethylbenzene (PBEB), in an Italian subalpine lake located in a populated and industrial area. The study investigated specifically the potential BFR biomagnification in a particular lake's pelagic food web, whose structure and dynamics were evaluated using the Stable Isotope Analysis. The potential BFR biomagnification was investigated by using the trophic-level adjusted BMFs and Trophic Magnification Factors (TMFs), confirming that HBCD and some PBDE congeners are able to biomagnify within food webs. Comparing the calculated values of BMFTL and TMF, a significant positive correlation was observed between the two factors, suggesting that the use of BMFTL to investigate the biomagnification potential of organic chemical compounds might be an appropriate approach when a simple food web is considered. Copyright © 2014 Elsevier B.V. All rights reserved.

Imprudent fishing harvests and consequent trophic cascades on the West Florida shelf over the last half century: A harbinger of increased human deaths from paralytic shellfish poisoning along the southeastern United States, in response to oligotrophication?

NASA Astrophysics Data System (ADS)

Walsh, J. J.; Tomas, C. R.; Steidinger, K. A.; Lenes, J. M.; Chen, F. R.; Weisberg, R. H.; Zheng, L.; Landsberg, J. H.; Vargo, G. A.; Heil, C. A.

2011-06-01

Within the context of ubiquitous overfishing of piscivores, recent consequent increments of jellyfish and clupeids have occurred at the zooplanktivore trophic level in the eastern Gulf of Mexico (GOM), after overfishing of one of their predators, i.e. red snapper. Initiation of a local trophic cascade thence led to declines of herbivore stocks, documented here on the West Florida shelf. These exacerbating world-wide trophic cascades have resulted in larger harmful algal blooms (HABs), already present at the base of most coastal food webs. Impacts on human health have thus far been minimal within nutrient-rich coastal regions. To provide a setting for past morbidities, consideration is given to chronologies of other trophic cascades within eutrophic, cold water marine ecosystems of the Scotian Sea, in the Gulf of Alaska, off Southwest Africa, within the Barents, White, and Black Seas, in the Gulf of Maine, and finally in the North Sea. Next, comparison is now made here of recent ten-fold increments within Florida waters of both relatively benign and saxitoxic HABs, some of which are fatal to humans. These events are placed in a perspective of other warm shelf systems of the South China and Caribbean Seas to assess prior and possible future poison toxicities of oligotrophic coastal habitats. Past wide-spread kills of fishes and sea urchins over the Caribbean Sea and the downstream GOM are examined in relation to the potential transmission of dinoflagellate saxitoxin and other epizootic poison vectors by western boundary currents over larger "commons" than local embayments. Furthermore, since some HABs produce more potent saxitoxins upon nutrient depletion, recent decisions to ban seasonal fertilizer applications to Florida lawns may have unintended consequences. In the future, human-killing phytoplankton, rather than relatively benign fish-killing HABs of the past, may be dispersed along the southeastern United States seaboard.

Seasonal Change in Trophic Niche of Adfluvial Arctic Grayling (Thymallus arcticus) and Coexisting Fishes in a High-Elevation Lake System

PubMed Central

Cutting, Kyle A.; Cross, Wyatt F.; Anderson, Michelle L.; Reese, Elizabeth G.

2016-01-01

Introduction of non-native species is a leading threat to global aquatic biodiversity. Competition between native and non-native species is often influenced by changes in suitable habitat or food availability. We investigated diet breadth and degree of trophic niche overlap for a fish assemblage of native and non-native species inhabiting a shallow, high elevation lake system. This assemblage includes one of the last remaining post-glacial endemic populations of adfluvial Arctic grayling (Thymallus arcticus) in the contiguous United States. We examined gut contents and stable isotope values of fish taxa in fall and spring to assess both short- (days) and long-term (few months) changes in trophic niches. We incorporate these short-term (gut contents) data into a secondary isotope analysis using a Bayesian statistical framework to estimate long-term trophic niche. Our data suggest that in this system, Arctic grayling share both a short- and long-term common food base with non-native trout of cutthroat x rainbow hybrid species (Oncorhynchus clarkia bouvieri x Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis). In addition, trophic niche overlap among Arctic grayling, hybrid trout, and brook trout appeared to be stronger during spring than fall. In contrast, the native species of Arctic grayling, burbot (Lota lota), and suckers (Catostomus spp.) largely consumed different prey items. Our results suggest strong seasonal differences in trophic niche overlap among Arctic grayling and non-native trout, with a potential for greatest competition for food during spring. We suggest that conservation of endemic Arctic grayling in high-elevation lakes will require recognition of the potential for coexisting non-native taxa to impede well-intentioned recovery efforts. PMID:27205901

Induction of the plasticity-associated immediate early gene Arc by stress and hallucinogens: role of brain-derived neurotrophic factor.

PubMed

Benekareddy, Madhurima; Nair, Amrita R; Dias, Brian G; Suri, Deepika; Autry, Anita E; Monteggia, Lisa M; Vaidya, Vidita A

2013-03-01

Exposure to stress and hallucinogens in adulthood evokes persistent alterations in neurocircuitry and emotional behaviour. The structural and functional changes induced by stress and hallucinogen exposure are thought to involve transcriptional alterations in specific effector immediate early genes. The immediate early gene, activity regulated cytoskeletal-associated protein (Arc), is important for both activity and experience dependent plasticity. We sought to examine whether trophic factor signalling through brain-derived neurotrophic factor (BDNF) contributes to the neocortical regulation of Arc mRNA in response to distinct stimuli such as immobilization stress and the hallucinogen 2,5-dimethoxy-4-iodoamphetamine (DOI). Acute exposure to either immobilization stress or DOI induced Arc mRNA levels within the neocortex. BDNF infusion into the neocortex led to a robust up-regulation of local Arc transcript expression. Further, baseline Arc mRNA expression in the neocortex was significantly decreased in inducible BDNF knockout mice with an adult-onset, forebrain specific BDNF loss. The induction of Arc mRNA levels in response to both acute immobilization stress or a single administration of DOI was significantly attenuated in the inducible BDNF knockout mice. Taken together, our results implicate trophic factor signalling through BDNF in the regulation of cortical Arc mRNA expression, both under baseline conditions and following stress and hallucinogen exposure. These findings suggest the possibility that the regulation of Arc expression via BDNF provides a molecular substrate for the structural and synaptic plasticity observed following stimuli such as stress and hallucinogens.

Regulation of Embryonic and Postnatal Development by the CSF-1 Receptor

PubMed Central

Chitu, Violeta; Stanley, E. Richard

2017-01-01

Macrophages are found in all tissues and regulate tissue morphogenesis during development through trophic and scavenger functions. The colony stimulating factor-1 (CSF-1) receptor (CSF-1R) is the major regulator of tissue macrophage development and maintenance. In combination with receptor activator of nuclear factor κB (RANK), the CSF-1R also regulates the differentiation of the bone-resorbing osteoclast and controls bone remodeling during embryonic and early postnatal development. CSF-1R-regulated macrophages play trophic and remodeling roles in development. Outside the mononuclear phagocytic system, the CSF-1R directly regulates neuronal survival and differentiation, the development of intestinal Paneth cells and of preimplantation embryos, as well as trophoblast innate immune function. Consistent with the pleiotropic roles of the receptor during development, CSF-1R deficiency in most mouse strains causes embryonic or perinatal death and the surviving mice exhibit multiple developmental and functional deficits. The CSF-1R is activated by two dimeric glycoprotein ligands, CSF-1, and interleukin-34 (IL-34). Homozygous Csf1-null mutations phenocopy most of the deficits of Csf1r-null mice. In contrast, Il34-null mice have no gross phenotype, except for decreased numbers of Langerhans cells and microglia, indicating that CSF-1 plays the major developmental role. Homozygous inactivating mutations of the Csf1r or its ligands have not been reported in man. However, heterozygous inactivating mutations in the Csf1r lead to a dominantly inherited adult-onset progressive dementia, highlighting the importance of CSF-1R signaling in the brain. PMID:28236968

Regulation of Embryonic and Postnatal Development by the CSF-1 Receptor.

PubMed

Chitu, Violeta; Stanley, E Richard

2017-01-01

Macrophages are found in all tissues and regulate tissue morphogenesis during development through trophic and scavenger functions. The colony stimulating factor-1 (CSF-1) receptor (CSF-1R) is the major regulator of tissue macrophage development and maintenance. In combination with receptor activator of nuclear factor κB (RANK), the CSF-1R also regulates the differentiation of the bone-resorbing osteoclast and controls bone remodeling during embryonic and early postnatal development. CSF-1R-regulated macrophages play trophic and remodeling roles in development. Outside the mononuclear phagocytic system, the CSF-1R directly regulates neuronal survival and differentiation, the development of intestinal Paneth cells and of preimplantation embryos, as well as trophoblast innate immune function. Consistent with the pleiotropic roles of the receptor during development, CSF-1R deficiency in most mouse strains causes embryonic or perinatal death and the surviving mice exhibit multiple developmental and functional deficits. The CSF-1R is activated by two dimeric glycoprotein ligands, CSF-1, and interleukin-34 (IL-34). Homozygous Csf1-null mutations phenocopy most of the deficits of Csf1r-null mice. In contrast, Il34-null mice have no gross phenotype, except for decreased numbers of Langerhans cells and microglia, indicating that CSF-1 plays the major developmental role. Homozygous inactivating mutations of the Csf1r or its ligands have not been reported in man. However, heterozygous inactivating mutations in the Csf1r lead to a dominantly inherited adult-onset progressive dementia, highlighting the importance of CSF-1R signaling in the brain. © 2017 Elsevier Inc. All rights reserved.

Estimates of long-term water total phosphorus (TP) concentrations in three large shallow lakes in the Yangtze River basin, China.

PubMed

Wu, Pan; Qin, Boqiang; Yu, Ge

2016-03-01

The shallow lakes in the eastern China developed on alluvial plains with high-nutrient sediments, and most overflow into the Yangtze River with short hydraulic residence times, whereas they become eutrophic over long time periods. Assuming strong responses to hydrogeological changes in the basin, we attempted to determine the dynamic eutrophication history of these lakes. Although evaluation models for internal total phosphorus (TP) loading are widely used for deep lakes in Europe and North America, the accuracy of these models for shallow lakes that have smaller water volumes controlled by the geometrical morphology and greater basin area of alluvial plains is unknown. To describe the magnitude of changes in velocity of trophic state for the studied shallow lakes, we first evaluated the P retention model in relation to the major forces driving lake morphology, basin climate, and external discharge and then used the model to estimate changes in TP in three large shallow lakes (Taihu, Chao, and Poyang) over 60 years (1950-2009 AD). The observed levels of TP were verified against the relative error of the three lakes (<6.43 %) and Nash-Sutcliffe coefficients (0.67-0.75). The results showed that the predicted TP concentrations largely increased with hydraulic residence time, especially in extreme drought years, with a generally rising trend in trophic status. The simulated trophic state index showed that lakes Taihu and Poyang became eutrophic in the 1990s, whereas Lake Chao became eutrophic in the 1980s; lakes Taihu and Chao ultimately became hypereutrophic in the 2000s. The analysis suggested that the tropic status of the shallow lakes was affected by both the hydroclimate and geological sedimentation of the Yangtze River basin. This work will contribute to the development of an internal P loading model for further evaluating trophic states.

Investigation on trophic state index by artificial neural networks (case study: Dez Dam of Iran)

NASA Astrophysics Data System (ADS)

Saghi, H.; Karimi, L.; Javid, A. H.

2015-06-01

Dam construction and surface runoff control is one of the most common approaches for water-needs supply of human societies. However, the increasing development of social activities and hence the subsequent increase in environmental pollutants leads to deterioration of water quality in dam reservoirs and eutrophication process could be intensified. So, the water quality of reservoirs is now one of the key factors in operation and water quality management of reservoirs. Hence, maintaining the quality of the stored water and identification and examination of changes along time has been a constant concern of humans that involves the water authorities. Traditionally, empirical trophic state indices of dam reservoirs often defined based on changes in concentration of effective factors (nutrients) and its consequences (increase in chlorophyll a), have been used as an efficient tool in the definition of dam reservoirs quality. In recent years, modeling techniques such as artificial neural networks have enhanced the prediction capability and the accuracy of these studies. In this study, artificial neural networks have been applied to analyze eutrophication process in the Dez Dam reservoir in Iran. In this paper, feed forward neural network with one input layer, one hidden layer and one output layer was applied using MATLAB neural network toolbox for trophic state index (TSI) analysis in the Dez Dam reservoir. The input data of this network are effective parameters in the eutrophication: nitrogen cycle parameters and phosphorous cycle parameters and parameters that will be changed by eutrophication: Chl a, SD, DO and the output data is TSI. Based on the results from estimation of modified Carlson trophic state index, Dez Dam reservoir is considered to be eutrophic in the early July to mid-November and would be mesotrophic with decrease in temperature. Therefore, a decrease in water quality of the dam reservoir during the warm seasons is expectable. The results indicated that artificial neural network (ANN) is a suitable tool for quality modeling of reservoir of dam and increment and decrement of nutrients in trend of eutrophication. Therefore, ANN is a suitable tool for quality modeling of reservoir of dam.

Is brood parasitism related to host nestling diet and nutrition?

Treesearch

Zachary S. Ladin; Vincent D' Amico; Deb P. Jaisi; W. Gregory Shriver

2015-01-01

Food and nutrient limitation can have negative effects on survival, fecundity, and lifetime fitness of individuals, which can ultimately limit populations. Changes in trophic dynamics and diet patterns, affected by anthropogenic environmental and landscape change, are poorly understood yet may play an important role in population regulation. We determined diets of Wood...

Age-Dependent Deficits in Fear Learning in Heterozygous BDNF Knock-Out Mice

ERIC Educational Resources Information Center

Endres, Thomas; Lessmann, Volkmar

2012-01-01

Beyond its trophic function, the neurotrophin BDNF (brain-derived neurotrophic factor) is well known to crucially mediate synaptic plasticity and memory formation. Whereas recent studies suggested that acute BDNF/TrkB signaling regulates amygdala-dependent fear learning, no impairments of cued fear learning were reported in heterozygous BDNF…

Suppression of soybean aphid by generalist predators results in a trophic cascade in soybeans.

PubMed

Costamagna, Alejandro C; Landis, Douglas A; Difonzo, Christina D

2007-03-01

Top-down regulation of herbivores in terrestrial ecosystems is pervasive and can lead to trophic cascades that release plants from herbivory. Due to their relatively simplified food webs, agroecosystems may be particularly prone to trophic cascades, a rationale that underlies biological control. However, theoretical and empirical studies show that, within multiple enemy assemblages, intraguild predation (IGP) may lead to a disruption of top-down control by predators. We conducted a factorial field study to test the separate and combined effects of predators and parasitoids in a system with asymmetric IGP. Specifically we combined ambient levels of generalist predators (mainly Coccinellidae) of the soybean aphid, Aphis glycines Matsumura, with controlled releases of the native parasitoid Lysiphlebus testaceipes (Cresson) and measured their impact on aphid population growth and soybean biomass and yield. We found that generalist predators provided strong, season-long aphid suppression, which resulted in a trophic cascade that doubled soybean biomass and yield. However, contrary to our expectations, L. testaceipes provided minor aphid suppression and only when predators were excluded, which resulted in nonadditive effects when both groups were combined. We found direct and indirect evidence of IGP, but because percentage parasitism did not differ between predator exclusion and ambient predator treatments, we concluded that IGP did not disrupt parasitism during this study. Our results support theoretical predictions that intraguild predators which also provide strong herbivore suppression do not disrupt top-down control of herbivores.

A Pro-Nerve Growth Factor (proNGF) and NGF Binding Protein, α2-Macroglobulin, Differentially Regulates p75 and TrkA Receptors and Is Relevant to Neurodegeneration Ex Vivo and In Vivo

PubMed Central

Barcelona, Pablo F.

2015-01-01

Nerve growth factor (NGF) is generated from a precursor, proNGF, that is proteolytically processed. NGF preferentially binds a trophic tyrosine kinase receptor, TrkA, while proNGF binds a neurotrophin receptor (NTR), p75NTR, that can have neurotoxic activity. Previously, we along with others showed that the soluble protein α2-macroglobulin (α2M) is neurotoxic. Toxicity is due in part to α2M binding to NGF and inhibiting trophic activity, presumably by preventing NGF binding to TrkA. However, the mechanisms remained unclear. Here, we show ex vivo and in vivo three mechanisms for α2M neurotoxicity. First, unexpectedly the α2M-NGF complexes do bind TrkA receptors but do not induce TrkA dimerization or activation, resulting in deficient trophic support. Second, α2M makes stable complexes with proNGF, conveying resistance to proteolysis that results in more proNGF and less NGF. Third, α2M-proNGF complexes bind p75NTR and are more potent agonists than free proNGF, inducing tumor necrosis factor alpha (TNF-α) production. Hence, α2M regulates proNGF/p75NTR positively and mature NGF/TrkA negatively, causing neuronal death ex vivo. These three mechanisms are operative in vivo, and α2M causes neurodegeneration in a p75NTR- and proNGF-dependent manner. α2M could be exploited as a therapeutic target, or as a modifier of neurotrophin signals. PMID:26217017

High-resolution food webs based on nitrogen isotopic composition of amino acids

PubMed Central

Chikaraishi, Yoshito; Steffan, Shawn A; Ogawa, Nanako O; Ishikawa, Naoto F; Sasaki, Yoko; Tsuchiya, Masashi; Ohkouchi, Naohiko

2014-01-01

Food webs are known to have myriad trophic links between resource and consumer species. While herbivores have well-understood trophic tendencies, the difficulties associated with characterizing the trophic positions of higher-order consumers have remained a major problem in food web ecology. To better understand trophic linkages in food webs, analysis of the stable nitrogen isotopic composition of amino acids has been introduced as a potential means of providing accurate trophic position estimates. In the present study, we employ this method to estimate the trophic positions of 200 free-roaming organisms, representing 39 species in coastal marine (a stony shore) and 38 species in terrestrial (a fruit farm) environments. Based on the trophic positions from the isotopic composition of amino acids, we are able to resolve the trophic structure of these complex food webs. Our approach reveals a high degree of trophic omnivory (i.e., noninteger trophic positions) among carnivorous species such as marine fish and terrestrial hornets.This information not only clarifies the trophic tendencies of species within their respective communities, but also suggests that trophic omnivory may be common in these webs. PMID:25360278

Pleiotrophin over-expression provides trophic support to dopaminergic neurons in parkinsonian rats.

PubMed

Taravini, Irene Re; Chertoff, Mariela; Cafferata, Eduardo G; Courty, José; Murer, Mario G; Pitossi, Fernando J; Gershanik, Oscar S

2011-06-07

Pleiotrophin is known to promote the survival and differentiation of dopaminergic neurons in vitro and is up-regulated in the substantia nigra of Parkinson's disease patients. To establish whether pleiotrophin has a trophic effect on nigrostriatal dopaminergic neurons in vivo, we injected a recombinant adenovirus expressing pleiotrophin in the substantia nigra of 6-hydroxydopamine lesioned rats. The viral vector induced pleiotrophin over-expression by astrocytes in the substantia nigra pars compacta, without modifying endogenous neuronal expression. The percentage of tyrosine hydroxylase-immunoreactive cells as well as the area of their projections in the lesioned striatum was higher in pleiotrophin-treated animals than in controls. These results indicate that pleiotrophin over-expression partially rescues tyrosine hydroxylase-immunoreactive cell bodies and terminals of dopaminergic neurons undergoing 6-hydroxydopamine-induced degeneration.

Variation of mercury in fish from Massachusetts lakes based on ecoregion and lake trophic status

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rose, J.; Hutcheson, M.; West, C.R.

1995-12-31

Twenty-four of the state`s least-impacted waterbodies were sampled for sediment, water, physical characteristics and 3 species of fish to determine the extent of, and patterns of variation in, mercury contamination. Sampling effort was apportioned among three different ecological subregions of the state, as defined by EPA, and among lakes of differing trophic status. The authors sought to partition the variance to discover if these broadly defined concepts are suitable predictors of mercury levels in fish. Mean fish mercury was 0.14 ppm wet weight in samples of 168 of the bottom feeding brown bullheads (Ameriurus nebulosus) (range = 0.01--0.79 ppm); 0.3more » ppm in 199 of the omnivorous yellow perch (Perca flavescens) (range = 0.01--0.75 ppm); and 0.4 ppm in samples of 152 of the predaceous largemouth bass (Micropterus salmoides) (range = 0.05--1.1 ppm). Multivariate statistics are employed to determine how mercury concentrations in fish correlate with sediment chemistry, water chemistry, fish trophic status, fish size and age, lake and watershed size, the presence and extent of wetlands in the watershed, and physical characteristics of the lake. The survey design complements ongoing efforts begun in 1983 to test fish in a variety of waters, from which emanated fish advisories for impacted rivers and lakes. The study defines a baseline for fish contamination in Massachusetts lakes and ponds that serves as a template for public health decisions regarding fish consumption.« less

Uptake Kinetics and Trophic Transfer of Tungsten from Cabbage to a Herbivorous Animal Model

DOE PAGES

Lindsay, James H.; Kennedy, Alan J.; Seiter-Moser, Jennifer M.; ...

2017-10-20

This paper builds on previous studies on military-relevant tungsten (W) to more thoroughly explore environmental pathways and bioaccumulation kinetics during direct soil exposure versus trophic transfer and elucidate its relative accumulation and speciation in different snail organs. The modeled steady-state concentration and bioaccumulation factor (BAF) of W from soil into cabbage were 302 mg/kg and 0.55, respectively. Steady-state concentrations (34 mg/kg) and BAF values (0.05) obtained for the snail directly exposed to contaminated soil were lower than trophic transfer by consumption of W-contaminated cabbage (tissue concentration of 86 mg/kg; BAF of 0.36). Thus, consumption of contaminated food is the mostmore » important pathway for W mobility in this food chain. The highest concentrations of W compartmentalization were in the snail’s hepatopancreas based on wet chemistry and synchrotron-based investigations. Chemical speciation via inductively couple plasma mass spectrometry showed a higher degree of polytungstate partitioning in the hepatopancreas relative to the rest of the body. Based on synchrotron analysis, W was incorporated into the shell matrix during exposure, particularly during the regeneration of damaged shell. Finally, this offers the potential for application of the shell as a longer-term biomonitoring and forensics tool for historic exposure.« less

Uptake Kinetics and Trophic Transfer of Tungsten from Cabbage to a Herbivorous Animal Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindsay, James H.; Kennedy, Alan J.; Seiter-Moser, Jennifer M.

This paper builds on previous studies on military-relevant tungsten (W) to more thoroughly explore environmental pathways and bioaccumulation kinetics during direct soil exposure versus trophic transfer and elucidate its relative accumulation and speciation in different snail organs. The modeled steady-state concentration and bioaccumulation factor (BAF) of W from soil into cabbage were 302 mg/kg and 0.55, respectively. Steady-state concentrations (34 mg/kg) and BAF values (0.05) obtained for the snail directly exposed to contaminated soil were lower than trophic transfer by consumption of W-contaminated cabbage (tissue concentration of 86 mg/kg; BAF of 0.36). Thus, consumption of contaminated food is the mostmore » important pathway for W mobility in this food chain. The highest concentrations of W compartmentalization were in the snail’s hepatopancreas based on wet chemistry and synchrotron-based investigations. Chemical speciation via inductively couple plasma mass spectrometry showed a higher degree of polytungstate partitioning in the hepatopancreas relative to the rest of the body. Based on synchrotron analysis, W was incorporated into the shell matrix during exposure, particularly during the regeneration of damaged shell. Finally, this offers the potential for application of the shell as a longer-term biomonitoring and forensics tool for historic exposure.« less

Prey state shapes the effects of temporal variation in predation risk

PubMed Central

Matassa, Catherine M.; Trussell, Geoffrey C.

2014-01-01

The ecological impacts of predation risk are influenced by how prey allocate foraging effort across periods of safety and danger. Foraging decisions depend on current danger, but also on the larger temporal, spatial or energetic context in which prey manage their risks of predation and starvation. Using a rocky intertidal food chain, we examined the responses of starved and fed prey (Nucella lapillus dogwhelks) to different temporal patterns of risk from predatory crabs (Carcinus maenas). Prey foraging activity declined during periods of danger, but as dangerous periods became longer, prey state altered the magnitude of risk effects on prey foraging and growth, with likely consequences for community structure (trait-mediated indirect effects on basal resources, Mytilus edulis mussels), prey fitness and trophic energy transfer. Because risk is inherently variable over time and space, our results suggest that non-consumptive predator effects may be most pronounced in productive systems where prey can build energy reserves during periods of safety and then burn these reserves as ‘trophic heat’ during extended periods of danger. Understanding the interaction between behavioural (energy gain) and physiological (energy use) responses to risk may illuminate the context dependency of trait-mediated trophic cascades and help explain variation in food chain length. PMID:25339716

Are red-tailed hawks and great horned owls diurnal-nocturnal dietary counterparts?

USGS Publications Warehouse

Marti, C.D.; Kochert, Michael N.

1995-01-01

Red-tailed Hawks (Buteo jamaicensis) and Great Homed Owls (Bubo virginianus)are common in North America where they occupy a wide range of habitats, often sympatrically. The two species are similar in size and have been portrayed as ecological counterparts, eating the same prey by day and night. We tested the trophic similarity of the two species by comparing published dietary data from across the United States. Both species ate primarily mammals and birds, and mean proportions of those two prey types did not differ significantly between diets of the two raptors. Red-tailed Hawks ate significantly more reptiles, and Great Homed Owls significantly more invertebrates. Dietary diversity was not significantly different at the level of prey taxonomic class, and diet overlap between the two species averaged 91%. At the prey species level, dietary overlap averaged only 50%, and at that level Red-tailed Hawk dietary diversity was significantly greater than that of Great Horned Owls. Mean prey mass of Red-tailed Hawks was significantly greater than that of Great Homed Owls. Populations of the two species in the western United States differed trophically more than did eastern populations. We conclude that, although the two species are generalist predators, they take largely different prey species in the same localities resulting in distinctive trophic characteristics.

Aquatic ecosystem health and trophic status classification of the Bitter Lakes along the main connecting link between the Red Sea and the Mediterranean.

PubMed

El-Serehy, Hamed A; Abdallah, Hala S; Al-Misned, Fahad A; Irshad, Rizwan; Al-Farraj, Saleh A; Almalki, Esam S

2018-02-01

The Bitter Lakes are the most significant water bodies of the Suez Canal, comprising 85% of the water volume, but spreading over only 24% of the length of the canal. The present study aims at investigation of the trophic status of the Bitter Lakes employing various trophic state indices, biotic and abiotic parameters, thus reporting the health of the Lake ecosystem according to the internationally accepted classification criteria's. The composition and abundance of phytoplankton with a dominance of diatoms and a decreased population density of 4315-7376 ind. l -1 reflect the oligotrophic nature of this water body. The intense growth of diatoms in the Bitter Lakes depends on silicate availability, in addition to nitrate and phosphate. If the trophic state index (TSI) is applied to the lakes under study it records that the Bitter Lakes have an index under 40. Moreover, in the total chlorophyll- a measurements of 0.35-0.96 µg l -1 there are more indicative of little algal biomass and lower biological productivity. At 0.76-2.3 µg l -1 , meanwhile, the low quantity of Phosphorus is a further measure of low biological productivity. In the Bitter Lakes, TN/TP ratios are high and recorded 147.4, and 184.7 for minimum and maximum ratios, respectively. These values indicate that in Bitter lakes, the limiting nutrient is phosphorus and confirm the oligotrophic status of the Bitter Lakes. The latter conclusion is supported by Secchi disc water clarity measurements, showing that light can penetrate, and thus algae can photosynthesize, as deep as >13 m. This study, therefore, showed that the Bitter Lakes of the Suez Canal exhibit oligotrophic conditions with clear water, low productivity and with no algal blooming.

The Herbivore-Induced Plant Volatiles Methyl Salicylate and Menthol Positively affect Growth and Pathogenicity of Entomopathogenic Fungi

PubMed Central

Lin, Yongwen; Qasim, Muhammad; Hussain, Mubasher; Akutse, Komivi Senyo; Avery, Pasco Bruce; Dash, Chandra Kanta; Wang, Liande

2017-01-01

Some herbivore-induced-plant volatiles (HIPVs) compounds are vital for the functioning of an ecosystem, by triggering multi-trophic interactions for natural enemies, plants and herbivores. However, the effect of these chemicals, which play a crucial role in regulating the multi-trophic interactions between plant-herbivore-entomopathogenic fungi, is still unknown. To fill this scientific gap, we therefore investigated how these chemicals influence the entomopathogenic fungi growth and efficacy. In this study, Lipaphis erysimi induced Arabidopsis thaliana HIPVs were collected using headspace system and detected with GC-MS, and then analyzed the effects of these HIPVs chemicals on Lecanicillium lecanii strain V3450. We found that the HIPVs menthol and methyl salicylate at 1 and 10 nmol·ml−1 improved many performance aspects of the fungus, such as germination, sporulation, appressorial formation as well as its pathogenicity and virulence. These findings are not only important for understanding the multi-trophic interactions in an ecosystem, but also would contribute for developing new and easier procedures for conidial mass production as well as improve the pathogenicity and virulence of entomopathogenic fungi in biological pest management strategies. PMID:28079180

The Herbivore-Induced Plant Volatiles Methyl Salicylate and Menthol Positively affect Growth and Pathogenicity of Entomopathogenic Fungi

NASA Astrophysics Data System (ADS)

Lin, Yongwen; Qasim, Muhammad; Hussain, Mubasher; Akutse, Komivi Senyo; Avery, Pasco Bruce; Dash, Chandra Kanta; Wang, Liande

2017-01-01

Some herbivore-induced-plant volatiles (HIPVs) compounds are vital for the functioning of an ecosystem, by triggering multi-trophic interactions for natural enemies, plants and herbivores. However, the effect of these chemicals, which play a crucial role in regulating the multi-trophic interactions between plant-herbivore-entomopathogenic fungi, is still unknown. To fill this scientific gap, we therefore investigated how these chemicals influence the entomopathogenic fungi growth and efficacy. In this study, Lipaphis erysimi induced Arabidopsis thaliana HIPVs were collected using headspace system and detected with GC-MS, and then analyzed the effects of these HIPVs chemicals on Lecanicillium lecanii strain V3450. We found that the HIPVs menthol and methyl salicylate at 1 and 10 nmol·ml-1 improved many performance aspects of the fungus, such as germination, sporulation, appressorial formation as well as its pathogenicity and virulence. These findings are not only important for understanding the multi-trophic interactions in an ecosystem, but also would contribute for developing new and easier procedures for conidial mass production as well as improve the pathogenicity and virulence of entomopathogenic fungi in biological pest management strategies.

The Herbivore-Induced Plant Volatiles Methyl Salicylate and Menthol Positively affect Growth and Pathogenicity of Entomopathogenic Fungi.

PubMed

Lin, Yongwen; Qasim, Muhammad; Hussain, Mubasher; Akutse, Komivi Senyo; Avery, Pasco Bruce; Dash, Chandra Kanta; Wang, Liande

2017-01-12

Some herbivore-induced-plant volatiles (HIPVs) compounds are vital for the functioning of an ecosystem, by triggering multi-trophic interactions for natural enemies, plants and herbivores. However, the effect of these chemicals, which play a crucial role in regulating the multi-trophic interactions between plant-herbivore-entomopathogenic fungi, is still unknown. To fill this scientific gap, we therefore investigated how these chemicals influence the entomopathogenic fungi growth and efficacy. In this study, Lipaphis erysimi induced Arabidopsis thaliana HIPVs were collected using headspace system and detected with GC-MS, and then analyzed the effects of these HIPVs chemicals on Lecanicillium lecanii strain V3450. We found that the HIPVs menthol and methyl salicylate at 1 and 10 nmol·ml -1 improved many performance aspects of the fungus, such as germination, sporulation, appressorial formation as well as its pathogenicity and virulence. These findings are not only important for understanding the multi-trophic interactions in an ecosystem, but also would contribute for developing new and easier procedures for conidial mass production as well as improve the pathogenicity and virulence of entomopathogenic fungi in biological pest management strategies.

Northward range extension of an endemic soil decomposer with a distinct trophic position.

PubMed

Melody, Carol; Schmidt, Olaf

2012-12-23

Ecological niche theory asserts that invading species become established only if introduced propagules survive stochastic mortality and can exploit resources unconsumed by resident species. Because their transportation is not controlled by plant health or biosecurity regulations, soil macrofauna decomposers, including earthworms are probably introduced frequently into non-native soils. Yet even with climatic change, exotic earthworm species from southern Europe have not been reported to become established in previously glaciated areas of northern Europe that already have trophically differentiated earthworm communities of 'peregrine' species. We discovered established populations of the earthworm Prosellodrilus amplisetosus (Lumbricidae), a member of a genus endemic to southern France, in six habitats of an urban farm in Dublin, Ireland, about 1000 km north of the genus's endemic range. Not only was P. amplisetosus the dominant endogeic (geophagous) earthworm species in two habitats, it also occupied a significantly different trophic position from the resident species, as evinced by stable isotope ratio analysis. The suggested ability of this non-native species to feed on and assimilate isotopically more enriched soil carbon (C) and nitrogen fractions that are inaccessible to resident species portends potential implications of decomposer range expansions for soil functioning including C sequestration.

The water-quality monitoring program for the Baltimore reservoir system, 1981-2007—Description, review and evaluation, and framework integration for enhanced monitoring

USGS Publications Warehouse

Koterba, Michael T.; Waldron, Marcus C.; Kraus, Tamara E.C.

2011-01-01

The City of Baltimore, Maryland, and parts of five surrounding counties obtain their water from Loch Raven and Liberty Reservoirs. A third reservoir, Prettyboy, is used to resupply Loch Raven Reservoir. Management of the watershed conditions for each reservoir is a shared responsibility by agreement among City, County, and State jurisdictions. The most recent (2005) Baltimore Reservoir Watershed Management Agreement (RWMA) called for continued and improved water-quality monitoring in the reservoirs and selected watershed tributaries. The U.S. Geological Survey (USGS) conducted a retrospective review of the effectiveness of monitoring data obtained and analyzed by the RWMA jurisdictions from 1981 through 2007 to help identify possible improvements in the monitoring program to address RWMA water-quality concerns. Long-term water-quality concerns include eutrophication and sedimentation in the reservoirs, and elevated concentrations of (a) nutrients (nitrogen and phosphorus) being transported from the major tributaries to the reservoirs, (b) iron and manganese released from reservoir bed sediments during periods of deep-water anoxia, (c) mercury in higher trophic order game fish in the reservoirs, and (d) bacteria in selected reservoir watershed tributaries. Emerging concerns include elevated concentrations of sodium, chloride, and disinfection by-products (DBPs) in the drinking water from both supply reservoirs. Climate change and variability also could be emerging concerns, affecting seasonal patterns, annual trends, and drought occurrence, which historically have led to declines in reservoir water quality. Monitoring data increasingly have been used to support the development of water-quality models. The most recent (2006) modeling helped establish an annual sediment Total Maximum Daily Load to Loch Raven Reservoir, and instantaneous and 30-day moving average water-quality endpoints for chlorophyll-a (chl-a) and dissolved oxygen (DO) in Loch Raven and Prettyboy Reservoirs. Modelers cited limitations in data, including too few years with sufficient stormflow data, and (or) a lack of (readily available) data, for selected tributary and reservoir hydrodynamic, water-quality, and biotic conditions. Reservoir monitoring also is too infrequent to adequately address the above water-quality endpoints. Monitoring data also have been effectively used to generally describe trophic states, changes in trophic state or conditions related to trophic state, and in selected cases, trends in water-quality or biotic parameters that reflect RWMA water-quality concerns. Limitations occur in the collection, aggregation, analyses, and (or) archival of monitoring data in relation to most RWMA water-quality concerns. Trophic, including eutrophic, conditions have been broadly described for each reservoir in terms of phytoplankton production, and variations in production related to typical seasonal patterns in the concentration of DO, and hypoxic to anoxic conditions, where the latter have led to elevated concentrations of iron and manganese in reservoir and supply waters. Trend analyses for the period 1981-2004 have shown apparent declines in production (algal counts and possibly chl-a). The low frequency of phytoplankton data collection (monthly or bimonthly, depending on the reservoir), however, limits the development of a model to quantitatively describe and relate temporal variations in phytoplankton production including seasonal succession to changes in trophic states or other reservoir water-quality or biotic conditions. Extensive monitoring for nutrients, which, in excessive amounts, cause eutrophic conditions, has been conducted in the watershed tributaries and reservoirs. Data analyses (1980-90s) have (a) identified seasonal patterns in concentrations, (b) characterized loads from (non)point sources, and (c) shown that different seasonal patterns and trends in nutrient concentrations occur between watershed tributaries and downstream reservoir

TAM receptors support neural stem cell survival, proliferation and neuronal differentiation.

PubMed

Ji, Rui; Meng, Lingbin; Jiang, Xin; Cvm, Naresh Kumar; Ding, Jixiang; Li, Qiutang; Lu, Qingxian

2014-01-01

Tyro3, Axl and Mertk (TAM) receptor tyrosine kinases play multiple functional roles by either providing intrinsic trophic support for cell growth or regulating the expression of target genes that are important in the homeostatic regulation of immune responses. TAM receptors have been shown to regulate adult hippocampal neurogenesis by negatively regulation of glial cell activation in central nervous system (CNS). In the present study, we further demonstrated that all three TAM receptors were expressed by cultured primary neural stem cells (NSCs) and played a direct growth trophic role in NSCs proliferation, neuronal differentiation and survival. The cultured primary NSCs lacking TAM receptors exhibited slower growth, reduced proliferation and increased apoptosis as shown by decreased BrdU incorporation and increased TUNEL labeling, than those from the WT NSCs. In addition, the neuronal differentiation and maturation of the mutant NSCs were impeded, as characterized by less neuronal differentiation (β-tubulin III+) and neurite outgrowth than their WT counterparts. To elucidate the underlying mechanism that the TAM receptors play on the differentiating NSCs, we examined the expression profile of neurotrophins and their receptors by real-time qPCR on the total RNAs from hippocampus and primary NSCs; and found that the TKO NSC showed a significant reduction in the expression of both nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), but accompanied by compensational increases in the expression of the TrkA, TrkB, TrkC and p75 receptors. These results suggest that TAM receptors support NSCs survival, proliferation and differentiation by regulating expression of neurotrophins, especially the NGF.

Effects of ecological interactions and environmental conditions on community dynamics in an estuarine ecosystem

NASA Astrophysics Data System (ADS)

Liu, H.; Minello, T.; Sutton, G.

2016-02-01

Coastal marine ecosystems are both productive and vulnerable to human and natural stressors. Examining the relative importance of fishing, environmental variability, and habitat alteration on ecosystem dynamics is challenging. Intensive harvest and habitat loss have resulted in widespread concerns related to declines in fisheries production, but causal mechanisms are rarely clear. In this study, we modeled trophic dynamics in Galveston Bay, Texas, using fishery-independent catch data for blue crab, shrimp, red drum, Atlantic croaker and spotted seatrout along with habitat information collected by the Texas Parks and Wildlife Department during 1984 - 2014. We developed a multispecies state-space model to examine ecological interactions and partition the relative effects of trophic interactions and environmental conditions on the community dynamics. Preliminary results showed the importance of salinity, density-dependence, and trophic interactions. We are continuing to explore these results from a perspective of fish community compensatory responses to exploitation, reflecting both direct and indirect effects of harvesting under the influence of climate variability.

Trophic flexibility and the persistence of understory birds in intensively logged rainforest.

PubMed

Edwards, David P; Woodcock, Paul; Newton, Rob J; Edwards, Felicity A; Andrews, David J R; Docherty, Teegan D S; Mitchell, Simon L; Ota, Takahiro; Benedick, Suzan; Bottrell, Simon H; Hamer, Keith C

2013-10-01

Effects of logging on species composition in tropical rainforests are well known but may fail to reveal key changes in species interactions. We used nitrogen stable-isotope analysis of 73 species of understory birds to quantify trophic responses to repeated intensive logging of rainforest in northern Borneo and to test 4 hypotheses: logging has significant effects on trophic positions and trophic-niche widths of species, and the persistence of species in degraded forest is related to their trophic positions and trophic-niche widths in primary forest. Species fed from higher up the food chain and had narrower trophic-niche widths in degraded forest. Species with narrow trophic-niche widths in primary forest were less likely to persist after logging, a result that indicates a higher vulnerability of dietary specialists to local extinction following habitat disturbance. Persistence of species in degraded forest was not related to a species' trophic position. These results indicate changes in trophic organization that were not apparent from changes in species composition and highlight the importance of focusing on trophic flexibility over the prevailing emphasis on membership of static feeding guilds. Our results thus support the notion that alterations to trophic organization and interactions within tropical forests may be a pervasive and functionally important hidden effect of forest degradation. © 2013 Society for Conservation Biology.

Taxa-specific eco-sensitivity in relation to phytoplankton bloom stability and ecologically relevant lake state

NASA Astrophysics Data System (ADS)

Napiórkowska-Krzebietke, Agnieszka; Dunalska, Julita A.; Zębek, Elżbieta

2017-05-01

Phytoplankton (including plant-like, animal-like algae and Cyanobacteria) blooms have recently become a serious global threat to the sustenance of ecosystems, to human and animal health and to economy. This study focused on the composition and stability of blooms as well as their taxa-specific ecological sensitivity to the main causal factors (especially phosphorus and nitrogen) in degraded urban lakes. The analyzed lakes were assessed with respect to the trophic state as well as ecological status. Total phytoplankton biomass (ranging from 1.5 to 181.3 mg dm-3) was typical of blooms of different intensity, which can appear during a whole growing season but are the most severe in early or late summer. Our results suggested that steady-state and non-steady-state bloom assemblages including mono-, bi- and multi-species or heterogeneous blooms may occur in urban lakes. The most intense blooms were formed by the genera of Cyanobacteria: Microcystis, Limnothrix, Pseudanabaena, Planktothrix, Bacillariophyta: Cyclotella and Dinophyta mainly Ceratium and Peridinium. Considering the sensitivity of phytoplankton assemblages, a new eco-sensitivity factor was proposed (E-SF), based on the concept of Phytoplankton Trophic Index composed of trophic scores of phytoplankton taxa along the eutrophication gradient. The E-SF values of 0.5, 1.3, 6.7 and 15.1 were recognized in lakes having a high, good, moderate or poor ecological status, respectively. For lake restoration, each type of bloom should be considered separately because of different sensitivities of taxa and relationships with environmental variables. Proper recognition of the taxa-specific response to abiotic (especially to N and P enrichment) and biotic factors could have significant implications for further water protection and management.

Impacts of Intensive Logging on the Trophic Organisation of Ant Communities in a Biodiversity Hotspot

PubMed Central

Woodcock, Paul; Edwards, David P.; Newton, Rob J.; Vun Khen, Chey; Bottrell, Simon H.; Hamer, Keith C.

2013-01-01

Trophic organisation defines the flow of energy through ecosystems and is a key component of community structure. Widespread and intensifying anthropogenic disturbance threatens to disrupt trophic organisation by altering species composition and relative abundances and by driving shifts in the trophic ecology of species that persist in disturbed ecosystems. We examined how intensive disturbance caused by selective logging affects trophic organisation in the biodiversity hotspot of Sabah, Borneo. Using stable nitrogen isotopes, we quantified the positions in the food web of 159 leaf-litter ant species in unlogged and logged rainforest and tested four predictions: (i) there is a negative relationship between the trophic position of a species in unlogged forest and its change in abundance following logging, (ii) the trophic positions of species are altered by logging, (iii) disturbance alters the frequency distribution of trophic positions within the ant assemblage, and (iv) disturbance reduces food chain length. We found that ant abundance was 30% lower in logged forest than in unlogged forest but changes in abundance of individual species were not related to trophic position, providing no support for prediction (i). However, trophic positions of individual species were significantly higher in logged forest, supporting prediction (ii). Consequently, the frequency distribution of trophic positions differed significantly between unlogged and logged forest, supporting prediction (iii), and food chains were 0.2 trophic levels longer in logged forest, the opposite of prediction (iv). Our results demonstrate that disturbance can alter trophic organisation even without trophically-biased changes in community composition. Nonetheless, the absence of any reduction in food chain length in logged forest suggests that species-rich arthropod food webs do not experience trophic downgrading or a related collapse in trophic organisation despite the disturbance caused by logging. These food webs appear able to bend without breaking in the face of some forms of anthropogenic disturbance. PMID:23593302

Impacts of intensive logging on the trophic organisation of ant communities in a biodiversity hotspot.

PubMed

Woodcock, Paul; Edwards, David P; Newton, Rob J; Vun Khen, Chey; Bottrell, Simon H; Hamer, Keith C

2013-01-01

Trophic organisation defines the flow of energy through ecosystems and is a key component of community structure. Widespread and intensifying anthropogenic disturbance threatens to disrupt trophic organisation by altering species composition and relative abundances and by driving shifts in the trophic ecology of species that persist in disturbed ecosystems. We examined how intensive disturbance caused by selective logging affects trophic organisation in the biodiversity hotspot of Sabah, Borneo. Using stable nitrogen isotopes, we quantified the positions in the food web of 159 leaf-litter ant species in unlogged and logged rainforest and tested four predictions: (i) there is a negative relationship between the trophic position of a species in unlogged forest and its change in abundance following logging, (ii) the trophic positions of species are altered by logging, (iii) disturbance alters the frequency distribution of trophic positions within the ant assemblage, and (iv) disturbance reduces food chain length. We found that ant abundance was 30% lower in logged forest than in unlogged forest but changes in abundance of individual species were not related to trophic position, providing no support for prediction (i). However, trophic positions of individual species were significantly higher in logged forest, supporting prediction (ii). Consequently, the frequency distribution of trophic positions differed significantly between unlogged and logged forest, supporting prediction (iii), and food chains were 0.2 trophic levels longer in logged forest, the opposite of prediction (iv). Our results demonstrate that disturbance can alter trophic organisation even without trophically-biased changes in community composition. Nonetheless, the absence of any reduction in food chain length in logged forest suggests that species-rich arthropod food webs do not experience trophic downgrading or a related collapse in trophic organisation despite the disturbance caused by logging. These food webs appear able to bend without breaking in the face of some forms of anthropogenic disturbance.

Pleiotrophin over-expression provides trophic support to dopaminergic neurons in parkinsonian rats

PubMed Central

2011-01-01

Background Pleiotrophin is known to promote the survival and differentiation of dopaminergic neurons in vitro and is up-regulated in the substantia nigra of Parkinson's disease patients. To establish whether pleiotrophin has a trophic effect on nigrostriatal dopaminergic neurons in vivo, we injected a recombinant adenovirus expressing pleiotrophin in the substantia nigra of 6-hydroxydopamine lesioned rats. Results The viral vector induced pleiotrophin over-expression by astrocytes in the substantia nigra pars compacta, without modifying endogenous neuronal expression. The percentage of tyrosine hydroxylase-immunoreactive cells as well as the area of their projections in the lesioned striatum was higher in pleiotrophin-treated animals than in controls. Conclusions These results indicate that pleiotrophin over-expression partially rescues tyrosine hydroxylase-immunoreactive cell bodies and terminals of dopaminergic neurons undergoing 6-hydroxydopamine-induced degeneration. PMID:21649894

The trophic effect of ouabain on retinal ganglion cells is mediated by IL-1β and TNF-α

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salles von-Held-Ventura, Juliana; Mázala-de-Oliveira, Thalita; Cândida da Rocha Oliveira, Amanda

Ouabain is a steroid hormone that binds to the enzyme Na{sup +}, K{sup +} – ATPase and stimulates different intracellular pathways controlling growth, proliferation and cell survival. IL-1β and TNF-α are pleiotropic molecules, conventionally regarded as pro-inflammatory cytokines with well-known effects in the immune system. In addition, IL-1β and TNF-α also play important roles in the nervous system including neuroprotective effects. Previous data from our group showed that ouabain treatment is able to induce an increase in retinal ganglion cell survival kept in mixed retinal cell cultures. The aim of this work was to investigate if IL-1β and TNF-α couldmore » be mediating the trophic effect of ouabain on retinal ganglion cells. Our results show that the trophic effect of ouabain on retinal ganglion cell was inhibited by either anti-IL-1β or anti-TNF-α antibodies. In agreement, IL-1β or TNF-α increased the retinal ganglion cells survival in a dose-dependent manner. Accordingly, ouabain treatment induces a temporal release of TNF-α and IL-1β from retinal cell cultures. Interestingly, TNF-α and IL-1β regulate each other intracellular levels. Our results suggest that ouabain treatment triggers the activation of TNF-α and IL-1β signaling pathways leading to an increase in retinal ganglion cell survival. - Highlights: • Pro-inflammatory cytokines regulates the ouabain effect on RGC survival. • Ouabain treatment modulates the intracellular levels of TNF-α and IL-1β. • Ouabain induces the release of TNF-α and IL-1β in retinal cell cultures.« less

Wasp-Waist Interactions in the North Sea Ecosystem

PubMed Central

Fauchald, Per; Skov, Henrik; Skern-Mauritzen, Mette; Johns, David; Tveraa, Torkild

2011-01-01

Background In a “wasp-waist” ecosystem, an intermediate trophic level is expected to control the abundance of predators through a bottom-up interaction and the abundance of prey through a top-down interaction. Previous studies suggest that the North Sea is mainly governed by bottom-up interactions driven by climate perturbations. However, few studies have investigated the importance of the intermediate trophic level occupied by small pelagic fishes. Methodology/Principal Findings We investigated the numeric interactions among 10 species of seabirds, two species of pelagic fish and four groups of zooplankton in the North Sea using decadal-scale databases. Linear models were used to relate the time series of zooplankton and seabirds to the time series of pelagic fish. Seabirds were positively related to herring (Clupea harengus), suggesting a bottom-up interaction. Two groups of zooplankton; Calanus helgolandicus and krill were negatively related to sprat (Sprattus sprattus) and herring respectively, suggesting top-down interactions. In addition, we found positive relationships among the zooplankton groups. Para/pseudocalanus was positively related to C. helgolandicus and C. finmarchicus was positively related to krill. Conclusion/Significance Our results indicate that herring was important in regulating the abundance of seabirds through a bottom-up interaction and that herring and sprat were important in regulating zooplankton through top-down interactions. We suggest that the positive relationships among zooplankton groups were due to selective foraging and switching in the two clupeid fishes. Our results suggest that “wasp-waist” interactions might be more important in the North Sea than previously anticipated. Fluctuations in the populations of pelagic fish due to harvesting and depletion of their predators might accordingly have profound consequences for ecosystem dynamics through trophic cascades. PMID:21829494

Climate-mediated changes in marine ecosystem regulation during El Niño.

PubMed

Lindegren, Martin; Checkley, David M; Koslow, Julian A; Goericke, Ralf; Ohman, Mark D

2018-02-01

The degree to which ecosystems are regulated through bottom-up, top-down, or direct physical processes represents a long-standing issue in ecology, with important consequences for resource management and conservation. In marine ecosystems, the role of bottom-up and top-down forcing has been shown to vary over spatio-temporal scales, often linked to highly variable and heterogeneously distributed environmental conditions. Ecosystem dynamics in the Northeast Pacific have been suggested to be predominately bottom-up regulated. However, it remains unknown to what extent top-down regulation occurs, or whether the relative importance of bottom-up and top-down forcing may shift in response to climate change. In this study, we investigate the effects and relative importance of bottom-up, top-down, and physical forcing during changing climate conditions on ecosystem regulation in the Southern California Current System (SCCS) using a generalized food web model. This statistical approach is based on nonlinear threshold models and a long-term data set (~60 years) covering multiple trophic levels from phytoplankton to predatory fish. We found bottom-up control to be the primary mode of ecosystem regulation. However, our results also demonstrate an alternative mode of regulation represented by interacting bottom-up and top-down forcing, analogous to wasp-waist dynamics, but occurring across multiple trophic levels and only during periods of reduced bottom-up forcing (i.e., weak upwelling, low nutrient concentrations, and primary production). The shifts in ecosystem regulation are caused by changes in ocean-atmosphere forcing and triggered by highly variable climate conditions associated with El Niño. Furthermore, we show that biota respond differently to major El Niño events during positive or negative phases of the Pacific Decadal Oscillation (PDO), as well as highlight potential concerns for marine and fisheries management by demonstrating increased sensitivity of pelagic fish to exploitation during El Niño. © 2017 John Wiley & Sons Ltd.

Extracting plant phenology metrics in a Great Basin watershed: methods and considerations for quantifying phenophases in a cold desert

USDA-ARS?s Scientific Manuscript database

Plant phenology is recognized as important for all trophic interactions. There has been a recent advent of phenology and camera networks worldwide. The established PhenoCam Network has sites in coterminous United States, including the western states. However, there is a paucity of published research...

Water-quality effects on phytoplankton species and density and trophic state indices at Big Base and Little Base Lakes, Little Rock Air Force Base, Arkansas, June through August, 2015

USGS Publications Warehouse

Driver, Lucas; Justus, Billy

2016-01-01

Big Base and Little Base Lakes are located on Little Rock Air Force Base, Arkansas, and their close proximity to a dense residential population and an active military/aircraft installation make the lakes vulnerable to water-quality degradation. The U.S. Geological Survey (USGS) conducted a study from June through August 2015 to investigate the effects of water quality on phytoplankton species and density and trophic state in Big Base and Little Base Lakes, with particular regard to nutrient concentrations. Nutrient concentrations, trophic-state indices, and the large part of the phytoplankton biovolume composed of cyanobacteria, indicate eutrophic conditions were prevalent for Big Base and Little Base Lakes, particularly in August 2015. Cyanobacteria densities and biovolumes measured in this study likely pose a low to moderate risk of adverse algal toxicity, and the high proportion of filamentous cyanobacteria in the lakes, in relation to other algal groups, is important from a fisheries standpoint because these algae are a poor food source for many aquatic taxa. In both lakes, total nitrogen to total phosphorus (N:P) ratios declined over the sampling period as total phosphorus concentrations increased relative to nitrogen concentrations. The N:P ratios in the August samples (20:1 and 15:1 in Big Base and Little Base Lakes, respectively) and other indications of eutrophic conditions are of concern and suggest that exposure of the two lakes to additional nutrients could cause unfavorable dissolved-oxygen conditions and increase the risk of cyanobacteria blooms and associated cyanotoxin issues.

Direct and indirect trophic effects of predator depletion on basal trophic levels.

PubMed

Chen, Huili; Hagerty, Steven; Crotty, Sinead M; Bertness, Mark D

2016-02-01

Human population growth and development have heavily degraded coastal ecosystems with cascading impacts across multiple trophic levels. Understanding both the direct and indirect trophic effects of human activities is important for coastal conservation. In New England, recreational overfishing has triggered a regional trophic cascade. Predator depletion releases the herbivorous purple marsh crab from consumer control and leads to overgrazing of marsh cordgrass and salt marsh die-off. The direct and indirect trophic effects of predator depletion on basal trophic levels, however, are not understood. Using observational and experimental data, we examined the hypotheses that (1) direct trophic effects of predator depletion decrease meiofaunal abundance by releasing deposit feeding fiddler crabs from consumer control, and/or (2) indirect trophic effects of predator depletion increase meiofaunal abundance by releasing blue carbon via the erosion of centuries of accreted marsh peat. Experimental deposit feeder removal led to 23% higher meiofaunal density at die-off than at healthy sites, while reciprocally transplanting sediment from die-off and healthy sites revealed that carbon-rich die-off sediment increased meiofauna density by over 164%: six times stronger than direct trophic effects. Recovering sites had both carbon-rich sediment and reduced deposit feeding leading to higher meiofauna densities than both die-off and healthy sites. This suggests that consequences of the trophic downgrading of coastal habitats can be driven by both direct and indirect trophic mechanisms that may vary in direction and magnitude, making their elucidation dependent on experimental manipulations.

[Eutrophication control in local area by physic-ecological engineering].

PubMed

Li, Qiu-Hua; Xia, Pin-Hua; Wu, Hong; Lin, Tao; Zhang, You-Chun; Li, Cun-Xiong; Chen, Li-Li; Yang, Fan

2012-07-01

An integrated physical and ecological engineering experiment for ecological remediation was performed at the Maixi River bay in Baihua Reservoir Guizhou Province, China. The results show that eutrophic parameters, such as total nitrogen, total phosphorus, chlorophyll a and chemical oxygen demand from the experimental site (enclosed water) were significantly lower than those of the reference site. The largest differences between the sites were 0.61 mg x L(-1), 0.041 mg x L(-1), 23.06 microg x L(-1), 8.4 mg x L(-1) respectively; experimental site transparency was > 1.50 m which was significantly higher than that of the reference site. The eutrophic index of the experimental site was oligo-trophic and mid-trophic, while the control site was mid-trophic state and eutrophic state. Phytoplankton abundance was 2 125.5 x 10(4) cells x L(-1) in June, 2011 at the control site,but phytoplankton abundance was lower at the experimental site with 33 x 10(4) cells x L(-1). Cyanobacteria dominated phytoplankton biomass at both sites, however the experimental site consisted of a higher proportion of diatoms and dinoflagellates. After more than one year of operation, the ecological engineering technology effectively controlled the occurrence of algae blooms, changed phytoplankton community structure, and controlled the negative impacts of eutrophication. Integrating physical and ecological engineering technology could improve water quality for reservoirs on the Guizhou plateau.

Effects of near-future ocean acidification, fishing, and marine protection on a temperate coastal ecosystem.

PubMed

Cornwall, Christopher E; Eddy, Tyler D

2015-02-01

Understanding ecosystem responses to global and local anthropogenic impacts is paramount to predicting future ecosystem states. We used an ecosystem modeling approach to investigate the independent and cumulative effects of fishing, marine protection, and ocean acidification on a coastal ecosystem. To quantify the effects of ocean acidification at the ecosystem level, we used information from the peer-reviewed literature on the effects of ocean acidification. Using an Ecopath with Ecosim ecosystem model for the Wellington south coast, including the Taputeranga Marine Reserve (MR), New Zealand, we predicted ecosystem responses under 4 scenarios: ocean acidification + fishing; ocean acidification + MR (no fishing); no ocean acidification + fishing; no ocean acidification + MR for the year 2050. Fishing had a larger effect on trophic group biomasses and trophic structure than ocean acidification, whereas the effects of ocean acidification were only large in the absence of fishing. Mortality by fishing had large, negative effects on trophic group biomasses. These effects were similar regardless of the presence of ocean acidification. Ocean acidification was predicted to indirectly benefit certain species in the MR scenario. This was because lobster (Jasus edwardsii) only recovered to 58% of the MR biomass in the ocean acidification + MR scenario, a situation that benefited the trophic groups lobsters prey on. Most trophic groups responded antagonistically to the interactive effects of ocean acidification and marine protection (46%; reduced response); however, many groups responded synergistically (33%; amplified response). Conservation and fisheries management strategies need to account for the reduced recovery potential of some exploited species under ocean acidification, nonadditive interactions of multiple factors, and indirect responses of species to ocean acidification caused by declines in calcareous predators. © 2014 Society for Conservation Biology.

The Trophic Life Cycle Stage of the Opportunistic Fungal Pathogen Pneumocystis murina Hinders the Ability of Dendritic Cells To Stimulate CD4+ T Cell Responses

PubMed Central

Evans, Heather M.; Simpson, Andrew; Shen, Shu; Stromberg, Arnold J.; Pickett, Carol L.

2017-01-01

ABSTRACT The life cycle of the opportunistic fungal pathogen Pneumocystis murina consists of a trophic stage and an ascus-like cystic stage. Infection with the cyst stage induces proinflammatory immune responses, while trophic forms suppress the cytokine response to multiple pathogen-associated molecular patterns (PAMPs), including β-glucan. A targeted gene expression assay was used to evaluate the dendritic cell response following stimulation with trophic forms alone, with a normal mixture of trophic forms and cysts, or with β-glucan. We demonstrate that stimulation with trophic forms downregulated the expression of multiple genes normally associated with the response to infection, including genes encoding transcription factors. Trophic forms also suppressed the expression of genes related to antigen processing and presentation, including the gene encoding the major histocompatibility complex (MHC) class II transactivator, CIITA. Stimulation of dendritic cells with trophic forms, but not a mixture of trophic forms and cysts, reduced the expression of MHC class II and the costimulatory molecule CD40 on the surface of the cells. These defects in the expression of MHC class II and costimulatory molecules corresponded with a reduced capacity for trophic form-loaded dendritic cells to stimulate CD4+ T cell proliferation and polarization. These data are consistent with the delayed innate and adaptive responses previously observed in immunocompetent mice inoculated with trophic forms compared to responses in mice inoculated with a mixture of trophic forms and cysts. We propose that trophic forms broadly inhibit the ability of dendritic cells to fulfill their role as antigen-presenting cells. PMID:28694293

Reef Fishes at All Trophic Levels Respond Positively to Effective Marine Protected Areas

PubMed Central

Soler, German A.; Edgar, Graham J.; Thomson, Russell J.; Kininmonth, Stuart; Campbell, Stuart J.; Dawson, Terence P.; Barrett, Neville S.; Bernard, Anthony T. F.; Galván, David E.; Willis, Trevor J.; Alexander, Timothy J.; Stuart-Smith, Rick D.

2015-01-01

Marine Protected Areas (MPAs) offer a unique opportunity to test the assumption that fishing pressure affects some trophic groups more than others. Removal of larger predators through fishing is often suggested to have positive flow-on effects for some lower trophic groups, in which case protection from fishing should result in suppression of lower trophic groups as predator populations recover. We tested this by assessing differences in the trophic structure of reef fish communities associated with 79 MPAs and open-access sites worldwide, using a standardised quantitative dataset on reef fish community structure. The biomass of all major trophic groups (higher carnivores, benthic carnivores, planktivores and herbivores) was significantly greater (by 40% - 200%) in effective no-take MPAs relative to fished open-access areas. This effect was most pronounced for individuals in large size classes, but with no size class of any trophic group showing signs of depressed biomass in MPAs, as predicted from higher predator abundance. Thus, greater biomass in effective MPAs implies that exploitation on shallow rocky and coral reefs negatively affects biomass of all fish trophic groups and size classes. These direct effects of fishing on trophic structure appear stronger than any top down effects on lower trophic levels that would be imposed by intact predator populations. We propose that exploitation affects fish assemblages at all trophic levels, and that local ecosystem function is generally modified by fishing. PMID:26461104

Trophic factors from adipose tissue-derived multi-lineage progenitor cells promote cytodifferentiation of periodontal ligament cells.

PubMed

Sawada, Keigo; Takedachi, Masahide; Yamamoto, Satomi; Morimoto, Chiaki; Ozasa, Masao; Iwayama, Tomoaki; Lee, Chun Man; Okura, Hanayuki; Matsuyama, Akifumi; Kitamura, Masahiro; Murakami, Shinya

2015-08-14

Stem and progenitor cells are currently being investigated for their applicability in cell-based therapy for periodontal tissue regeneration. We recently demonstrated that the transplantation of adipose tissue-derived multi-lineage progenitor cells (ADMPCs) enhances periodontal tissue regeneration in beagle dogs. However, the molecular mechanisms by which transplanted ADMPCs induce periodontal tissue regeneration remain to be elucidated. In this study, trophic factors released by ADMPCs were examined for their paracrine effects on human periodontal ligament cell (HPDL) function. ADMPC conditioned medium (ADMPC-CM) up-regulated osteoblastic gene expression, alkaline phosphatase activity and calcified nodule formation in HPDLs, but did not significantly affect their proliferative response. ADMPCs secreted a number of growth factors, including insulin-like growth factor binding protein 6 (IGFBP6), hepatocyte growth factor and vascular endothelial growth factor. Among these, IGFBP6 was most highly expressed. Interestingly, the positive effects of ADMPC-CM on HPDL differentiation were significantly suppressed by transfecting ADMPCs with IGFBP6 siRNA. Our results suggest that ADMPCs transplanted into a defect in periodontal tissue release trophic factors that can stimulate the differentiation of HPDLs to mineralized tissue-forming cells, such as osteoblasts and cementoblasts. IGFBP6 may play crucial roles in ADMPC-induced periodontal regeneration. Copyright © 2015 Elsevier Inc. All rights reserved.

Neural Influences on Sonic Hedgehog and Apoptosis in the Rat Penis1

PubMed Central

Bond, Christopher; Tang, Yi; Podlasek, Carol A.

2010-01-01

The role of sonic hedgehog (SHH) in maintaining corpora cavernosal morphology in the adult penis has been established; however, the mechanism of how SHH itself is regulated remains unclear. Since decreased SHH protein is a cause of smooth muscle apoptosis and erectile dysfunction (ED) in the penis, and SHH treatment can suppress cavernous nerve (CN) injury-induced apoptosis, the question of how SHH signaling is regulated is significant. It is likely that neural input is involved in this process since two models of neuropathy-induced ED exhibit decreased SHH protein and increased apoptosis in the penis. We propose the hypothesis that SHH abundance in the corpora cavernosa is regulated by SHH signaling in the pelvic ganglia, neural activity, or neural transport of a trophic factor from the pelvic ganglia to the corpora. We have examined each of these potential mechanisms. SHH inhibition in the penis shows a 12-fold increase in smooth muscle apoptosis. SHH inhibition in the pelvic ganglia causes significantly increased apoptosis (1.3-fold) and decreased SHH protein (1.1-fold) in the corpora cavernosa. SHH protein is not transported by the CN. Colchicine treatment of the CN resulted in significantly increased smooth muscle apoptosis (1.2-fold) and decreased SHH protein (1.3-fold) in the penis. Lidocaine treatment of the CN caused a similar increase in apoptosis (1.6-fold) and decrease in SHH protein (1.3-fold) in the penis. These results show that neural activity and a trophic factor from the pelvic ganglia/CN are necessary to regulate SHH protein and smooth muscle abundance in the penis. PMID:18256331

Expanding models of lake trophic state to predict cyanobacteria in lakes

EPA Science Inventory

Background/Question/Methods: Cyanobacteria are a primary taxonomic group associated with harmful algal blooms in lakes. Understanding the drivers of cyanobacteria presence has important implications for lake management and for the protection of human and ecosystem health. Chlor...

The ups and downs of trophic control in continental shelf ecosystems.

PubMed

Frank, Kenneth T; Petrie, Brian; Shackell, Nancy L

2007-05-01

Traditionally, marine ecosystem structure was thought to be determined by phytoplankton dynamics. However, an integrated view on the relative roles of top-down (consumer-driven) and bottom-up (resource-driven) forcing in large-scale, exploited marine ecosystems is emerging. Long time series of scientific survey data, underpinning the management of commercially exploited species such as cod, are being used to diagnose mechanisms that could affect the composition and relative abundance of species in marine food webs. By assembling published data from studies in exploited North Atlantic ecosystems, we found pronounced geographical variation in top-down and bottom-up trophic forcing. The data suggest that ecosystem susceptibility to top-down control and their resiliency to exploitation are related to species richness and oceanic temperature conditions. Such knowledge could be used to produce ecosystem guidelines to regulate and manage fisheries in a sustainable fashion.

Trophic and Non-Trophic Interactions in a Biodiversity Experiment Assessed by Next-Generation Sequencing

PubMed Central

Tiede, Julia; Wemheuer, Bernd; Traugott, Michael; Daniel, Rolf; Tscharntke, Teja; Ebeling, Anne; Scherber, Christoph

2016-01-01

Plant diversity affects species richness and abundance of taxa at higher trophic levels. However, plant diversity effects on omnivores (feeding on multiple trophic levels) and their trophic and non-trophic interactions are not yet studied because appropriate methods were lacking. A promising approach is the DNA-based analysis of gut contents using next generation sequencing (NGS) technologies. Here, we integrate NGS-based analysis into the framework of a biodiversity experiment where plant taxonomic and functional diversity were manipulated to directly assess environmental interactions involving the omnivorous ground beetle Pterostichus melanarius. Beetle regurgitates were used for NGS-based analysis with universal 18S rDNA primers for eukaryotes. We detected a wide range of taxa with the NGS approach in regurgitates, including organisms representing trophic, phoretic, parasitic, and neutral interactions with P. melanarius. Our findings suggest that the frequency of (i) trophic interactions increased with plant diversity and vegetation cover; (ii) intraguild predation increased with vegetation cover, and (iii) neutral interactions with organisms such as fungi and protists increased with vegetation cover. Experimentally manipulated plant diversity likely affects multitrophic interactions involving omnivorous consumers. Our study therefore shows that trophic and non-trophic interactions can be assessed via NGS to address fundamental questions in biodiversity research. PMID:26859146

Size-dependent trophic patterns of pallid sturgeon and shovelnose sturgeon in a large river system

USGS Publications Warehouse

French, William E.; Graeb, Brian D. S.; Bertrand, Katie N.; Chipps, Steven R.; Klumb, Robert A.

2013-01-01

This study compared patterns of δ15N and δ13C enrichment of pallid sturgeon Scaphirhynchus albus and shovelnose sturgeon S. platorynchus in the Missouri River, United States, to infer their trophic position in a large river system. We examined enrichment and energy flow for pallid sturgeon in three segments of the Missouri River (Montana/North Dakota, Nebraska/South Dakota, and Nebraska/Iowa) and made comparisons between species in the two downstream segments (Nebraska/South Dakota and Nebraska/Iowa). Patterns in isotopic composition for pallid sturgeon were consistent with gut content analyses indicating an ontogenetic diet shift from invertebrates to fish prey at sizes of >500-mm fork length (FL) in all three segments of the Missouri River. Isotopic patterns revealed shovelnose sturgeon did not experience an ontogenetic shift in diet and used similar prey resources as small (<500-mm FL) pallid sturgeon in the two downstream segments. We found stable isotope analysis to be an effective tool for evaluating the trophic position of sturgeons within a large river food web.

Variability of Lekanesphaera monodi metabolic rates with habitat trophic status

NASA Astrophysics Data System (ADS)

Vignes, Fabio; Fedele, Marialaura; Pinna, Maurizio; Mancinelli, Giorgio; Basset, Alberto

2012-05-01

Regulation of metabolism is a common strategy used by individuals to respond to a changing environment. The mechanisms underlying the variability of metabolic rates in macroinvertebrates are of primary importance in studying benthic-pelagic energy transfer in transitional water ecosystems. Lekanesphaera monodi is an isopod endemic to transitional water ecosystems that can modify its metabolic rate in response to environmental changes. Therefore it is a useful model in studying the influence of environmental factors on metabolism. This study focused on the interpopulation variability of standard metabolic rates (SMR) in L. monodi populations sampled in three transitional water ecosystems differing in their trophic status. The standard metabolic rates of L. monodi individuals across the same range of body size spectra were inferred from oxygen consumption measurements in a flow-through respirometer in the three populations and a body condition index was assessed for each population. Habitat trophic status was evaluated by monthly measurement of the basic physical-chemical parameters of the water column in the ecosystems for one year. Standard metabolic rates showed high variability, ranging from 0.27 to 10.14 J d-1. Body size accounted for more than 38% of total variability. In terms of trophic status, individuals from the eutrophic ecosystem had significantly higher standard metabolic rates than individuals from the other ecosystems (SMR = 2.3 J d-1 in Spunderati Sud vs. 1.36 J d-1 in Alimini and 0.69 J d-1 in Acquatina). The body conditions index was also higher in the population from the eutrophic ecosystem. Results show that standard metabolic rates and growth rates are directly related to habitat productivity in accordance with the expectations of the food habits hypothesis. A possible extension of this hypothesis to benthic invertebrates is proposed.

Unpacking brown food-webs: Animal trophic identity reflects rampant microbivory

USDA-ARS?s Scientific Manuscript database

Detritivory is the dominant trophic paradigm in most terrestrial, aquatic, and marine ecosystems, yet accurate measurement of consumer trophic position within detrital (= ‘brown’) food-webs has remained impenetrable. Measurement of detritivore trophic position is complicated by the fact that detritu...

Quantification of Carbon and Phosphorus Co-Limitation in Bacterioplankton: New Insights on an Old Topic

PubMed Central

Dorado-García, Irene; Medina-Sánchez, Juan Manuel; Herrera, Guillermo; Cabrerizo, Marco J.; Carrillo, Presentación

2014-01-01

Because the nature of the main resource that limits bacterioplankton (e.g. organic carbon [C] or phosphorus [P]) has biogeochemical implications concerning organic C accumulation in freshwater ecosystems, empirical knowledge is needed concerning how bacteria respond to these two resources, available alone or together. We performed field experiments of resource manipulation (2×2 factorial design, with the addition of C, P, or both combined) in two Mediterranean freshwater ecosystems with contrasting trophic states (oligotrophy vs. eutrophy) and trophic natures (autotrophy vs. heterotrophy, measured as gross primary production:respiration ratio). Overall, the two resources synergistically co-limited bacterioplankton, i.e. the magnitude of the response of bacterial production and abundance to the two resources combined was higher than the additive response in both ecosystems. However, bacteria also responded positively to single P and C additions in the eutrophic ecosystem, but not to single C in the oligotrophic one, consistent with the value of the ratio between bacterial C demand and algal C supply. Accordingly, the trophic nature rather than the trophic state of the ecosystems proves to be a key feature determining the expected types of resource co-limitation of bacteria, as summarized in a proposed theoretical framework. The actual types of co-limitation shifted over time and partially deviated (a lesser degree of synergism) from the theoretical expectations, particularly in the eutrophic ecosystem. These deviations may be explained by extrinsic ecological forces to physiological limitations of bacteria, such as predation, whose role in our experiments is supported by the relationship between the dynamics of bacteria and bacterivores tested by SEMs (structural equation models). Our study, in line with the increasingly recognized role of freshwater ecosystems in the global C cycle, suggests that further attention should be focussed on the biotic interactions that modulate resource co-limitation of bacteria. PMID:24918445

Modelling impacts of offshore wind farms on trophic web: the Courseulles-sur-Mer case study

NASA Astrophysics Data System (ADS)

Raoux, Aurore; Pezy, Jean-Philippe; Dauvin, Jean-Claude; Tecchio, samuele; Degraer, Steven; Wilhelmsson, Dan; Niquil, Nathalie

2016-04-01

The French government is planning the construction of three offshore wind farms in Normandy. These offshore wind farms will integrate into an ecosystem already subject to a growing number of anthropogenic disturbances such as transportation, fishing, sediment deposit, and sediment extraction. The possible effects of this cumulative stressors on ecosystem functioning are still unknown, but they could impact their resilience, making them susceptible to changes from one stable state to another. Understanding the behaviour of these marine coastal complex systems is essential in order to anticipate potential state changes, and to implement conservation actions in a sustainable manner. Currently, there are no global and integrated studies on the effects of construction and exploitation of offshore wind farms. Moreover, approaches are generally focused on the conservation of some species or groups of species. Here, we develop a holistic and integrated view of ecosystem impacts through the use of trophic webs modelling tools. Trophic models describe the interaction between biological compartments at different trophic levels and are based on the quantification of flow of energy and matter in ecosystems. They allow the application of numerical methods for the characterization of emergent properties of the ecosystem, also called Ecological Network Analysis (ENA). These indices have been proposed as ecosystem health indicators as they have been demonstrated to be sensitive to different impacts on marine ecosystems. We present here in detail the strategy for analysing the potential environmental impacts of the construction of the Courseulles-sur-Mer offshore wind farm (Bay of Seine) such as the reef effect through the use of the Ecopath with Ecosim software. Similar Ecopath simulations will be made in the future on the Le Tréport offshore wind farm site. Results will contribute to a better knowledge of the impacts of the offshore wind farms on ecosystems. They also allow to define recommendations for environmental managers and industry in terms of monitoring the effects of Marine Renewable Energy, not only locally, but also on other sites, national and European levels. Finally, this approach could contribute to a better social acceptability of Marine Renewable Energy projects allowing a holistic vision of all pressures on ecosystems. Keywords: Marine Renewable Energies, trophic model Contact author: Aurore Raoux, UNICAEN, raoux.aurore@gmail.com

Richness-Productivity Relationships Between Trophic Levels in a Detritus-Based System: Significance of Abundance and Trophic Linkage.

EPA Science Inventory

Most theoretical and empirical studies of productivity–species richness relationships fail to consider linkages among trophic levels. We quantified productivity–richness relationships in detritus-based, water-filled tree-hole communities for two trophic levels: invertebrate consu...

Integrating microbes into food-chains: Insect trophic identity reflects rampant microbivory

USDA-ARS?s Scientific Manuscript database

Detritivory is the dominant trophic paradigm in most terrestrial, aquatic, and marine ecosystems, yet accurate measurement of consumer trophic position within detrital (= ‘brown’) food-webs has remained relatively impenetrable. Measurement of detritivore trophic position is complicated by the fact t...

Nitrergic ventro-medial medullary neurons activated during cholinergically induced active (REM) sleep in the cat

PubMed Central

Pose, Inés; Sampogna, Sharon; Chase, Michael H.; Morales, Francisco R.

2010-01-01

The rostral ventro-medial medullary reticular formation is a complex structure that is involved with a variety of motor functions. It contains glycinergic neurons that are activated during active (REM) sleep (AS); these neurons appear to be responsible for the postsynaptic inhibition of motoneurons that occurs during this state. We have reported that neurons in this same region contain nitric oxide (NO) synthase and that they innervate brainstem motor pools. In the present study we examined the c-fos expression of these neurons after carbachol-induced active sleep (C-AS). Three control and four experimental cats were employed to identify c-fos expressing nitrergic neurons using immunocytochemical techniques to detect the Fos protein together with neuronal nitric oxide synthase (nNOS) or NADPH-diaphorase activity. The classical neurotransmitter content of the nitrergic cells in this region was examined through the combination of immunocytochemical techniques for the detection of glutamate, glycine, choline acetyltransferase (ChAT), tyrosine hydroxilase (TH) or GABA together with nNOS. During C-AS, there was a 1074% increase in the number of nitrergic neurons that expressed c-fos. These neurons did not contain glycine, ChAT, TH or GABA, but a subpopulation (15%) of them displayed glutamate-like immunoreactivity. Therefore, some of these neurons contain both an excitatory neurotransmitter (glutamate) and an excitatory neuromodulator (NO); the neurotransmitter content of the rest of them remains to be determined. Because some of the nitrergic neurons innervate brainstem motoneurons it is possible that they participate in the generation of tonic and excitatory phasic motor events that occur during AS. We also suggest that these nitrergic neurons may be involved in autonomic regulation during this state. In addition, because NO has trophic effects on target neurons, the present findings represent the first, albeit indirect, evidence for a possible trophic function of this nature during AS. PMID:21044662

Individuals in food webs: the relationships between trophic position, omnivory and among-individual diet variation.

PubMed

Svanbäck, Richard; Quevedo, Mario; Olsson, Jens; Eklöv, Peter

2015-05-01

Among-individual diet variation is common in natural populations and may occur at any trophic level within a food web. Yet, little is known about its variation among trophic levels and how such variation could affect phenotypic divergence within populations. In this study we investigate the relationships between trophic position (the population's range and average) and among-individual diet variation. We test for diet variation among individuals and across size classes of Eurasian perch (Perca fluviatilis), a widespread predatory freshwater fish that undergoes ontogenetic niche shifts. Second, we investigate among-individual diet variation within fish and invertebrate populations in two different lake communities using stable isotopes. Third, we test potential evolutionary implications of population trophic position by assessing the relationship between the proportion of piscivorous perch (populations of higher trophic position) and the degree of phenotypic divergence between littoral and pelagic perch sub-populations. We show that among-individual diet variation is highest at intermediate trophic positions, and that this high degree of among-individual variation likely causes an increase in the range of trophic positions among individuals. We also found that phenotypic divergence was negatively related to trophic position in a population. This study thus shows that trophic position is related to and may be important for among-individual diet variation as well as to phenotypic divergence within populations.

Urbanization as a threat to biodiversity: trophic theory, economic geography, and implications for conservation land acquisition

Treesearch

Brian Czech

2005-01-01

Habitat loss is often cited as the primary cause of species endangerment in the United States, followed by invasive species, pollution, and direct take. Urbanization, one type of habitat loss, is the leading cause of species endangerment in the contiguous United States and entails a relatively thorough transformation from the "economy of nature" to the human...

'Trophic' and 'source' amino acids in trophic estimation: a likely metabolic explanation.

PubMed

O'Connell, T C

2017-06-01

Amino acid nitrogen isotopic analysis is a relatively new method for estimating trophic position. It uses the isotopic difference between an individual's 'trophic' and 'source' amino acids to determine its trophic position. So far, there is no accepted explanation for the mechanism by which the isotopic signals in 'trophic' and 'source' amino acids arise. Yet without a metabolic understanding, the utility of nitrogen isotopic analyses as a method for probing trophic relations, at either bulk tissue or amino acid level, is limited. I draw on isotopic tracer studies of protein metabolism, together with a consideration of amino acid metabolic pathways, to suggest that the 'trophic'/'source' groupings have a fundamental metabolic origin, to do with the cycling of amino-nitrogen between amino acids. 'Trophic' amino acids are those whose amino-nitrogens are interchangeable, part of a metabolic amino-nitrogen pool, and 'source' amino acids are those whose amino-nitrogens are not interchangeable with the metabolic pool. Nitrogen isotopic values of 'trophic' amino acids will reflect an averaged isotopic signal of all such dietary amino acids, offset by the integrated effect of isotopic fractionation from nitrogen cycling, and modulated by metabolic and physiological effects. Isotopic values of 'source' amino acids will be more closely linked to those of equivalent dietary amino acids, but also modulated by metabolism and physiology. The complexity of nitrogen cycling suggests that a single identifiable value for 'trophic discrimination factors' is unlikely to exist. Greater consideration of physiology and metabolism should help in better understanding observed patterns in nitrogen isotopic values.

Expanding Models of Lake Trophic State to Predict Cyanobacteria in Lakes: A Data Mining Approach

EPA Science Inventory

Background/Question/Methods: Cyanobacteria are a primary taxonomic group associated with harmful algal blooms in lakes. Understanding the drivers of cyanobacteria presence has important implications for lake management and for the protection of human and ecosystem health. Chloro...

Use of Landsat data to predict the trophic state of Minnesota lakes

NASA Technical Reports Server (NTRS)

Lillesand, T. M.; Johnson, W. L.; Deuell, R. L.; Lindstrom, O. M.; Meisner, D. E.

1983-01-01

Near-concurrent Landsat Multispectral Scanner (MSS) and ground data were obtained for 60 lakes distributed in two Landsat scene areas. The ground data included measurement of secchi disk depth, chlorophyll-a, total phosphorous, turbidity, color, and total nitrogen, as well as Carlson Trophic State Index (TSI) values derived from the first three parameters. The Landsat data best correlated with the TSI values. Prediction models were developed to classify some 100 'test' lakes appearing in the two analysis scenes on the basis of TSI estimates. Clouds, wind, poor image data, small lake size, and shallow lake depth caused some problems in lake TSI prediction. Overall, however, the Landsat-predicted TSI estimates were judged to be very reliable for the secchi-derived TSI estimation, moderately reliable for prediction of the chlorophyll-a TSI, and unreliable for the phosphorous value. Numerous Landsat data extraction procedures were compared, and the success of the Landsat TSI prediction models was a strong function of the procedure employed.

Trophic state and toxic cyanobacteria density in optimization modeling of multi-reservoir water resource systems.

PubMed

Sulis, Andrea; Buscarinu, Paola; Soru, Oriana; Sechi, Giovanni M

2014-04-22

The definition of a synthetic index for classifying the quality of water bodies is a key aspect in integrated planning and management of water resource systems. In previous works [1,2], a water system optimization modeling approach that requires a single quality index for stored water in reservoirs has been applied to a complex multi-reservoir system. Considering the same modeling field, this paper presents an improved quality index estimated both on the basis of the overall trophic state of the water body and on the basis of the density values of the most potentially toxic Cyanobacteria. The implementation of the index into the optimization model makes it possible to reproduce the conditions limiting water use due to excessive nutrient enrichment in the water body and to the health hazard linked to toxic blooms. The analysis of an extended limnological database (1996-2012) in four reservoirs of the Flumendosa-Campidano system (Sardinia, Italy) provides useful insights into the strengths and limitations of the proposed synthetic index.

Trophic conditions in Lake Winnisquam, New Hampshire

USGS Publications Warehouse

Frost, Leonard R.

1977-01-01

Lake Winnisquam has received treated domestic sewage for approximately 50 years and since June 1961 has been treated with copper sulfate to control the growth of nuisance algae. The Laconia City secondary sewage-treatment plant was upgraded in 1975 to include phosphorus removal. Phosphorus was not removed effectively until early 1976, and, therefore, the 1976 data are considered baseline or pre-phosphorus removal with respect to anticipated changes in the trophic condition of the lake. Effluent from the Laconia State School primary-treatment plant was diverted to the Laconia City plant in October 1976. Dissolved oxygen concentrations showed marked differences between the two basins comprising Lake Winnisquam. Phytoplankton samples showed similarities by algal group for all stations but algal genera varied between the upper and lower basins. Total phosphorus concentrations in the epilimnion ranged from 0.01 to 0.10 milligram per liter, and accumulation of total phosphorus in the hypolimnion resulted in concentrations up to 0.59 milligrams per liter. Chemical states of nutrients varied among the stations corresponding to the degree of depletion of hypolimnetic dissolved oxygen. Dissolved oxygen profiles were used to illustrate zones of algal production, respiration, and bacterial decomposition. The rate of depletion of dissolved oxygen in the hypolimnion was linearly related to time. Because change in the rate of hypolimnetic dissolved oxygen depletion is more easily measured than change of nutrient load in the lake, it is suggested it be used as an indicator of the response of the lake to change in trophic condition.

The distribution of persistent organic pollutants in a trophically complex Antarctic ecosystem model

NASA Astrophysics Data System (ADS)

Bates, Michael L.; Bengtson Nash, Susan M.; Hawker, Darryl W.; Shaw, Emily C.; Cropp, Roger A.

2017-06-01

Despite Antarctica's isolation from human population centres, persistent organic pollutants (POPs) are transported there via long range atmospheric transport and subsequently cold-trapped. The challenging nature of working in the Antarctic environment greatly limits our ability to monitor POP concentrations and understand the processes that govern the distribution of POPs in Antarctic ecosystems. Here we couple a dynamic, trophically complex biological model with a fugacity model to investigate the distribution of hexachlorobenzene (HCB) in a near-shore Antarctic ecosystem. Using this model we examine the steady-state, and annual cycle of HCB concentration in the atmosphere, ocean, sediment, detritus, and 21 classes of biota that span from primary producers to apex predators. The scope and trophic resolution of our model allows us to examine POP pathways through the ecosystem. In our model the main pathway of HCB to upper trophic species is via pelagic communities, with relatively little via benthic communities. Using a dynamic ecosystem model also allows us to examine the seasonal and potential climate change induced changes in POP distribution. We show that there is a large annual cycle in concentration in the planktonic communities, which may have implications for biomagnification factors calculated from observations. We also examine the direct effects of increasing temperature on the redistribution of HCB in a changing climate and find that it is likely minor compared to other indirect effects, such as changes in atmospheric circulation, sea ice dynamics, and changes to the ecosystem itself.

Estimation of a Trophic State Index for selected inland lakes in Michigan, 1999–2013

USGS Publications Warehouse

Fuller, Lori M.; Jodoin, Richard S.

2016-03-11

A 15-year estimated Trophic State Index (eTSI) for Michigan inland lakes is available, and it spans seven datasets, each representing 1 to 3 years of data from 1999 to 2013. On average, 3,000 inland lake eTSI values are represented in each of the datasets by a process that relates field-measured Secchi-disk transparency (SDT) to Landsat satellite imagery to provide eTSI values for unsampled inland lakes. The correlation between eTSI values and field-measured Trophic State Index (TSI) values from SDT was strong as shown by R2 values from 0.71 to 0.83. Mean eTSI values ranged from 42.7 to 46.8 units, which when converted to estimated SDT (eSDT) ranged from 8.9 to 12.5 feet for the datasets. Most eTSI values for Michigan inland lakes are in the mesotrophic TSI class. The Environmental Protection Agency (EPA) Level III Ecoregions were used to illustrate and compare the spatial distribution of eTSI classes for Michigan inland lakes. Lakes in the Northern Lakes and Forests, North Central Hardwood Forests, and Southern Michigan/Northern Indiana Drift Plains ecoregions are predominantly in the mesotrophic TSI class. The Huron/Erie Lake Plains and Eastern Corn Belt Plains ecoregions, had predominantly eutrophic class lakes and also the highest percent of hypereutrophic lakes than other ecoregions in the State. Data from multiple sampling programs—including data collected by volunteers with the Cooperative Lakes Monitoring Program (CLMP) through the Michigan Department of Environmental Quality (MDEQ), and the 2007 National Lakes Assessment (NLA)—were compiled to compare the distribution of lake TSI classes between each program. The seven eTSI datasets are available for viewing and download with eSDT from the Michigan Lake Water Clarity Interactive Map Viewer at http://mi.water.usgs.gov/projects/RemoteSensing/index.html.

How habitat-modifying organisms structure the food web of two coastal ecosystems

PubMed Central

van der Zee, Els M.; Angelini, Christine; Govers, Laura L.; Christianen, Marjolijn J. A.; Altieri, Andrew H.; van der Reijden, Karin J.; Silliman, Brian R.; van de Koppel, Johan; van der Geest, Matthijs; van Gils, Jan A.; van der Veer, Henk W.; Piersma, Theunis; de Ruiter, Peter C.; Olff, Han; van der Heide, Tjisse

2016-01-01

The diversity and structure of ecosystems has been found to depend both on trophic interactions in food webs and on other species interactions such as habitat modification and mutualism that form non-trophic interaction networks. However, quantification of the dependencies between these two main interaction networks has remained elusive. In this study, we assessed how habitat-modifying organisms affect basic food web properties by conducting in-depth empirical investigations of two ecosystems: North American temperate fringing marshes and West African tropical seagrass meadows. Results reveal that habitat-modifying species, through non-trophic facilitation rather than their trophic role, enhance species richness across multiple trophic levels, increase the number of interactions per species (link density), but decrease the realized fraction of all possible links within the food web (connectance). Compared to the trophic role of the most highly connected species, we found this non-trophic effects to be more important for species richness and of more or similar importance for link density and connectance. Our findings demonstrate that food webs can be fundamentally shaped by interactions outside the trophic network, yet intrinsic to the species participating in it. Better integration of non-trophic interactions in food web analyses may therefore strongly contribute to their explanatory and predictive capacity. PMID:26962135

How habitat-modifying organisms structure the food web of two coastal ecosystems.

PubMed

van der Zee, Els M; Angelini, Christine; Govers, Laura L; Christianen, Marjolijn J A; Altieri, Andrew H; van der Reijden, Karin J; Silliman, Brian R; van de Koppel, Johan; van der Geest, Matthijs; van Gils, Jan A; van der Veer, Henk W; Piersma, Theunis; de Ruiter, Peter C; Olff, Han; van der Heide, Tjisse

2016-03-16

The diversity and structure of ecosystems has been found to depend both on trophic interactions in food webs and on other species interactions such as habitat modification and mutualism that form non-trophic interaction networks. However, quantification of the dependencies between these two main interaction networks has remained elusive. In this study, we assessed how habitat-modifying organisms affect basic food web properties by conducting in-depth empirical investigations of two ecosystems: North American temperate fringing marshes and West African tropical seagrass meadows. Results reveal that habitat-modifying species, through non-trophic facilitation rather than their trophic role, enhance species richness across multiple trophic levels, increase the number of interactions per species (link density), but decrease the realized fraction of all possible links within the food web (connectance). Compared to the trophic role of the most highly connected species, we found this non-trophic effects to be more important for species richness and of more or similar importance for link density and connectance. Our findings demonstrate that food webs can be fundamentally shaped by interactions outside the trophic network, yet intrinsic to the species participating in it. Better integration of non-trophic interactions in food web analyses may therefore strongly contribute to their explanatory and predictive capacity. © 2016 The Author(s).

Nutrients, phytoplankton, zooplankton, and macrobenthos

USGS Publications Warehouse

Rudstam, Lars G.; Holeck, Kristen T.; Watkins, James M.; Hotaling, Christopher; Lantry, Jana R.; Bowen, Kelly L.; Munawar, Mohi; Weidel, Brian C.; Barbiero, Richard; Luckey, Frederick J.; Dove, Alice; Johnson, Timothy B.; Biesinger, Zy

2017-01-01

Lower trophic levels support the prey fish on which most sport fish depend. Therefore, understanding the production potential of lower trophic levels is integral to the management of Lake Ontario’s fishery resources. Lower trophic-level productivity differs among offshore and nearshore waters. In the offshore, there is concern about the ability of the lake to support Alewife (Table 1) production due to a perceived decline in productivity of phytoplankton and zooplankton whereas, in the nearshore, there is a concern about excessive attached algal production (e.g., Cladophora) associated with higher nutrient concentrations—the oligotrophication of the offshore and the eutrophication of the nearshore (Mills et al. 2003; Holeck et al. 2008; Dove 2009; Koops et al. 2015; Stewart et al. 2016). Even though the collapse of the Alewife population in Lake Huron in 2003 (and the associated decline in the Chinook Salmon fishery) may have been precipitated by a cold winter (Dunlop and Riley 2013), Alewife had not returned to high abundances in Lake Huron as of 2014 (Roseman et al. 2015). Failure of the Alewife population to recover from collapse has been attributed to declines in lower trophic-level production (Barbiero et al. 2011; Bunnell et al. 2014; but see He et al. 2015). In Lake Michigan, concerns of a similar Alewife collapse led to a decrease in the number of Chinook Salmon stocked. If lower trophic-level production declines in Lake Ontario, a similar management action could be considered. On the other hand, in Lake Erie, which supplies most of the water in Lake Ontario, eutrophication is increasing and so are harmful algal blooms. Thus, there is also a concern that nutrient levels and algal blooms could increase in Lake Ontario, especially in the nearshore. Solutions to the two processes of concern—eutrophication in the nearshore and oligotrophication in the offshore—may be mutually exclusive. In either circumstance, fisheries management needs information on the productivity of lower trophic levels in Lake Ontario. In this chapter, we review the status of lower trophic levels in Lake Ontario with special attention to the current (2008-2013) and previous (2003-2007) reporting periods. During the two reporting periods, three whole-lake surveys of lower trophic levels were conducted: the Lower Trophic Level Assessment (LOLA) in 2003 and 2008 (Makarewicz and Howell 2012; Munawar et al. 2015b) and the Cooperative Science and Management Initiative (CSMI) in 2013. Analyses of the CSMI data are ongoing. In addition to the three one-year sources of information on lower trophic levels, several multi-year sources of information are available, including data from the surveillance program conducted since 1965 by Environment Canada (EC) (Dove 2009), monitoring conducted since 1980 by the U.S. Environmental Protection Agency’s (EPA) Great Lakes National Program Office (GLNPO) (Barbiero et al. 2014; Reavie et al. 2014), sampling for a Bioindex Program at two stations, one offshore and one in the Eastern Basin, assessments of Mysis diluviana (formerly Mysis relicta) conducted since 1980 by Fisheries and Oceans Canada (Johannsson et al. 1998, 2011) and the Ontario Ministry of Natural Resources and Forestry (OMNRF), and monitoring conducted since 1995 by the Biomonitoring Program (BMP) on the New York side of the lake (Holeck et al. 2015b). The BMP is a collaboration of the New York State Department of Environmental Conservation (DEC), U.S. Fish and Wildlife Service, U.S. Geological Survey (USGS), and Cornell University.

Bioaccumulation and trophic transfer of cyclic volatile methylsiloxanes (cVMS) in the aquatic marine food webs of the Oslofjord, Norway.

PubMed

Powell, David E; Schøyen, Merete; Øxnevad, Sigurd; Gerhards, Reinhard; Böhmer, Thomas; Koerner, Martin; Durham, Jeremy; Huff, Darren W

2018-05-01

The trophic transfer of cyclic methylsiloxanes (cVMS) in aquatic ecosystems is an important criterion for assessing bioaccumulation and ecological risk. Bioaccumulation and trophic transfer of cVMS, specifically octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6), were evaluated for the marine food webs of the Inner and Outer Oslofjord, Norway. The sampled food webs included zooplankton, benthic macroinvertebrates, shellfish, and finfish species. Zooplankton, benthic macroinvertebrates, and shellfish occupied the lowest trophic levels (TL ≈2 to 3); northern shrimp (Pandalus borealis) and Atlantic herring (Clupea harengus) occupied the middle trophic levels (TL ≈3 to 4), and Atlantic cod (Gadus morhua) occupied the highest tropic level (TL>4.0). Trophic dynamics in the Oslofjord were best described as a compressed food web defined by demersal and pelagic components that were confounded by a diversity in prey organisms and feeding relationships. Lipid-normalized concentrations of D4, D5, and D6 were greatest in the lowest trophic levels and significantly decreased up the food web, with the lowest concentrations being observed in the highest trophic level species. Trophic magnification factors (TMF) for D4, D5, and D6 were <1.0 (range 0.3 to 0.9) and were consistent between the Inner and Outer Oslofjord, indicating that exposure did not impact TMF across the marine food web. There was no evidence to suggest biomagnification of cVMS in the Oslofjord. Rather, results indicated that trophic dilution of cVMS, not trophic magnification, occurred across the sampled food webs. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Responses of trophic structure and zooplankton community to salinity and temperature in Tibetan lakes: Implication for the effect of climate warming.

PubMed

Lin, Qiuqi; Xu, Lei; Hou, Juzhi; Liu, Zhengwen; Jeppesen, Erik; Han, Bo-Ping

2017-11-01

Warming has pronounced effects on lake ecosystems, either directly by increased temperatures or indirectly by a change in salinity. We investigated the current status of zooplankton communities and trophic structure in 45 Tibetan lakes along a 2300 m altitude and a 76 g/l salinity gradient. Freshwater to hyposaline lakes mainly had three trophic levels: phytoplankton, small zooplankton and fish/Gammarus, while mesosaline to hypersaline lakes only had two: phytoplankton and large zooplankton. Zooplankton species richness declined significantly with salinity, but did not relate with temperature. Furthermore, the decline in species richness with salinity in lakes with two trophic levels was much less abrupt than in lakes with three trophic levels. The structural variation of the zooplankton community depended on the length of the food chain, and was significantly explained by salinity as the critical environmental variable. The zooplankton community shifted from dominance of copepods and small cladoceran species in the lakes with low salinity and three trophic levels to large saline filter-feeding phyllopod species in those lakes with high salinity and two trophic levels. The zooplankton to phytoplankton biomass ratio was positively related with temperature in two-trophic-level systems and vice versa in three-trophic-level systems. As the Tibetan Plateau is warming about three times faster than the global average, our results imply that warming could have a considerable impact on the structure and function of Tibetan lake ecosystems, either via indirect effects of salinization/desalinization on species richness, composition and trophic structure or through direct effects of water temperature on trophic interactions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Phytohormone mediation of interactions between herbivores and plant pathogens.

PubMed

Lazebnik, Jenny; Frago, Enric; Dicke, Marcel; van Loon, Joop J A

2014-07-01

Induced plant defenses against either pathogens or herbivore attackers are regulated by phytohormones. These phytohormones are increasingly recognized as important mediators of interactions between organisms associated with plants. In this review, we discuss the role of plant defense hormones in sequential tri-partite interactions among plants, pathogenic microbes, and herbivorous insects, based on the most recent literature. We discuss the importance of pathogen trophic strategy in the interaction with herbivores that exhibit different feeding modes. Plant resistance mechanisms also affect plant quality in future interactions with attackers. We discuss exemplary evidence for the hypotheses that (i) biotrophic pathogens can facilitate chewing herbivores, unless plants exhibit effector-triggered immunity, but (ii) facilitate or inhibit phloem feeders. (iii) Necrotrophic pathogens, on the other hand, can inhibit both phloem feeders and chewers. We also propose herbivore feeding mode as predictor of effects on pathogens of different trophic strategies, providing evidence for the hypotheses that (iv) phloem feeders inhibit pathogen attack by increasing SA induction, whereas (v) chewing herbivores tend not to affect necrotrophic pathogens, while they may either inhibit or facilitate biotrophic pathogens. Putting these hypotheses to the test will increase our understanding of phytohormonal regulation of plant defense to sequential attack by plant pathogens and insect herbivores. This will provide valuable insight into plant-mediated ecological interactions among members of the plant-associated community.

Age-Dependent Neurochemical Remodeling of Hypothalamic Astrocytes.

PubMed

Santos, Camila Leite; Roppa, Paola Haack Amaral; Truccolo, Pedro; Fontella, Fernanda Urruth; Souza, Diogo Onofre; Bobermin, Larissa Daniele; Quincozes-Santos, André

2017-10-04

The hypothalamus is a crucial integrative center in the central nervous system, responsible for the regulation of homeostatic activities, including systemic energy balance. Increasing evidence has highlighted a critical role of astrocytes in orchestrating hypothalamic functions; they participate in the modulation of synaptic transmission, metabolic and trophic support to neurons, immune defense, and nutrient sensing. In this context, disturbance of systemic energy homeostasis, which is a common feature of obesity and the aging process, involves inflammatory responses. This may be related to dysfunction of hypothalamic astrocytes. In this regard, the aim of this study was to evaluate the neurochemical properties of hypothalamic astrocyte cultures from newborn, adult, and aged Wistar rats. Age-dependent changes in the regulation of glutamatergic homeostasis, glutathione biosynthesis, amino acid profile, glucose metabolism, trophic support, and inflammatory response were observed. Additionally, signaling pathways including nuclear factor erythroid-derived 2-like 2/heme oxygenase-1 p38 mitogen-activated protein kinase, nuclear factor kappa B, phosphatidylinositide 3-kinase/Akt, and leptin receptor expression may represent putative mechanisms associated with the cellular alterations. In summary, our findings indicate that as age increases, hypothalamic astrocytes remodel and exhibit changes in their neurochemical properties. This process may play a role in the onset and/or progression of metabolic disorders.

Expression of cholecystokinin2-receptor in rat and human L cells and the stimulation of glucagon-like peptide-1 secretion by gastrin treatment.

PubMed

Cao, Yang; Cao, Xun; Liu, Xiao-Min

2015-03-01

Gastrin is a gastrointestinal hormone secreted by G cells. Hypergastrinemia can improve blood glucose and glycosylated hemoglobin levels. These positive effects are primarily due to the trophic effects of gastrin on β-cells. In recent years, many receptors that regulate secretion of glucagon-like peptide 1 (GLP-1) have been identified in enteroendocrine L cell lines. This led us to hypothesize that, in addition to the trophic effects of gastrin on β-cells, L cells also express cholecystokinin2-receptor (CCK2R), which may regulate GLP-1 secretion and have synergistic effects on glucose homeostasis. Our research provides a preliminary analysis of CCK2R expression and the stimulating effect of gastrin treatment on GLP-1 secretion in a human endocrine L cell line, using RT-PCR, Western blot, immunocytochemistry, and ELISA analyses. The expression of proglucagon and prohormone convertase 3, which regulate GLP-1 biosynthesis, were also analyzed by real-time PCR. Double immunofluorescence labeling was utilized to assess the intracellular localization of CCK2R and GLP-1 in L cells harvested from rat colon tissue. Our results showed that CCK2R was expressed in both the human L cell line and the rat L cells. We also showed that treatment with gastrin, a CCK2R agonist, stimulated the secretion of GLP-1, and that this effect was likely due to increased expression of proglucagon and PCSK1 (also known as prohormone convertase 3 (PC3 gene)). These results not only provide a basis for the role gastrin may play in intestinal L cells, and may also provide the basis for the development of a method of gastrin-mediated glycemic regulation. Copyright © 2014 Elsevier GmbH. All rights reserved.

Lessons learned from the USEPA Environmental Monitoring and Assessment Program for Great River Ecosystems

EPA Science Inventory

We assessed the North American mid-continent great rivers (Upper Mississippi, Missouri, and Ohio). We estimated the extent of each river in most (MDC) or least-disturbed condition (LDC) based on multiple biological response indicators (fish and macroinvertebrates, trophic state ...

Variation in trophic shift for stable isotope ratios of carbon, nitrogen, and sulfur

USGS Publications Warehouse

McCutchan, J.H.; Lewis, W.M.; Kendall, C.; McGrath, C.C.

2003-01-01

Use of stable isotope ratios to trace pathways of organic matter among consumers requires knowledge of the isotopic shift between diet and consumer. Variation in trophic shift among consumers can be substantial. For data from the published literature and supplementary original data (excluding fluid-feeding consumers), the mean isotopic shift for C was +0.5 ?? 0.13??? rather than 0.0???, as commonly assumed. The shift for C was higher for consumers analyzed as muscle (+1.3 ?? 0.30???) than for consumers analyzed whole (+0.3 ?? 0.14???). Among consumers analyzed whole, the trophic shift for C was lower for consumers acidified prior to analysis (-0.2 ?? 0.21???) than for unacidified samples (+0.5 ?? 0.17???). For N, trophic shift was lower for consumers raised on invertebrate diets (+1.4 ?? 0.21???) than for consumers raised on other high-protein diets (+3.3 ?? 0.26???) and was intermediate for consumers raised on plant and algal diets (+2.2 ?? 0.30???). The trophic shift for S differed between high-protein (+2.0 ?? 0.65???) and low-protein diets (-0.5 ?? 0.56???). Thus, methods of analysis and dietary differences can affect trophic shift for consumers; the utility of stable isotope methods can be improved if this information is incorporated into studies of trophic relationships. Although few studies of stable isotope ratios have considered variation in the trophic shift, such variation is important because small errors in estimates of trophic shift can result in large errors in estimates of the contribution of sources to consumers or in estimates of trophic position.

Benthic Trophic Interactions in an Antarctic Shallow Water Ecosystem Affected by Recent Glacier Retreat.

PubMed

Pasotti, Francesca; Saravia, Leonardo Ariel; De Troch, Marleen; Tarantelli, Maria Soledad; Sahade, Ricardo; Vanreusel, Ann

2015-01-01

The western Antarctic Peninsula is experiencing strong environmental changes as a consequence of ongoing regional warming. Glaciers in the area are retreating rapidly and increased sediment-laden meltwater runoff threatens the benthic biodiversity at shallow depths. We identified three sites with a distinct glacier-retreat related history and different levels of glacial influence in the inner part of Potter Cove (King George Island, South Shetland Islands), a fjord-like embayment impacted since the 1950s by a tidewater glacier retreat. We compared the soft sediment meio- and macrofauna isotopic niche widths (δ13C and δ15N stable isotope analysis) at the three sites to investigate possible glacier retreat-related influences on benthic trophic interactions. The isotopic niches were locally shaped by the different degrees of glacier retreat-related disturbance within the Cove. Wider isotopic niche widths were found at the site that has become ice-free most recently, and narrower niches at the older ice-free sites. At an intermediate state of glacier retreat-related disturbance (e.g. via ice-growler scouring) species with different strategies could settle. The site at the earliest stage of post-retreat development was characterized by an assemblage with lower trophic redundancy. Generally, the isotopic niche widths increased with increasing size spectra of organisms within the community, excepting the youngest assemblage, where the pioneer colonizer meiofauna size class displayed the highest isotopic niche width. Meiofauna at all sites generally occupied positions in the isotopic space that suggested a detrital-pool food source and/or the presence of predatory taxa. In general ice scour and glacial impact appeared to play a two-fold role within the Cove: i) either stimulating trophic diversity by allowing continuous re-colonization of meiofaunal species or, ii) over time driving the benthic assemblages into a more compact trophic structure with increased connectedness and resource recycling.

Benthic Trophic Interactions in an Antarctic Shallow Water Ecosystem Affected by Recent Glacier Retreat

PubMed Central

Pasotti, Francesca; Saravia, Leonardo Ariel; De Troch, Marleen; Tarantelli, Maria Soledad; Sahade, Ricardo; Vanreusel, Ann

2015-01-01

The western Antarctic Peninsula is experiencing strong environmental changes as a consequence of ongoing regional warming. Glaciers in the area are retreating rapidly and increased sediment-laden meltwater runoff threatens the benthic biodiversity at shallow depths. We identified three sites with a distinct glacier-retreat related history and different levels of glacial influence in the inner part of Potter Cove (King George Island, South Shetland Islands), a fjord-like embayment impacted since the 1950s by a tidewater glacier retreat. We compared the soft sediment meio- and macrofauna isotopic niche widths (δ13C and δ15N stable isotope analysis) at the three sites to investigate possible glacier retreat-related influences on benthic trophic interactions. The isotopic niches were locally shaped by the different degrees of glacier retreat-related disturbance within the Cove. Wider isotopic niche widths were found at the site that has become ice-free most recently, and narrower niches at the older ice-free sites. At an intermediate state of glacier retreat-related disturbance (e.g. via ice-growler scouring) species with different strategies could settle. The site at the earliest stage of post-retreat development was characterized by an assemblage with lower trophic redundancy. Generally, the isotopic niche widths increased with increasing size spectra of organisms within the community, excepting the youngest assemblage, where the pioneer colonizer meiofauna size class displayed the highest isotopic niche width. Meiofauna at all sites generally occupied positions in the isotopic space that suggested a detrital-pool food source and/or the presence of predatory taxa. In general ice scour and glacial impact appeared to play a two-fold role within the Cove: i) either stimulating trophic diversity by allowing continuous re-colonization of meiofaunal species or, ii) over time driving the benthic assemblages into a more compact trophic structure with increased connectedness and resource recycling. PMID:26559062

Salinization triggers a trophic cascade in experimental freshwater communities with varying food-chain length.

PubMed

Hintz, William D; Mattes, Brian M; Schuler, Matthew S; Jones, Devin K; Stoler, Aaron B; Lind, Lovisa; Relyea, Rick A

2017-04-01

The application of road deicing salts in northern regions worldwide is changing the chemical environment of freshwater ecosystems. Chloride levels in many lakes, streams, and wetlands exceed the chronic and acute thresholds established by the United States and Canada for the protection of freshwater biota. Few studies have identified the impacts of deicing salts in stream and wetland communities and none have examined impacts in lake communities. We tested how relevant concentrations of road salt (15, 100, 250, 500, and 1000 mg Cl - /L) interacted with experimental communities containing two or three trophic levels (i.e., no fish vs. predatory fish). We hypothesized that road salt and fish would have a negative synergistic effect on zooplankton, which would then induce a trophic cascade. We tested this hypothesis in outdoor mesocosms containing filamentous algae, periphyton, phytoplankton, zooplankton, several macroinvertebrate species, and fish. We found that the presence of fish and high salt had a negative synergistic effect on the zooplankton community, which in turn caused an increase in phytoplankton. Contributing to the magnitude of this trophic cascade was a direct positive effect of high salinity on phytoplankton abundance. Cascading effects were limited with respect to impacts on the benthic food web. Periphyton and snail grazers were unaffected by the salt-induced trophic cascade, but the biomass of filamentous algae decreased as a result of competition with phytoplankton for light or nutrients. We also found direct negative effects of high salinity on the biomass of filamentous algae and amphipods (Hyalella azteca) and the mortality of banded mystery snails (Viviparus georgianus) and fingernail clams (Sphaerium simile). Clam mortality was dependent on the presence of fish, suggesting a non-consumptive interactive effect with salt. Our results indicate that globally increasing concentrations of road salt can alter community structure via both direct and indirect effects. © 2016 by the Ecological Society of America.

Isotope niche dimension and trophic overlap between bigheaded carps and native filter-feeding fish in the lower Missouri River, USA

USGS Publications Warehouse

Wang, Jianzhu; Chapman, Duane C.; Xu, Jun; Wang, Yang; Gu, Binhe

2018-01-01

Stable carbon and nitrogen isotope values (δ13C and δ15N) were used to evaluate trophic niche overlap between two filter-feeding fishes (known together as bigheaded carp) native to China, silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis), and three native filter-feeding fish including bigmouth buffalo (Ictiobus cyprinellus), gizzard shad (Dorosoma cepedianum) and paddlefish (Polyodon spathula) in the lower Missouri River, USA, using the Bayesian Stable Isotope in R statistics. Results indicate that except for bigmouth buffalo, all species displayed similar trophic niche size and trophic diversity. Bigmouth buffalo occupied a small trophic niche and had the greatest trophic overlap with silver carp (93.6%) and bighead carp (94.1%) followed by gizzard shad (91.0%). Paddlefish had a trophic niche which relied on some resources different from those used by other species, and therefore had the lowest trophic overlap with bigheaded carp and other two native fish. The trophic overlap by bigheaded carp onto native fish was typically stronger than the reverse effects from native fish. Average niche overlap between silver carp and native species was as high as 71%, greater than niche overlap between bighead carp and native fish (64%). Our findings indicate that bigheaded carps are a potential threat to a diverse and stable native fish community.

Neurotrophic factors and receptors in the immature and adult spinal cord after mechanical injury or kainic acid.

PubMed

Widenfalk, J; Lundströmer, K; Jubran, M; Brene, S; Olson, L

2001-05-15

Delivery of neurotrophic factors to the injured spinal cord has been shown to stimulate neuronal survival and regeneration. This indicates that a lack of sufficient trophic support is one factor contributing to the absence of spontaneous regeneration in the mammalian spinal cord. Regulation of the expression of neurotrophic factors and receptors after spinal cord injury has not been studied in detail. We investigated levels of mRNA-encoding neurotrophins, glial cell line-derived neurotrophic factor (GDNF) family members and related receptors, ciliary neurotrophic factor (CNTF), and c-fos in normal and injured spinal cord. Injuries in adult rats included weight-drop, transection, and excitotoxic kainic acid delivery; in newborn rats, partial transection was performed. The regulation of expression patterns in the adult spinal cord was compared with that in the PNS and the neonate spinal cord. After mechanical injury of the adult rat spinal cord, upregulations of NGF and GDNF mRNA occurred in meningeal cells adjacent to the lesion. BDNF and p75 mRNA increased in neurons, GDNF mRNA increased in astrocytes close to the lesion, and GFRalpha-1 and truncated TrkB mRNA increased in astrocytes of degenerating white matter. The relatively limited upregulation of neurotrophic factors in the spinal cord contrasted with the response of affected nerve roots, in which marked increases of NGF and GDNF mRNA levels were observed in Schwann cells. The difference between the ability of the PNS and CNS to provide trophic support correlates with their different abilities to regenerate. Kainic acid delivery led to only weak upregulations of BDNF and CNTF mRNA. Compared with several brain regions, the overall response of the spinal cord tissue to kainic acid was weak. The relative sparseness of upregulations of endogenous neurotrophic factors after injury strengthens the hypothesis that lack of regeneration in the spinal cord is attributable at least partly to lack of trophic support.

Nitrogen Addition Regulates Soil Nematode Community Composition through Ammonium Suppression

PubMed Central

Wei, Cunzheng; Zheng, Huifen; Li, Qi; Lü, Xiaotao; Yu, Qiang; Zhang, Haiyang; Chen, Quansheng; He, Nianpeng; Kardol, Paul; Liang, Wenju; Han, Xingguo

2012-01-01

Nitrogen (N) enrichment resulting from anthropogenic activities has greatly changed the composition and functioning of soil communities. Nematodes are one of the most abundant and diverse groups of soil organisms, and they occupy key trophic positions in the soil detritus food web. Nematodes have therefore been proposed as useful indicators for shifts in soil ecosystem functioning under N enrichment. Here, we monitored temporal dynamics of the soil nematode community using a multi-level N addition experiment in an Inner Mongolia grassland. Measurements were made three years after the start of the experiment. We used structural equation modeling (SEM) to explore the mechanisms regulating nematode responses to N enrichment. Across the N enrichment gradient, significant reductions in total nematode abundance, diversity (H' and taxonomic richness), maturity index (MI), and the abundance of root herbivores, fungivores and omnivores-predators were found in August. Root herbivores recovered in September, contributing to the temporal variation of total nematode abundance across the N gradient. Bacterivores showed a hump-shaped relationship with N addition rate, both in August and September. Ammonium concentration was negatively correlated with the abundance of total and herbivorous nematodes in August, but not in September. Ammonium suppression explained 61% of the variation in nematode richness and 43% of the variation in nematode trophic group composition. Ammonium toxicity may occur when herbivorous nematodes feed on root fluid, providing a possible explanation for the negative relationship between herbivorous nematodes and ammonium concentration in August. We found a significantly positive relationship between fungivores and fungal phospholipid fatty acids (PLFA), suggesting bottom-up control of fungivores. No such relationship was found between bacterivorous nematodes and bacterial PLFA. Our findings contribute to the understanding of effects of N enrichment in semiarid grassland on soil nematode trophic groups, and the cascading effects in the detrital soil food web. PMID:22952671

Temporal variation in the biochemical ecology of lower trophic levels in the Northern California Current

NASA Astrophysics Data System (ADS)

Miller, J. A.; Peterson, W. T.; Copeman, L. A.; Du, X.; Morgan, C. A.; Litz, M. N. C.

2017-06-01

There is strong correlative evidence that variation in the growth and survival of secondary consumers is related to the copepod species composition within the Northern California Current. Potential mechanisms driving these correlations include: (1) enhanced growth and survival of secondary consumers when lipid-rich, boreal copepod species are abundant, with cascading effects on higher trophic levels; (2) the regulation of growth and condition of primary and secondary consumers by the relative proportion of certain essential fatty acids (FAs) in primary producers; or (3) a combination of these factors. Disentangling the relative importance of taxonomic composition, lipid quantity, and FA composition on the nutritional quality of copepods requires detailed information on both the consumer and primary producers. Therefore, we collected phytoplankton and copepods at an oceanographic station for 19 months and completed species community analyses and generated detailed lipid profiles, including lipid classes and FAs, for both groups. There was strong covariation between species and biochemistry within and across trophic levels and distinct seasonal differences. The amount of total lipid within both the phytoplankton and copepod communities was twice as high in spring and summer than in fall and winter, and certain FAs, such as diatom indicators 20:5ω3 and 16:1ω7, comprised a greater proportion of the FA pool in spring and summer. Indicators of bacterial production within the copepod community were proportionally twice as high during fall and winter than spring and summer. Seasonal transitions in copepod FA composition were consistently offset from transitions in copepod species composition by approximately two weeks. The timing of the seasonal transition in copepod FAs reflected seasonal shifts in the species composition and/or biochemistry of primary producers more than seasonal shifts in the copepod species composition. These results emphasize the importance of interactions between the copepod community and their available phytoplankton prey in regulating the nutritional quality of primary consumers.

Land Use Influences Niche Size and the Assimilation of Resources by Benthic Macroinvertebrates in Tropical Headwater Streams

PubMed Central

Parreira de Castro, Diego Marcel; Reis de Carvalho, Débora; Pompeu, Paulo dos Santos; Moreira, Marcelo Zacharias; Nardoto, Gabriela Bielefeld; Callisto, Marcos

2016-01-01

It is well recognized that assemblage structure of stream macroinvertebrates changes with alterations in catchment or local land use. Our objective was to understand how the trophic ecology of benthic macroinvertebrate assemblages responds to land use changes in tropical streams. We used the isotope methodology to assess how energy flow and trophic relations among macroinvertebrates were affected in environments affected by different land uses (natural cover, pasture, sugar cane plantation). Macroinvertebrates were sampled and categorized into functional feeding groups, and available trophic resources were sampled and evaluated for the isotopic composition of 13C and 15N along streams located in the Cerrado (neotropical savanna). Streams altered by pasture or sugar cane had wider and more overlapped trophic niches, which corresponded to more generalist feeding habits. In contrast, trophic groups in streams with native vegetation had narrower trophic niches with smaller overlaps, suggesting greater specialization. Pasture sites had greater ranges of resources exploited, indicating higher trophic diversity than sites with natural cover and sugar cane plantation. We conclude that agricultural land uses appears to alter the food base and shift macroinvertebrate assemblages towards more generalist feeding behaviors and greater overlap of the trophic niches. PMID:26934113

Trophic Ecology of Benthic Marine Invertebrates with Bi-Phasic Life Cycles: What Are We Still Missing?

PubMed

Calado, Ricardo; Leal, Miguel Costa

2015-01-01

The study of trophic ecology of benthic marine invertebrates with bi-phasic life cycles is critical to understand the mechanisms shaping population dynamics. Moreover, global climate change is impacting the marine environment at an unprecedented level, which promotes trophic mismatches that affect the phenology of these species and, ultimately, act as drivers of ecological and evolutionary change. Assessing the trophic ecology of marine invertebrates is critical to understanding maternal investment, larval survival to metamorphosis, post-metamorphic performance, resource partitioning and trophic cascades. Tools already available to assess the trophic ecology of marine invertebrates, including visual observation, gut content analysis, food concentration, trophic markers, stable isotopes and molecular genetics, are reviewed and their main advantages and disadvantages for qualitative and quantitative approaches are discussed. The challenges to perform the partitioning of ingestion, digestion and assimilation are discussed together with different approaches to address each of these processes for short- and long-term fingerprinting. Future directions for research on the trophic ecology of benthic marine invertebrates with bi-phasic life cycles are discussed with emphasis on five guidelines that will allow for systematic study and comparative meta-analysis to address important unresolved questions. © 2015 Elsevier Ltd. All rights reserved.

Land Use Influences Niche Size and the Assimilation of Resources by Benthic Macroinvertebrates in Tropical Headwater Streams.

PubMed

Parreira de Castro, Diego Marcel; Reis de Carvalho, Débora; Pompeu, Paulo dos Santos; Moreira, Marcelo Zacharias; Nardoto, Gabriela Bielefeld; Callisto, Marcos

2016-01-01

It is well recognized that assemblage structure of stream macroinvertebrates changes with alterations in catchment or local land use. Our objective was to understand how the trophic ecology of benthic macroinvertebrate assemblages responds to land use changes in tropical streams. We used the isotope methodology to assess how energy flow and trophic relations among macroinvertebrates were affected in environments affected by different land uses (natural cover, pasture, sugar cane plantation). Macroinvertebrates were sampled and categorized into functional feeding groups, and available trophic resources were sampled and evaluated for the isotopic composition of 13C and 15N along streams located in the Cerrado (neotropical savanna). Streams altered by pasture or sugar cane had wider and more overlapped trophic niches, which corresponded to more generalist feeding habits. In contrast, trophic groups in streams with native vegetation had narrower trophic niches with smaller overlaps, suggesting greater specialization. Pasture sites had greater ranges of resources exploited, indicating higher trophic diversity than sites with natural cover and sugar cane plantation. We conclude that agricultural land uses appears to alter the food base and shift macroinvertebrate assemblages towards more generalist feeding behaviors and greater overlap of the trophic niches.

Trophic signatures of seabirds suggest shifts in oceanic ecosystems

PubMed Central

Gagne, Tyler O.; Hyrenbach, K. David; Hagemann, Molly E.; Van Houtan, Kyle S.

2018-01-01

Pelagic ecosystems are dynamic ocean regions whose immense natural capital is affected by climate change, pollution, and commercial fisheries. Trophic level–based indicators derived from fishery catch data may reveal the food web status of these systems, but the utility of these metrics has been debated because of targeting bias in fisheries catch. We analyze a unique, fishery-independent data set of North Pacific seabird tissues to inform ecosystem trends over 13 decades (1890s to 2010s). Trophic position declined broadly in five of eight species sampled, indicating a long-term shift from higher–trophic level to lower–trophic level prey. No species increased their trophic position. Given species prey preferences, Bayesian diet reconstructions suggest a shift from fishes to squids, a result consistent with both catch reports and ecosystem models. Machine learning models further reveal that trophic position trends have a complex set of drivers including climate, commercial fisheries, and ecomorphology. Our results show that multiple species of fish-consuming seabirds may track the complex changes occurring in marine ecosystems. PMID:29457134

Trophic signatures of seabirds suggest shifts in oceanic ecosystems.

PubMed

Gagne, Tyler O; Hyrenbach, K David; Hagemann, Molly E; Van Houtan, Kyle S

2018-02-01

Pelagic ecosystems are dynamic ocean regions whose immense natural capital is affected by climate change, pollution, and commercial fisheries. Trophic level-based indicators derived from fishery catch data may reveal the food web status of these systems, but the utility of these metrics has been debated because of targeting bias in fisheries catch. We analyze a unique, fishery-independent data set of North Pacific seabird tissues to inform ecosystem trends over 13 decades (1890s to 2010s). Trophic position declined broadly in five of eight species sampled, indicating a long-term shift from higher-trophic level to lower-trophic level prey. No species increased their trophic position. Given species prey preferences, Bayesian diet reconstructions suggest a shift from fishes to squids, a result consistent with both catch reports and ecosystem models. Machine learning models further reveal that trophic position trends have a complex set of drivers including climate, commercial fisheries, and ecomorphology. Our results show that multiple species of fish-consuming seabirds may track the complex changes occurring in marine ecosystems.

Fish community reassembly after a coral mass mortality: higher trophic groups are subject to increased rates of extinction.

PubMed

Alonso, David; Pinyol-Gallemí, Aleix; Alcoverro, Teresa; Arthur, Rohan

2015-05-01

Since Gleason and Clements, our understanding of community dynamics has been influenced by theories emphasising either dispersal or niche assembly as central to community structuring. Determining the relative importance of these processes in structuring real-world communities remains a challenge. We tracked reef fish community reassembly after a catastrophic coral mortality in a relatively unfished archipelago. We revisited the stochastic model underlying MacArthur and Wilson's Island Biogeography Theory, with a simple extension to account for trophic identity. Colonisation and extinction rates calculated from decadal presence-absence data based on (1) species neutrality, (2) trophic identity and (3) site-specificity were used to model post-disturbance reassembly, and compared with empirical observations. Results indicate that species neutrality holds within trophic guilds, and trophic identity significantly increases overall model performance. Strikingly, extinction rates increased clearly with trophic position, indicating that fish communities may be inherently susceptible to trophic downgrading even without targeted fishing of top predators. © 2015 John Wiley & Sons Ltd/CNRS.

Trophic Status, Ecological Condition and Cyanobacteria Risk of New England Lakes and Ponds Based on Aircraft Remote Sensing.

EPA Science Inventory

Aircraft remote sensing of freshwater ecosystems offers federal and state monitoring agencies an ability to meet their assessment requirements by rapidly acquiring information on ecosystem responses to environmental change for water bodies that are below the resolution of space...

Chesapeake Bay Future Conditions Report. Volume 6. Water Quality

DTIC Science & Technology

1977-12-01

Bay ecosystem. Beginning as a tropical depression off the Yucatan "Coast on I5 June 1972, Agnes moved from the Gulf of Mexico, across the Southern...ultimately assumes a completely terres- trial state and disappears. During eu- trophication, the lake becomes so rich in nutritive compounds

Stylet bundle morphology and trophically related enzymes of the hemlock woolly adelgid (Hemiptera: Adelgidae)

Treesearch

Kelly L.F. Oten; Allen C. Cohen; Fred P. Hain

2014-01-01

The hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), is a pest of eastern and Carolina hemlocks (Tsuga canadensis (L.) Carriere and Tsuga caroliniana Engelmann, respectively) in the eastern United States and has already caused catastrophic changes to eastern forests. As one of the significant...

Landsat ETM+ Secchi Disc Transparency (SDT) retrievals for Rawal Lake, Pakistan

NASA Astrophysics Data System (ADS)

Butt, Mohsin Jamil; Nazeer, Majid

2015-10-01

Satellite imagery holds significant potential for monitoring regional lake water clarity. This study addresses the use of satellite data and ground observations for the assessment of Rawal Lake water clarity in Pakistan. Satellite data from Landsat sensor for the years 2009-2013 are used to model Secchi Disc Transparency (SDT). Landsat images within ±3 days of the measured SDT data is used for the development of a regression model. The results of this study show that ETM+ band3 and band1/band3 ratio is the reliable predictor of SDT with R2 values of 0.725 and 0.793 respectively. The modeled SDT is further used to estimate the Trophic State Index (TSI) and trophic condition of Rawal Lake. In addition, the in situ Chlorophyll-a (Chl-a) and Total Phosphorus (TP) concentration are used to calculate the TSI of the Lake. The Mann-Kendall (MK) statistical test shows that the increasing trend in TSI based on SDT is significant (τ = 0.523). The trophic condition of Rawal Lake indicates that the Lake falls under the hypereutrophic category, that is, highly polluted and extremely unhealthy for the purpose of drinking.

Trophic amplification of climate warming

PubMed Central

Kirby, Richard R.; Beaugrand, Gregory

2009-01-01

Ecosystems can alternate suddenly between contrasting persistent states due to internal processes or external drivers. It is important to understand the mechanisms by which these shifts occur, especially in exploited ecosystems. There have been several abrupt marine ecosystem shifts attributed either to fishing, recent climate change or a combination of these two drivers. We show that temperature has been an important driver of the trophodynamics of the North Sea, a heavily fished marine ecosystem, for nearly 50 years and that a recent pronounced change in temperature established a new ecosystem dynamic regime through a series of internal mechanisms. Using an end-to-end ecosystem approach that included primary producers, primary, secondary and tertiary consumers, and detritivores, we found that temperature modified the relationships among species through nonlinearities in the ecosystem involving ecological thresholds and trophic amplifications. Trophic amplification provides an alternative mechanism to positive feedback to drive an ecosystem towards a new dynamic regime, which in this case favours jellyfish in the plankton and decapods and detritivores in the benthos. Although overfishing is often held responsible for marine ecosystem degeneration, temperature can clearly bring about similar effects. Our results are relevant to ecosystem-based fisheries management (EBFM), seen as the way forward to manage exploited marine ecosystems. PMID:19740882

[Strengths, weaknesses, and opportunities of French research in trophic ecology].

PubMed

Perga, Marie-Élodie; Danger, Michael; Dubois, Stanislas; Fritch, Clémentine; Gaucherel, Cédric; Hubas, Cedric; Jabot, Franck; Lacroix, Gérard; Lefebvre, Sébastien; Marmonier, Pierre; Bec, Alexandre

2018-05-30

The French National Institute of Ecology and Environment (INEE) aims at fostering pluridisciplinarity in Environmental Science and, for that purpose, funds ex muros research groups (GDR) on thematic topics. Trophic ecology has been identified as a scientific field in ecology that would greatly benefit from such networking activity, as being profoundly scattered. This has motivated the seeding of a GDR, entitled "GRET". The contours of the GRET's action, and its ability to fill these gaps within trophic ecology at the French national scale, will depend on the causes of this relative scattering. This study relied on a nationally broadcasted poll aiming at characterizing the field of trophic ecology in France. Amongst all the unique individuals that fulfilled the poll, over 300 belonged at least partly to the field of trophic ecology. The sample included all French public research institutes and career stages. Three main disruptions within the community of scientist in trophic ecology were identified. The first highlighted the lack of interfaces between microbial and trophic ecology. The second evidenced that research questions were strongly linked to single study fields or ecosystem type. Last, research activities are still quite restricted to the ecosystem boundaries. All three rupture points limit the conceptual and applied progression in the field of trophic ecology. Here we show that most of the disruptions within French Trophic Ecology are culturally inherited, rather than motivated by scientific reasons or justified by socio-economic stakes. Comparison with the current literature confirms that these disruptions are not necessarily typical of the French research landscape, but instead echo the general weaknesses of the international research in ecology. Thereby, communication and networking actions within and toward the community of trophic ecologists, as planned within the GRET's objectives, should contribute to fill these gaps, by reintegrating microbes within trophic concepts and setting the seeds for trans- and meta-ecosystemic research opportunities. Once the community of trophic ecologists is aware of the scientific benefit in pushing its boundaries forwards, turning words and good intentions into concrete research projects will depend on the opportunities to obtain research funding. Copyright © 2018 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.

The role of trophic factors and inflammatory processes in physical activity-induced neuroprotection in Parkinson's disease.

PubMed

Pałasz, Ewelina; Bąk, Agnieszka; Gąsiorowska, Anna; Niewiadomska, Grażyna

2017-01-04

Glial cells and neurotrophins play an important role in maintaining homeostasis of the CNS. Disturbances of their function can lead to a number of nervous system diseases, including Parkinson's disease (PD). Current clinical studies provide evidence that moderate physical activity adapted to the health status of PD patients can support pharmacological treatment, slow down the onset of motor impairments, and extend the patients period of independence. Physical activity, by stimulating the production and release of endogenous trophic factors, prevents the neurodegeneration of dopaminergic neurons via inhibition of inflammatory processes and the reduction of oxidative stress. The aim of this study is to present the current state of knowledge for the anti-inflammatory and neuroprotective properties of physical activity as a supportive therapy in Parkinson's disease.

Assessment of phytoplankton and environmental variables for water quality and trophic state classification in the Gemlik Gulf, Marmara Sea (Turkey).

PubMed

Balci, Muharrem; Balkis, Neslihan

2017-02-15

Phytoplankton assemblages related to environmental factors and ecological status of the Gemlik Gulf were investigated between June 2010 and May 2011. A total 155 phytoplankton species were detected and 6 taxa (Amphisolenia laticincta, Archaeperidinium minutum, Cochlodinium sp., Gynogonadinium aequatoriale, Heterocapsa rotundata and Metaphalacroma sp.) were new records for the Turkish Seas. The lowest and highest total phytoplankton abundance among the sampling units (depths) was recorded in April 2011 (7.4×10 3 cellsL -1 ) and July 2010 (251.8×10 3 cellsL -1 ). Local small patches of visible red tide events were detected especially in the gulf, although a phytoplankton bloom was not observed. The water column was well stratified in the early autumn and well mixed in the early spring according to stratification index values. Surface nutrient concentrations increased especially at stations located inside of the gulf. The limiting effect of silicate was observed in early, mid-summer and early winter periods while the nitrogen was the limiting nutrient in the gulf during the whole sampling period. In the Gulf, low water quality-high mesotrophic and bad water quality-eutrophic status, high quality and low trophic level were generally detected according to Chl a, dissolved oxygen and trophic index. However, indices developed to determine the trophic level and water quality of the Mediterranean Sea can give unexpected results about the current environmental quality status when it is applied to the Marmara Sea which has limited photic zone by the halocline-pycnocline and thermocline. Copyright © 2016 Elsevier Ltd. All rights reserved.

Mesenchymal stem cells: environmentally responsive therapeutics for regenerative medicine

PubMed Central

Murphy, Matthew B; Moncivais, Kathryn; Caplan, Arnold I

2013-01-01

Mesenchymal stem cells (MSCs) are partially defined by their ability to differentiate into tissues including bone, cartilage and adipose in vitro, but it is their trophic, paracrine and immunomodulatory functions that may have the greatest therapeutic impact in vivo. Unlike pharmaceutical treatments that deliver a single agent at a specific dose, MSCs are site regulated and secrete bioactive factors and signals at variable concentrations in response to local microenvironmental cues. Significant progress has been made in understanding the biochemical and metabolic mechanisms and feedback associated with MSC response. The anti-inflammatory and immunomodulatory capacity of MSC may be paramount in the restoration of localized or systemic conditions for normal healing and tissue regeneration. Allogeneic MSC treatments, categorized as a drug by regulatory agencies, have been widely pursued, but new studies demonstrate the efficacy of autologous MSC therapies, even for individuals affected by a disease state. Safety and regulatory concerns surrounding allogeneic cell preparations make autologous and minimally manipulated cell therapies an attractive option for many regenerative, anti-inflammatory and autoimmune applications. PMID:24232253

Trophic niche of squids: Insights from isotopic data in marine systems worldwide

NASA Astrophysics Data System (ADS)

Navarro, Joan; Coll, Marta; Somes, Christoper J.; Olson, Robert J.

2013-10-01

Cephalopods are an important prey resource for fishes, seabirds, and marine mammals, and are also voracious predators on crustaceans, fishes, squid and zooplankton. Because of their high feeding rates and abundance, squids have the potential to exert control on the recruitment of commercially important fishes. In this review, we synthesize the available information for two intrinsic markers (δ15N and δ13C isotopic values) in squids for all oceans and several types of ecosystems to obtain a global view of the trophic niches of squids in marine ecosystems. In particular, we aimed to examine whether the trophic positions and trophic widths of squid species vary among oceans and ecosystem types. To correctly compare across systems, we adjusted squid δ15N values for the isotopic variability of phytoplankton at the base of the food web provided by an ocean circulation-biogeochemistry-isotope model. Studies that focused on the trophic ecology of squids using isotopic techniques were few, and most of the information on squids was from studies on their predators. Our results showed that squids occupy a large range of trophic positions and exploit a large range of trophic resources, reflecting the versatility of their feeding behavior and confirming conclusions from food-web models. Clear differences in both trophic position and trophic width were found among oceans and ecosystem types. The study also reinforces the importance of considering the natural variation in isotopic values when comparing the isotopic values of consumers inhabiting different ecosystems.

Ecosystem Responses To Plant Phenology Across Scales And Trophic Levels

NASA Astrophysics Data System (ADS)

Stoner, D.; Sexton, J. O.; Nagol, J. R.; Ironside, K.; Choate, D.; Longshore, K.; Edwards, T., Jr.

2015-12-01

Plant phenology in arid and semi-arid ecoregions is constrained by water availability and governs the life history characteristics of primary and secondary consumers. We related the behavior, demography, and distribution of mammalian herbivores and their principal predator to remotely sensed vegetation and climatological indices across the western United States for the period 2000-2014. Across scales, terrain and topographic position moderates the effects of climatological drought on primary productivity, resulting in differential susceptibility among plant functional types to water stress. At broad scales, herbivores tie parturition to moist sites during the period of maximum increase in local forage production. Consequently, juvenile mortality is highest in regions of extreme phenological variability. Although decoupled from primary production by one or more trophic levels, carnivore home range size and density is negatively correlated to plant productivity and growing season length. At the finest scales, predation influences the behavior of herbivore prey through compromised habitat selection, in which maternal females trade nutritional benefits of high plant biomass for reduced mortality risk associated with increased visibility. Climate projections for the western United States predict warming combined with shifts in the timing and form of precipitation. Our analyses suggest that these changes will propagate through trophic levels as increased phenological variability and shifts in plant distributions, larger consumer home ranges, altered migration behavior, and generally higher volatility in wildlife populations. Combined with expansion and intensification of human land use across the region, these changes will likely have economic implications stemming from increased human-wildlife conflict (e.g., crop damage, vehicle collisions) and changes in wildlife-related tourism.

Trophic State Evolution and Nutrient Trapping Capacity in a Transboundary Subtropical Reservoir: A 25-Year Study

NASA Astrophysics Data System (ADS)

Cunha, Davi Gasparini Fernandes; Benassi, Simone Frederigi; de Falco, Patrícia Bortoletto; do Carmo Calijuri, Maria

2016-03-01

Artificial reservoirs have been used for drinking water supply, other human activities, flood control and pollution abatement worldwide, providing overall benefits to downstream water quality. Most reservoirs in Brazil were built during the 1970s, but their long-term patterns of trophic status, water chemistry, and nutrient removal are still not very well characterized. We aimed to evaluate water quality time series (1985-2010) data from the riverine and lacustrine zones of the transboundary Itaipu Reservoir (Brazil/Paraguay). We examined total phosphorus and nitrogen, chlorophyll a concentrations, water transparency, and phytoplankton density to look for spatial and temporal trends and correlations with trophic state evolution and nutrient retention. There was significant temporal and spatial water quality variation ( P < 0.01, ANCOVA). The results indicated that the water quality and structure of the reservoir were mainly affected by one internal force (hydrodynamics) and one external force (upstream cascading reservoirs). Nutrient and chlorophyll a concentrations tended to be lower in the lacustrine zone and decreased over the 25-year timeframe. Reservoir operational features seemed to be limiting primary production and phytoplankton development, which exhibited a maximum density of 6050 org/mL. The relatively small nutrient concentrations in the riverine zone were probably related to the effect of the cascade reservoirs upstream of Itaipu and led to relatively low removal percentages. Our study suggested that water quality problems may be more pronounced immediately after the filling phase of the artificial reservoirs, associated with the initial decomposition of drowned vegetation at the very beginning of reservoir operation.

Trophic State Evolution and Nutrient Trapping Capacity in a Transboundary Subtropical Reservoir: A 25-Year Study.

PubMed

Cunha, Davi Gasparini Fernandes; Benassi, Simone Frederigi; de Falco, Patrícia Bortoletto; Calijuri, Maria do Carmo

2016-03-01

Artificial reservoirs have been used for drinking water supply, other human activities, flood control and pollution abatement worldwide, providing overall benefits to downstream water quality. Most reservoirs in Brazil were built during the 1970s, but their long-term patterns of trophic status, water chemistry, and nutrient removal are still not very well characterized. We aimed to evaluate water quality time series (1985-2010) data from the riverine and lacustrine zones of the transboundary Itaipu Reservoir (Brazil/Paraguay). We examined total phosphorus and nitrogen, chlorophyll a concentrations, water transparency, and phytoplankton density to look for spatial and temporal trends and correlations with trophic state evolution and nutrient retention. There was significant temporal and spatial water quality variation (P < 0.01, ANCOVA). The results indicated that the water quality and structure of the reservoir were mainly affected by one internal force (hydrodynamics) and one external force (upstream cascading reservoirs). Nutrient and chlorophyll a concentrations tended to be lower in the lacustrine zone and decreased over the 25-year timeframe. Reservoir operational features seemed to be limiting primary production and phytoplankton development, which exhibited a maximum density of 6050  org/mL. The relatively small nutrient concentrations in the riverine zone were probably related to the effect of the cascade reservoirs upstream of Itaipu and led to relatively low removal percentages. Our study suggested that water quality problems may be more pronounced immediately after the filling phase of the artificial reservoirs, associated with the initial decomposition of drowned vegetation at the very beginning of reservoir operation.

Eutrophication in the Yunnan Plateau lakes: the influence of lake morphology, watershed land use, and socioeconomic factors.

PubMed

Liu, Wenzhi; Li, Siyue; Bu, Hongmei; Zhang, Quanfa; Liu, Guihua

2012-03-01

Lakes play an important role in socioeconomic development and ecological balance in China, but their water quality has deteriorated considerably in recent decades. In this study, we investigated the spatial-temporal variations of eutrophication parameters (secchi depth, total nitrogen, total phosphorus, chemical oxygen demand, chlorophyll-a, trophic level index, and trophic state index) and their relationships with lake morphology, watershed land use, and socioeconomic factors in the Yunnan Plateau lakes. Results indicated that about 77.8% of lakes were eutrophic according to trophic state index. The plateau lakes showed spatial variations in water quality and could be classified into high-nutrient and low-nutrient groups. However, because watersheds were dominated by vegetation, all eutrophication parameters except chlorophyll-a showed no significant differences between the wet and dry seasons. Lake depth, water residence time, volume, and percentage of built-up land were significantly related to several eutrophication parameters. Agricultural land use and social-economic factors had no significant correlation with all eutrophication parameters. Stepwise regression analyses demonstrated that lake depth and water residence time accounted for 73.8% to 87.6% of the spatial variation of single water quality variables, respectively. Redundancy analyses indicated that lake morphology, watershed land use, and socioeconomic factors together explained 74.3% of the spatial variation in overall water quality. The results imply that water quality degradation in the plateau lakes may be mainly due to the domestic and industrial wastewaters. This study will improve our understanding of the determinants of lake water quality and help to design efficient strategies for controlling eutrophication in the plateau region.

Prey size diversity hinders biomass trophic transfer and predator size diversity promotes it in planktonic communities

PubMed Central

García-Comas, Carmen; Sastri, Akash R.; Ye, Lin; Chang, Chun-Yi; Lin, Fan-Sian; Su, Min-Sian; Gong, Gwo-Ching; Hsieh, Chih-hao

2016-01-01

Body size exerts multiple effects on plankton food-web interactions. However, the influence of size structure on trophic transfer remains poorly quantified in the field. Here, we examine how the size diversity of prey (nano-microplankton) and predators (mesozooplankton) influence trophic transfer efficiency (using biomass ratio as a proxy) in natural marine ecosystems. Our results support previous studies on single trophic levels: transfer efficiency decreases with increasing prey size diversity and is enhanced with greater predator size diversity. We further show that communities with low nano-microplankton size diversity and high mesozooplankton size diversity tend to occur in warmer environments with low nutrient concentrations, thus promoting trophic transfer to higher trophic levels in those conditions. Moreover, we reveal an interactive effect of predator and prey size diversities: the positive effect of predator size diversity becomes influential when prey size diversity is high. Mechanistically, the negative effect of prey size diversity on trophic transfer may be explained by unicellular size-based metabolic constraints as well as trade-offs between growth and predation avoidance with size, whereas increasing predator size diversity may enhance diet niche partitioning and thus promote trophic transfer. These findings provide insights into size-based theories of ecosystem functioning, with implications for ecosystem predictive models. PMID:26865298

Trophic transfer of microplastics in aquatic ecosystems: Identifying critical research needs.

PubMed

Au, Sarah Y; Lee, Cindy M; Weinstein, John E; van den Hurk, Peter; Klaine, Stephen J

2017-05-01

To evaluate the process of trophic transfer of microplastics, it is important to consider various abiotic and biotic factors involved in their ingestion, egestion, bioaccumulation, and biomagnification. Toward this end, a review of the literature on microplastics has been conducted to identify factors influencing their uptake and absorption; their residence times in organisms and bioaccumulation; the physical effects of their aggregation in gastrointestinal tracts; and their potential to act as vectors for the transfer of other contaminants. Limited field evidence from higher trophic level organisms in a variety of habitats suggests that trophic transfer of microplastics may be a common phenomenon and occurs concurrently with direct ingestion. Critical research needs include standardizing methods of field characterization of microplastics, quantifying uptake and depuration rates in organisms at different trophic levels, quantifying the influence that microplastics have on the uptake and/or depuration of environmental contaminants among different trophic levels, and investigating the potential for biomagnification of microplastic-associated chemicals. More integrated approaches involving computational modeling are required to fully assess trophic transfer of microplastics. Integr Environ Assess Manag 2017;13:505-509. © 2017 SETAC. © 2017 SETAC.

Spider foraging strategy affects trophic cascades under natural and drought conditions.

PubMed

Liu, Shengjie; Chen, Jin; Gan, Wenjin; Schaefer, Douglas; Gan, Jianmin; Yang, Xiaodong

2015-07-23

Spiders can cause trophic cascades affecting litter decomposition rates. However, it remains unclear how spiders with different foraging strategies influence faunal communities, or present cascading effects on decomposition. Furthermore, increased dry periods predicted in future climates will likely have important consequences for trophic interactions in detritus-based food webs. We investigated independent and interactive effects of spider predation and drought on litter decomposition in a tropical forest floor. We manipulated densities of dominant spiders with actively hunting or sit-and-wait foraging strategies in microcosms which mimicked the tropical-forest floor. We found a positive trophic cascade on litter decomposition was triggered by actively hunting spiders under ambient rainfall, but sit-and-wait spiders did not cause this. The drought treatment reversed the effect of actively hunting spiders on litter decomposition. Under drought conditions, we observed negative trophic cascade effects on litter decomposition in all three spider treatments. Thus, reduced rainfall can alter predator-induced indirect effects on lower trophic levels and ecosystem processes, and is an example of how such changes may alter trophic cascades in detritus-based webs of tropical forests.

Spider foraging strategy affects trophic cascades under natural and drought conditions

PubMed Central

Liu, Shengjie; Chen, Jin; Gan, Wenjin; Schaefer, Douglas; Gan, Jianmin; Yang, Xiaodong

2015-01-01

Spiders can cause trophic cascades affecting litter decomposition rates. However, it remains unclear how spiders with different foraging strategies influence faunal communities, or present cascading effects on decomposition. Furthermore, increased dry periods predicted in future climates will likely have important consequences for trophic interactions in detritus-based food webs. We investigated independent and interactive effects of spider predation and drought on litter decomposition in a tropical forest floor. We manipulated densities of dominant spiders with actively hunting or sit-and-wait foraging strategies in microcosms which mimicked the tropical-forest floor. We found a positive trophic cascade on litter decomposition was triggered by actively hunting spiders under ambient rainfall, but sit-and-wait spiders did not cause this. The drought treatment reversed the effect of actively hunting spiders on litter decomposition. Under drought conditions, we observed negative trophic cascade effects on litter decomposition in all three spider treatments. Thus, reduced rainfall can alter predator-induced indirect effects on lower trophic levels and ecosystem processes, and is an example of how such changes may alter trophic cascades in detritus-based webs of tropical forests. PMID:26202370

Trophic transfer of metals along freshwater food webs: Evidence of cadmium biomagnification in nature

USGS Publications Warehouse

Croteau, M.-N.; Luoma, S.N.; Stewart, A.R.

2005-01-01

We conducted a study with cadmium (Cd) and copper (Cu) in the delta of San Francisco Bay, using nitrogen and carbon stable isotopes to identify trophic position and food web structure. Cadmium is progressively enriched among trophic levels in discrete epiphyte-based food webs composed of macrophyte-dwelling invertebrates (the first link being epiphytic algae) and fishes (the first link being gobies). Cadmium concentrations were biomagnified 15 times within the scope of two trophic links in both food webs. Trophic enrichment in invertebrates was twice that of fishes. No tendency toward trophic-level enrichment was observed for Cu, regardless of whether organisms were sorted by food web or treated on a taxonomic basis within discrete food webs. The greatest toxic effects of Cd are likely to occur with increasing trophic positions, where animals are ingesting Cd-rich prey (or food). In Franks Tract this occurs within discrete food chains composed of macrophyte-dwelling invertebrates or fishes inhabiting submerged aquatic vegetation. Unraveling ecosystem complexity is necessary before species most exposed and at risk can be identified. ?? 2005, by the American Society of Limnology and Oceanography, Inc.

Overfishing and the replacement of demersal finfish by shellfish: an example from the English Channel.

PubMed

Molfese, Carlotta; Beare, Doug; Hall-Spencer, Jason M

2014-01-01

The worldwide depletion of major fish stocks through intensive industrial fishing is thought to have profoundly altered the trophic structure of marine ecosystems. Here we assess changes in the trophic structure of the English Channel marine ecosystem using a 90-year time-series (1920-2010) of commercial fishery landings. Our analysis was based on estimates of the mean trophic level (mTL) of annual landings and the Fishing-in-Balance index (FiB). Food webs of the Channel ecosystem have been altered, as shown by a significant decline in the mTL of fishery landings whilst increases in the FiB index suggest increased fishing effort and fishery expansion. Large, high trophic level species (e.g. spurdog, cod, ling) have been increasingly replaced by smaller, low trophic level fish (e.g. small spotted catsharks) and invertebrates (e.g. scallops, crabs and lobster). Declining trophic levels in fisheries catches have occurred worldwide, with fish catches progressively being replaced by invertebrates. We argue that a network of fisheries closures would help rebalance the trophic status of the Channel and allow regeneration of marine ecosystems.

Exercise-induced neuroprotective effects on neurodegenerative diseases: the key role of trophic factors.

PubMed

Campos, Carlos; Rocha, Nuno Barbosa F; Lattari, Eduardo; Paes, Flávia; Nardi, António E; Machado, Sérgio

2016-06-01

Age-related neurodegenerative disorders, like Alzheimer's or Parkinson's disease, are becoming a major issue to public health care. Currently, there is no effective pharmacological treatment to address cognitive impairment in these patients. Here, we aim to explore the role of exercise-induced trophic factor enhancement in the prevention or delay of cognitive decline in patients with neurodegenerative diseases. There is a significant amount of evidence from animal and human studies that links neurodegenerative related cognitive deficits with changes on brain and peripheral trophic factor levels. Several trials with elderly individuals and patients with neurodegenerative diseases report exercise induced cognitive improvements and changes on trophic factor levels including BDNF, IGF-I, among others. Further studies with healthy aging and clinical populations are needed to understand how diverse exercise interventions produce different variations in trophic factor signaling. Genetic profiles and potential confounders regarding trophic factors should also be addressed in future trials.

A single exposure to cocaine during development elicits regionally-selective changes in basal basic Fibroblast Growth Factor (FGF-2) gene expression and alters the trophic response to a second injection.

PubMed

Giannotti, Giuseppe; Caffino, Lucia; Malpighi, Chiara; Melfi, Simona; Racagni, Giorgio; Fumagalli, Fabio

2015-02-01

During adolescence, the brain is maturing and more sensitive to drugs of abuse that can influence its developmental trajectory. Recently, attention has been focused on basic fibroblast growth factor (FGF-2) given that its administration early in life enhances the acquisition of cocaine self-administration and sensitization at adulthood (Turner et al. (Pharmacol Biochem Behav 92:100-4, 2009), Clinton et al. (Pharmacol Biochem Behav103:6-17, 2012)). Additionally, we found that abstinence from adolescent cocaine exposure long lastingly dysregulates FGF-2 transcription (Giannotti et al. (Psychopharmacology (Berl) 225:553-60, 2013 ). The objectives of the study are to evaluate if (1) a single injection of cocaine (20 mg/kg) at postnatal day 35 alters FGF-2 messenger RNA (mRNA) levels and (2) the first injection influences the trophic response to a second injection (10 mg/kg) provided 24 h or 7 days later. We found regional differences in the FGF-2 expression pattern as either the first or the second injection of cocaine by themselves upregulated FGF-2 mRNA in the medial prefrontal cortex and nucleus accumbens while downregulating it in the hippocampus. The first injection influences the trophic response of the second. Of note, 24 h after the first injection, accumbal and hippocampal FGF-2 changes produced by cocaine in saline-pretreated rats were prevented in cocaine-pretreated rats. Conversely, in the medial prefrontal cortex and hippocampus 7 days after the first injection, the cocaine-induced FGF-2 changes were modified by the subsequent exposure to the psychostimulant. These findings show that a single cocaine injection is sufficient to produce enduring changes in the adolescent brain and indicate that early cocaine priming alters the mechanisms regulating the trophic response in a brain region-specific fashion.

Trophic Scaling and Occupancy Analysis Reveals a Lion Population Limited by Top-Down Anthropogenic Pressure in the Limpopo National Park, Mozambique

PubMed Central

Everatt, Kristoffer T.; Andresen, Leah; Somers, Michael J.

2014-01-01

The African lion (Panthera Leo) has suffered drastic population and range declines over the last few decades and is listed by the IUCN as vulnerable to extinction. Conservation management requires reliable population estimates, however these data are lacking for many of the continent's remaining populations. It is possible to estimate lion abundance using a trophic scaling approach. However, such inferences assume that a predator population is subject only to bottom-up regulation, and are thus likely to produce biased estimates in systems experiencing top-down anthropogenic pressures. Here we provide baseline data on the status of lions in a developing National Park in Mozambique that is impacted by humans and livestock. We compare a direct density estimate with an estimate derived from trophic scaling. We then use replicated detection/non-detection surveys to estimate the proportion of area occupied by lions, and hierarchical ranking of covariates to provide inferences on the relative contribution of prey resources and anthropogenic factors influencing lion occurrence. The direct density estimate was less than 1/3 of the estimate derived from prey resources (0.99 lions/100 km2 vs. 3.05 lions/100 km2). The proportion of area occupied by lions was Ψ = 0.439 (SE = 0.121), or approximately 44% of a 2 400 km2 sample of potential habitat. Although lions were strongly predicted by a greater probability of encountering prey resources, the greatest contributing factor to lion occurrence was a strong negative association with settlements. Finally, our empirical abundance estimate is approximately 1/3 of a published abundance estimate derived from opinion surveys. Altogether, our results describe a lion population held below resource-based carrying capacity by anthropogenic factors and highlight the limitations of trophic scaling and opinion surveys for estimating predator populations exposed to anthropogenic pressures. Our study provides the first empirical quantification of a population that future change can be measured against. PMID:24914934

Trophic scaling and occupancy analysis reveals a lion population limited by top-down anthropogenic pressure in the Limpopo National Park, Mozambique.

PubMed

Everatt, Kristoffer T; Andresen, Leah; Somers, Michael J

2014-01-01

The African lion (Panthera Leo) has suffered drastic population and range declines over the last few decades and is listed by the IUCN as vulnerable to extinction. Conservation management requires reliable population estimates, however these data are lacking for many of the continent's remaining populations. It is possible to estimate lion abundance using a trophic scaling approach. However, such inferences assume that a predator population is subject only to bottom-up regulation, and are thus likely to produce biased estimates in systems experiencing top-down anthropogenic pressures. Here we provide baseline data on the status of lions in a developing National Park in Mozambique that is impacted by humans and livestock. We compare a direct density estimate with an estimate derived from trophic scaling. We then use replicated detection/non-detection surveys to estimate the proportion of area occupied by lions, and hierarchical ranking of covariates to provide inferences on the relative contribution of prey resources and anthropogenic factors influencing lion occurrence. The direct density estimate was less than 1/3 of the estimate derived from prey resources (0.99 lions/100 km² vs. 3.05 lions/100 km²). The proportion of area occupied by lions was Ψ = 0.439 (SE = 0.121), or approximately 44% of a 2,400 km2 sample of potential habitat. Although lions were strongly predicted by a greater probability of encountering prey resources, the greatest contributing factor to lion occurrence was a strong negative association with settlements. Finally, our empirical abundance estimate is approximately 1/3 of a published abundance estimate derived from opinion surveys. Altogether, our results describe a lion population held below resource-based carrying capacity by anthropogenic factors and highlight the limitations of trophic scaling and opinion surveys for estimating predator populations exposed to anthropogenic pressures. Our study provides the first empirical quantification of a population that future change can be measured against.

Diet Composition and Trophic Ecology of Northeast Pacific Ocean Sharks.

PubMed

Bizzarro, Joseph J; Carlisle, Aaron B; Smith, Wade D; Cortés, Enric

Although there is a general perception of sharks as large pelagic, apex predators, most sharks are smaller, meso- and upper-trophic level predators that are associated with the seafloor. Among 73 shark species documented in the eastern North Pacific (ENP), less than half reach maximum lengths >200cm, and 78% occur in demersal or benthic regions of the continental shelf or slope. Most small (≤200cm) species (e.g., houndsharks) and demersal, nearshore juveniles of larger species (e.g., requiem sharks) consume small teleosts and decapod crustaceans, whereas large species in pelagic coastal and oceanic environments feed on large teleosts and squids. Several large, pelagic apex predator species occur in the ENP, but the largest species (i.e., Basking Shark, Whale Shark) consume zooplankton or small nekton. Size-based dietary variability is substantial for many species, and segregation of juvenile and adult foraging habitats also is common (e.g., Horn Shark, Shortfin Mako). Temporal dietary differences are most pronounced for temperate, nearshore species with wide size ranges, and least pronounced for smaller species in extreme latitudes and deep-water regions. Sympatric sharks often occupy various trophic positions, with resource overlap differing by space and time and some sharks serving as prey to other species. Most coastal species remain in the same general region over time and feed opportunistically on variable prey inputs (e.g., season migrations, spawning, or recruitment events), whereas pelagic, oceanic species actively seek hot spots of prey abundance that are spatiotemporally variable. The influence of sharks on ecosystem structure and regulation has been downplayed compared to that of large teleosts species with higher per capita consumption rates (e.g., tunas, billfishes). However, sharks also exert indirect influences on prey populations by causing behavioural changes that may result in restricted ranges and reduced fitness. Except for food web modelling efforts in Alaskan waters, the trophic impacts of sharks are poorly incorporated into current ecosystem approaches to fisheries management in the NEP. © 2017 Elsevier Ltd. All rights reserved.

Acidification in the Adirondacks: Defining the Biota in trophic Levels of 30 Chemically Diverse Acid-Impacted Lakes

EPA Science Inventory

The Adirondack Mountains in New York State have a varied surficial geology and chemically diverse surface waters that are among the most impacted by acid deposition in the U.S. No single Adirondack investigation has been comprehensive in defining the effects of acidification on ...

Trophic State and Toxic Cyanobacteria Density in Optimization Modeling of Multi-Reservoir Water Resource Systems

PubMed Central

Sulis, Andrea; Buscarinu, Paola; Soru, Oriana; Sechi, Giovanni M.

2014-01-01

The definition of a synthetic index for classifying the quality of water bodies is a key aspect in integrated planning and management of water resource systems. In previous works [1,2], a water system optimization modeling approach that requires a single quality index for stored water in reservoirs has been applied to a complex multi-reservoir system. Considering the same modeling field, this paper presents an improved quality index estimated both on the basis of the overall trophic state of the water body and on the basis of the density values of the most potentially toxic Cyanobacteria. The implementation of the index into the optimization model makes it possible to reproduce the conditions limiting water use due to excessive nutrient enrichment in the water body and to the health hazard linked to toxic blooms. The analysis of an extended limnological database (1996–2012) in four reservoirs of the Flumendosa-Campidano system (Sardinia, Italy) provides useful insights into the strengths and limitations of the proposed synthetic index. PMID:24759172

Interannual and long-term changes in the trophic state of a multibasin lake: Effects of morphology, climate, winter aeration, and beaver activity

USGS Publications Warehouse

Robertson, Dale M.; Rose, William; Reneau, Paul C.

2016-01-01

Little St. Germain Lake (LSG), a relatively pristine multibasin lake in Wisconsin, USA, was examined to determine how morphologic (internal), climatic (external), anthropogenic (winter aeration), and natural (beaver activity) factors affect the trophic state (phosphorus, P; chlorophyll, CHL; and Secchi depth, SD) of each of its basins. Basins intercepting the main flow and external P sources had highest P and CHL and shallowest SD. Internal loading in shallow, polymictic basins caused P and CHL to increase and SD to decrease as summer progressed. Winter aeration used to eliminate winterkill increased summer internal P loading and decreased water quality, while reductions in upstream beaver impoundments had little effect on water quality. Variations in air temperature and precipitation affected each basin differently. Warmer air temperatures increased productivity throughout the lake and decreased clarity in less eutrophic basins. Increased precipitation increased P in the basins intercepting the main flow but had little effect on the isolated deep West Bay. These relations are used to project effects of future climatic changes on LSG and other temperate lakes.

An assessment of the trophic structure of the Bay of Biscay continental shelf food web: Comparing estimates derived from an ecosystem model and isotopic data

NASA Astrophysics Data System (ADS)

Lassalle, G.; Chouvelon, T.; Bustamante, P.; Niquil, N.

2014-01-01

Comparing outputs of ecosystem models with estimates derived from experimental and observational approaches is important in creating valuable feedback for model construction, analyses and validation. Stable isotopes and mass-balanced trophic models are well-known and widely used as approximations to describe the structure of food webs, but their consistency has not been properly established as attempts to compare these methods remain scarce. Model construction is a data-consuming step, meaning independent sets for validation are rare. Trophic linkages in the French continental shelf of the Bay of Biscay food webs were recently investigated using both methodologies. Trophic levels for mono-specific compartments representing small pelagic fish and marine mammals and multi-species functional groups corresponding to demersal fish and cephalopods, derived from modelling, were compared with trophic levels calculated from independent carbon and nitrogen isotope ratios. Estimates of the trophic niche width of those species, or groups of species, were compared between these two approaches as well. A significant and close-to-one positive (rSpearman2 = 0.72 , n = 16, p < 0.0001) correlation was found between trophic levels estimated by Ecopath modelling and those derived from isotopic signatures. Differences between estimates were particularly low for mono-specific compartments. No clear relationship existed between indices of trophic niche width derived from both methods. Given the wide recognition of trophic levels as a useful concept in ecosystem-based fisheries management, propositions were made to further combine these two approaches.

Toward a trophic theory of species diversity

PubMed Central

Terborgh, John W.

2015-01-01

Efforts to understand the ecological regulation of species diversity via bottom-up approaches have failed to yield a consensus theory. Theories based on the alternative of top-down regulation have fared better. Paine’s discovery of keystone predation demonstrated that the regulation of diversity via top-down forcing could be simple, strong, and direct, yet ecologists have persistently failed to perceive generality in Paine’s result. Removing top predators destabilizes many systems and drives transitions to radically distinct alternative states. These transitions typically involve community reorganization and loss of diversity, implying that top-down forcing is crucial to diversity maintenance. Contrary to the expectations of bottom-up theories, many terrestrial herbivores and mesopredators are capable of sustained order-of-magnitude population increases following release from predation, negating the assumption that populations of primary consumers are resource limited and at or near carrying capacity. Predation sensu lato (to include Janzen–Connell mortality agents) has been shown to promote diversity in a wide range of ecosystems, including rocky intertidal shelves, coral reefs, the nearshore ocean, streams, lakes, temperate and tropical forests, and arctic tundra. The compelling variety of these ecosystems suggests that top-down forcing plays a universal role in regulating diversity. This conclusion is further supported by studies showing that the reduction or absence of predation leads to diversity loss and, in the more dramatic cases, to catastrophic regime change. Here, I expand on the thesis that diversity is maintained by the interaction between predation and competition, such that strong top-down forcing reduces competition, allowing coexistence. PMID:26374788

The relative importance of water temperature and residence time in predicting cyanobacteria abundance in regulated rivers.

PubMed

Cha, YoonKyung; Cho, Kyung Hwa; Lee, Hyuk; Kang, Taegu; Kim, Joon Ha

2017-11-01

Despite a growing awareness of the problems associated with cyanobacterial blooms in rivers, and particularly in regulated rivers, the drivers of bloom formation and abundance in rivers are not well understood. We developed a Bayesian hierarchical model to assess the relative importance of predictors of summer cyanobacteria abundance, and to test whether the relative importance of each predictor varies by site, using monitoring data from 16 sites in the four major rivers of South Korea. The results suggested that temperature and residence time, but not nutrient levels, are important predictors of summer cyanobacteria abundance in rivers. Although the two predictors were of similar significance across the sites, the residence time was marginally better in accounting for the variation in cyanobacteria abundance. The model with spatial hierarchy demonstrated that temperature played a consistently significant role at all sites, and showed no effect from site-specific factors. In contrast, the importance of residence time varied significantly from site to site. This variation was shown to depend on the trophic state, indicated by the chlorophyll-a and total phosphorus levels. Our results also suggested that the magnitude of weir inflow is a key factor determining the cyanobacteria abundance under baseline conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

PCB Food Web Dynamics Quantify Nutrient and Energy Flow in Aquatic Ecosystems.

PubMed

McLeod, Anne M; Paterson, Gordon; Drouillard, Ken G; Haffner, G Douglas

2015-11-03

Measuring in situ nutrient and energy flows in spatially and temporally complex aquatic ecosystems represents a major ecological challenge. Food web structure, energy and nutrient budgets are difficult to measure, and it is becoming more important to quantify both energy and nutrient flow to determine how food web processes and structure are being modified by multiple stressors. We propose that polychlorinated biphenyl (PCB) congeners represent an ideal tracer to quantify in situ energy and nutrient flow between trophic levels. Here, we demonstrate how an understanding of PCB congener bioaccumulation dynamics provides multiple direct measurements of energy and nutrient flow in aquatic food webs. To demonstrate this novel approach, we quantified nitrogen (N), phosphorus (P) and caloric turnover rates for Lake Huron lake trout, and reveal how these processes are regulated by both growth rate and fish life history. Although minimal nutrient recycling was observed in young growing fish, slow growing, older lake trout (>5 yr) recycled an average of 482 Tonnes·yr(-1) of N, 45 Tonnes·yr(-1) of P and assimilated 22 TJ yr(-1) of energy. Compared to total P loading rates of 590 Tonnes·yr(-1), the recycling of primarily bioavailable nutrients by fish plays an important role regulating the nutrient states of oligotrophic lakes.

Cadmium transfer and detoxification mechanisms in a soil-mulberry-silkworm system: phytoremediation potential.

PubMed

Zhou, Lingyun; Zhao, Ye; Wang, Shuifeng

2015-11-01

Phytoremediation has been proven to be an environmentally sound alternative for the recovery of contaminated soils, and the economic profit that comes along with the process might stimulate its field use. This study investigated cadmium (Cd) transfer and detoxification mechanisms in a soil-mulberry-silkworm system to estimate the suitability of the mulberry and silkworm as an alternative method for the remediation of Cd-polluted soil; it also explored the underlying mechanisms regulating the trophic transfer of Cd. The results show that both the mulberry and silkworm have high Cd tolerance. The transfer factor suggests that the mulberry has high potential for Cd extraction from polluted soil. The subcellular distribution and chemical forms of Cd in mulberry leaves show that cell wall deposition and vacuolar compartmentalization play important role in Cd tolerance. In the presence of increasing Cd concentrations in silkworm food, detoxification mechanisms (excretion and homeostasis) were activated so that excess Cd was excreted in fecal balls, and metallothionein levels in the mid-gut, the posterior of the silk gland, and the fat body of silkworms were enhanced. And, the Cd concentrations in silk are at a low level, ranging from 0.02 to 0.21 mg kg(-1). Therefore, these mechanisms of detoxification can regulate Cd trophic transfer, and mulberry planting and silkworm breeding has high phytoremediation potential for Cd-contaminated soil.

Herbivore-initiated interaction cascades and their modulation by productivity in an African savanna

PubMed Central

Pringle, Robert M.; Young, Truman P.; Rubenstein, Daniel I.; McCauley, Douglas J.

2007-01-01

Despite conceptual recognition that indirect effects initiated by large herbivores are likely to have profound impacts on ecological community structure and function, the existing literature on indirect effects focuses largely on the role of predators. As a result, we know neither the frequency and extent of herbivore-initiated indirect effects nor the mechanisms that regulate their strength. We examined the effects of ungulates on taxa (plants, arthropods, and an insectivorous lizard) representing several trophic levels, using a series of large, long-term, ungulate-exclusion plots that span a landscape-scale productivity gradient in an African savanna. At each of six sites, lizards, trees, and the numerically dominant order of arthropods (Coleoptera) were more abundant in the absence of ungulates. The effect of ungulates on arthropods was mediated by herbaceous vegetation cover. The effect on lizards was simultaneously mediated by both tree density (lizard microhabitat) and arthropod abundance (lizard food). The magnitudes of the experimental effects on all response variables (trees, arthropods, and lizards) were negatively correlated with two distinct measures of primary productivity. These results demonstrate strong cascading effects of ungulates, both trophic and nontrophic, and support the hypothesis that productivity regulates the strength of these effects. Hence, the strongest indirect effects (and thus, the greatest risks to ecosystem integrity after large mammals are extirpated) are likely to occur in low-productivity habitats. PMID:17190823

Trophic factors from adipose tissue-derived multi-lineage progenitor cells promote cytodifferentiation of periodontal ligament cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sawada, Keigo; Takedachi, Masahide, E-mail: takedati@dent.osaka-u.ac.jp; Yamamoto, Satomi

Stem and progenitor cells are currently being investigated for their applicability in cell-based therapy for periodontal tissue regeneration. We recently demonstrated that the transplantation of adipose tissue-derived multi-lineage progenitor cells (ADMPCs) enhances periodontal tissue regeneration in beagle dogs. However, the molecular mechanisms by which transplanted ADMPCs induce periodontal tissue regeneration remain to be elucidated. In this study, trophic factors released by ADMPCs were examined for their paracrine effects on human periodontal ligament cell (HPDL) function. ADMPC conditioned medium (ADMPC-CM) up-regulated osteoblastic gene expression, alkaline phosphatase activity and calcified nodule formation in HPDLs, but did not significantly affect their proliferative response.more » ADMPCs secreted a number of growth factors, including insulin-like growth factor binding protein 6 (IGFBP6), hepatocyte growth factor and vascular endothelial growth factor. Among these, IGFBP6 was most highly expressed. Interestingly, the positive effects of ADMPC-CM on HPDL differentiation were significantly suppressed by transfecting ADMPCs with IGFBP6 siRNA. Our results suggest that ADMPCs transplanted into a defect in periodontal tissue release trophic factors that can stimulate the differentiation of HPDLs to mineralized tissue-forming cells, such as osteoblasts and cementoblasts. IGFBP6 may play crucial roles in ADMPC-induced periodontal regeneration. - Highlights: • ADMPC-derived humoral factors stimulate cytodifferentiation of HPDLs. • ADMPCs secret growth factors including IGFBP6, VEGF and HGF. • IGFBP6 is involved in the promotion effect of ADMPC-CM on HPDL cytodifferentiation.« less

Trophic magnification of PCBs and its relationship to the octanol-water partition coefficient

USGS Publications Warehouse

Walters, D.M.; Mills, M.A.; Cade, B.S.; Burkard, L.P.

2011-01-01

We investigated polychlorinated biphenyl (PCB) bioaccumulation relative to octanol-water partition coefficient (KOW) and organism trophic position (TP) at the Lake Hartwell Superfund site (South Carolina). We measured PCBs (127 congeners) and stable isotopes (??15N) in sediment, organic matter, phytoplankton, zooplankton, macroinvertebrates, and fish. TP, as calculated from ??15N, was significantly, positively related to PCB concentrations, and food web trophic magnification factors (TMFs) ranged from 1.5-6.6 among congeners. TMFs of individual congeners increased strongly with log KOW, as did the predictive power (r2) of individual TP-PCB regression models used to calculate TMFs. We developed log KOW-TMF models for eight food webs with vastly different environments (freshwater, marine, arctic, temperate) and species composition (cold- vs warmblooded consumers). The effect of KOW on congener TMFs varied strongly across food webs (model slopes 0.0-15.0) because the range of TMFs among studies was also highly variable. We standardized TMFs within studies to mean = 0, standard deviation (SD) = 1 to normalize for scale differences and found a remarkably consistent KOW effect on TMFs (no difference in model slopes among food webs). Our findings underscore the importance of hydrophobicity (as characterized by KOW) in regulating bioaccumulation of recalcitrant compounds in aquatic systems, and demonstrate that relationships between chemical KOW and bioaccumulation from field studies are more generalized than previously recognized. ?? This article not subject to U.S. Copyright. Published 2011 by the American Chemical Society.

Trophic magnification of PCBs and Its relationship to the octanol-water partition coefficient.

PubMed

Walters, David M; Mills, Marc A; Cade, Brian S; Burkard, Lawrence P

2011-05-01

We investigated polychlorinated biphenyl (PCB) bioaccumulation relative to octanol-water partition coefficient (K(OW)) and organism trophic position (TP) at the Lake Hartwell Superfund site (South Carolina). We measured PCBs (127 congeners) and stable isotopes (δ¹⁵N) in sediment, organic matter, phytoplankton, zooplankton, macroinvertebrates, and fish. TP, as calculated from δ¹⁵N, was significantly, positively related to PCB concentrations, and food web trophic magnification factors (TMFs) ranged from 1.5-6.6 among congeners. TMFs of individual congeners increased strongly with log K(OW), as did the predictive power (r²) of individual TP-PCB regression models used to calculate TMFs. We developed log K(OW)-TMF models for eight food webs with vastly different environments (freshwater, marine, arctic, temperate) and species composition (cold- vs warmblooded consumers). The effect of K(OW) on congener TMFs varied strongly across food webs (model slopes 0.0-15.0) because the range of TMFs among studies was also highly variable. We standardized TMFs within studies to mean = 0, standard deviation (SD) = 1 to normalize for scale differences and found a remarkably consistent K(OW) effect on TMFs (no difference in model slopes among food webs). Our findings underscore the importance of hydrophobicity (as characterized by K(OW)) in regulating bioaccumulation of recalcitrant compounds in aquatic systems, and demonstrate that relationships between chemical K(OW) and bioaccumulation from field studies are more generalized than previously recognized.

Breaking out of the comfort zone: El Niño-Southern Oscillation as a driver of trophic flows in a benthic consumer of the Humboldt Current ecosystem.

PubMed

Riascos, José M; Solís, Marco A; Pacheco, Aldo S; Ballesteros, Manuel

2017-06-28

The trophic flow of a species is considered a characteristic trait reflecting its trophic position and function in the ecosystem and its interaction with the environment. However, climate patterns are changing and we ignore how patterns of trophic flow are being affected. In the Humboldt Current ecosystem, arguably one of the most productive marine systems, El Niño-Southern Oscillation is the main source of interannual and longer-term variability. To assess the effect of this variability on trophic flow we built a 16-year series of mass-specific somatic production rate (P/B) of the Peruvian scallop ( Argopecten purpuratus ), a species belonging to a former tropical fauna that thrived in this cold ecosystem. A strong increase of the P/B ratio of this species was observed during nutrient-poor, warmer water conditions typical of El Niño, owing to the massive recruitment of fast-growing juvenile scallops. Trophic ecology theory predicts that when primary production is nutrient limited, the trophic flow of organisms occupying low trophic levels should be constrained (bottom-up control). For former tropical fauna thriving in cold, productive upwelling coastal zones, a short time of low food conditions but warm waters during El Niño could be sufficient to waken their ancestral biological features and display massive proliferations. © 2017 The Author(s).

Food web topology and parasites in the pelagic zone of a subarctic lake

USGS Publications Warehouse

Amundsen, Per-Arne; Lafferty, K.D.; Knudsen, R.; Primicerio, R.; Klemetsen, A.; Kuris, A.M.

2009-01-01

Parasites permeate trophic webs with their often complex life cycles, but few studies have included parasitism in food web analyses. Here we provide a highly resolved food web from the pelagic zone of a subarctic lake and explore how the incorporation of parasites alters the topology of the web. 2. Parasites used hosts at all trophic levels and increased both food-chain lengths and the total number of trophic levels. Their inclusion in the network analyses more than doubled the number of links and resulted in an increase in important food-web characteristics such as linkage density and connectance. 3. More than half of the parasite taxa were trophically transmitted, exploiting hosts at multiple trophic levels and thus increasing the degree of omnivory in the trophic web. 4. For trophically transmitted parasites, the number of parasite-host links exhibited a positive correlation with the linkage density of the host species, whereas no such relationship was seen for nontrophically transmitted parasites. Our findings suggest that the linkage density of free-living species affects their exposure to trophically transmitted parasites, which may be more likely to adopt highly connected species as hosts during the evolution of complex life cycles. 5. The study supports a prominent role for parasites in ecological networks and demonstrates that their incorporation may substantially alter considerations of food-web structure and functioning. ?? 2009 British Ecological Society.

Trophic modeling of the Northern Humboldt Current Ecosystem, Part I: Comparing trophic linkages under La Niña and El Niño conditions

NASA Astrophysics Data System (ADS)

Tam, Jorge; Taylor, Marc H.; Blaskovic, Verónica; Espinoza, Pepe; Michael Ballón, R.; Díaz, Erich; Wosnitza-Mendo, Claudia; Argüelles, Juan; Purca, Sara; Ayón, Patricia; Quipuzcoa, Luis; Gutiérrez, Dimitri; Goya, Elisa; Ochoa, Noemí; Wolff, Matthias

2008-10-01

The El Niño of 1997-98 was one of the strongest warming events of the past century; among many other effects, it impacted phytoplankton along the Peruvian coast by changing species composition and reducing biomass. While responses of the main fish resources to this natural perturbation are relatively well known, understanding the ecosystem response as a whole requires an ecotrophic multispecies approach. In this work, we construct trophic models of the Northern Humboldt Current Ecosystem (NHCE) and compare the La Niña (LN) years in 1995-96 with the El Niño (EN) years in 1997-98. The model area extends from 4°S-16°S and to 60 nm from the coast. The model consists of 32 functional groups of organisms and differs from previous trophic models of the Peruvian system through: (i) division of plankton into size classes to account for EN-associated changes and feeding preferences of small pelagic fish, (ii) increased division of demersal groups and separation of life history stages of hake, (iii) inclusion of mesopelagic fish, and (iv) incorporation of the jumbo squid ( Dosidicus gigas), which became abundant following EN. Results show that EN reduced the size and organization of energy flows of the NHCE, but the overall functioning (proportion of energy flows used for respiration, consumption by predators, detritus and export) of the ecosystem was maintained. The reduction of diatom biomass during EN forced omnivorous planktivorous fish to switch to a more zooplankton-dominated diet, raising their trophic level. Consequently, in the EN model the trophic level increased for several predatory groups (mackerel, other large pelagics, sea birds, pinnipeds) and for fishery catch. A high modeled biomass of macrozooplankton was needed to balance the consumption by planktivores, especially during EN condition when observed diatoms biomass diminished dramatically. Despite overall lower planktivorous fish catches, the higher primary production required-to-catch ratio implied a stronger ecological impact of the fishery and stresses the need for precautionary management of fisheries during and after EN. During EN energetic indicators such as the lower primary production/total biomass ratio suggest a more energetically efficient ecosystem, while reduced network indicators such as the cycling index and relative ascendency indicate of a less organized state of the ecosystem. Compared to previous trophic models of the NHCE we observed: (i) a shrinking of ecosystem size in term of energy flows, (ii) slight changes in overall functioning (proportion of energy flows used for respiration, consumption by predators and detritus), and (iii) the use of alternate pathways leading to a higher ecological impact of the fishery for planktivorous fish.

Evaluation of the ornithogenic influence on the trophic state of East Mediterranean wetland ecosystem using trend analysis.

PubMed

Litaor, M Iggy; Barnea, I; Reichmann, O; Zohar, I

2016-01-01

The Great Rift Valley portion of the East African-Eurasian Migratory Flyway is extremely important globally because of the numbers (>500 million) and diversity of seasonal traveling birds. The construction of the Agmon wetland (1.1km(2)) in the Hula Valley, Israel in 1994 and a change in crop type and rotation has attracted increasing number of Eurasian cranes (Grus grus) to winter in the wetland (>40,000 in 2014). The birds are fed in an area of 100ha and roost during the night in the wetland for protection from predators. Feeding practices have yielded an eco-tourism bonanza with over 400,000 visitors annually. However, this practice may have negative impacts on the trophic state of the wetland. We performed trend analyses using monthly means of selected constituents collected from mid-1994 to 2014. The temporal distribution of TN and TP concentrations in the inlets did not change with time. The concentrations of TN and TP in the outlet increased significantly during the earlier monitoring period. Kendall-Theil regression showed that TP concentrations in the outlet increased significantly from a monthly mean of 180μgL(-1) in 2010 to a monthly mean of 260μgL(-1) in 2014. Similarly, the results of chlorophyll a concentrations in the outlet showed a sharp upturn in the latter part of the series from a mean of 66mgL(-1) in 2010 to a mean of 122mgL(-1) in 2014. The concurrent increase of TP and chlorophyll a, the two most important parameters affecting a waterbody trophic index coincided with the observed increase in the number of roosting cranes in the wetland. Hence, we assume that the continued increases in TP concentrations could transform the wetland from a mild eutrophic to a permanent hypereutrophic state. Reducing the number of roosting cranes may prevent this from happening. Copyright © 2015 Elsevier B.V. All rights reserved.

[Trophic niche partitioning of pelagic sharks in Central Eastern Pacific inferred from stable isotope analysis.

PubMed

Li, Yun Kai; Gao, Xiao di; Wang, Lin Yu; Fang, Lin

2018-01-01

As the apex predators of the open ocean ecosystems, pelagic sharks play important roles in stabilizing the marine food web through top-down control. Stable isotope analysis is a powerful tool to investigate the feeding ecology. The carbon and nitrogen isotope ratios can be used to trace food source and evaluate the trophic position of marine organisms. In this study, the isotope values of 130 pelagic sharks from 8 species in Central Eastern Pacific were analyzed and their trophic position and niche were calculated to compare the intra/inter-specific resource partitioning in the Central Eastern Pacific ecosystem. The results exhibited significant differences in both carbon and nitrogen isotope values among the shark species. The trophic levels ranged from 4.3 to 5.4 in the Central Eastern Pacific shark community. The trophic niche of blue sharks and shortfin mako sharks showed no overlap with the other shark species, exhibiting unique ecological roles in the open ocean food web. These data highlighted the diverse roles among pelagic sharks, supporting previous findings that this species is not trophically redundant and the trophic niche of pelagic sharks can not be simply replaced by those of other top predator species.

Critical assessment and ramifications of a purported marine trophic cascade

NASA Astrophysics Data System (ADS)

Grubbs, R. Dean; Carlson, John K.; Romine, Jason G.; Curtis, Tobey H.; McElroy, W. David; McCandless, Camilla T.; Cotton, Charles F.; Musick, John A.

2016-02-01

When identifying potential trophic cascades, it is important to clearly establish the trophic linkages between predators and prey with respect to temporal abundance, demographics, distribution, and diet. In the northwest Atlantic Ocean, the depletion of large coastal sharks was thought to trigger a trophic cascade whereby predation release resulted in increased cownose ray abundance, which then caused increased predation on and subsequent collapse of commercial bivalve stocks. These claims were used to justify the development of a predator-control fishery for cownose rays, the “Save the Bay, Eat a Ray” fishery, to reduce predation on commercial bivalves. A reexamination of data suggests declines in large coastal sharks did not coincide with purported rapid increases in cownose ray abundance. Likewise, the increase in cownose ray abundance did not coincide with declines in commercial bivalves. The lack of temporal correlations coupled with published diet data suggest the purported trophic cascade is lacking the empirical linkages required of a trophic cascade. Furthermore, the life history parameters of cownose rays suggest they have low reproductive potential and their populations are incapable of rapid increases. Hypothesized trophic cascades should be closely scrutinized as spurious conclusions may negatively influence conservation and management decisions.

Comparative study of trophic organization of juvenile fish assemblages of three tidal creeks in a tropical semi-arid estuary.

PubMed

Figueiredo, G G A A; Pessanha, A L M

2016-07-01

A comparison of three tidal creeks assessed the effects of the hydrological regime on trophic organization in juvenile fish assemblages of 21 species in a tropical estuary in north-eastern Brazil. There were seven trophic guilds represented spatially. Zooplanktivore and zoobenthivore guilds dominated the lower estuary, whereas omnivores and detritivores dominated the upper estuary. In the rainy season, the zooplanktivore and omnivore guilds were more common throughout the estuary, but in the dry season, zoobenthivores and piscivores occurred throughout. The trophic organization results show that (1) there was a higher complexity in tidal creeks in the upper estuary compared with the first tidal creek in the lower region and (2) trophic linkages increased in the upper estuary, principally the number of omnivore and detritivore species. Spatial variation in trophic structure was primarily associated with differences in the location of the tidal creeks along the estuary, and this variability was partly attributed to fish species richness; the number of species increased towards the upper estuary, and additional species occupied different trophic levels or used additional resources. © 2015 The Fisheries Society of the British Isles.

Overfishing and the Replacement of Demersal Finfish by Shellfish: An Example from the English Channel

PubMed Central

Molfese, Carlotta; Beare, Doug; Hall-Spencer, Jason M.

2014-01-01

The worldwide depletion of major fish stocks through intensive industrial fishing is thought to have profoundly altered the trophic structure of marine ecosystems. Here we assess changes in the trophic structure of the English Channel marine ecosystem using a 90-year time-series (1920–2010) of commercial fishery landings. Our analysis was based on estimates of the mean trophic level (mTL) of annual landings and the Fishing-in-Balance index (FiB). Food webs of the Channel ecosystem have been altered, as shown by a significant decline in the mTL of fishery landings whilst increases in the FiB index suggest increased fishing effort and fishery expansion. Large, high trophic level species (e.g. spurdog, cod, ling) have been increasingly replaced by smaller, low trophic level fish (e.g. small spotted catsharks) and invertebrates (e.g. scallops, crabs and lobster). Declining trophic levels in fisheries catches have occurred worldwide, with fish catches progressively being replaced by invertebrates. We argue that a network of fisheries closures would help rebalance the trophic status of the Channel and allow regeneration of marine ecosystems. PMID:25010196

Critical assessment and ramifications of a purported marine trophic cascade

USGS Publications Warehouse

Grubbs, R. Dean; Carlson, John K; Romine, Jason G.; Curtis, Tobey H; McElroy, W. David; McCandless, Camilla T; Cotton, Charles F; Musick, John A.

2016-01-01

When identifying potential trophic cascades, it is important to clearly establish the trophic linkages between predators and prey with respect to temporal abundance, demographics, distribution, and diet. In the northwest Atlantic Ocean, the depletion of large coastal sharks was thought to trigger a trophic cascade whereby predation release resulted in increased cownose ray abundance, which then caused increased predation on and subsequent collapse of commercial bivalve stocks. These claims were used to justify the development of a predator-control fishery for cownose rays, the “Save the Bay, Eat a Ray” fishery, to reduce predation on commercial bivalves. A reexamination of data suggests declines in large coastal sharks did not coincide with purported rapid increases in cownose ray abundance. Likewise, the increase in cownose ray abundance did not coincide with declines in commercial bivalves. The lack of temporal correlations coupled with published diet data suggest the purported trophic cascade is lacking the empirical linkages required of a trophic cascade. Furthermore, the life history parameters of cownose rays suggest they have low reproductive potential and their populations are incapable of rapid increases. Hypothesized trophic cascades should be closely scrutinized as spurious conclusions may negatively influence conservation and management decisions.

The trophic vacuum and the evolution of complex life cycles in trophically transmitted helminths

PubMed Central

Benesh, Daniel P.; Chubb, James C.; Parker, Geoff A.

2014-01-01

Parasitic worms (helminths) frequently have complex life cycles in which they are transmitted trophically between two or more successive hosts. Sexual reproduction often takes place in high trophic-level (TL) vertebrates, where parasites can grow to large sizes with high fecundity. Direct infection of high TL hosts, while advantageous, may be unachievable for parasites constrained to transmit trophically, because helminth propagules are unlikely to be ingested by large predators. Lack of niche overlap between propagule and definitive host (the trophic transmission vacuum) may explain the origin and/or maintenance of intermediate hosts, which overcome this transmission barrier. We show that nematodes infecting high TL definitive hosts tend to have more successive hosts in their life cycles. This relationship was modest, though, driven mainly by the minimum TL of hosts, suggesting that the shortest trophic chains leading to a host define the boundaries of the transmission vacuum. We also show that alternative modes of transmission, like host penetration, allow nematodes to reach high TLs without intermediate hosts. We suggest that widespread omnivory as well as parasite adaptations to increase transmission probably reduce, but do not eliminate, the barriers to the transmission of helminths through the food web. PMID:25209937

Trophic niche partitioning of littoral fish species from the rocky intertidal of Helgoland, Germany

NASA Astrophysics Data System (ADS)

Hielscher, N. N.; Malzahn, A. M.; Diekmann, R.; Aberle, N.

2015-12-01

During a 3-year field study, interspecific and interannual differences in the trophic ecology of littoral fish species were investigated in the rocky intertidal of Helgoland island (North Sea). We investigated trophic niche partitioning of common coexisting littoral fish species based on a multi-tracer approach using stable isotope and fatty acids in order to show differences and similarities in resource use and feeding modes. The results of the dual-tracer approach showed clear trophic niche partitioning of the five target fish species, the goldsinny wrasse Ctenolabrus rupestris, the sand goby Pomatoschistus minutus, the painted goby Pomatoschistus pictus, the short-spined sea scorpion Myoxocephalus scorpius and the long-spined sea scorpion Taurulus bubalis. Both stable isotopes and fatty acids showed distinct differences in the trophic ecology of the studied fish species. However, the combined use of the two techniques added an additional resolution on the interannual scale. The sand goby P. minutus showed the largest trophic plasticity with a pronounced variability between years. The present data analysis provides valuable information on trophic niche partitioning of fish species in the littoral zones of Helgoland and on complex benthic food webs in general.

Critical assessment and ramifications of a purported marine trophic cascade

PubMed Central

Grubbs, R. Dean; Carlson, John K.; Romine, Jason G.; Curtis, Tobey H.; McElroy, W. David; McCandless, Camilla T.; Cotton, Charles F.; Musick, John A.

2016-01-01

When identifying potential trophic cascades, it is important to clearly establish the trophic linkages between predators and prey with respect to temporal abundance, demographics, distribution, and diet. In the northwest Atlantic Ocean, the depletion of large coastal sharks was thought to trigger a trophic cascade whereby predation release resulted in increased cownose ray abundance, which then caused increased predation on and subsequent collapse of commercial bivalve stocks. These claims were used to justify the development of a predator-control fishery for cownose rays, the “Save the Bay, Eat a Ray” fishery, to reduce predation on commercial bivalves. A reexamination of data suggests declines in large coastal sharks did not coincide with purported rapid increases in cownose ray abundance. Likewise, the increase in cownose ray abundance did not coincide with declines in commercial bivalves. The lack of temporal correlations coupled with published diet data suggest the purported trophic cascade is lacking the empirical linkages required of a trophic cascade. Furthermore, the life history parameters of cownose rays suggest they have low reproductive potential and their populations are incapable of rapid increases. Hypothesized trophic cascades should be closely scrutinized as spurious conclusions may negatively influence conservation and management decisions. PMID:26876514

Improving the Quality and Scientific Understanding of Trophic Magnification Factors (TMFs)

EPA Science Inventory

This short 1000 word report presents a series of research needs for improving the measurement and understanding of trophic magnification factors (TMFs). TMFs are useful measures of trophic magnification and represent the diet-weighted average biomagnification factor (BMF) of che...

Trophodynamics of Emerging Brominated Flame Retardants in the Aquatic Food Web of Lake Taihu: Relationship with Organism Metabolism across Trophic Levels.

PubMed

Zheng, Guomao; Wan, Yi; Shi, Sainan; Zhao, Haoqi; Gao, Shixiong; Zhang, Shiyi; An, Lihui; Zhang, Zhaobin

2018-04-17

Despite the increasing use and discharge of novel brominated flame retardants, little information is available about their trophodynamics in the aquatic food web, and their subsequent relationships to compound metabolism. In this study, concentrations of 2,4,6-tribromophenyl allyl ether (ATE), 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), tetrabromo- o-chlorotoluene (TBCT), pentabromobenzyl acrylate (PBBA), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), bis(2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (TBPH), and decabromodiphenyl ethane (DBDPE) were measured in 17 species, including plankton, invertebrates, and fish from Lake Taihu, South China. Trophodynamics of the compounds were assessed, and metabolic rates were measured in the liver microsomes of crucian (trophic level [TL]: 2.93), catfish (TL: 3.86), and yellow-head catfish (TL: 4.3). Significantly positive relationships were found between trophic levels and lipid-normalized concentrations of ATE, BTBPE, and TBPH; their trophic magnification factors (TMFs) were 2.85, 2.83, and 2.42, respectively. Consistently, the three chemicals were resistant to metabolism in all fish microsomes. No significant relationship was observed for βTBECH ( p = 0.116), and DBDPE underwent trophic dilution in the food web (TMFs = 0.37, p = 0.021). Moreover, these two chemicals showed steady metabolism with incubation time in all fish microsomes. TBCT and PBBA exhibited significant trophic magnifications in the food web (TMF = 4.56, 2.01). Though different metabolic rates were observed for the two compounds among the tested fish species, TBCT and PBBA both showed metabolic resistance in high-trophic-level fish. These results indicated that metabolism of organisms at high trophic levels plays an important role in the assessment of trophic magnification potentials of these flame retardant chemicals.

Trophic interactions, ecosystem structure and function in the southern Yellow Sea

NASA Astrophysics Data System (ADS)

Lin, Qun; Jin, Xianshi; Zhang, Bo

2013-01-01

The southern Yellow Sea is an important fishing ground, providing abundant fishery resources. However, overfishing and climate change have caused a decline in the resource and damaged the ecosystem. We developed an ecosystem model to analyze the trophic interactions and ecosystem structure and function to guide sustainable development of the ecosystem. A trophic mass-balance model of the southern Yellow Sea during 2000-2001 was constructed using Ecopath with Ecosim software. We defined 22 important functional groups and studied their diet composition. The trophic levels of fish, shrimp, crabs, and cephalopods were between 2.78 and 4.39, and the mean trophic level of the fisheries was 3.24. The trophic flows within the food web occurred primarily in the lower trophic levels. The mean trophic transfer efficiency was 8.1%, of which 7.1% was from primary producers and 9.3% was from detritus within the ecosystem. The transfer efficiency between trophic levels II to III to IV to V to >V was 5.0%, 5.7%, 18.5%, and 19.7%-20.4%, respectively. Of the total flow, phytoplankton contributed 61% and detritus contributed 39%. Fishing is defined as a top predator within the ecosystem, and has a negative impact on most commercial species. Moreover, the ecosystem had a high gross efficiency of the fishery and a high value of primary production required to sustain the fishery. Together, our data suggest there is high fishing pressure in the southern Yellow Sea. Based on analysis of Odum's ecological parameters, this ecosystem was at an immature stage. Our results provide some insights into the structure and development of this ecosystem.

The Life Cycle Stages of Pneumocystis murina Have Opposing Effects on the Immune Response to This Opportunistic Fungal Pathogen

PubMed Central

Evans, Heather M.; Bryant, Grady L.

2016-01-01

The cell wall β-glucans of Pneumocystis cysts have been shown to stimulate immune responses in lung epithelial cells, dendritic cells, and alveolar macrophages. Little is known about how the trophic life forms, which do not have a fungal cell wall, interact with these innate immune cells. Here we report differences in the responses of both neonatal and adult mice to the trophic and cystic life cycle stages of Pneumocystis murina. The adult and neonatal immune responses to infection with Pneumocystis murina trophic forms were less robust than the responses to infection with a physiologically normal mixture of cysts and trophic forms. Cysts promoted the recruitment of nonresident innate immune cells and T and B cells into the lungs. Cysts, but not trophic forms, stimulated increased concentrations of the cytokine gamma interferon (IFN-γ) in the alveolar spaces and an increase in the percentage of CD4+ T cells that produce IFN-γ. In vitro, bone marrow-derived dendritic cells (BMDCs) stimulated with cysts produced the proinflammatory cytokines interleukin 1β (IL-1β) and IL-6. In contrast, trophic forms suppressed antigen presentation to CD4+ T cells, as well as the β-glucan-, lipoteichoic acid (LTA)-, and lipopolysaccharide (LPS)-induced production of interleukin 1β (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α) by BMDCs. The negative effects of trophic forms were not due to ligation of mannose receptor. Our results indicate that optimal innate and adaptive immune responses to Pneumocystis species are dependent on stimulation with the cyst life cycle stage. Conversely, trophic forms suppress β-glucan-induced proinflammatory responses in vitro, suggesting that the trophic forms dampen cyst-induced inflammation in vivo. PMID:27572330

Gastrin and the growth of the gastrointestinal tract.

PubMed Central

Ekundayo, A A; Lee, C Y; Goodlad, R A

1995-01-01

While the proliferative effects of gastrin in the gastric fundus are well established, there is a considerable degree of confusion regarding the role of gastrin on the growth of the small intestine and colon. The hypothesis that gastrin is trophic throughout the gut was tested by giving three doses of pentagastrin and one of gastrin 17 to rats maintained by total parenteral nutrition (TPN). The rats were fed intravenously for one week, with the various peptides added to the TPN diet. The number of vincristine arrested metaphases per gland or crypt was then scored to determine the proliferative state. Both gastrin 17 and pentagastrin were found to be trophic in the gastric fundus, but not to the gastric antrum. A proliferative response was also seen in the duodenum, but with little evidence of a dose response element. No effect on small bowel weight was seen, and no proliferative effect was noted in the mid small bowel, thus the duodenal effect could be attributed to a local action of increased acid output on the duodenum, not a general role throughout the small intestine. No proliferative effects of pentagastrin or gastrin were seen in the colon. It is therefore concluded that the trophic role of gastrin is restricted to the gastric fundus and the proximal duodenum. PMID:7883218

Eutrophication in Poyang Lake (Eastern China) over the Last 300 Years in Response to Changes in Climate and Lake Biomass

PubMed Central

Liao, Mengna; Yu, Ge; Guo, Ya

2017-01-01

Poyang Lake is suffering from persistent eutrophication, which is degrading the local ecosystem. A better understanding of the mechanisms that drive eutrophication in lake systems is essential to fight the ongoing deterioration. In this study, hydraulic residence time (HRT) was used to evaluate Poyang Lake’s trophic state. A hydrology and ecosystem forced model was constructed to simulate long-term changes in algae and aquatic plant biomass and total phosphorous (TP). A comparison analysis revealed that between 1812 and 1828 (i.e., a consistent-change stage), climate and hydrology were the main driving forces, while algae and aquatic plant biomass contributed only 20.9% to the trophic changes in Poyang Lake. However, between 1844 and 1860 the biomass predominated contributing 63.6%. This could be attributed to nutrient absorption by algae and aquatic plants. A correlation analysis of the water TP and algae and aquatic plant biomass revealed a strong positive relationship. However, the algae and aquatic plant growth rate tended to decline after the biomass reached half of the maximum. This research reconstructs the long-term trophic evolution of Poyang Lake and provides a better understanding of the relationship between climatic and hydrological changes and lake ecosystems. PMID:28046083

What is a Trophic Cascade?

PubMed

Ripple, William J; Estes, James A; Schmitz, Oswald J; Constant, Vanessa; Kaylor, Matthew J; Lenz, Adam; Motley, Jennifer L; Self, Katharine E; Taylor, David S; Wolf, Christopher

2016-11-01

Few concepts in ecology have been so influential as that of the trophic cascade. Since the 1980s, the term has been a central or major theme of more than 2000 scientific articles. Despite this importance and widespread usage, basic questions remain about what constitutes a trophic cascade. Inconsistent usage of language impedes scientific progress and the utility of scientific concepts in management and conservation. Herein, we offer a definition of trophic cascade that is designed to be both widely applicable yet explicit enough to exclude extraneous interactions. We discuss our proposed definition and its implications, and define important related terms, thereby providing a common language for scientists, policy makers, conservationists, and other stakeholders with an interest in trophic cascades. Copyright © 2016 Elsevier Ltd. All rights reserved.

Phenotypic integration in a series of trophic traits: tracing the evolution of myrmecophagy in spiders (Araneae).

PubMed

Pekár, Stano; Michalko, Radek; Korenko, Stanislav; Sedo, Ondřej; Líznarová, Eva; Sentenská, Lenka; Zdráhal, Zbyněk

2013-02-01

Several hypotheses have been put forward to explain the evolution of prey specificity (stenophagy). Yet little light has so far been shed on the process of evolution of stenophagy in carnivorous predators. We performed a detailed analysis of a variety of trophic adaptations in one species. Our aim was to determine whether a specific form of stenophagy, myrmecophagy, has evolved from euryphagy via parallel changes in several traits from pre-existing characters. For that purpose, we studied the trophic niche and morphological, behavioural, venomic and physiological adaptations in a euryphagous spider, Selamia reticulata. It is a species that is branching off earlier in phylogeny than stenophagous ant-eating spiders of the genus Zodarion (both Zodariidae). The natural diet was wide and included ants. Laboratory feeding trials revealed versatile prey capture strategies that are effective on ants and other prey types. The performance of spiders on two different diets - ants only and mixed insects - failed to reveal differences in most fitness components (survival and developmental rate). However, the weight increase was significantly higher in spiders on the mixed diet. As a result, females on a mixed diet had higher fecundity and oviposited earlier. No differences were found in incubation period, hatching success or spiderling size. S. reticulata possesses a more diverse venom composition than Zodarion. Its venom is more effective for the immobilisation of beetle larvae than of ants. Comparative analysis of morphological traits related to myrmecophagy in the family Zodariidae revealed that their apomorphic states appeared gradually along the phylogeny to derived prey-specialised genera. Our results suggest that myrmecophagy has evolved gradually from the ancestral euryphagous strategy by integrating a series of trophic traits. Copyright © 2012 Elsevier GmbH. All rights reserved.

Molecular trophic markers in marine food webs and their potential use for coral ecology.

PubMed

Leal, Miguel Costa; Ferrier-Pagès, Christine

2016-10-01

Notable advances in ecological genomics have been driven by high-throughput sequencing technology and taxonomically broad sequence repositories that allow us to accurately assess species interactions with great taxonomic resolution. The use of DNA as a marker for ingested food is particularly relevant to address predator-prey interactions and disentangle complex marine food webs. DNA-based methods benefit from reductionist molecular approaches to address ecosystem scale processes, such as community structure and energy flow across trophic levels, among others. Here we review how molecular trophic markers have been used to better understand trophic interactions in the marine environment and their advantages and limitations. We focus on animal groups where research has been focused, such as marine mammals, seabirds, fishes, pelagic invertebrates and benthic invertebrates, and use case studies to illustrate how DNA-based methods unraveled food-web interactions. The potential of molecular trophic markers for disentangling the complex trophic ecology of corals is also discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

[Research progress on food sources and food web structure of wetlands based on stable isotopes].

PubMed

Chen, Zhan Yan; Wu, Hai Tao; Wang, Yun Biao; Lyu, Xian Guo

2017-07-18

The trophic dynamics of wetland organisms is the basis of assessing wetland structure and function. Stable isotopes of carbon and nitrogen have been widely applied to identify trophic relationships in food source, food composition and food web transport in wetland ecosystem studies. This paper provided an overall review about the current methodology of isotope mixing model and trophic level in wetland ecosystems, and discussed the standards of trophic fractionation and baseline. Moreover, we characterized the typical food sources and isotopic compositions of wetland ecosystems, summarized the food sources in different trophic levels of herbivores, omnivores and carnivores based on stable isotopic analyses. We also discussed the limitations of stable isotopes in tra-cing food sources and in constructing food webs. Based on the current results, development trends and upcoming requirements, future studies should focus on sample treatment, conservation and trophic enrichment measurement in the wetland food web, as well as on combing a variety of methodologies including traditional stomach stuffing, molecular markers, and multiple isotopes.

Elucidating fishing effects in a large-predator dominated system: The case of Darwin and Wolf Islands (Galápagos)

NASA Astrophysics Data System (ADS)

Ruiz, Diego J.; Banks, Stuart; Wolff, Matthias

2016-01-01

Fifty years of artisanal fishing history in Galápagos characterized by boom and bust of resources has changed the natural marine community structure close to fishing ports in the Galápagos Marine Reserve. Nonetheless, the remote Darwin and Wolf Islands are still in a "near natural state" harboring high species richness unique for the archipelago and high biomass. Marine life that aggregates to the pinnacles linked to the wider oceanic seascape makes them interesting and unique systems in terms of community structure and study of on-shore/offshore trophic interactions. Although > 200 km from local fishing ports the two islands also support an artisanal fishery targeting large demersal predators of high trophic levels. They are areas prioritized for conservation actions by Galápagos National Park, and local non-governmental organizations given their natural heritage importance, value to local fishers and revenue from dive tourism attracted by the promise of large marine predator aggregations such as sharks. Given that catch data upon which to base conservation recommendations is sparse it is difficult to accurately estimate present day fishing trends in Darwin and Wolf. We used a trophic steady-state model that connects benthic and pelagic communities to assess the potential effects of a change in fishing intensity in the two islands system. A predator-prey matrix was built using the Ecopath with Ecosim (EwE) software with total biomass estimated at 937 t km- 2. Large fish aggregations accounted for 19%, primary producers for 9.0% and non-fish (seabirds, marine mammals and sea turtles) for less than 0.1% of the total living biomass. The total system size in terms of overall flows was 16,652 t km- 2 year- 1, four times larger than a generic seamount model but smaller than that modeled for a Galápagos upwelling system based upon the western Bolivar Channel region. Consumption and respiration dominated the flows in the system (53.4 and 31.8% respectively). The Darwin and Wolf system shows a mature state, dominated by respiration, and top-down control via sharks and benthic predatory fish as the most important system compartments in terms of biomass. Model simulations suggest that heavy fishing pressure on top predators would greatly change the system's trophic structure. The nature of impacts depended on the types of gears simulated. Reduced natural predator densities through fishing exert strong direct and indirect influences on the system towards sea urchin-dominated benthos.

A test of trophic cascade theory: fish and benthic assemblages across a predator density gradient on coral reefs.

PubMed

Casey, Jordan M; Baird, Andrew H; Brandl, Simon J; Hoogenboom, Mia O; Rizzari, Justin R; Frisch, Ashley J; Mirbach, Christopher E; Connolly, Sean R

2017-01-01

Removal of predators is often hypothesized to alter community structure through trophic cascades. However, despite recent advances in our understanding of trophic cascades, evidence is often circumstantial on coral reefs because fishing pressure frequently co-varies with other anthropogenic effects, such as fishing for herbivorous fishes and changes in water quality due to pollution. Australia's outer Great Barrier Reef (GBR) has experienced fishing-induced declines of apex predators and mesopredators, but pollution and targeting of herbivorous fishes are minimal. Here, we quantify fish and benthic assemblages across a fishing-induced predator density gradient on the outer GBR, including apex predators and mesopredators to herbivores and benthic assemblages, to test for evidence of trophic cascades and alternative hypotheses to trophic cascade theory. Using structural equation models, we found no cascading effects from apex predators to lower trophic levels: a loss of apex predators did not lead to higher levels of mesopredators, and this did not suppress mobile herbivores and drive algal proliferation. Likewise, we found no effects of mesopredators on lower trophic levels: a decline of mesopredators was not associated with higher abundances of algae-farming damselfishes and algae-dominated reefs. These findings indicate that top-down forces on coral reefs are weak, at least on the outer GBR. We conclude that predator-mediated trophic cascades are probably the exception rather than the rule in complex ecosystems such as the outer GBR.

Trophic look at soft-bottom communities - Short-term effects of trawling cessation on benthos

NASA Astrophysics Data System (ADS)

Dannheim, Jennifer; Brey, Thomas; Schröder, Alexander; Mintenbeck, Katja; Knust, Rainer; Arntz, Wolf E.

2014-01-01

The trophic structure of the German Bight soft-bottom benthic community was evaluated for potential changes after cessation of bottom trawling. Species were collected with van-Veen grabs and beam trawls. Trophic position (i.e. nitrogen stable isotope ratios, δ15N) and energy flow (i.e. species metabolism approximated by body mass scaled abundance) of dominant species were compared in trawled areas and an area protected from fisheries for 14 months in order to detect trawling cessation effects by trophic characteristics. At the community level, energy flow was lower in the protected area, but we were unable to detect significant changes in trophic position. At the species level energy flow in the protected area was lower for predating/scavenging species but higher for interface feeders. Species trophic positions of small predators/scavengers were lower and of deposit feeders higher in the protected area. Major reasons for trophic changes after trawling cessation may be the absence of artificial and additional food sources from trawling likely to attract predators and scavengers, and the absence of physical sediment disturbance impacting settlement/survival of less mobile species and causing a gradual shift in food availability and quality. Our results provide evidence that species or community energy flow is a good indicator to detect trawling induced energy-flow alterations in the benthic system, and that in particular species trophic properties are suitable to capture subtle and short-term changes in the benthos following trawling cessation.

The effects of urbanization on trophic interactions in a desert landscape

USDA-ARS?s Scientific Manuscript database

Background/Question/Methods: Trophic systems can be affected through top-down (predators) and bottom-up (resources) impacts. Human activity can alter trophic systems by causing predators to avoid areas (top-down) or by providing increased resources through irrigation and decorative plants that attra...

EFFECTS OF SEDIMENT CONTAMINANTS AND ENVIRONMENTAL GRADIENTS ON MACROBENTHIC COMMUNITY TROPHIC STRUCTURE IN GULF OF MEXICO ESTUARIES

EPA Science Inventory

Macrobenthic communities from estuaries throughout the northern Gulf of Mexico were studied to assess the influence of sediment contaminants and natural environmental factors on macrobenthic community trophic structure. Community trophic data were also used to evaluate whether re...

Food Webs and Multiple Biotic Interactions in Plant-Herbivore Models

USDA-ARS?s Scientific Manuscript database

Trophic relationships between plants and insects are not confined to biological interactions such as herbivory (i.e. direct consumption of one primary producer by a predator), in an ecological approach, many other interactions, trophic or even non trophic, may influence plant herbivory by insects. T...

Climate Change and Baleen Whale Trophic Cascades in Greenland

DTIC Science & Technology

2009-09-30

DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited. Climate Change and Baleen Whale Trophic Cascades in Greenland...SUBTITLE Climate Change And Baleen Whale Trophic Cascades In Greenland 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S

Food web heterogeneity and succession in created saltmarshes

USGS Publications Warehouse

Nordstrom, M C; Demopoulos, Amanda W.J.; Whitcraft, CR; Rismondo, A.; McMillan, P.; Gonzales, J P; Levin, L A

2015-01-01

1. Ecological restoration must achieve functional as well as structural recovery. Functional metrics for reestablishment of trophic interactions can be used to complement traditional monitoring of structural attributes. In addition, topographic effects on food web structure provide added information within a restoration context; often, created sites may require spatial heterogeneity to effectively match structure and function of natural habitats. 2. We addressed both of these issues in our study of successional development of benthic food web structure, with focus on bottom–up driven changes in macroinvertebrate consumer assemblages in the salt marshes of the Venice Lagoon, Italy. We combined quantified estimates of the changing community composition with stable isotope data (13C:12C and 15N:14N) to compare the general trophic structure between created (2–14 years) marshes and reference sites and along topographic elevation gradients within salt marshes. 3. Macrofaunal invertebrate consumers exhibited local, habitat-specific trophic patterns. Stable isotope-based trophic structure changed with increasing marsh age, in particular with regards to mid-elevation (Salicornia) habitats. In young marshes, the mid-elevation consumer signatures resembled those of unvegetated ponds. The mid elevation of older and natural marshes had a more distinct Salicornia-zone food web, occasionally resembling that of the highest (Sarcocornia-dominated) elevation. In summary, this indicates that primary producers and availability of vascular plant detritus structure consumer trophic interactions and the flow of carbon. 4. Functionally different consumers, subsurface-feeding detritivores (Oligochaeta) and surface grazers (Hydrobia sp.), showed distinct but converging trajectories of isotopic change over time, indicating that successional development may be asymmetric between ‘brown’ (detrital) guilds and ‘green’ (grazing) guilds in the food web. 5. Synthesis and applications. Created marsh food webs converged into a natural state over about a decade, with successional shifts seen in both consumer community composition and stable isotope space. Strong spatial effects were noted, highlighting the utility of stable isotopes to evaluate functional equivalence in spatially heterogeneous systems. Understanding the recovery of functional properties such as food web support, and their inherent spatial variability, is key to planning and managing successful habitat restoration.

Form and function of damselfish skulls: rapid and repeated evolution into a limited number of trophic niches.

PubMed

Cooper, W James; Westneat, Mark W

2009-01-30

Damselfishes (Perciformes, Pomacentridae) are a major component of coral reef communities, and the functional diversity of their trophic anatomy is an important constituent of the ecological morphology of these systems. Using shape analyses, biomechanical modelling, and phylogenetically based comparative methods, we examined the anatomy of damselfish feeding among all genera and trophic groups. Coordinate based shape analyses of anatomical landmarks were used to describe patterns of morphological diversity and determine positions of functional groups in a skull morphospace. These landmarks define the lever and linkage structures of the damselfish feeding system, and biomechanical analyses of this data were performed using the software program JawsModel4 in order to calculate the simple mechanical advantage (MA) employed by different skull elements during feeding, and to compute kinematic transmission coefficients (KT) that describe the efficiency with which angular motion is transferred through the complex linkages of damselfish skulls. Our results indicate that pomacentrid planktivores are significantly different from other damselfishes, that biting MA values and protrusion KT ratios are correlated with pomacentrid trophic groups more tightly than KT scores associated with maxillary rotation and gape angle, and that the MAs employed by their three biting muscles have evolved independently. Most of the biomechanical parameters examined have experienced low levels of phylogenetic constraint, which suggests that they have evolved quickly. Joint morphological and biomechanical analyses of the same anatomical data provided two reciprocally illuminating arrays of information. Both analyses showed that the evolution of planktivory has involved important changes in pomacentrid functional morphology, and that the mechanics of upper jaw kinesis have been of great importance to the evolution of damselfish feeding. Our data support a tight and biomechanically defined link between structure and the functional ecology of fish skulls, and indicate that certain mechanisms for transmitting motion through their jaw linkages may require particular anatomical configurations, a conclusion that contravenes the concept of "many-to-one mapping" for fish jaw mechanics. Damselfish trophic evolution is characterized by rapid and repeated shifts between a small number of eco-morphological states, an evolutionary pattern that we describe as reticulate adaptive radiation.

TYPES OF SALT MARSH EDGE AND EXPORT OF TROPHIC ENERGY FROM MARSHES TO DEEPER HABITATS

EPA Science Inventory

We quantified nekton and estimated trophic export at salt marshes with both erosional and depositional edges at the Goodwin Islands (York River, Virginia, USA). At depositional-edge marshes, we examined trophic flows through quantitative sampling with 1.75 m2 drop rings, and thro...

Invasive plant architecture alters trophic interactions by changing predator abundance and behavior

Treesearch

Dean E. Pearson

2009-01-01

As primary producers, plants are known to influence higher trophic interactions by initiating food chains. However, as architects, plants may bypass consumers to directly affect predators with important but underappreciated trophic ramifications. Invasion of western North American grasslands by the perennial forb, spotted knapweed (Centaurea maculosa...

Infectious Agents Trigger Trophic Cascades.

PubMed

Buck, Julia C; Ripple, William J

2017-09-01

Most demonstrated trophic cascades originate with predators, but infectious agents can also cause top-down indirect effects in ecosystems. Here we synthesize the literature on trophic cascades initiated by infectious agents including parasitoids, pathogens, parasitic castrators, macroparasites, and trophically transmitted parasites. Like predators, infectious agents can cause density-mediated and trait-mediated indirect effects through their direct consumptive and nonconsumptive effects respectively. Unlike most predators, however, infectious agents are not fully and immediately lethal to their victims, so their consumptive effects can also trigger trait-mediated indirect effects. We find that the frequency of trophic cascades reported for different consumer types scales with consumer lethality. Furthermore, we emphasize the value of uniting predator-prey and parasite-host theory under a general consumer-resource framework. Copyright © 2017 Elsevier Ltd. All rights reserved.

The trophic vacuum and the evolution of complex life cycles in trophically transmitted helminths.

PubMed

Benesh, Daniel P; Chubb, James C; Parker, Geoff A

2014-10-22

Parasitic worms (helminths) frequently have complex life cycles in which they are transmitted trophically between two or more successive hosts. Sexual reproduction often takes place in high trophic-level (TL) vertebrates, where parasites can grow to large sizes with high fecundity. Direct infection of high TL hosts, while advantageous, may be unachievable for parasites constrained to transmit trophically, because helminth propagules are unlikely to be ingested by large predators. Lack of niche overlap between propagule and definitive host (the trophic transmission vacuum) may explain the origin and/or maintenance of intermediate hosts, which overcome this transmission barrier. We show that nematodes infecting high TL definitive hosts tend to have more successive hosts in their life cycles. This relationship was modest, though, driven mainly by the minimum TL of hosts, suggesting that the shortest trophic chains leading to a host define the boundaries of the transmission vacuum. We also show that alternative modes of transmission, like host penetration, allow nematodes to reach high TLs without intermediate hosts. We suggest that widespread omnivory as well as parasite adaptations to increase transmission probably reduce, but do not eliminate, the barriers to the transmission of helminths through the food web. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Examining predator–prey body size, trophic level and body mass across marine and terrestrial mammals

PubMed Central

Tucker, Marlee A.; Rogers, Tracey L.

2014-01-01

Predator–prey relationships and trophic levels are indicators of community structure, and are important for monitoring ecosystem changes. Mammals colonized the marine environment on seven separate occasions, which resulted in differences in species' physiology, morphology and behaviour. It is likely that these changes have had a major effect upon predator–prey relationships and trophic position; however, the effect of environment is yet to be clarified. We compiled a dataset, based on the literature, to explore the relationship between body mass, trophic level and predator–prey ratio across terrestrial (n = 51) and marine (n = 56) mammals. We did not find the expected positive relationship between trophic level and body mass, but we did find that marine carnivores sit 1.3 trophic levels higher than terrestrial carnivores. Also, marine mammals are largely carnivorous and have significantly larger predator–prey ratios compared with their terrestrial counterparts. We propose that primary productivity, and its availability, is important for mammalian trophic structure and body size. Also, energy flow and community structure in the marine environment are influenced by differences in energy efficiency and increased food web stability. Enhancing our knowledge of feeding ecology in mammals has the potential to provide insights into the structure and functioning of marine and terrestrial communities. PMID:25377460

Bioaccumulation and trophic dilution of human pharmaceuticals across trophic positions of an effluent-dependent wadeable stream

PubMed Central

Du, Bowen; Haddad, Samuel P.; Luek, Andreas; Scott, W. Casan; Saari, Gavin N.; Kristofco, Lauren A.; Connors, Kristin A.; Rash, Christopher; Rasmussen, Joseph B.; Chambliss, C. Kevin; Brooks, Bryan W.

2014-01-01

Though pharmaceuticals are increasingly observed in a variety of organisms from coastal and inland aquatic systems, trophic transfer of pharmaceuticals in aquatic food webs have not been reported. In this study, bioaccumulation of select pharmaceuticals was investigated in a lower order effluent-dependent stream in central Texas, USA, using isotope dilution liquid chromatography–tandem mass spectrometry (MS). A fish plasma model, initially developed from laboratory studies, was tested to examine observed versus predicted internal dose of select pharmaceuticals. Pharmaceuticals accumulated to higher concentrations in invertebrates relative to fish; elevated concentrations of the antidepressant sertraline and its primary metabolite desmethylsertraline were observed in the Asian clam, Corbicula fluminea, and two unionid mussel species. Trophic positions were determined from stable isotopes (δ15N and δ13C) collected by isotope ratio-MS; a Bayesian mixing model was then used to estimate diet contributions towards top fish predators. Because diphenhydramine and carbamazepine were the only target compounds detected in all species examined, trophic magnification factors (TMFs) were derived to evaluate potential trophic transfer of both compounds. TMFs for diphenhydramine (0.38) and carbamazepine (1.17) indicated neither compound experienced trophic magnification, which suggests that inhalational and not dietary exposure represented the primary route of uptake by fish in this effluent-dependent stream. PMID:25313153

Predator Persistence through Variability of Resource Productivity in Tritrophic Systems.

PubMed

Soudijn, Floor H; de Roos, André M

2017-12-01

The trophic structure of species communities depends on the energy transfer between trophic levels. Primary productivity varies strongly through time, challenging the persistence of species at higher trophic levels. Yet resource variability has mostly been studied in systems with only one or two trophic levels. We test the effect of variability in resource productivity in a tritrophic model system including a resource, a size-structured consumer, and a size-specific predator. The model complies with fundamental principles of mass conservation and the body-size dependence of individual-level energetics and predator-prey interactions. Surprisingly, we find that resource variability may promote predator persistence. The positive effect of variability on the predator arises through periods with starvation mortality of juvenile prey, which reduces the intraspecific competition in the prey population. With increasing variability in productivity and starvation mortality in the juvenile prey, the prey availability increases in the size range preferred by the predator. The positive effect of prey mortality on the trophic transfer efficiency depends on the biologically realistic consideration of body size-dependent and food-dependent functions for growth and reproduction in our model. Our findings show that variability may promote the trophic transfer efficiency, indicating that environmental variability may sustain species at higher trophic levels in natural ecosystems.

Evaluating trophic cascades as drivers of regime shifts in different ocean ecosystems

PubMed Central

Pershing, Andrew J.; Mills, Katherine E.; Record, Nicholas R.; Stamieszkin, Karen; Wurtzell, Katharine V.; Byron, Carrie J.; Fitzpatrick, Dominic; Golet, Walter J.; Koob, Elise

2015-01-01

In ecosystems that are strongly structured by predation, reducing top predator abundance can alter several lower trophic levels—a process known as a trophic cascade. A persistent trophic cascade also fits the definition of a regime shift. Such ‘trophic cascade regime shifts' have been reported in a few pelagic marine systems—notably the Black Sea, Baltic Sea and eastern Scotian Shelf—raising the question of how common this phenomenon is in the marine environment. We provide a general methodology for distinguishing top-down and bottom-up effects and apply this methodology to time series from these three ecosystems. We found evidence for top-down forcing in the Black Sea due primarily to gelatinous zooplankton. Changes in the Baltic Sea are primarily bottom-up, strongly structured by salinity, but top-down forcing related to changes in cod abundance also shapes the ecosystem. Changes in the eastern Scotian Shelf that were originally attributed to declines in groundfish are better explained by changes in stratification. Our review suggests that trophic cascade regime shifts are rare in open ocean ecosystems and that their likelihood increases as the residence time of water in the system increases. Our work challenges the assumption that negative correlation between consecutive trophic levels implies top-down forcing.

Predator and prey biodiversity relationship and its consequences on marine ecosystem functioning-interplay between nanoflagellates and bacterioplankton.

PubMed

Yang, Jinny Wu; Wu, Wenxue; Chung, Chih-Ching; Chiang, Kuo-Ping; Gong, Gwo-Ching; Hsieh, Chih-Hao

2018-06-01

The importance of biodiversity effects on ecosystem functioning across trophic levels, especially via predatory-prey interactions, is receiving increased recognition. However, this topic has rarely been explored for marine microbes, even though microbial biodiversity contributes significantly to marine ecosystem function and energy flows. Here we examined diversity and biomass of bacteria (prey) and nanoflagellates (predators), as well as their effects on trophic transfer efficiency in the East China Sea. Specifically, we investigated: (i) predator diversity effects on prey biomass and trophic transfer efficiency (using the biomass ratio of predator/prey as a proxy), (ii) prey diversity effects on predator biomass and trophic transfer efficiency, and (iii) the relationship between predator and prey diversity. We found higher prey diversity enhanced both diversity and biomass of predators, as well as trophic transfer efficiency, which may arise from more balanced diet and/or enhanced niche complementarity owing to higher prey diversity. By contrast, no clear effect was detected for predator diversity on prey biomass and transfer efficiency. Notably, we found prey diversity effects on predator-prey interactions; whereas, we found no significant diversity effect on biomass within the same trophic level. Our findings highlight the importance of considering multi-trophic biodiversity effects on ecosystem functioning in natural ecosystems.

Pre- and post-hatch trophic egg production in the subsocial burrower bug, Canthophorus niveimarginatus (Heteroptera: Cydnidae)

NASA Astrophysics Data System (ADS)

Filippi, Lisa; Baba, Narumi; Inadomi, Koichi; Yanagi, Takao; Hironaka, Mantaro; Nomakuchi, Shintaro

2009-02-01

In recent years, three terrestrial bugs, Adomerus triguttulus and Sehirus cinctus (Cydnidae) and the closely related Parastrachia japonensis (Parastrachiidae), have been the focus of several fascinating studies because of the remarkable, extensive parental care they were found to display. This care includes egg and nymph guarding, production of trophic eggs, unfertilized, low cost eggs that are used as food by newly hatched nymphs, and progressive provisioning of the host seed. In this study, we have investigated yet a third related Asian cydnid, Canthophorus niveimarginatus, with regard to the possible occurrence of some or all of these complex traits in order to assess how widespread these maternal investment patterns are in this group of insects and to better understand the implications of their manifestations from an evolutionary context. Manipulative experiments were carried out in the lab to determine whether females provision nests. Observational and egg removal studies were carried out to determine whether trophic eggs are produced, and, if they are, their possible impact on nymphal success. The findings revealed that C. niveimarginatus does, in fact, progressively provision young, and this species also displays all of the other behaviors associated with extended parental care in subsocial insects. Moreover, unlike the other two related species, which place trophic eggs on the surface of the original egg mass, C. niveimarginatus produces both pre- and post-hatch trophic eggs. Nymphs deprived of access to post-hatch trophic eggs had significantly lower body weight and survival rate than those that fed on them. To our knowledge, this is the first time the production of both pre- and post-hatch trophic eggs has been demonstrated in insects outside the Hymenoptera. In this paper, we qualitatively and quantitatively demonstrate the provisioning behavior and patterns of trophic egg production in C. niveimarginatus. When and how trophic eggs are produced and delivered to young should have important correlations with the ecological and life history constraints under which a species has evolved. Thus, we also discuss the possible ecological and life history factors that favor the evolution of post-hatch trophic eggs.

Amino Acid Isotopic Trophic Enrichment in Mesozooplankton: Is Alanine a Better Predictor of Protistan Grazer Steps?

NASA Astrophysics Data System (ADS)

Decima, M.; Landry, M. R.; Bradley, C. J.; Fogel, M. L.

2016-02-01

Food-web studies within marine environments are increasingly reliant upon results from compound-specific isotope analysis of amino acids (CSIA-AA). The approach is advantageous because it allows consumer trophic positions to be estimated without sampling the dynamic primary producers. The baseline signal in the source AA phenylalanine is preserved, and a constant enrichment in glutamic acid at each trophic step is assumed, regardless of consumer type or diet. However, a number of recent studies challenge the assumption of universal and invariant isotopic fractionation of glutamic acid for all trophic levels, as well as its specific applicability to the main grazers in the ocean: the protistan microzooplankton. We present results from both laboratory and field studies that further explore this issue. Experiments include six 2-stage chemostats, using two different microzooplankton-phytoplankton pairs and one copepod-phytoplankton pair, and one 3-stage experiment using a copepod-microzooplankton-phytoplankton chain. We confirm previous observations of negligible fractionation of glutamic acid in protistan consumers when nutrients are limiting. In contrast, a consistent trophic enrichment effect was observed for alanine, with increasing δ15N values by trophic level for both metazoan and protistan consumers. A re-analysis of published CSIA-AA data of zooplankton species show that an index using alanine and phenylalanine gives trophic level estimates closer to expected given current understanding of the linkages within microbial food webs. Our results examine the details of isotopic fractionation of alanine within defined food chains and generally support its potential use as a trophic level indicator that includes the protistan contribution to mesozooplankton diet.

Application of LANDSAT to the surveillance of lake eutrophication in the Great Lakes basin. [Saginaw Bay, Michigan

NASA Technical Reports Server (NTRS)

Rogers, R. H.; Smith, V. E.; Scherz, J. P.; Woelkerling, W. J.; Adams, M. S.; Gannon, J. E. (Principal Investigator)

1977-01-01

The author has identified the following significant results. A step-by-step procedure for establishing and monitoring the trophic status of inland lakes with the use of LANDSAT data, surface sampling, laboratory analysis, and aerial observations were demonstrated. The biomass was related to chlorophyll-a concentrations, water clarity, and trophic state. A procedure was developed for using surface sampling, LANDSAT data, and linear regression equations to produce a color-coded image of large lakes showing the distribution and concentrations of water quality parameters, causing eutrophication as well as parameters which indicate its effects. Cover categories readily derived from LANDSAT were those for which loading rates were available and were known to have major effects on the quality and quantity of runoff and lake eutrophication. Urban, barren land, cropland, grassland, forest, wetlands, and water were included.

Food-web stability signals critical transitions in temperate shallow lakes

PubMed Central

Kuiper, Jan J.; van Altena, Cassandra; de Ruiter, Peter C.; van Gerven, Luuk P. A.; Janse, Jan H.; Mooij, Wolf M.

2015-01-01

A principal aim of ecologists is to identify critical levels of environmental change beyond which ecosystems undergo radical shifts in their functioning. Both food-web theory and alternative stable states theory provide fundamental clues to mechanisms conferring stability to natural systems. Yet, it is unclear how the concept of food-web stability is associated with the resilience of ecosystems susceptible to regime change. Here, we use a combination of food web and ecosystem modelling to show that impending catastrophic shifts in shallow lakes are preceded by a destabilizing reorganization of interaction strengths in the aquatic food web. Analysis of the intricate web of trophic interactions reveals that only few key interactions, involving zooplankton, diatoms and detritus, dictate the deterioration of food-web stability. Our study exposes a tight link between food-web dynamics and the dynamics of the whole ecosystem, implying that trophic organization may serve as an empirical indicator of ecosystem resilience. PMID:26173798

Emerging Chagas disease: trophic network and cycle of transmission of Trypanosoma cruzi from palm trees in the Amazon.

PubMed Central

Teixeira, A. R.; Monteiro, P. S.; Rebelo, J. M.; Argañaraz, E. R.; Vieira, D.; Lauria-Pires, L.; Nascimento, R.; Vexenat, C. A.; Silva, A. R.; Ault, S. K.; Costa, J. M.

2001-01-01

A trophic network involving molds, invertebrates, and vertebrates, ancestrally adapted to the palm tree (Attalaea phalerata) microhabitat, maintains enzootic Trypanosoma cruzi infections in the Amazonian county Paço do Lumiar, state of Maranhão, Brazil. We assessed seropositivity for T. cruzi infections in the human population of the county, searched in palm trees for the triatomines that harbor these infections, and gathered demographic, environmental, and socioeconomic data. Rhodnius pictipes and R. neglectus in palm-tree frond clefts or in houses were infected with T. cruzi (57% and 41%, respectively). Human blood was found in 6.8% of R. pictipes in houses, and 9 of 10 wild Didelphis marsupialis had virulent T. cruzi infections. Increasing human population density, rain forest deforestation, and human predation of local fauna are risk factors for human T. cruzi infections. PMID:11266300

Connectivity of tropical marine ecosystems--An overview of interdisciplinary research to understand biodiversity and trophic relationships in the Virgin Islands and Puerto Rico

USGS Publications Warehouse

McClain-Counts, Jennifer P.; Demopoulos, Amanda W.J.

2012-01-01

The Virgin Islands and Puerto Rico contain marine reserves and protected areas that encompass a variety of tropical ecosystems, including coral reefs, mangroves, and seagrass beds. Reserves and protected areas are established for a variety of reasons, such as preserving nursery habitats and biodiversity, or reducing anthropogenic effects associated with pollution and land use. Questions remain regarding the effectiveness of these designated areas in preserving and protecting spatially connected habitats and associated fishes and invertebrates. Scientists from the U.S. Geological Survey (USGS), University of Florida, and Arkansas State University are collaborating on interdisciplinary research in the Virgin Islands and Puerto Rico to examine the biodiversity and trophic dynamics of fishes and invertebrates residing in connected mangroves, seagrasses, and coral reefs to discern the effectiveness of current marine reserves and protected areas for conserving reef resources.

Trophic cascades triggered by overfishing reveal possible mechanisms of ecosystem regime shifts.

PubMed

Daskalov, Georgi M; Grishin, Alexander N; Rodionov, Sergei; Mihneva, Vesselina

2007-06-19

Large-scale transitions between alternative states in ecosystems are known as regime shifts. Once described as healthy and dominated by various marine predators, the Black Sea ecosystem by the late 20th century had experienced anthropogenic impacts such as heavy fishing, cultural eutrophication, and invasions by alien species. We studied changes related to these "natural experiments" to reveal the mechanisms of regime shifts. Two major shifts were detected, the first related to a depletion of marine predators and the second to an outburst of the alien comb jelly Mnemiopsis leidyi; both shifts were triggered by intense fishing resulting in system-wide trophic cascades. The complex nature of ecosystem responses to human activities calls for more elaborate approaches than currently provided by traditional environmental and fisheries management. This implies challenging existing practices and implementing explanatory models of ecosystem interactions that can better reconcile conservation and ecosystem management ideals.

Trophic compensation reinforces resistance: herbivory absorbs the increasing effects of multiple disturbances.

PubMed

Ghedini, Giulia; Russell, Bayden D; Connell, Sean D

2015-02-01

Disturbance often results in small changes in community structure, but the probability of transitioning to contrasting states increases when multiple disturbances combine. Nevertheless, we have limited insights into the mechanisms that stabilise communities, particularly how perturbations can be absorbed without restructuring (i.e. resistance). Here, we expand the concept of compensatory dynamics to include countervailing mechanisms that absorb disturbances through trophic interactions. By definition, 'compensation' occurs if a specific disturbance stimulates a proportional countervailing response that eliminates its otherwise unchecked effect. We show that the compounding effects of disturbances from local to global scales (i.e. local canopy-loss, eutrophication, ocean acidification) increasingly promote the expansion of weedy species, but that this response is countered by a proportional increase in grazing. Finally, we explore the relatively unrecognised role of compensatory effects, which are likely to maintain the resistance of communities to disturbance more deeply than current thinking allows. © 2015 John Wiley & Sons Ltd/CNRS.

A stable isotope ( δ13C, δ15N) model for the North Water food web: implications for evaluating trophodynamics and the flow of energy and contaminants

NASA Astrophysics Data System (ADS)

Hobson, Keith A.; Fisk, Aaron; Karnovsky, Nina; Holst, Meike; Gagnon, Jean-Marc; Fortier, Martin

The North Water Polynya is an area of high biological activity that supports large numbers of higher trophic-level organisms such as seabirds and marine mammals. An overall objective of the Upper Trophic-Level Group of the International North Water Polynya Study (NOW) was to evaluate carbon and contaminant flux through these high trophic-level (TL) consumers. Crucial to an evaluation of the role of such consumers, however, was the establishment of primary trophic linkages within the North Water food web. We used δ15N values of food web components from particulate organic matter (POM) through polar bears ( Ursus maritimus) to create a trophic-level model based on the assumptions that Calanus hyperboreus occupies TL 2.0 and there is a 2.4‰ trophic enrichment in 15N between birds and their diets, and a 3.8‰ trophic enrichment for all other components. This model placed the planktivorous dovekie ( Alle alle) at TL 3.3, ringed seal ( Phoca hispida) at TL 4.5, and polar bear at TL 5.5. The copepods C. hyperboreus, Chiridius glacialis and Euchaeta glacialis formed a trophic continuum (TL 2.0-3.0) from primary herbivore through omnivore to primary carnivore. Invertebrates were generally sorted according to planktonic, benthic and epibenthic feeding groups. Seabirds formed three trophic groups, with dovekie occupying the lowest, black-legged kittiwake ( Rissa tridactyla), northern fulmar ( Fulmarus glacialis), thick-billed murre ( Uria aalge), and ivory gull ( Pagophilia eburnea) intermediate (TL 3.9-4.0), and glaucous gull ( Larus hyperboreus) the highest (TL 4.6) trophic positions. Among marine mammals, walrus ( Odobenus rosmarus) occupied the lowest (TL 3.2) and bearded seal ( Erignathus barbatus), ringed seal, beluga whale ( Delphinapterus leucas), and narwhal ( Monodon monoceros) intermediate positions (TL 4.1-4.6). In addition to arctic cod ( Boreogadus saida), we suggest that lower trophic-level prey, in particular the amphipod Themisto libellula, contribute fundamentally in transferring energy and carbon flux to higher trophic-level seabirds and marine mammals. We measured PCB 153 among selected organisms to investigate the behavior of bioaccumulating contaminants within the food web. Our isotopic model confirmed the trophic magnification of PCB 153 in this high-Arctic food web due to a strong correlation between contaminant concentration and organism δ15N values, demonstrating the utility of combining isotopic and contaminant approaches to food-web studies. Stable-carbon isotope analysis confirmed an enrichment in 13C between POM and ice algae (-22.3 vs. -17.7‰). Benthic organisms were generally enriched in 13C compared to pelagic species. We discuss individual species isotopic data and the general utility of our stable isotope model for defining carbon flux and contaminant flow through the North Water food web.

Trophic transfer of essential elements in the clownfish Amphiprion ocellaris in the context of ocean acidification.

PubMed

Jacob, Hugo; Pouil, Simon; Lecchini, David; Oberhänsli, François; Swarzenski, Peter; Metian, Marc

2017-01-01

Little information exists on the effects of ocean acidification (OA) on the digestive and post-digestive processes in marine fish. Here, we investigated OA impacts (Δ pH = 0.5) on the trophic transfer of select trace elements in the clownfish Amphiprion ocellaris using radiotracer techniques. Assimilation efficiencies of three essential elements (Co, Mn and Zn) as well as their other short-term and long-term kinetic parameters in juvenile clownfish were not affected by this experimental pH change. In complement, their stomach pH during digestion were not affected by the variation in seawater pH. Such observations suggest that OA impacts do not affect element assimilation in these fish. This apparent pCO2 tolerance may imply that clownfish have the ability to self-regulate pH shifts in their digestive tract, or that they can metabolically accommodate such shifts. Such results are important to accurately assess future OA impacts on diverse marine biota, as such impacts are highly species specific, complex, and may be modulated by species-specific metabolic processes.

Trophic transfer of essential elements in the clownfish Amphiprion ocellaris in the context of ocean acidification

PubMed Central

Pouil, Simon; Lecchini, David; Oberhänsli, François; Swarzenski, Peter; Metian, Marc

2017-01-01

Little information exists on the effects of ocean acidification (OA) on the digestive and post-digestive processes in marine fish. Here, we investigated OA impacts (Δ pH = 0.5) on the trophic transfer of select trace elements in the clownfish Amphiprion ocellaris using radiotracer techniques. Assimilation efficiencies of three essential elements (Co, Mn and Zn) as well as their other short-term and long-term kinetic parameters in juvenile clownfish were not affected by this experimental pH change. In complement, their stomach pH during digestion were not affected by the variation in seawater pH. Such observations suggest that OA impacts do not affect element assimilation in these fish. This apparent pCO2 tolerance may imply that clownfish have the ability to self-regulate pH shifts in their digestive tract, or that they can metabolically accommodate such shifts. Such results are important to accurately assess future OA impacts on diverse marine biota, as such impacts are highly species specific, complex, and may be modulated by species-specific metabolic processes. PMID:28399186

Iron as a Cofactor That Limits the Promotion of Cyanobacteria in Lakes Across a Tropic Gradient

NASA Astrophysics Data System (ADS)

Sorichetti, R. J.; Creed, I. F.; Trick, C. G.

2014-12-01

The frequency and intensity of cyanobacterial blooms (cyanoblooms) is increasing globally. While cyanoblooms in eutrophic (nutrient-rich) freshwater lakes are expected to persist and worsen with climate change projections, many of the "new" cyanobloom reports pertain to oligotrophic (nutrient-poor) freshwater lakes with no prior history of cyanobloom occurrence. Under the pressures of a changing climate, there exists a critical research need to revisit existing conceptual models and identify cyanobloom regulating factors currently unaccounted for. Iron (Fe) is required in nearly all pathways of cyanobacterial macronutrient use, though its precise role in regulating cyanobacterial biomass across the lake trophic gradient is not fully understood. The hypotheses tested were: (1) cyanobacteria will predominate in lakes when bioavailable Fe concentration is low, and (2) cyanobacteria overcome this Fe limitation in all lakes using the siderophore-based Fe acquisition strategy to scavenge Fe providing a competitive advantage over other phytoplankton. These hypotheses were tested using natural lakes across an oligo-meso-eutrophic gradient across Canada. In all lakes sampled, the relative cyanobacterial biomass was highest at low predicted Fe bioavailability (< 1.0 × 10-19 mol L-1). Within this range of low bioavailable Fe, iron-binding organic ligands were measured. Concentrations of ligands with reactive hydroxamate moieties were positively correlated to cyanobacterial biomass in both the oligotrophic (r2 = 0.77, p < 0.001) and eutrophic (r2 = 0.81, p < 0.001) lakes suggesting a possible low-Fe mediated cellular origin, siderophores. Fe-binding ligands with catecholate-type binding sites were detected in all lakes, although lack of a relationship with cyanobacterial biomass and a significant relationship with dissolved organic carbon (DOC) in oligotrophic (r2 = 0.65, p < 0.001) and eutrophic (r2 = 0.65, p < 0.001) lakes may indicate an allochthonous source that is not used by cyanobacteria. These findings suggest that Fe serves as a possible cofactor that maintains cyanobacterial levels across a lake trophic gradient and that cyanobacteria invoke a similar Fe-scavenging system to overcome Fe limitation in lakes of all trophic status.

Trophic structure of pelagic species in the northwestern Mediterranean Sea

NASA Astrophysics Data System (ADS)

Albo-Puigserver, Marta; Navarro, Joan; Coll, Marta; Layman, Craig A.; Palomera, Isabel

2016-11-01

Ecological knowledge of food web interactions within pelagic marine communities is often limited, impairing our capabilities to manage these ecologically and economically important marine fish species. Here we used stable isotope analyses to investigate trophic interactions in the pelagic ecosystem of the northwestern Mediterranean Sea during 2012 and 2013. Our results suggest that European sardine, Sardina pilchardus, and anchovy, Engraulis encrasicolus, are consumers located at relatively low levels of the pelagic food web. Unexpectedly, the round sardinella, Sardinella aurita, appeared to be located at a higher trophic level than the other small pelagic fish species, although previous studies found similarity in their diets. Isotope data suggested that trophic niches of species within the genera Trachurus spp. and Scomber spp., were distinct. Atlantic bonito Sarda sarda, European hake Merluccius merluccius and European squid Loligo vulgaris, appeared to feed at higher trophic levels than other species. Despite some intraspecific seasonal variability for some species, community trophic structure appeared relatively stable through the year. These data provide an important step for developing models of food web dynamics in the northwestern Mediterranean Sea.

Trace elements in organisms of different trophic groups in the White Sea

NASA Astrophysics Data System (ADS)

Budko, D. F.; Demina, L. L.; Martynova, D. M.; Gorshkova, O. M.

2015-09-01

Concentrations of trace elements (Fe, Mn, Cu, Pb, Ni, Cr, Cd, As, Co, and Se) have been studied in different trophic groups of organisms: primary producers (seston, presented mostly by phytoplankton), primary consumers (mesozooplankton, macrozooplankton, and bivalves), secondary consumers (predatory macrozooplankton and starfish), and consumers of higher trophic levels (fish species), inhabiting the coastal zone of Kandalaksha Bay and the White Sea (Cape Kartesh). The concentrations of elements differ significantly for the size groups of Sagitta elegans (zooplankton) and blue mussel Mytilus edulis, as well as for the bone and muscle tissues of studied fish species, Atlantic cod Gadus morhua marisalbi and Atlantic wolffish Anarhichas lupus. The concentrations of all the studied elements were lower among the primary consumers and producers, but increased again at higher trophic levels, from secondary consumers to tertiary consumers ("mesozooplankton → macrozooplankton Sagitta elegans" and "mussels → starfish"). Ni and Pb tended to decline through the food chains seston→…→cod and mesozooplankton→…→stickleback. Only the concentrations of Fe increased in all the trophic chains along with the increase of the trophic level.

Trophic factors in neurologic disease.

PubMed

Stewart, S S; Appel, S H

1988-01-01

Recent studies suggest that diffusible factors released by neural targets enhance the survival, growth, and differentiation of neurons both peripherally and in the central nervous system. Evidence for such trophic factors exists for many of the neural systems involved in the degenerative neurologic diseases Alzheimer's disease, parkinsonism, and amyotrophic lateral sclerosis. It is our hypothesis that for each of these disorders there is both a primary insult and a secondary effect. The primary insult may have multiple etiologies, but the secondary effect is the result of retrograde degeneration. Such retrograde degeneration occurs because of an impairment of trophic factor function or an inadequacy of trophic effects to keep pace with the primary destructive process. Accordingly, it may be possible to exploit such trophic mechanisms to define further the pathobiology of neural degeneration and to develop specific treatments for currently incurable illnesses.

A trophic model of fringing coral reefs in Nanwan Bay, southern Taiwan suggests overfishing.

PubMed

Liu, Pi-Jen; Shao, Kwang-Tsao; Jan, Rong-Quen; Fan, Tung-Yung; Wong, Saou-Lien; Hwang, Jiang-Shiou; Chen, Jen-Ping; Chen, Chung-Chi; Lin, Hsing-Juh

2009-09-01

Several coral reefs of Nanwan Bay, Taiwan have recently undergone shifts to macroalgal or sea anemone dominance. Thus, a mass-balance trophic model was constructed to analyze the structure and functioning of the food web. The fringing reef model was comprised of 18 compartments, with the highest trophic level of 3.45 for piscivorous fish. Comparative analyses with other reef models demonstrated that Nanwan Bay was similar to reefs with high fishery catches. While coral biomass was not lower, fish biomass was lower than those of reefs with high catches. Consequently, the sums of consumption and respiratory flows and total system throughput were also decreased. The Nanwan Bay model potentially suggests an overfished status in which the mean trophic level of the catch, matter cycling, and trophic transfer efficiency are extremely reduced.

Bridging the gap between marine biogeochemical and fisheries sciences; configuring the zooplankton link

NASA Astrophysics Data System (ADS)

Mitra, Aditee; Castellani, Claudia; Gentleman, Wendy C.; Jónasdóttir, Sigrún H.; Flynn, Kevin J.; Bode, Antonio; Halsband, Claudia; Kuhn, Penelope; Licandro, Priscilla; Agersted, Mette D.; Calbet, Albert; Lindeque, Penelope K.; Koppelmann, Rolf; Møller, Eva F.; Gislason, Astthor; Nielsen, Torkel Gissel; St. John, Michael

2014-12-01

Exploring climate and anthropogenic impacts on marine ecosystems requires an understanding of how trophic components interact. However, integrative end-to-end ecosystem studies (experimental and/or modelling) are rare. Experimental investigations often concentrate on a particular group or individual species within a trophic level, while tropho-dynamic field studies typically employ either a bottom-up approach concentrating on the phytoplankton community or a top-down approach concentrating on the fish community. Likewise the emphasis within modelling studies is usually placed upon phytoplankton-dominated biogeochemistry or on aspects of fisheries regulation. In consequence the roles of zooplankton communities (protists and metazoans) linking phytoplankton and fish communities are typically under-represented if not (especially in fisheries models) ignored. Where represented in ecosystem models, zooplankton are usually incorporated in an extremely simplistic fashion, using empirical descriptions merging various interacting physiological functions governing zooplankton growth and development, and thence ignoring physiological feedback mechanisms. Here we demonstrate, within a modelled plankton food-web system, how trophic dynamics are sensitive to small changes in parameter values describing zooplankton vital rates and thus the importance of using appropriate zooplankton descriptors. Through a comprehensive review, we reveal the mismatch between empirical understanding and modelling activities identifying important issues that warrant further experimental and modelling investigation. These include: food selectivity, kinetics of prey consumption and interactions with assimilation and growth, form of voided material, mortality rates at different age-stages relative to prior nutrient history. In particular there is a need for dynamic data series in which predator and prey of known nutrient history are studied interacting under varied pH and temperature regimes.

Woody plant phylogenetic diversity mediates bottom-up control of arthropod biomass in species-rich forests.

PubMed

Schuldt, Andreas; Baruffol, Martin; Bruelheide, Helge; Chen, Simon; Chi, Xiulian; Wall, Marcus; Assmann, Thorsten

2014-09-01

Global change is predicted to cause non-random species loss in plant communities, with consequences for ecosystem functioning. However, beyond the simple effects of plant species richness, little is known about how plant diversity and its loss influence higher trophic levels, which are crucial to the functioning of many species-rich ecosystems. We analyzed to what extent woody plant phylogenetic diversity and species richness contribute to explaining the biomass and abundance of herbivorous and predatory arthropods in a species-rich forest in subtropical China. The biomass and abundance of leaf-chewing herbivores, and the biomass dispersion of herbivores within plots, increased with woody plant phylogenetic diversity. Woody plant species richness had much weaker effects on arthropods, but interacted with plant phylogenetic diversity to negatively affect the ratio of predator to herbivore biomass. Overall, our results point to a strong bottom-up control of functionally important herbivores mediated particularly by plant phylogenetic diversity, but do not support the general expectation that top-down predator effects increase with plant diversity. The observed effects appear to be driven primarily by increasing resource diversity rather than diversity-dependent primary productivity, as the latter did not affect arthropods. The strong effects of plant phylogenetic diversity and the overall weaker effects of plant species richness show that the diversity-dependence of ecosystem processes and interactions across trophic levels can depend fundamentally on non-random species associations. This has important implications for the regulation of ecosystem functions via trophic interaction pathways and for the way species loss may impact these pathways in species-rich forests.

One Year in the Lower St. Lawrence Estuary: Feeding Niche Separation of Two Co-existing Krill Species

NASA Astrophysics Data System (ADS)

Winkler, G.; Cabrol, J.; Sage, R.; Nozais, C.; Tremblay, R.; Starr, M.

2016-02-01

The lower St. Lawrence estuary (LSLE) is influenced by river discharge and saltwater inflow. Together with arctic water inflow and ice cover in winter a strong stratification occurs resulting in a cold intermediate layer (CIL) from spring to autumn. This stratification provides thermal habitats. Here, we focus on two krill species Thysanoessa raschii and Meganyctiphanes norvegica that aggregate in the CIL and the warmer deep water layer, respectively. Both species are known to migrate into the surface layer to feed and thus transfering energy through the food web by linking lower with higher trophic levels. However, their specific feeding biology and trophic interactions are poorly understood. We tested the following hypotheses: (1) the diets vary throughout the season depending on food availability, (2) similar to thermal habitat separation, trophic niche separation between T. raschii and M. norvegica occurs, characterized by herbivory in T. raschii and carnivory in M. norvegica. Trophic position and feeding behavior of theses krill populations were monitored throughout one year 2014-2015 using a stable isotope approach. The two species showed a seasonal shift in their trophic position being on a higher trophic level in summer than in spring and autumn, which did not correspond to phytoplankton or zooplankton availability. Within the trophic space of carbon and nitrogen stable isotopes M. norvegica showed a relatively stable position, whereas T. raschii covered a much larger space throughout the year. M. norvegica was always positioned at a higher trophic level than T. raschii. Results of a stable isotope mixing model (SIAR) revealed 50% phytoplankton and 50% copepods in the diet of M. norvegica, while T. raschii showed a higher proportion of ca. 70% phytoplankton in its diet. Both species exploited several trophic levels, but in different proportions, thereby minimizing diet overlap, suggesting a further mechanism to enhance stable co-existence of these krill species in the highly stratified LSLE.

Not all jellyfish are equal: isotopic evidence for inter- and intraspecific variation in jellyfish trophic ecology.

PubMed

Fleming, Nicholas E C; Harrod, Chris; Newton, Jason; Houghton, Jonathan D R

2015-01-01

Jellyfish are highly topical within studies of pelagic food-webs and there is a growing realisation that their role is more complex than once thought. Efforts being made to include jellyfish within fisheries and ecosystem models are an important step forward, but our present understanding of their underlying trophic ecology can lead to their oversimplification in these models. Gelatinous zooplankton represent a polyphyletic assemblage spanning >2,000 species that inhabit coastal seas to the deep-ocean and employ a wide variety of foraging strategies. Despite this diversity, many contemporary modelling approaches include jellyfish as a single functional group feeding at one or two trophic levels at most. Recent reviews have drawn attention to this issue and highlighted the need for improved communication between biologists and theoreticians if this problem is to be overcome. We used stable isotopes to investigate the trophic ecology of three co-occurring scyphozoan jellyfish species (Aurelia aurita, Cyanea lamarckii and C. capillata) within a temperate, coastal food-web in the NE Atlantic. Using information on individual size, time of year and δ (13)C and δ (15)N stable isotope values, we examined: (1) whether all jellyfish could be considered as a single functional group, or showed distinct inter-specific differences in trophic ecology; (2) Were size-based shifts in trophic position, found previously in A. aurita, a common trait across species?; (3) When considered collectively, did the trophic position of three sympatric species remain constant over time? Differences in δ (15)N (trophic position) were evident between all three species, with size-based and temporal shifts in δ (15)N apparent in A. aurita and C. capillata. The isotopic niche width for all species combined increased throughout the season, reflecting temporal shifts in trophic position and seasonal succession in these gelatinous species. Taken together, these findings support previous assertions that jellyfish require more robust inclusion in marine fisheries or ecosystem models.

Not all jellyfish are equal: isotopic evidence for inter- and intraspecific variation in jellyfish trophic ecology

PubMed Central

Fleming, Nicholas E.C.; Newton, Jason; Houghton, Jonathan D.R.

2015-01-01

Jellyfish are highly topical within studies of pelagic food-webs and there is a growing realisation that their role is more complex than once thought. Efforts being made to include jellyfish within fisheries and ecosystem models are an important step forward, but our present understanding of their underlying trophic ecology can lead to their oversimplification in these models. Gelatinous zooplankton represent a polyphyletic assemblage spanning >2,000 species that inhabit coastal seas to the deep-ocean and employ a wide variety of foraging strategies. Despite this diversity, many contemporary modelling approaches include jellyfish as a single functional group feeding at one or two trophic levels at most. Recent reviews have drawn attention to this issue and highlighted the need for improved communication between biologists and theoreticians if this problem is to be overcome. We used stable isotopes to investigate the trophic ecology of three co-occurring scyphozoan jellyfish species (Aurelia aurita, Cyanea lamarckii and C. capillata) within a temperate, coastal food-web in the NE Atlantic. Using information on individual size, time of year and δ13C and δ15N stable isotope values, we examined: (1) whether all jellyfish could be considered as a single functional group, or showed distinct inter-specific differences in trophic ecology; (2) Were size-based shifts in trophic position, found previously in A. aurita, a common trait across species?; (3) When considered collectively, did the trophic position of three sympatric species remain constant over time? Differences in δ15N (trophic position) were evident between all three species, with size-based and temporal shifts in δ15N apparent in A. aurita and C. capillata. The isotopic niche width for all species combined increased throughout the season, reflecting temporal shifts in trophic position and seasonal succession in these gelatinous species. Taken together, these findings support previous assertions that jellyfish require more robust inclusion in marine fisheries or ecosystem models. PMID:26244116

Amino Acid Isotope Incorporation and Enrichment Factors in Pacific Bluefin Tuna, Thunnus orientalis

PubMed Central

Bradley, Christina J.; Madigan, Daniel J.; Block, Barbara A.; Popp, Brian N.

2014-01-01

Compound specific isotopic analysis (CSIA) of amino acids has received increasing attention in ecological studies in recent years due to its ability to evaluate trophic positions and elucidate baseline nutrient sources. However, the incorporation rates of individual amino acids into protein and specific trophic discrimination factors (TDFs) are largely unknown, limiting the application of CSIA to trophic studies. We determined nitrogen turnover rates of individual amino acids from a long-term (up to 1054 days) laboratory experiment using captive Pacific bluefin tuna, Thunnus orientalis (PBFT), a large endothermic pelagic fish fed a controlled diet. Small PBFT (white muscle δ15N∼11.5‰) were collected in San Diego, CA and transported to the Tuna Research and Conservation Center (TRCC) where they were fed a controlled diet with high δ15N values relative to PBFT white muscle (diet δ15N∼13.9‰). Half-lives of trophic and source amino acids ranged from 28.6 to 305.4 days and 67.5 to 136.2 days, respectively. The TDF for the weighted mean values of amino acids was 3.0 ‰, ranging from 2.2 to 15.8 ‰ for individual combinations of 6 trophic and 5 source amino acids. Changes in the δ15N values of amino acids across trophic levels are the underlying drivers of the trophic 15N enrichment. Nearly all amino acid δ15N values in this experiment changed exponentially and could be described by a single compartment model. Significant differences in the rate of 15N incorporation were found for source and trophic amino acids both within and between these groups. Varying half-lives of individual amino acids can be applied to migratory organisms as isotopic clocks, determining the length of time an individual has spent in a new environment. These results greatly enhance the ability to interpret compound specific isotope analyses in trophic studies. PMID:24465724

Examining predator-prey body size, trophic level and body mass across marine and terrestrial mammals.

PubMed

Tucker, Marlee A; Rogers, Tracey L

2014-12-22

Predator-prey relationships and trophic levels are indicators of community structure, and are important for monitoring ecosystem changes. Mammals colonized the marine environment on seven separate occasions, which resulted in differences in species' physiology, morphology and behaviour. It is likely that these changes have had a major effect upon predator-prey relationships and trophic position; however, the effect of environment is yet to be clarified. We compiled a dataset, based on the literature, to explore the relationship between body mass, trophic level and predator-prey ratio across terrestrial (n = 51) and marine (n = 56) mammals. We did not find the expected positive relationship between trophic level and body mass, but we did find that marine carnivores sit 1.3 trophic levels higher than terrestrial carnivores. Also, marine mammals are largely carnivorous and have significantly larger predator-prey ratios compared with their terrestrial counterparts. We propose that primary productivity, and its availability, is important for mammalian trophic structure and body size. Also, energy flow and community structure in the marine environment are influenced by differences in energy efficiency and increased food web stability. Enhancing our knowledge of feeding ecology in mammals has the potential to provide insights into the structure and functioning of marine and terrestrial communities. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Persistence of trophic hotspots and relation to human impacts within an upwelling marine ecosystem.

PubMed

Santora, Jarrod A; Sydeman, William J; Schroeder, Isaac D; Field, John C; Miller, Rebecca R; Wells, Brian K

2017-03-01

Human impacts (e.g., fishing, pollution, and shipping) on pelagic ecosystems are increasing, causing concerns about stresses on marine food webs. Maintaining predator-prey relationships through protection of pelagic hotspots is crucial for conservation and management of living marine resources. Biotic components of pelagic, plankton-based, ecosystems exhibit high variability in abundance in time and space (i.e., extreme patchiness), requiring investigation of persistence of abundance across trophic levels to resolve trophic hotspots. Using a 26-yr record of indicators for primary production, secondary (zooplankton and larval fish), and tertiary (seabirds) consumers, we show distributions of trophic hotspots in the southern California Current Ecosystem result from interactions between a strong upwelling center and a productive retention zone with enhanced nutrients, which concentrate prey and predators across multiple trophic levels. Trophic hotspots also overlap with human impacts, including fisheries extraction of coastal pelagic and groundfish species, as well as intense commercial shipping traffic. Spatial overlap of trophic hotspots with fisheries and shipping increases vulnerability of the ecosystem to localized depletion of forage fish, ship strikes on marine mammals, and pollution. This study represents a critical step toward resolving pelagic areas of high conservation interest for planktonic ecosystems and may serve as a model for other ocean regions where ecosystem-based management and marine spatial planning of pelagic ecosystems is warranted. © 2016 by the Ecological Society of America.

Microbes are trophic analogues of arthropods, mammals, and fish: Isotopic fingerprinting unites ‘green’ and ‘brown’ food webs

USDA-ARS?s Scientific Manuscript database

This work addresses a cross-cutting issue within the field of food-web ecology—the integration of the microbiome into trophic hierarchies. The nature and degree to which microbes may reconfigure the trophic identities of carnivore and omnivore groups have remained surprisingly unresolved. This means...

Intra-trophic isotopic discrimination of 15N/14N for amino acids in autotrophs: Implications for nitrogen dynamics in ecological studies

USDA-ARS?s Scientific Manuscript database

Metabolic reactions within heterotrophs cause discrimination in their stable nitrogen isotopic composition of amino acids (d15NAA) compared to their diets. Ecologists have exploited this measurable inter-trophic discrimination in the d15NAA value to estimate the trophic positions of heterotrophic an...

Comparing compound-specific and bulk stable nitrogen isotope trophic discrimination factors across multiple freshwater fish species and diets

USDA-ARS?s Scientific Manuscript database

The use of nitrogen stable isotopes for estimation of animal trophic position has become an indispensable approach in food web ecology. Compound-specific isotope analysis of amino acids is a new approach for estimating trophic position that may overcome key issues associated with nitrogen stable iso...

Recovery of African wild dogs suppresses prey but does not trigger a trophic cascade.

PubMed

Ford, Adam T; Goheen, Jacob R; Augustine, David J; Kinnaird, Margaret F; O'Brien, Timothy G; Palmer, Todd M; Pringle, Robert M; Woodroffe, Rosie

2015-10-01

Increasingly, the restoration of large carnivores is proposed as a means through which to restore community structure and ecosystem function via trophic cascades. After a decades-long absence, African wild dogs (Lycaon pictus) recolonized the Laikipia Plateau in central Kenya, which we hypothesized would trigger a trophic cascade via suppression of their primary prey (dik-dik, Madoqua guentheri) and the subsequent relaxation of browsing pressure on trees. We tested the trophic-cascade hypothesis using (1) a 14-year time series of wild dog abundance; (2) surveys of dik-dik population densities conducted before and after wild dog recovery; and (3) two separate, replicated, herbivore-exclusion experiments initiated before and after wild dog recovery. The dik-dik population declined by 33% following wild dog recovery, which is best explained by wild dog predation. Dik-dik browsing suppressed tree abundance, but the strength of suppression did not differ between before and after wild dog recovery. Despite strong, top-down limitation between adjacent trophic levels (carnivore-herbivore and herbivore-plant), a trophic cascade did not occur, possibly because of a time lag in indirect effects, variation in rainfall, and foraging by herbivores other than dik-dik. Our ability to reject the trophic-cascade hypothesis required two important approaches: (1) temporally replicated herbivore exclusions, separately established before and after wild dog recovery; and (2) evaluating multiple drivers of variation in the abundance of dik-dik and trees. While the restoration of large carnivores is often a conservation priority, our results suggest that indirect effects are mediated by ecological context, and that trophic cascades are not a foregone conclusion of such recoveries.

Predator diversity and environmental change modify the strengths of trophic and nontrophic interactions.

PubMed

Sentis, Arnaud; Gémard, Charlène; Jaugeon, Baptiste; Boukal, David S

2017-07-01

Understanding the dependence of species interaction strengths on environmental factors and species diversity is crucial to predict community dynamics and persistence in a rapidly changing world. Nontrophic (e.g. predator interference) and trophic components together determine species interaction strengths, but the effects of environmental factors on these two components remain largely unknown. This impedes our ability to fully understand the links between environmental drivers and species interactions. Here, we used a dynamical modelling framework based on measured predator functional responses to investigate the effects of predator diversity, prey density, and temperature on trophic and nontrophic interaction strengths within a freshwater food web. We found that (i) species interaction strengths cannot be predicted from trophic interactions alone, (ii) nontrophic interaction strengths vary strongly among predator assemblages, (iii) temperature has opposite effects on trophic and nontrophic interaction strengths, and (iv) trophic interaction strengths decrease with prey density, whereas the dependence of nontrophic interaction strengths on prey density is concave up. Interestingly, the qualitative impacts of temperature and prey density on the strengths of trophic and nontrophic interactions were independent of predator identity, suggesting a general pattern. Our results indicate that taking multiple environmental factors and the nonlinearity of density-dependent species interactions into account is an important step towards a better understanding of the effects of environmental variations on complex ecological communities. The functional response approach used in this study opens new avenues for (i) the quantification of the relative importance of the trophic and nontrophic components in species interactions and (ii) a better understanding how environmental factors affect these interactions and the dynamics of ecological communities. © 2016 John Wiley & Sons Ltd.

Trophic Strategies of a Non-Native and a Native Amphibian Species in Shared Ponds

PubMed Central

San Sebastián, Olatz; Navarro, Joan; Llorente, Gustavo A.; Richter-Boix, Álex

2015-01-01

One of the critical factors for understanding the establishment, success and potential impact on native species of an introduced species is a thorough knowledge of how these species manage trophic resources. Two main trophic strategies for resource acquisition have been described: competition and opportunism. In the present study our objective was to identify the main trophic strategies of the non-native amphibian Discoglossus pictus and its potential trophic impact on the native amphibian Bufo calamita. We determine whether D. pictus exploits similar trophic resources to those exploited by the native B. calamita (competition hypothesis) or alternative resources (opportunistic hypothesis). To this end, we analyzed the stable isotope values of nitrogen and carbon in larvae of both species, in natural ponds and in controlled laboratory conditions. The similarity of the δ15N and δ13C values in the two species coupled with isotopic signal variation according to pond conditions and niche partitioning when they co-occurred indicated dietary competition. Additionally, the non-native species was located at higher levels of trophic niches than the native species and B. calamita suffered an increase in its standard ellipse area when it shared ponds with D. pictus. These results suggest niche displacement of B. calamita to non-preferred resources and greater competitive capacity of D. pictus in field conditions. Moreover, D. pictus showed a broader niche than the native species in all conditions, indicating increased capacity to exploit the diversity of resources; this may indirectly favor its invasiveness. Despite the limitations of this study (derived from potential variability in pond isotopic signals), the results support previous experimental studies. All the studies indicate that D. pictus competes with B. calamita for trophic resources with potential negative effects on the fitness of the latter. PMID:26101880

Trophic position increases with thermocline depth in yellowfin and bigeye tuna across the Western and Central Pacific Ocean

NASA Astrophysics Data System (ADS)

Houssard, Patrick; Lorrain, Anne; Tremblay-Boyer, Laura; Allain, Valérie; Graham, Brittany S.; Menkes, Christophe E.; Pethybridge, Heidi; Couturier, Lydie I. E.; Point, David; Leroy, Bruno; Receveur, Aurore; Hunt, Brian P. V.; Vourey, Elodie; Bonnet, Sophie; Rodier, Martine; Raimbault, Patrick; Feunteun, Eric; Kuhnert, Petra M.; Munaron, Jean-Marie; Lebreton, Benoit; Otake, Tsuguo; Letourneur, Yves

2017-05-01

Estimates of trophic position are used to validate ecosystem models and understand food web structure. A consumer's trophic position can be estimated by the stable nitrogen isotope values (δ15N) of its tissue, once the baseline isotopic variability has been accounted for. Our study established the first data-driven baseline δ15N isoscape for the Western and Central Pacific Ocean using particulate organic matter. Bulk δ15N analysis on 1039 muscle tissue of bigeye and yellowfin tuna were conducted together with amino acid compound-specific δ15N analysis (AA-CSIA) on a subset of 21 samples. Both particulate organic matter and tuna bulk δ15N values varied by more than 10‰ across the study area. Fine-scaled trophic position maps were constructed and revealed higher tuna trophic position (by ∼1) in the southern latitudes compared to the equator. AA-CSIA confirmed these spatial patterns for bigeye and, to a lesser extent, yellowfin tuna. Using generalized additive models, spatial variations of tuna trophic positions were mainly related to the depth of the 20°C isotherm, a proxy for the thermocline behavior, with higher tuna trophic position estimates at greater thermocline depths. We hypothesized that a deeper thermocline would increase tuna vertical habitat and access to mesopelagic prey of higher trophic position. Archival tagging data further suggested that the vertical habitat of bigeye tuna was deeper in the southern latitudes than at the equator. These results suggest the importance of thermocline depth in influencing tropical tuna diet, which affects their vulnerability to fisheries, and may be altered by climate change.

Coastal habitats as surrogates for taxonomic, functional and trophic structures of benthic faunal communities.

PubMed

Törnroos, Anna; Nordström, Marie C; Bonsdorff, Erik

2013-01-01

Due to human impact, there is extensive degradation and loss of marine habitats, which calls for measures that incorporate taxonomic as well as functional and trophic aspects of biodiversity. Since such data is less easily quantifiable in nature, the use of habitats as surrogates or proxies for biodiversity is on the rise in marine conservation and management. However, there is a critical gap in knowledge of whether pre-defined habitat units adequately represent the functional and trophic structure of communities. We also lack comparisons of different measures of community structure in terms of both between- (β) and within-habitat (α) variability when accounting for species densities. Thus, we evaluated a priori defined coastal habitats as surrogates for traditional taxonomic, functional and trophic zoobenthic community structure. We focused on four habitats (bare sand, canopy-forming algae, seagrass above- and belowground), all easily delineated in nature and defined through classification systems. We analyzed uni- and multivariate data on species and trait diversity as well as stable isotope ratios of benthic macrofauna. A good fit between habitat types and taxonomic and functional structure was found, although habitats were more similar functionally. This was attributed to within-habitat heterogeneity so when habitat divisions matched the taxonomic structure, only bare sand was functionally distinct. The pre-defined habitats did not meet the variability of trophic structure, which also proved to differentiate on a smaller spatial scale. The quantification of trophic structure using species density only identified an epi- and an infaunal unit. To summarize the results we present a conceptual model illustrating the match between pre-defined habitat types and the taxonomic, functional and trophic community structure. Our results show the importance of including functional and trophic aspects more comprehensively in marine management and spatial planning.

Functionally diverse reef-fish communities ameliorate coral disease.

PubMed

Raymundo, Laurie J; Halford, Andrew R; Maypa, Aileen P; Kerr, Alexander M

2009-10-06

Coral reefs, the most diverse of marine ecosystems, currently experience unprecedented levels of degradation. Diseases are now recognized as a major cause of mortality in reef-forming corals and are complicit in phase shifts of reef ecosystems to algal-dominated states worldwide. Even so, factors contributing to disease occurrence, spread, and impact remain poorly understood. Ecosystem resilience has been linked to the conservation of functional diversity, whereas overfishing reduces functional diversity through cascading, top-down effects. Hence, we tested the hypothesis that reefs with trophically diverse reef fish communities have less coral disease than overfished reefs. We surveyed reefs across the central Philippines, including well-managed marine protected areas (MPAs), and found that disease prevalence was significantly negatively correlated with fish taxonomic diversity. Further, MPAs had significantly higher fish diversity and less disease than unprotected areas. We subsequently investigated potential links between coral disease and the trophic components of fish diversity, finding that only the density of coral-feeding chaetodontid butterflyfishes, seldom targeted by fishers, was positively associated with disease prevalence. These previously uncharacterized results are supported by a second large-scale dataset from the Great Barrier Reef. We hypothesize that members of the charismatic reef-fish family Chaetodontidae are major vectors of coral disease by virtue of their trophic specialization on hard corals and their ecological release in overfished areas, particularly outside MPAs.

Instability of Water Quality of a Shallow, Polymictic, Flow-Through Lake.

PubMed

Ferencz, Beata; Dawidek, Jarosław; Toporowska, Magdalena

2018-01-01

This paper describes catchment processes that favor the trophic instability of a shallow polymictic lake, in which a shift from eutrophy to hypertrophy occurs rapidly. In the lake, in 2007, the winter discharge maximum and an intensive precipitation (monthly sums exceeded 60 mm) in a vegetation season were observed. In 2007, the cyanobacterial blooms disappeared and the water trophy decreased. Total phosphorus (TP) was the main factor determining the high trophic status of the lake. The TP retention resulted from a quick flow of two inflows: QI1 (r = 0.64) and QI2 (0.56), and the base flow of tributary 1 (0.62). A significant negative correlation between TP and precipitation ( r  = - 0.54) was observed. Both the surface and the groundwater inflow of I4 showed a positive correlation with the retention of PO 4 ( r  = 0.67 and r  = 0.60, respectively), whereas the outlet discharge determined RNO 3 ( r  = 0.57). The trophy of Lake Syczyńskie was determined by the relationship between nutrient input and export, expressed as the ionic retention, Carlson's trophic state index (TSI), and phytoplankton abundance. The results showed that many factors influence the stability of water quality in small, polymictic lakes. However, in the studied lake, intense precipitation and winter discharge maxima (particularly base flow) prevented summer cyanobacterial blooms.

Shift in a Large River Fish Assemblage: Body-Size and Trophic Structure Dynamics

PubMed Central

Broadway, Kyle J.; Pyron, Mark; Gammon, James R.; Murry, Brent A.

2015-01-01

As the intensity and speed of environmental change increase at both local and global scales it is imperative that we gain a better understanding of the ecological implications of community shifts. While there has been substantial progress toward understanding the drivers and subsequent responses of community change (e.g. lake trophic state), the ecological impacts of food web changes are far less understood. We analyzed Wabash River fish assemblage data collected from 1974-2008, to evaluate temporal variation in body-size structure and functional group composition. Two parameters derived from annual community size-spectra were our major response variables: (1) the regression slope is an index of ecological efficiency and predator-prey biomass ratios, and (2) spectral elevation (regression midpoint height) is a proxy for food web capacity. We detected a large assemblage shift, over at least a seven year period, defined by dramatic changes in abundance (measured as catch-per-unit-effort) of the dominant functional feeding groups among two time periods; from an assemblage dominated by planktivore-omnivores to benthic invertivores. There was a concurrent increase in ecological efficiency (slopes increased over time) following the shift associated with an increase in large-bodied low trophic level fish. Food web capacity remained relatively stable with no clear temporal trends. Thus, increased ecological efficiency occurred simultaneous to a compensatory response that shifted biomass among functional feeding groups. PMID:25902144

Radionuclides in bats using a contaminated pond on the Nevada National Security Site, USA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warren, Ronald W.; Hall, Derek B.; Greger, Paul D.

In this study, perched groundwater percolating through radionuclide contamination in the E Tunnel Complex on the Nevada National Security Site, formerly the Nevada Test Site, emerges and is stored in a series of ponds making it available to wildlife, including bats. Since many bat species using the ponds are considered sensitive or protected/regulated and little information is available on dose to bats from radioactive water sources, bats were sampled to determine if the dose they were receiving exceeded the United States Department of Energy dose limit of 1.0E-3 Gy/day. Radionuclide concentrations in water, sediment, and flying insects were also measuredmore » as input parameters to the dose rate model and to examine trophic level relationships. The RESRAD-Biota model was used to calculate dose rates to bats using different screening levels. Efficacy of RESRAD-Biota and suggested improvements are discussed. Finally, dose to bats foraging and drinking at these ponds is well below the dose limit set to protect terrestrial biota populations.« less

Microglia in the Retina: Roles in Development, Maturity, and Disease.

PubMed

Silverman, Sean M; Wong, Wai T

2018-05-31

Microglia, the primary resident immune cell type, constitute a key population of glia in the retina. Recent evidence indicates that microglia play significant functional roles in the retina at different life stages. During development, retinal microglia regulate neuronal survival by exerting trophic influences and influencing programmed cell death. During adulthood, ramified microglia in the plexiform layers interact closely with synapses to maintain synaptic structure and function that underlie the retina's electrophysiological response to light. Under pathological conditions, retinal microglia participate in potentiating neurodegeneration in diseases such as glaucoma, retinitis pigmentosa, and age-related neurodegeneration by producing proinflammatory neurotoxic cytokines and removing living neurons via phagocytosis. Modulation of pathogenic microglial activation states and effector mechanisms has been linked to neuroprotection in animal models of retinal diseases. These findings have led to the design of early proof-of-concept clinical trials with microglial modulation as a therapeutic strategy. Expected final online publication date for the Annual Review of Vision Science Volume 4 is September 15, 2018. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Radionuclides in bats using a contaminated pond on the Nevada National Security Site, USA

DOE PAGES

Warren, Ronald W.; Hall, Derek B.; Greger, Paul D.

2014-01-03

In this study, perched groundwater percolating through radionuclide contamination in the E Tunnel Complex on the Nevada National Security Site, formerly the Nevada Test Site, emerges and is stored in a series of ponds making it available to wildlife, including bats. Since many bat species using the ponds are considered sensitive or protected/regulated and little information is available on dose to bats from radioactive water sources, bats were sampled to determine if the dose they were receiving exceeded the United States Department of Energy dose limit of 1.0E-3 Gy/day. Radionuclide concentrations in water, sediment, and flying insects were also measuredmore » as input parameters to the dose rate model and to examine trophic level relationships. The RESRAD-Biota model was used to calculate dose rates to bats using different screening levels. Efficacy of RESRAD-Biota and suggested improvements are discussed. Finally, dose to bats foraging and drinking at these ponds is well below the dose limit set to protect terrestrial biota populations.« less

Water-quality characteristics of Michigan's inland lakes, 2001-10

USGS Publications Warehouse

Fuller, L.M.; Taricska, C.K.

2012-01-01

The U.S. Geological Survey and the Michigan Department of Environmental Quality (MDEQ) jointly monitored for selected water-quality constituents and properties of inland lakes during 2001–10 as part of Michigan's Lake Water-Quality Assessment program. During 2001–10, 866 lake basins from 729 inland lakes greater than 25 acres were monitored for baseline water-quality conditions and trophic status. This report summarizes the water-quality characteristics and trophic conditions of the monitored lakes throughout the State; the data include vertical-profile measurements, nutrient measurements at three discrete depths, Secchi-disk transparency (SDT) measurements, and chlorophyll a measurements for the spring and summer, with major ions and other chemical indicators measured during the spring at mid-depth and color during the summer from near-surface samples. In about 75 percent of inland lake deep basins (index stations), trophic characteristics were associated with oligotrophic or mesotrophic conditions; 5 percent or less were categorized as hypereutrophic, and 80 percent of hypereutrophic lakes had a maximum depth of 30 feet or less. Comparison of spring and summer measurements shows that water clarity based on SDT measurements were clearer in the spring than in the summer for 63 percent of lakes. For near-surface measurements made in spring, 97 percent of lakes can be considered phosphorus limited and less than half a percent nitrogen limited; for summer measurements, 96 percent of lakes can be considered phosphorus limited and less than half a percent nitrogen limited. Spatial patterns of major ions, alkalinity, and hardness measured in the spring at mid-depth all showed lower values in the Upper Peninsula of Michigan and a southward increase toward the southern areas of the Lower Peninsula, though the location of increase varied by constituent. A spatial analysis of the data based on U.S. Environmental Protection Agency Level III Ecoregions separated potassium, sulfate, and chloride concentrations fairly well, with a pattern of lower values in northern ecoregions trending toward higher values in southern ecoregions; lower and higher concentrations of magnesium, hardness, calcium, and alkalinity were well separated, but middle-range concentrations in central Michigan ecoregions were mixed. The highest concentrations of chloride and sodium were in the southeastern area of the Lower Peninsula. Lakes with multiple basins showed few statistically significant differences in constituent concentrations at the 95-percent confidence level among combinations of depths between basins. The most statistically significant differences were found for water temperature, with significant differences in somewhat less than half the combinations in the spring and just a few combinations in the summer. The lack of significant differences between major basins of multibasin lakes indicates that monitoring of trophic characteristics in all major basins might not be necessary for the majority of constituents in future sampling programs. Trophic characteristics based on the 2001–10 dataset were compared to trophic characteristics resulting from other Michigan sampling programs, including the volunteer Cooperative Lakes Monitoring Program coordinated by the MDEQ (measurements on 250 lakes in 2011), trophic-state predictions produced by relating existing measurements to remotely sensed data (measurements for about 3,000 lakes), and the National Lakes Assessment (NLA) statistically valid, probability-designed lakes program (measurements for 50 lakes in Michigan and about 1,100 lakes nationally). A higher percentage of oligotrophic lakes resulted when using SDT from the volunteer data and the 2001–10 dataset than when using the predicted measurements from remotely sensed data or the NLA. Comparing trophic characteristics from differently designed programs provides multiple interpretations of lake water-quality status in Michigan lakes. No directional statistically significant difference was found at the 95-percent confidence level among historical nutrients and trophic characteristics when comparing 445 lakes with historical data for 1974–84 with the 2001–10 dataset, though SDT did show statistically significant differences at the 95-percent confidence level. Depending on the primary indicator, 50–66 percent of lakes did not change trophic-status class, 13–23 percent moved towards the oligotrophic end of the TSI scale, and 20–25 percent moved a class towards the eutrophic end of the TSI scale. Increasing percentages of urban-dominant land cover in the drainage areas of lakes had a more positive correlation with chloride concentration than did increased percentages of other land-cover classes; there was also a slight correlation of urban-dominant land cover and calcium concentration. Removing data for lakes in southeastern Lower Michigan, known from previous reports to be higher in chloride, still resulted in a positive relation even though the coefficient of determination (R2 value) decreased from 0.55 to 0.39. Dominant land-cover drainage areas were not strongly related to nutrients with respect to a linear relation, nor were lake drainage-area sizes.

Annual Nutrient Loadings, Primary Productivity, and Trophic State of Lake Koocanusa, Montana and British Columbia, 1972-80

USGS Publications Warehouse

Woods, Paul F.

1982-01-01

Limnological data collected at Lake Koocanusa were used to investigate the relationship of nutrient loadings, primary productivity, and trophic state of the reservoir during 1972-80. The reservoir, on the Kootenai River, was impounded by Libby Dam on March 21, 1972. Manipulation of the 7.16-cubic-kilometer reservoir for flood control, its primary function, created large fluctuations in reservoir volume and produced annual lake-filling times that ranged from 0.14 to 0.66 year. Loadings of nitrogen and phosphorus prior to and following impoundment of Lake Koocanusa were found to be large enough to predict eutrophic conditions. Beginning in 1976, total phosphorus loadings, but not total nitrogen loadings, were substantially reduced following improvements in waste-water treatment at a fertilizer plant located upstream from the reservoir. The closure of Libby Dam substantially reduced loadings of nitrogen and phosphorus downstream from Lake Koocanusa. On the average, the reservoir retained 63 percent of its influent loading of total phosphorus and 25 percent of its influent loading of total nitrogen. Daily areal and volumetric primary productivity varied widely in each year at four sampled limnological stations. During the 9 years studied, daily areal primary productivity, in milligrams of carbon fixed per square meter, ranged from 0.4 to 420.0; the mean of the 313 sampled days was 128.5. Annual areal primary productivity ranged from 23.2 to 38.5 grams of carbon fixed per square meter and thereby categorized Lake Koocanusa as oligotrophic. The relationship of annual areal primary productivity and 12 selected environmental variables was determined by multiple regression analysis. One of the models that was derived used two variables-annual euphotic zone depth and annual areal phosphorus loading-and accounted for 62.0 percent of the variation in annual areal primary productivity. The distribution of chlorophyll a within the water column indicated that, on the average, more than one-half of the phytoplankton in the reservoir was beneath the euphotic zone. These results support the hypothesis that the reservoir's weak thermal structure had allowed circulation of phytoplankton out of the euphotic zone. The trophic state of Lake Koocanusa was categorized as eutrophic when based on the relationship of the nutrient loadings and the reservoir's ratio of mean depth to hydraulic-residence time. This result conflicted with the oligotrophic ranking the reservoir received based on its areal primary productivity. The discrepancy in trophic state was attributed mainly to the failure of nutrient loading models to adequately account for physical processes within reservoirs. Part of the nutrient loading that entered Lake Koocanusa was unavailable to phytoplankton because the nutrients were carried beneath the euphotic zone by large volumes of interflow and underflow. Another part of the nutrient loading was adsorbed to suspended sediment and removed from the water column. Thus, phytoplankton primary productivity was controlled not only by nutrients, but also by other limno logical processes.

Wolves trigger a trophic cascade to berries as alternative food for grizzly bears.

PubMed

Ripple, William J; Beschta, Robert L; Fortin, Jennifer K; Robbins, Charles T

2015-05-01

This is a Forum article in response to: Barber-Meyer, S. (2015) Trophic cascades from wolves to grizzly bears or changing abundance of bears and alternate foods? Journal of Animal Ecology, 83, doi: 10.1111/1365-2656.12338. We used multiple data sets and study areas as well as several lines of evidence to investigate potential trophic linkages in Yellowstone National Park. Our results suggest that a trophic cascade from wolves to elk to berry production to berry consumption by grizzly bears may now be underway in the Park. © 2015 The Authors. Journal of Animal Ecology © 2015 British Ecological Society.

Trophic Strategies of Unicellular Plankton.

PubMed

Chakraborty, Subhendu; Nielsen, Lasse Tor; Andersen, Ken H

2017-04-01

Unicellular plankton employ trophic strategies ranging from pure photoautotrophs over mixotrophy to obligate heterotrophs (phagotrophs), with cell sizes from 10 -8 to 1 μg C. A full understanding of how trophic strategy and cell size depend on resource environment and predation is lacking. To this end, we develop and calibrate a trait-based model for unicellular planktonic organisms characterized by four traits: cell size and investments in phototrophy, nutrient uptake, and phagotrophy. We use the model to predict how optimal trophic strategies depend on cell size under various environmental conditions, including seasonal succession. We identify two mixotrophic strategies: generalist mixotrophs investing in all three investment traits and obligate mixotrophs investing only in phototrophy and phagotrophy. We formulate two conjectures: (1) most cells are limited by organic carbon; however, small unicellulars are colimited by organic carbon and nutrients, and only large photoautotrophs and smaller mixotrophs are nutrient limited; (2) trophic strategy is bottom-up selected by the environment, while optimal size is top-down selected by predation. The focus on cell size and trophic strategies facilitates general insights into the strategies of a broad class of organisms in the size range from micrometers to millimeters that dominate the primary and secondary production of the world's oceans.

Trophic Mode-Dependent Proteomic Analysis Reveals Functional Significance of Light-Independent Chlorophyll Synthesis in Synechocystis sp. PCC 6803.

PubMed

Fang, Longfa; Ge, Haitao; Huang, Xiahe; Liu, Ye; Lu, Min; Wang, Jinlong; Chen, Weiyang; Xu, Wu; Wang, Yingchun

2017-01-09

The photosynthetic model organism Synechocystis sp. PCC 6803 can grow in different trophic modes, depending on the availability of light and exogenous organic carbon source. However, how the protein profile changes to facilitate the cells differentially propagate in different modes has not been comprehensively investigated. Using isobaric labeling-based quantitative proteomics, we simultaneously identified and quantified 45% Synechocystis proteome across four different trophic modes, i.e., autotrophic, heterotrophic, photoheterotrophic, and mixotrophic modes. Among the 155 proteins that are differentially expressed across four trophic modes, proteins involved in nitrogen assimilation and light-independent chlorophyll synthesis are dramatically upregulated in the mixotrophic mode, concomitant with a dramatic increase of P II phosphorylation that senses carbon and nitrogen assimilation status. Moreover, functional study using a mutant defective in light-independent chlorophyll synthesis revealed that this pathway is important for chlorophyll accumulation under a cycled light/dark illumination regime, a condition mimicking day/night cycles in certain natural habitats. Collectively, these results provide the most comprehensive information on trophic mode-dependent protein expression in cyanobacterium, and reveal the functional significance of light-independent chlorophyll synthesis in trophic growth. Copyright © 2017 The Author. Published by Elsevier Inc. All rights reserved.

Eco-Evolutionary Trophic Dynamics: Loss of Top Predators Drives Trophic Evolution and Ecology of Prey

PubMed Central

Palkovacs, Eric P.; Wasserman, Ben A.; Kinnison, Michael T.

2011-01-01

Ecosystems are being altered on a global scale by the extirpation of top predators. The ecological effects of predator removal have been investigated widely; however, predator removal can also change natural selection acting on prey, resulting in contemporary evolution. Here we tested the role of predator removal on the contemporary evolution of trophic traits in prey. We utilized a historical introduction experiment where Trinidadian guppies (Poecilia reticulata) were relocated from a site with predatory fishes to a site lacking predators. To assess the trophic consequences of predator release, we linked individual morphology (cranial, jaw, and body) to foraging performance. Our results show that predator release caused an increase in guppy density and a “sharpening” of guppy trophic traits, which enhanced food consumption rates. Predator release appears to have shifted natural selection away from predator escape ability and towards resource acquisition ability. Related diet and mesocosm studies suggest that this shift enhances the impact of guppies on lower trophic levels in a fashion nuanced by the omnivorous feeding ecology of the species. We conclude that extirpation of top predators may commonly select for enhanced feeding performance in prey, with important cascading consequences for communities and ecosystems. PMID:21526156

Trophic flow structure of the Danajon ecosystem (Central Philippines) and impacts of illegal and destructive fishing practices

NASA Astrophysics Data System (ADS)

Bacalso, Regina Therese M.; Wolff, Matthias

2014-11-01

A trophic model of the shallow Danajon Bank, in the Central Visayas, Philippines was developed using a mass-balance approach (Ecopath) to describe the system characteristics and fisheries interactions. The Ecopath model is composed of 37 functional groups and 17 fishing fleet types reflecting the high diversity of catches and fishing operations in the Danajon Bank. Collectively, the catch is dominated by lower trophic level fish and invertebrates as reflected in the mean trophic level of the fishery (2.95). The low biomass and high exploitation levels for many upper trophic level groups and the little evidence for strong natural physical disturbances suggest that top-down fishery is the main driver of system dynamics. The mixed trophic impacts (MTI) analysis reveals the role of the illegal and destructive fishing operations in influencing the ecosystem structure and dynamics. Furthermore, the illegal fisheries' estimated collective annual harvest is equivalent to nearly a quarter of the entire municipal fisheries catch in the area. Improved fisheries law enforcement by the local government units to curb these illegal and destructive fishing operations could substantially increase the potential gains of the legal fisheries.

Community trait overdispersion due to trophic interactions: concerns for assembly process inference

PubMed Central

Petchey, Owen L.

2016-01-01

The expected link between competitive exclusion and community trait overdispersion has been used to infer competition in local communities, and trait clustering has been interpreted as habitat filtering. Such community assembly process inference has received criticism for ignoring trophic interactions, as competition and trophic interactions might create similar trait patterns. While other theoretical studies have generally demonstrated the importance of predation for coexistence, ours provides the first quantitative demonstration of such effects on assembly process inference, using a trait-based ecological model to simulate the assembly of a competitive primary consumer community with and without the influence of trophic interactions. We quantified and contrasted trait dispersion/clustering of the competitive communities with the absence and presence of secondary consumers. Trophic interactions most often decreased trait clustering (i.e. increased dispersion) in the competitive communities due to evenly distributed invasions of secondary consumers and subsequent competitor extinctions over trait space. Furthermore, effects of trophic interactions were somewhat dependent on model parameters and clustering metric. These effects create considerable problems for process inference from trait distributions; one potential solution is to use more process-based and inclusive models in inference. PMID:27733548

Using stable isotope analysis to assess trophic relationships between Atlantic bluefin tuna (Thunnus thynnus) and striped dolphin (Stenella coeruleoalba) in the Strait of Gibraltar.

PubMed

Varela, José L; Rojo-Nieto, Elisa; Sorell, Joan M; Medina, Antonio

2018-08-01

Stable isotope analysis (δ 13 C and δ 15 N from liver and muscle) was used to assess trophic relationships between Atlantic bluefin tuna (ABFT) (Thunnus thynnus) and striped dolphin (SC) (Stenella coeruleoalba) in the Strait of Gibraltar (SoG). δ 15 N values from ABFT muscle and liver tissues were significantly different from those of dolphin samples, but no for δ 13 C values. Diet estimation by MixSIAR models from muscle and liver revealed that ABFT fed mainly on squids (Todaropsis eblanae and Illex coindetii). The shrimp Pasiphaea sp. was estimated to be the most important prey-species in the diet of SC. Trophic positions estimated from muscle and liver isotopic data suggested that ABFT occupy a higher trophic level than SC. Estimations of isotopic niche, as measured by the standard ellipse area, indicated that ABFT show a broader trophic niche than SC; furthermore, SEAc did not show trophic overlap between both predators. The results of this study suggest that resource partitioning occurs between ABFT and SC in the SoG ecosystem. Copyright © 2018 Elsevier Ltd. All rights reserved.

Trophic interactions between native and introduced fish species in a littoral fish community.

PubMed

Monroy, M; Maceda-Veiga, A; Caiola, N; De Sostoa, A

2014-11-01

The trophic interactions between 15 native and two introduced fish species, silverside Odontesthes bonariensis and rainbow trout Oncorhynchus mykiss, collected in a major fishery area at Lake Titicaca were explored by integrating traditional ecological knowledge and stable-isotope analyses (SIA). SIA suggested the existence of six trophic groups in this fish community based on δ(13)C and δ(15)N signatures. This was supported by ecological evidence illustrating marked spatial segregation between groups, but a similar trophic level for most of the native groups. Based on Bayesian ellipse analyses, niche overlap appeared to occur between small O. bonariensis (<90 mm) and benthopelagic native species (31.6%), and between the native pelagic killifish Orestias ispi and large O. bonariensis (39%) or O. mykiss (19.7%). In addition, Bayesian mixing models suggested that O. ispi and epipelagic species are likely to be the main prey items for the two introduced fish species. This study reveals a trophic link between native and introduced fish species, and demonstrates the utility of combining both SIA and traditional ecological knowledge to understand trophic relationships between fish species with similar feeding habits. © 2014 The Fisheries Society of the British Isles.

Marine Mammal Impacts in Exploited Ecosystems: Would Large Scale Culling Benefit Fisheries?

PubMed Central

Morissette, Lyne; Christensen, Villy; Pauly, Daniel

2012-01-01

Competition between marine mammals and fisheries for marine resources—whether real or perceived—has become a major issue for several countries and in international fora. We examined trophic interactions between marine mammals and fisheries based on a resource overlap index, using seven Ecopath models including marine mammal groups. On a global scale, most food consumed by marine mammals consisted of prey types that were not the main target of fisheries. For each ecosystem, the primary production required (PPR) to sustain marine mammals was less than half the PPR to sustain fisheries catches. We also developed an index representing the mean trophic level of marine mammal's consumption (TLQ) and compared it with the mean trophic level of fisheries' catches (TLC). Our results showed that overall TLQ was lower than TLC (2.88 versus 3.42). As fisheries increasingly exploit lower-trophic level species, the competition with marine mammals may become more important. We used mixed trophic impact analysis to evaluate indirect trophic effects of marine mammals, and in some cases found beneficial effects on some prey. Finally, we assessed the change in the trophic structure of an ecosystem after a simulated extirpation of marine mammal populations. We found that this lead to alterations in the structure of the ecosystems, and that there was no clear and direct relationship between marine mammals' predation and the potential catch by fisheries. Indeed, total biomass, with no marine mammals in the ecosystem, generally remained surprisingly similar, or even decreased for some species. PMID:22970153

Trophic transfer of trace metals from the polychaete worm Nereis diversicolor to the polychaete N. virens and the decapod crustacean Palaemonetes varians

USGS Publications Warehouse

Rainbow, P.S.; Poirier, L.; Smith, B.D.; Brix, K.V.; Luoma, S.N.

2006-01-01

Diet is an important exposure route for the uptake of trace metals by aquatic invertebrates, with trace metal trophic transfer depending on 2 stages - assimilation and subsequent accumulation by the predator. This study investigated the trophic transfer of trace metals from the sediment-dwelling polychaete worm Nereis diversicolor from metal-rich estuarine sediments in southwestern UK to 2 predators - another polychaete N. virens (Cu, Zn, Pb, Cd, Fe) and the decapod crustacean Palaemonetes varians (Cu, Zn, Pb, Cd, Fe, Ag, As, Mn). N. virens showed net accumulation of Cu, Zn, Pb and Cd from the prey; accumulation increased with increasing prey concentration, but a coefficient of trophic transfer decreased with increasing prey concentration, probably because a higher proportion of accumulated metal in the prey is bound in less trophically available (insoluble) detoxified forms. The trace metal accumulation patterns of P. varians apparently restricted significant net accumulation of metals from the diet of N. diversicolor to just Cd. There was significant mortality of the decapods fed on the diets of metal-rich worms. Metal-rich invertebrates that have accumulated metals from the rich historical store in the sediments of particular SW England estuaries can potentially pass these metals along food chains, with accumulation and total food chain transfer depending on the metal assimilation efficiencies and accumulation patterns of the animal at each trophic level. This trophic transfer may be significant enough to have ecotoxicological effects. ?? Inter-Research 2006.

Complex trophic interactions of calanoid copepods in the Benguela upwelling system

NASA Astrophysics Data System (ADS)

Schukat, Anna; Auel, Holger; Teuber, Lena; Lahajnar, Niko; Hagen, Wilhelm

2014-01-01

Life-cycle adaptations, dietary preferences and trophic levels of calanoid copepods from the northern Benguela Current off Namibia were determined via lipid classes, marker fatty acids and stable isotope analyses, respectively. Trophic levels of copepod species were compared to other zooplankton and top consumers. Lipid class analyses revealed that three of the dominant calanoid copepod species stored wax esters, four accumulated triacylglycerols and another three species were characterised by high phospholipid levels. The two biomarker approaches (via fatty acids and stable isotopes) revealed a complex pattern of trophic positions for the various copepod species, but also highlighted the dietary importance of diatoms and dinoflagellates. Calanoides carinatus and Nannocalanus minor occupied the lowest trophic level (predominantly herbivorous) corresponding to high amounts of fatty acid markers for diatoms (e.g. 16:1(n - 7)) and dinoflagellates (e.g. 18:4(n - 3)). These two copepod species represent the classical link between primary production and higher trophic levels. All other copepods belonged to secondary or even tertiary (some deep-sea copepods) consumers. The calanoid copepod species cover the entire range of δ15N ratios, as compared to δ15N ratios of all non-calanoid taxa investigated, from salps to adult fish. These data emphasise that the trophic roles of calanoid copepods are far more complex than just interlinking primary producers with pelagic fish, which should also be considered in the process of developing realistic food-web models of coastal upwelling systems.

Marine mammal impacts in exploited ecosystems: would large scale culling benefit fisheries?

PubMed

Morissette, Lyne; Christensen, Villy; Pauly, Daniel

2012-01-01

Competition between marine mammals and fisheries for marine resources-whether real or perceived-has become a major issue for several countries and in international fora. We examined trophic interactions between marine mammals and fisheries based on a resource overlap index, using seven Ecopath models including marine mammal groups. On a global scale, most food consumed by marine mammals consisted of prey types that were not the main target of fisheries. For each ecosystem, the primary production required (PPR) to sustain marine mammals was less than half the PPR to sustain fisheries catches. We also developed an index representing the mean trophic level of marine mammal's consumption (TL(Q)) and compared it with the mean trophic level of fisheries' catches (TL(C)). Our results showed that overall TL(Q) was lower than TL(C) (2.88 versus 3.42). As fisheries increasingly exploit lower-trophic level species, the competition with marine mammals may become more important. We used mixed trophic impact analysis to evaluate indirect trophic effects of marine mammals, and in some cases found beneficial effects on some prey. Finally, we assessed the change in the trophic structure of an ecosystem after a simulated extirpation of marine mammal populations. We found that this lead to alterations in the structure of the ecosystems, and that there was no clear and direct relationship between marine mammals' predation and the potential catch by fisheries. Indeed, total biomass, with no marine mammals in the ecosystem, generally remained surprisingly similar, or even decreased for some species.

Regulated release of serotonin from axonal growth cones isolated from the fetal rat brain.

PubMed

Mercado, R; Floran, B; Hernandez, J

1998-01-01

In the present work we propose an hypothetical model related to a molecular recognizing system for serotonin in isolated growth cone particles. This model is supported by previous results from our laboratory plus new ones which show that growth cones release serotonin tonically and such release can be stimulated by potassium in a calcium-dependent manner. The present results, together with other author's data, suggest a physiological basis for the putative role of serotonin as a trophic factor during nervous system development.

Landsat analysis of lake quality

NASA Technical Reports Server (NTRS)

Scarpace, F. L.; Fisher, L. T.; Holmquist, K. W.

1979-01-01

The trophic status of a number of inland lakes in Wisconsin has been assessed. The feasibility of using both photographic and digital representations of Landsat imagery was investigated during the lake classification project. The result of the investigation has been a semi-automatic data acquisition and handling system which, in conjunction with an analytical categorization scheme, can be used to classify all the significant lakes in the state.

Soil fauna responses to natural disturbances, invasive species, and global climate change: Current state of the science and a call to action

Treesearch

David R. Coyle; Uma J. Nagendra; Melanie K. Taylor; J. Holly Campbell; Chelsea E. Cunard; Aaron H. Joslin; Abha Mundepi; Carly A. Phillips; Mac A. Callaham

2017-01-01

Environmental disturbances seem to be increasing in frequency and impact, yet we have little understanding of the belowground impacts of these events. Soil fauna, while widely acknowledged to be important drivers of biogeochemical function, soil structure and sustainability, and trophic interactions, are understudied compared to other belowground organisms such as...

[Applications of stable isotope analysis in the trophic ecology studies of cephalopods].

PubMed

Li, Yun-Kai; Gong, Yi; Chen, Xin-Jun

2014-05-01

Cephalopods play an important role in marine food webs, however, knowledge about their complex life history, especially their feeding ecology, remains limited. With the rapidly increasing use of stable isotope analysis (SIA) in ecology, it becomes a powerful tool and complement of traditional methods for investigating the trophic ecology and migration patterns of invertebrates. Here, after summarizing the current methods for trophic ecology investigation of cephalopods, applications of SIA in studying the trophic ecology of cephalopods were reviewed, including the key issues such as standardization of available tissues for SIA analyzing, diet shift and migration patterns of cephalopods, with the aim of advancing its application in the biology of cephalopods in the future.

Long-chain omega-3 from low-trophic-level fish provides value to farmed seafood

PubMed Central

Bibus, Douglas M

2015-01-01

Low-trophic-level fish are a crucial source of long-chain (LC) omega-3 fatty acids for farmed fish and humans. Many farm-raised fish species have a clear need for these nutrients. Farmed fish deposit the LC omega-3s in their flesh and transfer them up the food chain. However, the content of LC omega-3s in farm-raised seafood continues to decline, while the content of shorter-chain plant-sourced omega-3s, and pro-inflammtory omega-6s continue to increase. This reduces its nutritional worth. The value of low-trophic-level fish is often viewed merely as its price at the dock. Some reports and metrics steer public attention towards the mass balance between quantities of low-trophic-level fish and farmed seafood. However, the the nutritional value of seafood is more important than its mere quantities. The role of low-trophic-level fish in human nutrition, health, and wellbeing is a fundamental component of its economic value to society. PMID:26097289

Biodiversity loss in benthic macroinfaunal communities and its consequence for organic mercury trophic availability to benthivorous predators in the lower Hudson River estuary, USA.

PubMed

Goto, Daisuke; Wallace, William G

2009-12-01

Organic mercury such as methylmercury is not only one of the most toxic substances found in coastal ecosystems but also has high trophic transfer efficiency. In this study, we examined implications of chronically altered benthic macroinfaunal assemblages for organic mercury trophic availability (based on organic mercury intracellular partitioning) to their predators in the Arthur Kill-AK (New York, USA). Despite low species diversity, both density and biomass of benthic macroinvertebrates in AK were significantly higher than those at the reference site. Disproportionately high biomass of benthic macroinvertebrates (mostly polychaetes) in the northern AK resulted in a more than twofold increase ('ecological enrichment') in the trophically available organic mercury pool. These results suggest that altered benthic macroinfaunal community structure in AK may play an important role in organic mercury trophic availability at the base of benthic food webs and potentially in mercury biogeochemical cycling in this severely urbanized coastal ecosystem.

Long-chain omega-3 from low-trophic-level fish provides value to farmed seafood.

PubMed

Bibus, Douglas M

2015-03-01

Low-trophic-level fish are a crucial source of long-chain (LC) omega-3 fatty acids for farmed fish and humans. Many farm-raised fish species have a clear need for these nutrients. Farmed fish deposit the LC omega-3s in their flesh and transfer them up the food chain. However, the content of LC omega-3s in farm-raised seafood continues to decline, while the content of shorter-chain plant-sourced omega-3s, and pro-inflammtory omega-6s continue to increase. This reduces its nutritional worth. The value of low-trophic-level fish is often viewed merely as its price at the dock. Some reports and metrics steer public attention towards the mass balance between quantities of low-trophic-level fish and farmed seafood. However, the the nutritional value of seafood is more important than its mere quantities. The role of low-trophic-level fish in human nutrition, health, and wellbeing is a fundamental component of its economic value to society.

The Influence of Mean Trophic Level on Biomass and Production in Marine Ecosystems

NASA Astrophysics Data System (ADS)

Woodson, C. B.; Schramski, J.

2016-02-01

The oceans have faced rapid removal of top predators causing a reduction in the mean trophic level of many marine ecosystems due to fishing down the food web. However, estimating the pre-exploitation biomass of the ocean has been difficult. Historical population sizes have been estimated using population dynamics models, archaeological or historical records, fisheries data, living memory, ecological monitoring data, genetics, and metabolic theory. In this talk, we expand on the use of metabolic theory by including complex trophic webs to estimate pre-exploitation levels of marine biomass. Our results suggest that historical marine biomass could be as much as 10 times higher than current estimates and that the total carrying capacity of the ocean is sensitive to mean trophic level and trophic web complexity. We further show that the production levels needed to support the added biomass are possible due to biomass accumulation and predator-prey overlap in regions such as fronts. These results have important implications for marine biogeochemical cycling, fisheries management, and conservation efforts.

Environmental drivers of heterogeneity in the trophic-functional structure of protozoan communities during an annual cycle in a coastal ecosystem.

PubMed

Xu, Guangjian; Yang, Eun Jin; Xu, Henglong

2017-08-15

Trophic-functional groupings are an important biological trait to summarize community structure in functional space. The heterogeneity of the tropic-functional pattern of protozoan communities and its environmental drivers were studied in coastal waters of the Yellow Sea during a 1-year cycle. Samples were collected using the glass slide method at four stations within a water pollution gradient. A second-stage matrix-based analysis was used to summarize spatial variation in the annual pattern of the functional structure. A clustering analysis revealed significant variability in the trophic-functional pattern among the four stations during the 1-year cycle. The heterogeneity in the trophic-functional pattern of the communities was significantly related to changes in environmental variables, particularly ammonium-nitrogen and nitrates, alone or in combination with dissolved oxygen. These results suggest that the heterogeneity in annual patterns of protozoan trophic-functional structure may reflect water quality status in coastal ecosystems. Copyright © 2017. Published by Elsevier Ltd.

Trophic structure of the Barents Sea fish assemblage with special reference to the cod stock recoverability

NASA Astrophysics Data System (ADS)

Dolgov, Andrey V.

2009-04-01

The species composition and trophic structure of the Barents Sea fish assemblage is analysed based on data from research survey trawls and diet analyses of various species. Atlantic cod was the dominant fish species encountered, accounting for more than 55% by abundance or biomass. Only five fish species (long rough dab, thorny skate, Greenland halibut, deepwater redfish and saithe) were sufficiently abundant to be considered as possible food competitors with cod in the Barents Sea. However, possible trophic competition is not high, due to low spatial and temporal overlap between cod and these other species. Analyses of fish assemblages and trophic structures of the Barents Sea and other areas (North Sea, Western Greenland, Newfoundland-Labrador shelf) suggest that Barents Sea cod is the only cod stock for which the ability to recover may not be restricted by trophic relations among fishes, due to a lack of other abundant predatory species and low potential for competition caused by spatial-temporal changes.

Relating trophic resources to community structure: a predictive index of food availability

PubMed Central

Edgar, Graham J.

2017-01-01

The abundance and the distribution of trophic resources available for consumers influence the productivity and the diversity of natural communities. Nevertheless, assessment of the actual abundance of food items available for individual trophic groups has been constrained by differences in methods and metrics used by various authors. Here we develop an index of food abundance, the framework of which can be adapted for different ecosystems. The relative available food index (RAFI) is computed by considering standard resource conditions of a habitat and the influence of various generalized anthropogenic and natural factors. RAFI was developed using published literature on food abundance and validated by comparison of predictions versus observed trophic resources across various marine sites. RAFI tables here proposed can be applied to a range of marine ecosystems for predictions of the potential abundance of food available for each trophic group, hence permitting exploration of ecological theories by focusing on the deviation from the observed to the expected. PMID:28386417

Chemical contaminants (trace metals, persistent organic pollutants) in albacore tuna from western Indian and south-eastern Atlantic Oceans: Trophic influence and potential as tracers of populations.

PubMed

Chouvelon, Tiphaine; Brach-Papa, Christophe; Auger, Dominique; Bodin, Nathalie; Bruzac, Sandrine; Crochet, Sylvette; Degroote, Maxime; Hollanda, Stephanie J; Hubert, Clarisse; Knoery, Joël; Munschy, Catherine; Puech, Alexis; Rozuel, Emmanuelle; Thomas, Bastien; West, Wendy; Bourjea, Jérôme; Nikolic, Natacha

2017-10-15

Albacore tuna (Thunnus alalunga) is a highly commercial fish species harvested in the world's Oceans. Identifying the potential links between populations is one of the key tools that can improve the current management across fisheries areas. In addition to characterising populations' contamination state, chemical compounds can help refine foraging areas, individual flows and populations' structure, especially when combined with other intrinsic biogeochemical (trophic) markers such as carbon and nitrogen stable isotopes. This study investigated the bioaccumulation of seven selected trace metals - chromium, nickel, copper (Cu), zinc (Zn), cadmium (Cd), mercury (Hg) and lead - in the muscle of 443 albacore tunas, collected over two seasons and/or years in the western Indian Ocean (WIO: Reunion Island and Seychelles) and in the south-eastern Atlantic Ocean (SEAO: South Africa). The main factor that explained metal concentration variability was the geographic origin of fish, rather than the size and the sex of individuals, or the season/year of sampling. The elements Cu, Zn, Cd and Hg indicated a segregation of the geographic groups most clearly. For similar sized-individuals, tunas from SEAO had significantly higher concentrations in Cu, Zn and Cd, but lower Hg concentrations than those from WIO. Information inferred from the analysis of trophic markers (δ 13 C, δ 15 N) and selected persistent organic pollutants, as well as information on stomach contents, corroborated the geographical differences obtained by trace metals. It also highlighted the influence of trophic ecology on metal bioaccumulation. Finally, this study evidenced the potential of metals and chemical contaminants in general as tracers, by segregating groups of individuals using different food webs or habitats, to better understand spatial connectivity at the population scale. Limited flows of individuals between the SEAO and the WIO are suggested. Albacore as predatory fish also provided some information on environmental and food web chemical contamination in the different study areas. Copyright © 2017 Elsevier B.V. All rights reserved.

Changes in trophic flow structure of Independence Bay (Peru) over an ENSO cycle

NASA Astrophysics Data System (ADS)

Taylor, Marc H.; Wolff, Matthias; Mendo, Jaime; Yamashiro, Carmen

2008-10-01

During the strong warm El Niño (EN) that occurred in 1997/98, Independence Bay (14°S, Peru) showed a ca. 10 °C increase in surface temperatures, higher oxygen concentrations, and clearer water due to decreased phytoplankton concentrations. Under these quasi-tropical conditions, many benthic species suffered (e.g. macroalgae, portunid crabs, and polychaetes) while others benefited (e.g. scallop, sea stars, and sea urchins). The most obvious change was the strong recruitment success and subsequent proliferation of the scallop Argopecten purpuratus, whose biomass increased fiftyfold. To understand these changes, steady-state models of the bay ecosystem trophic structure were constructed and compared for a normal upwelling year (1996) and during an EN (1998), and longer-term dynamics (1996-2003) were explored based on time series of catch and biomass using Ecopath with Ecosim (EwE) software. Model inputs were based on surveys and landings data collected by the Instituto del Mar del Perú (IMARPE). Results indicate that while ecosystem size (total throughput) is reduced by 18% during EN, mainly as a result of decreased total primary production, benthic biomass remains largely unchanged despite considerable shifts in the dominant benthic taxa (e.g. scallops replace polychaetes as secondary consumers). Under normal upwelling conditions, predation by snails and crabs utilize the production of their prey almost completely, resulting in more efficient energy flow to higher trophic levels than occurs during EN. However during EN, the proliferation of the scallop A. purpuratus combined with decreased phytoplankton increased the proportion of directly utilized primary production, while exports and flows to detritus are reduced. The simulations suggest that the main cause for the scallop outburst and for the reduction in crab and macroalgae biomass was a direct temperature effect, whereas other changes are partially explained by trophic interactions. The simulations suggest that bottom-up effects largely control the system.

An ecosystem model of an exploited southern Mediterranean shelf region (Gulf of Gabes, Tunisia) and a comparison with other Mediterranean ecosystem model properties

NASA Astrophysics Data System (ADS)

Hattab, Tarek; Ben Rais Lasram, Frida; Albouy, Camille; Romdhane, Mohamed Salah; Jarboui, Othman; Halouani, Ghassen; Cury, Philippe; Le Loc'h, François

2013-12-01

In this paper, we describe an exploited continental shelf ecosystem (Gulf of Gabes) in the southern Mediterranean Sea using an Ecopath mass-balance model. This allowed us to determine the structure and functioning of this ecosystem and assess the impacts of fishing upon it. The model represents the average state of the ecosystem between 2000 and 2005. It includes 41 functional groups, which encompass the entire trophic spectrum from phytoplankton to higher trophic levels (e.g., fishes, birds, and mammals), and also considers the fishing activities in the area (five fleets). Model results highlight an important bentho-pelagic coupling in the system due to the links between plankton and benthic invertebrates through detritus. A comparison of this model with those developed for other continental shelf regions in the Mediterranean (i.e., the southern Catalan, the northern-central Adriatic, and the northern Aegean Seas) emphasizes similar patterns in their trophic functioning. Low and medium trophic levels (i.e., zooplankton, benthic molluscs, and polychaetes) and sharks were identified as playing key ecosystem roles and were classified as keystone groups. An analysis of ecosystem attributes indicated that the Gulf of Gabes is the least mature (i.e., in the earliest stages of ecosystem development) of the four ecosystems that were compared and it is suggested that this is due, at least in part, to the impacts of fishing. Bottom trawling was identified as having the widest-ranging impacts across the different functional groups and the largest impacts on some commercially-targeted demersal fish species. Several exploitation indices highlighted that the Gulf of Gabes ecosystem is highly exploited, a finding which is supported by stock assessment outcomes. This suggests that it is unlikely that the gulf can be fished at sustainable levels, a situation which is similar to other marine ecosystems in the Mediterranean Sea.

Investigating trophic relationships of pinnipeds in Alaska and Washington using stable isotope ratios of nitrogen and carbon

USGS Publications Warehouse

Hobson, Keith A.; Sease, John L.; Merrick, Richard L.; Piatt, John F.

1997-01-01

We measured stable-nitrogen (δ15N) and stable-carbon (δ13C) isotope ratios in muscle and hair from 7 northern fur seals (Callorhinus ursinus) from the Pribilof Islands, Alaska, and 27 Steller sea lions (Eumetopias jubatus), and 14 harbor seals (Phoca vitulina) from the Gulf of Alaska and coast of Washington State, in order to contrast dietary information derived from isotopic vs. available conventional dietary studies. Stable-nitrogen-isotope analysis of muscle revealed that harbor seals were enriched over sea lions (mean δ15N = 18.6‰vs. 17.5‰) which were in turn enriched over northern fur seals (mean δ15N = 16.6‰). Trophic segregation among these species likely results primarily from differential reliance on herring (Clupea harengus), Atka mackerel (Pleurogrammus monopterygius), and large vs. small walleye pollock (Theregra chalcogramma). According to their δ15N values, adult male Steller sea lions showed a higher trophic position than adult females (mean δ15N: 18.0‰ vs. 17.2‰), whereas adult female northern fur seals were trophically higher than juvenile male fur seals (mean δ15N: 16.5‰vs. 15.0‰). Each of these observed differences likely resulted from differential reliance on squid or differences in the size range of pollock consumed. Three northern fur seal pups showed higher δ15N enrichment over adults (mean 17.7‰vs. 15.8‰) due to their reliance on their mother's milk. Stable-carbon isotope measurements of hair revealed a cline toward more negative values with latitude. Segregation in hair δ13C between Steller sea lions and harbor seals off the coast of Washington (mean δ13C: -13.6‰ vs. -15.0‰) reflected the greater association of harbor seals with freshwater input from the Columbia River. Our study demonstrates the utility of the stable isotope approach to augment conventional dietary analyses of pinnipeds and other marine mammals.

Mercury bioaccumulation in fish in a region affected by historic gold mining; the South Yuba River, Deer Creek, and Bear River watersheds, California, 1999

USGS Publications Warehouse

May, Jason T.; Hothem, Roger L.; Alpers, Charles N.; Law, Matthew A.

2000-01-01

Mercury that was used historically for gold recovery in mining areas of the Sierra Nevada continues to enter local and downstream water bodies, including the Sacramento Delta and the San Francisco Bay of northern California. Methylmercury is of particular concern because it is the most prevalent form of mercury in fish and is a potent neurotoxin that bioaccumulates at successive trophic levels within food webs. In April 1999, the U.S. Geological Survey, in cooperation with several other agencies the Forest Service (U.S. Department of Agriculture), the Bureau of Land Management, the U.S. Environmental Protection Agency, the California State Water Resources Control Board, and the Nevada County Resource Conservation District began a pilot investigation to characterize the occurrence and distribution of mercury in water, sediment, and biota in the South Yuba River, Deer Creek, and Bear River watersheds of California. Biological samples consisted of semi-aquatic and aquatic insects, amphibians, bird eggs, and fish. Fish were collected from 5 reservoirs and 14 stream sites during August through October 1999 to assess the distribution of mercury in these watersheds. Fish that were collected from reservoirs included top trophic level predators (black basses, Micropterus spp.) intermediate trophic level predators [sunfish (blue gill, Lepomis macrochirus; green sunfish, Lepomis cyanellus; and black crappie, Poxomis nigromaculatus)] and benthic omnivores (channel catfish, Ictularus punctatus). At stream sites, the species collected were upper trophic level salmonids (brown trout, Salmo trutta) and upper-to-intermediate trophic level salmonids (rainbow trout, Oncorhynchus mykiss). Boneless and skinless fillet portions from 161 fish were analyzed for total mercury; 131 samples were individual fish, and the remaining 30 fish were combined into 10 composite samples of three fish each of the same species and size class. Mercury concentrations in samples of black basses (Micropterus spp.), including largemouth, smallmouth, and spotted bass, ranged from 0.20 to 1.5 parts per million (ppm), wet basis. Mercury concentrations in sunfish ranged from less than 0.10 to 0.41 ppm (wet). Channel catfish had mercury concentrations from 0.16 to 0.75 ppm (wet). The range of mercury concentrations observed in rainbow trout was from 0.06 to 0.38 ppm (wet), and in brown trout was from 0.02 to 0.43 ppm (wet). Mercury concentrations in trout were greater than 0.3 ppm in samples from three of 14 stream sites. Mercury at elevated concentrations may pose a health risk to piscivorous wildlife and to humans who eat fish on a regular basis. Data presented in this report may be useful to local, state, and federal agencies responsible for assessing the potential risks associated with elevated levels of mercury in fish in the South Yuba River, Deer Creek, and Bear River watersheds.

Predicting Trophic Interactions and Habitat Utilization in the California Current Ecosystem

DTIC Science & Technology

2014-09-30

on trophic interactions affecting habitat utilization and foraging patterns of California sea lions (CSL) in the California Current Large Marine...middle (sardine and anchovy) and higher (sea lions ) trophic level species. To this end, our numerical experiments are designed to isolate patterns of...NEMURO) embedded in a regional ocean circulation model (ROMS), and both coupled with a multi- species individual-based model (IBM) for forage fish

Common carp disrupt ecosystem structure and function through middle-out effects

USGS Publications Warehouse

Kaemingk, Mark A.; Jolley, Jeffrey C.; Paukert, Craig P.; Willis, David W.; Henderson, Kjetil R.; Holland, Richard S.; Wanner, Greg A.; Lindvall, Mark L.

2016-01-01

Middle-out effects or a combination of top-down and bottom-up processes create many theoretical and empirical challenges in the realm of trophic ecology. We propose using specific autecology or species trait (i.e. behavioural) information to help explain and understand trophic dynamics that may involve complicated and non-unidirectional trophic interactions. The common carp (Cyprinus carpio) served as our model species for whole-lake observational and experimental studies; four trophic levels were measured to assess common carp-mediated middle-out effects across multiple lakes. We hypothesised that common carp could influence aquatic ecosystems through multiple pathways (i.e. abiotic and biotic foraging, early life feeding, nutrient). Both studies revealed most trophic levels were affected by common carp, highlighting strong middle-out effects likely caused by common carp foraging activities and abiotic influence (i.e. sediment resuspension). The loss of water transparency, submersed vegetation and a shift in zooplankton dynamics were the strongest effects. Trophic levels furthest from direct pathway effects were also affected (fish life history traits). The present study demonstrates that common carp can exert substantial effects on ecosystem structure and function. Species capable of middle-out effects can greatly modify communities through a variety of available pathways and are not confined to traditional top-down or bottom-up processes.

Developing Terrestrial Trophic Models for Petroleum and Natural Gas Exploration and Production Sites: The Oklahoma Tallgrass Prairie Preserve Example

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stevenson, M; Coty, J; Stewart, J

This document details procedures to be used when constructing a conceptual terrestrial trophic model for natural gas and oil exploration and production sites. A site conceptual trophic model is intended for use in evaluating ecological impacts of oil and brine releases at E&P sites from a landscape or ecosystem perspective. The terrestrial trophic model protocol was developed using an example site, the Tallgrass Prairie Preserve (TPP) in Oklahoma. The procedure focuses on developing a terrestrial trophic model using information found in the primary literature, and augmented using site-specific research where available. Although the TPP has been the subject of considerablemore » research and public interest since the high-profile reintroduction of bison (Bison bison) in 1993, little formal work has been done to develop a food web for the plant and animal communities found at the preserve. We describe how to divide species into guilds using explicit criteria on the basis of resource use and spatial distribution. For the TPP, sixteen guilds were developed for use in the trophic model, and the relationships among these guilds were analyzed. A brief discussion of the results of this model is provided, along with considerations for its use and areas for further study.« less

Trophic interaction modifications: an empirical and theoretical framework.

PubMed

Terry, J Christopher D; Morris, Rebecca J; Bonsall, Michael B

2017-10-01

Consumer-resource interactions are often influenced by other species in the community. At present these 'trophic interaction modifications' are rarely included in ecological models despite demonstrations that they can drive system dynamics. Here, we advocate and extend an approach that has the potential to unite and represent this key group of non-trophic interactions by emphasising the change to trophic interactions induced by modifying species. We highlight the opportunities this approach brings in comparison to frameworks that coerce trophic interaction modifications into pairwise relationships. To establish common frames of reference and explore the value of the approach, we set out a range of metrics for the 'strength' of an interaction modification which incorporate increasing levels of contextual information about the system. Through demonstrations in three-species model systems, we establish that these metrics capture complimentary aspects of interaction modifications. We show how the approach can be used in a range of empirical contexts; we identify as specific gaps in current understanding experiments with multiple levels of modifier species and the distributions of modifications in networks. The trophic interaction modification approach we propose can motivate and unite empirical and theoretical studies of system dynamics, providing a route to confront ecological complexity. © 2017 The Authors. Ecology Letters published by CNRS and John Wiley & Sons Ltd.

The gut microbiome and degradation enzyme activity of wild freshwater fishes influenced by their trophic levels.

PubMed

Liu, Han; Guo, Xianwu; Gooneratne, Ravi; Lai, Ruifang; Zeng, Cong; Zhan, Fanbin; Wang, Weimin

2016-04-13

Vertebrate gut microbiome often underpins the metabolic capability and provides many beneficial effects on their hosts. However, little was known about how host trophic level influences fish gut microbiota and metabolic activity. In this study, more than 985,000 quality-filtered sequences from 24 16S rRNA libraries were obtained and the results revealed distinct compositions and diversities of gut microbiota in four trophic categories. PCoA test showed that gut bacterial communities of carnivorous and herbivorous fishes formed distinctly different clusters in PCoA space. Although fish in different trophic levels shared a large size of OTUs comprising a core microbiota community, at the genus level a strong distinction existed. Cellulose-degrading bacteria Clostridium, Citrobacter and Leptotrichia were dominant in the herbivorous, while Cetobacterium and protease-producing bacteria Halomonas were dominant in the carnivorous. PICRUSt predictions of metagenome function revealed that fishes in different trophic levels affected the metabolic capacity of their gut microbiota. Moreover, cellulase and amylase activities in herbivorous fishes were significantly higher than in the carnivorous, while trypsin activity in the carnivorous was much higher than in the herbivorous. These results indicated that host trophic level influenced the structure and composition of gut microbiota, metabolic capacity and gut content enzyme activity.

Trophic specialization influences the rate of environmental niche evolution in damselfishes (Pomacentridae).

PubMed

Litsios, Glenn; Pellissier, Loïc; Forest, Félix; Lexer, Christian; Pearman, Peter B; Zimmermann, Niklaus E; Salamin, Nicolas

2012-09-22

The rate of environmental niche evolution describes the capability of species to explore the available environmental space and is known to vary among species owing to lineage-specific factors. Trophic specialization is a main force driving species evolution and is responsible for classical examples of adaptive radiations in fishes. We investigate the effect of trophic specialization on the rate of environmental niche evolution in the damselfish, Pomacentridae, which is an important family of tropical reef fishes. First, phylogenetic niche conservatism is not detected in the family using a standard test of phylogenetic signal, and we demonstrate that the environmental niches of damselfishes that differ in trophic specialization are not equivalent while they still overlap at their mean values. Second, we estimate the relative rates of niche evolution on the phylogenetic tree and show the heterogeneity among rates of environmental niche evolution of the three trophic groups. We suggest that behavioural characteristics related to trophic specialization can constrain the evolution of the environmental niche and lead to conserved niches in specialist lineages. Our results show the extent of influence of several traits on the evolution of the environmental niche and shed new light on the evolution of damselfishes, which is a key lineage in current efforts to conserve biodiversity in coral reefs.

Trophic specialization influences the rate of environmental niche evolution in damselfishes (Pomacentridae)

PubMed Central

Litsios, Glenn; Pellissier, Loïc; Forest, Félix; Lexer, Christian; Pearman, Peter B.; Zimmermann, Niklaus E.; Salamin, Nicolas

2012-01-01

The rate of environmental niche evolution describes the capability of species to explore the available environmental space and is known to vary among species owing to lineage-specific factors. Trophic specialization is a main force driving species evolution and is responsible for classical examples of adaptive radiations in fishes. We investigate the effect of trophic specialization on the rate of environmental niche evolution in the damselfish, Pomacentridae, which is an important family of tropical reef fishes. First, phylogenetic niche conservatism is not detected in the family using a standard test of phylogenetic signal, and we demonstrate that the environmental niches of damselfishes that differ in trophic specialization are not equivalent while they still overlap at their mean values. Second, we estimate the relative rates of niche evolution on the phylogenetic tree and show the heterogeneity among rates of environmental niche evolution of the three trophic groups. We suggest that behavioural characteristics related to trophic specialization can constrain the evolution of the environmental niche and lead to conserved niches in specialist lineages. Our results show the extent of influence of several traits on the evolution of the environmental niche and shed new light on the evolution of damselfishes, which is a key lineage in current efforts to conserve biodiversity in coral reefs. PMID:22719034

Determining the trophic guilds of fishes and macroinvertebrates in a seagrass food web

USGS Publications Warehouse

Luczkovich, J.J.; Ward, G.P.; Johnson, J.C.; Christian, R.R.; Baird, D.; Neckles, H.; Rizzo, W.M.

2002-01-01

We established trophic guilds of macroinvertebrate and fish taxa using correspondence analysis and a hierarchical clustering strategy for a seagrass food web in winter in the northeastern Gulf of Mexico. To create the diet matrix, we characterized the trophic linkages of macroinvertebrate and fish taxa present in Halodule wrightii seagrass habitat areas within the St. Marks National Wildlife Refuge (Florida) using binary data, combining dietary links obtained from relevant literature for macroinvertebrates with stomach analysis of common fishes collected during January and February of 1994. Heirarchical average-linkage cluster analysis of the 73 taxa of fishes and macroinvertebrates in the diet matrix yielded 14 clusters with diet similarity ??? 0.60. We then used correspondence analysis with three factors to jointly plot the coordinates of the consumers (identified by cluster membership) and of the 33 food sources. Correspondence analysis served as a visualization tool for assigning each taxon to one of eight trophic guilds: herbivores, detritivores, suspension feeders, omnivores, molluscivores, meiobenthos consumers, macrobenthos consumers, and piscivores. These trophic groups, cross-classified with major taxonomic groups, were further used to develop consumer compartments in a network analysis model of carbon flow in this seagrass ecosystem. The method presented here should greatly improve the development of future network models of food webs by providing an objective procedure for aggregating trophic groups.

Global Trophic Position Comparison of Two Dominant Mesopelagic Fish Families (Myctophidae, Stomiidae) Using Amino Acid Nitrogen Isotopic Analyses

PubMed Central

Choy, C. Anela; Davison, Peter C.; Drazen, Jeffrey C.; Flynn, Adrian; Gier, Elizabeth J.; Hoffman, Joel C.; McClain-Counts, Jennifer P.; Miller, Todd W.; Popp, Brian N.; Ross, Steve W.; Sutton, Tracey T.

2012-01-01

The δ15N values of organisms are commonly used across diverse ecosystems to estimate trophic position and infer trophic connectivity. We undertook a novel cross-basin comparison of trophic position in two ecologically well-characterized and different groups of dominant mid-water fish consumers using amino acid nitrogen isotope compositions. We found that trophic positions estimated from the δ15N values of individual amino acids are nearly uniform within both families of these fishes across five global regions despite great variability in bulk tissue δ15N values. Regional differences in the δ15N values of phenylalanine confirmed that bulk tissue δ15N values reflect region-specific water mass biogeochemistry controlling δ15N values at the base of the food web. Trophic positions calculated from amino acid isotopic analyses (AA-TP) for lanternfishes (family Myctophidae) (AA-TP ∼2.9) largely align with expectations from stomach content studies (TP ∼3.2), while AA-TPs for dragonfishes (family Stomiidae) (AA-TP ∼3.2) were lower than TPs derived from stomach content studies (TP∼4.1). We demonstrate that amino acid nitrogen isotope analysis can overcome shortcomings of bulk tissue isotope analysis across biogeochemically distinct systems to provide globally comparative information regarding marine food web structure. PMID:23209656

Untangling interactions: do temperature and habitat fragmentation gradients simultaneously impact biotic relationships?

PubMed Central

Lakeman-Fraser, Poppy; Ewers, Robert M.

2014-01-01

Gaining insight into the impact of anthropogenic change on ecosystems requires investigation into interdependencies between multiple drivers of ecological change and multiple biotic responses. Global environmental change drivers can act simultaneously to impact the abundance and diversity of biota, but few studies have also measured the impact across trophic levels. We firstly investigated whether climate (using temperature differences across a latitudinal gradient as a surrogate) interacts with habitat fragmentation (measured according to fragment area and distance to habitat edges) to impact a New Zealand tri-trophic food chain (plant, herbivore and natural enemy). Secondly, we examined how these interactions might differentially impact both the density and biotic processes of species at each of the three trophic levels. We found evidence to suggest that these drivers act non-additively across trophic levels. The nature of these interactions however varied: location synergistically interacted with fragmentation measures to exacerbate the detrimental effects on consumer density; and antagonistically interacted to ameliorate the impact on plant density and on the interactions between trophic levels (herbivory and parasitoid attack rate). Our findings indicate that the ecological consequences of multiple global change drivers are strongly interactive and vary according to the trophic level studied and whether density or ecological processes are investigated. PMID:24898374

Global trophic position comparison of two dominant mesopelagic fish families (Myctophidae, Stomiidae) using amino acid nitrogen isotopic analyses

USGS Publications Warehouse

Choy, C. Anela; Davison, Peter C.; Drazen, Jeffrey C.; Flynn, Adrian; Gier, Elizabeth J.; Hoffman, Joel C.; McClain-Counts, Jennifer P.; Miller, Todd W.; Popp, Brian N.; Ross, Steve W.; Sutton, Tracey T.

2012-01-01

The δ15N values of organisms are commonly used across diverse ecosystems to estimate trophic position and infer trophic connectivity. We undertook a novel cross-basin comparison of trophic position in two ecologically well-characterized and different groups of dominant mid-water fish consumers using amino acid nitrogen isotope compositions. We found that trophic positions estimated from the δ15N values of individual amino acids are nearly uniform within both families of these fishes across five global regions despite great variability in bulk tissue δ15N values. Regional differences in the δ15N values of phenylalanine confirmed that bulk tissue δ15N values reflect region-specific water mass biogeochemistry controlling δ15N values at the base of the food web. Trophic positions calculated from amino acid isotopic analyses (AA-TP) for lanternfishes (family Myctophidae) (AA-TP ~2.9) largely align with expectations from stomach content studies (TP ~3.2), while AA-TPs for dragonfishes (family Stomiidae) (AA-TP ~3.2) were lower than TPs derived from stomach content studies (TP~4.1). We demonstrate that amino acid nitrogen isotope analysis can overcome shortcomings of bulk tissue isotope analysis across biogeochemically distinct systems to provide globally comparative information regarding marine food web structure.

The gut microbiome and degradation enzyme activity of wild freshwater fishes influenced by their trophic levels

PubMed Central

Liu, Han; Guo, Xianwu; Gooneratne, Ravi; Lai, Ruifang; Zeng, Cong; Zhan, Fanbin; Wang, Weimin

2016-01-01

Vertebrate gut microbiome often underpins the metabolic capability and provides many beneficial effects on their hosts. However, little was known about how host trophic level influences fish gut microbiota and metabolic activity. In this study, more than 985,000 quality-filtered sequences from 24 16S rRNA libraries were obtained and the results revealed distinct compositions and diversities of gut microbiota in four trophic categories. PCoA test showed that gut bacterial communities of carnivorous and herbivorous fishes formed distinctly different clusters in PCoA space. Although fish in different trophic levels shared a large size of OTUs comprising a core microbiota community, at the genus level a strong distinction existed. Cellulose-degrading bacteria Clostridium, Citrobacter and Leptotrichia were dominant in the herbivorous, while Cetobacterium and protease-producing bacteria Halomonas were dominant in the carnivorous. PICRUSt predictions of metagenome function revealed that fishes in different trophic levels affected the metabolic capacity of their gut microbiota. Moreover, cellulase and amylase activities in herbivorous fishes were significantly higher than in the carnivorous, while trypsin activity in the carnivorous was much higher than in the herbivorous. These results indicated that host trophic level influenced the structure and composition of gut microbiota, metabolic capacity and gut content enzyme activity. PMID:27072196

Assessment of multi-trophic changes in a shallow boreal lake simultaneously exposed to climate change and aerial deposition of contaminants from the Athabasca Oil Sands Region, Canada.

PubMed

Summers, Jamie C; Kurek, Joshua; Rühland, Kathleen M; Neville, Erin E; Smol, John P

2017-08-15

The Athabasca Oil Sands Region (AOSR) has been intensely developed for industrial bitumen extraction and upgrading since the 1980s. A paucity of environmental monitoring prior to development raises questions about baseline conditions in freshwater systems in the region and ecological responses to industrial activities. Further, climatic changes prompt questions about the relative roles of climate and industry in shaping aquatic ecosystems through time. We use aquatic bioindicators from multiple trophic levels, concentrations of petrogenic contaminants (dibenzothiophenes), and spectrally-inferred chlorophyll-a preserved in well-dated sediments of a closed-basin, shallow lake ~50km away from the main area of industry, in conjunction with climate observations, to assess how the biotic assemblages of a typical AOSR lake have changed during the past ~75years. We examine the contributions of the area's stressors in structuring aquatic communities. Increases in sedimentary measures of petrogenic contaminants provide clear evidence of aerial contaminant deposition from local industry since its establishment, while climate records demonstrate consistent warming and a recent period of reduced precipitation. Quantitative comparisons of biological assemblages from before and after the establishment of regional industry find significant (p<0.05) differences; however, the magnitude and overall timing of the changes are not consistent with a threshold-type shift in response to the onset of regional industry. Rather, biotic assemblages from multiple trophic levels suggest transitions to an increasingly complex benthic environment and relatively warmer waters, which, like the increasing trends in inferred primary production, are consistent with a changing climate. These findings highlight the important role of climate conditions in regulating primary production and structuring aquatic communities in these shallow systems. Copyright © 2017 Elsevier B.V. All rights reserved.

Regenerative effects of human embryonic stem cell-derived neural crest cells for treatment of peripheral nerve injury.

PubMed

Jones, Iwan; Novikova, Liudmila N; Novikov, Lev N; Renardy, Monika; Ullrich, Andreas; Wiberg, Mikael; Carlsson, Leif; Kingham, Paul J

2018-04-01

Surgical intervention is the current gold standard treatment following peripheral nerve injury. However, this approach has limitations, and full recovery of both motor and sensory modalities often remains incomplete. The development of artificial nerve grafts that either complement or replace current surgical procedures is therefore of paramount importance. An essential component of artificial grafts is biodegradable conduits and transplanted cells that provide trophic support during the regenerative process. Neural crest cells are promising support cell candidates because they are the parent population to many peripheral nervous system lineages. In this study, neural crest cells were differentiated from human embryonic stem cells. The differentiated cells exhibited typical stellate morphology and protein expression signatures that were comparable with native neural crest. Conditioned media harvested from the differentiated cells contained a range of biologically active trophic factors and was able to stimulate in vitro neurite outgrowth. Differentiated neural crest cells were seeded into a biodegradable nerve conduit, and their regeneration potential was assessed in a rat sciatic nerve injury model. A robust regeneration front was observed across the entire width of the conduit seeded with the differentiated neural crest cells. Moreover, the up-regulation of several regeneration-related genes was observed within the dorsal root ganglion and spinal cord segments harvested from transplanted animals. Our results demonstrate that the differentiated neural crest cells are biologically active and provide trophic support to stimulate peripheral nerve regeneration. Differentiated neural crest cells are therefore promising supporting cell candidates to aid in peripheral nerve repair. © 2018 The Authors. Journal of Tissue Engineering and Regenerative Medicine published by John Wiley & Sons, Ltd.

Species richness and trophic diversity increase decomposition in a co-evolved food web.

PubMed

Baiser, Benjamin; Ardeshiri, Roxanne S; Ellison, Aaron M

2011-01-01

Ecological communities show great variation in species richness, composition and food web structure across similar and diverse ecosystems. Knowledge of how this biodiversity relates to ecosystem functioning is important for understanding the maintenance of diversity and the potential effects of species losses and gains on ecosystems. While research often focuses on how variation in species richness influences ecosystem processes, assessing species richness in a food web context can provide further insight into the relationship between diversity and ecosystem functioning and elucidate potential mechanisms underpinning this relationship. Here, we assessed how species richness and trophic diversity affect decomposition rates in a complete aquatic food web: the five trophic level web that occurs within water-filled leaves of the northern pitcher plant, Sarracenia purpurea. We identified a trophic cascade in which top-predators--larvae of the pitcher-plant mosquito--indirectly increased bacterial decomposition by preying on bactivorous protozoa. Our data also revealed a facultative relationship in which larvae of the pitcher-plant midge increased bacterial decomposition by shredding detritus. These important interactions occur only in food webs with high trophic diversity, which in turn only occur in food webs with high species richness. We show that species richness and trophic diversity underlie strong linkages between food web structure and dynamics that influence ecosystem functioning. The importance of trophic diversity and species interactions in determining how biodiversity relates to ecosystem functioning suggests that simply focusing on species richness does not give a complete picture as to how ecosystems may change with the loss or gain of species.

Species Richness and Trophic Diversity Increase Decomposition in a Co-Evolved Food Web

PubMed Central

Baiser, Benjamin; Ardeshiri, Roxanne S.; Ellison, Aaron M.

2011-01-01

Ecological communities show great variation in species richness, composition and food web structure across similar and diverse ecosystems. Knowledge of how this biodiversity relates to ecosystem functioning is important for understanding the maintenance of diversity and the potential effects of species losses and gains on ecosystems. While research often focuses on how variation in species richness influences ecosystem processes, assessing species richness in a food web context can provide further insight into the relationship between diversity and ecosystem functioning and elucidate potential mechanisms underpinning this relationship. Here, we assessed how species richness and trophic diversity affect decomposition rates in a complete aquatic food web: the five trophic level web that occurs within water-filled leaves of the northern pitcher plant, Sarracenia purpurea. We identified a trophic cascade in which top-predators — larvae of the pitcher-plant mosquito — indirectly increased bacterial decomposition by preying on bactivorous protozoa. Our data also revealed a facultative relationship in which larvae of the pitcher-plant midge increased bacterial decomposition by shredding detritus. These important interactions occur only in food webs with high trophic diversity, which in turn only occur in food webs with high species richness. We show that species richness and trophic diversity underlie strong linkages between food web structure and dynamics that influence ecosystem functioning. The importance of trophic diversity and species interactions in determining how biodiversity relates to ecosystem functioning suggests that simply focusing on species richness does not give a complete picture as to how ecosystems may change with the loss or gain of species. PMID:21673992

Light, nutrients, and food-chain length constrain planktonic energy transfer efficiency across multiple trophic levels

PubMed Central

Dickman, Elizabeth M.; Newell, Jennifer M.; González, María J.; Vanni, Michael J.

2008-01-01

The efficiency of energy transfer through food chains [food chain efficiency (FCE)] is an important ecosystem function. It has been hypothesized that FCE across multiple trophic levels is constrained by the efficiency at which herbivores use plant energy, which depends on plant nutritional quality. Furthermore, the number of trophic levels may also constrain FCE, because herbivores are less efficient in using plant production when they are constrained by carnivores. These hypotheses have not been tested experimentally in food chains with 3 or more trophic levels. In a field experiment manipulating light, nutrients, and food-chain length, we show that FCE is constrained by algal food quality and food-chain length. FCE across 3 trophic levels (phytoplankton to carnivorous fish) was highest under low light and high nutrients, where algal quality was best as indicated by taxonomic composition and nutrient stoichiometry. In 3-level systems, FCE was constrained by the efficiency at which both herbivores and carnivores converted food into production; a strong nutrient effect on carnivore efficiency suggests a carryover effect of algal quality across 3 trophic levels. Energy transfer efficiency from algae to herbivores was also higher in 2-level systems (without carnivores) than in 3-level systems. Our results support the hypothesis that FCE is strongly constrained by light, nutrients, and food-chain length and suggest that carryover effects across multiple trophic levels are important. Because many environmental perturbations affect light, nutrients, and food-chain length, and many ecological services are mediated by FCE, it will be important to apply these findings to various ecosystem types. PMID:19011082

Employing citizen science to study defoliation impacts on arthropod communities on tamarisk

NASA Astrophysics Data System (ADS)

Kruse, Audrey L.

The invasive tamarisk tree is widespread across the southwestern landscape of the United States and has been dominant in regulated river reaches, outcompeting native vegetation and impacting trophic webs in riparian ecosystems. The changes in riparian habitat and recreation opportunities along southwestern rivers, like the San Juan River in Utah, led to the implementation of a biocontrol program in the form of the tamarisk leaf beetle (Diorhabda spp.). It is unknown what the long term effects on riparian ecosystems are as a result of the beetles' defoliation of tamarisk each summer. This study sought to identify the current arthropod community composition and abundance over one growing season on the San Juan River between Bluff and Mexican Hat, UT and second, to involve the public in this research through a citizen science component. I found that non-native insects, including the tamarisk leaf beetle, dominated the arboreal arthropod communities within the tamarisk and there are relatively few native arthropods residing in tamarisk throughout the summer season. Foliation levels (the quantity of leaves in the canopy of tamarisk) were inconclusive predictors of arthropod abundances but varied by species and by feeding guild. This may indicate that the defoliation of the tamarisk is not necessarily negatively impacting trophic interactions in tamarisk. I incorporated youth participants on educational river rafting trips to assist in data collection of arthropods from tamarisk trees as a way to educate and bring attention to the issue of invasive species in the Southwest. After completing my own citizen science project and after doing a literature review of other, similar citizen science projects, I found that striving for both rigorous scientific data and quality educational programming is challenging for a small scale project that does not target broad spatial, geographic, or temporal data. Citizen science project developers should clearly identify their objectives and spend time developing and evaluating both the data quality and the educational quality of citizen science programs to achieve credibility in both realms.

Trophic flexibility of the Atlantic blue crab Callinectes sapidus in invaded coastal systems of the Apulia region (SE Italy): A stable isotope analysis

NASA Astrophysics Data System (ADS)

Mancinelli, Giorgio; Teresa Guerra, Maria; Alujević, Karla; Raho, Davide; Zotti, Maurizio; Vizzini, Salvatrice

2017-11-01

The Atlantic blue crab Callinectes sapidus is recognized as an Invasive Alien Species in the Mediterranean Sea. However, its trophic role and feeding flexibility in invaded benthic food webs have been addressed only recently. Here, field samplings were conducted in winter and summer in five coastal systems of the Apulia region (SE Italy), three located on the Ionian Sea (Mar Piccolo, Torre Colimena, and Spunderati) and two on the Adriatic Sea (Acquatina and Alimini Grande). Captured blue crabs were weighed and had their δ13C and δ15N isotopic signatures measured; their trophic level (TL) was estimated using the mussel Mytilus galloprovincialis as isotopic baseline. C. sapidus abundances varied greatly across systems and seasons, and in Adriatic systems the species was not collected in winter. Trophic levels showed significant spatial and temporal variations, although with no general pattern. In winter, the Mar Piccolo population showed the highest TL values; the lowest estimates were in Torre Colimena and Spunderati, where crabs showed δ13C signatures significantly higher than mussels, suggesting the contribution of 13C-enriched plant material in the diet. In summer, with the exception of the Mar Piccolo, Ionian populations increased their trophic level; both Adriatic populations were characterized by the lowest TL estimates. The analysis performed at the individual scale further indicated body weight-related changes in trophic level. For the Torre Colimena population, in particular, a hump-shaped pattern was observed in both seasons. The present study highlighted a considerable spatial and temporal trophic flexibility of C. sapidus at the population scale, while at the individual scale size-related shifts in trophic level were observed. The ability of the blue crab to vary its energy sources in relation with season, local environmental conditions, and ontogenetic stage is emphasized, suggesting that it may represent a key determinant of its invasion success.

Measuring variability in trophic status in the Lake Waco/Bosque River Watershed

PubMed Central

Rodriguez, Angela D; Matlock, Marty D

2008-01-01

Background Nutrient management in rivers and streams is difficult due to the spatial and temporal variability of algal growth responses. The objectives of this project were to determine the spatial and seasonal in situ variability of trophic status in the Lake Waco/Bosque River watershed, determine the variability in the lotic ecosystem trophic status index (LETSI) at each site as indicators of the system's nutrient sensitivity, and determine if passive diffusion periphytometers could provide threshold algal responses to nutrient enrichment. Methods We used the passive diffusion periphytometer to measure in-situ nutrient limitation and trophic status at eight sites in five streams in the Lake Waco/Bosque River Watershed in north-central Texas from July 1997 through October 1998. The chlorophyll a production in the periphytometers was used as an indicator of baseline chlorophyll a productivity and of maximum primary productivity (MPP) in response to nutrient enrichment (nitrogen and phosphorus). We evaluated the lotic ecosystem trophic status index (LETSI) using the ratio of baseline primary productivity to MPP, and evaluated the trophic class of each site. Results The rivers and streams in the Lake Waco/Bosque River Watershed exhibited varying degrees of nutrient enrichment over the 18-month sampling period. The North Bosque River at the headwaters (NB-02) located below the Stephenville, Texas wastewater treatment outfall consistently exhibited the highest degree of water quality impact due to nutrient enrichment. Sites at the outlet of the watershed (NB-04 and NB-05) were the next most enriched sites. Trophic class varied for enriched sites over seasons. Conclusion Seasonality played a significant role in the trophic class and sensitivity of each site to nutrients. Managing rivers and streams for nutrients will require methods for measuring in situ responses and sensitivities to nutrient enrichment. Nutrient enrichment periphytometers show significant potential for use in nutrient gradient studies. PMID:18271947

Measuring variability in trophic status in the Lake Waco/Bosque River Watershed.

PubMed

Rodriguez, Angela D; Matlock, Marty D

2008-01-11

Nutrient management in rivers and streams is difficult due to the spatial and temporal variability of algal growth responses. The objectives of this project were to determine the spatial and seasonal in situ variability of trophic status in the Lake Waco/Bosque River watershed, determine the variability in the lotic ecosystem trophic status index (LETSI) at each site as indicators of the system's nutrient sensitivity, and determine if passive diffusion periphytometers could provide threshold algal responses to nutrient enrichment. We used the passive diffusion periphytometer to measure in-situ nutrient limitation and trophic status at eight sites in five streams in the Lake Waco/Bosque River Watershed in north-central Texas from July 1997 through October 1998. The chlorophyll a production in the periphytometers was used as an indicator of baseline chlorophyll a productivity and of maximum primary productivity (MPP) in response to nutrient enrichment (nitrogen and phosphorus). We evaluated the lotic ecosystem trophic status index (LETSI) using the ratio of baseline primary productivity to MPP, and evaluated the trophic class of each site. The rivers and streams in the Lake Waco/Bosque River Watershed exhibited varying degrees of nutrient enrichment over the 18-month sampling period. The North Bosque River at the headwaters (NB-02) located below the Stephenville, Texas wastewater treatment outfall consistently exhibited the highest degree of water quality impact due to nutrient enrichment. Sites at the outlet of the watershed (NB-04 and NB-05) were the next most enriched sites. Trophic class varied for enriched sites over seasons. Seasonality played a significant role in the trophic class and sensitivity of each site to nutrients. Managing rivers and streams for nutrients will require methods for measuring in situ responses and sensitivities to nutrient enrichment. Nutrient enrichment periphytometers show significant potential for use in nutrient gradient studies.

Influence of climate change and trophic coupling across four trophic levels in the Celtic Sea.

PubMed

Lauria, Valentina; Attrill, Martin J; Pinnegar, John K; Brown, Andrew; Edwards, Martin; Votier, Stephen C

2012-01-01

Climate change has had profound effects upon marine ecosystems, impacting across all trophic levels from plankton to apex predators. Determining the impacts of climate change on marine ecosystems requires understanding the direct effects on all trophic levels as well as indirect effects mediated by trophic coupling. The aim of this study was to investigate the effects of climate change on the pelagic food web in the Celtic Sea, a productive shelf region in the Northeast Atlantic. Using long-term data, we examined possible direct and indirect 'bottom-up' climate effects across four trophic levels: phytoplankton, zooplankton, mid-trophic level fish and seabirds. During the period 1986-2007, although there was no temporal trend in the North Atlantic Oscillation index (NAO), the decadal mean Sea Surface Temperature (SST) in the Celtic Sea increased by 0.66 ± 0.02 °C. Despite this, there was only a weak signal of climate change in the Celtic Sea food web. Changes in plankton community structure were found, however this was not related to SST or NAO. A negative relationship occurred between herring abundance (0- and 1-group) and spring SST (0-group: p = 0.02, slope = -0.305 ± 0.125; 1-group: p = 0.04, slope = -0.410 ± 0.193). Seabird demographics showed complex species-specific responses. There was evidence of direct effects of spring NAO (on black-legged kittiwake population growth rate: p = 0.03, slope = 0.0314 ± 0.014) as well as indirect bottom-up effects of lagged spring SST (on razorbill breeding success: p = 0.01, slope = -0.144 ± 0.05). Negative relationships between breeding success and population growth rate of razorbills and common guillemots may be explained by interactions between mid-trophic level fish. Our findings show that the impacts of climate change on the Celtic Sea ecosystem is not as marked as in nearby regions (e.g. the North Sea), emphasizing the need for more research at regional scales.

Herbivory drives large-scale spatial variation in reef fish trophic interactions

PubMed Central

Longo, Guilherme O; Ferreira, Carlos Eduardo L; Floeter, Sergio R

2014-01-01

Trophic interactions play a critical role in the structure and function of ecosystems. Given the widespread loss of biodiversity due to anthropogenic activities, understanding how trophic interactions respond to natural gradients (e.g., abiotic conditions, species richness) through large-scale comparisons can provide a broader understanding of their importance in changing ecosystems and support informed conservation actions. We explored large-scale variation in reef fish trophic interactions, encompassing tropical and subtropical reefs with different abiotic conditions and trophic structure of reef fish community. Reef fish feeding pressure on the benthos was determined combining bite rates on the substrate and the individual biomass per unit of time and area, using video recordings in three sites between latitudes 17°S and 27°S on the Brazilian Coast. Total feeding pressure decreased 10-fold and the composition of functional groups and species shifted from the northern to the southernmost sites. Both patterns were driven by the decline in the feeding pressure of roving herbivores, particularly scrapers, while the feeding pressure of invertebrate feeders and omnivores remained similar. The differential contribution to the feeding pressure across trophic categories, with roving herbivores being more important in the northernmost and southeastern reefs, determined changes in the intensity and composition of fish feeding pressure on the benthos among sites. It also determined the distribution of trophic interactions across different trophic categories, altering the evenness of interactions. Feeding pressure was more evenly distributed at the southernmost than in the southeastern and northernmost sites, where it was dominated by few herbivores. Species and functional groups that performed higher feeding pressure than predicted by their biomass were identified as critical for their potential to remove benthic biomass. Fishing pressure unlikely drove the large-scale pattern; however, it affected the contribution of some groups on a local scale (e.g., large-bodied parrotfish) highlighting the need to incorporate critical functions into conservation strategies. PMID:25512851

Quantifying Trophic Interactions and Carbon Flow in Louisiana Salt Marshes Using Multiple Biomarkers

NASA Astrophysics Data System (ADS)

Polito, M. J.; Lopez-Duarte, P. C.; Olin, J.; Johnson, J. J.; Able, K.; Martin, C. W.; Fodrie, J.; Hooper-Bui, L. M.; Taylor, S.; Stouffer, P.; Roberts, B. J.; Rabalais, N. N.; Jensen, O.

2017-12-01

Salt marshes are critical habitats for many species in the northern Gulf of Mexico. However, given their complex nature, quantifying trophic linkages and the flow of carbon through salt marsh food webs is challenging. This gap in our understanding of food web structure and function limits our ability to evaluate the impacts of natural and anthropogenic stressors on salt marsh ecosystems. For example, 2010 Deepwater Horizon (DWH) oil spill had the potential to alter trophic and energy pathways. Even so, our ability to evaluate its effects on Louisiana salt marsh food webs was limited by a poor basis for comparison of the pre-spill baseline food web. To be better equipped to measure significant alterations in salt marsh ecosystems in the future, we quantified trophic interactions at two marsh sites in Barataria Bay, LA in May and October of 2015. Trophic structure and carbon flow across 52 species of saltmarsh primary producers and consumers were examined through a combination of three approaches: bulk tissue stable isotope analysis (δ13C, δ15N, δ34S), dietary fatty acid analysis (FAA), and compound-specific stable isotope analysis of essential amino acids (δ13C EAA). Bulk stable isotope analysis indicated similar trophic diversity between sites and seasons with the use of aquatic resources increasing concomitantly with trophic level. FAA and δ13C EAA biomarkers revealed that marsh organisms were largely divided into two groups: those that primarily derive carbon from terrestrial C4 grasses, and those that predominately derive carbon from a combination of phytoplankton and benthic microalgal sources. Differences in trophic structure and carbon flow were minimal between seasons and sites that were variably impacted by the DWH spill. These data on salt marsh ecosystem structure will be useful to inform future injury assessments and restoration initiatives.

Ontogenetic, spatial and temporal variation in trophic level and diet of Chukchi Sea fishes

NASA Astrophysics Data System (ADS)

Marsh, Jennifer M.; Mueter, Franz J.; Iken, Katrin; Danielson, Seth

2017-01-01

Climate warming and increasing development are expected to alter the ecosystem of the Chukchi Sea, including its fish communities. As a component of the Arctic Ecosystem Integrated Survey, we assessed the ontogenetic, spatial and temporal variability of the trophic level and diet of key fish species in the Chukchi Sea using N and C stable isotopes. During August and September of 2012 and 2013, 16 common fish species and two primary, invertebrate consumers were collected from surface, midwater and bottom trawls within the eastern Chukchi Sea. Linear mixed-effects models were used to detect possible variation in the relationship between body length and either δ13C or δ15N values among water masses and years for 13 fish species with an emphasis on Arctic cod (Boreogadus saida). We also examined the fish community isotopic niche space, trophic redundancy, and trophic separation within each water mass as measures of resiliency of the fish food web. Ontogenetic shifts in trophic level and diet were observed for most species and these changes tended to vary by water mass. As they increased in length, most fish species relied more on benthic prey with the exception of three forage fish species (walleye pollock, Gadus chalcogrammus, capelin, Mallotus villosus, and Pacific sandlance, Ammodytes hexapterus). Species that exhibited interannual differences in diet and trophic level were feeding at lower trophic levels and consumed a more pelagic diet in 2012 when zooplankton densities were higher. Fish communities occupied different isotopic niche spaces depending on water mass association. In more northerly Arctic waters, the fish community occupied the smallest isotopic niche space and relied heavily on a limited range of intermediate δ13C prey, whereas in warmer, nutrient-rich Bering Chukchi Summer Water, pelagic prey was important. In the warmest, Pacific-derived coastal water, fish consumed both benthic and pelagic prey. Examining how spatial gradients in trophic position are linked to environmental drivers can provide insight into potential fish community shifts with a changing climate.

Food-web inferences of stable isotope spatial patterns in copepods and yellowfin tuna in the pelagic eastern Pacific Ocean

NASA Astrophysics Data System (ADS)

Olson, Robert J.; Popp, Brian N.; Graham, Brittany S.; López-Ibarra, Gladis A.; Galván-Magaña, Felipe; Lennert-Cody, Cleridy E.; Bocanegra-Castillo, Noemi; Wallsgrove, Natalie J.; Gier, Elizabeth; Alatorre-Ramírez, Vanessa; Ballance, Lisa T.; Fry, Brian

2010-07-01

Evaluating the impacts of climate and fishing on oceanic ecosystems requires an improved understanding of the trophodynamics of pelagic food webs. Our approach was to examine broad-scale spatial relationships among the stable N isotope values of copepods and yellowfin tuna ( Thunnus albacares), and to quantify yellowfin tuna trophic status in the food web based on stable-isotope and stomach-contents analyses. Using a generalized additive model fitted to abundance-weighted-average δ 15N values of several omnivorous copepod species, we examined isotopic spatial relationships among yellowfin tuna and copepods. We found a broad-scale, uniform gradient in δ 15N values of copepods increasing from south to north in a region encompassing the eastern Pacific warm pool and parts of several current systems. Over the same region, a similar trend was observed for the δ 15N values in the white muscle of yellowfin tuna caught by the purse-seine fishery, implying limited movement behavior. Assuming the omnivorous copepods represent a proxy for the δ 15N values at the base of the food web, the isotopic difference between these two taxa, “ ΔYFT-COP,” was interpreted as a trophic-position offset. Yellowfin tuna trophic-position estimates based on their bulk δ 15N values were not significantly different than independent estimates based on stomach contents, but are sensitive to errors in the trophic enrichment factor and the trophic position of copepods. An apparent inshore-offshore, east to west gradient in yellowfin tuna trophic position was corroborated using compound-specific isotope analysis of amino acids conducted on a subset of samples. The gradient was not explained by the distribution of yellowfin tuna of different sizes, by seasonal variability at the base of the food web, or by known ambit distances (i.e. movements). Yellowfin tuna stomach contents did not show a regular inshore-offshore gradient in trophic position during 2003-2005, but the trophic-position estimates based on both methods had similar scales of variability. We conclude that trophic status of yellowfin tuna increased significantly from east to west over the study area based on the spatial pattern of ΔYFT-COP values and the difference between the δ 15N values of glutamic acid and glycine, “trophic” and “source” amino acids, respectively. These results provide improved depictions of trophic links and biomass flows for food-web models, effective tools to evaluate climate and fishing effects on exploited ecosystems.

Near-future pH conditions severely impact calcification, metabolism and the nervous system in the pteropod Heliconoides inflatus.

PubMed

Moya, Aurelie; Howes, Ella L; Lacoue-Labarthe, Thomas; Forêt, Sylvain; Hanna, Bishoy; Medina, Mónica; Munday, Philip L; Ong, Jue-Sheng; Teyssié, Jean-Louis; Torda, Gergely; Watson, Sue-Ann; Miller, David J; Bijma, Jelle; Gattuso, Jean-Pierre

2016-12-01

Shelled pteropods play key roles in the global carbon cycle and food webs of various ecosystems. Their thin external shell is sensitive to small changes in pH, and shell dissolution has already been observed in areas where aragonite saturation state is ~1. A decline in pteropod abundance has the potential to disrupt trophic networks and directly impact commercial fisheries. Therefore, it is crucial to understand how pteropods will be affected by global environmental change, particularly ocean acidification. In this study, physiological and molecular approaches were used to investigate the response of the Mediterranean pteropod, Heliconoides inflatus, to pH values projected for 2100 under a moderate emissions trajectory (RCP6.0). Pteropods were subjected to pH T 7.9 for 3 days, and gene expression levels, calcification and respiration rates were measured relative to pH T 8.1 controls. Gross calcification decreased markedly under low pH conditions, while genes potentially involved in calcification were up-regulated, reflecting the inability of pteropods to maintain calcification rates. Gene expression data imply that under low pH conditions, both metabolic processes and protein synthesis may be compromised, while genes involved in acid-base regulation were up-regulated. A large number of genes related to nervous system structure and function were also up-regulated in the low pH treatment, including a GABA A receptor subunit. This observation is particularly interesting because GABA A receptor disturbances, leading to altered behavior, have been documented in several other marine animals after exposure to elevated CO 2 . The up-regulation of many genes involved in nervous system function suggests that exposure to low pH could have major effects on pteropod behavior. This study illustrates the power of combining physiological and molecular approaches. It also reveals the importance of behavioral analyses in studies aimed at understanding the impacts of low pH on marine animals. © 2016 John Wiley & Sons Ltd.

The transcriptomics of ecological convergence between 2 limnetic coregonine fishes (Salmonidae).

PubMed

Derome, N; Bernatchez, L

2006-12-01

Species living in comparable habitats often display strikingly similar patterns of specialization, suggesting that natural selection can lead to predictable evolutionary changes. Elucidating the genomic basis underlying such adaptive phenotypic changes is a major goal in evolutionary biology. Increasing evidence indicates that natural selection would first modulate gene regulation during the process of population divergence. Previously, we showed that parallel phenotypic adaptations of the dwarf whitefish (Coregonus clupeaformis) ecotype to the limnetic trophic niche involved parallel transcriptional changes at the same genes involved in muscle contraction and energetic metabolism relative to the sympatric normal ecotype. Here, we tested whether the same genes are also implicated in a limnetic specialist species, the cisco (Coregonus artedi), which is the most likely competitor of dwarf whitefish. Significant upregulation was detected in cisco at the same 6 candidate genes functionally involved in modulating swimming activity, namely 5 variants of a major protein of fast muscle and 1 putative catalytic crystallin enzyme. Moreover, 3 of 5 variants and the same putative catalytic crystallin enzyme were upregulated in cisco relative to the dwarf ecotype, indicating a greater physiological potential of the former for exploiting the limnetic trophic niche. This study provides the first empirical evidence that recent, parallel phenotypic evolution toward the use of the same ecological niche occupied by a specialist competitor involved similar adaptive changes in expression at the same genes. As such, this study provides strong support to the general hypothesis that directional selection acting on gene regulation may promote rapid phenotypic divergence and ultimately speciation.

Disruption of Trophic Inhibitory Signaling in Autism Sepctrum Disorders

DTIC Science & Technology

2016-12-01

1 AWARD NUMBER: W81XWH-14-1-0433 TITLE: Disruption of Trophic Inhibitory Signaling in Autism Sepctrum Disorders PRINCIPAL INVESTIGATOR: Anis...SUBTITLE 5a. CONTRACT NUMBER Disruption of Trophic Inhibitory Signaling in Autism Sepctrum Disorders 5b. GRANT NUMBER W81XWH-14-1-0433 5c. PROGRAM...bumetanide to mice rescues synaptic and circuit dysfunction in Fragile X mice. 15. SUBJECT TERMS Autism Spectrum Disorders, Fragile X Syndrome Angelman

Using stable isotopes to test for trophic niche partitioning: a case study with stream salamanders and fish

USGS Publications Warehouse

Sepulveda, Adam; Lowe, Winsor H.; Marra, Peter P.

2012-01-01

5. Although we did not identify mechanisms that facilitate salamander and fish coexistence, our empirical data and use of novel approaches to describe the trophic niche did yield important insights on the role of predator–prey interactions and cannibalism as alternative coexistence mechanisms. In addition, we found that 95% kernel estimators are a simple and robust method to describe population-level measure of trophic structure.

Trophic interactions and direct physical effects control phytoplankton biomass and production in an estuary

USGS Publications Warehouse

Alpine, A.E.; Cloern, J.E.

1992-01-01

San Francisco Bay has recently been invaded by the suspension-feeding clam Potamocorbula amurensis. Previous work has shown that phytoplankton biomass in the upper estuary is low (2-3 mg Chl a m-3) during seasonal periods of high river flow and short residence time and it is usually high (peak >30 mg Chl a m-3) during the summer-autumn seasons of low river flow and long residence time. However since P. amurensis became widespread and abundant in 1987, the summer phytoplankton biomass maximum has disappeared, presumably because of increased grazing pressure by this newly introduced species. For 1977-1990, mean estimated primary production was only 39 g C m-2 yr-1 during years when bivalve suspension feeders were abundant (>2000 m-2), compared to 106 g C m-2 yr-1 when bivalves were absent or present in low numbers. These observations support the hypothesis that seasonal and interannual fluctuations in estuarine phytoplankton biomass and primary production can be regulated jointly by direct physical effects (eg river-driven transport) and trophic interactions (episodes of enhanced grazing pressure by immigrant populations of benthic suspension feeders). -from Authors

Trophic pathways supporting juvenile Chinook and Coho salmon in the glacial Susitna River, Alaska: patterns of freshwater, marine, and terrestrial resource use across a seasonally dynamic habitat mosaic

USGS Publications Warehouse

Rine, Kristin M.; Wipfli, Mark S.; Schoen, Erik R.; Nightengale, Timothy L.; Stricker, Craig A.

2016-01-01

Contributions of terrestrial-, freshwater-, and marine-derived prey resources to stream fishes vary over time and space, altering the energy pathways that regulate production. In this study, we determined large-scale use of these resources by juvenile Chinook and coho salmon (Oncorhynchus tshawytscha and Oncorhynchus kisutch, respectively) in the glacial Susitna River, Alaska. We resolved spatial and temporal trophic patterns among multiple macrohabitat types along a 97 km segment of the river corridor via stable isotope and stomach content analyses. Juvenile salmon were supported primarily by freshwater-derived resources and secondarily by marine and terrestrial sources. The relative contribution of marine-derived prey to rearing salmon was greatest in the fall within off-channel macrohabitats, whereas the contributions of terrestrial invertebrate prey were generally greatest during midsummer, across all macrohabitats. No longitudinal (upstream–downstream) diet pattern was discernable. These results highlight large-scale spatial and seasonal patterns of energy flow and the dynamic interplay of pulsed marine and terrestrial prey subsidies to juvenile Chinook and coho salmon in a large, complex, and relatively pristine glacial river.

l-Serine and glycine serve as major astroglia-derived trophic factors for cerebellar Purkinje neurons

PubMed Central

Furuya, Shigeki; Tabata, Toshihide; Mitoma, Junya; Yamada, Keiko; Yamasaki, Miwako; Makino, Asami; Yamamoto, Toshifumi; Watanabe, Masahiko; Kano, Masanobu; Hirabayashi, Yoshio

2000-01-01

Glial cells support the survival and development of central neurons through the supply of trophic factors. Here we demonstrate that l-serine (l-Ser) and glycine (Gly) also are glia-derived trophic factors. These amino acids are released by astroglial cells and promote the survival, dendritogenesis, and electrophysiological development of cultured cerebellar Purkinje neurons. Although l-Ser and Gly are generally classified as nonessential amino acids, 3-phosphoglycerate dehydrogenase (3PGDH), a key enzyme for their biosynthesis, is not expressed in Purkinje neurons. By contrast, the Bergman glia, a native astroglia in the cerebellar cortex, highly expresses 3PGDH. These data suggest that l-Ser and Gly mediate the trophic actions of glial cells on Purkinje neurons. PMID:11016963

Understanding food webs in the Chesapeake Bay

USGS Publications Warehouse

Keough, J.R.; Haramis, G.M.; Perry, M.C.; Perry, M.C.

2002-01-01

Approaches to predictive modeling and to management of the Chesapeake Bay ecosystem are 'bottom up' (i.e., approaches involve the control of nutrient inputs in attempts to manage plankton productivity) and 'top down' (i.e., approaches involve controls on harvest of fisheries and wildlife in attempts to manage vertebrate populations). Both approaches are limited by a lack of understanding of trophic connections between nutrient inputs, primary producers, and higher trophic level consumers. This project is aimed at identifying trophic structure for the submersed aquatic vegetation habitat of the Chesapeake Bay. We are employing analysis of stable isotope ratios of plant and animal tissues to identify trophic levels and traditional food habits analysis to identify the foods of a number of species of waterfowl.

Image processing developments and applications for water quality monitoring and trophic state determination

NASA Technical Reports Server (NTRS)

Blackwell, R. J.

1982-01-01

Remote sensing data analysis of water quality monitoring is evaluated. Data anaysis and image processing techniques are applied to LANDSAT remote sensing data to produce an effective operational tool for lake water quality surveying and monitoring. Digital image processing and analysis techniques were designed, developed, tested, and applied to LANDSAT multispectral scanner (MSS) data and conventional surface acquired data. Utilization of these techniques facilitates the surveying and monitoring of large numbers of lakes in an operational manner. Supervised multispectral classification, when used in conjunction with surface acquired water quality indicators, is used to characterize water body trophic status. Unsupervised multispectral classification, when interpreted by lake scientists familiar with a specific water body, yields classifications of equal validity with supervised methods and in a more cost effective manner. Image data base technology is used to great advantage in characterizing other contributing effects to water quality. These effects include drainage basin configuration, terrain slope, soil, precipitation and land cover characteristics.

The role of multispectral scanners as data sources for EPA hydrologic models

NASA Technical Reports Server (NTRS)

Slack, R.; Hill, D.

1982-01-01

An estimated cost savings of 30% to 50% was realized from using LANDSAT-derived data as input into a program which simulates hydrologic and water quality processes in natural and man-made water systems. Data from the satellite were used in conjunction with EPA's 11-channel multispectral scanner to obtain maps for characterizing the distribution of turbidity plumes in Flathead Lake and to predict the effect of increasing urbanization in Montana's Flathead River Basin on the lake's trophic state. Multispectral data are also being studied as a possible source of the parameters needed to model the buffering capability of lakes in an effort to evaluate the effect of acid rain in the Adirondacks. Water quality in Lake Champlain, Vermont is being classified using data from the LANDSAT and the EPA MSS. Both contact-sensed and MSS data are being used with multivariate statistical analysis to classify the trophic status of 145 lakes in Illinois and to identify water sampling sites in Appalachicola Bay where contaminants threaten Florida's shellfish.

Complex trophic interactions in kelp forest ecosystems

USGS Publications Warehouse

Estes, J.A.; Danner, E.M.; Doak, D.F.; Konar, B.; Springer, A.M.; Steinberg, P.D.; Tinker, M. Tim; Williams, T.M.

2004-01-01

The distributions and abundances of species and populations change almost continuously. Understanding the processes responsible is perhaps ecology’s most fundamental challenge. Kelp-forest ecosystems in southwest Alaska have undergone several phase shifts between alga- and herbivore-dominated states in recent decades. Overhunting and recovery of sea otters caused the earlier shifts. Studies focusing on these changes demonstrate the importance of top-down forcing processes, a variety of indirect food-web interactions associated with the otter-urchin-kelp trophic cascade, and the role of food-chain length in the coevolution of defense and resistance in plants and their herbivores. This system unexpectedly shifted back to an herbivore-dominated state during the 1990s, because of a sea-otter population collapse that apparently was driven by increased predation by killer whales. Reasons for this change remain uncertain but seem to be linked to the whole-sale collapse of marine mammals in the North Pacific Ocean and southern Bering Sea. We hypothesize that killer whales sequentially "fished down" pinniped and sea-otter populations after their earlier prey, the great whales, were decimated by commercial whaling. The dynamics of kelp forests in southwest Alaska thus appears to have been influenced by an ecological chain reaction that encompassed numerous species and large scales of space and time.

Trophic Ecology and Movement Patters of Tiger Sharks (Galeocerdo Cuvier) off the Western North Atlantic Coastal and Continental Shelf Waters

NASA Astrophysics Data System (ADS)

Sancho, G.; Edman, R.; Frazier, B.; Bubley, W.

2016-02-01

Understanding the trophic dynamics and habitat utilization of apex predators is central to inferring their influence on different marine landscapes and to help design effective management plans for these animals. Tiger sharks (Galeocerdo cuvier) are abundant in shelf and offshore Gulf Stream waters of the western North Atlantic Ocean, and based on movements from individuals captured in Florida and Bahamas, seem to avoid coastal and shelf waters off South Carolina and Georgia. This contradicts reports of tiger sharks regularly being caught nearshore by anglers in these states, indicating that separate sub-populations may exist in the western North Atlantic. In the present study we captured Tiger Sharks in coastal waters off South Carolina in 2014 and 2015 in order to describe their movement patterns through acoustic and satellite tagging, and trophic dynamics through stable isotope analyses. Movement data show that these tiger sharks repeatedly visit particular inshore areas and mainly travel over the continental shelf, but rarely venture offshore beyond the continental shelf edge. Ongoing C and N stable isotope analyses of muscle, blood and skin tissues from adult and juvenile tiger sharks, as well as from potential prey species and primary producers, will help determine if their diets are based on inshore, shelf or offshore based food webs. Tiger sharks exploiting nearshore environments and shelf waters have much higher probabilities of interacting with humans than individuals occupying far offshore Gulf Stream habitats.

Bioaccumulation factors and the steady state assumption for cesium isotopes in aquatic foodwebs near nuclear facilities.

PubMed

Rowan, D J

2013-07-01

Steady state approaches, such as transfer coefficients or bioaccumulation factors, are commonly used to model the bioaccumulation of (137)Cs in aquatic foodwebs from routine operations and releases from nuclear generating stations and other nuclear facilities. Routine releases from nuclear generating stations and facilities, however, often consist of pulses as liquid waste is stored, analyzed to ensure regulatory compliance and then released. The effect of repeated pulse releases on the steady state assumption inherent in the bioaccumulation factor approach has not been evaluated. In this study, I examine the steady state assumption for aquatic biota by analyzing data for two cesium isotopes in the same biota, one isotope in steady state (stable (133)Cs) from geologic sources and the other released in pulses ((137)Cs) from reactor operations. I also compare (137)Cs bioaccumulation factors for similar upstream populations from the same system exposed solely to weapon test (137)Cs, and assumed to be in steady state. The steady state assumption appears to be valid for small organisms at lower trophic levels (zooplankton, rainbow smelt and 0+ yellow perch) but not for older and larger fish at higher trophic levels (walleye). Attempts to account for previous exposure and retention through a biokinetics approach had a similar effect on steady state, upstream and non-steady state, downstream populations of walleye, but were ineffective in explaining the more or less constant deviation between fish with steady state exposures and non-steady state exposures of about 2-fold for all age classes of walleye. These results suggest that for large, piscivorous fish, repeated exposure to short duration, pulse releases leads to much higher (137)Cs BAFs than expected from (133)Cs BAFs for the same fish or (137)Cs BAFs for similar populations in the same system not impacted by reactor releases. These results suggest that the steady state approach should be used with caution in any situation where reactor releases are episodic or pulse in nature, even if the magnitude of these releases is small. Copyright © 2012. Published by Elsevier Ltd.

Short-Lived Human Umbilical Cord-Blood-Derived Neural Stem Cells Influence the Endogenous Secretome and Increase the Number of Endogenous Neural Progenitors in a Rat Model of Lacunar Stroke.

PubMed

Jablonska, Anna; Drela, Katarzyna; Wojcik-Stanaszek, Luiza; Janowski, Miroslaw; Zalewska, Teresa; Lukomska, Barbara

2016-11-01

Stroke is the leading cause of severe disability, and lacunar stroke is related to cognitive decline and hemiparesis. There is no effective treatment for the majority of patients with stroke. Thus, stem cell-based regenerative medicine has drawn a growing body of attention due to the capabilities for trophic factor expression and neurogenesis enhancement. Moreover, it was shown in an experimental autoimmune encephalomyelitis (EAE) model that even short-lived stem cells can be therapeutic, and we have previously observed that phenomenon indirectly. Here, in a rat model of lacunar stroke, we investigated the molecular mechanisms underlying the positive therapeutic effects of short-lived human umbilical cord-blood-derived neural stem cells (HUCB-NSCs) through the distinct measurement of exogenous human and endogenous rat trophic factors. We have also evaluated neurogenesis and metalloproteinase activity as cellular components of therapeutic activity. As expected, we observed an increased proliferation and migration of progenitors, as well as metalloproteinase activity up to 14 days post transplantation. These changes were most prominent at the 7-day time point when we observed 30 % increases in the number of bromodeoxyuridine (BrdU)-positive cells in HUCB-NSC transplanted animals. The expression of human trophic factors was present until 7 days post transplantation, which correlated well with the survival of the human graft. For these 7 days, the level of messenger RNA (mRNA) in the analyzed trophic factors was from 300-fold for CNTF to 10,000-fold for IGF, much higher compared to constitutive expression in HUCB-NSCs in vitro. What is interesting is that there was no increase in the expression of rat trophic factors during the human graft survival, compared to that in non-transplanted animals. However, there was a prolongation of a period of increased trophic expression until 14 days post transplantation, while, in non-transplanted animals, there was a significant drop in rat trophic expression at that time point. We conclude that the positive therapeutic effect of short-lived stem cells may be related to the net increase in the amount of trophic factors (rat + human) until graft death and to the prolonged increase in rat trophic factor expression subsequently.

Trophic position of soil nematodes in boreal forests as indicated by stable isotope analysis

NASA Astrophysics Data System (ADS)

Kudrin, Alexey; Tsurikov, Sergey

2016-04-01

Despite the well-developed trophic classification of soil nematodes, their position in soil food webs is still little understood. Observed deviations from the typical feeding strategy indicate that a simplified trophic classification probably does not fully reflect actual trophic interactions. Furthermore, the extent and functional significance of nematodes as prey for other soil animals remains unknown. Stable isotope analysis (SIA) is powerful tool for investigating the structure of soil food webs, but its application to the study of soil nematodes has been limited to only a few studies. We used stable isotope analysis to gain a better understanding of trophic links of several groups of soil nematodes in two boreal forests on albeluvisol. We investigated four taxonomic groups of nematodes: Mononchida, Dorylaimida, Plectidae and Tylenchidae (mostly from the genus Filenchus), that according to the conventional trophic classification represent predators, omnivores, bacterivores and root-fungal feeders, respectively. To assess the trophic position of nematodes, we used a comparison against a set of reference species including herbivorous, saprophagous and predatory macro-invertebrates, oribatid and mesostigmatid mites, and collembolans. Our results suggest that trophic position of the investigated groups of soil nematodes generally corresponds to the conventional classification. All nematodes were enriched in 13C relative to Picea abies roots and litter, and mycorrhizal fungal mycelium. Root-fungal feeders Tylenchidae had δ15N values similar to those of earthworms, enchytraeids and Entomobrya collembolans, but slightly lower δ13C values. Bacterivorous Plectidae were either equal or enriched in 15N compared with saprophagous macroinvertebrates and most mesofauna species. Omnivorous Dorylaimida and predatory Mononchida were further enriched in 15N and their isotopic signature was similar to that of predatory arthropods. These data confirm a clear separation of nematodes into saprophagous/microbial feeders (Tylenchidae and Plectidae) and predators (Mononchida and Dorylaimida). Furthermore, they suggest that Mononchida and Dorylaimida use different sources of carbon, though exact trophic links remain unclear. As a rule, nematodes were either equal or higher in δ15N values relative to most microbivorous microarthropods, contradicting an emerging view that soil nematodes can be an important prey for a wide range of oribatid mites and collembolans. Patterns of the isotopic signatures suggest that soil nematodes and the bulk of soil animals depend on resources derived from a dominating upper-canopy tree (Picea abies) via the detrital, rather than mycorrhizal pathway.

Do stage-specific functional responses of consumers dampen the effects of subsidies on trophic cascades in streams?

PubMed

Sato, Takuya; Watanabe, Katsutoshi

2014-07-01

Resource subsidies often weaken trophic cascades in recipient communities via consumers' functional response to the subsidies. Consumer populations are commonly stage-structured and may respond to the subsidies differently among the stages yet less is known about how this might impact the subsidy effects on the strength of trophic cascades in recipient systems. We show here, using a large-scale field experiment, that the stage structure of a recipient consumer would dampen the effects of terrestrial invertebrate subsidies on the strength of trophic cascade in streams. When a high input rate of the terrestrial invertebrates was available, both large and small fish stages switched their diet to the terrestrial subsidy, which weakened the trophic cascade in streams. However, when the input rate of the terrestrial invertebrates was at a moderate level, the terrestrial subsidy did not weaken the trophic cascade. This discrepancy was likely due to small fish stages being competitively excluded from feeding on the subsidy by larger stages of fish and primarily foraging on benthic invertebrates under the moderate input level. Although previous studies using single fish stages have clearly demonstrated that the terrestrial invertebrate input equivalent to our moderate input rate weakened the trophic cascade in streams, this subsidy effect might be overestimated given small fish stage may not switch their diet to the subsidy under competition with large fish stage. Given the ubiquity of consumer stage structure and interaction among consumer stages, the effects we saw might be widespread in nature, requiring future studies that explicitly involve consumer's stage structure into community ecology. © 2013 The Authors. Journal of Animal Ecology © 2013 British Ecological Society.

Competition influence in the segregation of the trophic niche of otariids: a case study using isotopic Bayesian mixing models in Galapagos pinnipeds.

PubMed

Páez-Rosas, Diego; Rodríguez-Pérez, Mónica; Riofrío-Lazo, Marjorie

2014-12-15

The feeding success of predators is associated with the competition level for resources, and, thus, sympatric species are exposed to a potential trophic overlap. Isotopic Bayesian mixing models should provide a better understanding of the contribution of preys to the diet of predators and the feeding behavior of a species over time. The carbon and nitrogen isotopic signatures from pup hair samples of 93 Galapagos sea lions and 48 Galapagos fur seals collected between 2003 and 2009 in different regions (east and west) of the archipelago were analyzed. A PDZ Europa ANCA-GSL elemental analyzer interfaced with a PDZ Europa 20-20 continuous flow gas source mass spectrometer was employed. Bayesian models, SIAR and SIBER, were used to estimate the contribution of prey to the diet of predators, the niche breadth, and the trophic overlap level between the populations. Statistical differences in the isotopic values of both predators were observed over the time. The mixing model determined that Galapagos fur seals had a primarily teutophagous diet, whereas the Galapagos sea lions fed exclusively on fish in both regions of the archipelago. The SIBER analysis showed differences in the trophic niche between the two sea lion populations, with the western rookery of the Galapagos sea lion being the population with the largest trophic niche area. A trophic niche partitioning between Galapagos fur seals and Galapagos sea lions in the west of the archipelago is suggested by our results. At intraspecific level, the western population of the Galapagos sea lion (ZwW) showed higher trophic breadth than the eastern population, a strategy adopted by the ZwW to decrease the interspecific competition levels in the western region. Copyright © 2014 John Wiley & Sons, Ltd.

Experimental demonstration of a trophic cascade in the Galápagos rocky subtidal: Effects of consumer identity and behavior.

PubMed

Witman, Jon D; Smith, Franz; Novak, Mark

2017-01-01

In diverse tropical webs, trophic cascades are presumed to be rare, as species interactions may dampen top-down control and reduce their prevalence. To test this hypothesis, we used an open experimental design in the Galápagos rocky subtidal that enabled a diverse guild of fish species, in the presence of each other and top predators (sea lions and sharks), to attack two species of sea urchins grazing on benthic algae. Time-lapse photography of experiments on natural and experimental substrates revealed strong species identity effects: only two predator species-blunthead triggerfish (Pseudobalistes naufragium) and finescale triggerfish (Balistes polylepis)-drove a diurnal trophic cascade extending to algae, and they preferred large pencil urchins (Eucidaris galapagensis) over green urchins (Lytechinus semituberculatus). Triggerfish predation effects were strong, causing a 24-fold reduction of pencil urchin densities during the initial 21 hours of a trophic cascade experiment. A trophic cascade was demonstrated for pencil urchins, but not for green urchins, by significantly higher percent cover of urchin-grazed algae in cages that excluded predatory fish than in predator access (fence) treatments. Pencil urchins were more abundant at night when triggerfish were absent, suggesting that this species persists by exploiting a nocturnal predation refuge. Time-series of pencil urchin survivorship further demonstrated per capita interference effects of hogfish and top predators. These interference effects respectively weakened and extended the trophic cascade to a fourth trophic level through behavioral modifications of the triggerfish-urchin interaction. We conclude that interference behaviors capable of modifying interaction strength warrant greater attention as mechanisms for altering top-down control, particularly in speciose food webs.

Temporal variability (1997-2015) of trophic fish guilds and its relationships with El Niño events in a subtropical estuary

NASA Astrophysics Data System (ADS)

Possamai, Bianca; Vieira, João P.; Grimm, Alice M.; Garcia, Alexandre M.

2018-03-01

Global climatic phenomena like El Niño events are known to alter hydrological cycles and local abiotic conditions leading to changes in structure and dynamics of terrestrial and aquatic biological communities worldwide. Based on a long-term (19 years) standardized sampling of shallow water estuarine fishes, this study investigated the temporal variability in composition and dominance patterns of trophic guilds in a subtropical estuary (Patos Lagoon estuary, Southern Brazil) and their relationship with local and regional driving forces associated with moderate (2002-2003 and 2009-2010) and very strong (1997-1998 and 2015-2016) El Niño events. Fish species were classified into eight trophic guilds (DTV detritivore, HVP herbivore-phytoplankton, HVM macroalgae herbivore, ISV insectivore, OMN omnivore, PSV piscivore, ZBV zoobenthivore and ZPL zooplanktivore) and their abundances were correlated with environmental factors. Canonical correspondence analysis revealed that less dominant (those comprising < 10% of total abundance) trophic guilds, such as HVP, HVM, ISV, PSV, increased their relative abundance in the estuary during higher rainfall and lower salinity conditions associated with moderate and very strong El Niño events. An opposite pattern was observed for the dominant trophic fish guilds like OMN and, at lesser extent, DTV and ZPL, which had greater association with higher values of salinity and water transparency occurring mostly during non-El Niño conditions. In contrast, ZBV's abundance was not correlated with contrasting environmental conditions, but rather, had higher association with samples characterized by intermediate environmental values. Overall, these findings show that moderate and very strong El Niño events did not substantially disrupt the dominance patterns among trophic fish guilds in the estuary. Rather, they increased trophic estuarine diversity by flushing freshwater fishes with distinct feeding habits into the estuary.

Trophic models: What do we learn about Celtic Sea and Bay of Biscay ecosystems?

NASA Astrophysics Data System (ADS)

Moullec, Fabien; Gascuel, Didier; Bentorcha, Karim; Guénette, Sylvie; Robert, Marianne

2017-08-01

Trophic models are key tools to go beyond the single-species approaches used in stock assessments to adopt a more holistic view and implement the Ecosystem Approach to Fisheries Management (EAFM). This study aims to: (i) analyse the trophic functioning of the Celtic Sea and the Bay of Biscay, (ii) investigate ecosystem changes over the 1980-2013 period and, (iii) explore the response to management measures at the food web scale. Ecopath models were built for each ecosystem for years 1980 and 2013, and Ecosim models were fitted to time series data of biomass and catches. EcoTroph diagnosis showed that in both ecosystems, fishing pressure focuses on high trophic levels (TLs) and, to a lesser extent, on intermediate TLs. However, the interplay between local environmental conditions, species composition and ecosystem functioning could explain the different responses to fisheries management observed between these two contiguous ecosystems. Indeed, over the study period, the ecosystem's exploitation status has improved in the Bay of Biscay but not in the Celtic Sea. This improvement does not seem to be sufficient to achieve the objectives of an EAFM, as high trophic levels were still overexploited in 2013 and simulations conducted with Ecosim in the Bay of Biscay indicate that at current fishing effort the biomass will not be rebuilt by 2030. The ecosystem's response to a reduction in fishing mortality depends on which trophic levels receive protection. Reducing fishing mortality on pelagic fish, instead of on demersal fish, appears more efficient at maximising catch and total biomass and at conserving both top-predator and intermediate TLs. Such advice-oriented trophic models should be used on a regular basis to monitor the health status of marine food webs and analyse the trade-offs between multiple objectives in an ecosystem-based fisheries management context.

The Influence of Terrestrial Matter in Marine Food Webs of the Beaufort Sea Shelf and Slope

NASA Astrophysics Data System (ADS)

Bell, L.; Iken, K.; Bluhm, B.

2016-02-01

Forecasted increases in terrestrial organic matter (OMterr) inputs to the Beaufort Sea necessitate a better understanding of the contribution of this organic matter food source to the trophic structure of marine communities. This study investigated the relative ecological importance of OMterr across the Beaufort Sea shelf and slope by examining differences in community trophic structure concurrent with variation in terrestrial versus marine organic matter influence. Interannual variability in organism trophic level was assessed to confirm the persistent impact of these large-scale patterns in food source distribution on marine consumers. Oxygen stable isotope ratios (δ18O) of surface water confirmed the widespread influence of Canada's Mackenzie River plume across the Beaufort Sea. Carbon stable isotope ratios (δ13C values) of pelagic particulate organic matter (pPOM) and marine consumers from locations ranging from 20 to 1000 m bottom depth revealed a strong isotopic imprint of OMterr in the eastern Beaufort Sea, which decreased westward from the Mackenzie River. Food web length, based on the nitrogen stable isotope ratios (δ15N values) of marine consumers, was greater closer to the Mackenzie River outflow both in shelf and slope locations due to relatively higher δ15N values of pelagic and benthic primary consumers. Strong microbial processing of OMterr in the eastern regions of the Beaufort Sea is inferred based on a trophic gap between sources and lower trophic consumers. A large proportion of epifaunal biomass occupying higher trophic levels suggests that OMterr as a basal food source can provide substantial energetic support for higher marine trophic levels. These findings support the concept that terrestrial matter is an important source in the Arctic marine food web, and compel a more specific understanding of energy transfer through the OMterr-associated microbial loop.

Experimental demonstration of a trophic cascade in the Galápagos rocky subtidal: Effects of consumer identity and behavior

PubMed Central

Witman, Jon D.; Smith, Franz; Novak, Mark

2017-01-01

In diverse tropical webs, trophic cascades are presumed to be rare, as species interactions may dampen top-down control and reduce their prevalence. To test this hypothesis, we used an open experimental design in the Galápagos rocky subtidal that enabled a diverse guild of fish species, in the presence of each other and top predators (sea lions and sharks), to attack two species of sea urchins grazing on benthic algae. Time-lapse photography of experiments on natural and experimental substrates revealed strong species identity effects: only two predator species–blunthead triggerfish (Pseudobalistes naufragium) and finescale triggerfish (Balistes polylepis)–drove a diurnal trophic cascade extending to algae, and they preferred large pencil urchins (Eucidaris galapagensis) over green urchins (Lytechinus semituberculatus). Triggerfish predation effects were strong, causing a 24-fold reduction of pencil urchin densities during the initial 21 hours of a trophic cascade experiment. A trophic cascade was demonstrated for pencil urchins, but not for green urchins, by significantly higher percent cover of urchin-grazed algae in cages that excluded predatory fish than in predator access (fence) treatments. Pencil urchins were more abundant at night when triggerfish were absent, suggesting that this species persists by exploiting a nocturnal predation refuge. Time-series of pencil urchin survivorship further demonstrated per capita interference effects of hogfish and top predators. These interference effects respectively weakened and extended the trophic cascade to a fourth trophic level through behavioral modifications of the triggerfish-urchin interaction. We conclude that interference behaviors capable of modifying interaction strength warrant greater attention as mechanisms for altering top-down control, particularly in speciose food webs. PMID:28430794

The dynamics of methane emissions in Alaskan peatlands at different trophic levels

NASA Astrophysics Data System (ADS)

Zhang, L.; Liu, X.; Langford, L.; Chanton, J.; Hines, M. E.

2016-12-01

One major uncertainty in estimating methane (CH4) emission from wetlands is extrapolating from highly heterogeneous and inadequately studied local sites to larger scales. The heterogeneity of peatlands comes from contrasting surface vegetation compositions within short distances that are usually associated with different nutrient sources and trophic status. Different microbial communities and metabolic pathways occur at different trophic levels. Stable isotope C ratios (δ13C) have been used as a robust tool to distinguish methanogenic pathways, but different sources of parent compounds (acetate and CO2) with unique δ13C signatures, and unresolved fractionation factors associated with different methanogens, add complexity. To better understand the relationships between trophic status, surface vegetation compositions and methanogenic pathways, 28 peatland sites were studied in Fairbanks and Anchorage, Alaska in the summer of 2015. These sites were ordinated using multiple factor analysis into 3 clusters based on pH, temp, CH4 and volatile fatty acids production rates, δ13C values, and surface vegetation composition. In the low-pH trophic cluster (pH 4.2), Sphagnum fuscum was the dominant species with specific sedges (Ledum decumbens), and primary fermentation rates was slow with no CH4 detected. In the intermediate trophic level (pH 5.3), in which Sphagnum magellanicum was largely present, both hydrogenotrophic (HM) and acetoclastic methanogenesis (AM) were very active. Syntrophy was present at certain sites, which may provide CO2 and acetate with unique δ13C for CH4 production. At the highest pH trophic cluster examined in this study (pH 5.8), Carex tenuiflora, Carex aquatilis, and Sphagnum Squarrosum dominated. CH4 production rates were higher than those in the intermediate cluster and the apparent fractionation factor a was lower.

Age and trophic position dominate bioaccumulation of mercury and organochlorines in the food web of Lake Washington

USGS Publications Warehouse

McIntyre, J.K.; Beauchamp, D.A.

2007-01-01

Understanding the mechanisms of bioaccumulation in food webs is critical to predicting which food webs are at risk for higher rates of bioaccumulation that endanger the health of upper-trophic predators, including humans. Mercury and organochlorines were measured concurrently with stable isotopes of nitrogen and carbon in key fishes and invertebrates of Lake Washington to explore important pathways of bioaccumulation in this food web. Across the food web, age and trophic position together were highly significant predictors of bioaccumulation. Trophic position was more important than age for predicting accumulation of mercury, ???DDT, and ???-chlordane, whereas age was more important than trophic position for predicting ???PCB. Excluding age from the analysis inflated the apparent importance of trophic position to bioaccumulation for all contaminants. Benthic and pelagic habitats had similar potential to bioaccumulate contaminants, although higher ???-chlordane concentrations in organisms were weakly associated with more benthic carbon signals. In individual fish species, contaminant concentrations increased with age, size, and trophic position (??15N), whereas relationships with carbon source (??13C) were not consistent. Lipid concentrations were correlated with contaminant concentrations in some but not all fishes, suggesting that lipids were not involved mechanistically in bioaccumulation. Contaminant concentrations in biota did not vary among littoral sites. Collectively, these results suggest that age may be an important determinant of bioaccumulation in many food webs and could help explain a significant amount of the variability in apparent biomagnification rates among food webs. As such, effort should be made when possible to collect information on organism age in addition to stable isotopes when assessing food webs for rates of biomagnification. ?? 2006 Elsevier B.V. All rights reserved.

Stable C and N isotopic composition of cold-water corals from the Newfoundland and Labrador continental slope: Examination of trophic, depth and spatial effects

NASA Astrophysics Data System (ADS)

Sherwood, Owen A.; Jamieson, Robyn E.; Edinger, Evan N.; Wareham, Vonda E.

2008-10-01

With the aim of understanding of the trophic ecology of cold-water corals, this paper explores the tissue δ13C and δ15N values of 11 'coral' species (8 alcyonacean, 1 antipatharian, 1 pennatulacean, 1 scleractinian) collected along the Newfoundland and Labrador continental slope. Isotopic results delimit species along continua of trophic level and food lability. With an isotopic signature similar to macrozooplankton, Paragorgia arborea occupies the lowest trophic level and most likely feeds on fresh phytodetritus. Primnoa resedaeformis occupies a slightly higher trophic level, likely supplementing its diet with microzooplankton. Bathypathes arctica, Pennatulacea and other alcyonaceans ( Acanella arbuscula, Acanthogorgia armata, Anthomastus grandiflorus, Duva florida, Keratoisis ornata, Paramuricea sp.) had higher δ13C and δ15N values, suggesting these species feed at higher trophic levels and on a greater proportion of more degraded POM. Flabellum alabastrum had an isotopic signature similar to that of snow crab, indicating a primarily carnivorous diet. Isotopic composition did not vary significantly over a depth gradient of 50-1400 m. Coral δ13C increased slightly (<1‰) from the Hudson Strait to the southern Grand Banks, but δ15N did not. By modulating the availability and quality of suspended foods, substrate likely exerts a primary influence on the feeding habits of cold-water corals.

From neurons to epidemics: How trophic coherence affects spreading processes.

PubMed

Klaise, Janis; Johnson, Samuel

2016-06-01

Trophic coherence, a measure of the extent to which the nodes of a directed network are organised in levels, has recently been shown to be closely related to many structural and dynamical aspects of complex systems, including graph eigenspectra, the prevalence or absence of feedback cycles, and linear stability. Furthermore, non-trivial trophic structures have been observed in networks of neurons, species, genes, metabolites, cellular signalling, concatenated words, P2P users, and world trade. Here, we consider two simple yet apparently quite different dynamical models-one a susceptible-infected-susceptible epidemic model adapted to include complex contagion and the other an Amari-Hopfield neural network-and show that in both cases the related spreading processes are modulated in similar ways by the trophic coherence of the underlying networks. To do this, we propose a network assembly model which can generate structures with tunable trophic coherence, limiting in either perfectly stratified networks or random graphs. We find that trophic coherence can exert a qualitative change in spreading behaviour, determining whether a pulse of activity will percolate through the entire network or remain confined to a subset of nodes, and whether such activity will quickly die out or endure indefinitely. These results could be important for our understanding of phenomena such as epidemics, rumours, shocks to ecosystems, neuronal avalanches, and many other spreading processes.

Worker reproduction of the invasive yellow crazy ant Anoplolepis gracilipes.

PubMed

Lee, Ching-Chen; Nakao, Hirotaka; Tseng, Shu-Ping; Hsu, Hung-Wei; Lin, Gwo-Li; Tay, Jia-Wei; Billen, Johan; Ito, Fuminori; Lee, Chow-Yang; Lin, Chung-Chi; Yang, Chin-Cheng Scotty

2017-01-01

Reproductive division of labor is one of the key features of social insects. Queens are adapted for reproduction while workers are adapted for foraging and colony maintenance. In many species, however, workers retain functional ovaries and can lay unfertilized male eggs or trophic eggs. Here we report for the first time on the occurrence of physogastric workers and apparent worker reproduction in the invasive yellow crazy ant Anoplolepis gracilipes (Fr. Smith). We further examined the reproductive potential and nutritional role of physogastric workers through multidisciplinary approaches including morphological characterization, laboratory manipulation, genetic analysis and behavioral observation. Egg production with two types of eggs, namely reproductive and trophic eggs, by physogastric workers was found. The reproductive egg was confirmed to be haploid and male-destined, suggesting that the workers produced males via arrhenotokous parthenogenesis as no spermatheca was discovered. Detailed observations suggested that larvae were mainly fed with trophic eggs. Along with consumption of trophic eggs by queens and other castes as part of their diet, the vital role of physogastric workers as "trophic specialist" is confirmed. We propose that adaptive advantages derived from worker reproduction for A. gracilipes may include 1) trophic eggs provisioned by physogastric workers likely assist colonies of A. gracilipes in overcoming unfavorable conditions such as paucity of food during critical founding stage; 2) worker-produced males are fertile and thus might offer an inclusive fitness advantage for the doomed orphaned colony.

Determining the trophic guilds of fishes and macroinvertebrates in a seagrass food web

USGS Publications Warehouse

Luczkovich, J.J.; Ward, G.P.; Johnson, J.C.; Christian, R.R.; Baird, D.; Neckles, H.; Rizzo, W.M.

2002-01-01

We established trophic guilds of macroinvertebrate and fish taxa using correspondence analysis and a hierarchical clustering strategy for a seagrass food web in winter in the northeastern Gulf of Mexico. To create the diet matrix, we characterized the trophic linkages of macroinvertebrate and fish taxa. present in Hatodule wrightii seagrass habitat areas within the St. Marks National Wildlife Refuge (Florida) using binary data, combining dietary links obtained from relevant literature for macroinvertebrates with stomach analysis of common fishes collected during January and February of 1994. Heirarchical average-linkage cluster analysis of the 73 taxa of fishes and macroinvertebrates in the diet matrix yielded 14 clusters with diet similarity greater than or equal to 0.60. We then used correspondence analysis with three factors to jointly plot the coordinates of the consumers (identified by cluster membership) and of the 33 food sources. Correspondence analysis served as a visualization tool for assigning each taxon to one of eight trophic guilds: herbivores, detritivores, suspension feeders, omnivores, molluscivores, meiobenthos consumers, macrobenthos consumers, and piscivores. These trophic groups, cross-classified with major taxonomic groups, were further used to develop consumer compartments in a network analysis model of carbon flow in this seagrass ecosystem. The method presented here should greatly improve the development of future network models of food webs by providing an objective procedure for aggregating trophic groups.

Internal distribution of Cd in lettuce and resulting effects on Cd trophic transfer to the snail: Achatina fulica.

PubMed

Li, Cheng-Cheng; Dang, Fei; Cang, Long; Zhou, Dong-Mei; Peijnenburg, Willie J G M

2015-09-01

The mechanisms underlying Cd trophic transfer along the soil-lettuce-snail food chain were investigated. The fate of Cd within cells, revealed by assessment of Cd chemical forms and of subcellular partitioning, differed between the two examined lettuce species that we examined (L. longifolia and L. crispa). The species-specific internal Cd fate not only influenced Cd burdens in lettuce, with higher Cd levels in L. crispa, but also affected Cd transfer efficiency to the consumer snail (Achatina fulica). Especially, the incorporation of Cd chemical forms (Cd in the inorganic, water-soluble and pectates and protein-integrated forms) in lettuce could best explain Cd trophic transfer, when compared to dietary Cd levels alone and/or subcellular Cd partitioning. Trophically available metal on the subcellular partitioning base failed to shed light on Cd transfer in this study. After 28-d of exposure, most Cd was trapped in the viscera of Achatina fulica, and cadmium bio-magnification was noted in the snails, as the transfer factor of lettuce-to-snail soft tissue was larger than one. This study provides a first step to apply a chemical speciation approach to dictate the trophic bioavailability of Cd through the soil-plant-snail system, which might be an important pre-requisite for mechanistic understanding of metal trophic transfer. Copyright © 2015 Elsevier Ltd. All rights reserved.

Trophic discrimination factors of stable carbon and nitrogen isotopes in hair of corn fed wild boar.

PubMed

Holá, Michaela; Ježek, Miloš; Kušta, Tomáš; Košatová, Michaela

2015-01-01

Stable isotope measurements are increasingly being used to gain insights into the nutritional ecology of many wildlife species and their role in ecosystem structure and function. Such studies require estimations of trophic discrimination factors (i.e. differences in the isotopic ratio between the consumer and its diet). Although trophic discrimination factors are tissue- and species-specific, researchers often rely on generalized, and fixed trophic discrimination factors that have not been experimentally derived. In this experimental study, captive wild boar (Sus scrofa) were fed a controlled diet of corn (Zea mays), a popular and increasingly dominant food source for wild boar in the Czech Republic and elsewhere in Europe, and trophic discrimination factors for stable carbon (Δ13C) and nitrogen (Δ15N) isotopes were determined from hair samples. The mean Δ13C and Δ15N in wild boar hair were -2.3‰ and +3.5‰, respectively. Also, in order to facilitate future derivations of isotopic measurements along wild boar hair, we calculated the average hair growth rate to be 1.1 mm d(-1). Our results serve as a baseline for interpreting isotopic patterns of free-ranging wild boar in current European agricultural landscapes. However, future research is needed in order to provide a broader understanding of the processes underlying the variation in trophic discrimination factors of carbon and nitrogen across of variety of diet types.

From neurons to epidemics: How trophic coherence affects spreading processes

NASA Astrophysics Data System (ADS)

Klaise, Janis; Johnson, Samuel

2016-06-01

Trophic coherence, a measure of the extent to which the nodes of a directed network are organised in levels, has recently been shown to be closely related to many structural and dynamical aspects of complex systems, including graph eigenspectra, the prevalence or absence of feedback cycles, and linear stability. Furthermore, non-trivial trophic structures have been observed in networks of neurons, species, genes, metabolites, cellular signalling, concatenated words, P2P users, and world trade. Here, we consider two simple yet apparently quite different dynamical models—one a susceptible-infected-susceptible epidemic model adapted to include complex contagion and the other an Amari-Hopfield neural network—and show that in both cases the related spreading processes are modulated in similar ways by the trophic coherence of the underlying networks. To do this, we propose a network assembly model which can generate structures with tunable trophic coherence, limiting in either perfectly stratified networks or random graphs. We find that trophic coherence can exert a qualitative change in spreading behaviour, determining whether a pulse of activity will percolate through the entire network or remain confined to a subset of nodes, and whether such activity will quickly die out or endure indefinitely. These results could be important for our understanding of phenomena such as epidemics, rumours, shocks to ecosystems, neuronal avalanches, and many other spreading processes.

Mesoscale Eddies Are Oases for Higher Trophic Marine Life

PubMed Central

Godø, Olav R.; Samuelsen, Annette; Macaulay, Gavin J.; Patel, Ruben; Hjøllo, Solfrid Sætre; Horne, John; Kaartvedt, Stein; Johannessen, Johnny A.

2012-01-01

Mesoscale eddies stimulate biological production in the ocean, but knowledge of energy transfers to higher trophic levels within eddies remains fragmented and not quantified. Increasing the knowledge base is constrained by the inability of traditional sampling methods to adequately sample biological processes at the spatio-temporal scales at which they occur. By combining satellite and acoustic observations over spatial scales of 10 s of km horizontally and 100 s of m vertically, supported by hydrographical and biological sampling we show that anticyclonic eddies shape distribution and density of marine life from the surface to bathyal depths. Fish feed along density structures of eddies, demonstrating that eddies catalyze energy transfer across trophic levels. Eddies create attractive pelagic habitats, analogous to oases in the desert, for higher trophic level aquatic organisms through enhanced 3-D motion that accumulates and redistributes biomass, contributing to overall bioproduction in the ocean. Integrating multidisciplinary observation methodologies promoted a new understanding of biophysical interaction in mesoscale eddies. Our findings emphasize the impact of eddies on the patchiness of biomass in the sea and demonstrate that they provide rich feeding habitat for higher trophic marine life. PMID:22272294

The interacting effects of temperature and food chain length on trophic abundance and ecosystem function.

PubMed

Beveridge, Oliver S; Humphries, Stuart; Petchey, Owen L

2010-05-01

1. While much is known about the independent effects of trophic structure and temperature on density and ecosystem processes, less is known about the interaction(s) between the two. 2. We manipulated the temperature of laboratory-based bacteria-protist communities that contained communities with one, two, or three trophic levels, and recorded species' densities and bacterial decomposition. 3. Temperature, food chain length and their interaction produced significant responses in microbial density and bacterial decomposition. Prey and resource density expressed different patterns of temperature dependency during different phases of population dynamics. The addition of a predator altered the temperature-density relationship of prey, from a unimodal trend to a negative one. Bacterial decomposition was greatest in the presence of consumers at higher temperatures. 4. These results are qualitatively consistent with a recent model of direct and indirect temperature effects on resource-consumer population dynamics. Results highlight and reinforce the importance of indirect effects of temperature mediated through trophic interactions. Understanding and predicting the consequences of environmental change will require that indirect effects, trophic structure, and individual species' tolerances be incorporated into theory and models.

A 200-year perspective on alternative stable state theory and lake management from a biomanipulated shallow lake.

PubMed

Hobbs, William O; Hobbs, Joy M Ramstack; LaFrançois, Toben; Zimmer, Kyle D; Theissen, Kevin M; Edlund, Mark B; Michelutti, Neal; Butler, Malcolm G; Hanson, Mark A; Carlson, Thomas J

2012-07-01

Multiple stressors to a shallow lake ecosystem have the ability to control the relative stability of alternative states (clear, macrophyte-dominated or turbid, algal-dominated). As a consequence, the use of remedial biomanipulations to induce trophic cascades and shift a turbid lake to a clear state is often only a temporary solution. Here we show the instability of short-term manipulations in the shallow Lake Christina (Minnesota, USA) is governed by the long-term state following a regime shift in the lake. During the modern, managed period of the lake, three top-down manipulations (fish kills) were undertaken inducing temporary (5-10 years) unstable clear-water states. Paleoecological remains of diatoms, along with proxies of primary production (total chlorophyll a and total organic carbon accumulation rate) and trophic state (total P) from sediment records clearly show a single regime shift in the lake during the early 1950s; following this shift, the functioning of the lake ecosystem is dominated by a persistent turbid state. We find that multiple stressors contributed to the regime shift. First, the lake began to eutrophy (from agricultural land use and/or increased waterfowl populations), leading to a dramatic increase in primary production. Soon after, the construction of a dam in 1936 effectively doubled the depth of the lake, compounded by increases in regional humidity; this resulted in an increase in planktivorous and benthivorous fish reducing phytoplankton grazers. These factors further conspired to increase the stability of a turbid regime during the modern managed period, such that switches to a clear-water state were inherently unstable and the lake consistently returned to a turbid state. We conclude that while top-down manipulations have had measurable impacts on the lake state, they have not been effective in providing a return to an ecosystem similar to the stable historical period. Our work offers an example of a well-studied ecosystem forced by multiple stressors into a new long-term managed period, where manipulated clear-water states are temporary, managed features.

Evolutionary trade-offs in plants mediate the strength of trophic cascades.

PubMed

Mooney, Kailen A; Halitschke, Rayko; Kessler, Andre; Agrawal, Anurag A

2010-03-26

Predators determine herbivore and plant biomass via so-called trophic cascades, and the strength of such effects is influenced by ecosystem productivity. To determine whether evolutionary trade-offs among plant traits influence patterns of trophic control, we manipulated predators and soil fertility and measured impacts of a major herbivore (the aphid Aphis nerii) on 16 milkweed species (Asclepias spp.) in a phylogenetic field experiment. Herbivore density was determined by variation in predation and trade-offs between herbivore resistance and plant growth strategy. Neither herbivore density nor predator effects on herbivores predicted the cascading effects of predators on plant biomass. Instead, cascade strength was strongly and positively associated with milkweed response to soil fertility. Accordingly, contemporary patterns of trophic control are driven by evolutionary convergent trade-offs faced by plants.

Ecological dynamics across the Arctic associated with recent climate change.

PubMed

Post, Eric; Forchhammer, Mads C; Bret-Harte, M Syndonia; Callaghan, Terry V; Christensen, Torben R; Elberling, Bo; Fox, Anthony D; Gilg, Olivier; Hik, David S; Høye, Toke T; Ims, Rolf A; Jeppesen, Erik; Klein, David R; Madsen, Jesper; McGuire, A David; Rysgaard, Søren; Schindler, Daniel E; Stirling, Ian; Tamstorf, Mikkel P; Tyler, Nicholas J C; van der Wal, Rene; Welker, Jeffrey; Wookey, Philip A; Schmidt, Niels Martin; Aastrup, Peter

2009-09-11

At the close of the Fourth International Polar Year, we take stock of the ecological consequences of recent climate change in the Arctic, focusing on effects at population, community, and ecosystem scales. Despite the buffering effect of landscape heterogeneity, Arctic ecosystems and the trophic relationships that structure them have been severely perturbed. These rapid changes may be a bellwether of changes to come at lower latitudes and have the potential to affect ecosystem services related to natural resources, food production, climate regulation, and cultural integrity. We highlight areas of ecological research that deserve priority as the Arctic continues to warm.

[Mechanism of population density compensation in island bumblebee taxocenoses (Hymenoptera, Apidae, Bombus) and the notion of reserve compensatory species].

PubMed

Bolotov, I N; Kolosova, Iu S; Podbolotskaia, M V; Potapov, G S; Grishchenko, I V

2013-01-01

The notion of a dynamic compensatory system is discussed, characterized by the alternation of species occupying the leading position in bumblebee taxocenoses, while the total density of these pollinators in island ecosystems remains at similar levels. The functioning of the compensatory system is regulated by both abiotic factors (the weather and climate) and biotic factors (competition for trophic resources). The stability of the system is determined by the presence of reserve compensatory species capable of rapid population growth against the background of depressed abundance of other species under changing environmental conditions.

Consequences of omnivory for trophic interactions on a salt marsh shrub.

PubMed

Ho, Chuan-Kai; Pennings, Steven C

2008-06-01

Although omnivory is common in nature, its impact on trophic interactions is variable. Predicting the food web consequences of omnivory is complicated because omnivores can simultaneously produce conflicting direct and indirect effects on the same species or trophic level. We conducted field and laboratory experiments testing the top-down impacts of an omnivorous salt marsh crab, Armases cinereum, on the shrub Iva frutescens and its herbivorous and predatory arthropod fauna. Armases is a "true omnivore," consuming both Iva and arthropods living on Iva. We hypothesized that Armases would benefit Iva through a top-down trophic cascade, and that this benefit would be stronger than the direct negative effect of Armases on Iva. A field experiment on Sapelo Island, Georgia (USA), supported this hypothesis. Although Armases suppressed predators (spiders), it also suppressed herbivores (aphids), and benefited Iva, increasing leaf number, and reducing the proportion of dead shoots. A one-month laboratory experiment, focusing on the most common species in the food web, also supported this hypothesis. Armases strongly suppressed aphids and consumed fewer Iva leaves if aphids were available as an alternate diet. Armases gained more body mass if they could feed on aphids as well as on Iva. Although Armases had a negative effect on Iva when aphids were not present, Armases benefited Iva if aphids were present, because Armases controlled aphid populations, releasing Iva from herbivory. Although Armases is an omnivore, it produced strong top-down forces and a trophic cascade because it fed preferentially on herbivores rather than plants when both were available. At the same time, the ability of Armases to subsist on a plant diet allows it to persist in the food web when animal food is not available. Because omnivores feed on multiple trophic levels, their effects on food webs may differ from those predicted by standard trophic models that assume that each species feeds only on a single trophic level. To better understand the complexity of real food webs, the variable feeding habits and feeding preferences of different omnivorous species must be taken into consideration.

P2 receptors in cardiovascular regulation and disease

PubMed Central

Erlinge, David

2007-01-01

The role of ATP as an extracellular signalling molecule is now well established and evidence is accumulating that ATP and other nucleotides (ADP, UTP and UDP) play important roles in cardiovascular physiology and pathophysiology, acting via P2X (ion channel) and P2Y (G protein-coupled) receptors. In this article we consider the dual role of ATP in regulation of vascular tone, released as a cotransmitter from sympathetic nerves or released in the vascular lumen in response to changes in blood flow and hypoxia. Further, purinergic long-term trophic and inflammatory signalling is described in cell proliferation, differentiation, migration and death in angiogenesis, vascular remodelling, restenosis and atherosclerosis. The effects on haemostasis and cardiac regulation is reviewed. The involvement of ATP in vascular diseases such as thrombosis, hypertension and diabetes will also be discussed, as well as various heart conditions. The purinergic system may be of similar importance as the sympathetic and renin-angiotensin-aldosterone systems in cardiovascular regulation and pathophysiology. The extracellular nucleotides and their cardiovascular P2 receptors are now entering the phase of clinical development. PMID:18368530

Coccolithophore responses to environmental variability in the South China Sea: species composition and calcite content

NASA Astrophysics Data System (ADS)

Jin, Xiaobo; Liu, Chuanlian; Poulton, Alex J.; Dai, Minhan; Guo, Xianghui

2016-08-01

Coccolithophore contributions to the global marine carbon cycle are regulated by the calcite content of their scales (coccoliths) and the relative cellular levels of photosynthesis and calcification rates. All three of these factors vary between coccolithophore species and with response to the growth environment. Here, water samples were collected in the northern basin of the South China Sea (SCS) during summer 2014 in order to examine how environmental variability influenced species composition and cellular levels of calcite content. Average coccolithophore abundance and their calcite concentration in the water column were 11.82 cells mL-1 and 1508.3 pg C mL-1, respectively, during the cruise. Water samples can be divided into three floral groups according to their distinct coccolithophore communities. The vertical structure of the coccolithophore community in the water column was controlled by the trophic conditions, which were regulated by mesoscale eddies across the SCS basin. The evaluation of coccolithophore-based calcite in the surface ocean also showed that three key species in the SCS (Emiliania huxleyi, Gephyrocapsa oceanica, Florisphaera profunda) and other larger, numerically rare species made almost equal contributions to total coccolith-based calcite in the water column. For Emiliania huxleyi biometry measurements, coccolith size positively correlated with nutrients (nitrate, phosphate), and it is suggested that coccolith length is influenced by light and nutrients through the regulation of growth rates. Larger-sized coccoliths were also linked statistically to low pH and calcite saturation states; however, it is not a simple cause and effect relationship, as carbonate chemistry was strongly co-correlated with the other key environmental factors (nutrients, light).

Optimal defense strategies in an idealized microbial food web under trade-off between competition and defense.

PubMed

Våge, Selina; Storesund, Julia E; Giske, Jarl; Thingstad, T Frede

2014-01-01

Trophic mechanisms that can generate biodiversity in food webs include bottom-up (growth rate regulating) and top-down (biomass regulating) factors. The top-down control has traditionally been analyzed using the concepts of "Keystone Predation" (KP) and "Killing-the-Winner" (KtW), predominately occuring in discussions of macro- and micro-biological ecology, respectively. Here we combine the classical diamond-shaped food web structure frequently discussed in KP analyses and the KtW concept by introducing a defense strategist capable of partial defense. A formalized description of a trade-off between the defense-strategist's competitive and defensive ability is included. The analysis reveals a complex topology of the steady state solution with strong relationships between food web structure and the combination of trade-off, defense strategy and the system's nutrient content. Among the results is a difference in defense strategies corresponding to maximum biomass, production, or net growth rate of invading individuals. The analysis thus summons awareness that biomass or production, parameters typically measured in field studies to infer success of particular biota, are not directly acted upon by natural selection. Under coexistence with a competition specialist, a balance of competitive and defensive ability of the defense strategist was found to be evolutionarily stable, whereas stronger defense was optimal under increased nutrient levels in the absence of the pure competition specialist. The findings of success of different defense strategies are discussed with respect to SAR11, a highly successful bacterial clade in the pelagic ocean.

Anti-B-Cell Therapies in Autoimmune Neurological Diseases: Rationale and Efficacy Trials.

PubMed

Alexopoulos, Harry; Biba, Angie; Dalakas, Marinos C

2016-01-01

B cells have an ever-increasing role in the etiopathology of a number of autoimmune neurological disorders, acting as antibody-producing cells and, most importantly, as sensors, coordinators, and regulators of the immune response. B cells, among other functions, regulate the T-cell activation process through their participation in antigen presentation and production of cytokines. The availability of monoclonal antibodies or fusion proteins against B-cell surface molecules or B-cell trophic factors bestows a rational approach for treating autoimmune neurological disorders, even when T cells are the main effector cells. This review summarizes basic aspects of B-cell biology, discusses the role(s) of B cells in neurological autoimmunity, and presents anti-B-cell drugs that are either currently on the market or are expected to be available in the near future for treating neurological autoimmune disorders.

Uncovering trophic positions and food resources of soil animals using bulk natural stable isotope composition.

PubMed

Potapov, Anton M; Tiunov, Alexei V; Scheu, Stefan

2018-06-19

Despite the major importance of soil biota in nutrient and energy fluxes, interactions in soil food webs are poorly understood. Here we provide an overview of recent advances in uncovering the trophic structure of soil food webs using natural variations in stable isotope ratios. We discuss approaches of application, normalization and interpretation of stable isotope ratios along with methodological pitfalls. Analysis of published data from temperate forest ecosystems is used to outline emerging concepts and perspectives in soil food web research. In contrast to aboveground and aquatic food webs, trophic fractionation at the basal level of detrital food webs is large for carbon and small for nitrogen stable isotopes. Virtually all soil animals are enriched in 13 C as compared to plant litter. This 'detrital shift' likely reflects preferential uptake of 13 C-enriched microbial biomass and underlines the importance of microorganisms, in contrast to dead plant material, as a major food resource for the soil animal community. Soil organic matter is enriched in 15 N and 13 C relative to leaf litter. Decomposers inhabiting mineral soil layers therefore might be enriched in 15 N resulting in overlap in isotope ratios between soil-dwelling detritivores and litter-dwelling predators. By contrast, 13 C content varies little between detritivores in upper litter and in mineral soil, suggesting that they rely on similar basal resources, i.e. little decomposed organic matter. Comparing vertical isotope gradients in animals and in basal resources can be a valuable tool to assess trophic interactions and dynamics of organic matter in soil. As indicated by stable isotope composition, direct feeding on living plant material as well as on mycorrhizal fungi is likely rare among soil invertebrates. Plant carbon is taken up predominantly by saprotrophic microorganisms and channelled to higher trophic levels of the soil food web. However, feeding on photoautotrophic microorganisms and non-vascular plants may play an important role in fuelling soil food webs. The trophic niche of most high-rank animal taxa spans at least two trophic levels, implying the use of a wide range of resources. Therefore, to identify trophic species and links in food webs, low-rank taxonomic identification is required. Despite overlap in feeding strategies, stable isotope composition of the high-rank taxonomic groups reflects differences in trophic level and in the use of basal resources. Different taxonomic groups of predators and decomposers are likely linked to different pools of organic matter in soil, suggesting different functional roles and indicating that trophic niches in soil animal communities are phylogenetically structured. During last two decades studies using stable isotope analysis have elucidated the trophic structure of soil communities, clarified basal food resources of the soil food web and revealed links between above- and belowground ecosystem compartments. Extending the use of stable isotope analysis to a wider range of soil-dwelling organisms, including microfauna, and a larger array of ecosystems provides the perspective of a comprehensive understanding of the structure and functioning of soil food webs. © 2018 Cambridge Philosophical Society.

Comparison of Coral Reef Ecosystems along a Fishing Pressure Gradient

PubMed Central

Weijerman, Mariska; Fulton, Elizabeth A.; Parrish, Frank A.

2013-01-01

Three trophic mass-balance models representing coral reef ecosystems along a fishery gradient were compared to evaluate ecosystem effects of fishing. The majority of the biomass estimates came directly from a large-scale visual survey program; therefore, data were collected in the same way for all three models, enhancing comparability. Model outputs–such as net system production, size structure of the community, total throughput, production, consumption, production-to-respiration ratio, and Finn’s cycling index and mean path length–indicate that the systems around the unpopulated French Frigate Shoals and along the relatively lightly populated Kona Coast of Hawai’i Island are mature, stable systems with a high efficiency in recycling of biomass. In contrast, model results show that the reef system around the most populated island in the State of Hawai’i, O’ahu, is in a transitional state with reduced ecosystem resilience and appears to be shifting to an algal-dominated system. Evaluation of the candidate indicators for fishing pressure showed that indicators at the community level (e.g., total biomass, community size structure, trophic level of the community) were most robust (i.e., showed the clearest trend) and that multiple indicators are necessary to identify fishing perturbations. These indicators could be used as performance indicators when compared to a baseline for management purposes. This study shows that ecosystem models can be valuable tools in identification of the system state in terms of complexity, stability, and resilience and, therefore, can complement biological metrics currently used by monitoring programs as indicators for coral reef status. Moreover, ecosystem models can improve our understanding of a system’s internal structure that can be used to support management in identification of approaches to reverse unfavorable states. PMID:23737951

Diets and trophic guilds of small fishes from coastal marine habitats in western Taiwan.

PubMed

Egan, J P; Chew, U-S; Kuo, C-H; Villarroel-Diaz, V; Hundt, P J; Iwinski, N G; Hammer, M P; Simons, A M

2017-07-01

The diets and trophic guilds of small fishes were examined along marine sandy beaches and in estuaries at depths <1·5 m in western Taiwan, Republic of China. Copepods were the most frequently identified item in fish guts, indicating they are key prey for the fish assemblages studied. Piscivore, crustacivore, detritivore, omnivore, zooplanktivore and terrestrial invertivore trophic guilds were identified. The zooplanktivore guild contained the most fish species. Maximum prey size consumption was positively correlated with standard length (L S ) in seven species and at the assemblage level and negatively correlated with L S in a single detritivorous species. The diet data and trophic guild scheme produced by this study contribute to an understanding of coastal marine food webs and can inform ecosystem-based fisheries management. © 2017 The Fisheries Society of the British Isles.

Trophic ecology of sea urchins in coral-rocky reef systems, Ecuador

PubMed Central

Loor-Andrade, Peggy; Rodríguez-Barreras, Ruber; Cortés, Jorge

2016-01-01

Sea urchins are important grazers and influence reef development in the Eastern Tropical Pacific (ETP). Diadema mexicanum and Eucidaris thouarsii are the most important sea urchins on the Ecuadorian coastal reefs. This study provided a trophic scenario for these two species of echinoids in the coral-rocky reef bottoms of the Ecuadorian coast, using stable isotopes. We evaluated the relative proportion of algal resources assimilated, and trophic niche of the two sea urchins in the most southern coral-rocky reefs of the ETP in two sites with different disturbance level. Bayesian models were used to estimate the contribution of algal sources, niche breadth, and trophic overlap between the two species. The sea urchins behaved as opportunistic feeders, although they showed differential resource assimilation. Eucidaris thouarsii is the dominant species in disturbed environments; likewise, their niche amplitude was broader than that of D. mexicanum when conditions were not optimal. However, there was no niche overlap between the species. The Stable Isotope Analysis in R (SIAR) indicated that both sea urchins shared limiting resources in the disturbed area, mainly Dictyota spp. (contributions of up to 85% for D. mexicanum and up to 75% for E. thouarsii). The Stable Isotope Bayesian Ellipses in R (SIBER) analysis results indicated less interspecific competition in the undisturbed site. Our results suggested a trophic niche partitioning between sympatric sea urchin species in coastal areas of the ETP, but the limitation of resources could lead to trophic overlap and stronger habitat degradation. PMID:26839748

Food Web Topology in High Mountain Lakes

PubMed Central

Sánchez-Hernández, Javier; Cobo, Fernando; Amundsen, Per-Arne

2015-01-01

Although diversity and limnology of alpine lake systems are well studied, their food web structure and properties have rarely been addressed. Here, the topological food webs of three high mountain lakes in Central Spain were examined. We first addressed the pelagic networks of the lakes, and then we explored how food web topology changed when benthic biota was included to establish complete trophic networks. We conducted a literature search to compare our alpine lacustrine food webs and their structural metrics with those of 18 published lentic webs using a meta-analytic approach. The comparison revealed that the food webs in alpine lakes are relatively simple, in terms of structural network properties (linkage density and connectance), in comparison with lowland lakes, but no great differences were found among pelagic networks. The studied high mountain food webs were dominated by a high proportion of omnivores and species at intermediate trophic levels. Omnivores can exploit resources at multiple trophic levels, and this characteristic might reduce competition among interacting species. Accordingly, the trophic overlap, measured as trophic similarity, was very low in all three systems. Thus, these alpine networks are characterized by many omnivorous consumers with numerous prey species and few consumers with a single or few prey and with low competitive interactions among species. The present study emphasizes the ecological significance of omnivores in high mountain lakes as promoters of network stability and as central players in energy flow pathways via food partitioning and enabling energy mobility among trophic levels. PMID:26571235

Use of Shark Dental Protein to Estimate Trophic Position via Amino Acid Compound-Specific Isotope Analysis

NASA Astrophysics Data System (ADS)

Hayes, M.; Herbert, G.; Ellis, G.

2017-12-01

The diets of apex predators such as sharks are expected to change in response to overfishing of their mesopredator prey, but pre-anthropogenic baselines necessary to test for such changes are lacking. Stable isotope analysis (SIA) of soft tissues is commonly used to study diets in animals based on the bioaccumulation of heavier isotopes of carbon and nitrogen with increasing trophic level. In specimens representing pre-anthropogenic baselines, however, a modified SIA approach is needed to deal with taphonomic challenges, such as loss of soft tissues or selective loss of less stable amino acids (AAs) in other sources of organic compounds (e.g., teeth or bone) which can alter bulk isotope values. These challenges can be overcome with a compound-specific isotope analysis of individual AAs (AA-CSIA), but this first requires a thorough understanding of trophic enrichment factors for individual AAs within biomineralized tissues. In this study, we compare dental and muscle proteins of individual sharks via AA-CSIA to determine how trophic position is recorded within teeth and whether that information differs from that obtained from soft tissues. If skeletal organics reliably record information about shark ecology, then archaeological and perhaps paleontological specimens can be used to investigate pre-anthropogenic ecosystems. Preliminary experiments show that the commonly used glutamic acid/phenylalanine AA pairing may not be useful for establishing trophic position from dental proteins, but that estimated trophic position determined from alternate AA pairs are comparable to those from muscle tissue within the same species.

Trophic Discrimination Factors of Stable Carbon and Nitrogen Isotopes in Hair of Corn Fed Wild Boar

PubMed Central

Holá, Michaela; Ježek, Miloš; Kušta, Tomáš; Košatová, Michaela

2015-01-01

Stable isotope measurements are increasingly being used to gain insights into the nutritional ecology of many wildlife species and their role in ecosystem structure and function. Such studies require estimations of trophic discrimination factors (i.e. differences in the isotopic ratio between the consumer and its diet). Although trophic discrimination factors are tissue- and species- specific, researchers often rely on generalized, and fixed trophic discrimination factors that have not been experimentally derived. In this experimental study, captive wild boar (Sus scrofa) were fed a controlled diet of corn (Zea mays), a popular and increasingly dominant food source for wild boar in the Czech Republic and elsewhere in Europe, and trophic discrimination factors for stable carbon (Δ13C) and nitrogen (Δ15N) isotopes were determined from hair samples. The mean Δ13C and Δ15N in wild boar hair were –2.3 ‰ and +3.5 ‰, respectively. Also, in order to facilitate future derivations of isotopic measurements along wild boar hair, we calculated the average hair growth rate to be 1.1 mm d-1. Our results serve as a baseline for interpreting isotopic patterns of free-ranging wild boar in current European agricultural landscapes. However, future research is needed in order to provide a broader understanding of the processes underlying the variation in trophic discrimination factors of carbon and nitrogen across of variety of diet types. PMID:25915400

Food Web Topology in High Mountain Lakes.

PubMed

Sánchez-Hernández, Javier; Cobo, Fernando; Amundsen, Per-Arne

2015-01-01

Although diversity and limnology of alpine lake systems are well studied, their food web structure and properties have rarely been addressed. Here, the topological food webs of three high mountain lakes in Central Spain were examined. We first addressed the pelagic networks of the lakes, and then we explored how food web topology changed when benthic biota was included to establish complete trophic networks. We conducted a literature search to compare our alpine lacustrine food webs and their structural metrics with those of 18 published lentic webs using a meta-analytic approach. The comparison revealed that the food webs in alpine lakes are relatively simple, in terms of structural network properties (linkage density and connectance), in comparison with lowland lakes, but no great differences were found among pelagic networks. The studied high mountain food webs were dominated by a high proportion of omnivores and species at intermediate trophic levels. Omnivores can exploit resources at multiple trophic levels, and this characteristic might reduce competition among interacting species. Accordingly, the trophic overlap, measured as trophic similarity, was very low in all three systems. Thus, these alpine networks are characterized by many omnivorous consumers with numerous prey species and few consumers with a single or few prey and with low competitive interactions among species. The present study emphasizes the ecological significance of omnivores in high mountain lakes as promoters of network stability and as central players in energy flow pathways via food partitioning and enabling energy mobility among trophic levels.

Protection by GDNF and other trophic factors against the dopamine-depleting effects of neurotoxic doses of methamphetamine.

PubMed

Cass, Wayne A; Peters, Laura E; Harned, Michael E; Seroogy, Kim B

2006-08-01

Repeated methamphetamine (METH) administration to animals can result in long-lasting decreases in striatal dopamine (DA) content. It has previously been shown that glial cell line-derived neurotrophic factor (GDNF) can reduce the DA-depleting effects of neurotoxic doses of METH. However, there are several other trophic factors that are protective against dopaminergic toxins. Thus, the present experiments further investigated the protective effect of GDNF as well as the protective effects of several other trophic factors. Male Fischer-344 rats were given an intracerebral injection of trophic factor (2-10 microg) 1 day before METH (5 mg/kg, s.c., 4 injections at 2-h intervals). Seven days later DA levels in the striatum were measured using high-performance liquid chromatography (HPLC). Initial experiments indicated that only intrastriatal GDNF, and not intranigral GDNF, was protective. Thereafter, all other trophic factors were administered into the striatum. Members of the GDNF family (GDNF, neurturin, and artemin) all provided significant protection against the DA-depleting effects of METH, with GDNF providing the greatest protection. Brain-derived neurotrophic factor, neurotrophin-3, acidic fibroblast growth factor, basic fibroblast growth factor, ciliary neurotrophic factor, transforming growth factor-alpha (TGF-alpha), heregulin beta1 (HRG-beta1), and amphiregulin (AR) provided no significant protection at the doses examined. These results suggest that the GDNF family of trophic factors can provide significant protection against the DA-depleting effects of neurotoxic doses of METH.

Bathymetric limits of chondrichthyans in the deep sea: A re-evaluation

NASA Astrophysics Data System (ADS)

Musick, J. A.; Cotton, C. F.

2015-05-01

Chondrichthyans are largely absent in abyssal (>3000 m) habitats in most regions of the world ocean and are uncommon below 2000 m. The deeper-living chondrichthyans include certain rajids, squaliforms and holocephalans. Several hypotheses have been erected to explain the absence of chondrichthyans from the abyss. These are mostly based on energetics: deep-sea food webs are impoverished due to their distance from primary production, and chondrichthyans, occupying the highest trophic levels, cannot be supported due to entropy among trophic levels. We examined this hypothesis by comparing trophic levels, calculated from dietary data, of deep-sea chondrichthyans with those of deep-sea teleosts. Chondrichthyans were mostly above trophic level 4, whereas all the teleosts examined were below that level. Both small and medium squaloids, as well as sharks and skates of large size, feed on fishes, cephalopods and scavenged prey, and thus occupy the highest trophic levels in bathydemersal fish communities. In addition, whereas teleosts and chondrichthyans both store lipids in their livers to support long periods of fasting, chondrichthyans must devote much of their liver lipids to maintain neutral buoyancy. Consequently teleosts with swim bladders are better adapted to survive in the abyss where food sources are sparse and unpredictable. The potential prey field for both chondrichthyans and teleosts declines in biomass and diversity with depth, but teleosts have more flexibility in their feeding mechanisms and food habits, and occupy abyssal trophic guilds for which chondrichthyans are ill adapted.

Trophic Interactions Between Insects and Stream-Associated Amphibians in Steep, Cobble-Bottom Streams of the Pacific Coast of North America

PubMed Central

Atwood, Trisha; Richardson, John S.

2012-01-01

Two native, stream-associated amphibians are found in coastal streams of the west coast of North America, the tailed frog and the coastal giant salamander, and each interacts with stream insects in contrasting ways. For tailed frogs, their tadpoles are the primary life stage found in steep streams and they consume biofilm from rock surfaces, which can have trophic and non-trophic effects on stream insects. By virtue of their size the tadpoles are relatively insensitive to stream insect larvae, and tadpoles are capable of depleting biofilm levels directly (exploitative competition), and may also “bulldoze” insect larvae from the surfaces of stones (interference competition). Coastal giant salamander larvae, and sometimes adults, are found in small streams where they prey primarily on stream insects, as well as other small prey. This predator-prey interaction with stream insects does not appear to result in differences in the stream invertebrate community between streams with and without salamander larvae. These two examples illustrate the potential for trophic and non-trophic interactions between stream-associated amphibians and stream insects, and also highlights the need for further research in these systems. PMID:26466536

Effect of flood pulses on the trophic ecology of four piscivorous fishes from the eastern Amazon.

PubMed

Barbosa, T A P; Rosa, D C O; Soares, B E; Costa, C H A; Esposito, M C; Montag, L F A

2018-06-08

This study investigated the effect of hydrological periods on the feeding activity and trophic interactions of four piscivorous fishes from the middle Xingu River, Brazil: pike-characid Boulengerella cuvieri, dogtooth characin Hydrolycus armatus, dogtooth characin Hydrolycus tatauaia and South American silver croaker Plagioscion squamosissimus. Repletion Index (I R %), Alimentary Index (I Ai %) and food web properties were calculated for each species. A total of 825 specimens were collected. The I R showed changes in feeding intensity of B. cuvieri, H. armatus and H. tatauaia among hydrological periods. Flood pulse showed no influence on composition and importance of food items consumed. Trophic connections showed that connectivity ranged from 0.025 to 0.038. The highest number of trophic connections (75) occurred in the high-water period, when 51 food items were recorded and the lowest number of trophic connections (43) occurred in receding water, with 31 food items. In all food webs, over 45% of food items were consumed by only one species (ultra-peripheral items), which is common in piscivorous fishes. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Density-dependent effects of omnivorous stream crayfish on benthic trophic dynamics

USGS Publications Warehouse

Ludlam, J.P.; Banks, B. T.; Magoulick, Daniel D.

2015-01-01

Crayfish are abundant and important consumers in aquatic food webs and crayfish invasions have demonstrated strong effects of crayfish on multiple trophic levels. Density may be an important factor determining the role of omnivorous crayfish in benthic communities, especially if density alters the strength of trophic interactions. The effect of crayfish density on a simple benthic food web using ceramic tiles was examined in three treatments (crayfish exclusion cage, cage control (open to crayfish), and exposed ceramic tiles) in mesocosms stocked with 6, 12, or 18 crayfish·m-2. We hypothesized that at low densities crayfish consumption of herbivorous chironomids would increase algal abundance, but at high densities crayfish would reduce both periphyton and invertebrates. In the experiment, periphyton and chironomid abundance increased with declining crayfish biomass on day 30 but not day 15. The magnitude of crayfish effects on day 15 periphyton chlorophyll a abundance increased with crayfish biomass, but crayfish effects on day 30 periphyton chlorophyll a or chironomid biomass did not increase with crayfish biomass. In this experiment there was little evidence for a trophic cascade at low crayfish densities and strong omnivory by crayfish dominated trophic dynamics.

Limnological characteristics and trophic state of a newly created site: the Pareja Limno-reservoir

NASA Astrophysics Data System (ADS)

Molina-Navarro, E.; Martínez-Pérez, S.; Sastre-Merlín, A.

2012-04-01

The creation of dams in the riverine zone of large reservoirs is an innovative action whose primary goal is to generate water bodies that ensure a stable level of water there. We have termed these bodies of water "limno-reservoirs" because their water level becomes constant and independent of the fluctuations occurring in the main reservoir. In addition, limno-reservoirs represent environmental initiatives with corrective and/or compensatory effects. Pareja Limno-reservoir, located near the left side of Entrepeñas Reservoir (Guadalajara province, central Spain), is one of the first initiatives of this type in Spain. We are investigating the hydrology, limnology, microbiology, siltation risk and other aspects of this site. This research has a special interest since the building of limno-reservoirs is rising in Spain. To acquire knowledge about their behavior may be helpful for further constructions. In fact, every new reservoir building project usually includes a limno-reservoir. Moreover, there are many initiatives related with the construction of this kind of hydraulic infrastructures in the reservoirs under exploitation. This work focuses on the limnological study of the Pareja Limno-reservoir. To conduct this research, twelve seasonal sample collections at two sampling points (the dam and inflow zones) have been made in Pareja Limno-reservoir, from spring 2008 to winter 2011. The primary goal of this study is to describe the limnological characteristics of the limno-reservoir. Special interest is placed in the study of the trophic state through different indicators (nutrients, transparency, phytoplankton and zooplankton populations), as the European Water Framework Directive objective is to achieve a "good ecological status" in every aquatic ecosystem by 2015. The results of the study show that the Pareja Limno-reservoir follows a warm monomictic water stratification pattern. Water was slightly alkaline and conductivity values were mostly over 1000 μS cm-1 due to the high SO4= concentrations. The highest N and P levels were found in the winter, whereas the highest chlorophyll aand phytoplankton biomass values were found in the summer and autumn. The total zooplankton species richness was high, especially in the inflow zone. Globally, the results obtained suggest that the Pareja Limno-reservoir is oligo-mesotrophic, so it may be under the WFD requirements, although some differences were found using a variety of trophic state criteria.

Analysis on the spatiotemporal characteristics of water quality and trophic states in Tiegang Reservoir: A public drinking water supply reservoir in South China

NASA Astrophysics Data System (ADS)

Song, Yun-long; Zhu, Jia; Li, Wang; Tao, Yi; Zhang, Jin-song

2017-08-01

Shenzhen is the most densely populated city in China and with a severe shortage of water. The per capita water resource is less than 200 m3, which is approximately 1/12 of the national average level. In 2016, nearly 90% of Shenzhen’s drinking water needed to be imported from the Pearl River. After arrived at Shenzhen, overseas water was firstly stockpiled in local reservoirs and then was supplied to nearby water works. Tiegang Reservoir is the largest drinking water supply reservoir and its water quality has played an important role to the city’s drinking water security. A fifteen-month’s field observation was conducted from April 2013 to June 2014 in Tiegang Reservoir, in order to analyze the temporal and spatial distribution of water quality factors and seasonal variation of trophic states. One-way ANOVA showed that significant difference was found in water quality factors on month (p<0.005). The spatial heterogeneity of water quality was obvious (p<0.05). The distribution pattern of WT, TOC, Silicate, NO3 --N, TN and Fe was pre-rainy period > latter rainy period > high temperature and rain free period > temperature jump period > winter drought period, while SD showed the contrary. Two-way ANOVA showed that months rather than locations were the key influencing factors of water quality factors succession. Tiegang reservoir was seriously polluted by TN, as a result WQI were at IV∼V level. If TN was not taken into account, WQI were atI∼III level. TLI (Σ) were about 35∼60, suggesting Tiegang reservoir was in mesotrophic and light-eutrophic trophic states. The WQI and TLI (Σ) in sampling sites 9 and 10 were poorer than that of other sites. The 14 water quality factors were divided into 5 groups by factor analysis (FA). The total interpretation rate was 73.54%. F1 represents the climatic change represented by water temperature. F2 and F4 represent the concentration of nutrients. F3 and F5 represent the sensory indexes of water body, such as turbidity, transparency. The FA results indicated that water quality potential risk factors was total nitrogen (TN), and potential risk factors also include chlorophyll-a and nitrate nitrogen (NO3 --N).

Trophic cascades from wolves to grizzly bears or changing abundance of bears and alternate foods?

USGS Publications Warehouse

Barber-Meyer, Shannon M.

2015-01-01

This is a Forum article commenting on: Ripple, W. J., Beschta, R. L., Fortin, J. K., & Robbins, C. T. (2014) Trophic cascades from wolves to grizzly bears in Yellowstone. Journal of Animal Ecology, 83, 223–233. Comparisons Ripple et al. (2014) used to demonstrate increased fruit availability and consumption by grizzly bears post-wolf reintroduction are flawed and tenuous at best. Importantly, a more parsimonious (than trophic cascades) hypothesis, not sufficiently considered by Ripple et al., exists and is better supported by available data I review.

Neuronal somata and extrasomal compartments play distinct roles during synapse formation between Lymnaea neurons.

PubMed

Xu, Fenglian; Luk, Collin C; Wiersma-Meems, Ryanne; Baehre, Kelly; Herman, Cameron; Zaidi, Wali; Wong, Noelle; Syed, Naweed I

2014-08-20

Proper synapse formation is pivotal for all nervous system functions. However, the precise mechanisms remain elusive. Moreover, compared with the neuromuscular junction, steps regulating the synaptogenic program at central cholinergic synapses remain poorly defined. In this study, we identified different roles of neuronal compartments (somal vs extrasomal) in chemical and electrical synaptogenesis. Specifically, the electrically synapsed Lymnaea pedal dorsal A cluster neurons were used to study electrical synapses, whereas chemical synaptic partners, visceral dorsal 4 (presynaptic, cholinergic), and left pedal dorsal 1 (LPeD1; postsynaptic) were explored for chemical synapse formation. Neurons were cultured in a soma-soma or soma-axon configuration and synapses explored electrophysiologically. We provide the first direct evidence that electrical synapses develop in a soma-soma, but not soma-axon (removal of soma) configuration, indicating the requirement of gene transcription regulation in the somata of both synaptic partners. In addition, the soma-soma electrical coupling was contingent upon trophic factors present in Lymnaea brain-conditioned medium. Further, we demonstrate that chemical (cholinergic) synapses between soma-soma and soma-axon pairs were indistinguishable, with both exhibiting a high degree of contact site and target cell type specificity. We also provide direct evidence that presynaptic cell contact-mediated, clustering of postsynaptic cholinergic receptors at the synaptic site requires transmitter-receptor interaction, receptor internalization, and a protein kinase C-dependent lateral migration toward the contact site. This study provides novel insights into synaptogenesis between central neurons revealing both distinct and synergistic roles of cell-cell signaling and extrinsic trophic factors in executing the synaptogenic program. Copyright © 2014 the authors 0270-6474/14/3411304-12$15.00/0.

Mercury Speciation and Trophic Magnification Slopes in Giant Salamander Larvae from the Pacific Northwest, USA

NASA Astrophysics Data System (ADS)

Bank, M. S.; Crocker, J.; Wachtl, J.; Kleeman, P.; Fellers, G.; Currens, C.; Hothem, R.; Madej, M. A.

2014-12-01

Mercury (Hg) contamination of stream salamanders in the Pacific Northwest region of the United States has received little attention. Here we report total Hg (HgT) and methyl mercury (MeHg) concentrations in larval giant salamanders (Dicamptodon spp.) and surface water from forested and chaparral lotic ecosystems distributed along a latitudinal gradient throughout Northern California and Washington. To test hypotheses related to potential effects from mining land-use activities, salamander larvae were also sampled from a reference site at Whiskeytown National Recreation Area, California, and at a nearby, upstream site (Shasta county) on Bureau of Land Management land where Hg contamination from gold mining activities has been documented. HgT concentrations in whole body larvae ranged from 4.6 to 74.5 ng/g wet wt. and percent MeHg ranged from 67% to 86%. Both HgT and MeHg larval tissue concentrations were significantly higher at the mining site in comparison to measured background levels (P < 0.001). We conclude that salamander larvae in remote stream ecosystems, where Hg sources were dominated by atmospheric deposition, were generally low in HgT and MeHg and, in comparison, watersheds with a legacy of land-use practices (i.e., mining operations) had approximately 4.5 - 5.5 times the level of HgT bioaccumulation. Moreover, trophic magnification slopes were highest in the Shasta county region where mining was present. These findings suggest that mining activities increase HgT and MeHg exposure to salamander larvae in the region and may present a threat to other higher trophically positioned organisms, and their associated food webs.

Secondary foundation species as drivers of trophic and functional diversity: evidence from a tree-epiphyte system.

PubMed

Angelini, Christine; Silliman, Brian R

2014-01-01

Facilitation cascades arise where primary foundation species facilitate secondary (dependent) foundation species, and collectively, they increase habitat complexity and quality to enhance biodiversity. Whether such phenomena occur in nonmarine systems and if secondary foundation species enhance food web structure (e.g., support novel feeding guilds) and ecosystem function (e.g., provide nursery for juveniles) remain unclear. Here we report on field experiments designed to test whether trees improve epiphyte survival and epiphytes secondarily increase the number and diversity of adult and juvenile invertebrates in a potential live oak-Tillandsia usneoides (Spanish moss) facilitation cascade. Our results reveal that trees reduce physical stress to facilitate Tillandsia, which, in turn, reduces desiccation and predation stress to facilitate invertebrates. In experimental removals, invertebrate total density, juvenile density, species richness and H' diversity were 16, 60, 1.7, and 1.5 times higher, and feeding guild richness and H' were 5 and 11 times greater in Tillandsia-colonized relative to Tillandsia-removal limb plots. Tillandsia enhanced communities similarly in a survey across the southeastern United States. These findings reveal that a facilitation cascade organizes this widespread terrestrial assemblage and expand the role of secondary foundation species as drivers of trophic structure and ecosystem function. We conceptualize the relationship between foundation species' structural attributes and associated species abundance and composition in a Foundation Species-Biodiversity (FSB) model. Importantly, the FSB predicts that, where secondary foundation species form expansive and functionally distinct structures that increase habitat availability and complexity within primary foundation species, they generate and maintain hot spots of biodiversity and trophic interactions.

Bioaccumulation of organohalogenated compounds in sharks and rays from the southeastern USA.

PubMed

Weijs, Liesbeth; Briels, Nathalie; Adams, Douglas H; Lepoint, Gilles; Das, Krishna; Blust, Ronny; Covaci, Adrian

2015-02-01

Organohalogenated compounds are widespread in the marine environment and can be a serious threat to organisms in all levels of aquatic food webs, including elasmobranch species. Information about the concentrations of POPs (persistent organic pollutants) and of MeO-PBDEs (methoxylated polybrominated diphenyl ethers) in elasmobranchs is scarce and potential toxic effects are poorly understood. The aims of the present study were therefore to investigate the occurrence of multiple POP classes (PCBs, PBDEs, DDXs, HCB, CHLs) and of MeO-PBDEs in various elasmobranch species from different trophic levels in estuarine and marine waters of the southeastern United States. Overall, levels and patterns of PCBs, PBDEs, DDXs, HCB, CHLs and of MeO-PBDEs varied according to the species, maturity stage, gender and habitat type. The lowest levels of POPs were found in Atlantic stingrays and the highest levels were found in bull sharks. As both species are respectively near the bottom and at top of the trophic web, with juvenile bull sharks frequently feeding on Atlantic stingrays, these findings further suggest a bioaccumulation and biomagnification process with trophic position. MeO-PBDEs were not detected in Atlantic stingrays, but were found in all shark species. HCB was not found in Atlantic stingrays, bonnetheads or lemon sharks, but was detected in the majority of bull sharks examined. Comparison with previous studies suggests that Atlantic stingrays may be experiencing toxic effects of PCBs and DDXs on their immune system. However, the effect of these compounds on the health of shark species remains unclear. Copyright © 2014 Elsevier Inc. All rights reserved.

Potential trophic cascades triggered by the barred owl range expansion

USGS Publications Warehouse

Holm, Samantha R.; Noon, Barry R.; Wiens, David; Ripple, William J.

2016-01-01

Recently, the barred owl (Strix varia) has expanded its range into the Pacific Northwest of the United States resulting in pronounced effects on the demography and behavior of the northern spotted owl (S. occidentalis caurina). The range expansion has brought together historically allopatric species, creating the potential for significant changes in the avian predator community with possible cascading effects on food-web dynamics. The adverse effects of the barred owl on the behavior and demography of the northern spotted owl are well-documented, but little is known about the immediate and long-term effects changes in the predator community may have on native species composition and ecosystem processes. Based on northern spotted owl and barred owl selection for diet and habitat resources, there is a potential for trophic cascades within the region's predator and prey communities, differing responses by their shared and unique prey species, and possible direct and indirect effects on ecosystem processes. We explored the possible ecological consequences of the barred owl range expansion to wildlife communities of the Pacific Northwest based on the theoretical underpinnings of predator–prey relationships, interspecific competition, intraguild predation, and potential cascading trophic interactions. Negative effects on fitness of northern spotted owls because of interspecific competition with barred owls are strong selection forces that may contribute to the regional extinction of the northern spotted owl. In addition, we posit that shared prey species and those uniquely consumed by barred owls, along with other competing native predators, may experience changes in behavior, abundance, and distribution as a result of increased rates of predation by rapidly expanding populations of barred owls.

Evolutionary transitions in symbioses: dramatic reductions in bathymetric and geographic ranges of Zoanthidea coincide with loss of symbioses with invertebrates.

PubMed

Swain, Timothy D

2010-06-01

Two fundamental symbiosis-based trophic types are recognized among Zoanthidea (Cnidaria, Anthozoa): fixed carbon is either obtained directly from zooxanthellae photosymbionts or from environmental sources through feeding with the assistance of host-invertebrate behaviour and structure. Each trophic type is characteristic of the suborders of Zoanthidea and is associated with substantial distributional asymmetries: suborder Macrocnemina are symbionts of invertebrates and have global geographic and bathymetric distributions and suborder Brachycnemina are hosts of endosymbiotic zooxanthellae and are restricted to tropical photic zones. While exposure to solar radiation could explain the bathymetric asymmetry it does not explain the geographic asymmetry, nor is it clear why evolutionary transitions to the zooxanthellae-free state have apparently occurred within Macrocnemina but not within Brachycnemina. To better understand the transitions between symbiosis-based trophic types of Zoanthidea, a concatenated data set of nuclear and mitochondrial nucleotide sequences were used to test hypotheses of monophyly for groups defined by morphology and symbiosis, and to reconstruct the evolutionary transitions of morphological and symbiotic characters. The results indicate that the morphological characters that define Macrocnemina are plesiomorphic and the characters that define its subordinate taxa are homoplasious. Symbioses with invertebrates have ancient and recent transitions with a general pattern of stability in host associations through evolutionary time. The reduction in distribution of Zoanthidea is independent of the evolution of zooxanthellae symbiosis and consistent with hypotheses of the benefits of invertebrate symbioses, indicating that the ability to persist in most habitats may have been lost with the termination of symbioses with invertebrates.

Mercury biomagnification and the trophic structure of the ichthyofauna from a remote lake in the Brazilian Amazon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azevedo-Silva, Claudio Eduardo, E-mail: ceass@biof

The present study assesses mercury biomagnification and the trophic structure of the ichthyofauna from the Puruzinho Lake, Brazilian Amazon. In addition to mercury determination, the investigation comprised the calculation of Trophic Magnification Factor (TMF) and Trophic Magnification Slope (TMS), through the measurements of stable isotopes of carbon (δ{sup 13}C) and nitrogen (δ{sup 15}N) in fish samples. These assessments were executed in two different scenarios, i.e., considering (1) all fish species or (2) only the resident fish (excluding the migratory species). Bottom litter, superficial sediment and seston were the sources used for generating the trophic position (TP) data used in themore » calculation of the TMF. Samples from 84 fish were analysed, comprising 13 species, which were categorized into four trophic guilds: iliophagous, planktivorous, omnivorous and piscivorous fish. The δ{sup 13}C values pointed to the separation of the ichthyofauna into two groups. One group comprised iliophagous and planktivorous species, which are linked to the food chains of phytoplankton and detritus. The other group was composed by omnivorous and piscivorous fish, which are associated to the trophic webs of phytoplankton, bottom litter, detritus, periphyton, as well as to food chains of igapó (blackwater-flooded Amazonian forests). The TP values suggest that the ichthyofauna from the Puruzinho Lake is part of a short food web, with three well-characterized trophic levels. Mercury concentrations and δ{sup 13}C values point to multiple sources for Hg input and transfer. The similarity in Hg levels and TP values between piscivorous and planktivorous fish suggests a comparable efficiency for the transfer of this metal through pelagic and littoral food chains. Regarding the two abovementioned scenarios, i.e., considering (1) the entire ichthyofauna and (2) only the resident species, the TMF values were 5.25 and 4.49, as well as the TMS values were 0.21 and 0.19, respectively. These findings confirm that Hg biomagnifies through the food web of Puruzinho Lake ichthyofauna. The migratory species did not significantly change mercury biomagnification rate in Puruzinho Lake; however, they may play a relevant role in Hg transport. The biomagnification rate (TMS value) in Puruzinho Lake was higher than the average values for its latitude, being comparable to TMS values of temperate and polar systems (marine and freshwater environments). - Highlights: • Mercury biomagnified in food web of a remote Amazonian lake. • δ{sup 13}C and δ{sup 15}N values suggest multiple Hg sources in food web with 3 trophic levels. • We found similar Hg transfer efficiencies in pelagic and littoral food chains. • Migration may influence the trophic structure assessment performed with δ{sup 15}N. • The migrating species did not significantly alter the biomagnification calculation.« less

Feeding strategies and ecological roles of three predatory pelagic fish in the western Mediterranean Sea

NASA Astrophysics Data System (ADS)

Navarro, Joan; Sáez-Liante, Raquel; Albo-Puigserver, Marta; Coll, Marta; Palomera, Isabel

2017-06-01

Knowing the feeding ecology of marine predators is pivotal to developing an understanding of their ecological role in the ecosystem and determining the trophic relationships between them. Despite the ecological importance of predatory pelagic fish species, research on these species in the Mediterranean Sea is limited. Here, by combining analyses of stomach contents and stable isotope values, we examined the feeding strategies of swordfish, Xiphias gladius, little tunny, Euthynnus alletteratus and Atlantic bonito, Sarda sarda, in the western Mediterranean Sea. We also compared the trophic niche and trophic level of these species with published information of other sympatric pelagic predators present in the ecosystem. Results indicated that, although the diet of the three species was composed mainly by fin-fish species, a clear segregation in their main feeding strategies was found. Swordfish showed a generalist diet including demersal species such as blue whiting, Micromesistius poutassou, and European hake, Merluccius merluccius, and pelagic fin-fish such as barracudina species (Arctozenus risso and Lestidiops jayakari) or small pelagic fish species. Little tunny and Atlantic bonito were segregated isotopically between them and showed a diet basically composed of anchovy, Engraulis encrasicolus, and round sardinella, Sardinella aurita, and sardines, Sardina pilchardus, respectively. This trophic segregation, in addition to potential segregation by depth, is likely a mechanism that allows their potential coexistence within the same pelagic habitat. When the trophic position of these three predatory pelagic fish species is compared with other pelagic predators such as bluefin tuna, Thunnus thynnus, and dolphinfish, Coryphaena hippurus, present in the western Mediterranean Sea, we found that they show similar intermediate trophic position in the ecosystem. In conclusion, the combined stomach and isotopic results highlight, especially for little tunny and Atlantic bonito, the trophic importance of Clupeoid species in their diet. In addition, the importance of demersal resources for swordfish provides evidence for the pelagic-demersal coupling of the ecosystem and the need to manage marine resources in an integrated way.

Application of Nitrogen and Carbon Stable Isotopes (δ15N and δ13C) to Quantify Food Chain Length and Trophic Structure

PubMed Central

Perkins, Matthew J.; McDonald, Robbie A.; van Veen, F. J. Frank; Kelly, Simon D.; Rees, Gareth; Bearhop, Stuart

2014-01-01

Increasingly, stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) are used to quantify trophic structure, though relatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plant-invertebrate food chains spanning four trophic levels we estimated nitrogen range (NR) using δ15N, and carbon range (CR) using δ13C, which are used to quantify food chain length and breadth of trophic resources respectively. Across a range of known food chain lengths we examined how NR and CR changed within and between food chains. Our isotopic estimates of structure are robust because they were calculated using resampling procedures that propagate variance in sample means through to quantified uncertainty in final estimates. To identify origins of uncertainty in estimates of NR and CR, we additionally examined variation in discrimination (which is change in δ15N or δ13C from source to consumer) between trophic levels and among food chains. δ15N discrimination showed significant enrichment, while variation in enrichment was species and system specific, ranged broadly (1.4‰ to 3.3‰), and importantly, propagated variation to subsequent estimates of NR. However, NR proved robust to such variation and distinguished food chain length well, though some overlap between longer food chains infers a need for awareness of such limitations. δ13C discrimination was inconsistent; generally no change or small significant enrichment was observed. Consequently, estimates of CR changed little with increasing food chain length, showing the potential utility of δ13C as a tracer of energy pathways. This study serves as a robust test of isotopic quantification of food chain structure, and given global estimates of aquatic food chains approximate four trophic levels while many food chains include invertebrates, our use of four trophic level plant-invertebrate food chains makes our findings relevant for a majority of ecological systems. PMID:24676331

Beyond diversity: how nested predator effects control ecosystem functions.

PubMed

Schneider, Florian Dirk; Brose, Ulrich

2013-01-01

The global decline in biodiversity is especially evident in higher trophic levels as predators display higher sensitivity to environmental change than organisms from lower trophic levels. This is even more alarming given the paucity of knowledge about the role of individual predator species in sustaining ecosystem functioning. The effect of predator diversity on lower trophic level prey is often driven by the increasing chance of including the most influential species. Furthermore, intraguild predation can cause trophic cascades with net positive effects on basal prey. As a consequence, the effects of losing a predator species appear to be idiosyncratic and it becomes unpredictable how the community's net effect on lower trophic levels changes when species number is declining. We performed a full factorial microcosm experiment with litter layer arthropods to measure the effects of predator diversity and context-dependent identity effects on a detritivore population and microbial biomass. We show that major parts of the observed diversity effect can be assigned to the increasing likelihood of including the most influential predator. Further, the presence of a second predator feeding on the first predator dampens this dominant effect. Including this intraguild predator on top of the first predator is more likely with increasing predator diversity as well. Thus, the overall pattern can be explained by a second identity effect, which is nested into the first. When losing a predator from the community, the response of the lower trophic level is highly dependent on the remaining predator species. We mechanistically explain the net effects of the predator community on lower trophic levels by nested effects of predator identities. These identity effects become predictable when taking the species' body masses into account. This provides a new mechanistic perspective describing ecosystem functioning as a consequence of species composition and yields an understanding beyond simple effects of biodiversity. © 2012 The Authors. Journal of Animal Ecology © 2012 British Ecological Society.

Fish communities and trophic metrics as measures of ecological degradation: a case study in the tributaries of the river Ganga basin, India.

PubMed

Dubey, Vineet Kumar; Sarkar, Uttam Kumar; Pandey, Ajay; Lakra, Wazir Singh

2013-09-01

In India, freshwater aquatic resources are suffering from increasing human population, urbanization and shortage of all kind of natural resources like water. To mitigate this, all the major rivers have been planned for a river-interlinking through an interlinking canal system under a huge scheme; yet, the baseline information on ecological conditions of those tropical rivers and their fish communities is lacking at present. In view of that, the present study was undertaken to assess the ecological condition by comparing the trophic metrics of the fish community, conservation status and water chemistry of the two tropical rivers of the Ganga basin, from October 2007 to November 2009. The analysis of trophic niches of the available fish species indicated dominancy of carnivorous (19 species) in river Ken and omnivorous (23 species) in Betwa. The trophic level score of carnivorous species was recorded similar (33.33%) in both rivers, whereas omnivorous species were mostly found in Betwa (36.51%) than Ken (28.07%). Relatively undisturbed sites of Betwa (B1, B2 and B3) and Ken (K2, K3 and K5) were characterized by diverse fish fauna and high richness of threatened species. The higher mean trophic level scores were recorded at B4 of Betwa and K4 of Ken. The Bray-Curtis index for trophic level identified the carnivorous species (> 0.32) as an indicator species for pollution. Anthropogenic exposure, reflected in water quality as well as in fish community structure, was found higher especially in the lower stretches of both rivers. Our results suggest the importance of trophic metrics on fish community, for ecological conditions evaluation, which enables predictions on the effect of future morphodynamic changes (in the post-interlinking phases), and provide a framework and reference condition to support restoration efforts of relatively altered fish habitats in tropical rivers of India.

Trophic ecology and vertical patterns of carbon and nitrogen stable isotopes in zooplankton from oxygen minimum zone regions

NASA Astrophysics Data System (ADS)

Williams, Rebecca L.; Wakeham, Stuart; McKinney, Rick; Wishner, Karen F.

2014-08-01

The unique physical and biogeochemical characteristics of oxygen minimum zones (OMZs) influence plankton ecology, including zooplankton trophic webs. Using carbon and nitrogen stable isotopes, this study examined zooplankton trophic webs in the Eastern Tropical North Pacific (ETNP) OMZ. δ13C values were used to indicate zooplankton food sources, and δ15N values were used to indicate zooplankton trophic position and nitrogen cycle pathways. Vertically stratified MOCNESS net tows collected zooplankton from 0 to 1000 m at two stations along a north-south transect in the ETNP during 2007 and 2008, the Tehuantepec Bowl and the Costa Rica Dome. Zooplankton samples were separated into four size fractions for stable isotope analyses. Particulate organic matter (POM), assumed to represent a primary food source for zooplankton, was collected with McLane large volume in situ pumps. The isotopic composition and trophic ecology of the ETNP zooplankton community had distinct spatial and vertical patterns influenced by OMZ structure. The most pronounced vertical isotope gradients occurred near the upper and lower OMZ oxyclines. Material with lower δ13C values was apparently produced in the upper oxycline, possibly by chemoautotrophic microbes, and was subsequently consumed by zooplankton. Between-station differences in δ15N values suggested that different nitrogen cycle processes were dominant at the two locations, which influenced the isotopic characteristics of the zooplankton community. A strong depth gradient in zooplankton δ15N values in the lower oxycline suggested an increase in trophic cycling just below the core of the OMZ. Shallow POM (0-110 m) was likely the most important food source for mixed layer, upper oxycline, and OMZ core zooplankton, while deep POM was an important food source for most lower oxycline zooplankton (except for samples dominated by the seasonally migrating copepod Eucalanus inermis). There was no consistent isotopic progression among the four zooplankton size classes for these bulk mixed assemblage samples, implying overlapping trophic webs within the total size range considered.

Trophic interactions of common elasmobranchs in deep-sea communities of the Gulf of Mexico revealed through stable isotope and stomach content analysis

NASA Astrophysics Data System (ADS)

Churchill, Diana A.; Heithaus, Michael R.; Vaudo, Jeremy J.; Grubbs, R. Dean; Gastrich, Kirk; Castro, José I.

2015-05-01

Deep-water sharks are abundant and widely distributed in the northern and eastern Gulf of Mexico. As mid- and upper-level consumers that can range widely, sharks likely are important components of deep-sea communities and their trophic interactions may serve as system-wide baselines that could be used to monitor the overall health of these communities. We investigated the trophic interactions of deep-sea sharks using a combination of stable isotope (δ13C and δ15N) and stomach content analyses. Two hundred thirty-two muscle samples were collected from elasmobranchs captured off the bottom at depths between 200 and 1100 m along the northern slope (NGS) and the west Florida slope (WFS) of the Gulf of Mexico during 2011 and 2012. Although we detected some spatial, temporal, and interspecific variation in apparent trophic positions based on stable isotopes, there was considerable isotopic overlap among species, between locations, and through time. Overall δ15N values in the NGS region were higher than in the WFS. The δ15N values also increased between April 2011 and 2012 in the NGS, but not the WFS, within Squalus cf. mitsukurii. We found that stable isotope values of S. cf. mitsukurii, the most commonly captured elasmobranch, varied between sample regions, through time, and also with sex and size. Stomach content analysis (n=105) suggested relatively similar diets at the level of broad taxonomic categories of prey among the taxa with sufficient sample sizes. We did not detect a relationship between body size and relative trophic levels inferred from δ15N, but patterns within several species suggest increasing trophic levels with increasing size. Both δ13C and δ15N values suggest a substantial degree of overlap among most deep-water shark species. This study provides the first characterization of the trophic interactions of deep-sea sharks in the Gulf of Mexico and establishes system baselines for future investigations.

Body size, trophic level, and the use of fish as transmission routes by parasites.

PubMed

Poulin, R; Leung, T L F

2011-07-01

Within food webs, trophically transmitted helminth parasites use predator-prey links for their own transfer from intermediate prey hosts, in which they occur as larval or juvenile stages, to predatory definitive hosts, in which they reach maturity. In large taxa that can be used as intermediate and/or definitive hosts, such as fish, a host species' position within a trophic network should determine whether its parasite fauna consists mostly of adult or larval helminths, since vulnerability to predation determines an animal's role in predator-prey links. Using a large database on the helminth parasites of 303 fish species, we tested whether the proportion of parasite species in a host that occur as larval or juvenile stages is best explained by their trophic level or by their body size. Independent of fish phylogeny or habitat, only fish body length emerged as a significant predictor of the proportion of parasites in a host that occur as larval stages from our multivariate analyses. On average, the proportion of larval helminth taxa in fish shorter than 20 cm was twice as high as that for fish over 100 cm in length. This is consistent with the prediction that small fishes, being more vulnerable to predation, make better hosts for larval parasites. However, trophic level and body length are strongly correlated among fish species, and they may have separate though confounded effects on the parasite fauna exploiting a given species. Helminths show varying levels of host specificity toward their intermediate host when the latter is the downstream host involved in trophic transmission toward an upstream definitive host. Given this broad physiological compatibility of many helminths with fish hosts, our results indicate that fish body length, as a proxy for vulnerability to predators, is a better predictor of their use by helminth larvae than their trophic level based on diet content.

Two new species of the Phanaeus endymion species group (Coleoptera, Scarabaeidae, Scarabaeinae).

PubMed

Moctezuma, Victor; Sánchez-Huerta, José Luis; Halffter, Gonzalo

2017-01-01

Phanaeus bravoensis sp. n. is described from the coniferous-oak forests in the state of Guerrero, and P. huichol sp. n. from coniferous-oak forests and cloud forests in Jalisco and Nayarit. The new species are closely related to P. halffterorum and P. zoque respectively. Morphological trait combination, geographic distribution, and trophic habits show important differences among the studied species. A distribution map and an updated key to separate the species are included.

Predator personality structures prey communities and trophic cascades.

PubMed

Start, Denon; Gilbert, Benjamin

2017-03-01

Intraspecific variation is central to our understanding of evolution and population ecology, yet its consequences for community ecology are poorly understood. Animal personality - consistent individual differences in suites of behaviours - may be particularly important for trophic dynamics, where predator personality can determine activity rates and patterns of attack. We used mesocosms with aquatic food webs in which the top predator (dragonfly nymphs) varied in activity and subsequent attack rates on zooplankton, and tested the effects of predator personality. We found support for four hypotheses: (1) active predators disproportionately reduce the abundance of prey, (2) active predators select for predator-resistant prey species, (3) active predators strengthen trophic cascades (increase phytoplankton abundance) and (4) active predators are more likely to cannibalise one another, weakening all other trends when at high densities. These results suggest that intraspecific variation in predator personality is an important determinant of prey abundance, community composition and trophic cascades. © 2017 John Wiley & Sons Ltd/CNRS.

A unifying theory for top-heavy ecosystem structure in the ocean.

PubMed

Woodson, C Brock; Schramski, John R; Joye, Samantha B

2018-01-02

Size generally dictates metabolic requirements, trophic level, and consequently, ecosystem structure, where inefficient energy transfer leads to bottom-heavy ecosystem structure and biomass decreases as individual size (or trophic level) increases. However, many animals deviate from simple size-based predictions by either adopting generalist predatory behavior, or feeding lower in the trophic web than predicted from their size. Here we show that generalist predatory behavior and lower trophic feeding at large body size increase overall biomass and shift ecosystems from a bottom-heavy pyramid to a top-heavy hourglass shape, with the most biomass accounted for by the largest animals. These effects could be especially dramatic in the ocean, where primary producers are the smallest components of the ecosystem. This approach makes it possible to explore and predict, in the past and in the future, the structure of ocean ecosystems without biomass extraction and other impacts.

Relationship between ecomorphology and trophic segregation in four closely related sympatric fish species (Teleostei, Sciaenidae).

PubMed

Blasina, Gabriela; Molina, Juan; Lopez Cazorla, Andrea; Díaz de Astarloa, Juan

This study explores the relationship between ecomorphology and trophic segregation in four closely related sympatric fish species (Teleostei, Sciaenidae) that are known to differ in their trophic habits. Only adult specimens were analyzed: 103 Cynoscion guatucupa, 77 Pogonias cromis, 61 Micropogonias furnieri, and 48 Menticirrhus americanus. The four species presented divergent ecomorphological traits related to swimming agility, prey spotting and capture, and the potential size of prey they were able to swallow. Results suggest that these sciaenid species can partition the food resources, even though they completely overlap in space. Differences in their ecomorphological traits appear to correlate closely with the diet and consequently could explain the trophic differentiation observed. Arguably, these ecomorphological differences play a significant role in the coexistence of the adults of these sympatric fish species. Copyright © 2016 Académie des sciences. Published by Elsevier SAS. All rights reserved.

First direct evidence of a vertebrate three-level trophic chain in the fossil record

PubMed Central

Kriwet, Jürgen; Witzmann, Florian; Klug, Stefanie; Heidtke, Ulrich H.J

2007-01-01

We describe the first known occurrence of a Permian shark specimen preserving two temnospondyl amphibians in its digestive tract as well as the remains of an acanthodian fish, which was ingested by one of the temnospondyls. This exceptional find provides for the first time direct evidence of a vertebrate three-level food chain in the fossil record with the simultaneous preservation of three trophic levels. Our analysis shows that small-sized Lower Permian xenacanthid sharks of the genus Triodus preyed on larval piscivorous amphibians. The recorded trophic interaction can be explained by the adaptation of certain xenacanthids to fully freshwater environments and the fact that in these same environments, large temnospondyls occupied the niche of modern crocodiles. This unique faunal association has not been documented after the Permian and Triassic. Therefore, this Palaeozoic three-level food chain provides strong and independent support for changes in aquatic trophic chain structures through time. PMID:17971323

First direct evidence of a vertebrate three-level trophic chain in the fossil record.

PubMed

Kriwet, Jürgen; Witzmann, Florian; Klug, Stefanie; Heidtke, Ulrich H J

2008-01-22

We describe the first known occurrence of a Permian shark specimen preserving two temnospondyl amphibians in its digestive tract as well as the remains of an acanthodian fish, which was ingested by one of the temnospondyls. This exceptional find provides for the first time direct evidence of a vertebrate three-level food chain in the fossil record with the simultaneous preservation of three trophic levels. Our analysis shows that small-sized Lower Permian xenacanthid sharks of the genus Triodus preyed on larval piscivorous amphibians. The recorded trophic interaction can be explained by the adaptation of certain xenacanthids to fully freshwater environments and the fact that in these same environments, large temnospondyls occupied the niche of modern crocodiles. This unique faunal association has not been documented after the Permian and Triassic. Therefore, this Palaeozoic three-level food chain provides strong and independent support for changes in aquatic trophic chain structures through time.

Effects of increasing seawater circulation by tidal power plant operation on the water quality in the Shihwa coastal reservoir, Republic of Korea

NASA Astrophysics Data System (ADS)

Lee, B. Y.; Lee, C. H.; KIm, K. T.

2016-02-01

Since 2012 to present, the Tidal Power Plant (TPP) has been operated in Shihwa Coastal Reservoir (SCR) to improve the water quality. The tidal mixing volume increased about 5 times from 0.03 to 0.16 billion ton/day which represents about 50% of the SCR water volume. Water quality monitoring data showed that it break a strong stratification and hypoxia (≤3 mg/L Dissolved Oxygen) during summer season in main tidal channel. In addition, Total Phosphorus (TP), Total Nitrogen (TN) and Chemical Oxygen Demand concentrations in the main tidal channel reached to similar level with outside SCR concentrations. However, inner area with limited tidal mixing has not experienced improvement in TN and TP concentrations after the TPP operation. Trophic State Index (TSI) which was composite index of trophic condition also kept high score (>50) and remained in eutrophic state especially in summer season. Overall, an increase of seawater circulation has a positive effect on water quality in main tidal channel but not in inner area because of limited seawater mixing and effects of stormwater runoff. The stormwater runoff should be properly managed in this case because most point source pollution load is discharged outside of SCR. Acknowledgement : This research was a part of the project titled 'Development of integrated estuarine management system', funded by the Ministry of Oceans and Fisheries, Korea

Bioaccumulation and elimination of bisphenol a (BPA) in the alga Chlorella pyrenoidosa and the potential for trophic transfer to the rotifer Brachionus calyciflorus.

PubMed

Guo, Ruixin; Du, Yingxiang; Zheng, Fengzhu; Wang, Jing; Wang, Zhiliang; Ji, Rong; Chen, Jianqiu

2017-08-01

In this study, we investigated the bioaccumulation and elimination of 14 C-labeled BPA by the green alga Chlorella pyrenoidosa and the subsequent transfer of 14 C-BPA residues from the contaminated alga to the rotifer Brachionus calyciflorus. After 10 days of BPA exposure, the algal cells accumulated 15% of the initial radioactivity from the medium, with 71% of the accumulated radioactivity occurring in the form of non-extractable bound residues. An approximate steady state of the accumulation of the 14 C-BPA residues in the algae was reached after about 4 days of exposure. The bioconcentration factor of total radioactivity in the algae was 106 mL (g dry weight) -1  at steady state. During the elimination phase, only the extractable residues were released from the algae into the water whereas the bound residues, following their ingestion by the rotifers, were converted to extractable forms and then also released. Furthermore, our results demonstrated the biomagnification of BPA-related residues in the food chain between algae and rotifers. The trophic transfer of these BPA-derived residues from the algae to rotifers and thus the environmental hazard may posed by this pathway, because of subsequent effects on the food chain. Copyright © 2017 Elsevier Ltd. All rights reserved.

Quality of surface water before implementation of a flood-control project in Chaska, Minnesota

USGS Publications Warehouse

Tornes, L.H.

1981-01-01

Samples were collected for 1 year from East Creek, Chaska Creek, and Courthouse Lake in Chaska, Minnesota, to determine the water quality before implementation of a flood-control project proposed by the U.S. Army Corps of Engineers. The creeks had similar water-quality characteristics. Data indicate that ground water may be the primary source of dissolved solids, sulfate, chloride, and chromium in the creeks. The pesticides alachlor, atrazine, simazine, and 2,4-D were found in water samples from both creeks but were well below the lethal concentrations for fish. Courthouse Lake, a 57-foot-deep stream-trout lake, had a mean summer trophic-state index of 35. Phytoplankton populations varied seasonally, and blue-green algae were predominant only in late summer. The algal-pollution index was highest in late summer, but did not provide evidence of high organic pollution. The apparently successful recovery of Courthouse Lake from past inundations by Minnesota River floodwaters having total phosphorus concentrations as high as 0.66 milligram per liter suggests that the lake, in time, will also recover from the added runoff expected as a result of implementing the flood-control project. The runoff could temporarily raise the total phosphorus concentration in the lake from 0.03 to 0.12 milligram per liter and raise the spring trophic-state index from 49 to 69.

Molecular-based approaches to characterize coastal microbial community and their potential relation to the trophic state of Red Sea

PubMed Central

Ansari, Mohd Ikram; Harb, Moustapha; Jones, Burton; Hong, Pei-Ying

2015-01-01

Molecular-based approaches were used to characterize the coastal microbiota and to elucidate the trophic state of Red Sea. Nutrient content and enterococci numbers were monitored, and used to correlate with the abundance of microbial markers. Microbial source tracking revealed the presence of >1 human-associated Bacteroides spp. at some of the near-shore sampling sites and at a heavily frequented beach. Water samples collected from the beaches had occasional exceedances in enterococci numbers, higher total organic carbon (TOC, 1.48–2.18 mg/L) and nitrogen (TN, 0.15–0.27 mg/L) than that detected in the near-shore waters. Enterococci abundances obtained from next-generation sequencing did not correlate well with the cultured enterococci numbers. The abundance of certain genera, for example Arcobacter, Pseudomonas and unclassified Campylobacterales, was observed to exhibit slight correlation with TOC and TN. Low abundance of functional genes accounting for up to 41 copies/L of each Pseudomonas aeruginosa and Campylobacter coli were detected. Arcobacter butzleri was also detected in abundance ranging from 111 to 238 copies/L. Operational taxonomic units (OTUs) associated with cyanobacteria, Prochlorococcus, Ostreococcus spp. and Gramella were more prevalent in waters that were likely impacted by urban runoffs and recreational activities. These OTUs could potentially serve as quantifiable markers indicative of the water quality. PMID:25758166

Complex life cycles in a pond food web: effects of life stage structure and parasites on network properties, trophic positions and the fit of a probabilistic niche model.

PubMed

Preston, Daniel L; Jacobs, Abigail Z; Orlofske, Sarah A; Johnson, Pieter T J

2014-03-01

Most food webs use taxonomic or trophic species as building blocks, thereby collapsing variability in feeding linkages that occurs during the growth and development of individuals. This issue is particularly relevant to integrating parasites into food webs because parasites often undergo extreme ontogenetic niche shifts. Here, we used three versions of a freshwater pond food web with varying levels of node resolution (from taxonomic species to life stages) to examine how complex life cycles and parasites alter web properties, the perceived trophic position of organisms, and the fit of a probabilistic niche model. Consistent with prior studies, parasites increased most measures of web complexity in the taxonomic species web; however, when nodes were disaggregated into life stages, the effects of parasites on several network properties (e.g., connectance and nestedness) were reversed, due in part to the lower trophic generality of parasite life stages relative to free-living life stages. Disaggregation also reduced the trophic level of organisms with either complex or direct life cycles and was particularly useful when including predation on parasites, which can inflate trophic positions when life stages are collapsed. Contrary to predictions, disaggregation decreased network intervality and did not enhance the fit of a probabilistic niche model to the food webs with parasites. Although the most useful level of biological organization in food webs will vary with the questions of interest, our results suggest that disaggregating species-level nodes may refine our perception of how parasites and other complex life cycle organisms influence ecological networks.

Trophic dilution of cyclic volatile methylsiloxanes (cVMS) in the pelagic marine food web of Tokyo Bay, Japan.

PubMed

Powell, David E; Suganuma, Noriyuki; Kobayashi, Keiji; Nakamura, Tsutomu; Ninomiya, Kouzo; Matsumura, Kozaburo; Omura, Naoki; Ushioka, Satoshi

2017-02-01

Bioaccumulation and trophic transfer of cyclic volatile methylsiloxanes (cVMS), specifically octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6), were evaluated in the pelagic marine food web of Tokyo Bay, Japan. Polychlorinated biphenyl (PCB) congeners that are "legacy" chemicals known to bioaccumulate in aquatic organisms and biomagnify across aquatic food webs were used as a benchmark chemical (CB-180) to calibrate the sampled food web and as a reference chemical (CB-153) to validate the results. Trophic magnification factors (TMFs) were calculated from slopes of ordinary least-squares (OLS) regression models and slopes of bootstrap regression models, which were used as robust alternatives to the OLS models. Various regression models were developed that incorporated benchmarking to control bias associated with experimental design, food web dynamics, and trophic level structure. There was no evidence from any of the regression models to suggest biomagnification of cVMS in Tokyo Bay. Rather, the regression models indicated that trophic dilution of cVMS, not trophic magnification, occurred across the sampled food web. Comparison of results for Tokyo Bay to results from other studies indicated that bioaccumulation of cVMS was not related to type of food web (pelagic vs demersal), environment (marine vs freshwater), species composition, or location. Rather, results suggested that differences between study areas was likely related to food web dynamics and variable conditions of exposure resulting from non-uniform patterns of organism movement across spatial concentration gradients. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Ecosystem structure and resilience—A comparison between the Norwegian and the Barents Sea

NASA Astrophysics Data System (ADS)

Yaragina, Natalia A.; Dolgov, Andrey V.

2009-10-01

Abundance and biomass of the most important fish species inhabited the Barents and Norwegian Sea ecosystems have shown considerable fluctuations over the last decades. These fluctuations connected with fishing pressure resulted in the trophic structure alterations of the ecosystems. Resilience and other theoretical concepts (top-down, wasp-waste and bottom-up control, trophic cascades) were viewed to examine different response of the Norwegian and Barents Sea ecosystems on disturbing forces. Differences in the trophic structure and functioning of Barents and Norwegian Sea ecosystems as well as factors that might influence the resilience of the marine ecosystems, including climatic fluctuation, variations in prey and predator species abundance, alterations in their regular migrations, and fishing exploitation were also considered. The trophic chain lengths in the deep Norwegian Sea are shorter, and energy transfer occurs mainly through the pelagic fish/invertebrates communities. The shallow Barents Sea is characterized by longer trophic chains, providing more energy flow into their benthic assemblages. The trophic mechanisms observed in the Norwegian Sea food webs dominated by the top-down control, i.e. the past removal of Norwegian Spring spawning followed by zooplankton development and intrusion of blue whiting and mackerel into the area. The wasp-waist response is shown to be the most pronounced effect in the Barents Sea, related to the position of capelin in the ecosystem; large fluctuations in the capelin abundance have been strengthened by intensive fishery. Closer links between ecological and fisheries sciences are needed to elaborate and test various food webs and multispecies models available.

Comparative organochlorine accumulation in two ecologically similar shark species (Carcharodon carcharias and Carcharhinus obscurus) with divergent uptake based on different life history.

PubMed

Beaudry, Marina C; Hussey, Nigel E; McMeans, Bailey C; McLeod, Anne M; Wintner, Sabine P; Cliff, Geremy; Dudley, Sheldon F J; Fisk, Aaron T

2015-09-01

Trophic position and body mass are traits commonly used to predict organochlorine burdens. Sharks, however, have a variety of feeding and life history strategies and metabolize lipid uniquely. Because of this diversity, and the lipid-association of organochlorines, the dynamics of organochlorine accumulation in sharks may be predicted ineffectively by stable isotope-derived trophic position and body mass, as is typical for other taxa. The present study compared ontogenetic organochlorine profiles in the dusky shark (Carcharhinus obscurus) and white shark (Carcharodon carcharias), which differ in metabolic thermoregulation and trophic position throughout their ontogeny. Although greater organochlorine concentrations were observed in the larger bodied and higher trophic position white shark (e.g., p,p'-dichlorodiphenyldichloroethylene: 20.2 ± 2.7 ng/g vs 9.3 ± 2.2 ng/g in the dusky shark), slopes of growth-dilution corrected concentrations with age were equal to those of the dusky shark. Similar ontogenetic trophic position increases in both species, less frequent white shark seal predation than previously assumed, or inaccurate species-specific growth parameters are possible explanations. Inshore habitat use (indicated by δ(13)C values) and mass were important predictors in white and dusky sharks, respectively, of both overall compound profiles and select organochlorine concentrations. The present study clarified understanding of trophic position and body mass as reliable predictors of interspecific organochlorine accumulation in sharks, whereas regional endothermy and diet shifting were shown to have less impact on overall rates of accumulation. © 2015 SETAC.

Roles of epiphytes associated with macroalgae in benthic food web of a eutrophic coastal lagoon

NASA Astrophysics Data System (ADS)

Zheng, Xinqing; Huang, Lingfeng; Lin, Rongcheng; Du, Jianguo

2015-11-01

Macroalgae perform a significant function in the trophic dynamics in many coastal lagoons, and conventionally, they are the key trophic base that fuels the overall aquatic food web. However, few studies have considered the trophic contribution of epiphytes that attach to macroalgae in the diet of benthic primary consumers or their contribution to the trophic base of the aquatic food web. In this study, macrobenthic invertebrate biomass was combined with multiple-isotope-mixing models to distinguish the trophic importance of macroalgae and their associated epiphytic assemblages in the benthic food web during Ulva lactuca bloom in the Yundang Lagoon, a eutrophic coastal lagoon in Xiamen, China. Amphipods primarily dominated the zoobenthos, with the biomass varied from 40.9 g/m2 in January to 283.9 g/m2 in March. They mainly fed on U. lactuca and its associated epiphytes, which jointly contributed more than 60% to amphipod diets, but species-specific feeding habits were exhibited among amphipods. Using the zoobenthos biomass as a weighting factor, the contribution of U. lactuca and its epiphytes to total benthic communities during U. lactuca bloom exceeded 65%.The epiphytes were clearly utilized more than U. lactuca, with a median contribution ranging from 48.5% in January to 66.6% in March. Our findings demonstrate the trophic importance of the epiphytes in macroalgae-based coastal habitats, as found in many seagrass beds. Therefore, we propose that further food web studies of macroalgae-based ecosystems should pay greater attention to the role of epiphytes.

Nitrogen isotopic baselines and implications for estimating foraging habitat and trophic position of yellowfin tuna in the Indian and Pacific Oceans

NASA Astrophysics Data System (ADS)

Lorrain, Anne; Graham, Brittany S.; Popp, Brian N.; Allain, Valérie; Olson, Robert J.; Hunt, Brian P. V.; Potier, Michel; Fry, Brian; Galván-Magaña, Felipe; Menkes, Christophe E. R.; Kaehler, Sven; Ménard, Frédéric

2015-03-01

Assessment of isotopic compositions at the base of food webs is a prerequisite for using stable isotope analysis to assess foraging locations and trophic positions of marine organisms. Our study represents a unique application of stable-isotope analyses across multiple trophic levels (primary producer, primary consumer and tertiary consumer) and over a large spatial scale in two pelagic marine ecosystems. We found that δ15N values of particulate organic matter (POM), barnacles and phenylalanine from the muscle tissue of yellowfin tuna all showed similar spatial patterns. This consistency suggests that isotopic analysis of any of these can provide a reasonable proxy for isotopic variability at the base of the food web. Secondly, variations in the δ15N values of yellowfin tuna bulk-muscle tissues paralleled the spatial trends observed in all of these isotopic baseline proxies. Variation in isotopic composition at the base of the food web, rather than differences in tuna diet, explained the 11‰ variability observed in the bulk-tissue δ15N values of yellowfin tuna. Evaluating the trophic position of yellowfin tuna using amino-acid isotopic compositions across the western Indian and equatorial Pacific Oceans strongly suggests these tuna occupy similar trophic positions, albeit absolute trophic positions estimated by this method were lower than expected. This study reinforces the importance of considering isotopic baseline variability for diet studies, and provides new insights into methods that can be applied to generate nitrogen isoscapes for worldwide comparisons of top predators in marine ecosystems.

Trophic ecomorphology of Siluriformes (Pisces, Osteichthyes) from a tropical stream.

PubMed

Pagotto, J P A; Goulart, E; Oliveira, E F; Yamamura, C B

2011-05-01

The present study analysed the relationship between morphology and trophic structure of Siluriformes (Pisces, Osteichthyes) from the Caracu Stream (22º 45' S and 53º 15' W), a tributary of the Paraná River (Brazil). Sampling was carried out at three sites using electrofishing, and two species of Loricariidae and four of Heptapteridae were obtained. A cluster analysis revealed the presence of three trophic guilds (detritivores, insectivores and omnivores). Principal components analysis demonstrated the segregation of two ecomorphotypes: at one extreme there were the detritivores (Loricariidae) with morphological structures that are fundamental in allowing them to fix themselves to substrates characterised by rushing torrents, thus permitting them to graze on the detritus and organic materials encrusted on the substrate; at the other extreme of the gradient there were the insectivores and omnivores (Heptapteridae), with morphological characteristics that promote superior performance in the exploitation of structurally complex habitats with low current velocity, colonised by insects and plants. Canonical discriminant analysis revealed an ecomorphological divergence between insectivores, which have morphological structures that permit them to capture prey in small spaces among rocks, and omnivores, which have a more compressed body and tend to explore food items deposited in marginal backwater zones. Mantel tests showed that trophic structure was significantly related to the body shape of a species, independently of the phylogenetic history, indicating that, in this case, there was an ecomorphotype for each trophic guild. Therefore, the present study demonstrated that the Siluriformes of the Caracu Stream were ecomorphologically structured and that morphology can be applied as an additional tool in predicting the trophic structure of this group.

Effect of medium osmolarity and taurine on neuritic outgrowth from goldfish retinal explants.

PubMed

Cubillán, Lisbeth; Obregón, Francisco; Lima, Lucimey

2009-01-01

Taurine stimulates outgrowth of goldfish retinal explants in a concentration- and time-dependent manner, an effect related to calcium movement and protein phosphorylation. Since taurine is an osmoregulator in the central nervous system, and osmolality might influence regeneration, the purpose of this work was to evaluate the possible effect of hypo-osmolality on basal outgrowth and on the trophic action of the amino acid. Accordingly, goldfish retinal explants obtained after crushing the optic nerve were cultured in iso- and hypo-osmotic medium, the latter achieved by diluting the medium 10% 24 and 72 h after plating. The length and density of the neurites, measured after 5 days in culture, were significantly lower in the hypo- than in the iso-osmotic medium. Taurine stimulated the outgrowth under both conditions, but the percentage of increase was greater in iso-osmotic medium. Taurine concentration, determined by HPLC, did not significantly change in explants. Co-administration of beta-alanine and taurine impaired the trophic effect of taurine to a greater extent in the iso- than in hypo-osmotic medium, indicating a possible differential interaction with the taurine transporter which could be altered by osmotic stress. The exact mechanism of outgrowth regulation by hypotonicity requires further clarification, taking into considering possible modification of the taurine transporter.

Hypoxia tolerance of common sole juveniles depends on dietary regime and temperature at the larval stage: evidence for environmental conditioning.

PubMed

Zambonino-Infante, José L; Claireaux, Guy; Ernande, Bruno; Jolivet, Aurélie; Quazuguel, Patrick; Sévère, Armelle; Huelvan, Christine; Mazurais, David

2013-05-07

An individual's environmental history may have delayed effects on its physiology and life history at later stages in life because of irreversible plastic responses of early ontogenesis to environmental conditions. We chose a marine fish, the common sole, as a model species to study these effects, because it inhabits shallow marine areas highly exposed to environmental changes. We tested whether temperature and trophic conditions experienced during the larval stage had delayed effects on life-history traits and resistance to hypoxia at the juvenile stage. We thus examined the combined effect of global warming and hypoxia in coastal waters, which are potential stressors to many estuarine and coastal marine fishes. Elevated temperature and better trophic conditions had a positive effect on larval growth and developmental rates; warmer larval temperature had a delayed positive effect on body mass and resistance to hypoxia at the juvenile stage. The latter suggests a lower oxygen demand of individuals that had experienced elevated temperatures during larval stages. We hypothesize that an irreversible plastic response to temperature occurred during early ontogeny that allowed adaptive regulation of metabolic rates and/or oxygen demand with long-lasting effects. These results could deeply affect predictions about impacts of global warming and eutrophication on marine organisms.

In vivo blockade of acetylcholinesterase increases intraovarian acetylcholine and enhances follicular development and fertility in the rat.

PubMed

Urra, Javier; Blohberger, Jan; Tiszavari, Michelle; Mayerhofer, Artur; Lara, Hernan E

2016-07-21

Growth and differentiation of ovarian follicles are regulated by systemic and local factors, which may include acetylcholine (ACh). Granulosa cells (GCs) of growing follicles and luteal cells produce ACh and in cultured GCs it exerts trophic actions via muscarinic receptors. However, such actions were not studied in vivo. After having established that rat ovarian GCs and luteal cells express the ACh-metabolizing enzyme ACh esterase (AChE), we examined the consequences of local application of an AChE inhibitor, huperzine A (HupA), by osmotic minipump delivery into the ovarian bursa of hemiovariectomized rats. Saline was used in the control group. Local delivery of HupA for 4 weeks increased ovarian ACh content. Estrus cyclicity was not changed indicating a locally restricted range of HupA action. The number of primordial and primary follicles was unaffected, but small secondary follicles significantly increased in the HupA group. Furthermore, a significant increase in the number of corpora lutea suggested increased ovulatory events. In support, as shown upon mating, HupA-treated females had significantly increased implantation sites and more pups. Thus the data are in support of a trophic role of ACh in follicular development and ovulation and point to an important role of ACh in female fertility.

In vivo blockade of acetylcholinesterase increases intraovarian acetylcholine and enhances follicular development and fertility in the rat

PubMed Central

Blohberger, Jan; Tiszavari, Michelle; Mayerhofer, Artur; Lara, Hernan E.

2016-01-01

Growth and differentiation of ovarian follicles are regulated by systemic and local factors, which may include acetylcholine (ACh). Granulosa cells (GCs) of growing follicles and luteal cells produce ACh and in cultured GCs it exerts trophic actions via muscarinic receptors. However, such actions were not studied in vivo. After having established that rat ovarian GCs and luteal cells express the ACh-metabolizing enzyme ACh esterase (AChE), we examined the consequences of local application of an AChE inhibitor, huperzine A (HupA), by osmotic minipump delivery into the ovarian bursa of hemiovariectomized rats. Saline was used in the control group. Local delivery of HupA for 4 weeks increased ovarian ACh content. Estrus cyclicity was not changed indicating a locally restricted range of HupA action. The number of primordial and primary follicles was unaffected, but small secondary follicles significantly increased in the HupA group. Furthermore, a significant increase in the number of corpora lutea suggested increased ovulatory events. In support, as shown upon mating, HupA-treated females had significantly increased implantation sites and more pups. Thus the data are in support of a trophic role of ACh in follicular development and ovulation and point to an important role of ACh in female fertility. PMID:27440195

Variability in organic carbon reactivity across lake residence time and trophic gradients

NASA Astrophysics Data System (ADS)

Evans, Chris D.; Futter, Martyn N.; Moldan, Filip; Valinia, Salar; Frogbrook, Zoe; Kothawala, Dolly N.

2017-11-01

The transport of dissolved organic carbon from land to ocean is a large dynamic component of the global carbon cycle. Inland waters are hotspots for organic matter turnover, via both biological and photochemical processes, and mediate carbon transfer between land, oceans and atmosphere. However, predicting dissolved organic carbon reactivity remains problematic. Here we present in situ dissolved organic carbon budget data from 82 predominantly European and North American water bodies with varying nutrient concentrations and water residence times ranging from one week to 700 years. We find that trophic status strongly regulates whether water bodies act as net dissolved organic carbon sources or sinks, and that rates of both dissolved organic carbon production and consumption can be predicted from water residence time. Our results suggest a dominant role of rapid light-driven removal in water bodies with a short water residence time, whereas in water bodies with longer residence times, slower biotic production and consumption processes are dominant and counterbalance one another. Eutrophication caused lakes to transition from sinks to sources of dissolved organic carbon. We conclude that rates and locations of dissolved organic carbon processing and associated CO2 emissions in inland waters may be misrepresented in global carbon budgets if temporal and spatial reactivity gradients are not accounted for.

Bioaccumulation and biomagnification of emerging bisphenol analogues in aquatic organisms from Taihu Lake, China.

PubMed

Wang, Qiang; Chen, Meng; Shan, Guoqiang; Chen, Pengyu; Cui, Shuo; Yi, Shujun; Zhu, Lingyan

2017-11-15

Due to regulations on bisphenol A (BPA) in many countries, a variety of bisphenol analogues are being widely manufactured and applied. However, there is a big knowledge gap on bioaccumulation and biomagnification of these emerging bisphenols in aquatic organisms. The bioaccumulation and magnification of nine bisphenol analogues in aquatic organisms at different trophic levels collected from Taihu Lake, China, were evaluated. The total concentrations of the nine bisphenols in the lake waters were in the range of 49.7-3480ng/L (mean, 389ng/L). BPA, bisphenol AF (BPAF) and bisphenol S (BPS) were the most predominant analogues in the water. The mean natural logarithm bioaccumulation factor (log BAFs) of BPAF, bisphenol C (BPC), bisphenol Z (BPZ) and bisphenol E (BPE) were greater than BPA, and there was a significantly positive correlation between log BAFs of the biphenols and their octanol-water partition coefficients (log K ow ). The trophic magnification factors of BPAF, BPC and BPZ were 2.52, 2.69 and 1.71, respectively, suggesting that they had the potential to biomagnify in the food web. The results of this study call for further investigations on risk assessment of these emerging pollutants in the environment. Copyright © 2017 Elsevier B.V. All rights reserved.

Water-quality, phytoplankton, and trophic-status characteristics of Big Base and Little Base lakes, Little Rock Air Force Base, Arkansas, 2003-2004

USGS Publications Warehouse

Justus, B.G.

2005-01-01

Little Rock Air Force Base is the largest C-130 base in the Air Force and is the only C-130 training base in the Department of Defense. Little Rock Air Force Base is located in central Arkansas near the eastern edge of the Ouachita Mountains, near the Mississippi Alluvial Plain, and within the Arkansas Valley Ecoregion. Habitats include upland pine forests, upland deciduous forest, broad-leaved deciduous swamps, and two small freshwater lakes?Big Base Lake and Little Base Lake. Big Base and Little Base Lakes are used primarily for recreational fishing by base personnel and the civilian public. Under normal (rainfall) conditions, Big Base Lake has a surface area of approximately 39 acres while surface area of Little Base Lake is approximately 1 acre. Little Rock Air Force Base personnel are responsible for managing the fishery in these two lakes and since 1999 have started a nutrient enhancement program that involves sporadically adding fertilizer to Big Base Lake. As a means of determining the relations between water quality and primary production, Little Rock Air Force Base personnel have a need for biological (phytoplankton density), chemical (dissolved-oxygen and nutrient concentrations), and physical (water temperature and light transparency) data. To address these monitoring needs, the U.S. Geological Survey in cooperation with Little Rock Air Force Base, conducted a study to collect and analyze biological, chemical, and physical data. The U.S. Geological Survey sampled water quality in Big Base Lake and Little Base Lake on nine occasions from July 2003 through June 2004. Because of the difference in size, two sampling sites were established on Big Base Lake, while only one site was established on Little Base Lake. Lake profile data for Big Base Lake indicate that low dissolved- oxygen concentrations in the hypolimnion probably constrain most fish species to the upper 5-6 feet of depth during the summer stratification period. Dissolved-oxygen concentrations in Big Base Lake below a depth of 6 feet generally were less than 3 milligrams per liter for summer months that were sampled in 2003 and 2004. Some evidence indicates that phosphorus was limiting primary production during the sampling period. Dissolved nitrogen constituents frequently were detected in water samples (indicating availability) but dissolved phosphorus constituents-orthophosphorus and dissolved phosphorus-were not detected in any samples collected at the two lakes. The absence of dissolved phosphorus constituents and presence of total phosphorus indicates that all phosphorus was bound to suspended material (sediment particles and living organisms). Nitrogen:phosphorus ratios on most sampling occasions tended to be slightly higher than 16:1, which can be interpreted as further indication that phosphorus could be limiting primary production to some extent. An alkalinity of 20 milligrams per liter of calcium carbonate or higher is recommended to optimize nutrient availability and buffering capacity in recreational fishing lakes and ponds. Median values for water samples collected at the three sites ranged from 12-13 milligrams per liter of calcium carbonate. Alkalinities ranged from 9-60 milligrams per liter of calcium carbonate, but 13 of 17 samples collected at the deepest site had alkalinities less than 20 milligrams per liter of calcium carbonate. Results of three trophic-state indices, and a general trophic classification, as well as abundant green algae and large growths of blue-green algae indicate that Big Base Lake may be eutrophic. Trophic-state index values calculated using total phosphorus, chlorophyll a, and Secchi disc measurements from both lakes generally exceeded criteria at which lakes are considered to be eutrophic. A second method of determining lake trophic status-the general trophic classification-categorized the three sampling sites as mesotrophic or eutrophic. Green algae were found to be in abundance throughout mos

Trophic Pathways of the Mid-North Atlantic

EPA Science Inventory

Because deep-sea fisheries are increasing as coastal fisheries decline, fisheries scientists need baseline data on deep-sea ecosystems prior to further development of deep-water fisheries. We present preliminary results and ongoing efforts to characterize the trophic structure a...

Mercury biomagnification and the trophic structure of the ichthyofauna from a remote lake in the Brazilian Amazon.

PubMed

Azevedo-Silva, Claudio Eduardo; Almeida, Ronaldo; Carvalho, Dario P; Ometto, Jean P H B; de Camargo, Plínio B; Dorneles, Paulo R; Azeredo, Antonio; Bastos, Wanderley R; Malm, Olaf; Torres, João P M

2016-11-01

The present study assesses mercury biomagnification and the trophic structure of the ichthyofauna from the Puruzinho Lake, Brazilian Amazon. In addition to mercury determination, the investigation comprised the calculation of Trophic Magnification Factor (TMF) and Trophic Magnification Slope (TMS), through the measurements of stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) in fish samples. These assessments were executed in two different scenarios, i.e., considering (1) all fish species or (2) only the resident fish (excluding the migratory species). Bottom litter, superficial sediment and seston were the sources used for generating the trophic position (TP) data used in the calculation of the TMF. Samples from 84 fish were analysed, comprising 13 species, which were categorized into four trophic guilds: iliophagous, planktivorous, omnivorous and piscivorous fish. The δ 13 C values pointed to the separation of the ichthyofauna into two groups. One group comprised iliophagous and planktivorous species, which are linked to the food chains of phytoplankton and detritus. The other group was composed by omnivorous and piscivorous fish, which are associated to the trophic webs of phytoplankton, bottom litter, detritus, periphyton, as well as to food chains of igapó (blackwater-flooded Amazonian forests). The TP values suggest that the ichthyofauna from the Puruzinho Lake is part of a short food web, with three well-characterized trophic levels. Mercury concentrations and δ 13 C values point to multiple sources for Hg input and transfer. The similarity in Hg levels and TP values between piscivorous and planktivorous fish suggests a comparable efficiency for the transfer of this metal through pelagic and littoral food chains. Regarding the two abovementioned scenarios, i.e., considering (1) the entire ichthyofauna and (2) only the resident species, the TMF values were 5.25 and 4.49, as well as the TMS values were 0.21 and 0.19, respectively. These findings confirm that Hg biomagnifies through the food web of Puruzinho Lake ichthyofauna. The migratory species did not significantly change mercury biomagnification rate in Puruzinho Lake; however, they may play a relevant role in Hg transport. The biomagnification rate (TMS value) in Puruzinho Lake was higher than the average values for its latitude, being comparable to TMS values of temperate and polar systems (marine and freshwater environments). Copyright © 2016 Elsevier Inc. All rights reserved.

The Mediterranean and Black Sea Fisheries at Risk from Overexploitation

PubMed Central

Tsikliras, Athanassios C.; Dinouli, Anny; Tsiros, Vasileios-Zikos; Tsalkou, Eleni

2015-01-01

The status of the Mediterranean and Black Sea fisheries was evaluated for the period 1970-2010 on a subarea basis, using various indicators including the temporal variability of total landings, the number of recorded stocks, the mean trophic level of the catch, the fishing-in-balance index and the catch-based method of stock classification. All indicators confirmed that the fisheries resources of the Mediterranean and Black Sea are at risk from overexploitation. The pattern of exploitation and the state of stocks differed among the western (W), central (C) and eastern (E) Mediterranean subareas and the Black Sea (BS), with the E Mediterranean and BS fisheries being in a worst shape. Indeed, in the E Mediterranean and the BS, total landings, mean trophic level of the catch and fishing-in-balance index were declining, the cumulative percentage of overexploited and collapsed stocks was higher, and the percentage of developing stocks was lower, compared to the W and C Mediterranean. Our results confirm the need for detailed and extensive stock assessments across species that will eventually lead to stocks recovering through conservation and management measures. PMID:25793975

Role of aryl hydrocarbon receptor in mesenchymal stromal cell activation: A minireview.

PubMed

de Almeida, Danilo Candido; Evangelista, Laura Sibele Martins; Câmara, Niels Olsen Saraiva

2017-09-26

Mesenchymal stromal cells (MSCs) possess great therapeutic advantages due to their ability to produce a diverse array of trophic/growth factors related to cytoprotection and immunoregulation. MSC activation via specific receptors is a crucial event for these cells to exert their immunosuppressive response. The aryl-hydrocarbon receptor (AhR) is a sensitive molecule for external signals and it is expressed in MSCs and, upon positive activation, may potentially regulate the MSC-associated immunomodulatory function. Consequently, signalling pathways linked to AhR activation can elucidate some of the molecular cascades involved in MSC-mediated immunosuppression. In this minireview, we have noted some important findings concerning MSC regulation via AhR, highlighting that its activation is associated with improvement in migration and immunoregulation, as well as an increase in pro-regenerative potential. Thus, AhR-mediated MSC activation can contribute to new perspectives on MSC-based therapies, particularly those directed at immune-associated disorders.

Surveillance, Phagocytosis, and Inflammation: How Never-Resting Microglia Influence Adult Hippocampal Neurogenesis

PubMed Central

Sierra, Amanda; Beccari, Sol; Diaz-Aparicio, Irune; Encinas, Juan M.; Comeau, Samuel; Tremblay, Marie-Ève

2014-01-01

Microglia cells are the major orchestrator of the brain inflammatory response. As such, they are traditionally studied in various contexts of trauma, injury, and disease, where they are well-known for regulating a wide range of physiological processes by their release of proinflammatory cytokines, reactive oxygen species, and trophic factors, among other crucial mediators. In the last few years, however, this classical view of microglia was challenged by a series of discoveries showing their active and positive contribution to normal brain functions. In light of these discoveries, surveillant microglia are now emerging as an important effector of cellular plasticity in the healthy brain, alongside astrocytes and other types of inflammatory cells. Here, we will review the roles of microglia in adult hippocampal neurogenesis and their regulation by inflammation during chronic stress, aging, and neurodegenerative diseases, with a particular emphasis on their underlying molecular mechanisms and their functional consequences for learning and memory. PMID:24772353

Quorum Sensing in Marine Microbial Environments.

PubMed

Hmelo, Laura R

2017-01-03

Quorum sensing (QS) is a form of chemical communication used by certain bacteria that regulates a wide range of biogeochemically important bacterial behaviors. Although QS was first observed in a marine bacterium nearly four decades ago, only in the past decade has there been a rise in interest in the role that QS plays in the ocean. It has become clear that QS, regulated by signals such as acylated homoserine lactones (AHLs) or furanosyl-borate diesters [autoinducer-2 (AI-2) molecules], is involved in important processes within the marine carbon cycle, in the health of coral reef ecosystems, and in trophic interactions between a range of eukaryotes and their bacterial associates. The most well-studied QS systems in the ocean occur in surface-attached (biofilm) communities and rely on AHL signaling. AHL-QS is highly sensitive to the chemical and biological makeup of the environment and may respond to anthropogenic change, including ocean acidification and rising sea surface temperatures.

Gut microbiota and obesity.

PubMed

Scarpellini, Emidio; Campanale, Mariachiara; Leone, Diana; Purchiaroni, Flaminia; Vitale, Giovanna; Lauritano, Ernesto Cristiano; Gasbarrini, Antonio

2010-10-01

Intestinal epithelium, mucosal immune system, and bacterial flora represent a morpho-functional system on dynamic balance responsible for the intestinal metabolic and trophic functions, and the regulation of mucosal and systemic host's immunity. Obesity is a pathological condition affecting a growing number of people especially in the Western countries resulting from the failure of the organism's energetic balance based on the perfect equality of income, waste, and storage. Recent evidences explain the mechanisms for the microbial regulation of the host's metabolism both in health and disease. In particular, animal studies have explained how quali-/quantitative changes in microflora composition are able to affect the absorption of the nutrients and the energy distribution. Antibiotics, prebiotics, probiotics, and symbiotics are the instruments utilized in the current clinical practice to modulate the intestinal bacterial flora in man both in health and pathologic conditions with promising preliminary results on prevention and therapy of obesity and related metabolic diseases.

Quorum Sensing in Marine Microbial Environments

NASA Astrophysics Data System (ADS)

Hmelo, Laura R.

2017-01-01

Quorum sensing (QS) is a form of chemical communication used by certain bacteria that regulates a wide range of biogeochemically important bacterial behaviors. Although QS was first observed in a marine bacterium nearly four decades ago, only in the past decade has there been a rise in interest in the role that QS plays in the ocean. It has become clear that QS, regulated by signals such as acylated homoserine lactones (AHLs) or furanosyl-borate diesters [autoinducer-2 (AI-2) molecules], is involved in important processes within the marine carbon cycle, in the health of coral reef ecosystems, and in trophic interactions between a range of eukaryotes and their bacterial associates. The most well-studied QS systems in the ocean occur in surface-attached (biofilm) communities and rely on AHL signaling. AHL-QS is highly sensitive to the chemical and biological makeup of the environment and may respond to anthropogenic change, including ocean acidification and rising sea surface temperatures.

[Use of magnetic therapy combined with galvanization and tissue electrophoresis in the treatment of trophic ulcers].

PubMed

Alekseenko, A V; Gusak, V V; Stoliar, V F; Iftodiĭ, A G; Tarabanchuk, V V; Shcherban, N G; Naumets, A A

1993-01-01

The results of treatment of 86 patients with the use of magnetotherapy in combination with galvanization and intratissue electrophoresis are presented. To create an electric field, the "Potok-1" apparatus with a density of current equal to 0.05-0.1 mA/cm2 was employed. Simultaneously, the "MAG-30" apparatus for low-frequency magnetotherapy with induction of 30 mT and area of exposure of 20 cm2 was applied to a trophic ulcer site. The use of magnetogalvanotherapy in the complex of treatment of trophic ulcers of the lower extremities is recommended.

[THE CORRECTION OF TROPHIC DISORDERS IN CHILDREN OF CHRONIC GASTRODUODENITIS WITH METHOD LOW-FREQUENCY LIGHT-MAGNETOTHERAPY].

PubMed

Kolosova, T A; Sadovnikova, I V; Belousova, T E

2015-01-01

The results of a survey of school children with chronic gastroduodenitis when applying at an early period the medical rehabilitation with method low-frequency light-magnetotherapy. During treatment of hospital was evaluated vegetative-trophic status with methods of cardiointervalography and thermovision functional tests. In normalizes clinical parameters was correction in dynamics of the vegetative status in children, it confirms the effectiveness of the therapy. It is proved, that the use of low-frequency light-magnetotherapy has a positive effect on the vegetative--trophic provision an organism and normalizes the vegetative dysfunction.

Dietary biomagnification of organochlorine contaminants in Alaskan polar bears

USGS Publications Warehouse

Bentzen, T.W.; Follmann, Erich H.; Amstrup, Steven C.; York, G.S.; Wooller, M.J.; Muir, D.C.G.; O'Hara, T. M.

2008-01-01

Concentrations of organochlorine contaminants in the adipose tissue of polar bears (Ursus maritimus Phipps, 1774) vary throughout the Arctic. The range in concentrations has not been explained fully by bear age, sex, condition, location, or reproductive status. Dietary pathways expose polar bears to a variety of contaminant profiles and concentrations. Prey range from lower trophic level bowhead whales (Balaena mysticetus L., 1758), one of the least contaminated marine mammals, to highly contaminated upper trophic level ringed seals (Phoca hispida (Schreber, 1775)). We used ??15N and ??13C signatures to estimate the trophic status of 42 polar bears sampled along Alaska's Beaufort Sea coast to determine the relationship between organochlorine concentration and trophic level. The ?? 15N values in the cellular portions of blood ranged from 18.2% to 20.7%. We found strong positive relationships between concentrations of the most recalcitrant polychlorinated biphenyls (PCBs) and ??15N values in models incorporating age, lipid content, and ??13C value. Specifically these models accounted for 67% and 76% of the variation in PCB153 and oxychlordane concentration in male polar bears and 85% and 93% in females, respectively. These results are strong indicators of variation in diet and biomagnification of organochlorines among polar bears related to their sex, age, and trophic position. ?? 2008 NRC.

Population-Scale Foraging Segregation in an Apex Predator of the North Atlantic

PubMed Central

Paiva, Vitor H.; Fagundes, Ana I.; Romão, Vera; Gouveia, Cátia; Ramos, Jaime A.

2016-01-01

In this work we investigated the between-colony spatial, behavioural and trophic segregation of two sub-populations of the elusive Macaronesian shearwaters Puffinus baroli breeding only ~340 km apart in Cima Islet (Porto Santo Island) and Selvagem Grande Island. Global location sensing (gls) loggers were used in combination with the trophic ecology of tracked individuals, inferred from the isotopic signatures of wing feathers. Results suggest that these two Macaronesian shearwater sub-populations do segregate during the non-breeding period in some ‘sub-population-specific’ regions, by responding to different oceanographic characteristics (habitat modelling). Within these disparate areas, both sub-populations behave differently (at-sea activity) and prey on disparate trophic niches (stable isotope analysis). One hypothesis would be that each sub-population have evolved and adapted to feed on particular and ‘sub-population-specific’ resources, and the segregation observed at the three different levels (spatial, behavioural and trophic) might be in fact a result of such adaptation, from the emergence of ‘cultural foraging patterns’. Finally, when comparing to the results of former studies reporting on the spatial, behavioural and trophic choices of Macaronesian shearwater populations breeding on Azores and Canary Islands, we realized the high ecological plasticity of this species inhabiting and foraging over the North-East Atlantic Ocean. PMID:27003687

Boosted food web productivity through ocean acidification collapses under warming.

PubMed

Goldenberg, Silvan U; Nagelkerken, Ivan; Ferreira, Camilo M; Ullah, Hadayet; Connell, Sean D

2017-10-01

Future climate is forecast to drive bottom-up (resource driven) and top-down (consumer driven) change to food web dynamics and community structure. Yet, our predictive understanding of these changes is hampered by an over-reliance on simplified laboratory systems centred on single trophic levels. Using a large mesocosm experiment, we reveal how future ocean acidification and warming modify trophic linkages across a three-level food web: that is, primary (algae), secondary (herbivorous invertebrates) and tertiary (predatory fish) producers. Both elevated CO 2 and elevated temperature boosted primary production. Under elevated CO 2 , the enhanced bottom-up forcing propagated through all trophic levels. Elevated temperature, however, negated the benefits of elevated CO 2 by stalling secondary production. This imbalance caused secondary producer populations to decline as elevated temperature drove predators to consume their prey more rapidly in the face of higher metabolic demand. Our findings demonstrate how anthropogenic CO 2 can function as a resource that boosts productivity throughout food webs, and how warming can reverse this effect by acting as a stressor to trophic interactions. Understanding the shifting balance between the propagation of resource enrichment and its consumption across trophic levels provides a predictive understanding of future dynamics of stability and collapse in food webs and fisheries production. © 2017 John Wiley & Sons Ltd.

Trophic transfer efficiency of methylmercury and inorganic mercury to lake trout Salvelinus namaycush from its prey

USGS Publications Warehouse

Madenijian, C.P.; David, S.R.; Krabbenhoft, D.P.

2012-01-01

Based on a laboratory experiment, we estimated the net trophic transfer efficiency of methylmercury to lake trout Salvelinus namaycush from its prey to be equal to 76.6 %. Under the assumption that gross trophic transfer efficiency of methylmercury to lake trout from its prey was equal to 80 %, we estimated that the rate at which lake trout eliminated methylmercury was 0.000244 day−1. Our laboratory estimate of methylmercury elimination rate was 5.5 times lower than the value predicted by a published regression equation developed from estimates of methylmercury elimination rates for fish available from the literature. Thus, our results, in conjunction with other recent findings, suggested that methylmercury elimination rates for fish have been overestimated in previous studies. In addition, based on our laboratory experiment, we estimated that the net trophic transfer efficiency of inorganic mercury to lake trout from its prey was 63.5 %. The lower net trophic transfer efficiency for inorganic mercury compared with that for methylmercury was partly attributable to the greater elimination rate for inorganic mercury. We also found that the efficiency with which lake trout retained either methylmercury or inorganic mercury from their food did not appear to be significantly affected by the degree of their swimming activity.

Trophic characteristics of a mangrove fish community in Southwest Thailand: Important mangrove contribution and intraspecies feeding variability

NASA Astrophysics Data System (ADS)

Zagars, Matiss; Ikejima, Kou; Kasai, Akihide; Arai, Nobuaki; Tongnunui, Prasert

2013-03-01

Mangrove production has been found to make a major contribution to the nutrition of a fish community in the Sikao Creek mangrove estuary, Southwest Thailand. Gut content analysis and carbon and nitrogen stable isotope analysis were used to assess fish feeding behavior and trophic reliance on different primary producers (mangrove leaves, phytoplankton, microphytobenthos) focusing on 19 dominant fish species, and 4 potential fish food items. Cluster analysis identified 5 trophic groups and the IsoSource model indicated the importance of primary food sources in trophically supporting different fish species. Most analyzed fish species had carbon isotopic signatures that were more depleted than those reported in previous studies, and the IsoSource model indicated that mangrove leaves were an important primary food source. This may be a specific characteristic of our study site, which is not well connected to other productive coastal habitats that provide alternative primary food sources. Thus we suggest that food chains in trophically isolated mangrove estuaries of southwest Thailand are more dependent on mangrove tree production. We also assessed the relationship of individuality in fish feeding habits and variability of δ13C values and showed that several mangrove fish species have significant intraspecies variability in feeding habits, possibly due to high intraspecific competition.

Resetting predator baselines in coral reef ecosystems

PubMed Central

Bradley, Darcy; Conklin, Eric; Papastamatiou, Yannis P.; McCauley, Douglas J.; Pollock, Kydd; Pollock, Amanda; Kendall, Bruce E.; Gaines, Steven D.; Caselle, Jennifer E.

2017-01-01

What did coral reef ecosystems look like before human impacts became pervasive? Early efforts to reconstruct baselines resulted in the controversial suggestion that pristine coral reefs have inverted trophic pyramids, with disproportionally large top predator biomass. The validity of the coral reef inverted trophic pyramid has been questioned, but until now, was not resolved empirically. We use data from an eight-year tag-recapture program with spatially explicit, capture-recapture models to re-examine the population size and density of a key top predator at Palmyra atoll, the same location that inspired the idea of inverted trophic biomass pyramids in coral reef ecosystems. Given that animal movement is suspected to have significantly biased early biomass estimates of highly mobile top predators, we focused our reassessment on the most mobile and most abundant predator at Palmyra, the grey reef shark (Carcharhinus amblyrhynchos). We estimated a density of 21.3 (95% CI 17.8, 24.7) grey reef sharks/km2, which is an order of magnitude lower than the estimates that suggested an inverted trophic pyramid. Our results indicate that the trophic structure of an unexploited reef fish community is not inverted, and that even healthy top predator populations may be considerably smaller, and more precarious, than previously thought. PMID:28220895

Stable isotopes document the trophic structure of a deep-sea cephalopod assemblage including giant octopod and giant squid.

PubMed

Cherel, Y; Ridoux, V; Spitz, J; Richard, P

2009-06-23

Although deep-sea cephalopods are key marine organims, their feeding ecology remains essentially unknown. Here, we report for the first time the trophic structure of an assemblage of these animals (19 species) by measuring the isotopic signature of wings of their lower beaks, which accumulated in stomachs of stranded sperm whales. Overall, the species encompassed a narrow range in delta(13)C values (1.7 per thousand), indicating that they lived in closely related and overlapping habitats. delta(13)C values can be interpreted in terms of distribution with the more (13)C-depleted species (e.g. Stigmatoteuthis arcturi, Vampyroteuthis infernalis) having a more pelagic habitat than the more (13)C-enriched, bathyal species (e.g. Todarodes sagittatus and the giant squid Architeuthis dux). The cephalopods sampled had delta(15)N values ranging 4.6 per thousand, which is consistent with the species spanning approximately 1.5 trophic levels. Neither the giant octopod (Haliphron atlanticus) nor the giant squid reached the highest trophic position. Species delta(15)N was independent of body size, with large squids having both the highest (Taningia danae) and lowest (Lepidoteuthis grimaldii) delta(15)N values. Their trophic position indicates that some species share the top of the food web, together with other megacarnivores such as the sperm whale.

At limits of life: multidisciplinary insights reveal environmental constraints on biotic diversity in continental Antarctica.

PubMed

Magalhães, Catarina; Stevens, Mark I; Cary, S Craig; Ball, Becky A; Storey, Bryan C; Wall, Diana H; Türk, Roman; Ruprecht, Ulrike

2012-01-01

Multitrophic communities that maintain the functionality of the extreme Antarctic terrestrial ecosystems, while the simplest of any natural community, are still challenging our knowledge about the limits to life on earth. In this study, we describe and interpret the linkage between the diversity of different trophic level communities to the geological morphology and soil geochemistry in the remote Transantarctic Mountains (Darwin Mountains, 80°S). We examined the distribution and diversity of biota (bacteria, cyanobacteria, lichens, algae, invertebrates) with respect to elevation, age of glacial drift sheets, and soil physicochemistry. Results showed an abiotic spatial gradient with respect to the diversity of the organisms across different trophic levels. More complex communities, in terms of trophic level diversity, were related to the weakly developed younger drifts (Hatherton and Britannia) with higher soil C/N ratio and lower total soluble salts content (thus lower conductivity). Our results indicate that an increase of ion concentration from younger to older drift regions drives a succession of complex to more simple communities, in terms of number of trophic levels and diversity within each group of organisms analysed. This study revealed that integrating diversity across multi-trophic levels of biotic communities with abiotic spatial heterogeneity and geological history is fundamental to understand environmental constraints influencing biological distribution in Antarctic soil ecosystems.

Decline in top predator body size and changing climate alter trophic structure in an oceanic ecosystem.

PubMed

Shackell, Nancy L; Frank, Kenneth T; Fisher, Jonathan A D; Petrie, Brian; Leggett, William C

2010-05-07

Globally, overfishing large-bodied groundfish populations has resulted in substantial increases in their prey populations. Where it has been examined, the effects of overfishing have cascaded down the food chain. In an intensively fished area on the western Scotian Shelf, Northwest Atlantic, the biomass of prey species increased exponentially (doubling time of 11 years) even though the aggregate biomass of their predators remained stable over 38 years. Concomitant reductions in herbivorous zooplankton and increases in phytoplankton were also evident. This anomalous trophic pattern led us to examine how declines in predator body size (approx. 60% in body mass since the early 1970s) and climatic regime influenced lower trophic levels. The increase in prey biomass was associated primarily with declines in predator body size and secondarily to an increase in stratification. Sea surface temperature and predator biomass had no influence. A regression model explained 65 per cent of prey biomass variability. Trait-mediated effects, namely a reduction in predator size, resulted in a weakening of top predation pressure. Increased stratification may have enhanced growing conditions for prey fish. Size-selective harvesting under changing climatic conditions initiated a trophic restructuring of the food chain, the effects of which may have influenced three trophic levels.

The exploration of trophic structure modeling using mass balance Ecopath model of Tangerang coastal waters

NASA Astrophysics Data System (ADS)

Dewi, N. N.; Kamal, M.; Wardiatno, Y.; Rozi

2018-04-01

Ecopath model approach was used to describe trophic interaction, energy flows and ecosystem condition of Tangerang coastal waters. This model consists of 42 ecological groups, of which 41 are living groups and one is a detritus group. Trophic levels of these groups vary between 1.0 (for primary producers and detritus) to 4.03 (for tetraodontidae). Groups with trophic levels 2≤TL<3 and 3≤TL<4 have a range of ecotropic efficiency from 0 to 0.9719 and 0 to 0.7520 respectively.The Mean transfer efficiency is 9.43% for phytoplankton and 3.39% for detritus. The Mixed trophic impact analysis indicates that phytoplankton havea positive impact on the majority of pelagic fish, while detritus has a positive impact on the majority of demersal fish. Leiognathidae havea negative impact on phytoplankton, zooplankton and several other groups. System omnivory index for this ecosystem is 0.151. System primary production/respiration (P/R) ratio of Tangerang coastal waters is 1.505. This coastal ecosystem is an immatureecosystem because it hasdegraded. Pedigree index for this model is 0.57. This model describes ecosystem condition affected by overfishing and antropogenic activities. Therefore, through Ecopath model we provide some suggestions about the ecosystem-based fisheries management.

Taurine and its neuroprotective role.

PubMed

Kumari, Neeta; Prentice, Howard; Wu, Jang-Yen

2013-01-01

Taurine plays multiple roles in the CNS including acting as a -neuro-modulator, an osmoregulator, a regulator of cytoplasmic calcium levels, a trophic factor in development, and a neuroprotectant. In neurons taurine has been shown to prevent mitochondrial dysfunction and to protect against endoplasmic reticulum (ER) stress associated with neurological disorders. In cortical neurons in culture taurine protects against excitotoxicity through reversing an increase in levels of key ER signaling components including eIF-2-alpha and cleaved ATF6. The role of communication between the ER and mitochondrion is also important and examples are presented of protection by taurine against ER stress together with prevention of subsequent mitochondrial initiated apoptosis.

Existence of muscarinic acetylcholine receptor (mAChR) and fibroblast growth factor receptor (FGFR) heteroreceptor complexes and their enhancement of neurite outgrowth in neural hippocampal cultures.

PubMed

Di Liberto, V; Borroto-Escuela, D O; Frinchi, M; Verdi, V; Fuxe, K; Belluardo, N; Mudò, G

2017-02-01

Recently, it was demonstrated that G-protein-coupled receptors (GPCRs) can transactivate tyrosine kinase receptors in absence of their ligands. In this work, driven by the observation that mAChRs and fibroblast growth factor receptors (FGFRs) share signalling pathways and regulation of brain functions, it was decided to explore whether mAChRs activation may transactivate FGFRs and, if so, to characterize the related trophic effects in cultured hippocampal neurons. Oxotremorine-M transactivation of FGFRs and related trophic effects were tested in primary hippocampal neurons. Western blotting and in situ proximity ligation assay (PLA) were used to detect FGFR phosphorylation (pFGFR) levels and M 1 R-FGFR1 heteroreceptor complexes, respectively. Oxotremorine-M, a non-selective mAChRs agonist, was able to transactivate FGFR and this transactivation was blocked by Src inhibitors. Oxotremorine-M treatment produced a significant increase in the primary neurite outgrowth that was blocked by pre-treatment with the pFGFR inhibitor SU5402 and Src inhibitors. This trophic effect was almost similar to that induced by fibroblast growth factor-2 (FGF-2). By using atropine as nonselective mAChRs or pirenzepine as selective antagonist for M 1 receptor (M 1 R) we could show that mAChRs are involved in modulating the pFGFRs. Using PLA, M 1 R-FGFR1 heteroreceptor complexes were identified in the hippocampus and cerebral cortex. The current findings, by showing functional mAChR-FGFR interactions, will contribute to advance the understanding of the mechanisms involved in the actions of cholinergic drugs on neuronal plasticity. Data may help to develop novel therapeutic strategies not only for neurodegenerative diseases but also for depression-induced atrophy of hippocampal neurons. Copyright © 2016 Elsevier B.V. All rights reserved.

Zooplanktivory and nutrient regeneration by invertebrate (Mysis relicta) and vertebrate (Oncorhynchus nerka) planktivores: Implications for trophic interactions in oligotrophic lakes

USGS Publications Warehouse

Chipps, S.R.; Bennett, D.H.

2000-01-01

We investigated zooplanktivory and nutrient regeneration by the opossum shrimp Mysis relicta and kokanee Oncorhynchus nerka to assess the relative roles of these planktivores in oligotrophic food webs. Using bioenergetic models and clearance rate estimates, we quantified phosphorus (P) excretion rates and consumption of cladoceran prey by Mysis and kokanees in Lake Pend Oreille, Idaho, from 1995 to 1996. Consumption of cladoceran prey by Mysis was 186 kg ?? ha-1 ?? year-1, whereas consumption by kokanees was less than one quarter as much, at 45 kg ?? ha-1 ?? year-1. Similarly, Mysis excreted approximately 0.250 kg P ?? ha-1 ?? year-1 during nighttime migrations into the upper water column, whereas P excretion by kokanees was less than one third as much, at approximately 0.070 kg P ?? ha-1 ?? year-1. On a volumetric basis, nocturnal excretion by Mysis ranged from 0.002 to 0.007 ??g P ?? L-1 ?? d-1 and accounted for less than 1% of the soluble reactive P typically measured in the upper water column of the lake. Hence, nutrient recycling by Mysis may be limited in the upper water column because of the nocturnal feeding habitats that constrain Mysis to deeper strata for much of the day. In spring and autumn months, low abundance of cladoceran prey coincided with high seasonal energy requirements of the Mysis population that were linked to timing of annual Mysis brood release and abundance of age-0 Mysis. Predation by Mysis accounted for 5-70% of daily cladoceran standing stock, supporting the notion that seasonal availability of cladocerans may be regulated by Mysis predation. In lakes where Mysis experience little predation mortality, they likely play a dominant role in food web interactions (e.g., trophic cascades) relative to planktivorous fishes. Biotic mechanisms, such as successful predator-avoidance behavior, omnivorous feeding habits, and seasonal variation in Mysisbiomass, enhance the ability of Mysis to influence food web interactions from an intermediate trophic level.

Spatial and Temporal Variations of Water Quality and Trophic Status in Xili Reservoir: a Subtropics Drinking Water Reservoir of Southeast China

NASA Astrophysics Data System (ADS)

Yunlong, Song; Zhang, Jinsong; Zhu, Jia; Li, Wang; Chang, Aimin; Yi, Tao

2017-12-01

Controlling of water quality pollution and eutrophication of reservoirs has become a very important research topic in urban drinking water field. Xili reservoir is an important water source of drinking water in Shenzhen. And its water quality has played an important role to the city’s drinking water security. A fifteen-month’s field observation was conducted from April 2013 to June 2014 in Xili reservoir, in order to analyze the temporal and spatial distribution of water quality factors and seasonal variation of trophic states. Xili reservoir was seriously polluted by nitrogen. Judged by TN most of the samples were no better than grade VI. Other water quality factor including WT, SD, pH, DO, COD, TOC, TP, Fe, silicate, turbidity, chlorophyll-a were pretty good. One-way ANOVA showed that significant difference was found in water quality factors on month (p<0.005). The spatial heterogeneity of water quality was obvious (p<0.05). The successions of water quality factors y were similar and the mainly pattern was Pre-rainy period > Latter rainy period > High temperature and rain free period > Temperature jump period > Winter drought period. Two-way ANOVA showed that months rather than locations were the key influencing factors of water quality factors succession.TLI (Σ) were about 35~52, suggesting Xili reservoir was in mycotrophic trophic states. As a result of runoff pollution, water quality at sampling sites 1 and 10 was poor. In the rainy season, near sampling sites 1 and 10, water appeared to be Light-eutrophic. The phytoplankton biomass of Xili reservoir was low. Water temperature was the main driving factor of phytoplankton succession.The 14 water quality factors were divided into five groups by factor analysis. The total interpretation rate was about 70.82%. F1 represents the climatic change represented by water temperature and organic pollution. F2 represents the concentration of nitrogen. F3 represents the phytoplankton biomass. F4 represents the sensory indexes of water body, such as turbidity, transparency.

A computer model to forecast wetland vegetation changes resulting from restoration and protection in coastal Louisiana

USGS Publications Warehouse

Visser, Jenneke M.; Duke-Sylvester, Scott M.; Carter, Jacoby; Broussard, Whitney P.

2013-01-01

The coastal wetlands of Louisiana are a unique ecosystem that supports a diversity of wildlife as well as a diverse community of commercial interests of both local and national importance. The state of Louisiana has established a 5-year cycle of scientific investigation to provide up-to-date information to guide future legislation and regulation aimed at preserving this critical ecosystem. Here we report on a model that projects changes in plant community distribution and composition in response to environmental conditions. This model is linked to a suite of other models and requires input from those that simulate the hydrology and morphology of coastal Louisiana. Collectively, these models are used to assess how alternative management plans may affect the wetland ecosystem through explicit spatial modeling of the physical and biological processes affected by proposed modifications to the ecosystem. We have also taken the opportunity to advance the state-of-the-art in wetland plant community modeling by using a model that is more species-based in its description of plant communities instead of one based on aggregated community types such as brackish marsh and saline marsh. The resulting model provides an increased level of ecological detail about how wetland communities are expected to respond. In addition, the output from this model provides critical inputs for estimating the effects of management on higher trophic level species though a more complete description of the shifts in habitat.

[Trophic structure of river fish from Corral de San Luis, Magdalena river basin, Colombia Caribbean].

PubMed

Morales, Jenny; García-Alzate, Carlos A

2016-06-01

Ecological studies of species, such as the stomach content analysis, allow us to recognize different trophic groups, the importance of trophic levels and the interrelationships among species and other members of the community. In this investigation, we studied food habits, feeding variation and trophic relationships of the fishes present in streams of the Corral de San Luis drainage, Tubará, Atlántico Department, a part of the lower Magdalena River Basin in Colombian Caribbean. Fish samples of Awaous banana, Agonostomus monticola, Andinoacara latifrons, Hyphessobrycon proteus, Poecilia gillii, Gobiomorus dormitor and Synbranchus marmoratus were obtained using a seine (2x5 m, mesh 0.5 cm), from November 2012 to October 2013. To analyze their stomach contents, we used numeric (% N), volumetric (% V) and frequency of occurrence (% FO) methods, an emptiness coefficient (C.V), index of food item importance (I.A). Besides, physical and chemical habitat parameters were recorded on site. Information obtained was processed using multivariate statistical analysis, ecological indices, and null models: canonical correspondence analysis (CCA), principal component analysis (PCA), trophic niche amplitude (Shannon-Weaver H´) and trophic overlap (Morisita-Horn). We observed significant differences on food resources consumption (K-W= 20.86; p<0.05) among the studied species. They were classified according to their food habits as omnivores with a tendency towards insectivory (A. monticola H´0.60; A. latifrons H´0.43), herbivores with a tendency towards the consumption of algae (A. banana H´0.50; P. gillii H´0.54) and carnivores with a tendency towards insectivory (H. proteus H´0.23); benthic invertebrates and microalgae were found the most important food sources. A total of 65 food items were identified in this study: 21 for A. banana (2 unique, 19 shared), 40 for A. monticola (21 unique, 19 shared), 19 for A. latifrons (5 unique, 14 shared), 6 for H. proteus (1 unique, 5 shared) and P. gillii with 28 (4 unique, 24 shared). The canonical correspondence analysis showed that water conductivity, salinity and pH were the variables that directly influenced fish community structure at the sampled sites. The null model analyses showed that the group of fishes was significantly segregated (p= 0.001) along the trophic axis, with respect to shared food items, and that the segregation was not influenced or generated by competition. The Morisita-Horn index showed false trophic overlap (similarity of about 80 %) between A. banana and P. gillii. The first component of the PCA analysis was explained mainly by phytoplankton, and component two was correlated with items of animal origin. The fishes associated with PC1 were P. gillii and A. banana, with high ingestion values of microalgae. PC2 was explained by A. monticola with high numbers of food items of animal origin. The group of fishes studied behaved as an assemblage; given that the trophic interrelationships showed false trophic overlap, and that they did not exclude one another from the ecosystems, but instead, used different food resources and different physical spaces within their habitat.

Two new species of the Phanaeus endymion species group (Coleoptera, Scarabaeidae, Scarabaeinae)

PubMed Central

Moctezuma, Victor; Sánchez-Huerta, José Luis; Halffter, Gonzalo

2017-01-01

Abstract Phanaeus bravoensis sp. n. is described from the coniferous-oak forests in the state of Guerrero, and P. huichol sp. n. from coniferous-oak forests and cloud forests in Jalisco and Nayarit. The new species are closely related to P. halffterorum and P. zoque respectively. Morphological trait combination, geographic distribution, and trophic habits show important differences among the studied species. A distribution map and an updated key to separate the species are included. PMID:29118601

78 FR 57353 - Endangered Species; File No. 14726

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-18

... gather information on their life-history, genetics, movements, behavior, and diet. Researchers are... from this sampling would help Dr. Witherington determine the trophic history of pelagic neonate and... with the trophic histories would further describe the sea turtles' home range, habitat use, residency...

Climate change could drive marine food web collapse through altered trophic flows and cyanobacterial proliferation

PubMed Central

Ullah, Hadayet; Goldenberg, Silvan U.; Fordham, Damien A.

2018-01-01

Global warming and ocean acidification are forecast to exert significant impacts on marine ecosystems worldwide. However, most of these projections are based on ecological proxies or experiments on single species or simplified food webs. How energy fluxes are likely to change in marine food webs in response to future climates remains unclear, hampering forecasts of ecosystem functioning. Using a sophisticated mesocosm experiment, we model energy flows through a species-rich multilevel food web, with live habitats, natural abiotic variability, and the potential for intra- and intergenerational adaptation. We show experimentally that the combined stress of acidification and warming reduced energy flows from the first trophic level (primary producers and detritus) to the second (herbivores), and from the second to the third trophic level (carnivores). Warming in isolation also reduced the energy flow from herbivores to carnivores, the efficiency of energy transfer from primary producers and detritus to herbivores and detritivores, and the living biomass of detritivores, herbivores, and carnivores. Whilst warming and acidification jointly boosted primary producer biomass through an expansion of cyanobacteria, this biomass was converted to detritus rather than to biomass at higher trophic levels—i.e., production was constrained to the base of the food web. In contrast, ocean acidification affected the food web positively by enhancing trophic flow from detritus and primary producers to herbivores, and by increasing the biomass of carnivores. Our results show how future climate change can potentially weaken marine food webs through reduced energy flow to higher trophic levels and a shift towards a more detritus-based system, leading to food web simplification and altered producer–consumer dynamics, both of which have important implications for the structuring of benthic communities. PMID:29315309

Diet reconstruction and resource partitioning of a Caribbean marine mesopredator using stable isotope bayesian modelling.

PubMed

Tilley, Alexander; López-Angarita, Juliana; Turner, John R

2013-01-01

The trophic ecology of epibenthic mesopredators is not well understood in terms of prey partitioning with sympatric elasmobranchs or their effects on prey communities, yet the importance of omnivores in community trophic dynamics is being increasingly realised. This study used stable isotope analysis of (15)N and (13)C to model diet composition of wild southern stingrays Dasyatis americana and compare trophic niche space to nurse sharks Ginglymostoma cirratum and Caribbean reef sharks Carcharhinus perezi on Glovers Reef Atoll, Belize. Bayesian stable isotope mixing models were used to investigate prey choice as well as viable Diet-Tissue Discrimination Factors for use with stingrays. Stingray δ(15)N values showed the greatest variation and a positive relationship with size, with an isotopic niche width approximately twice that of sympatric species. Shark species exhibited comparatively restricted δ(15)N values and greater δ(13)C variation, with very little overlap of stingray niche space. Mixing models suggest bivalves and annelids are proportionally more important prey in the stingray diet than crustaceans and teleosts at Glovers Reef, in contrast to all but one published diet study using stomach contents from other locations. Incorporating gut contents information from the literature, we suggest diet-tissue discrimination factors values of Δ(15)N ≈ 2.7‰ and Δ(13)C ≈ 0.9‰ for stingrays in the absence of validation experiments. The wide trophic niche and lower trophic level exhibited by stingrays compared to sympatric sharks supports their putative role as important base stabilisers in benthic systems, with the potential to absorb trophic perturbations through numerous opportunistic prey interactions.

Evolution of complex life cycles in trophically transmitted helminths. I. Host incorporation and trophic ascent.

PubMed

Parker, G A; Ball, M A; Chubb, J C

2015-02-01

Links between parasites and food webs are evolutionarily ancient but dynamic: life history theory provides insights into helminth complex life cycle origins. Most adult helminths benefit by sexual reproduction in vertebrates, often high up food chains, but direct infection is commonly constrained by a trophic vacuum between free-living propagules and definitive hosts. Intermediate hosts fill this vacuum, facilitating transmission to definitive hosts. The central question concerns why sexual reproduction, and sometimes even larval growth, is suppressed in intermediate hosts, favouring growth arrest at larval maturity in intermediate hosts and reproductive suppression until transmission to definitive hosts? Increased longevity and higher growth in definitive hosts can generate selection for larger parasite body size and higher fecundity at sexual maturity. Life cycle length is increased by two evolutionary mechanisms, upward and downward incorporation, allowing simple (one-host) cycles to become complex (multihost). In downward incorporation, an intermediate host is added below the definitive host: models suggest that downward incorporation probably evolves only after ecological or evolutionary perturbations create a trophic vacuum. In upward incorporation, a new definitive host is added above the original definitive host, which subsequently becomes an intermediate host, again maintained by the trophic vacuum: theory suggests that this is plausible even under constant ecological/evolutionary conditions. The final cycle is similar irrespective of its origin (upward or downward). Insights about host incorporation are best gained by linking comparative phylogenetic analyses (describing evolutionary history) with evolutionary models (examining selective forces). Ascent of host trophic levels and evolution of optimal host taxa ranges are discussed. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.

Diet and trophic level of the longnose spurdog Squalus blainville (Risso, 1826) in the deep waters of the Aegean Sea

NASA Astrophysics Data System (ADS)

Kousteni, Vasiliki; Karachle, Paraskevi K.; Megalofonou, Persefoni

2017-06-01

Knowledge of the diet and trophic level of marine predators is essential to develop an understanding of their ecological role in ecosystems. Research conducted on the trophic ecology of the deep-sea sharks is rather limited. The purpose of this study was to examine the diet of the longnose spurdog Squalus blainville, a deep-sea shark categorized as "data deficient" within its distribution range, with respect to sex, maturity, age, season and sampling location. The stomach contents of 211 specimens, captured in the Aegean (off Skyros and the Cyclades Islands) and Cretan Seas, using commercial bottom-trawlers from 2005 to 2012, were analysed. The cumulative prey curve showed that the sample size was adequate to describe the species' diet. The identified prey items belonged to five major groups: Teleostei, Crustacea, Cephalopoda, Annelida and Phanerogams. Higher diet diversity was observed in females compared to males, in immature individuals compared to mature ones, regardless of sex, and in spring and winter compared to other seasons. Age and sampling location seemed to influence both the diet diversity and trophic spectrum of the species. Feeding intensity based on the vacuity index was not significantly influenced by any of the factors examined, while the stomach filling degree was significantly influenced by all factors, except sex, showing significantly higher values in mature females compared to immature ones, in older individuals, in autumn compared to winter, and a significantly lower value in the Cyclades Islands compared to other locations. Females showed a significant larger mouth length compared to males of the same length, while no between-sex differences were found in gut morphometrics. The estimated fractional trophic level (TROPH=4.41) classified the species as carnivore with a preference for Teleostei and Cephalopoda, confirming its high trophic position.

Current-use pesticides in seawater and their bioaccumulation in polar bear-ringed seal food chains of the Canadian Arctic.

PubMed

Morris, Adam D; Muir, Derek C G; Solomon, Keith R; Letcher, Robert J; McKinney, Melissa A; Fisk, Aaron T; McMeans, Bailey C; Tomy, Gregg T; Teixeira, Camilla; Wang, Xiaowa; Duric, Mark

2016-07-01

The distribution of current-use pesticides (CUPs) in seawater and their trophodynamics were investigated in 3 Canadian Arctic marine food chains. The greatest ranges of dissolved-phase concentrations in seawater for each CUP were endosulfan sulfate (less than method detection limit (MDL) to 19 pg L(-1) ) > dacthal (0.76-15 pg L(-1) ) > chlorpyrifos (less than MDL to 8.1 pg L(-1) ) > pentachloronitrobenzene (less than MDL to 2.6 pg L(-1) ) > α-endosulfan (0.20-2.3 pg L(-1) ). Bioaccumulation factors (BAFs, water-respiring organisms) were greatest in plankton, including chlorothalonil (log BAF = 7.4 ± 7.1 L kg(-1) , mean ± standard error), chlorpyrifos (log BAF = 6.9 ± 6.7 L kg(-1) ), and α-endosulfan (log BAF = 6.5 ± 6.0 L kg(-1) ). The largest biomagnification factors (BMFs) were found for dacthal in the capelin:plankton trophic relationship (BMF = 13 ± 5.0) at Cumberland Sound (Nunvavut), and for β-endosulfan (BMF = 16 ± 4.9) and α-endosulfan (BMF = 9.3 ± 2.8) in the polar bear-ringed seal relationship at Barrow and Rae Strait (NU), respectively. Concentrations of endosulfan sulfate exhibited trophic magnification (increasing concentrations with increasing trophic level) in the poikilothermic portion of the food web (trophic magnification factor = 1.4), but all of the CUPs underwent trophic dilution in the marine mammal food web, despite some trophic level-specific biomagnification. Together, these observations are most likely indicative of metabolism of these CUPs in mammals. Environ Toxicol Chem 2016;35:1695-1707. © 2016 SETAC. © 2016 SETAC.

Trophic structure of amoeba communities near roots of Medicago sativa after contamination with fuel oil no. 6.

PubMed

Cortés-Pérez, Sandra; Rodríguez-Zaragoza, Salvador; Mendoza-López, Ma Remedios

2014-02-01

Root exudation increases microbial activity, selecting bacterial and fungal communities that metabolize organic matter such as hydrocarbons. However, a strong contamination pulse of hydrocarbons around plant roots may reorganize the soil's microbial trophic structure toward amoebae feeding on bacteria. We conducted a microcosm experiment to elucidate the effect of Medicago sativa on the trophic structure of naked amoebae after a strong pulse of pollution (50,000 ppm of fuel oil no. 6, which is a mixture of long chains ranging from C10 to C28). Plants were seeded 24 h after contamination and species of amoebae in the microcosms were identified at 1, 30, and 60 days after pollution. Several species from three trophic groups of naked amoeba were still alive 24 h after the hydrocarbon pulse. Non-planted microcosms harbored three trophic groups after 60 days, while planted ones nourished four groups. The bacterivore group was the most diverse in all microcosms, followed by protist-eaters and omnivores. The quantity of amoebae was significantly higher (3.4×10(3) organisms/g soil) in the planted pots than in the non-planted ones (1.3×10(3) organisms/g soil after 30 days of pollution (P ≤ 0.01). The shortest hydrocarbon chains (C10-C14) disappeared or diminished in all microcosms, and the longest ones increased in the planted ones. M. sativa thus exerted a positive effect on species richness, quantity, and the composition of amoebae trophic groups in contaminated soil. This indirect effect on bacterial predators is another key factor underlying hydrocarbon assimilation by living organisms during phytoremediation.

Trophic specialization and morphological divergence between two sympatric species in Lake Catemaco, Mexico.

PubMed

Ornelas-García, Claudia Patricia; Córdova-Tapia, Fernando; Zambrano, Luis; Bermúdez-González, María Pamela; Mercado-Silva, Norman; Mendoza-Garfias, Berenit; Bautista, Amando

2018-05-01

The association of morphological divergence with ecological segregation among closely related species could be considered as a signal of divergent selection in ecological speciation processes. Environmental signals such as diet can trigger phenotypic evolution, making polymorphic species valuable systems for studying the evolution of trophic-related traits. The main goal of this study was to analyze the association between morphological differences in trophic-related traits and ecological divergence in two sympatric species, Astyanax aeneus and A. caballeroi, inhabiting Lake Catemaco, Mexico. The trophic differences of a total of 70 individuals (35 A. aeneus and 35 A. caballeroi ) were examined using stable isotopes and gut content analysis; a subset of the sample was used to characterize six trophic and six ecomorphological variables. In our results, we recovered significant differences between both species in the values of stable isotopes, with higher values of δ 15 N for A. caballeroi than for A. aeneus . Gut content results were consistent with the stable isotope data, with a higher proportion of invertebrates in A. caballeroi (a consumption of invertebrates ten times higher than that of A. aeneus , which in turn consumed three times more vegetal material than A. caballeroi ). Finally, we found significant relationship between ecomorphology and stable isotopes ( r  = .24, p  < .01), hence, head length, preorbital length, eye diameter, and δ 15 N were all positively correlated; these characteristics correspond to A. caballeroi . While longer gut and gill rakers, deeper bodies, and vegetal material consumption were positively correlated and corresponded to A. aeneus . Our results are consistent with the hypothesis that morphological divergence in trophic-related traits could be associated with niche partitioning, allowing the coexistence of closely related species and reducing interspecific competition.

Soil microcosm for testing the effects of chemical pollutants on soil fauna communities and trophic structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parmelee, R.W.; Wentsel, R.S.; Phillips, C.T.

1993-08-01

A microcosm technique is presented that uses community and trophic-level analysis of soil nematodes and microarthropods to determine the effects of chemicals on soil systems. Forest soil was treated with either copper, p-nitrophenol, or trinitrotoluene. Nematodes were sorted into bacterivore, fungivore, herbivore, and omnivore-predator trophic groups, and a hatchling category. Microarthropods were sorted to the acarine suborders Prostigmata, Mesostigmata, and Oribatida; the insectan order Collembola; and a miscellaneous group. Omnivore-predator nematodes and meso-stigmatid and oribatid mites were the groups most sensitive to copper and were significantly reduced at levels as low as 100 [mu]g g[sup [minus]1] copper. Total nematode andmore » microarthropod numbers declined above 200 [mu]g g[sup [minus]1] copper. Trophic structure analysis suggested that high sensitivity of nematode predators to intermediate levels of copper reduced predation on herbivore nematodes and resulted in greater numbers of nematodes compared to controls. p-Nitrophenol was very toxic to the nematode community, and all trophic groups were significantly reduced above 20 [mu]g g[sup [minus]1]. However, there was no effect of p-nitrophenol on microarthropods. Trinitrotoluene had no significant negative effect on total abundance of either groups of soil fauna, but oribatids were significantly reduced at 200 [mu]g g[sup [minus]1]. The results demonstrated that soil nematodes and microarthropods were sensitive indicators of environmental contaminants and that trophic-structure and community analysis has the potential to detect more subtle indirect effects of chemicals on soil food-web structure. The authors conclude that microcosms with field communities of soil microfauna offer high resolution of the ecotoxicological effects of chemicals in complex soil systems.« less

Pacific sleeper shark Somniosus pacificus trophic ecology in the eastern North Pacific Ocean inferred from nitrogen and carbon stable-isotope ratios and diet.

PubMed

Courtney, D L; Foy, R

2012-04-01

Stable-isotope ratios of nitrogen (δ¹⁵N) and lipid-normalized carbon (δ¹³C') were used to examine geographic and ontogenetic variability in the trophic ecology of a high latitude benthopelagic elasmobranch, the Pacific sleeper shark Somniosus pacificus. Mean muscle tissue δ¹³C' values of S. pacificus differed significantly among geographic regions of the eastern North Pacific Ocean. Linear models identified significant ontogenetic and geographic variability in muscle tissue δ¹⁵N values of S. pacificus. The trophic position of S. pacificus in the eastern North Pacific Ocean estimated here from previously published stomach-content data (4·3) was within the range of S. pacificus trophic position predicted from a linear model of S. pacificus muscle tissue δ¹⁵N (3·3-5·7) for fish of the same mean total length (L(T) ; 201·5 cm), but uncertainty in predicted trophic position was very high (95% prediction intervals ranged from 2·9 to 6·4). The relative trophic position of S. pacificus determined here from a literature review of δ¹⁵N by taxa in the eastern North Pacific Ocean was also lower than would be expected based on stomach-content data alone when compared to fishes, squid and filter feeding whales. Stable-isotope analysis revealed wider variability in the feeding ecology of S. pacificus in the eastern North Pacific Ocean than shown by diet data alone, and expanded previous conclusions drawn from analyses of stomach-content data to regional and temporal scales meaningful for fisheries management. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.

From the epipelagic zone to the abyss: Trophic structure at two seamounts in the subtropical and tropical Eastern Atlantic - Part I zooplankton and micronekton

NASA Astrophysics Data System (ADS)

Denda, Anneke; Stefanowitsch, Benjamin; Christiansen, Bernd

2017-12-01

Specific mechanisms, driving trophic interactions within the pelagic community may be highly variable in different seamount systems. This study investigated the trophic structure of zooplankton and micronekton above and around Ampère and Senghor, two shallow seamounts in the subtropical and tropical Eastern Atlantic, and over the adjacent abyssal plains. For the identification of food sources and trophic positions stable isotope ratios (δ13C and δ15N) were used. δ13C ranged from -24.7‰ to -15.0‰ and δ15N covered a total range of 0.9-15.9‰. Based on epipelagic particulate organic matter, zooplankton and micronekton usually occupied the 1st-3rd trophic level, including herbivorous, omnivorous and carnivorous taxa. δ13C and δ15N values were generally lower in zooplankton and micronekton of the subtropical waters as compared to the tropical region, due to the differing nutrient availability and phytoplankton communities. Correlations between δ13C and δ15N values of particulate organic matter, zooplankton, micronekton and benthopelagic fishes suggest a linear food chain based on a single energy source from primary production for Ampère Seamount, but no evidence was found for an autochthonus seamount production as compared to the open ocean reference site. Between Senghor Seamount and the open ocean δ13C signatures indicate that hydrodynamic effects at seamounts may modify the energy supply at times, but evidence for a seamount effect on the trophic structure of the pelagic communities was weak, which supports the assumption that seamount communities rely to a large extent on advected food sources.

Is benthic food web structure related to diversity of marine macrobenthic communities?

NASA Astrophysics Data System (ADS)

Sokołowski, A.; Wołowicz, M.; Asmus, H.; Asmus, R.; Carlier, A.; Gasiunaité, Z.; Grémare, A.; Hummel, H.; Lesutiené, J.; Razinkovas, A.; Renaud, P. E.; Richard, P.; Kędra, M.

2012-08-01

Numerical structure and the organisation of food webs within macrozoobenthic communities has been assessed in the European waters (Svalbard, Barents Sea, Baltic Sea, North Sea, Atlantic Ocean and the Mediterranean Sea) to address the interactions between biodiversity and ecosystem functioning. Abundance and classical species diversity indices (S, H', J) of macrofaunal communities were related to principal attributes of food webs (relative trophic level and food chain length, FCL) that were determined from carbon and nitrogen stable isotope values. Structure of marine macrobenthos varies substantially at a geographical scale; total abundance ranges from 63 ind. m-2 to 34,517 ind. m-2, species richness varies from 3 to 166 and the Shannon-Weaver diversity index from 0.26 to 3.26 while Pielou's evenness index is below 0.73. The major source of energy for macrobenthic communities is suspended particulate organic matter, consisting of phytoplankton and detrital particles, sediment particulate organic matter, and microphytobenthos in varying proportions. These food sources support the presence of suspension- and deposit-feeding communities, which dominate numerically on the sea floor. Benthic food webs include usually four to five trophic levels (FCL varies from 3.08 to 4.86). Most species are assigned to the second trophic level (primary consumers), fewer species are grouped in the third trophic level (secondary consumers), and benthic top predators are the least numerous. Most species cluster primarily at the lowest trophic level that is consistent with the typical organization of pyramidal food webs. Food chain length increases with biodiversity, highlighting a positive effect of more complex community structure on food web organisation. In more diverse benthic communities, energy is transferred through more trophic levels while species-poor communities sustain a shorter food chain.

Phylogenetic patterns of climatic, habitat and trophic niches in a European avian assemblage

PubMed Central

Pearman, Peter B; Lavergne, Sébastien; Roquet, Cristina; Wüest, Rafael; Zimmermann, Niklaus E; Thuiller, Wilfried

2014-01-01

Aim The origins of ecological diversity in continental species assemblages have long intrigued biogeographers. We apply phylogenetic comparative analyses to disentangle the evolutionary patterns of ecological niches in an assemblage of European birds. We compare phylogenetic patterns in trophic, habitat and climatic niche components. Location Europe. Methods From polygon range maps and handbook data we inferred the realized climatic, habitat and trophic niches of 405 species of breeding birds in Europe. We fitted Pagel's lambda and kappa statistics, and conducted analyses of disparity through time to compare temporal patterns of ecological diversification on all niche axes together. All observed patterns were compared with expectations based on neutral (Brownian) models of niche divergence. Results In this assemblage, patterns of phylogenetic signal (lambda) suggest that related species resemble each other less in regard to their climatic and habitat niches than they do in their trophic niche. Kappa estimates show that ecological divergence does not gradually increase with divergence time, and that this punctualism is stronger in climatic niches than in habitat and trophic niches. Observed niche disparity markedly exceeds levels expected from a Brownian model of ecological diversification, thus providing no evidence for past phylogenetic niche conservatism in these multivariate niches. Levels of multivariate disparity are greatest for the climatic niche, followed by disparity of the habitat and the trophic niches. Main conclusions Phylogenetic patterns in the three niche components differ within this avian assemblage. Variation in evolutionary rates (degree of gradualism, constancy through the tree) and/or non-random macroecological sampling probably lead here to differences in the phylogenetic structure of niche components. Testing hypotheses on the origin of these patterns requires more complete phylogenetic trees of the birds, and extended ecological data on different niche components for all bird species. PMID:24790525

A Trophic Model of a Sandy Barrier Lagoon at Chiku in Southwestern Taiwan

NASA Astrophysics Data System (ADS)

Lin, H.-J.; Shao, K.-T.; Kuo, S.-R.; Hsieh, H.-L.; Wong, S.-L.; Chen, I.-M.; Lo, W.-T.; Hung, J.-J.

1999-05-01

Using the ECOPATH 3.0 software system, a balanced trophic model of a sandy barrier lagoon with intensive fishery activities at Chiku in tropical Taiwan was constructed. The lagoon model comprised 13 compartments. Trophic levels of the compartments varied from 1·0 for primary producers and detritus to 3·6 for piscivorous fish. Hanging-cultured oysters accounted for 39% of the harvestable fishery biomass and were the most important fishery species. The most prominent group in terms of biomass and energy flow in the lagoon was herbivorous zooplankton. Manipulations of the biomass of herbivorous zooplankton would have a marked impact on most compartments. Both total system throughput and fishery yield per unit area were high when compared to other reported marine ecosystems. This appears mainly due to high planktonic primary production, which is probably promoted by enriched river discharges draining mangroves and aquaculture ponds. Consequently, more than half of the total system throughput originates from primary producers in the lagoon. Although half of the primary production was not immediately used by upper trophic levels and flowed into the detrital pool, most of the detritus was directly consumed, passed up the food web and was exported to the fishery. Thus only a small proportion of energy was recycled through detritus pathways. This mechanism produces short pathways with high trophic efficiencies at higher trophic levels. The high fishery yield in the lagoon is due to high primary production and short pathways. This is the first model of a tropical sandy barrier lagoon with intensive fishery activities and thus may serve as a basis for future comparisons and ecosystem management.

Zooplankton trophic niches respond to different water types of the western Tasman Sea: A stable isotope analysis

NASA Astrophysics Data System (ADS)

Henschke, Natasha; Everett, Jason D.; Suthers, Iain M.; Smith, James A.; Hunt, Brian P. V.; Doblin, Martina A.; Taylor, Matthew D.

2015-10-01

The trophic relationships of 21 species from an oceanic zooplankton community were studied using stable isotopes of carbon and nitrogen. Zooplankton and suspended particulate organic matter (POM) were sampled in three different water types in the western Tasman Sea: inner shelf (IS), a cold core eddy (CCE) and a warm core eddy (WCE). δ15N values ranged from 3.9‰ for the parasitic copepod Sapphirina augusta to 10.2‰ for the euphausiid, Euphausia spinifera. δ13C varied from -22.6 to -19.4‰ as a result of the copepod Euchirella curticauda and E. spinifera. The isotopic composition of POM varied significantly among water types; as did the trophic enrichment of zooplankton over POM, with the lowest enrichment in the recently upwelled IS water type (0.5‰) compared to the warm core eddy (1.6‰) and cold core eddy (2.7‰). The WCE was an oligotrophic environment and was associated with an increased trophic level for omnivorous zooplankton (copepods and euphausiids) to a similar level as carnivorous zooplankton (chaetognaths). Therefore carnivory in zooplankton can increase in response to lower abundance and reduced diversity in their phytoplankton and protozoan prey. Trophic niche width comparisons across three zooplankton species: the salp Thalia democratica, the copepod Eucalanus elongatus and the euphausiid Thysanoessa gregaria, indicated that both niche partitioning and competition can occur within the zooplankton community. We have shown that trophic relationships among the zooplankton are dynamic and respond to different water types. The changes to the zooplankton isotopic niche, however, were still highly variable as result of oceanographic variation within water types.

A revisitation of TRIX for trophic status assessment in the light of the European Water Framework Directive: application to Italian coastal waters.

PubMed

Pettine, Maurizio; Casentini, Barbara; Fazi, Stefano; Giovanardi, Franco; Pagnotta, Romano

2007-09-01

The trophic status classification of coastal waters at the European scale requires the availability of harmonised indicators and procedures. The composite trophic status index (TRIX) provides useful metrics for the assessment of the trophic status of coastal waters. It was originally developed for Italian coastal waters and then applied in many European seas (Adriatic, Tyrrhenian, Baltic, Black and Northern seas). The TRIX index does not fulfil the classification procedure suggested by the WFD for two reasons: (a) it is based on an absolute trophic scale without any normalization to type-specific reference conditions; (b) it makes an ex ante aggregation of biological (Chl-a) and physico-chemical (oxygen, nutrients) quality elements, instead of an ex post integration of separate evaluations of biological and subsequent chemical quality elements. A revisitation of the TRIX index in the light of the European Water Framework Directive (WFD, 2000/60/EC) and new TRIX derived tools are presented in this paper. A number of Italian coastal sites were grouped into different types based on a thorough analysis of their hydro-morphological conditions, and type-specific reference sites were selected. Unscaled TRIX values (UNTRIX) for reference and impacted sites have been calculated and two alternative UNTRIX-based classification procedures are discussed. The proposed procedures, to be validated on a broader scale, provide users with simple tools that give an integrated view of nutrient enrichment and its effects on algal biomass (Chl-a) and on oxygen levels. This trophic evaluation along with phytoplankton indicator species and algal blooms contribute to the comprehensive assessment of phytoplankton, one of the biological quality elements in coastal waters.

Efficiency of transfer of essential polyunsaturated fatty acids versus organic carbon from producers to consumers in a eutrophic reservoir.

PubMed

Gladyshev, Michail I; Sushchik, Nadezhda N; Anishchenko, Olesia V; Makhutova, Olesia N; Kolmakov, Vladimir I; Kalachova, Galina S; Kolmakova, Anzhelika A; Dubovskaya, Olga P

2011-02-01

One of the central paradigms of ecology is that only about 10% of organic carbon production of one trophic level is incorporated into new biomass of organisms of the next trophic level. Many of energy-yielding compounds of carbon are designated as 'essential', because they cannot be synthesized de novo by consumers and must be obtained with food, while they play important structural and regulatory functions. The question arises: are the essential compounds transferred through trophic chains with the same efficiency as bulk carbon? To answer this question, we measured gross primary production of phytoplankton and secondary production of zooplankton and content of organic carbon and essential polyunsaturated fatty acids of ω-3 family with 18-22 carbon atoms (PUFA) in the biomass of phytoplankton and zooplankton in a small eutrophic reservoir during two summers. Transfer efficiency between the two trophic levels, phytoplankton (producers) and zooplankton (consumers), was calculated as ratio of the primary production versus the secondary (zooplankton) production for both carbon and PUFA. We found that the essential PUFA were transferred from the producers to the primary consumers with about twice higher efficiency than bulk carbon. In contrast, polyunsaturated fatty acids with 16 carbon atoms, which are synthesized exclusively by phytoplankton, but are not essential for animals, had significantly lower transfer efficiency than both bulk carbon, and essential PUFA. Thus, the trophic pyramid concept, which implicitly implies that all the energy-yielding compounds of carbon are transferred from one trophic level to the next with the same efficiency of about on average 10%, should be specified for different carbon compounds.

How does predation affect the bioaccumulation of hydrophobic organic compounds in aquatic organisms?

PubMed

Xia, Xinghui; Li, Husheng; Yang, Zhifeng; Zhang, Xiaotian; Wang, Haotian

2015-04-21

It is well-known that the body burden of hydrophobic organic compounds (HOCs) increases with the trophic level of aquatic organisms. However, the mechanism of HOC biomagnification is not fully understood. To fill this gap, this study investigated the effect of predation on the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs), one type of HOC, in low-to-high aquatic trophic levels under constant freely dissolved PAH concentrations (1, 5, or 10 μg L(-1)) maintained by passive dosing systems. The tested PAHs included phenanthrene, anthracene, fluoranthene, and pyrene. The test organisms included zebrafish, which prey on Daphnia magna, and cichlids, which prey on zebrafish. The results revealed that for both zebrafish and cichlids, predation elevated the uptake and elimination rates of PAHs. The increase of uptake rate constant ranged from 20.8% to 39.4% in zebrafish with the amount of predation of 5 daphnids per fish per day, and the PAH uptake rate constant increased with the amount of predation. However, predation did not change the final bioaccumulation equilibrium; the equilibrium concentrations of PAHs in fish only depended on the freely dissolved concentration in water. Furthermore, the lipid-normalized water-based bioaccumulation factor of each PAH was constant for fish at different trophic levels. These findings infer that the final bioaccumulation equilibrium of PAHs is related to a partition between water and lipids in aquatic organisms, and predation between trophic levels does not change bioaccumulation equilibrium but bioaccumulation kinetics at stable freely dissolved PAH concentrations. This study suggests that if HOCs have not reached bioaccumulation equilibrium, biomagnification occurs due to enhanced uptake rates caused by predation in addition to higher lipid contents in higher trophic organisms. Otherwise, it is only due to the higher lipid contents in higher trophic organisms.

Assessing Trophic Position and Mercury Accumulation in Sanpping Turtles

EPA Science Inventory

This study determined the trophic position and the total mercury concentrations of snapping turtles (Chelydra serpentina) captured from 26 freshwater sites in Rhode Island. Turtles were captured in baited wire cages, and a non-lethal sampling technique was used in which tips of ...

Effects of exurban development on trophic interactions in a desert landscape

USDA-ARS?s Scientific Manuscript database

Context Mechanisms of ecosystem change in urbanizing landscapes are poorly understood, especially in exurban areas featuring residential or commercial development set in a matrix of modified and natural vegetation. We asked how development altered trophic interactions and ecosystem processes in the ...

Howling about Trophic Cascades

ERIC Educational Resources Information Center

Kowalewski, David

2012-01-01

Following evolutionary theory and an agriculture model, ecosystem research has stressed bottom-up dynamics, implying that top wild predators are epiphenomenal effects of more basic causes. As such, they are assumed expendable. A more modern co-evolutionary and wilderness approach--trophic cascades--instead suggests that top predators, whose…

Trophic Magnification of PCBs and Its Relationship to the Octanol−Water Partition Coefficient

EPA Science Inventory

We investigated polychlorinated biphenyl (PCB) bioaccumulation relative to octanol-water partition coefficient (K_OW) and organism trophic position (TP) at the Lake Hartwell Superfund (South Carolina, USA). We measured PCBs (127 congeners) and stable isotopes (δ^15...

Trophic transference of microplastics under a low exposure scenario: Insights on the likelihood of particle cascading along marine food-webs.

PubMed

Santana, M F M; Moreira, F T; Turra, A

2017-08-15

Microplastics are emergent pollutants in marine environments, whose risks along food-web still need to be understood. Within this knowledge gap, MPs transference and persistence along trophic levels are key processes. We assessed the potential occurrence of these processes considering a less extreme scenario of exposure than used previously, with microplastics present only in the hemolymph of prey (the mussel Perna perna) and absent in the gut cavity. Predators were the crab Callinectes ornatus and the puffer fish Spheoeroides greeleyi. Transference of microplastics occurred from prey to predators but without evidences of particle persistence in their tissues after 10days of exposure. This suggests a reduced likelihood of trophic cascading of particles and, consequently, a reduced risk of direct impacts of microplastics on higher trophic levels. However, the contact with microplastics along food-webs is still concerning, modulated by the concentration of particles in prey and predators' depuration capacity and rate. Copyright © 2017. Published by Elsevier Ltd.

Predictive power of food web models based on body size decreases with trophic complexity.

PubMed

Jonsson, Tomas; Kaartinen, Riikka; Jonsson, Mattias; Bommarco, Riccardo

2018-05-01

Food web models parameterised using body size show promise to predict trophic interaction strengths (IS) and abundance dynamics. However, this remains to be rigorously tested in food webs beyond simple trophic modules, where indirect and intraguild interactions could be important and driven by traits other than body size. We systematically varied predator body size, guild composition and richness in microcosm insect webs and compared experimental outcomes with predictions of IS from models with allometrically scaled parameters. Body size was a strong predictor of IS in simple modules (r 2  = 0.92), but with increasing complexity the predictive power decreased, with model IS being consistently overestimated. We quantify the strength of observed trophic interaction modifications, partition this into density-mediated vs. behaviour-mediated indirect effects and show that model shortcomings in predicting IS is related to the size of behaviour-mediated effects. Our findings encourage development of dynamical food web models explicitly including and exploring indirect mechanisms. © 2018 John Wiley & Sons Ltd/CNRS.

Phenological sensitivity to climate across taxa and trophic levels.

PubMed

Thackeray, Stephen J; Henrys, Peter A; Hemming, Deborah; Bell, James R; Botham, Marc S; Burthe, Sarah; Helaouet, Pierre; Johns, David G; Jones, Ian D; Leech, David I; Mackay, Eleanor B; Massimino, Dario; Atkinson, Sian; Bacon, Philip J; Brereton, Tom M; Carvalho, Laurence; Clutton-Brock, Tim H; Duck, Callan; Edwards, Martin; Elliott, J Malcolm; Hall, Stephen J G; Harrington, Richard; Pearce-Higgins, James W; Høye, Toke T; Kruuk, Loeske E B; Pemberton, Josephine M; Sparks, Tim H; Thompson, Paul M; White, Ian; Winfield, Ian J; Wanless, Sarah

2016-07-14

Differences in phenological responses to climate change among species can desynchronise ecological interactions and thereby threaten ecosystem function. To assess these threats, we must quantify the relative impact of climate change on species at different trophic levels. Here, we apply a Climate Sensitivity Profile approach to 10,003 terrestrial and aquatic phenological data sets, spatially matched to temperature and precipitation data, to quantify variation in climate sensitivity. The direction, magnitude and timing of climate sensitivity varied markedly among organisms within taxonomic and trophic groups. Despite this variability, we detected systematic variation in the direction and magnitude of phenological climate sensitivity. Secondary consumers showed consistently lower climate sensitivity than other groups. We used mid-century climate change projections to estimate that the timing of phenological events could change more for primary consumers than for species in other trophic levels (6.2 versus 2.5-2.9 days earlier on average), with substantial taxonomic variation (1.1-14.8 days earlier on average).

Feeding habits and trophic level of the Panama grunt Pomadasys panamensis, an important bycatch species from the shrimp trawl fishery in the Gulf of California.

PubMed

Rodríguez-Preciado, José A; Amezcua, Felipe; Bellgraph, Brian; Madrid-Vera, Juan

2014-01-01

The Panama grunt is an abundant and commercially important species in the southeastern Gulf of California, but the research undertaken on this species is scarce despite its ecological and economic importance. We studied the feeding habits of Panama grunt through stomach content analyses as a first step towards understanding the biology of this species in the study area. Our results indicate that the Panama grunt is a benthic predator throughout its life cycle and feeds mainly on infaunal crustaceans. Diet differences among grunt were not found according to size, diet, or season. Shannon diversity index results indicate that Panama grunt has a limited trophic niche breadth with a diet dominated by a limited number of taxa as crustaceans. The estimated trophic level of this species is 3.59. Overall, the Panama grunt is a carnivorous fish occupying the intermediate levels of the trophic pyramid.

Do invasive corals alter coral reef processes? An empirical approach evaluating reef fish trophic interactions.

PubMed

Miranda, Ricardo J; Nunes, José de Anchieta C C; Mariano-Neto, Eduardo; Sippo, James Z; Barros, Francisco

2018-07-01

Understanding how invasive species affect key ecological interactions and ecosystem processes is imperative for the management of invasions. We evaluated the effects of invasive corals (Tubastraea spp.) on fish trophic interactions in an Atlantic coral reef. Remote underwater video cameras were used to examine fish foraging activity (bite rates and food preferences) on invasive cover levels. Using a model selection approach, we found that fish feeding rates declined with increased invasive cover. For Roving Herbivores (RH) and Sessile Invertivores (SI), an abrupt reduction of fish feeding rates corresponded with higher invasive cover, while feeding rates of Territorial Herbivores (TH) and Mobile Invertivores (MI) decreased linearly with cover increase. Additionally, some fish trophic groups, such as RH, SI and Omnivores (OM), had lower densities in reef sections with high invasive cover. These findings demonstrate that invasive corals negatively impact fish-benthic interactions, and could potentially alter existing trophic relationships in reef ecosystems. Copyright © 2018 Elsevier Ltd. All rights reserved.

Tempo of trophic evolution and its impact on mammalian diversification

PubMed Central

Price, Samantha A.; Hopkins, Samantha S. B.; Smith, Kathleen K.; Roth, V. Louise

2012-01-01

Mammals are characterized by the complex adaptations of their dentition, which are an indication that diet has played a critical role in their evolutionary history. Although much attention has focused on diet and the adaptations of specific taxa, the role of diet in large-scale diversification patterns remains unresolved. Contradictory hypotheses have been proposed, making prediction of the expected relationship difficult. We show that net diversification rate (the cumulative effect of speciation and extinction), differs significantly among living mammals, depending upon trophic strategy. Herbivores diversify fastest, carnivores are intermediate, and omnivores are slowest. The tempo of transitions between the trophic strategies is also highly biased: the fastest rates occur into omnivory from herbivory and carnivory and the lowest transition rates are between herbivory and carnivory. Extant herbivore and carnivore diversity arose primarily through diversification within lineages, whereas omnivore diversity evolved by transitions into the strategy. The ability to specialize and subdivide the trophic niche allowed herbivores and carnivores to evolve greater diversity than omnivores. PMID:22509033

Tempo of trophic evolution and its impact on mammalian diversification.

PubMed

Price, Samantha A; Hopkins, Samantha S B; Smith, Kathleen K; Roth, V Louise

2012-05-01

Mammals are characterized by the complex adaptations of their dentition, which are an indication that diet has played a critical role in their evolutionary history. Although much attention has focused on diet and the adaptations of specific taxa, the role of diet in large-scale diversification patterns remains unresolved. Contradictory hypotheses have been proposed, making prediction of the expected relationship difficult. We show that net diversification rate (the cumulative effect of speciation and extinction), differs significantly among living mammals, depending upon trophic strategy. Herbivores diversify fastest, carnivores are intermediate, and omnivores are slowest. The tempo of transitions between the trophic strategies is also highly biased: the fastest rates occur into omnivory from herbivory and carnivory and the lowest transition rates are between herbivory and carnivory. Extant herbivore and carnivore diversity arose primarily through diversification within lineages, whereas omnivore diversity evolved by transitions into the strategy. The ability to specialize and subdivide the trophic niche allowed herbivores and carnivores to evolve greater diversity than omnivores.

Determination of Trophic Structure in Selected Freshwater Ecosystems by using Stable Isotope Analysis

PubMed Central

Zainordin, ‘Amila Faqhira; Ab Hamid, Suhaila

2017-01-01

Stable isotope analysis has been used extensively to establish trophic relationships in many ecosystems. Present study utilised stable isotope signatures of carbon and nitrogen to identify trophic structure of aquatic food web in river and rice field ecosystems in Perak, northern peninsular Malaysia. The mean δ13C values of all producers ranged from −35.29 ± 0.21 to −26.00 ± 0.050‰. The greatest δ15N values noted was in zenarchopterid fish with 9.68 ± 0.020‰. The δ15N values of aquatic insects ranged between 2.59 ± 0.107 in Elmidae (Coleoptera) and 8.11 ± 0.022‰ in Nepidae (Hemiptera). Correspondingly, with all the δ13C and δ15N values recorded, it can be deduced that there are four trophic levels existed in the freshwater ecosystems which started with the producer (plants), followed by primary consumer (aquatic insects and non-predatory fish), secondary consumer (invertebrate predators) and lastly tertiary consumer (vertebrate predators). PMID:28890758

Feeding habits and trophic level of the Panama grunt Pomadasys panamensis, an important bycatch species from the shrimp trawl fishery in the Gulf of California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez-Preciado, Jose A.; Amezcua-Martinez, Felipe; Bellgraph, Brian J.

The Panama grunt is an abundant and commercially important species in the SE Gulf of California, but the research undertaken on this species is scarce despite its ecological and economic importance. We studied the feeding habits of Panama grunt through stomach content analyses as a first step towards understanding the biology of this species in the study area. Our results show that the Panama grunt is a benthic predator throughout its life cycle and feeds mainly on infaunal crustaceans. Diet differences were not found according to size, diet or season. Shannon diversity index results indicate that Panama grunt have amore » limited trophic niche breadth with a diet dominated by a limited number of taxa. The estimated trophic level of this species is 3.59. Overall, the Panama grunt is a carnivorous fish occupying the intermediate levels of the trophic pyramid.« less

Guano-Derived Nutrient Subsidies Drive Food Web Structure in Coastal Ponds.

PubMed

Vizzini, Salvatrice; Signa, Geraldina; Mazzola, Antonio

2016-01-01

A stable isotope study was carried out seasonally in three coastal ponds (Marinello system, Italy) affected by different gull guano input to investigate the effect of nutrient subsidies on food web structure and dynamics. A marked 15N enrichment occurred in the pond receiving the highest guano input, indicating that gull-derived fertilization (guanotrophication) had a strong localised effect and flowed across trophic levels. The main food web response to guanotrophication was an overall erosion of the benthic pathway in favour of the planktonic. Subsidized primary consumers, mostly deposit feeders, switched their diet according to organic matter source availability. Secondary consumers and, in particular, fish from the guanotrophic pond, acted as couplers of planktonic and benthic pathways and showed an omnivorous trophic behaviour. Food web structure showed substantial variability among ponds and a marked seasonality in the subsidized one: an overall simplification was evident only in summer when guano input maximises its trophic effects, while higher trophic diversity and complexity resulted when guano input was low to moderate.