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1

Antarctic Food Web Game  

NSDL National Science Digital Library

In this interactive game adapted from the Bigelow Laboratory for Ocean Sciences, build a food web that illustrates the flow of energy in an Antarctic ecosystem and the relationships between predators and prey.

2007-08-09

2

Effects of sea-ice extent and krill or salp dominance on the Antarctic food web  

Microsoft Academic Search

Krill (Euphausia superba) provide a direct link between primary producers and higher trophic levels in the Antarctic marine food web. The pelagic tunicate Salpa thompsoni can also be important during spring and summer through the formation of extensive and dense blooms. Although salps are not a major dietary item for Antarctic vertebrate predators,, their blooms can affect adult krill reproduction

V. Loeb; V. Siegel; O. Holm-Hansen; R. Hewitt; W. Fraser; W. Trivelpiece; S. Trivelpiece

1997-01-01

3

The Antarctic Food Chain  

NSDL National Science Digital Library

This lesson plan introduces students to the animals of Antarctica and to the Antarctic food chain. Students will draw pictures of a variety of animals and attach the pictures to a wall collage. They will then listen to or read statements about the diet of each animal and draw arrows to show which animals eat which other animals. Students will end up with a food web that illustrates the importance of krill to the Antarctic ecosystem.

4

Effects of sea-ice extent and krill or salp dominance on the Antarctic food web  

NASA Astrophysics Data System (ADS)

Krill (Euphausia superba) provide a direct link between primary producers and higher trophic levels in the Antarctic marine food web. The pelagic tunicate Salpa thompsoni can also be important during spring and summer through the formation of extensive and dense blooms. Although salps are not a major dietary item for Antarctic vertebrate predators,, their blooms can affect adult krill reproduction and survival of krill larvae. Here we provide data from 1995 and 1996 that support hypothesized relationships between krill, salps and region-wide sea-ice conditions,. We have assessed salp consumption as a proportion of net primary production, and found correlations between herbivore densities and integrated chlorophyll-a that indicate that there is a degree of competition between krill and salps. Our analysis of the relationship between annual sea-ice cover and a longer time series of air temperature measurements, indicates a decreased frequency of winters with extensive sea-ice development over the last five decades. Our data suggest that decreased krill availability may affect the levels of their vertebrate predators. Regional warming and reduced krill abundance therefore affect the marine food web and krill resource management.

Loeb, V.; Siegel, V.; Holm-Hansen, O.; Hewitt, R.; Fraser, W.; Trivelpiece, W.; Trivelpiece, S.

1997-06-01

5

Polar Record. Page 1 of 16. c Cambridge University Press 2013. doi:10.1017/S0032247412000757 1 Fishing down the food web of the Antarctic continental shelf  

E-print Network

Fishing down the food web of the Antarctic continental shelf and slope David G. Ainley H.T. Harvey. The history of biotic exploitation for the continental margin (shelf and slope) of the Antarctic Large Marine Ecosystem (LME) is reviewed, with emphasis on the period from 1970 to 2010. In the Antarctic Peninsula

Pauly, Daniel

6

Productivity and linkages of the food web of the southern region of the western Antarctic Peninsula continental shelf  

NASA Astrophysics Data System (ADS)

The productivity and linkages in the food web of the southern region of the west Antarctic Peninsula continental shelf were investigated using a multi-trophic level mass balance model. Data collected during the Southern Ocean Global Ocean Ecosystem Dynamics field program were combined with data from the literature on the abundance and diet composition of zooplankton, fish, seabirds and marine mammals to calculate energy flows in the food web and to infer the overall food web structure at the annual level. Sensitivity analyses investigated the effects of variability in growth and biomass of Antarctic krill (Euphausia superba) and in the biomass of Antarctic krill predators on the structure and energy fluxes in the food web. Scenario simulations provided insights into the potential responses of the food web to a reduced contribution of large phytoplankton (diatom) production to total primary production, and to reduced consumption of primary production by Antarctic krill and mesozooplankton coincident with increased consumption by microzooplankton and salps. Model-derived estimates of primary production were 187-207 g C m-2 y-1, which are consistent with observed values (47-351 g C m-2 y-1). Simulations showed that Antarctic krill provide the majority of energy needed to sustain seabird and marine mammal production, thereby exerting a bottom-up control on higher trophic level predators. Energy transfer to top predators via mesozooplanton was a less efficient pathway, and salps were a production loss pathway because little of the primary production they consumed was passed to higher trophic levels. Increased predominance of small phytoplankton (nanoflagellates and cryptophytes) reduced the production of Antarctic krill and of its predators, including seabirds and seals.

Ballerini, Tosca; Hofmann, Eileen E.; Ainley, David G.; Daly, Kendra; Marrari, Marina; Ribic, Christine A.; Smith, Walker O.; Steele, John H.

2014-03-01

7

Winter and spring controls on the summer food web of the coastal West Antarctic Peninsula.  

PubMed

Understanding the mechanisms by which climate variability affects multiple trophic levels in food webs is essential for determining ecosystem responses to climate change. Here we use over two decades of data collected by the Palmer Long Term Ecological Research program (PAL-LTER) to determine how large-scale climate and local physical forcing affect phytoplankton, zooplankton and an apex predator along the West Antarctic Peninsula (WAP). We show that positive anomalies in chlorophyll-a (chl-a) at Palmer Station, occurring every 4-6 years, are constrained by physical processes in the preceding winter/spring and a negative phase of the Southern Annular Mode (SAM). Favorable conditions for phytoplankton included increased winter ice extent and duration, reduced spring/summer winds, and increased water column stability via enhanced salinity-driven density gradients. Years of positive chl-a anomalies are associated with the initiation of a robust krill cohort the following summer, which is evident in Adélie penguin diets, thus demonstrating tight trophic coupling. Projected climate change in this region may have a significant, negative impact on phytoplankton biomass, krill recruitment and upper trophic level predators in this coastal Antarctic ecosystem. PMID:25000452

Saba, Grace K; Fraser, William R; Saba, Vincent S; Iannuzzi, Richard A; Coleman, Kaycee E; Doney, Scott C; Ducklow, Hugh W; Martinson, Douglas G; Miles, Travis N; Patterson-Fraser, Donna L; Stammerjohn, Sharon E; Steinberg, Deborah K; Schofield, Oscar M

2014-01-01

8

The Food Web Matching Game  

NSDL National Science Digital Library

In this activity, students construct a food web of Antarctic organisms. Working from a trophic table that provides information about each organisms's role in the food web, they will attempt to place them in their correct positions on a blank food web chart. Links to a glossary are embedded in the text.

9

Food Chain & Food Web  

NSDL National Science Digital Library

What are the differences and similarities between food chain and food web? Print (2) Garden Gate Print (1) Venn Diagram Garden Gate Venn Diagram Let's learn about the food chain and food web.Read the notes.Food Chain 4 Also, view more notes on food chain and food web. Go to the 7th title Food Chain which is before the Habitats and food chain title of the webpage.Food Chain Power Point Presentation Record what you learn ...

Ms. B

2011-10-27

10

Food Webs  

NSDL National Science Digital Library

The representation depicts 4 different food webs: Antarctica, the African Grasslands, the Australia Grasslands and a Marine environment. A separate food web for scavengers and decomposers is present in the African Grasslands section. Viewers must first build the web by moving boxes with the organism's picture and name to the appropriate spot on a grid. Clues describing food requirements are given as the boxes are moved. When the boxes are correctly placed a complete food web (with arrows) is displayed.

11

Food Webs  

NSDL National Science Digital Library

In this activity, learners construct possible food webs for six different ecosystems as they learn about the roles of different kinds of living organisms. Learners will also discuss and classify producers vs. consumers and different kinds of consumers (herbivores, carnivores, omnivores, decomposers and scavengers). This lesson guide includes background information, variations and bilingual (English/Spanish) cards.

2012-06-26

12

Shifts in Ross Sea food web structure as indicated by ?15N and ?13C values of fossil Antarctic seals  

NASA Astrophysics Data System (ADS)

As climate change continues to mount, there is a growing need for understanding its effects on biological-physical interactions of marine ecosystems. Assessing the effects of anthropogenic activities on the coastal marine ecosystem involves understanding the underlying mechanisms driving these changes as well as establishing baselines of the natural system. Preliminary findings have indicated shifts in bulk carbon (C) and nitrogen (N) isotopic values of southern elephant seal (Mirounga leonina) samples, collected in the Dry Valleys of Antarctica in the Ross Sea region, over approximately the last 7,000 years. These shifts could result from 1) seals changing their foraging location and/or diet over this time, 2) climate change-induced shifts in the biogeochemistry at the base of the food web, or 3) some combination of both processes. We explored the patterns of long-term change in Ross Sea food web structure by examining the stable isotope values of three top predators in this system, Weddell seals (Leptonychotes weddellii), leopard seals (Hydrurga leptonyx), and crabeater seals (Lobodon carcinophagus). Fossil seal samples were collected in the Dry Valleys during the austral summer of 2012/13 and then analyzed for bulk C and N isotopes via an elemental analyzer/isotope-ratio mass spectrometer (EA/IRMS). Our initial findings indicate that C isotopic values of fossil seal samples from Weddell, leopard, and crabeater seals were more enriched than isotopic values of modern seals of the same species (e.g., ?13C = -22.79 × 0.92 ‰ and -26.71 × 0.50 ‰ for fossil and modern crabeater seals, respectively). Given the relatively consistent diet of crabeater seals, these findings suggest a shift in baseline food web structure occurred over the last 10,000 years, either through changes in foraging location or local shifts in biogeochemistry. For all species, N isotopic values are widely variable (e.g., 7.28 to 16.0 ?15N ‰ for the Weddell seal), which may be a result of greatly changing diets in the last ~10,000 years, or a changing baseline N value for the Ross Sea. Seal bones will be radiocarbon-dated to isolate the key shifts in C and N isotopic values. Once those major shifts are temporally constrained, compound-specific isotopic analysis of the bone samples will be used to tease apart the diet vs. baseline effects on the bulk isotopic signatures of the seals. Our results suggests that during the last ~10,000 years, there was a fundamental shift in Ross Sea food web structure likely related to long term climatic variability.

Leopold, A.; Brault, E.; McMahon, K.

2013-12-01

13

Food Chains and Food Webs  

NSDL National Science Digital Library

This lesson explains how energy travels through an ecosystem. This flow can be diagrammed in food chains and food webs as shown in the lesson's illustrations. Key terms are hyperlinked so students can easily view definitions of new concepts.

2012-06-14

14

Food Chains and Webs  

NSDL National Science Digital Library

Learn more about food chains, food webs, and how the organisms in them affect each other. In class, you have learned what food webs and food chains are. Today, you will explore how the organisms in these systems interact. Step One: Food Chains What happens when you take something out of a food chain? Go to the Chain Reaction website: Chain Reaction--Food Chains This internet site will help you ...

Ms. Thompson

2007-02-21

15

Food Chains and Webs  

NSDL National Science Digital Library

In this activity, learners investigate feeding relationships. Learners complete a food web and then make a mobile to represent a food chain. Use this activity to talk about predator/prey relationships and ecosystems.

2012-06-26

16

Properties of food webs  

SciTech Connect

On the assumption that systems of interacting species, when perturbed from equilibrium, should return to equilibrium quickly, one can predict four properties of food webs: (1) food chains should be short, (2) species feeding on more than one trophic level (omnivores) should be rare, (3) those species that do feed on more than one trophic level should do so by feeding on species in adjacent trophic levels, and (4) host-parasitoid systems are likely to be exceptions to (1)-(3) when interaction coefficients permit greater trophic complexity. By generating random, model food webs (with many features identical to webs described from a variety of marine, freshwater, and terrestrial systems), it is possible to generate expected values for the number of trophic levels and the degree of omnivory within webs. When compared with these random webs, real world webs are shown to have fewer trophic levels, less omnivory, and very few omnivores feeding on nonadjacent trophic levels. Insect webs are shown to have a greater degree of omnivory than other webs. The confirmation of all these predictions from stability analyses suggests that system stability places necessary, though not sufficient, limitations on the possible shapes of food webs.

Pimm, S.L.

1980-04-01

17

Ocean Food Web Game  

NSDL National Science Digital Library

Students learn about the connections between organisms in the ocean in this kinesthetic activity. Each student is given a card, identifying an organism, its food source, and its predators. Holding the end of a ball of yarn firmly, the ball is passed from organism to organism as they are linked in the predator-prey food web. Once all students are connected in the food web, an extinction event is simulated by removing an organism. Those students remaining pull lightly on the web, to demonstrate how other organisms are affected by the loss. Students identify the impact of biodiversity loss throughout the food web. This activity is supported by a textbook chapter, One Global Ocean, part of the unit, Losing Biodiversity, in Global Systems Science (GSS), an interdisciplinary course for high school students that emphasizes how scientists from a wide variety of fields work together to understand significant problems of global impact.

2012-09-28

18

Oceanic Food Web  

NSDL National Science Digital Library

This visualization illustrates the carbon cycle throughout the oceanic zones, beginning at the surface and traveling to the deep. The concept map-like connections encourage students to link the abiotic and biotic interactions within the oceanic food web.

Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science

19

Planktonic microbial assemblages and the potential effects of metazooplankton predation on the food web of lakes from the maritime Antarctica and subAntarctic islands  

Microsoft Academic Search

Antarctica is the continent with the harshest climate on the Earth. Antarctic lakes, however, usually presents liquid water, at least during part of the year or below the ice cover, especially those from the sub-Antarctic islands and the maritime Antarctic region where climatic conditions are less extreme. Planktonic communities in these lakes are mostly dominated by microorganisms, including bacteria and

Antonio Camacho

2006-01-01

20

Forest food web Illustration  

NSDL National Science Digital Library

The lowest level of a food web includes producers, which are plants that make their own energy from the sun. Animals that eat these producers are called primary consumers, and consumers that eat other consumers are called secondary consumers. Decomposers break down dead plants and animals to release nutrients into the soil.

Katie Hale (CSUF; Biological Sciences)

2007-07-14

21

Forest Food Webs  

NSDL National Science Digital Library

This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 6-8. It focuses on the seasonal changes that affect life in a temperate forest ecosystem and how organisms in a temperate forest are dependent on one another for proper nutrition. Students describe the three major types of organisms that live in an ecosystem, three types of consumers, food webs, and food chains. They then create a food web diagram for display in their classrooms. Included are objectives, materials, procedures, discussion questions, evaluation ideas, suggested readings, and vocabulary. There are videos available to order which complement this lesson, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

Mary Cahill

2007-12-12

22

The Great Lakes Food Web.  

ERIC Educational Resources Information Center

Presents a play for students in grades four to nine that incorporates the scientific names, physical characteristics, feeding habits, interactions, and interdependence of the plants and animals that make up the Great Lakes food web to facilitate the learning of this complex system. Includes a Great Lakes food web chart. (AIM)

Baker, Marjane L.

1997-01-01

23

Complexity in quantitative food webs  

Microsoft Academic Search

Food webs depict who eats whom in communities. Ecologists have examined statistical metrics and other properties of food webs, but mainly due to the uneven quality of the data, the results have proved controversial. The qualitative data on which those efforts rested treat trophic interactions as present or absent and disregard potentially huge variation in their magnitude, an approach similar

C. Banasek-Richter; Louis-Félix Bersier; Marie-France Cattin; Richard Baltensperger; Jean-Pierre Gabriel; Yves Merz; Robert E. Ulanowicz; Annette F. Tavares; D. Dudley Williams; Ruiter de P. C; Kirk O. Winemiller; Russell E. Naisbit

2009-01-01

24

Top-down control on plankton components in an Antarctic pond: experimental approach to the study of low-complexity food webs  

Microsoft Academic Search

In order to address the top-down effect on the different phytoplankton size-fractions and ciliates, a survey at microcosm scale was conducted in a hypertrophic Antarctic pond, testing the hypotheses that (1) the picophytoplankton is regulated by a top-down control exerted by organisms of the bigger size-fractions, and (2) the nanoplankton fraction (algae and ciliates) is not regulated by a top-down

Luz Allende; Haydée Pizarro

2006-01-01

25

Research on the Web: Antarctic Weather Stations  

NSDL National Science Digital Library

This Web research activity helps students see the link between wind speeds and geographical features. All directions are included in a printable handout. Students begin by gathering wind-speed measurements for 10 weather stations in Antarctica, converting the data, as needed, to allow comparisons. Next, they record wind data for five consecutive days and calculate the average wind speed for each station. They then examine elevation data for the 10 weather stations. They end by developing a hypothesis for the different patterns they've observed.

26

Food Web and Energy Flow  

NSDL National Science Digital Library

This chapter discusses the concept of a food web and energy flow. Its activities will assist students in defining and constructing an energy pyramid. These activities can be incorporated into lessons which teach students how to create a food web and and identify the interdependencies within that habitat. Students will learn how to identify and illustrate parts of the water cycle, the carbon-oxygen cycle, and the nitrogen cycle. This section also offers students the tools to demonstrate active knowledge of conservation measures.

Janet R. Galle

2005-01-01

27

Food Chains and Food Webs - Balance within Natural Systems  

NSDL National Science Digital Library

With a continued focus on the Sonoran Desert, students are introduced to the concepts of food chains and food webs through a PowerPoint® presentation. They learn the difference between producers and consumers and study how these organisms function within their communities as participants in various food chains. They further understand ecosystem differences by learning how multiple food chains link together to form intricate and balanced food webs. At lesson end, students construct food webs using endemic desert species.

2014-09-18

28

Simple Rules Yield Complex Food Webs  

Microsoft Academic Search

Several of the most ambitious theories in ecology describe food webs that document the structure of strong and weak trophic links among diverse assemblages of species. Early mechanism-based theory asserted that food webs have little omnivory and several properties that are independent of species richness. This theory was overturned by empirical studies that found food webs to be much more

Neo Martinez

2003-01-01

29

INTRODUCTION Aquatic food-webs' ecology  

E-print Network

INTRODUCTION Aquatic food-webs' ecology: old and new challenges Andrea Belgrano Looking up ``aquatic food web'' on Google provides a dizzying array of eclectic sites and information (and disinformation!) to choose from. However, even within this morass it is clear that aquatic food-web research has

30

Persistence of complex food webs in metacommunities  

E-print Network

Persistence of complex food webs in metacommunities Gesa A. B¨ohme 1 and Thilo Gross 2 1 Max of Engineering Mathematics, Bristol, UK Keywords: metacommunities, food webs, predator-prey interactions, geo diversity and food web complexity. Recently Pillai et al. proposed a simple modeling framework

31

Fitting Algae Into the Food Web  

NSDL National Science Digital Library

This activity will help students understand food chains and food webs in the ocean. After studying the materials provided, students will play a food web game, in which they are given a blank food web and the names of the organisms. Students place the organisms in their correct places on the food web so that the arrows indicate the direction of energy flow. As a follow-up, students decide what would happen if they removed one of the organisms from the food web, consider the role of decomposers, and deal with geographic variation. Students should also be able to understand the importance of and need for primary producers, the interdependence of organisms, the role of bacteria in the food web, and geographic variation in food webs.

2007-12-12

32

Food webs for parasitologists: a review.  

PubMed

This review examines the historical origins of food web theory and explores the reasons why parasites have traditionally been left out of food web studies. Current paradigms may still be an impediment because, despite several attempts, it remains virtually impossible to retrofit parasites into food web theory in any satisfactory manner. It seems clear that parasitologists must return to first principles to solve how best to incorporate parasites into ecological food webs, and a first step in changing paradigms will be to include parasites in the classic ecological patterns that inform food web theory. The limitations of current food web models are discussed with respect to their logistic exclusion of parasites, and the traditional matrix approach in food web studies is critically examined. The well-known energetic perspective on ecosystem organization is presented as a viable alternative to the matrix approach because it provides an intellectually powerful theoretical paradigm for generating testable hypotheses on true food web structure. This review proposes that to make significant contributions to the food web debate, parasitologists must work from the standpoint of natural history to elucidate patterns of biomass, species abundance, and interaction strengths in real food webs, and these will provide the basis for more realistic models that incorporate parasite dynamics into the overall functional dynamics of the whole web. A general conclusion is that only by quantifying the effects of parasites in terms of energy flows (or biomass) will we be able to correctly place parasites into food webs. PMID:19891512

Sukhdeo, Michael V K

2010-04-01

33

Got Energy? Spinning a Food Web  

NSDL National Science Digital Library

Students learn about energy flow in food webs, including the roles of the sun, producers, consumers and decomposers in the energy cycle. They model a food web and create diagrams of food webs using their own drawings and/or images from nature or wildlife magazines. Students investigate the links between the sun, plants and animals, building their understanding of the web of nutrient dependency and energy transfer.

Integrated Teaching and Learning Program,

34

Soil Litter: The Food Web  

NSDL National Science Digital Library

Teachers could incorporate this brief radio program into a variety of learning settings. For example, teachers living in the temperate deciduous forest biome can play the program for students when leaves begin to fall in autumn. The program could also be used whenever students anywhere are learning about food webs or soil. Teachers can choose to use either the audio or text version (or both) to give students listening or reading practice.

Pulse of the Planet

2006-06-27

35

Where are the parasites in food webs?  

PubMed Central

This review explores some of the reasons why food webs seem to contain relatively few parasite species when compared to the full diversity of free living species in the system. At present, there are few coherent food web theories to guide scientific studies on parasites, and this review posits that the methods, directions and questions in the field of food web ecology are not always congruent with parasitological inquiry. For example, topological analysis (the primary tool in food web studies) focuses on only one of six important steps in trematode life cycles, each of which requires a stable community dynamic to evolve. In addition, these transmission strategies may also utilize pathways within the food web that are not considered in traditional food web investigations. It is asserted that more effort must be focused on parasite-centric models, and a central theme is that many different approaches will be required. One promising approach is the old energetic perspective, which considers energy as the critical resource for all organisms, and the currency of all food web interactions. From the parasitological point of view, energy can be used to characterize the roles of parasites at all levels in the food web, from individuals to populations to community. The literature on parasite energetics in food webs is very sparse, but the evidence suggests that parasite species richness is low in food webs because parasites are limited by the quantity of energy available to their unique lifestyles. PMID:23092160

2012-01-01

36

UNSTRUCTURED MARINE FOOD WEBS AND "POLLUTANT ANALOGUES"  

E-print Network

in the simple linear food chain ex- isting in that isolated marine environment and that the cesium/potassium (Cs by using real data. Let us first assume that in a food web each transfer of organic material (or energyUNSTRUCTURED MARINE FOOD WEBS AND "POLLUTANT ANALOGUES" JOHN D. ISAACS' ABSTRACT The several

37

Food web dynamics in the Scotia Sea in summer: A stable isotope study  

Microsoft Academic Search

The pelagic food web of the Scotia Sea was studied by analysing natural abundances of nitrogen and carbon stable isotopes of primary producers and pelagic consumers, sampled from the seasonal ice edge in the south to the Antarctic Polar Front in the north. The analysis covered, within a single mid-summer period, particulate organic matter (POM) and 38 taxa, ranging from

G. Stowasser; A. Atkinson; R. A. R. McGill; R. A. Phillips; M. A. Collins; D. W. Pond

38

Live from Antarctica 2: The Food Web Game  

NSDL National Science Digital Library

This activity will help students understand that increases in the ozone hole will result in damaging ultraviolet-B (UV-B) rays penetrating deep into the ocean, and harming young marine life, such as floating fish eggs, fish larvae, juvenile fish, and shrimp larvae, and affecting phytoplankton movement. Students will discover how others in the Antarctic food web will be affected if phytoplankton are harmed by depletion of the ozone layer. They will also find out what will survive UV-B radiation in Antarctica.

39

The microbial food web along salinity gradients  

Microsoft Academic Search

The microbial food web was studied along a gradient of salinity in two solar salterns used for the commercial production of salt. The different ponds in the salterns provide a wide range of ecosystems with food webs of different complexities. Abundance of prokaryotes, cell volume, prokaryotic heterotrophic production, chlorophyll a, abundance of heterotrophic flagellates, ciliates and phytoplankton were determined in

Carlos Pedrós-Alió; Juan I Calderón-Paz; Marlie H MacLean; Glòria Medina; Cèlia Marrasé; Josep M Gasol; Núria Guixa-Boixereu

2000-01-01

40

Simple rules yield complex food webs  

Microsoft Academic Search

Several of the most ambitious theories in ecology describe food webs that document the structure of strong and weak trophic links that is responsible for ecological dynamics among diverse assemblages of species. Early mechanism-based theory asserted that food webs have little omnivory and several properties that are independent of species richness. This theory was overturned by empirical studies that found

Richard J. Williams; Neo D. Martinez

2000-01-01

41

KELP FOREST FOOD WEBS IN GWAII HAANAS  

E-print Network

Grazing Rates on Kelp Assimilation of Kelp-derived Organic Carbon in Kelp Forest Food Webs | 33 IntertidalKELP FOREST FOOD WEBS IN GWAII HAANAS: Ecosystem-Level Effects of Predator Depletion and Recovery Management Faculty of Environment | Simon Fraser University Principal Investigator: Dr. Anne Salomon, SFU REM

42

Food Webs, Body Size, and Species Abundance in Ecological  

E-print Network

understood, and can reveal new patterns, by labeling each species that appears in a community's food web with Food Webs, Body Size, and Species Abundance in Ecological Community Description TOMAS JONSSON, JOEL Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 D. EVect of Food Web Perturbation

Cohen, Joel E.

43

Antarctic data management at the National Snow and Ice Data Center: Web-based geospatial tools for Antarctic discovery and analysis  

NASA Astrophysics Data System (ADS)

Located at the National Snow and Ice Data Center (NSIDC), the Antarctic Glaciological Data Center (AGDC) and the U.S. Antarctic Data Coordination Center (USADCC), supported by the National Science Foundation's Office of Polar Programs, archive and distribute Antarctic glaciological and cryospheric system data collected by researchers affiliated with the U.S. Antarctic Program. The centers provide long-term access to Antarctic data sets and information so that past and present findings are available for comparison with future data in change detection studies. By facilitating broad data and information access, the centers promote interdisciplinary scientific research. The AGDC and the USADCC offer a geospatial presentation of data sets and information using maps or image data of the Antarctic. They are currently migrating image data such as the surface morphology and snow grain size derived from Moderate Resolution Imaging Spectroradiometer (MODIS) images into the Mosaic of Antarctica (MOA) data product. They are also contributing data set locations from the USADCC's metadata files, image time-series data from the AGDC's Images of Antarctic Ice Shelves, PI-field project point data from the AGDC's Web archive (http://nsidc.org/agdc), and velocity vector locations from Antarctic outlet glaciers to a Web-available search and discovery tool (such as, Google Earth and the Minnesota Map Server).

Bauer, R.; Husted, L.; Scambos, T.; Bohlander, J.; Haran, T.; Judy, C.; Scharfen, G.

2006-12-01

44

Parasites in the Wadden Sea food web  

NASA Astrophysics Data System (ADS)

While the free-living fauna of the Wadden Sea has received much interest, little is known on the distribution and effects of parasites in the Wadden Sea food web. However, recent studies on this special type of trophic interaction indicate a high diversity of parasites in the Wadden Sea and suggest a multitude of effects on the hosts. This also includes effects on specific predator-prey relationships and the general structure of the food web. Focussing on molluscs, a major group in the Wadden Sea in terms of biomass and abundance and an important link between primary producers and predators, we review existing studies and exemplify the ecological role of parasites in the Wadden Sea food web. First, we give a brief inventory of parasites occurring in the Wadden Sea, ranging from microparasites (e.g. protozoa, bacteria) to macroparasites (e.g. helminths, parasitic copepods) and discuss the effects of spatial scale on heterogeneities in infection levels. We then demonstrate how parasites can affect host population dynamics by acting as a strong mortality factor, causing mollusc mass mortalities. In addition, we will exemplify how parasites can mediate the interaction strength of predator-prey relationships and affect the topological structure of the Wadden Sea food web as a whole. Finally, we highlight some ongoing changes regarding parasitism in the Wadden Sea in the course of global change (e.g. species introduction, climate change) and identify important future research questions to entangle the role of parasites in the Wadden Sea food web.

Thieltges, David W.; Engelsma, Marc Y.; Wendling, Carolin C.; Wegner, K. Mathias

2013-09-01

45

Constructing Sonoran Desert Food Chains and Food Webs  

NSDL National Science Digital Library

Is the food chain shown above accurate? Does the first link depict a producer, the second link a herbivore, and the third link an omnivore / carnivore? Students must correctly determine whether a species is a producer or consumer, and what type of consumer; herbivore, omnivore, or carnivore. Students are provided with a list of Sonoran Desert species and asked to construct, within their groups, several food chains. These food chains are then be used to construct a food web. In order to complete this activity, students must first research the individual species to understand their feeding habits.

VU Bioengineering RET Program,

46

Antarctic  

NSDL National Science Digital Library

Become an expert on the Antarctic habitat!! Begin your search for information by reading below. You can click on the underlined words to take you to the website you want to go to. Have fun! Read carefully. To find out about the habitat you can visit The Arctic: Earth s North Polar Region, Polar Region, and Arctic Tundra. Read the websites carefully to find important facts. Antarctica Animals and Animals in Antarctica will tell you about animals that live in the antarctic. Maya! Emperor Penguin will tell you lots of facts about penguins. To find more facts visit Penguin Facts. At this website ...

Ms. Ryan

2013-02-12

47

Food Web of a Pond  

NSDL National Science Digital Library

The representation depicts the food-based interconnections of selected organisms in a pond. Through the interactive interface, users can read about changes to organism populations as one species increases or decreases in number.

48

DEEPWATER AND NEARSHORE FOOD WEB CHARACTERIZATIONS IN LAKE SUPERIOR  

EPA Science Inventory

Due to the difficulty associated with sampling deep aquatic systems, food web relationships among deepwater fauna are often poorly known. We are characterizing nearshore versus offshore habitats in the Great Lakes and investigating food web linkages among profundal, pelagic, and ...

49

Structural Degradation in Mediterranean Sea Food Webs  

E-print Network

Structural Degradation in Mediterranean Sea Food Webs: Testing Ecological Hypotheses Using-Central Adriatic and South Catalan Sea) and two time periods (mid-late 1970s and 1990s) in the Mediterranean Sea to species removal; Niche model; Ecopath model; Mediterranean Sea. INTRODUCTION Degradation of marine

Myers, Ransom A.

50

Effects of fish in river food webs.  

PubMed

Experimental manipulations of fish in a Northern California river during summer base flow reveal that they have large effects on predators, herbivores, and plants in river food webs. California roach and juvenile steelhead consume predatory insects and fish fry, which feed on algivorous chironomid larvae. In the presence of fish, filamentous green algae are reduced to low, prostrate webs, infested with chironomids. When the absence of large fish releases smaller predators that suppress chironomids, algal biomass is higher, and tall upright algal turfs become covered with diatoms and cyanobacteria. These manipulations provide evidence that the Hairston, Smith, Slobodkin-Fretwell theory of trophic control, which predicts that plants will be alternately limited by resources or herbivores in food webs with odd and even numbers of trophic levels, has application to river communitics. PMID:17759974

Power, M E

1990-11-01

51

Ecosystem Models: Food webs How should components of the food web be represented in  

E-print Network

-1175. Two trophic pathways ­ Auxis, cephalopods Epipelagic Mesopelagic #12;Prey size distributions Prey Size, cephalopods) Higher daily rations Lower daily rations Larger prey sizes Smaller prey sizes Shorter food webs

Hawai'i at Manoa, University of

52

Models of food web evolution Alan J. McKane  

E-print Network

. If there are similarities between food webs in such diverse communities (for instance, marine, desert or lake communitiesModels of food web evolution Alan J. McKane Barbara Drossel While it is often possible to model of possible networks. Here we argue, in the context of food webs, that it is necessary to go beyond simply

McKane, Alan

53

Development and Verification of a Benthic/Pelagic Food Web  

E-print Network

Development and Verification of a Benthic/Pelagic Food Web Bioaccumulation Model for PCB Congeners for environmental managers. Food web bioaccumulation models have been developed that account for many of this model to predict contaminant transfer in a complex food web and its potential applicability to other

Gobas, Frank

54

DISTRIBUTION OF PHTHALATE MONOESTERS IN AN AQUATIC FOOD WEB  

E-print Network

web; bioaccumulation; metabolism Subject Terms: phthalate esters -- toxicology; food chains (ecologyDISTRIBUTION OF PHTHALATE MONOESTERS IN AN AQUATIC FOOD WEB by Maggie L. McConnell B: Distribution of Phthalate Monoesters in an Aquatic Food Web Report No.: 426 Examining Committee

55

Warmer Oceans Affect Food Web  

NSDL National Science Digital Library

In this video, students learn that the Exxon Valdez oil spill in Alaska in 1989 was not the sole cause of the decline of species in the local ecosystem. Rather, an explanation is posited for why some animal populations were already in decline when the spill occurred. Many of these animals share a common food: the sand lance, a fish whose populations have shrunk with the steady rise in ocean temperature that began in the late 1970s.

KTOO

56

Mycoloop: chytrids in aquatic food webs  

PubMed Central

Parasites are ecologically significant in various ecosystems through their role in shaping food web structure, facilitating energy transfer, and controlling disease. Here in this review, we mainly focus on parasitic chytrids, the dominant parasites in aquatic ecosystems, and explain their roles in aquatic food webs, particularly as prey for zooplankton. Chytrids have a free-living zoosporic stage, during which they actively search for new hosts. Zoospores are excellent food for zooplankton in terms of size, shape, and nutritional quality. In the field, densities of chytrids can be high, ranging from 101 to 109 spores L?1. When large inedible phytoplankton species are infected by chytrids, nutrients within host cells are transferred to zooplankton via the zoospores of parasitic chytrids. This new pathway, the “mycoloop,” may play an important role in shaping aquatic ecosystems, by altering sinking fluxes or determining system stability. The grazing of zoospores by zooplankton may also suppress outbreaks of parasitic chytrids. A food web model demonstrated that the contribution of the mycoloop to zooplankton production increased with nutrient availability and was also dependent on the stability of the system. Further studies with advanced molecular tools are likely to discover greater chytrid diversity and evidence of additional mycoloops in lakes and oceans. PMID:24795703

Kagami, Maiko; Miki, Takeshi; Takimoto, Gaku

2014-01-01

57

The Antarctic Ecosystem: Where Would It Be Without Krill?  

NSDL National Science Digital Library

This lesson plan asks students to investigate the importance of krill to the Antarctic ecosystem by researching the animals that depend on it. Students will read and answer questions about krill; research Antarctic animals and take note of the place of each animal in the food chain; and draw an Antarctic food web, using the animals they have researched. They will conclude by writing paragraphs explaining the potential consequences of a decline in krill populations.

58

Parasites in food webs: the ultimate missing links  

PubMed Central

Parasitism is the most common consumer strategy among organisms, yet only recently has there been a call for the inclusion of infectious disease agents in food webs. The value of this effort hinges on whether parasites affect food-web properties. Increasing evidence suggests that parasites have the potential to uniquely alter food-web topology in terms of chain length, connectance and robustness. In addition, parasites might affect food-web stability, interaction strength and energy flow. Food-web structure also affects infectious disease dynamics because parasites depend on the ecological networks in which they live. Empirically, incorporating parasites into food webs is straightforward. We may start with existing food webs and add parasites as nodes, or we may try to build food webs around systems for which we already have a good understanding of infectious processes. In the future, perhaps researchers will add parasites while they construct food webs. Less clear is how food-web theory can accommodate parasites. This is a deep and central problem in theoretical biology and applied mathematics. For instance, is representing parasites with complex life cycles as a single node equivalent to representing other species with ontogenetic niche shifts as a single node? Can parasitism fit into fundamental frameworks such as the niche model? Can we integrate infectious disease models into the emerging field of dynamic food-web modelling? Future progress will benefit from interdisciplinary collaborations between ecologists and infectious disease biologists. PMID:18462196

Lafferty, Kevin D; Allesina, Stefano; Arim, Matias; Briggs, Cherie J; De Leo, Giulio; Dobson, Andrew P; Dunne, Jennifer A; Johnson, Pieter T J; Kuris, Armand M; Marcogliese, David J; Martinez, Neo D; Memmott, Jane; Marquet, Pablo A; McLaughlin, John P; Mordecai, Erin A; Pascual, Mercedes; Poulin, Robert; Thieltges, David W

2008-01-01

59

Plankton, antarctic food chain base, respond to increased ultraviolet radiation  

SciTech Connect

With the growth of the austral spring ozone hole phytoplankton in antarctic waters beneath the depleted ozone layer are now being exposed to twice the amount of ultraviolet radiation as organisms outside the hole. This briefly describes the results of a major study examining this issue. A significant observation was a decrease in phytoplankton production by a minimum of 6-12 percent. Implications for other life forms are discussed briefly along with the effects of increased UV light on the whole ecosystem.

Dybas, C.

1992-12-01

60

Columbia River Food Webs: Developing a Broader Scientific Foundation for  

E-print Network

Columbia River Food Webs: Developing a Broader Scientific Foundation for Fish and Wildlife and Conservation Council #12;i Columbia River Food Webs: Developing a Broader Scientific Foundation for Fish and Conservation Council Intern Eric Schrepel, Technical and Web Data Specialist, Northwest Power

61

Gaining insight into food webs reconstructed by the inverse method  

NASA Astrophysics Data System (ADS)

The use of the inverse method to analyze flow patterns of organic components in ecological systems has had wide application in ecological modeling. Through this approach, an infinite number of food web flows describing the food web and satisfying biological constraints are generated, from which one (parsimonious) solution is drawn. Here we address two questions: (1) is there justification for the use of the parsimonious solution or is there a better alternative and (2) can we use the infinitely many solutions that describe the same food web to give more insight into the system? We reassess two published food webs, from the Gulf of Riga in the Baltic Sea and the Takapoto Atoll lagoon in the South Pacific. A finite number of random food web solutions is first generated using the Monte Carlo simulation technique. Using the Wilcoxon signed ranks test, we cannot find significant differences in the parsimonious solution and the average values of the finite random solutions generated. However, as the food web composed of the average flows has more attractive properties, the choice of the parsimonious solution to describe underdetermined food webs is challenged. We further demonstrate the use of the factor analysis technique to characterize flows that are closely related in the food web. Through this process sub-food webs are extracted within the plausible set of food webs, a property that can be utilized to gain insight into the sampling strategy for further constraining of the model.

Kones, Julius K.; Soetaert, Karline; van Oevelen, Dick; Owino, John O.; Mavuti, Kenneth

2006-04-01

62

Allometric degree distributions facilitate food-web stability  

Microsoft Academic Search

In natural ecosystems, species are linked by feeding interactions that determine energy fluxes and create complex food webs. The stability of these food webs1,2 enables many species to coexist and to form diverse ecosystems. Recent theory finds predator-prey body-mass ratios to be critically important for food-web stability3-5.However,themechanismsresponsibleforthisstability areunclear.Hereweuseabioenergeticconsumer-resourcemodel6 to explore how and why only particular predator-prey body-mass ratios promote stability

Björn C. Rall; Ulrich Brose; Sonja B. Otto

2007-01-01

63

Allometric degree distributions facilitate food-web stability  

Microsoft Academic Search

In natural ecosystems, species are linked by feeding interactions that determine energy fluxes and create complex food webs. The stability of these food webs enables many species to coexist and to form diverse ecosystems. Recent theory finds predator-prey body-mass ratios to be critically important for food-web stability. However, the mechanisms responsible for this stability are unclear. Here we use a

Sonja B. Otto; Björn C. Rall; Ulrich Brose

2007-01-01

64

Metacommunity theory explains the emergence of food web complexity.  

PubMed

Food webs are highly complex ecological networks, dynamic in both space and time. Metacommunity models are now at the core of unified theories of biodiversity, but to date they have not addressed food web complexity. Here we show that metacommunity theory can explain the emergence of species-rich food webs with complex network topologies. Our analysis shows that network branching in the food web is maximized at intermediate colonization rates and limited dispersal scales, which also leads to concomitant peaks in species diversity. Increased food web complexity and species diversity are made possible by the structural role played by network branches that are supported by omnivore and generalist feeding links. Thus, in contrast to traditional food web theory, which emphasizes the destabilizing effect of omnivory feeding in closed systems, metacommunity theory predicts that these feeding links, which are commonly observed in empirical food webs, play a critical structural role as food webs assemble in space. As this mechanism functions at the metacommunity level, evidence for its operation in nature will be obtained through multiscale surveys of food web structure. Finally, we apply our theory to reveal the effects of habitat destruction on network complexity and metacommunity diversity. PMID:22084089

Pillai, Pradeep; Gonzalez, Andrew; Loreau, Michel

2011-11-29

65

The Disruption of Coastal Food Webs  

NSDL National Science Digital Library

This week's In The News addresses recent findings (published in the October 16, 1998 issue of Science) that killer whale predation on sea otters in the North Pacific has "created an ecological chain reaction in nearshore ecosystems." Such ecological chain reactions refer to the disruption of the complex balance between predator and prey species. Killer whales, which traditionally fed on the (now scarce) Steller sea lions and harbor seals, have recently shifted their diet to sea otters. The resulting decline in sea otters has, in turn, led to an increase in sea urchins (sea otter prey), which in turn have deforested many kelp (seaweed) beds in the nearshore marine community. Although killer whales are playing a critical role in the current disruption, this chain of interactions "was probably initiated by anthropogenic changes in the offshore oceanic ecosystem" -- namely, the region's burgeoning fisheries, higher ocean temperatures, and the depletion of baleen whales. Similar "trophic cascades" have been well documented for lakes and in other systems (e.g. Snow Geese in the Arctic), but this research provides a new example of a disrupted food web that may reach a wider audience -- as it involves several highly charismatic vertebrates. The nine resources discussed describe the recent scientific findings, provide background information on food webs, and offer several resources for understanding ecological (trophic) chain reactions.

Payne, Laura X.

1998-01-01

66

The microbial food web along salinity gradients.  

PubMed

The microbial food web was studied along a gradient of salinity in two solar salterns used for the commercial production of salt. The different ponds in the salterns provide a wide range of ecosystems with food webs of different complexities. Abundance of prokaryotes, cell volume, prokaryotic heterotrophic production, chlorophyll a, abundance of heterotrophic flagellates, ciliates and phytoplankton were determined in several ponds in each saltern. Increases in salinity resulted in a progressive reduction in the abundance and number of different groups of eukaryotic microorganisms present, but an increase in biomass of prokaryotes. Maximal activity of both phyto- and bacterioplankton was found at a salinity of around 100 per thousand, where there was also a maximum in chlorophyll a concentration. Growth rates of heterotrophic prokaryotes decreased with increasing salinity. Bacterivory disappeared above 250 per thousand salinity, whereas other loss factors such as viral lysis appeared to be of minor importance throughout the gradient [Guixa-Boixereu et al. (1996) Aquat. Microb. Ecol. 11, 215-227]. PMID:10817867

Pedrós-Alió; Calderón-Paz; MacLean; Medina; Marrasé; Gasol; Guixa-Boixereu

2000-04-01

67

TOP-DOWN AND BOTTOM-UP EFFECTS IN A DETRITAL FOOD WEB: THE PITCHER PLANT INQUILINE COMMUNITY AS A MODEL FOOD WEB  

E-print Network

TOP-DOWN AND BOTTOM-UP EFFECTS IN A DETRITAL FOOD WEB: THE PITCHER PLANT INQUILINE COMMUNITY;TOP-DOWN AND BOTTOM-UP EFFECTS IN A DETRITAL FOOD WEB: THE PITCHER PLANT INQUILINE COMMUNITY that regulate food web dynamics. Both top-down and bottom-up forces affect populations within a food web

Notre Dame, University of

68

Host Centrality in Food Web Networks Determines Parasite Diversity  

PubMed Central

Background Parasites significantly alter topological metrics describing food web structure, yet few studies have explored the relationship between food web topology and parasite diversity. Methods/Principal Findings This study uses quantitative metrics describing network structure to investigate the relationship between the topology of the host food web and parasite diversity. Food webs were constructed for four restored brackish marshes that vary in species diversity, time post restoration and levels of parasitism. Our results show that the topology of the food web in each brackish marsh is highly nested, with clusters of generalists forming a distinct modular structure. The most consistent predictors of parasite diversity within a host were: trophic generality, and eigenvector centrality. These metrics indicate that parasites preferentially colonise host species that are highly connected, and within modules of tightly interacting species in the food web network. Conclusions/Significance These results suggest that highly connected free-living species within the food web may represent stable trophic relationships that allow for the persistence of complex parasite life cycles. Our data demonstrate that the structure of host food webs can have a significant effect on the establishment of parasites, and on the potential for evolution of complex parasite life cycles. PMID:22046360

Anderson, Tavis K.; Sukhdeo, Michael V. K.

2011-01-01

69

Bioaccumulation of Toxaphene Congeners in the Lake Superior Food Web  

Microsoft Academic Search

The bioaccumulation and biotransformation of toxaphene was examined in the food webs of Lake Superior and Siskiwit Lake (Isle Royale) using congener specific analysis as well as stable isotope ratios of carbon and nitrogen to characterize food webs. Toxaphene concentrations (calculated using technical toxaphene) in lake trout (Salvelinus namaycush) from the western basin of Lake Superior (N = 95) averaged

Derek C. G. Muir; D. Michael Whittle; David S. De Vault; Charles R. Bronte; Heidi Karlsson; Sean Backus; Camilla Teixeira

2004-01-01

70

Investigation a food web: producers, consumers, and decomposers  

NSDL National Science Digital Library

This activity is a field investigation where students list plants and animals they observe. Students will organize their data as producers, consumers, or decomposers and create a food web showing how they affect each other. They will predict what will happen if the food web becomes imbalanced by extinction or over population.

71

Two Degrees of Separation in Complex Food Webs  

Microsoft Academic Search

Feeding relationships can cause invasions, extirpations, and population fluctuations of a species to dramatically affect other species within a variety of natural habitats. Such strong effects rarely propagate through food webs more than three links away from the initial perturbation. However, in large food webs the number of species within these spheres of potential influence are generally unknown. Here we

Richard J. Williams; Neo D. Martinez; Eric L. Berlow; Jennifer A. Dunne; Albert-Laszlo Barabasi

2001-01-01

72

A "Bottom-Up" Approach to Food Web Construction  

ERIC Educational Resources Information Center

The ability to comprehend trophic (nutritional) relationships and food web dynamics is an essential part of environmental literacy. However, students face severe difficulties in grasping the variety of causal patterns in food webs. We propose a curriculum for comprehending trophic relations in elementary school. The curriculum allows students to…

Demetriou, Dorita; Korfiatis, Konstantinos; Constantinou, Constantinos

2009-01-01

73

Experimental Ecology of Food Webs: Complex Systems in Temporary Ponds  

Microsoft Academic Search

A food web graphically represents the paths of nutrients and energy through the living components of an ecosystem and the context in which individuals exploit their prey and avoid their enemies. Temporary ponds are excellent arenas for the study of food webs because they are discrete communities that can be mimicked in containers that approach the realism of natural habitats.

Henry M. Wilbur

1997-01-01

74

Complex interactions in microbial food webs: Stoichiometric and functional approaches  

Microsoft Academic Search

The food web structure in some high mountain lakes deviates from the established tendency of high heterotrophic bacteria: phyto- plankton biomass ratios in oligotrophic ecosystems. Thus, the microbial food web in La Caldera Lake is weakly developed, and bacteria constitute a minor component of the plankton community in terms of abundance, biomass and production. Autotrophic picoplankton is absent, and heterotrophic

Presentación Carrillo; Juan Manuel Medina-Sánchez; Manuel Villar-Argaiz; José Antonio Delgado-Molina; Francisco José Bullejos

75

CONTROLS ON FOOD WEBS IN GRAVEL-BEDDED RIVERS: THE  

E-print Network

to their life histories and seasonal phenologies, and the states of the physical environments, food webs and ecosystems in which they are embedded. Feedbacks between organisms, environment, and ecosystems occur over, marine, or lentic) habitats. Food web models provide one conceptual framework for organizing our efforts

Power, Mary Eleanor

76

Staff summary of Issues & Recommendations Predation and Food Webs  

E-print Network

1 Staff summary of Issues & Recommendations Predation and Food Webs *Preliminary draft, please and Food Webs Specific Language Changes NOAA Fisheries recommends the following new language in the Habitat: The Program should support, and BPA should fund, additional research into the overall magnitude of the impacts

77

Mercury bioaccumulation in estuarine food webs.  

PubMed

We tested for unintended mercury contamination problems associated with estuarine floodplain restoration projects of the Louisiana coastal zone, USA. Barataria Bay and Breton Sound are two neighboring deltaic estuaries that were isolated by levees from the Mississippi River about 100 years ago. These estuaries recently have been reconnected to the nutrient-rich Mississippi River, starting major river diversion (input) flows in 1991 for Breton Sound and in 2004 for Barataria Bay. We collected > 2100 fish over five years from 20 stations in these estuaries to test two hypotheses about Hg bioaccumulation: (H1) Background Hg bioaccumulation in fish would be highest in low-salinity upper reaches of estuaries, and (H2) recent river inputs to these upper estuarine areas would increase Hg bioaccumulation in fish food webs. For H1, we surveyed fish Hg concentrations at several stations along a salinity gradient in Barataria Bay in 2003-2004, a time when this estuary lacked strong river inputs. Results showed that average Hg concentrations in fish communities were lowest (150 ng/g dry mass) in higher salinity areas and -2.4x higher (350 ng/g) in low-salinity oligohaline and freshwater upper reaches of the estuary. For H2, we tested for enhanced Hg bioaccumulation following diversion onset in both estuaries. Fish communities from Breton Sound that had long-term (> 10 years) diversion inputs had -1.7x higher average Hg contents of 610 ng/g Hg vs. 350 ng/g background values. Shorter-term diversion inputs over 2-3 years in upper Barataria Bay did not result in strong Hg enrichments or stable C isotope increases seen in Breton Sound, even though N and S stable-isotope values indicated strong river inputs in both estuaries. It may be that epiphyte communities on abundant submerged aquatic vegetation (SAV) are important hotspots for Hg cycling in these estuaries, and observed lesser development of these epiphyte communities in upper Barataria Bay during the first years of diversion inputs may account for the lessened Hg bioaccumulation in fish. A management consideration from this study is that river restoration projects may unintentionally fertilize SAV and epiphyte-based food webs, leading to higher Hg bioaccumulation in river-impacted floodplains and their food webs. PMID:22611858

Fry, Brian; Chumchal, Matthew M

2012-03-01

78

Characteristics of Food Industry Web Sites and "Advergames" Targeting Children  

ERIC Educational Resources Information Center

Objective: To assess the content of food industry Web sites targeting children by describing strategies used to prolong their visits and foster brand loyalty; and to document health-promoting messages on these Web sites. Design: A content analysis was conducted of Web sites advertised on 2 children's networks, Cartoon Network and Nickelodeon. A…

Culp, Jennifer; Bell, Robert A.; Cassady, Diana

2010-01-01

79

The Food Web Matching Game: A Missing Link  

NSDL National Science Digital Library

This extension activity challenges students to answer hypothetical questions about a marine food web they have created. They are asked to hypothesize what might happen if a top predator like the killer whale became extinct, or if fish from the middle levels of the web were overfished, or if a primary producer such as algae were removed from the web.

80

TOWARD AN INTEGRATION OF LANDSCAPE AND FOOD WEB ECOLOGY:The Dynamics of Spatially Subsidized Food Webs  

Microsoft Academic Search

We focus on the implications of movement, landscape variables, and spatial het- erogeneity for food web dynamics. Movements of nutrients, detritus, prey, and consumers among habitats are ubiquitous in diverse biomes and can strongly influence population, consumer-resource, food web, and community dynamics. Nutrient and detrital subsidies usually increase primary and secondary produc- tivity, both directly and indirectly. Prey subsidies, by

Gary A. Polis; Wendy B. Anderson; Robert D. Holt

1997-01-01

81

Amphipod-supported food web: Themisto gaudichaudii, a key food resource for fishes in the southern Patagonian Shelf  

NASA Astrophysics Data System (ADS)

The trophic role of the hyperiid amphipod Themisto gaudichaudii in the southern Patagonian shelf food web was assessed from the analysis of stomach contents of the local fish assemblage. A total of 461 trawl samples were collected during seven seasonal cruises. A total of 17 out of 38 fish species were found to ingest T. gaudichaudii. This amphipod was a main prey item in five of these species, showing high values of alimentary index: Seriolella porosa (99.9%), Macruronus magellanicus (68.8%), Micromesistius australis (59.1%), Patagonotothen ramsayi (48.6%), and Merluccius hubbsi (10.9%). The contribution of T. gaudichaudii, in weight, to their summer diet was 60%, on average. This contribution was minimal in winter and maximal in summer. Fisheries studies have indicated that these five species, mainly M. magellanicus, account for almost 85% of the fish biomass in the area. Although the remaining 15% did not feed heavily on T. gaudichaudii, they are known to prey on the main hyperiid predators. Our study shows that T. gaudichaudii contributes greatly, both directly and indirectly, to supporting the fish community. We thus proposed that T. gaudichaudii plays a key role as a "wasp-waist" species in the sub-Antarctic region, similar to that of krill in Antarctic waters, channeling the energy flow and enabling a short and efficient food chain.

Padovani, Luciano N.; Viñas, María Delia; Sánchez, Felisa; Mianzan, Hermes

2012-01-01

82

Food-web dynamics in a large river discontinuum  

USGS Publications Warehouse

Nearly all ecosystems have been altered by human activities, and most communities are now composed of interacting species that have not co-evolved. These changes may modify species interactions, energy and material flows, and food-web stability. Although structural changes to ecosystems have been widely reported, few studies have linked such changes to dynamic food-web attributes and patterns of energy flow. Moreover, there have been few tests of food-web stability theory in highly disturbed and intensely managed freshwater ecosystems. Such synthetic approaches are needed for predicting the future trajectory of ecosystems, including how they may respond to natural or anthropogenic perturbations. We constructed flow food webs at six locations along a 386-km segment of the Colorado River in Grand Canyon (Arizona, USA) for three years. We characterized food-web structure and production, trophic basis of production, energy efficiencies, and interaction-strength distributions across a spatial gradient of perturbation (i.e., distance from Glen Canyon Dam), as well as before and after an experimental flood. We found strong longitudinal patterns in food-web characteristics that strongly correlated with the spatial position of large tributaries. Above tributaries, food webs were dominated by nonnative New Zealand mudsnails (62% of production) and nonnative rainbow trout (100% of fish production). The simple structure of these food webs led to few dominant energy pathways (diatoms to few invertebrate taxa to rainbow trout), large energy inefficiencies (i.e., Below large tributaries, invertebrate production declined ?18-fold, while fish production remained similar to upstream sites and comprised predominately native taxa (80–100% of production). Sites below large tributaries had increasingly reticulate and detritus-based food webs with a higher prevalence of omnivory, as well as interaction strength distributions more typical of theoretically stable food webs (i.e., nearly twofold higher proportion of weak interactions). Consistent with theory, downstream food webs were less responsive to the experimental flood than sites closest to the dam. We show how human-induced shifts to food-web structure can affect energy flow and interaction strengths, and we show that these changes have consequences for food-web function and response to perturbations.

Cross, Wyatt F.; Baxter, Colden V.; Rosi-Marshall, Emma J.; Hall, Robert O., Jr.; Kennedy, Theodore A.; Donner, Kevin C.; Kelly, Holly A. Wellard; Seegert, Sarah E.Z.; Behn, Kathrine E.; Yard, Michael D.

2013-01-01

83

Food Web Structure in a Harsh Glacier-Fed River  

PubMed Central

Glacier retreat is occurring across the world, and associated river ecosystems are expected to respond more rapidly than those in flowing waters in other regions. The river environment directly downstream of a glacier snout is characterised by extreme low water temperature and unstable channel sediments but these habitats may become rarer with widespread glacier retreat. In these extreme environments food web dynamics have been little studied, yet they could offer opportunities to test food web theories using highly resolved food webs owing to their low taxonomic richness. This study examined the interactions of macroinvertebrate and diatom taxa in the Ödenwinkelkees river, Austrian central Alps between 2006 and 2011. The webs were characterised by low taxon richness (13–22), highly connected individuals (directed connectance up to 0.19) and short mean food chain length (2.00–2.36). The dominant macroinvertebrates were members of the Chironomidae genus Diamesa and had an omnivorous diet rich in detritus and diatoms as well as other Chironomidae. Simuliidae (typically detritivorous filterers) had a diet rich in diatoms but also showed evidence of predation on Chironomidae larvae. Food webs showed strong species-averaged and individual size structuring but mass-abundance scaling coefficients were larger than those predicted by metabolic theory, perhaps due to a combination of spatial averaging effects of patchily distributed consumers and resources, and/or consumers deriving unquantified resources from microorganisms attached to the large amounts of ingested rock fragments. Comparison of food web structural metrics with those from 62 published river webs suggest these glacier-fed river food web properties were extreme but in line with general food web scaling predictions, a finding which could prove useful to forecast the effects of anticipated future glacier retreat on the structure of aquatic food webs. PMID:23613751

Clitherow, Leonie R.; Carrivick, Jonathan L.; Brown, Lee E.

2013-01-01

84

Adaptations in a hierarchical food web of southeastern Lake Michigan  

USGS Publications Warehouse

Two issues in ecological network theory are: (1) how to construct an ecological network model and (2) how do entire networks (as opposed to individual species) adapt to changing conditions? We present a novel method for constructing an ecological network model for the food web of southeastern Lake Michigan (USA) and we identify changes in key system properties that are large relative to their uncertainty as this ecological network adapts from one time point to a second time point in response to multiple perturbations. To construct our food web for southeastern Lake Michigan, we followed the list of seven recommendations outlined in Cohen et al. [Cohen, J.E., et al., 1993. Improving food webs. Ecology 74, 252–258] for improving food webs. We explored two inter-related extensions of hierarchical system theory with our food web; the first one was that subsystems react to perturbations independently in the short-term and the second one was that a system's properties change at a slower rate than its subsystems’ properties. We used Shannon's equations to provide quantitative versions of the basic food web properties: number of prey, number of predators, number of feeding links, and connectance (or density). We then compared these properties between the two time-periods by developing distributions of each property for each time period that took uncertainty about the property into account. We compared these distributions, and concluded that non-overlapping distributions indicated changes in these properties that were large relative to their uncertainty. Two subsystems were identified within our food web system structure (p < 0.001). One subsystem had more non-overlapping distributions in food web properties between Time 1 and Time 2 than the other subsystem. The overall system had all overlapping distributions in food web properties between Time 1 and Time 2. These results supported both extensions of hierarchical systems theory. Interestingly, the subsystem with more non-overlapping distributions in food web properties was the subsystem that contained primarily benthic taxa, contrary to expectations that the identified major perturbations (lower phosphorous inputs and invasive species) would more greatly affect the subsystem containing primarily pelagic taxa. Future food-web research should employ rigorous statistical analysis and incorporate uncertainty in food web properties for a better understanding of how ecological networks adapt.

Krause, Ann E.; Frank, Ken A.; Jones, Michael L.; Nalepa, Thomas F.; Barbiero, Richard P.; Madenjian, Charles P.; Agy, Megan; Evans, Marlene S.; Taylor, William W.; Mason, Doran M.; Leonard, Nancy J.

2009-01-01

85

RAPID COMMUNICATION / COMMUNICATION RAPIDE Simplified food webs lead to energetic  

E-print Network

diet and community analysis indicated that the food web leading to yellow perch (Perca flavescens nourriture disponible aux perchaudes (Perca flavescens) provenant de lacs pollués par les métaux lourds a été

Hontela, Alice

86

Tracking contaminant flux from aquatic to terrestrial food webs  

EPA Science Inventory

Aquatic insects provide a critical energy subsidy to riparian food webs, yet their role as vectors of contaminants to terrestrial ecosystems is poorly understood. We investigated aquatic resource utilization and contaminant exposure among riparian invertivores (spiders and herpt...

87

Barcoding a quantified food web: crypsis, concepts, ecology and hypotheses.  

PubMed

The efficient and effective monitoring of individuals and populations is critically dependent on correct species identification. While this point may seem obvious, identifying the majority of the more than 100 natural enemies involved in the spruce budworm (Choristoneura fumiferana--SBW) food web remains a non-trivial endeavor. Insect parasitoids play a major role in the processes governing the population dynamics of SBW throughout eastern North America. However, these species are at the leading edge of the taxonomic impediment and integrating standardized identification capacity into existing field programs would provide clear benefits. We asked to what extent DNA barcoding the SBW food web would alter our understanding of the diversity and connectence of the food web and the frequency of generalists vs. specialists in different forest habitats. We DNA barcoded over 10% of the insects collected from the SBW food web in three New Brunswick forest plots from 1983 to 1993. For 30% of these specimens, we amplified at least one additional nuclear region. When the nodes of the food web were estimated based on barcode divergences (using molecular operational taxonomic units (MOTU) or phylogenetic diversity (PD)--the food web became much more diverse and connectence was reduced. We tested one measure of food web structure (the "bird feeder effect") and found no difference compared to the morphologically based predictions. Many, but not all, of the presumably polyphagous parasitoids now appear to be morphologically-cryptic host-specialists. To our knowledge, this project is the first to barcode a food web in which interactions have already been well-documented and described in space, time and abundance. It is poised to be a system in which field-based methods permit the identification capacity required by forestry scientists. Food web barcoding provided an effective tool for the accurate identification of all species involved in the cascading effects of future budworm outbreaks. Integrating standardized barcodes within food webs may ultimately change the face of community ecology. This will be most poignantly felt in food webs that have not yet been quantified. Here, more accurate and precise connections will be within the grasp of any researcher for the first time. PMID:21754977

Smith, M Alex; Eveleigh, Eldon S; McCann, Kevin S; Merilo, Mark T; McCarthy, Peter C; Van Rooyen, Kathleen I

2011-01-01

88

Quantification and Resolution of a Complex, Size-Structured Food Web  

E-print Network

Quantification and Resolution of a Complex, Size-Structured Food Web GUY WOODWARD, DOUGIE C. SPEIRS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 A. Connectance Food Webs: Early Patterns and Recent Advances . . 87 B. Quantified Food Webs: From Pattern to Process . . . . . . . . . . . . . 90 C. The Broadstone Stream Food Web

Mottram, Nigel

89

Complex food webs prevent competitive exclusion among producer species  

Microsoft Academic Search

Herbivorous top-down forces and bottom-up competition for nutrients determine the coexistence and relative biomass patterns of producer species. Combining models of predator-prey and producer-nutrient interactions with a structural model of complex food webs, I investigated these two aspects in a dynamic food-web model. While competitive exclusion leads to persistence of only one producer species in 99.7% of the simulated simple

Ulrich Brose

2008-01-01

90

Web-based expert system for food dryer selection  

Microsoft Academic Search

This paper describes an integrated web-based fuzzy expert system for food dryer selection. A modular approach to designing the system was employed. It consists of a number of knowledge sources controlled by a scheduler, which communicate through a common blackboard. The system has been fully implemented to run on the web and provides an excellent example of how a number

Haitham M. S. Lababidi; Christopher G. J. Baker

2003-01-01

91

Genetic variation, predator–prey interactions and food web structure  

PubMed Central

Food webs are networks of species that feed on each other. The role that within-population phenotypic and genetic variation plays in food web structure is largely unknown. Here, I show via simulation how variation in two key traits, growth rates and phenology, by influencing the variability of body sizes present through time, can potentially affect several structural parameters in the direction of enhancing food web persistence: increased connectance, decreased interaction strengths, increased variation among interaction strengths and increased degree of omnivory. I discuss other relevant traits whose variation could affect the structure of food webs, such as morphological and additional life-history traits, as well as animal personalities. Furthermore, trait variation could also contribute to the stability of food web modules through metacommunity dynamics. I propose future research to help establish a link between within-population variation and food web structure. If appropriately established, such a link could have important consequences for biological conservation, as it would imply that preserving (functional) genetic variation within populations could ensure the preservation of entire communities. PMID:21444316

Moya-Laraño, Jordi

2011-01-01

92

Food Safety Resources on the World Wide Web  

Microsoft Academic Search

Issues of food safety are as important today than during any time in history. There is a lot of information available on the World Wide Web pertaining to food safety. Finding and sorting through all of the information for reliable and credible resources can take a lot of time and effort. Furthermore, are those sources updated as information changes? This

Carole Blemker

2006-01-01

93

An experimental test of a fundamental food web motif  

PubMed Central

Large-scale changes to the world's ecosystem are resulting in the deterioration of biostructure—the complex web of species interactions that make up ecological communities. A difficult, yet crucial task is to identify food web structures, or food web motifs, that are the building blocks of this baroque network of interactions. Once identified, these food web motifs can then be examined through experiments and theory to provide mechanistic explanations for how structure governs ecosystem stability. Here, we synthesize recent ecological research to show that generalist consumers coupling resources with different interaction strengths, is one such motif. This motif amazingly occurs across an enormous range of spatial scales, and so acts to distribute coupled weak and strong interactions throughout food webs. We then perform an experiment that illustrates the importance of this motif to ecological stability. We find that weak interactions coupled to strong interactions by generalist consumers dampen strong interaction strengths and increase community stability. This study takes a critical step by isolating a common food web motif and through clear, experimental manipulation, identifies the fundamental stabilizing consequences of this structure for ecological communities. PMID:20129988

Rip, Jason M. K.; McCann, Kevin S.; Lynn, Denis H.; Fawcett, Sonia

2010-01-01

94

PRIMARY RESEARCH PAPER Phytoplankton food quality control of planktonic food web  

E-print Network

of surface water bodies, protect drinking water supplies, and improve fisheries production (Vollenweider to test the effects of phytoplankton food quality for herbivorous zooplankton on planktonic food web, and can have profound effects on water quality and fisheries production. Keywords Phytoplankton food

Arhonditsis, George B.

95

FoodFit: A Web Application to Illustrate Healthier Food and Physical Activity Choices  

E-print Network

FoodFit: A Web Application to Illustrate Healthier Food and Physical Activity Choices Meriyan Eren their lifestyles to include healthier food choices and more frequent physical activities. Lack of motivation your diet with physical activities - Familiar nutrition facts label, colorful bar plots and face

Toronto, University of

96

Development of a Food Web Model (DOVE-Digital Organisms in a Virtual Ecosystem) to Examine Indirect Interactions in Food Webs and  

E-print Network

Development of a Food Web Model (DOVE- Digital Organisms in a Virtual Ecosystem) to Examine computational methods to develop a modeling approach of food webs that allows the incorporation, and examination are developing a computational model to examine food webs. The computational model is designed to address

97

Tracing Food Webs with Stable Hydrogen Isotopes  

Microsoft Academic Search

The hydrogen isotopic content of an animal's food, not water, determines that animal's hydrogen isotopic content. Liver and muscle tissue from mice reared on a diet such that the ratio of deuterium to hydrogen (D\\/H) of their food and water was kept constant, have the same average D\\/H ratio as the food source. In a simple, natural population of snails

Marilyn F. Estep; Halina Dabrowski

1980-01-01

98

Effects of Whaling on the Structure of the Southern Ocean Food Web: Insights on the “Krill Surplus” from Ecosystem Modelling  

PubMed Central

The aim of this study was to examine the ecological plausibility of the “krill surplus” hypothesis and the effects of whaling on the Southern Ocean food web using mass-balance ecosystem modelling. The depletion trajectory and unexploited biomass of each rorqual population in the Antarctic was reconstructed using yearly catch records and a set of species-specific surplus production models. The resulting estimates of the unexploited biomass of Antarctic rorquals were used to construct an Ecopath model of the Southern Ocean food web existing in 1900. The rorqual depletion trajectory was then used in an Ecosim scenario to drive rorqual biomasses and examine the “krill surplus” phenomenon and whaling effects on the food web in the years 1900–2008. An additional suite of Ecosim scenarios reflecting several hypothetical trends in Southern Ocean primary productivity were employed to examine the effect of bottom-up forcing on the documented krill biomass trend. The output of the Ecosim scenarios indicated that while the “krill surplus” hypothesis is a plausible explanation of the biomass trends observed in some penguin and pinniped species in the mid-20th century, the excess krill biomass was most likely eliminated by a rapid decline in primary productivity in the years 1975–1995. Our findings suggest that changes in physical conditions in the Southern Ocean during this time period could have eliminated the ecological effects of rorqual depletion, although the mechanism responsible is currently unknown. Furthermore, a decline in iron bioavailability due to rorqual depletion may have contributed to the rapid decline in overall Southern Ocean productivity during the last quarter of the 20th century. The results of this study underscore the need for further research on historical changes in the roles of top-down and bottom-up forcing in structuring the Southern Ocean food web. PMID:25517505

Surma, Szymon; Pakhomov, Evgeny A.; Pitcher, Tony J.

2014-01-01

99

Mercury biomagnification in marine zooplankton food webs in Hudson Bay.  

PubMed

While much research has been carried out on mercury in large marine mammals and associated food webs in northern regions, comparatively less has been conducted on lower trophic levels including zooplankton and the subsequent transfer to predators, which marks the entry of mercury into northern marine food webs. We present here the first database for mercury uptake and transfer exclusively within zooplankton food webs in northern marine waters. We have investigated both total (THg) and monomethylmercury (MMHg) concentrations, and isotopic signatures (?(15)N and ?(13)C) in individual zooplankton taxa collected over a period of eight years (2003-2010) from across Hudson Bay (including Hudson Strait and Foxe Basin) as part of research icebreaker cruises. ?(15)N values ranged from 3.4 to 14.0‰, implying trophic levels ranging from 1 to 4, and THg concentrations ranged from 5 to 242 ng g(-1) dw. Food web linkages were identified within the data set, and mercury biomagnification was evident both with THg and MMHg concentrations increasing from prey to predator, and with trophic magnification factors (TMFs). Total mercury and MMHg transfer in a unique prey-predator linkage (Limacina helicina-Clione limacina) are investigated and discussed with regard to known physiological and biochemical characteristics. The results suggest that exposure to mercury at higher trophic levels including humans can be affected by processes at the bottom of Arctic marine food webs. PMID:23157666

Foster, Karen L; Stern, Gary A; Pazerniuk, Monica A; Hickie, Brendan; Walkusz, Wojciech; Wang, Feiyue; Macdonald, Robie W

2012-12-01

100

Key Features of Intertidal Food Webs That Support Migratory Shorebirds  

PubMed Central

The migratory shorebirds of the East Atlantic flyway land in huge numbers during a migratory stopover or wintering on the French Atlantic coast. The Brouage bare mudflat (Marennes-Oléron Bay, NE Atlantic) is one of the major stopover sites in France. The particular structure and function of a food web affects the efficiency of carbon transfer. The structure and functioning of the Brouage food web is crucial for the conservation of species landing within this area because it provides sufficient food, which allows shorebirds to reach the north of Europe where they nest. The aim of this study was to describe and understand which food web characteristics support nutritional needs of birds. Two food-web models were constructed, based on in situ measurements that were made in February 2008 (the presence of birds) and July 2008 (absence of birds). To complete the models, allometric relationships and additional data from the literature were used. The missing flow values of the food web models were estimated by Monte Carlo Markov Chain – Linear Inverse Modelling. The flow solutions obtained were used to calculate the ecological network analysis indices, which estimate the emergent properties of the functioning of a food-web. The total activities of the Brouage ecosystem in February and July are significantly different. The specialisation of the trophic links within the ecosystem does not appear to differ between the two models. In spite of a large export of carbon from the primary producer and detritus in winter, the higher recycling leads to a similar retention of carbon for the two seasons. It can be concluded that in February, the higher activity of the ecosystem coupled with a higher cycling and a mean internal organization, ensure the sufficient feeding of the migratory shorebirds. PMID:24204666

Saint-Béat, Blanche; Dupuy, Christine; Bocher, Pierrick; Chalumeau, Julien; De Crignis, Margot; Fontaine, Camille; Guizien, Katell; Lavaud, Johann; Lefebvre, Sébastien; Montanié, Hélène; Mouget, Jean-Luc; Orvain, Francis; Pascal, Pierre-Yves; Quaintenne, Gwenaël; Radenac, Gilles; Richard, Pierre; Robin, Frédéric; Vézina, Alain F.; Niquil, Nathalie

2013-01-01

101

Key features of intertidal food webs that support migratory shorebirds.  

PubMed

The migratory shorebirds of the East Atlantic flyway land in huge numbers during a migratory stopover or wintering on the French Atlantic coast. The Brouage bare mudflat (Marennes-Oléron Bay, NE Atlantic) is one of the major stopover sites in France. The particular structure and function of a food web affects the efficiency of carbon transfer. The structure and functioning of the Brouage food web is crucial for the conservation of species landing within this area because it provides sufficient food, which allows shorebirds to reach the north of Europe where they nest. The aim of this study was to describe and understand which food web characteristics support nutritional needs of birds. Two food-web models were constructed, based on in situ measurements that were made in February 2008 (the presence of birds) and July 2008 (absence of birds). To complete the models, allometric relationships and additional data from the literature were used. The missing flow values of the food web models were estimated by Monte Carlo Markov Chain--Linear Inverse Modelling. The flow solutions obtained were used to calculate the ecological network analysis indices, which estimate the emergent properties of the functioning of a food-web. The total activities of the Brouage ecosystem in February and July are significantly different. The specialisation of the trophic links within the ecosystem does not appear to differ between the two models. In spite of a large export of carbon from the primary producer and detritus in winter, the higher recycling leads to a similar retention of carbon for the two seasons. It can be concluded that in February, the higher activity of the ecosystem coupled with a higher cycling and a mean internal organization, ensure the sufficient feeding of the migratory shorebirds. PMID:24204666

Saint-Béat, Blanche; Dupuy, Christine; Bocher, Pierrick; Chalumeau, Julien; De Crignis, Margot; Fontaine, Camille; Guizien, Katell; Lavaud, Johann; Lefebvre, Sébastien; Montanié, Hélène; Mouget, Jean-Luc; Orvain, Francis; Pascal, Pierre-Yves; Quaintenne, Gwenaël; Radenac, Gilles; Richard, Pierre; Robin, Frédéric; Vézina, Alain F; Niquil, Nathalie

2013-01-01

102

The relationship between the duration of food web evolution and the vulnerability to biological invasion  

Microsoft Academic Search

I conducted computer simulations of food web evolution and investigated the relationship between the duration of food web evolution and the vulnerability to biological invasion. Model food webs without evolution consisted of animal species with a limited number of prey species and producer species with small intrinsic growth rates. Because these species were not resistant to predation pressure, model food

Katsuhiko Yoshida

2008-01-01

103

Food web dynamics in a seasonally varying wetland  

USGS Publications Warehouse

A spatially explicit model is developed to simulate the small fish community and its underlying food web, in the freshwater marshes of the Everglades. The community is simplified to a few small fish species feeding on periphyton and invertebrates. Other compartments are detritus, crayfish, and a piscivorous fish species. This unit food web model is applied to each of the 10,000 spatial cells on a 100 x 100 pixel landscape. Seasonal variation in water level is assumed and rules are assigned for fish movement in response to rising and falling water levels, which can cause many spatial cells to alternate between flooded and dry conditions. It is shown that temporal variations of water level on a spatially heterogeneous landscape can maintain at least three competing fish species. In addition, these environmental factors can strongly affect the temporal variation of the food web caused by top-down control from the piscivorous fish.

DeAngelis, D.L.; Trexler, J.C.; Donalson, D.D.

2008-01-01

104

Infectious disease agents mediate interaction in food webs and ecosystems  

PubMed Central

Infectious agents are part of food webs and ecosystems via the relationship with their host species that, in turn, interact with both hosts and non-hosts. Through these interactions, infectious agents influence food webs in terms of structure, functioning and stability. The present literature shows a broad range of impacts of infectious agents on food webs, and by cataloguing that range, we worked towards defining the various mechanisms and their specific effects. To explore the impact, a direct approach is to study changes in food-web properties with infectious agents as separate species in the web, acting as additional nodes, with links to their host species. An indirect approach concentrates not on adding new nodes and links, but on the ways that infectious agents affect the existing links across host and non-host nodes, by influencing the ‘quality’ of consumer–resource interaction as it depends on the epidemiological state host involved. Both approaches are natural from an ecological point of view, but the indirect approach may connect more straightforwardly to commonly used tools in infectious disease dynamics. PMID:24403336

Selakovic, Sanja; de Ruiter, Peter C.; Heesterbeek, Hans

2014-01-01

105

Extinction risk and structure of a food web model  

NASA Astrophysics Data System (ADS)

We investigate in detail the model of a trophic web proposed by Amaral and Meyer [Phys. Rev. Lett. 82, 652 (1999)]. We focus on small-size systems that are relevant for real biological food webs and for which the fluctuations play an important role. We show, using Monte Carlo simulations, that such webs can be nonviable, leading to extinction of all species in small and/or weakly coupled systems. Estimations of the extinction times and survival chances are also given. We show that before the extinction the fraction of highly connected species (“omnivores”) is increasing. Viable food webs exhibit a pyramidal structure, where the density of occupied niches is higher at lower trophic levels, and moreover the occupations of adjacent levels are closely correlated. We also demonstrate that the distribution of the lengths of food chains has an exponential character and changes weakly with the parameters of the model. On the contrary, the distribution of avalanche sizes of the extinct species depends strongly on the connectedness of the web. For rather loosely connected systems, we recover the power-law type of behavior with the same exponent as found in earlier studies, while for densely connected webs the distribution is not of a power-law type.

P?kalski, Andrzej; Szwabi?ski, Janusz; Bena, Ioana; Droz, Michel

2008-03-01

106

Changes in host-parasitoid food web structure with elevation.  

PubMed

Gradients in elevation are increasingly used to investigate how species respond to changes in local climatic conditions. Whilst many studies have shown elevational patterns in species richness and turnover, little is known about how food web structure is affected by elevation. Contrasting responses of predator and prey species to elevation may lead to changes in food web structure. We investigated how the quantitative structure of a herbivore-parasitoid food web changes with elevation in an Australian subtropical rain forest. On four occasions, spread over 1 year, we hand-collected leaf miners at twelve sites, along three elevational gradients (between 493 m and 1159 m a.s.l). A total of 5030 insects, including 603 parasitoids, were reared, and summary food webs were created for each site. We also carried out a replicated manipulative experiment by translocating an abundant leaf-mining weevil Platynotocis sp., which largely escaped parasitism at high elevations (?900 m a.s.l.), to lower, warmer elevations, to test if it would experience higher parasitism pressure. We found strong evidence that the environmental change that occurs with increasing elevation affects food web structure. Quantitative measures of generality, vulnerability and interaction evenness decreased significantly with increasing elevation (and decreasing temperature), whilst elevation did not have a significant effect on connectance. Mined plant composition also had a significant effect on generality and vulnerability, but not on interaction evenness. Several relatively abundant species of leaf miner appeared to escape parasitism at higher elevations, but contrary to our prediction, Platynotocis sp. did not experience greater levels of parasitism when translocated to lower elevations. Our study indicates that leaf-mining herbivores and their parasitoids respond differently to environmental conditions imposed by elevation, thus producing structural changes in their food webs. Increasing temperatures and changes in vegetation communities that are likely to result from climate change may have a restructuring effect on host-parasitoid food webs. Our translocation experiment, however, indicated that leaf miners currently escaping parasitism at high elevations may not automatically experience higher parasitism under warmer conditions and future changes in food web structure may depend on the ability of parasitoids to adapt to novel hosts. PMID:25244661

Maunsell, Sarah C; Kitching, Roger L; Burwell, Chris J; Morris, Rebecca J

2014-09-22

107

Ecological tracers can quantify food web structure and change.  

PubMed

Disruption of natural food webs is becoming a commonplace occurrence as a result of human activities. Considering this, there is a need to improve our ability to define food web structure as well as to detect and understand the implications of trophodynamic change. This requires the development, validation, and application of ecologicaltracers that can provide insights into the movement of energy, nutrients, and contaminants through food webs. In this study, we examine the utility of two groups of naturally occurring intrinsic tracers (stable nitrogen isotopes and fatty acids) to provide such information in a predatory seabird, the herring gull (Larus argentatus). Spatial and temporal patterns in gull trophic position (inferred from egg stable nitrogen isotope values) were related to gull diet composition (inferred from egg fatty acid concentrations). These two independent groups of ecological tracers provided corroborating evidence that gull trophic position was related to the degree to which aquatic foods, namely fish, were consumed. The use of these tracers in concert led to a better understanding of routes of energy flow and contaminant transfer in food webs and how these pathways may be affected by ecosystem change. PMID:17007117

Hebert, Craig E; Arts, Michael T; Weseloh, D V Chip

2006-09-15

108

DEVELOPMENT OF A STREAM FOOD WEB MODEL CONSTRAINED BY STABLE ISOTOPE DATA  

EPA Science Inventory

Traditional stream food web studies provide static models of trophic structures. These models provide information about interspecific relationships, but not about material flows through food webs. Traditional ecosystem models developed from budgets or tracers provide quantitative...

109

Food-Web Models Predict Species Abundances in Response to Habitat Change  

E-print Network

sizes of food-web constituents than did simple keystone species models, models that included only species effects, which emphasize responses of populations to changes in the abundance of a single keystone species (food- web and keystone species mod

Gotelli, Nicholas J.

110

40 CFR 230.31 - Fish, crustaceans, mollusks, and other aquatic organisms in the food web.  

Code of Federal Regulations, 2011 CFR

40 Protection of Environment 25 2011-07-01...aquatic organisms in the food web. 230.31 Section...31 Protection of Environment ENVIRONMENTAL PROTECTION...aquatic organisms in the food web. (a) Aquatic...persistent synthetic organic chemicals. The...

2011-07-01

111

40 CFR 230.31 - Fish, crustaceans, mollusks, and other aquatic organisms in the food web.  

Code of Federal Regulations, 2013 CFR

40 Protection of Environment 26 2013-07-01...aquatic organisms in the food web. 230.31 Section...31 Protection of Environment ENVIRONMENTAL PROTECTION...aquatic organisms in the food web. (a) Aquatic...persistent synthetic organic chemicals. The...

2013-07-01

112

40 CFR 230.31 - Fish, crustaceans, mollusks, and other aquatic organisms in the food web.  

Code of Federal Regulations, 2014 CFR

40 Protection of Environment 25 2014-07-01...aquatic organisms in the food web. 230.31 Section...31 Protection of Environment ENVIRONMENTAL PROTECTION...aquatic organisms in the food web. (a) Aquatic...persistent synthetic organic chemicals. The...

2014-07-01

113

40 CFR 230.31 - Fish, crustaceans, mollusks, and other aquatic organisms in the food web.  

Code of Federal Regulations, 2012 CFR

40 Protection of Environment 26 2012-07-01...aquatic organisms in the food web. 230.31 Section...31 Protection of Environment ENVIRONMENTAL PROTECTION...aquatic organisms in the food web. (a) Aquatic...persistent synthetic organic chemicals. The...

2012-07-01

114

40 CFR 230.31 - Fish, crustaceans, mollusks, and other aquatic organisms in the food web.  

Code of Federal Regulations, 2010 CFR

40 Protection of Environment 24 2010-07-01...aquatic organisms in the food web. 230.31 Section...31 Protection of Environment ENVIRONMENTAL PROTECTION...aquatic organisms in the food web. (a) Aquatic...persistent synthetic organic chemicals. The...

2010-07-01

115

PERSPECTIVE Dynamics of the Lake Michigan food web,  

E-print Network

in the 1950s and 1960s, had profound effects on the food web. Recoveries of lake whitefish (Coregonus clupeaformis) and burbot (Lota lota) populations, as well as the buildup of salmonine popu- lations, were considérable sur le réseau alimentaire. Le rétablissement des populations du grand corégone (Coregonus

116

Aquatic Food Web Interactions: Microcosms as Lake Models  

NSDL National Science Digital Library

As a laboratory exercise for increasing knowledge of trophic cascades in aquatic ecosystems has led to a better understanding of several basic ecological tenets, including competition, predation, and a variety of other community-level food web interactions using microcosms from whole water plankton collections. This lab exercise incorporates student use of rigorous quantitative skills in enumeration, data collection, and statistical inference.

John C. Holz (University of Nebraska; )

2000-01-01

117

The trophodynamics of PCBs in the Lake Ontario food web  

SciTech Connect

Samples of water, sediment, invertebrates, fish, and herring gull eggs were collected in north-central Lake Ontario and were analyzed to determine the concentrations of PCBs, including non-ortho substituted PCB congeners, in the benthic and pelagic components of the Lake Ontario food web. There was biomagnification of PCBs in the food web from benthic and planktonic invertebrates through to lake trout and gulls. However, all of the fish species had about the same lipid-normalized concentrations of PCBs. The relative proportions of the PCB congeners changed as they passed through the food web. An index of metabolism for each PCB congener was calculated by comparing the concentrations of PCB congeners in various predator/prey groupings within the food web. These data indicate that invertebrates, fish and gulls have different capabilities in metabolizing and eliminating specific PCB congeners. While tri and tetrachlorinated congeners with no chlorine substitution at meta-para carbons on the biphenyl ring were readily metabolized by all taxa, only gulls appeared to be capable of metabolizing the PCBs with no chlorine substitution at ortho-meta positions. The trophodynamics of nonortho substituted (coplanar) PCBs did not differ from other PCB congeners of similar chlorine number, which indicates that non-ortho congeners are not any more persistent in biota than other PCBs.

Metcalfe, T.L.; Metcalfe, C.D. [Trent Univ., Peterborough, Ontario (Canada). Environmental and Resource Studies Program

1995-12-31

118

Interaction strengths in food webs: issues and opportunities  

Microsoft Academic Search

Summary 1. Recent efforts to understand how the patterning of interaction strength affects both structure and dynamics in food webs have highlighted several obstacles to productive synthesis. Issues arise with respect to goals and driving questions, methods and approaches, and placing results in the context of broader ecological theory. 2. Much confusion stems from lack of clarity about whether the

Eric L. Berlow; Anje-Margiet Neutel; Joel E. Cohen; Peter C. de Ruiter; Bo Ebenman; Mark Emmerson; Jeremy W. Fox; Vincent A. A. Jansen; J. Iwan Jones; Giorgos D. Kokkoris; Dmitrii O. Logofet; Alan J. McKane; Jose M. Montoya; Owen Petchey

2004-01-01

119

Importance of river inputs to Arctic coastal food webs  

NASA Astrophysics Data System (ADS)

Nutrients transported from land to sea by rivers are essential to the health and productivity of coastal food webs, yet there are many places in the world where understanding of river inputs to the ocean remains limited. This is particularly true in the Arctic, where river water flow and chemistry data are scarce.

Wendel, JoAnna

2014-05-01

120

A method for identifying keystone species in food web models  

Microsoft Academic Search

Keystones are defined as relatively low biomass species with a structuring role in their food webs. Thus, identifying keystone species in a given ecosystem may be formulated as: (1) estimating the impact on the different elements of an ecosystem resulting from a small change to the biomass of the species to be evaluated for its ‘keystoneness’; and (2) deciding on

Simone Libralato; Villy Christensen; Daniel Pauly

2006-01-01

121

Barcoding a Quantified Food Web: Crypsis, Concepts, Ecology and Hypotheses  

Microsoft Academic Search

The efficient and effective monitoring of individuals and populations is critically dependent on correct species identification. While this point may seem obvious, identifying the majority of the more than 100 natural enemies involved in the spruce budworm (Choristoneura fumiferana – SBW) food web remains a non-trivial endeavor. Insect parasitoids play a major role in the processes governing the population dynamics

M. Alex Smith; Eldon S. Eveleigh; Kevin S. McCann; Mark T. Merilo; Peter C. McCarthy; Kathleen I. Van Rooyen

2011-01-01

122

MODEL OF CARBON CYCLING IN PLANKTONIC FOOD WEBS  

EPA Science Inventory

A mathematical model of carbon fluxes through the heterotrophic microbial food web is developed from a synthesis of laboratory and field research,The basis of the model is the segregation of organic carbon into lability classes that are defined by bioassay experiments. acteria, p...

123

MODEL OF CARBON CYCLING IN THE PLANKTONIC FOOD WEB  

EPA Science Inventory

A mathematical model of carbon fluxes through the heterotrophic microbial food web is developed from a synthesis of laboratory and field research. he basis of the model is the segregation of organic carbon into lability classes that are defined by bioassay experiments. acteria, p...

124

BENTHOS AS THE BASIS FOR ARCTIC FOOD WEBS  

EPA Science Inventory

Plankton have traditionally been viewed as the basis for limnetic food webs, with zooplankton acting as a gateway for energy passing between phytoplanktonic primary producers and fish. Often, benthic production is considered to be important primarily in shallow systems or as a su...

125

Learning from visualizing and Interacting with the Semantic Web Dog Food  

E-print Network

Learning from visualizing and Interacting with the Semantic Web Dog Food Christophe Gravier://portail.univ-st-etienne.fr Abstract. Semantic Web conferences such as WWW and ISWC fos- tered a collaborative effort to the Semantic Web Conference Corpus, a.k.a. the Semantic Web Dog Food Corpus. Many other conferences

Paris-Sud XI, Université de

126

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

Microsoft Academic Search

Summary 1. 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

Per-Arne Amundsen; Kevin D. Lafferty; Rune Knudsen; Raul Primicerio; Anders Klemetsen; Armand M. Kuris

2009-01-01

127

Computer simulations of sympatric speciation in a simple food web  

NASA Astrophysics Data System (ADS)

Galapagos finches, have motivated much theoretical research aimed at understanding the processes associated with the formation of the species. Inspired by them, in this paper we investigate the process of sympatric speciation in a simple food web model. For that we modify the individual-based Penna model that has been widely used to study aging as well as other evolutionary processes. Initially, our web consists of a primary food source and a single herbivore species that feeds on this resource. Subsequently we introduce a predator that feeds on the herbivore. In both instances we manipulate directly a basal resource distribution and monitor the changes in the populations. Sympatric speciation is obtained for the top species in both cases, and our results suggest that the speciation velocity depends on how far up, in the food chain, the focus population is feeding. Simulations are done with three different sexual imprintinglike mechanisms, in order to discuss adaptation by natural selection.

Luz-Burgoa, K.; Dell, Tony; de Oliveira, S. Moss

2005-07-01

128

Carbon steady-state model of the planktonic food web of Lake Biwa, Japan  

E-print Network

after degradation of detritus to release dissolved organic carbon. Keywords: detritus, food web, lakeCarbon steady-state model of the planktonic food web of Lake Biwa, Japan NATHALIE NIQUIL,* GRETTA planktonic food web in the surface mixed-layer of the North Basin in Lake Biwa, Japan. This model synthesised

Jackson, George

129

Humans in the urban food web: Emerging insights from Phoenix and  

E-print Network

of trophic dynamics in urban vs. desert settings (see Urban Food Web diagram, below). However, the natureHumans in the urban food web: Emerging insights from Phoenix and Baltimore P. S. Warren, E. Adley intense human activity, urbanization, alters food webs and trophic structure in biological communities

Hall, Sharon J.

130

Developing a broader scientific foundation for river restoration: Columbia River food webs  

E-print Network

Developing a broader scientific foundation for river restoration: Columbia River food webs Robert J 31, 2012 (received for review August 6, 2012) Well-functioning food webs are fundamental emphasis on restoring habitat structure--without explicitly considering food webs--has been less successful

131

Effects of Sampling Effort on Characterization of Food-Web Structure  

Microsoft Academic Search

A critical and poorly understood aspect of food-web theory concerns the possibility that variable observation effort, such as widely different sampling intensities among investigators, confounds structural food-web patterns. We evaluated this pos- sibility by simulating the effects of variable observation effort on the structure of a food web including 77 insect species found inside the stems of 10 species of

Neo D. Martinez; Bradford A. Hawkins; Hassan Ali Dawah; Brian P. Feifarek

1999-01-01

132

A Comparison of Soil Food Webs Beneath C3- and C4-Dominated Grasslands  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil food web structure influences soil organic matter mineralization and plant nutrient availability, but the potential for plants to capitalize on this mechanism by altering soil food web structure has received little attention. We evaluated this potential mechanism by measuring soil food web str...

133

Bacterial traits, organism mass, and numerical abundance in the detrital soil food web of Dutch  

E-print Network

, collembolans, detritus, food web, microbial quotient, mites, nematodes, qCO2, soil basal respiration. EcologyLETTER Bacterial traits, organism mass, and numerical abundance in the detrital soil food web in the detrital soil food webs of grasslands in the Netherlands, using the relationship between average body mass

Cohen, Joel E.

134

Extinction risk and structure of a food web model  

E-print Network

We investigate in detail the model of a trophic web proposed by Amaral and Meyer [Phys. Rev. Lett. 82, 652 (1999)]. We focused on small-size systems that are relevant for real biological food webs and for which the fluctuations are playing an important role. We show, using Monte Carlo simulations, that such webs can be non-viable, leading to extinction of all species in small and/or weakly coupled systems. Estimations of the extinction times and survival chances are also given. We show that before the extinction the fraction of highly-connected species ("omnivores") is increasing. Viable food webs exhibit a pyramidal structure, where the density of occupied niches is higher at lower trophic levels, and moreover the occupations of adjacent levels are closely correlated. We also demonstrate that the distribution of the lengths of food chains has an exponential character and changes weakly with the parameters of the model. On the contrary, the distribution of avalanche sizes of the extinct species depends strong...

PÈ©kalski, A; Bena, I; Droz, M

2007-01-01

135

Benchmarking Successional Progress in a Quantitative Food Web  

PubMed Central

Central to ecology and ecosystem management, succession theory aims to mechanistically explain and predict the assembly and development of ecological communities. Yet processes at lower hierarchical levels, e.g. at the species and functional group level, are rarely mechanistically linked to the under-investigated system-level processes which drive changes in ecosystem properties and functioning and are comparable across ecosystems. As a model system for secondary succession, seasonal plankton succession during the growing season is readily observable and largely driven autogenically. We used a long-term dataset from large, deep Lake Constance comprising biomasses, auto- and heterotrophic production, food quality, functional diversity, and mass-balanced food webs of the energy and nutrient flows between functional guilds of plankton and partly fish. Extracting population- and system-level indices from this dataset, we tested current hypotheses about the directionality of successional progress which are rooted in ecosystem theory, the metabolic theory of ecology, quantitative food web theory, thermodynamics, and information theory. Our results indicate that successional progress in Lake Constance is quantifiable, passing through predictable stages. Mean body mass, functional diversity, predator-prey weight ratios, trophic positions, system residence times of carbon and nutrients, and the complexity of the energy flow patterns increased during succession. In contrast, both the mass-specific metabolic activity and the system export decreased, while the succession rate exhibited a bimodal pattern. The weighted connectance introduced here represents a suitable index for assessing the evenness and interconnectedness of energy flows during succession. Diverging from earlier predictions, ascendency and eco-exergy did not increase during succession. Linking aspects of functional diversity to metabolic theory and food web complexity, we reconcile previously disjoint bodies of ecological theory to form a complete picture of successional progress within a pelagic food web. This comprehensive synthesis may be used as a benchmark for quantifying successional progress in other ecosystems. PMID:24587353

Boit, Alice; Gaedke, Ursula

2014-01-01

136

Benchmarking successional progress in a quantitative food web.  

PubMed

Central to ecology and ecosystem management, succession theory aims to mechanistically explain and predict the assembly and development of ecological communities. Yet processes at lower hierarchical levels, e.g. at the species and functional group level, are rarely mechanistically linked to the under-investigated system-level processes which drive changes in ecosystem properties and functioning and are comparable across ecosystems. As a model system for secondary succession, seasonal plankton succession during the growing season is readily observable and largely driven autogenically. We used a long-term dataset from large, deep Lake Constance comprising biomasses, auto- and heterotrophic production, food quality, functional diversity, and mass-balanced food webs of the energy and nutrient flows between functional guilds of plankton and partly fish. Extracting population- and system-level indices from this dataset, we tested current hypotheses about the directionality of successional progress which are rooted in ecosystem theory, the metabolic theory of ecology, quantitative food web theory, thermodynamics, and information theory. Our results indicate that successional progress in Lake Constance is quantifiable, passing through predictable stages. Mean body mass, functional diversity, predator-prey weight ratios, trophic positions, system residence times of carbon and nutrients, and the complexity of the energy flow patterns increased during succession. In contrast, both the mass-specific metabolic activity and the system export decreased, while the succession rate exhibited a bimodal pattern. The weighted connectance introduced here represents a suitable index for assessing the evenness and interconnectedness of energy flows during succession. Diverging from earlier predictions, ascendency and eco-exergy did not increase during succession. Linking aspects of functional diversity to metabolic theory and food web complexity, we reconcile previously disjoint bodies of ecological theory to form a complete picture of successional progress within a pelagic food web. This comprehensive synthesis may be used as a benchmark for quantifying successional progress in other ecosystems. PMID:24587353

Boit, Alice; Gaedke, Ursula

2014-01-01

137

Moving Up the Information Food Chain: Deploying Softbots on the World Wide Web  

Microsoft Academic Search

I view the World Wide Web as an information food chain (figure 1). The maze of pages and hyperlinks that comprise the Web are at the very bottom of the chain. The WebCrawlers and Alta Vistas of the world are information herbivores; they graze on Web pages and regurgitate them as searchable indices. Today, most Web users feed near the

Oren Etzioni

1996-01-01

138

Anthropogenic alterations of lotic food web structure: evidence from the use of nitrogen isotopes  

Microsoft Academic Search

Understanding the processes that regulate food chain length in nature is a classic theme in ecology. Two factors expected to explain variation in food chain length are resource availability (productivity) and environmental stress. We examined the impact of anthropogenic activities, both a source of stress and productivity, on lotic food webs using two simple food web descriptors based on stable

Caroline Anderson; Gilbert Cabana

2009-01-01

139

Molecular evidence for genetic subdivision of Antarctic krill (Euphausia superba Dana) populations.  

PubMed Central

Antarctic krill (Euphausia superba Dana) is a key species in the Antarctic food web and occurs on a circumcontinental scale. Population genetic structure of this species was investigated by sequence analysis of the ND1 mitochondrial gene in four population samples collected at different geographical localities around the Antarctic continent. Results indicate the existence of significant genetic differences between samples, and we suggest that oceanographic barriers could be sufficiently strong and temporally stable to restrict gene flow between distinct areas. Moreover, our data indicate that Antarctic krill is not at mutation-drift equilibrium and that the species possibly has a low effective population size as compared to the census size. PMID:9921678

Zane, L; Ostellari, L; Maccatrozzo, L; Bargelloni, L; Battaglia, B; Patarnello, T

1998-01-01

140

The more food webs change, the more they stay the same  

PubMed Central

Here, we synthesize a number of recent empirical and theoretical papers to argue that food-web dynamics are characterized by high amounts of spatial and temporal variability and that organisms respond predictably, via behaviour, to these changing conditions. Such behavioural responses on the landscape drive a highly adaptive food-web structure in space and time. Empirical evidence suggests that underlying attributes of food webs are potentially scale-invariant such that food webs are characterized by hump-shaped trophic structures with fast and slow pathways that repeat at different resolutions within the food web. We place these empirical patterns within the context of recent food-web theory to show that adaptable food-web structure confers stability to an assemblage of interacting organisms in a variable world. Finally, we show that recent food-web analyses agree with two of the major predictions of this theory. We argue that the next major frontier in food-web theory and applied food-web ecology must consider the influence of variability on food-web structure. PMID:19451128

McCann, Kevin Shear; Rooney, Neil

2009-01-01

141

Estimating chemical biotransformation rates from food web concentrations.  

PubMed

Biotransformation is widely recognized as the most important and most uncertain determinant of bioaccumulation. A step-wise method for estimating organism-specific biotransformation half-lives from field observations and using established food web modeling is developed. As a proof of concept, the method is applied to the case of nine polycyclic aromatic hydrocarbons (PAHs) in a well-studied food web in Bohai Bay, China. The estimated half-lives are in good agreement with the existing literature. The proposed biotransformation estimation method, through data mining, for sufficiently defined ecosystems, may greatly reduce the necessary animal testing involved in chemical assessments by providing useful guidance to experimentalists and regulators. PMID:22248809

Webster, Eva M; Ellis, David A

2012-04-01

142

Ingestion and transfer of microplastics in the planktonic food web.  

PubMed

Experiments were carried out with different Baltic Sea zooplankton taxa to scan their potential to ingest plastics. Mysid shrimps, copepods, cladocerans, rotifers, polychaete larvae and ciliates were exposed to 10 ?m fluorescent polystyrene microspheres. These experiments showed ingestion of microspheres in all taxa studied. The highest percentage of individuals with ingested spheres was found in pelagic polychaete larvae, Marenzelleria spp. Experiments with the copepod Eurytemora affinis and the mysid shrimp Neomysis integer showed egestion of microspheres within 12 h. Food web transfer experiments were done by offering zooplankton labelled with ingested microspheres to mysid shrimps. Microscopy observations of mysid intestine showed the presence of zooplankton prey and microspheres after 3 h incubation. This study shows for the first time the potential of plastic microparticle transfer via planktonic organisms from one trophic level (mesozooplankton) to a higher level (macrozooplankton). The impacts of plastic transfer and possible accumulation in the food web need further investigations. PMID:24220023

Setälä, Outi; Fleming-Lehtinen, Vivi; Lehtiniemi, Maiju

2014-02-01

143

Simulating Food Web Dynamics along a Gradient: Quantifying Human Influence  

PubMed Central

Realistically parameterized and dynamically simulated food-webs are useful tool to explore the importance of the functional diversity of ecosystems, and in particular relations between the dynamics of species and the whole community. We present a stochastic dynamical food web simulation for the Kelian River (Borneo). The food web was constructed for six different locations, arrayed along a gradient of increasing human perturbation (mostly resulting from gold mining activities) along the river. Along the river, the relative importance of grazers, filterers and shredders decreases with increasing disturbance downstream, while predators become more dominant in governing eco-dynamics. Human activity led to increased turbidity and sedimentation which adversely impacts primary productivity. Since the main difference between the study sites was not the composition of the food webs (structure is quite similar) but the strengths of interactions and the abundance of the trophic groups, a dynamical simulation approach seemed to be useful to better explain human influence. In the pristine river (study site 1), when comparing a structural version of our model with the dynamical model we found that structurally central groups such as omnivores and carnivores were not the most important ones dynamically. Instead, primary consumers such as invertebrate grazers and shredders generated a greater dynamical response. Based on the dynamically most important groups, bottom-up control is replaced by the predominant top-down control regime as distance downstream and human disturbance increased. An important finding, potentially explaining the poor structure to dynamics relationship, is that indirect effects are at least as important as direct ones during the simulations. We suggest that our approach and this simulation framework could serve systems-based conservation efforts. Quantitative indicators on the relative importance of trophic groups and the mechanistic modeling of eco-dynamics could greatly contribute to understanding various aspects of functional diversity. PMID:22768346

Jordán, Ferenc; Gjata, Nerta; Mei, Shu; Yule, Catherine M.

2012-01-01

144

Simulating food web dynamics along a gradient: quantifying human influence.  

PubMed

Realistically parameterized and dynamically simulated food-webs are useful tool to explore the importance of the functional diversity of ecosystems, and in particular relations between the dynamics of species and the whole community. We present a stochastic dynamical food web simulation for the Kelian River (Borneo). The food web was constructed for six different locations, arrayed along a gradient of increasing human perturbation (mostly resulting from gold mining activities) along the river. Along the river, the relative importance of grazers, filterers and shredders decreases with increasing disturbance downstream, while predators become more dominant in governing eco-dynamics. Human activity led to increased turbidity and sedimentation which adversely impacts primary productivity. Since the main difference between the study sites was not the composition of the food webs (structure is quite similar) but the strengths of interactions and the abundance of the trophic groups, a dynamical simulation approach seemed to be useful to better explain human influence. In the pristine river (study site 1), when comparing a structural version of our model with the dynamical model we found that structurally central groups such as omnivores and carnivores were not the most important ones dynamically. Instead, primary consumers such as invertebrate grazers and shredders generated a greater dynamical response. Based on the dynamically most important groups, bottom-up control is replaced by the predominant top-down control regime as distance downstream and human disturbance increased. An important finding, potentially explaining the poor structure to dynamics relationship, is that indirect effects are at least as important as direct ones during the simulations. We suggest that our approach and this simulation framework could serve systems-based conservation efforts. Quantitative indicators on the relative importance of trophic groups and the mechanistic modeling of eco-dynamics could greatly contribute to understanding various aspects of functional diversity. PMID:22768346

Jordán, Ferenc; Gjata, Nerta; Mei, Shu; Yule, Catherine M

2012-01-01

145

Mercury biomagnification in the food web of a neotropical stream.  

PubMed

Anthropogenic and natural mercury (Hg) contamination have been a major concern in South America since the early 1900s, but it remains unclear whether Hg levels pose a hazard to human health in regions that lack point sources. We studied Hg biomagnification patterns in the food web of Río Las Marías, an Andean piedmont stream in northern Venezuela, which supports a major subsistence fishery. Mercury concentrations and trophic positions in the food web (based on stable isotopes of nitrogen and carbon) were characterized for 24 fish species representing seven trophic guilds (piscivore, generalized carnivore, omnivore, invertivore, algivore, terrestrial herbivore, detritivore). Mercury showed significant biomagnification through the food web, but vertical trophic position explained little of the variation. Muscle Hg concentrations also increased with body mass across the food web. Trophic guild assignments offered a useful alternative to explicit analysis of vertical trophic position; piscivores showed the highest Hg concentrations and terrestrial herbivores had the lowest. There were no consistent seasonal differences in Hg concentrations within the 5 species sampled during both the wet and dry seasons, suggesting that bioavailability is unaffected by strong seasonal variation in rainfall. From a human health perspective, many medium- to large-bodied species that are commonly eaten had Hg concentrations that exceeded International Marketing Limit (IML) (0.5 ?g/g) and World Health Organization (WHO) guidelines (0.2 ?g/g) for consumption. We conclude that Hg concentrations may pose a health concern for local subsistence fishermen and their families. Our results suggest a need to perform risk assessment and better understand contaminant levels in subsistence and commercial fisheries even in areas that lack known Hg point sources. PMID:22257508

Kwon, Sae Yun; McIntyre, Peter B; Flecker, Alexander S; Campbell, Linda M

2012-02-15

146

Coevolutionary dynamics of adaptive radiation for food-web development  

Microsoft Academic Search

To investigate how complex food-webs can develop through repeated evolutionary diversification, a predator–prey model was\\u000a analyzed. In the model, each individual has two traits: trait x as a predator and trait y as a prey. These traits constitute a two-dimensional phenotype space, in which the whole group of individuals are represented\\u000a as a phenotype distribution. Predator–prey interactions among the phenotypes

Hiroshi C. Ito; Masakazu Shimada; Takashi Ikegami

2009-01-01

147

Midwater food web in the vicinity of a marginal ice zone in the western Weddell Sea  

NASA Astrophysics Data System (ADS)

The structure of the food web in the vicinity of a marginal ice zone was investigated in the western Weddell Sea during austral autumn 1986. The diets of 40 species of zooplankton and micronekton occurring in the epipelagic zone were examined and compared using non-hierarchical clustering procedures. Over half the species were in three clusters of predominantly small-particle (phytoplankton; protozoans) grazers. These included biomass dominants Calanoides acutus, Calanus propinquus, Metridia gerlachei and Salpa thompsoni. Six clusters contained omnivores that had diets consisting of small particles as well as a substantial fraction of metozoan food. Among these was Euphausia superba. Seven groups were carnivorous, including species of copepods (1), chaetognaths (3), and fishes (5). Copepods were the most frequent food of carnivores; however krill also were important in the diets of three fish species. Among small-particle grazers, phytoplankton occurred more frequently in guts of individuals from open water; carnivory was more in evidence in samples collected under the pack ice. Regional comparisons of material taken on this and several previous cruises indicate that, in most of the dominant species, diets remain relatively consistent with respect to major food categories. Seasonal impact on feeding dynamics appears to be great: the guts of grazing species were generally much more full (visual evidence) during summer bloom conditions than during the autumn. The following trophic sequence is suggested for grazing zooplankton species in ice-covered regions of the Antarctic: (1) Active small-particle grazing during the summer bloom period; (2) reduced ingestion rates in autumn as primary production declines and the system becomes more oligotrophic, with some species augmenting grazing with carnivory; (3) descent of zooplankton biomass species into the mesopelagic zone in late autumn-early winter with feeding largely terminated. The sequence applies to the dominant zooplankton biomass species. Feeding dynamics and vertical distribution of several of the important larger sized grazing species, such as Euphausia superba and Salpa thompsoni, remain largely unknown

Hopkins, Thomas L.; Torres, Joseph J.

1989-04-01

148

Rescaling the trophic structure of marine food webs  

PubMed Central

Measures of trophic position (TP) are critical for understanding food web interactions and human-mediated ecosystem disturbance. Nitrogen stable isotopes (?15N) provide a powerful tool to estimate TP but are limited by a pragmatic assumption that isotope discrimination is constant (change in ?15N between predator and prey, ?15N = 3.4‰), resulting in an additive framework that omits known ?15N variation. Through meta-analysis, we determine narrowing discrimination from an empirical linear relationship between experimental ?15N and ?15N values of prey consumed. The resulting scaled ?15N framework estimated reliable TPs of zooplanktivores to tertiary piscivores congruent with known feeding relationships that radically alters the conventional structure of marine food webs. Apex predator TP estimates were markedly higher than currently assumed by whole-ecosystem models, indicating perceived food webs have been truncated and species-interactions over simplified. The scaled ?15N framework will greatly improve the accuracy of trophic estimates widely used in ecosystem-based management. PMID:24308860

Hussey, Nigel E; MacNeil, M Aaron; McMeans, Bailey C; Olin, Jill A; Dudley, Sheldon FJ; Cliff, Geremy; Wintner, Sabine P; Fennessy, Sean T; Fisk, Aaron T

2014-01-01

149

Two degrees of separation in complex food webs  

NASA Astrophysics Data System (ADS)

Feeding relationships can cause invasions, extirpations, and population fluctuations of a species to dramatically affect other species within a variety of natural habitats. Empirical evidence suggests that such strong effects rarely propagate through food webs more than three links away from the initial perturbation. However, the size of these spheres of potential influence within complex communities is generally unknown. Here, we show for that species within large communities from a variety of aquatic and terrestrial ecosystems are on average two links apart, with >95% of species typically within three links of each other. Species are drawn even closer as network complexity and, more unexpectedly, species richness increase. Our findings are based on seven of the largest and most complex food webs available as well as a food-web model that extends the generality of the empirical results. These results indicate that the dynamics of species within ecosystems may be more highly interconnected and that biodiversity loss and species invasions may affect more species than previously thought.

Williams, Richard J.; Berlow, Eric L.; Dunne, Jennifer A.; Barabási, Albert-László; Martinez, Neo D.

2002-10-01

150

Tracking the autochthonous carbon transfer in stream biofilm food webs.  

PubMed

Food webs in the rhithral zone rely mainly on allochthonous carbon from the riparian vegetation. However, autochthonous carbon might be more important in open canopy streams. In streams, most of the microbial activity occurs in biofilms, associated with the streambed. We followed the autochthonous carbon transfer toward bacteria and grazing protozoa within a stream biofilm food web. Biofilms that developed in a second-order stream (Thuringia, Germany) were incubated in flow channels under climate-controlled conditions. Six-week-old biofilms received either ¹³C- or ¹²C-labeled CO?, and uptake into phospholipid fatty acids was followed. The dissolved inorganic carbon of the flow channel water became immediately labeled. In biofilms grown under 8-h light/16-h dark conditions, more than 50% of the labeled carbon was incorporated in biofilm algae, mainly filamentous cyanobacteria, pennate diatoms, and nonfilamentous green algae. A mean of 29% of the labeled carbon reached protozoan grazer. The testate amoeba Pseudodifflugia horrida was highly abundant in biofilms and seemed to be the most important grazer on biofilm bacteria and algae. Hence, stream biofilms dominated by cyanobacteria and algae seem to play an important role in the uptake of CO? and transfer of autochthonous carbon through the microbial food web. PMID:22067054

Risse-Buhl, Ute; Trefzger, Nicolai; Seifert, Anne-Gret; Schönborn, Wilfried; Gleixner, Gerd; Küsel, Kirsten

2012-01-01

151

AKTive Food: Semantic Web based knowledge conduits for the Organic Food Industry  

Microsoft Academic Search

We present a vision and a proposal for using Semantic Web technologies in the organic food industry. This is a very knowledge inten- sive industry at every step from the producer, to the caterer or restau- ranteur, through to the consumer. There is a crucial need for a concept of environmental audit which would allow the various stake holders to

Christopher Brewster; Hugh Glaser; Barny Haughton

152

Complementary molecular information changes our perception of food web structure  

PubMed Central

How networks of ecological interactions are structured has a major impact on their functioning. However, accurately resolving both the nodes of the webs and the links between them is fraught with difficulties. We ask whether the new resolution conferred by molecular information changes perceptions of network structure. To probe a network of antagonistic interactions in the High Arctic, we use two complementary sources of molecular data: parasitoid DNA sequenced from the tissues of their hosts and host DNA sequenced from the gut of adult parasitoids. The information added by molecular analysis radically changes the properties of interaction structure. Overall, three times as many interaction types were revealed by combining molecular information from parasitoids and hosts with rearing data, versus rearing data alone. At the species level, our results alter the perceived host specificity of parasitoids, the parasitoid load of host species, and the web-wide role of predators with a cryptic lifestyle. As the northernmost network of host–parasitoid interactions quantified, our data point exerts high leverage on global comparisons of food web structure. However, how we view its structure will depend on what information we use: compared with variation among networks quantified at other sites, the properties of our web vary as much or much more depending on the techniques used to reconstruct it. We thus urge ecologists to combine multiple pieces of evidence in assessing the structure of interaction webs, and suggest that current perceptions of interaction structure may be strongly affected by the methods used to construct them. PMID:24449902

Wirta, Helena K.; Hebert, Paul D. N.; Kaartinen, Riikka; Prosser, Sean W.; Várkonyi, Gergely; Roslin, Tomas

2014-01-01

153

Food-Web Structure of Seagrass Communities across Different Spatial Scales and Human Impacts  

PubMed Central

Seagrass beds provide important habitat for a wide range of marine species but are threatened by multiple human impacts in coastal waters. Although seagrass communities have been well-studied in the field, a quantification of their food-web structure and functioning, and how these change across space and human impacts has been lacking. Motivated by extensive field surveys and literature information, we analyzed the structural features of food webs associated with Zostera marina across 16 study sites in 3 provinces in Atlantic Canada. Our goals were to (i) quantify differences in food-web structure across local and regional scales and human impacts, (ii) assess the robustness of seagrass webs to simulated species loss, and (iii) compare food-web structure in temperate Atlantic seagrass beds with those of other aquatic ecosystems. We constructed individual food webs for each study site and cumulative webs for each province and the entire region based on presence/absence of species, and calculated 16 structural properties for each web. Our results indicate that food-web structure was similar among low impact sites across regions. With increasing human impacts associated with eutrophication, however, food-web structure show evidence of degradation as indicated by fewer trophic groups, lower maximum trophic level of the highest top predator, fewer trophic links connecting top to basal species, higher fractions of herbivores and intermediate consumers, and higher number of prey per species. These structural changes translate into functional changes with impacted sites being less robust to simulated species loss. Temperate Atlantic seagrass webs are similar to a tropical seagrass web, yet differed from other aquatic webs, suggesting consistent food-web characteristics across seagrass ecosystems in different regions. Our study illustrates that food-web structure and functioning of seagrass habitats change with human impacts and that the spatial scale of food-web analysis is critical for determining results. PMID:21811637

Coll, Marta; Schmidt, Allison; Romanuk, Tamara; Lotze, Heike K.

2011-01-01

154

Internet Food Marketing Strategies Aimed at Children and Adolescents: A Content Analysis of Food and Beverage Brand Web Sites  

Microsoft Academic Search

Americans are spending an increasing amount of time using “new media” like the Internet. There has been little research examining food and beverage Web sites’ content and marketing practices, especially those that attract children and adolescents. The purpose of this study was to conduct a content analysis of food- and beverage-brand Web sites and the marketing techniques and advertising strategies

Kristi Weber; Mary Story; Lisa Harnack

2006-01-01

155

Ecological Stoichiometry, Biogeochemical Cycling, Invasive Species, and Aquatic Food Webs: San Francisco Estuary and Comparative Systems  

Microsoft Academic Search

Eutrophication has altered food webs across aquatic systems, but effects of nutrient stoichiometry (varying nutrient ratios) on ecosystem structure and function have received less attention. A prevailing assumption has been that nutrients are not ecologically relevant unless concentrations are limiting to phytoplankton. However, changes in nutrient stoichiometry fundamentally affect food quality at all levels of the food web. Here, 30-year

Patricia M. Glibert; David Fullerton; Joann M. Burkholder; Jeffrey C. Cornwell; Todd M. Kana

2011-01-01

156

This paper was published in Soft Matter as part of the Food Science web theme issue  

E-print Network

in food processing plants.1­4 In particular, the adsorption of proteins at liquid­solid interfaces materials and food industries.5,6 For example, adsorption of proteins onto food processing equipmentFood This paper was published in Soft Matter as part of the Food Science web theme issue This Soft

Dutcher, John

157

Bioaccumulation of toxaphene congeners in the lake superior food web  

USGS Publications Warehouse

The bioaccumulation and biotransformation of toxaphene was examined in the food webs of Lake Superior and Siskiwit Lake (Isle Royale) using congener specific analysis as well as stable isotope ratios of carbon and nitrogen to characterize food webs. Toxaphene concentrations (calculated using technical toxaphene) in lake trout (Salvelinus namaycush) from the western basin of Lake Superior (N = 95) averaged (±SD) 889 ± 896 ng/g wet wt and 60 ± 34 ng/g wet wt in Siskiwit Lake. Major congeners in lake trout were B8-789 (P38), B8-2226 (P44), B9-1679 (P50), and B9-1025 (P62). Toxaphene concentrations were found to vary seasonally, especially in lower food web organisms in Lake Superior and to a lesser extent in Siskiwit Lake. Toxaphene concentrations declined significantly in lake herring (Coregonus artedii), rainbow smelt (Omerus mordax), and slimy sculpin (Cottus cognatus) as well as in zooplankton (> 102 &mn;m) and Mysis (Mysis relicta) between May and October. The seasonal variation may reflect seasonal shifts in the species abundance within the zooplankton community. Trophic magnification factors (TMF) derived from regressions of toxaphene congener concentrations versus ?15N were > 1 for most octa- and nonachlorobornanes in Lake Superior except B8-1413 (P26) and B9-715. Log bioaccumulation factors (BAFs) for toxaphene congeners in lake trout (ng/g lipid/ng/L dissolved) ranged from 4.54 to 9.7 and were significantly correlated with log octanol-water partition coefficients. TMFs observed for total toxaphene and congener B9-1679 in Lake Superior were similar to those in Arctic lakes, as well as to previous studies in the Great Lakes, which suggests that the bioaccumulation behavior of toxaphene is similar in pelagic food webs of large, cold water systems. However, toxaphene concentrations were lower in lake trout from Siskiwit Lake and lakes in northwestern Ontario than in Lake Superior possibly because of shorter food chains and greater reliance on zooplankton or other pelagic invertebrates.

Muir, D.C.G.; Whittle, D.M.; De Vault, D. S.; Bronte, C.R.; Karlsson, H.; Backus, S.; Teixeira, C.

2004-01-01

158

Land use alters the resistance and resilience of soil food webs to drought  

NASA Astrophysics Data System (ADS)

Soils deliver several ecosystem services including carbon sequestration and nutrient cycling, which are of central importance to climate mitigation and sustainable food production. Soil biota play an important role in carbon and nitrogen cycling, and, although the effects of land use on soil food webs are well documented, the consequences for their resistance and resilience to climate change are not known. We compared the resistance and resilience to drought--which is predicted to increase under climate change--of soil food webs of two common land-use systems: intensively managed wheat with a bacterial-based soil food web and extensively managed grassland with a fungal-based soil food web. We found that the fungal-based food web, and the processes of C and N loss it governs, of grassland soil was more resistant, although not resilient, and better able to adapt to drought than the bacterial-based food web of wheat soil. Structural equation modelling revealed that fungal-based soil food webs and greater microbial evenness mitigated C and N loss. Our findings show that land use strongly affects the resistance and resilience of soil food webs to climate change, and that extensively managed grassland promotes more resistant, and adaptable, fungal-based soil food webs.

de Vries, Franciska T.; Liiri, Mira E.; Bjørnlund, Lisa; Bowker, Matthew A.; Christensen, Søren; Setälä, Heikki M.; Bardgett, Richard D.

2012-04-01

159

Land use alters the resistance and resilience of soil food webs to drought  

USGS Publications Warehouse

Soils deliver several ecosystem services including carbon sequestration and nutrient cycling, which are of central importance to climate mitigation and sustainable food production. Soil biota play an important role in carbon and nitrogen cycling, and, although the effects of land use on soil food webs are well documented the consequences for their resistance and resilience to climate change are not known. We compared the resistance and resilience to drought--which is predicted to increase under climate change of soil food webs of two common land-use systems: intensively managed wheat with a bacterial-based soil food web and extensively managed grassland with a fungal-based soil food web. We found that the fungal-based food web, and the processes of C and N loss it governs, of grassland soil was more resistant, although not resilient, and better able to adapt to drought than the bacterial-based food web of wheat soil. Structural equation modelling revealed that fungal-based soil food webs and greater microbial evenness mitigated C and N loss. Our findings show that land use strongly affects the resistance and resilience of soil food webs to climate change, and that extensively managed grassland promotes more resistant, and adaptable, fungal-based soil food webs.

de Vries, Franciska T.; Liiri, Mira E.; Bjørnlund, Lisa; Bowker, Matthew A.; Christensen, Søren; Setälä, Heikki; Bardgett, Richard D.

2012-01-01

160

Native and nonnative fish populations of the Colorado River are food limited--evidence from new food web analyses  

USGS Publications Warehouse

Fish populations in the Colorado River downstream from Glen Canyon Dam appear to be limited by the availability of high-quality invertebrate prey. Midge and blackfly production is low and nonnative rainbow trout in Glen Canyon and native fishes in Grand Canyon consume virtually all of the midge and blackfly biomass that is produced annually. In Glen Canyon, the invertebrate assemblage is dominated by nonnative New Zealand mudsnails, the food web has a simple structure, and transfers of energy from the base of the web (algae) to the top of the web (rainbow trout) are inefficient. The food webs in Grand Canyon are more complex relative to Glen Canyon, because, on average, each species in the web is involved in more interactions and feeding connections. Based on theory and on studies from other ecosystems, the structure and organization of Grand Canyon food webs should make them more stable and less susceptible to large changes following perturbations of the flow regime relative to food webs in Glen Canyon. In support of this hypothesis, Grand Canyon food webs were much less affected by a 2008 controlled flood relative to the food web in Glen Canyon.

Kennedy, Theodore A.; Cross, Wyatt F.; Hall, Robert O., Jr.; Baxter, Colden V.; Rosi-Marshall, Emma J.

2013-01-01

161

Reducing Methylmercury Accumulation in the Food Webs of San Francisco Bay and Its Local Watershed  

E-print Network

­ Food web shifts Knobs #12;Reservoir · Elective strategies ­ Slow knobs · THg inputs ­ Fast knobs#12;#12;Reducing Methylmercury Accumulation in the Food Webs of San Francisco Bay and Its Local food web Hg Gehrke et al. 2011. ES&T 45 (4), pp 1264­1270 #12;0 0.1 0.2 0.3 0.4 0.5 Louisiana

162

Quantitative approaches to the analysis of stable isotope food web data.  

PubMed

Ecologists use stable isotopes (delta13C, delta15N) to better understand food webs and explore trophic interactions in ecosystems. Traditionally, delta13C vs. delta15N bi-plots have been used to describe food web structure for a single time period or ecosystem. Comparisons of food webs across time and space are increasing, but development of statistical approaches for testing hypotheses regarding food web change has lagged behind. Here we present statistical methodologies for quantitatively comparing stable isotope food web data. We demonstrate the utility of circular statistics and hypothesis tests for quantifying directional food web differences using two case studies: an arthropod salt marsh community across a habitat gradient and a freshwater fish community from Lake Tahoe, USA, over a 120-year time period. We calculated magnitude and mean angle of change (theta) for each species in food web space using mean delta13C and delta15N of each species as the x, y coordinates. In the coastal salt marsh, arthropod consumers exhibited a significant shift toward dependence on Spartina, progressing from a habitat invaded by Phragmites to a restored Spartina habitat. In Lake Tahoe, we found that all species from the freshwater fish community shifted in the same direction in food web space toward more pelagic-based production with the introduction of nonnative Mysis relicta and onset of cultural eutrophication. Using circular statistics to quantitatively analyze stable isotope food web data, we were able to gain significant insight into patterns and changes in food web structure that were not evident from qualitative comparisons. As more ecologists incorporate a food web perspective into ecosystem analysis, these statistical tools can provide a basis for quantifying directional food web differences from standard isotope data. PMID:18051648

Schmidt, Stephanie N; Olden, Julian D; Solomon, Christopher T; Vander Zanden, M Jake

2007-11-01

163

Biochemical tracers reveal intra-specific differences in the food webs utilized by individual seabirds  

Microsoft Academic Search

Food web structure regulates the pathways and flow rates of energy, nutrients, and contaminants to top predators. Ecologically\\u000a and physiologically meaningful biochemical tracers provide a means to characterize and quantify these transfers within food\\u000a webs. In this study, changes in the ratios of stable N isotopes (e.g., ?15N), fatty acids (FA), and persistent contaminants were used to trace food web

Craig E. Hebert; D. V. Chip Weseloh; Lewis T. Gauthier; Michael T. Arts; Robert J. Letcher

2009-01-01

164

Perfluoroalkyl contaminants in a food web from Lake Ontario.  

PubMed

Perfluorooctane sulfonate (PFOS) is a persistent and bioaccumulative perfluorinated acid detectable in humans and wildlife worldwide that has alerted scientists to examine the environmental fate of other fluorinated organic contaminants. Recently a homologous series of perfluoroalkyl carboxylates (PFCAs) was detected in the Arctic, yet little is known about their sources, breadth of contamination, or environmental distribution. In this study we analyzed for PFOS, the homologous series of PFCAs ranging from 8 to 15 carbons in chain length, and the PFOS-precursor heptadecafluorooctane sulfonamide (FOSA) in various organisms from a food web of Lake Ontario. The sampled organisms included a top predator fish, lake trout (Salvelinus namaycush), three forage fish species including rainbow smelt (Osmerus mordax), slimy sculpin (Cottus cognatus), and alewife (Alosa pseudoharengus), and two invertebrates Diporeia (Diporeia hoyi) and Mysis (Mysis relicta). A striking finding was that the highest mean concentration for each fluorinated contaminantwas detected in the benthic macroinvertebrate Diporeia, which occupies the lowest trophic level of all organisms analyzed. Perfluorinated acid concentrations in Diporeia were often 10-fold higher than in Mysis, a predominantly pelagic feeder, suggesting that a major source of perfluoroalkyl contaminants to this food web was the sediment, not the water. PFOS was the dominant acid in all samples, but long-chain PFCAs, ranging in length from 8 to 15 carbons, were also detected in most samples between <0.5 and 90 ng/ g. Among Mysis and the more pelagic fish species (e.g. excluding Diporeia and sculpin) there was evidence for biomagnification, but the influence of foraging on highly contaminated Diporeia and sculpin by these fish may have overestimated trophic magnification factors (TMFs), which ranged from 0.51 for FOSA to 5.88 for PFOS. By accounting for the known diet composition of lake trout, it was shown that bioaccumulation was indeed occurring at the top of the food web for all perfluoroalkyl compounds except PFOA. Future monitoring at other locations in Lake Ontario, and in other aquatic environments, is necessary to determine if these food web dynamics are widespread. Archived lake trout samples collected between 1980 and 2001 showed that mean whole body PFOS concentrations increased from 43 to 180 ng/g over this period, but not linearly, and may have been indirectly influenced by the invasion and proliferation of zebra mussels (Dreissena polymorpha) through effects on the population and ecology of forage fishes. PMID:15543740

Martin, Jonathan W; Whittle, D Michael; Muir, Derek C G; Mabury, Scott A

2004-10-15

165

Australian Antarctic Data Centre  

NSDL National Science Digital Library

The Australian Antarctic Division is part of the Australian Government's Department of the Environment and Heritage. Within the department's Web site is the Australian Antarctic Data Centre, which makes all scientific observations and results freely available. Data topics include weather, GIS and mapping, marine science, flora and fauna, and many other topics related to the southern continent.

2002-01-01

166

Moving up the information food chain: Deploying softbots on the World Wide Web  

SciTech Connect

I view the World Wide Web as an information food chain. The maze of pages and hyperlinks that comprise the Web are at the very bottom of the chain. The WebCrawlers and Alta Vistas of the world are information herbivores; they graze on Web pages and regurgitate them as searchable indices. Today, most Web users feed near the bottom of the information food chain, but the time is ripe to move up. Since 1991, we have been building information carnivores, which intelligently hunt and feast on herbivores in Unix, on the Internet, and on the Web.

Etzioni, O. [Univ. of Washington, Seattle, WA (United States)

1996-12-31

167

Food and Beverage Brands that Market to Children and Adolescents on the Internet: A Content Analysis of Branded Web Sites  

ERIC Educational Resources Information Center

Objective: To identify food and beverage brand Web sites featuring designated children's areas, assess marketing techniques present on those industry Web sites, and determine nutritional quality of branded food items marketed to children. Design: Systematic content analysis of food and beverage brand Web sites and nutrient analysis of food and…

Henry, Anna E.; Story, Mary

2009-01-01

168

Biomagnification of polychlorinated biphenyls through a riverine food web  

SciTech Connect

From 1989 to 1993, biota collected from Pottersburg Creek, London, ON, Canada were analyzed for total polychlorinated biphenyls (PCBs) and lipids. Data were analyzed by analysis of covariance (ANCOVA) with lipid as the covariate, to investigate station, time, and trophic effects on PCB accumulation in aquatic organisms. All three variables were highly significant. PCB concentrations in biota decreased along the length of the creek away from the point source. PCB concentrations in biota collected in July 1993 were not significantly different from concentrations in biota collected in July 1990, suggesting that sources into the creek have not been alleviated. The relationship between PCBs and lipid for biota from Pottersburg Creek suggests that organisms accumulate PCBs relative to their position in the food web. Fish and leeches occupying the top of the food web accumulated more PCBs than organisms occupying a lower trophic position (crayfish and oligochaetes/chironomids), indicating that biomagnification through trophic transfer (i.e., the uptake of a chemical through ingestion) is the primary mechanism governing contaminant levels in biota and not bioconcentration (i.e, the uptake of a chemical from water).

Zaranko, D.T.; Kaushik, N.K. [Univ. of Guelph, Ontario (Canada). Dept. of Environmental Biology; Griffiths, R.W. [Ministry of Environment and Energy, London, Ontario (Canada)

1997-07-01

169

The ecological potentials of Phytomyxea (“plasmodiophorids”) in aquatic food webs  

PubMed Central

The Phytomyxea (“plasmodiophorids”) including both Plasmodiophorida and Phagomyxida is a monophyletic group of Eukaryotes composed of obligate biotrophic parasites of green plants, brown algae, diatoms and stramenopiles commonly found in many freshwater, soil and marine environments. However, most research on Phytomyxea has been restricted to plant pathogenic species with agricultural importance, thereby missing the huge ecological potential of this enigmatic group of parasites. Members of the Phytomyxea can induce changes in biomass in their hosts (e.g. hypertrophies of the host tissue) under suitable environmental conditions. Upon infection they alter the metabolism of their hosts, consequently changing the metabolic status of their host. This results in an altered chemical composition of the host tissue, which impacts the diversity of species which feed on the tissues of the infected host and on the zoospores produced by the parasites. Furthermore, significant amounts of nutrients derived from the hosts, both primary producers (plants and algae) and primary consumers (litter decomposers and plant parasites [Oomycetes]), can enter the food web at different trophic levels in form of zoospores and resting spores. Large numbers of zoospores and resting spores are produced which can be eaten by secondary and tertiary consumers, such as grazing zooplankton and metazoan filter-feeders. Therefore, these microbes can act as energy-rich nutrient resources which may significantly alter the trophic relationships in fresh water, soil and marine habitats. Based on the presented data, Phytomyxea can significantly contribute to the complexity and energy transfer within food webs. PMID:21339888

2011-01-01

170

Model of carbon cycling in planktonic food webs  

SciTech Connect

A mathematical model of carbon fluxes through the heterotrophic microbial food web is developed from a synthesis of laboratory and field research. The basis of the model is the segregation of organic carbon into lability classes that are defined by bioassay experiments. Bacteria, phytoplankton, three trophic levels of zooplankton, and dissolved organic carbon (DOC) and particulate organic carbon (POC) are modeled. The descriptions of bacterial growth and utilization of the various classes of substrate were treated as universal constants in the application of the model to three distinct ecosystems, ranging from oligotrophic to highly eutrophic. The successful application of the model to these diverse ecosystems supports the basic validity of the description of the microbial food web and the dynamics of carbon flux. The model indicates that the dynamics of bacteria and protozoan zooplankton production govern the rates of oxidation of carbon entering the water column. Explicit consideration of these groups would improve the capability of eutrophication models to predict dissolved oxygen dynamics, particularly when projecting responses to loading changes.

Connolly, J.P. [HydroQual, Inc., Mahwah, NJ (United States); Coffin, R.B. [Environmental Protection Agency, Gulf Breeze, FL (United States). Environmental Research Lab.

1995-10-01

171

Application of information theory methods to food web reconstruction  

USGS Publications Warehouse

In this paper we use information theory techniques on time series of abundances to determine the topology of a food web. At the outset, the food web participants (two consumers, two resources) are known; in addition we know that each consumer prefers one of the resources over the other. However, we do not know which consumer prefers which resource, and if this preference is absolute (i.e., whether or not the consumer will consume the non-preferred resource). Although the consumers and resources are identified at the beginning of the experiment, we also provide evidence that the consumers are not resources for each other, and the resources do not consume each other. We do show that there is significant mutual information between resources; the model is seasonally forced and some shared information between resources is expected. Similarly, because the model is seasonally forced, we expect shared information between consumers as they respond to the forcing of the resources. The model that we consider does include noise, and in an effort to demonstrate that these methods may be of some use in other than model data, we show the efficacy of our methods with decreasing time series size; in this particular case we obtain reasonably clear results with a time series length of 400 points. This approaches ecological time series lengths from real systems.

Moniz, L.J.; Cooch, E.G.; Ellner, S.P.; Nichols, J.D.; Nichols, J.M.

2007-01-01

172

Dynamics of the Lake Michigan food web, 1970-2000  

USGS Publications Warehouse

Herein, we document changes in the Lake Michigan food web between 1970 and 2000 and identify the factors responsible for these changes. Control of sea lamprey (Petromyzon marinus) and alewife (Alosa pseudoharengus) populations in Lake Michigan, beginning in the 1950s and 1960s, had profound effects on the food web. Recoveries of lake whitefish (Coregonus clupeaformis) and burbot (Lota lota) populations, as well as the buildup of salmonine populations, were attributable, at least in part, to sea lamprey control. Based on our analyses, predation by salmonines was primarily responsible for the reduction in alewife abundance during the 1970s and early 1980s. In turn, the decrease in alewife abundance likely contributed to recoveries of deepwater sculpin (Myoxocephalus thompsoni), yellow perch (Perca flavescens), and burbot populations during the 1970s and 1980s. Decrease in the abundance of all three dominant benthic macroinvertebrate groups, including Diporeia, oligochaetes, and sphaeriids, during the 1980s in nearshore waters (50 m deep) of Lake Michigan, was attributable to a decrease in primary production linked to a decline in phosphorus loadings. Continued decrease in Diporeia abundance during the 1990s was associated with the zebra mussel (Dreissena polymorpha) invasion, but specific mechanisms for zebra mussels affecting Diporeia abundance remain unidentified.

Madenjian, Charles P.; Fahnenstiel, Gary L.; Johengen, Thomas H.; Nalepa, Thomas F.; Vanderploeg, Henry A.; Fleischer, Guy W.; Schneeberger, Philip J.; Benjamin, Darren M.; Smith, Emily B.; Bence, James R.; Rutherford, Edward S.; Lavis, Dennis S.; Robertson, Dale M.; Jude, David J.; Ebener, Mark P.

2002-01-01

173

Non-Deterministic Modelling of Food-Web Dynamics  

PubMed Central

A novel approach to model food-web dynamics, based on a combination of chance (randomness) and necessity (system constraints), was presented by Mullon et al. in 2009. Based on simulations for the Benguela ecosystem, they concluded that observed patterns of ecosystem variability may simply result from basic structural constraints within which the ecosystem functions. To date, and despite the importance of these conclusions, this work has received little attention. The objective of the present paper is to replicate this original model and evaluate the conclusions that were derived from its simulations. For this purpose, we revisit the equations and input parameters that form the structure of the original model and implement a comparable simulation model. We restate the model principles and provide a detailed account of the model structure, equations, and parameters. Our model can reproduce several ecosystem dynamic patterns: pseudo-cycles, variation and volatility, diet, stock-recruitment relationships, and correlations between species biomass series. The original conclusions are supported to a large extent by the current replication of the model. Model parameterisation and computational aspects remain difficult and these need to be investigated further. Hopefully, the present contribution will make this approach available to a larger research community and will promote the use of non-deterministic-network-dynamics models as ‘null models of food-webs’ as originally advocated. PMID:25299245

Planque, Benjamin; Lindstrøm, Ulf; Subbey, Sam

2014-01-01

174

Food web structure and the evolution of ecological communities  

NASA Astrophysics Data System (ADS)

Simulations of the coevolution of many interacting species are performed using the Webworld model. The model has a realistic set of predator-prey equations that describe the population dynamics of the species for any structure of the food web. The equations account for competition between species for the same resources, and for the diet choice of predators between alternative prey according to an evolutionarily stable strategy. The set of species present undergoes long-term evolution d ue to speciation and extinction events. We summarize results obtained on the macro-evolutionary dynamics of speciations and extinctions, and on the statistical properties of the food webs that are generated by the model. Simulations begin from small numbers of species and build up to larger webs with relatively constant species number on average. The rate of origination and extinction of species are relatively high, but remain roughly balanced throughout the simulations. When a 'parent' species undergoes sp eciation, the 'child' species usually adds to the same trophic level as the parent. The chance of the child species surviving is significantly higher if the parent is on the second or third trophic level than if it is on the first level, most likely due to a wider choice of possible prey for species on higher levels. Addition of a new species sometimes causes extinction of existing species. The parent species has a high probability of extinction because it has strong competition with the new species. Non-pa rental competitors of the new species also have a significantly higher extinction probability than average, as do prey of the new species. Predators of the new species are less likely than average to become extinct.

Quince, Christopher; Higgs, Paul G.; McKane, Alan J.

175

Distribution, growth and reproduction of the limpet Nacella ( Patinigera ) concinna (Strebel 1908) in relation to potential food availability, in Esperanza Bay (Antarctic Peninsula)  

Microsoft Academic Search

The present work addresses the effect of environmental factors (icing, water temperature, food availability) on the ecology of the patellid limpet Nacella (Patinigera) concinna, in a bay on the Antarctic Peninsula. Sampling was conducted at three depths (intertidal, 5m, 10m) from February 1987 to January 1988. Temperature was recorded and concentrations of Chlorophyll a were measured on the bottom, in

J.-C. Brêthes; G. Ferreyra; S. Vega

1994-01-01

176

No tree an island: the plantcaterpillar food web of a secondary rain forest in New Guinea  

E-print Network

REPORT No tree an island: the plant­caterpillar food web of a secondary rain forest in New Guinea *Correspondence: E-mail: novotny@entu.cas.cz Abstract We characterized a plant­caterpillar food web from secondary individual caterpillars while some links were extremely rare. A caterpillar randomly picked from

Basset, Yves

177

Stable isotope analyses of the pelagic food web in Lake Baikal  

Microsoft Academic Search

Stable isotope ratios of various organisms were analyzed to elucidate food web structure in the pelagic zone of Lake Baikal. The pelagic food web of Lake Baikal is simple and consists of five major ecological groups: phyto- plankton (Aulacoseira baicalensis), mesozooplankton (Epischura baicalensis), macrozooplankton amphipod (Ma- crohectopus branickii), fish (Coregonus autumnalis migratoriusand four species of cottoid fishes), and seal (Phoca

Koichi Yoshii; Natalia G. Melnik; Oleg A. Timoshkin; Nina A. Bondarenko; Pavel N. Anoshko; Takahito Yoshioka; Eitaro Wada

1999-01-01

178

Reducing Methylmercury Accumulation in the Food Webs of San Francisco Bay and Its Local Watershed  

E-print Network

level rise ­ Food web shifts Open Bay: Possible Knobs #12;Suspended Sediment (mg/L) 0.00 0.02 0.04 0 legacy Hg matters · Isotopes · Spatial patterns · Even Hg in cinnabar and related forms makes of restored marshes · Non-elective changes ­ Temperature change ­ Food web shifts Risk Indicators Knobs #12

179

IMPORTANCE OF TEMPERATURE IN MODELLING PCB BIOACCUMULATION IN THE LAKE MICHIGAN FOOD WEB  

EPA Science Inventory

In most food web models, the exposure temperature of a food web is typically defined using a single spatial compartment. This essentially assumes that the predator and prey are exposed to the same temperature. However, in a large water body such as Lake Michigan, due to the spati...

180

Simplification of seagrass food webs across a gradient of nutrient enrichment  

Microsoft Academic Search

Anthropogenic nutrient enrichment has resulted in significant changes in food web structure. Although such changes have been associated with the loss of diversity and ecosystem services, little empirical work has been done to study food webs of similar systems across a nutrient enrichment gradient. We examined 11 seagrass beds along a gra- dient of increasing ?15N of primary consumers, where

Alexander Tewfik; Joseph B. Rasmussen; Kevin S. McCann

2007-01-01

181

Top-down and bottom-up diversity cascades in detrital vs. living food webs  

E-print Network

REPORT Top-down and bottom-up diversity cascades in detrital vs. living food webs Lee A. Dyer1 for maintaining diversity in biotic communities, but the indirect (Ã?cascadingÃ?) effects of top-down and bottom consumers in the detrital resources food web. These results support the hypotheses that top-down and bottom

Dyer, Lee

182

DEVELOPMENT, EVALUATION, AND APPLICATION OF A FOOD WEB BIOACCUMULATION MODEL FOR PCBS  

E-print Network

DEVELOPMENT, EVALUATION, AND APPLICATION OF A FOOD WEB BIOACCUMULATION MODEL FOR PCBS IN THE STRAIT Management Title of Research Project: Development, Evaluation, and Application of a Food Web Bioaccumulation of Georgia, I developed, parameterized, and tested a mechanistic bioaccumulation model for polychlorinated

183

Humans Strengthen Bottom-Up Effects and Weaken Trophic Cascades in a Terrestrial Food Web  

E-print Network

previous terrestrial food-web studies have been conducted. We used structural equation models (SEMsHumans Strengthen Bottom-Up Effects and Weaken Trophic Cascades in a Terrestrial Food Web Tyler B-down and bottom-up effects, respectively, may becoming superfluous. Given that most of the world's ecosystems

Hebblewhite, Mark

184

Developing a broader scientific foundation for river restoration: Columbia River food webs  

USGS Publications Warehouse

Well-functioning food webs are fundamental for sustaining rivers as ecosystems and maintaining associated aquatic and terrestrial communities. The current emphasis on restoring habitat structure—without explicitly considering food webs—has been less successful than hoped in terms of enhancing the status of targeted species and often overlooks important constraints on ecologically effective restoration. We identify three priority food web-related issues that potentially impede successful river restoration: uncertainty about habitat carrying capacity, proliferation of chemicals and contaminants, and emergence of hybrid food webs containing a mixture of native and invasive species. Additionally, there is the need to place these food web considerations in a broad temporal and spatial framework by understanding the consequences of altered nutrient, organic matter (energy), water, and thermal sources and flows, reconnecting critical habitats and their food webs, and restoring for changing environments. As an illustration, we discuss how the Columbia River Basin, site of one of the largest aquatic/riparian restoration programs in the United States, would benefit from implementing a food web perspective. A food web perspective for the Columbia River would complement ongoing approaches and enhance the ability to meet the vision and legal obligations of the US Endangered Species Act, the Northwest Power Act (Fish and Wildlife Program), and federal treaties with Northwest Indian Tribes while meeting fundamental needs for improved river management.

Naiman, Robert J.; Alldredge, Richard; Beauchamp, David A.; Bisson, Peter A.; Congleton, James; Henny, Charles J.; Huntly, Nancy; Lamberson, Roland; Levings, Colin; Merrill, Erik N.; Pearcy, William G.; Rieman, Bruce E.; Ruggerone, Gregory T.; Scarnecchia, Dennis; Smouse, Peter E.; Wood, Chris C.

2012-01-01

185

Can You Build It? Using Manipulatives to Assess Student Understanding of Food-Web Concepts  

ERIC Educational Resources Information Center

This article outlines an exercise that assesses student knowledge of food-web and energy-flow concepts. Students work in teams and use manipulatives to build food-web models based on criteria assigned by the instructor. The models are then peer reviewed according to guidelines supplied by the instructor.

Grumbine, Richard

2012-01-01

186

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

Technology Transfer Automated Retrieval System (TEKTRAN)

Food webs are known to have myriad trophic links between resource and consumer species. However, since the difficulties associated with characterizing the trophic position of organisms—particularly omnivores and higher-order consumers—have remained a major problem in food web ecology, our knowledge ...

187

Exploring Fish Diversity as a Determinant of Ecosystem Properties in Aquatic Food Webs  

ERIC Educational Resources Information Center

Dramatic biodiversity changes occurring globally from species loss and invasion have altered native food webs and ecosystem processes. My research objectives are to understand the consequences of fish diversity to freshwater systems by (1) examining the food web consequences of multiple top predators, (2) determining how biodiversity influences…

Carey, Michael P.

2009-01-01

188

Developing a broader scientific foundation for river restoration: Columbia River food webs.  

PubMed

Well-functioning food webs are fundamental for sustaining rivers as ecosystems and maintaining associated aquatic and terrestrial communities. The current emphasis on restoring habitat structure--without explicitly considering food webs--has been less successful than hoped in terms of enhancing the status of targeted species and often overlooks important constraints on ecologically effective restoration. We identify three priority food web-related issues that potentially impede successful river restoration: uncertainty about habitat carrying capacity, proliferation of chemicals and contaminants, and emergence of hybrid food webs containing a mixture of native and invasive species. Additionally, there is the need to place these food web considerations in a broad temporal and spatial framework by understanding the consequences of altered nutrient, organic matter (energy), water, and thermal sources and flows, reconnecting critical habitats and their food webs, and restoring for changing environments. As an illustration, we discuss how the Columbia River Basin, site of one of the largest aquatic/riparian restoration programs in the United States, would benefit from implementing a food web perspective. A food web perspective for the Columbia River would complement ongoing approaches and enhance the ability to meet the vision and legal obligations of the US Endangered Species Act, the Northwest Power Act (Fish and Wildlife Program), and federal treaties with Northwest Indian Tribes while meeting fundamental needs for improved river management. PMID:23197837

Naiman, Robert J; Alldredge, J Richard; Beauchamp, David A; Bisson, Peter A; Congleton, James; Henny, Charles J; Huntly, Nancy; Lamberson, Roland; Levings, Colin; Merrill, Erik N; Pearcy, William G; Rieman, Bruce E; Ruggerone, Gregory T; Scarnecchia, Dennis; Smouse, Peter E; Wood, Chris C

2012-12-26

189

Neighborhood Effects on Arthropod Diversity and Food Webs Laura Taylor-Taft and Stan Faeth  

E-print Network

Neighborhood Effects on Arthropod Diversity and Food Webs Laura Taylor-Taft and Stan Faeth School supplemented with 6 brittlebush plants. Plant productivity, arthropod diversity, abundance and biomass diversity and altered species composition. Consequently, urbanization results in changing the food web

Hall, Sharon J.

190

Qualitative analysis of two resource-based food-web models of three interacting species  

Microsoft Academic Search

Two models are developed and analysed for resource-based food webs. In model 1, the food web originates from abiotic resources but the environment is closed with respect to it; while, in model 2, the available resource is biotic in nature but the environment is open with respect to resource supply. Community structure as well as the physical properties are taken

Dipak Kesh; A. K. Sarkar; A. B. Roy

1997-01-01

191

Benthic versus Planktonic Foundations of Three Lake Superior Coastal Food Webs  

EPA Science Inventory

The structure of aquatic food webs can provide information on system function, trophic dynamics and, potentially, responses to anthropogenic stressors. Stable isotope analyses in a Lake Superior coastal wetland (Allouez Bay, WI, USA) revealed that the food web was based upon carb...

192

Comparison of the structure of lower and upper estuary food webs for Yaquina Bay (OR)  

EPA Science Inventory

Food web models can be used to estimate effects of water quality, habitat distribution or species loss on productivity, carbon flow and ecosystem service production in Pacific NW estuaries. Here we present a comparison of floral and faunal data used to parameterize food web mode...

193

Supporting Online Material for Generalized Models Reveal Stabilizing Factors in Food Webs  

E-print Network

can be analyzed at low computational cost. In the GM of food webs, computation of steady states canSupporting Online Material for Generalized Models Reveal Stabilizing Factors in Food Webs Thilo Generalized modeling. GM is based on the insight that, in general, the computation of steady states is much

194

Developing a broader scientific foundation for river restoration: Columbia River food webs  

PubMed Central

Well-functioning food webs are fundamental for sustaining rivers as ecosystems and maintaining associated aquatic and terrestrial communities. The current emphasis on restoring habitat structure—without explicitly considering food webs—has been less successful than hoped in terms of enhancing the status of targeted species and often overlooks important constraints on ecologically effective restoration. We identify three priority food web-related issues that potentially impede successful river restoration: uncertainty about habitat carrying capacity, proliferation of chemicals and contaminants, and emergence of hybrid food webs containing a mixture of native and invasive species. Additionally, there is the need to place these food web considerations in a broad temporal and spatial framework by understanding the consequences of altered nutrient, organic matter (energy), water, and thermal sources and flows, reconnecting critical habitats and their food webs, and restoring for changing environments. As an illustration, we discuss how the Columbia River Basin, site of one of the largest aquatic/riparian restoration programs in the United States, would benefit from implementing a food web perspective. A food web perspective for the Columbia River would complement ongoing approaches and enhance the ability to meet the vision and legal obligations of the US Endangered Species Act, the Northwest Power Act (Fish and Wildlife Program), and federal treaties with Northwest Indian Tribes while meeting fundamental needs for improved river management. PMID:23197837

Naiman, Robert J.; Alldredge, J. Richard; Beauchamp, David A.; Bisson, Peter A.; Congleton, James; Henny, Charles J.; Huntly, Nancy; Lamberson, Roland; Levings, Colin; Merrill, Erik N.; Pearcy, William G.; Rieman, Bruce E.; Ruggerone, Gregory T.; Scarnecchia, Dennis; Smouse, Peter E.; Wood, Chris C.

2012-01-01

195

Variable and complex food web structures revealed by exploring missing trophic links between birds and biofilm  

E-print Network

LETTER Variable and complex food web structures revealed by exploring missing trophic links between of complex and dynamic food webs in nature. Here, we empirically demonstrate a missing link, both critical-interpretation of niche differentiation. We contend that exploring missing links is a necessity for revealing true network

196

Spatial scales of carbon flow in a river food web  

USGS Publications Warehouse

Spatial extents of food webs that support stream and river consumers are largely unknown, but such information is essential for basic understanding and management of lotic ecosystems. We used predictable variation in algal ??13C with water velocity, and measurements of consumer ??13C and ??15N to examine carbon flow and trophic structure in food webs of the South Fork Eel River in Northern California. Analyses of ??13C showed that the most abundant macroinvertebrate groups (collector-gatherers and scrapers) relied on algae from local sources within their riffle or shallow pool habitats. In contrast, filter-feeding invertebrates in riffles relied in part on algal production derived from upstream shallow pools. Riffle invertebrate predators also relied in part on consumers of pool-derived algal carbon. One abundant taxon drifting from shallow pools and riffles (baetid mayflies) relied on algal production derived from the habitats from which they dispersed. The trophic linkage from pool algae to riffle invertebrate predators was thus mediated through either predation on pool herbivores dispersing into riffles, or on filter feeders. Algal production in shallow pool habitats dominated the resource base of vertebrate predators in all habitats at the end of the summer. We could not distinguish between the trophic roles of riffle algae and terrestrial detritus, but both carbon sources appeared to play minor roles for vertebrate consumers. In shallow pools, small vertebrates, including three-spined stickleback (Gasterosteus aculeatus), roach (Hesperoleucas symmetricus), and rough-skinned newts (Taricha granulosa), relied on invertebrate prey derived from local pool habitats. During the most productive summer period, growth of all size classes of steelhead and resident rainbow trout (Oncorhynchus mykiss) in all habitats (shallow pools, riffles, and deep unproductive pools) was largely derived from algal production in shallow pools. Preliminary data suggest that the strong role of shallow pool algae in riffle steelhead growth during summer periods was due to drift of pool invertebrates to riffles, rather than movement of riffle trout. Data for ??15N showed that resident rainbow trout (25-33 cm standard length) in deep pools preyed upon small size classes of juvenile steelhead that were most often found in riffles or shallow pools. While many invertebrate consumers relied primarily on algal production derived from local habitats, our study shows that growth of top predators in the river is strongly linked to food webs in adjacent habitats. These results suggest a key role for emigration of aquatic prey in determining carbon flow to top predators.

Finlay, J.C.; Khandwala, S.; Power, M.E.

2002-01-01

197

Food webs: a ladder for picking strawberries or a practical tool for practical problems?  

PubMed

While food webs have provided a rich vein of research material over the last 50 years, they have largely been the subject matter of the pure ecologist working in natural habitats. While there are some notable exceptions to this trend, there are, as I explain in this paper, many applied questions that could be answered using a food web approach. The paper is divided into two halves. The first half provides a brief review of six areas where food webs have begun to be used as an applied tool: restoration ecology, alien species, biological control, conservation ecology, habitat management and global warming. The second half outlines five areas in which a food web approach could prove very rewarding: urban ecology, agroecology, habitat fragmentation, cross-habitat food webs and ecosystem services. PMID:19451120

Memmott, Jane

2009-06-27

198

Food webs: a ladder for picking strawberries or a practical tool for practical problems?  

PubMed Central

While food webs have provided a rich vein of research material over the last 50 years, they have largely been the subject matter of the pure ecologist working in natural habitats. While there are some notable exceptions to this trend, there are, as I explain in this paper, many applied questions that could be answered using a food web approach. The paper is divided into two halves. The first half provides a brief review of six areas where food webs have begun to be used as an applied tool: restoration ecology, alien species, biological control, conservation ecology, habitat management and global warming. The second half outlines five areas in which a food web approach could prove very rewarding: urban ecology, agroecology, habitat fragmentation, cross-habitat food webs and ecosystem services. PMID:19451120

Memmott, Jane

2009-01-01

199

Watershed and Lake Influences on the Energetic Base of Coastal Wetland Food Webs across the Great Lakes Basin  

EPA Science Inventory

This manuscript examines the responses of Great Lakes coastal wetland food webs to nutrient enrichment and identifies three classes of systems whose food webs respond differently. Or is that differentially? Anyway, coastal wetlands with relatively long hydraulic residence times ...

200

Cranberry Bogs: The effect of cultivation and restoration on habitat distribution, benthic invertebrate communities, and food webs in stream ecosystems  

E-print Network

invertebrate communities, and food webs in stream ecosystems Kimberly Morrell Department of Biology, Carleton habitat distribution, benthic invertebrate communities, and food webs in stream ecosystems. To understand transects and analyzed benthic invertebrate samples. Stable isotope analyses clarified the relationships

Vallino, Joseph J.

201

Bioaccumulation of organochlorines in the Arctic marine food web  

SciTech Connect

Five classes of organochlorine (OC) compounds (hexachlorocyclohexane (HCB and HCHs), cyclodienes, isomers of DDT and its metabolites and congeners of polychlorinated biphenyls (PCBs) and toxaphene (CHBs)) have been detected in under-ice epontic particulate matter and tissue samples of marine biota from lower trophic levels of the Arctic Ocean at sites in Barrow Strait within the Canadian archipelago (75{degree}N), coastal (79{degree}N) and central Arctic basin (85{degree}N) locations. HCBs, PCBs, isomers of DDT and DDE, chlordane, dieldrin, alpha-endosulphan, HCB and {alpha}-HCH were present in quantifiable amounts in all samples. {beta}- and {gamma}-HCH and the cyclodienes aldrin, endrin, heptachlor, heptachlor epoxide, methoxychlor and mirex were detected but could not be quantified. All OCs measured in biota were also present in the Arctic atmosphere, particulate and dissolved fractions of snow, ice melt water and seawater, Small bodied marine organisms such as zooplankton and amphipods which are short-lived have a lower lipid content for storage of OCs than larger animals such as fish and mammals. Biomagnification factors calculated from presumed predator-prey links in the marine food web varied over two orders of magnitude for different OCs. Ratios for epontic particulates and plankton (< 10) were generally lower than values for trophic links between amphipods and published values for arctic marine fish and mammals (10--100). PCBs, DDT and chlordanes are biomagnified in the Arctic marine food web to a far greater degree than more abundant OC compounds such as HCHs and HCB that have a higher water solubility.

Hargrave, B.; Phillips, G.; Vass, W.; Harding, G. [Department of Fisheries and Oceans, Dartmouth, Nova Scotia (Canada). Bedford Inst. of Oceanography; Welch, H. [Department of Fisheries and Oceans, Winnipeg, Manitoba (Canada). Freshwater Inst.

1995-12-31

202

Deep-Sea Research I 51 (2004) 12451274 Carbon fluxes through food webs of the eastern equatorial  

E-print Network

Deep-Sea Research I 51 (2004) 1245­1274 Carbon fluxes through food webs of the eastern equatorial inverse and network analyses to examine food web interactions at 0 , 140 W during EqPac time approach allowed us to trace the pathway of fixed carbon through a representative food web

Jackson, George

2004-01-01

203

Food web architecture and basal resources interact to determine biomass and stoichiometric cascades along a benthic food web.  

PubMed

Understanding the effects of predators and resources on primary producers has been a major focus of interest in ecology. Within this context, the trophic cascade concept especially concerning the pelagic zone of lakes has been the focus of the majority of these studies. However, littoral food webs could be especially interesting because base trophic levels may be strongly regulated by consumers and prone to be light limited. In this study, the availability of nutrients and light and the presence of an omnivorous fish (Hyphessobrycon bifasciatus) were manipulated in enclosures placed in a humic coastal lagoon (Cabiúnas Lagoon, Macaé - RJ) to evaluate the individual and interactive effects of resource availability (nutrients and light) and food web configuration on the biomass and stoichiometry of periphyton and benthic grazers. Our findings suggest that light and nutrients interact to determine periphyton biomass and stoichiometry, which propagates to the consumer level. We observed a positive effect of the availability of nutrients on periphytic biomass and grazers' biomass, as well as a reduction of periphytic C?N?P ratios and an increase of grazers' N and P content. Low light availability constrained the propagation of nutrient effects on periphyton biomass and induced higher periphytic C?N?P ratios. The effects of fish presence strongly interacted with resource availability. In general, a positive effect of fish presence was observed for the total biomass of periphyton and grazer's biomass, especially with high resource availability, but the opposite was found for periphytic autotrophic biomass. Fish also had a significant effect on periphyton stoichiometry, but no effect was observed on grazers' stoichiometric ratios. In summary, we observed that the indirect effect of fish predation on periphyton biomass might be dependent on multiple resources and periphyton nutrient stoichiometric variation can affect consumers' stoichiometry. PMID:21789234

Guariento, Rafael D; Carneiro, Luciana S; Caliman, Adriano; Leal, João J F; Bozelli, Reinaldo L; Esteves, Francisco A

2011-01-01

204

Trophic groups and modules: two levels of group detection in food webs.  

PubMed

Within food webs, species can be partitioned into groups according to various criteria. Two notions have received particular attention: trophic groups (TGs), which have been used for decades in the ecological literature, and more recently, modules. The relationship between these two group concepts remains unknown in empirical food webs. While recent developments in network theory have led to efficient methods for detecting modules in food webs, the determination of TGs (groups of species that are functionally similar) is largely based on subjective expert knowledge. We develop a novel algorithm for TG detection. We apply this method to empirical food webs and show that aggregation into TGs allows for the simplification of food webs while preserving their information content. Furthermore, we reveal a two-level hierarchical structure where modules partition food webs into large bottom-top trophic pathways, whereas TGs further partition these pathways into groups of species with similar trophic connections. This provides new perspectives for the study of dynamical and functional consequences of food-web structure, bridging topological and dynamical analysis. TGs have a clear ecological meaning and are found to provide a trade-off between network complexity and information loss. PMID:25878127

Gauzens, Benoit; Thébault, Elisa; Lacroix, Gérard; Legendre, Stéphane

2015-05-01

205

Food Webs in Relation to Variation in the Environment and Species Assemblage: A Multivariate Approach  

PubMed Central

The abiotic environment has strong influences on the growth, survival, behavior, and ecology of aquatic organisms. Biotic interactions and species life histories interact with abiotic factors to structure the food web. One measure of food-web structure is food-chain length. Several hypotheses predict a linear relationship between one environmental variable (e.g., disturbance or ecosystem size) and food-chain length. However, many abiotic and biotic variables interact in diverse ways to structure a community, and may affect other measures of food web structure besides food-chain length. This study took a multivariate approach to test the influence of several important environmental variables on four food-web characteristics measured in nine ponds along a hydroperiod gradient over two years. This approach allowed for testing the ecosystem size and dynamic constraints hypotheses while in context of other possibly interacting environmental variables. The relationship between amphibian and invertebrate communities and pond habitat variables was assessed to understand the underlying food-web structure. Hydroperiod and pond area had a strong influence on amphibian and invertebrate communities, trophic diversity and ?15N range. The range in ?13C values responded strongly to dissolved oxygen. Food-chain length responded to multiple environmental variables. Invertebrate and amphibian communities were structured by pond hydroperiod which in turn influenced the trophic diversity of the food web. The results of this study suggest food-chain length is influenced by environmental variation and species assemblage and that a multivariate approach may allow us to better understand the dynamics within and across aquatic food webs. PMID:25880079

Schriever, Tiffany A.

2015-01-01

206

Snow Web 2.0: The Next Generation of Antarctic Meteorological Monitoring Systems?  

NASA Astrophysics Data System (ADS)

Adequate in-situ observation of the Antarctic lower atmosphere has proved problematic, due to a combination of the inhospitable nature and extent of the continent. Traditional weather stations are expensive, subject to extreme weather for long periods and are often isolated, and as such are prone to failure and logistically difficult to repair. We have developed the first generation of an extended system of atmospheric sensors, each costing a fraction of the price of a traditional weather station. The system is capable of performing all of the monitoring tasks of a traditional station, but has built-in redundancy over the traditional approach because many units can be deployed in a relatively small area for similar expenditure as one large weather station. Furthermore, each unit is equipped with wireless networking capabilities and so is able to share information with those units in its direct vicinity. This allows for the ferrying of collected information to a manned observation station and hence the ability to monitor data in real-time. The distributed nature of the data collected can then be used as a stand-alone product to investigate small-scale weather and climate phenomena or integrated into larger studies and be used to monitor wide regions. GPS hardware installed on each unit also allows for high-resolution glacier or ice-shelf tracking. As a testing and data gathering study, eighteen such weather stations were deployed in the vicinity of Scott Base, Ross Island, Antarctica over the 2011/12 summer season. This presentation reports on findings from this field study, and discusses possibilities for the future.

Coggins, J.; McDonald, A.; Plank, G.; Pannell, M.; Ward, R.; Parsons, S.

2012-04-01

207

Food webs and carbon flux in the Barents Sea  

NASA Astrophysics Data System (ADS)

Within the framework of the physical forcing, we describe and quantify the key ecosystem components and basic food web structure of the Barents Sea. Emphasis is given to the energy flow through the ecosystem from an end-to-end perspective, i.e. from bacteria, through phytoplankton and zooplankton to fish, mammals and birds. Primary production in the Barents is on average 93 g C m -2 y -1, but interannually highly variable (±19%), responding to climate variability and change (e.g. variations in Atlantic Water inflow, the position of the ice edge and low-pressure pathways). The traditional focus upon large phytoplankton cells in polar regions seems less adequate in the Barents, as the cell carbon in the pelagic is most often dominated by small cells that are entangled in an efficient microbial loop that appears to be well coupled to the grazing food web. Primary production in the ice-covered waters of the Barents is clearly dominated by planktonic algae and the supply of ice biota by local production or advection is small. The pelagic-benthic coupling is strong, in particular in the marginal ice zone. In total 80% of the harvestable production is channelled through the deep-water communities and benthos. 19% of the harvestable production is grazed by the dominating copepods Calanus finmarchicus and C. glacialis in Atlantic or Arctic Water, respectively. These two species, in addition to capelin ( Mallotus villosus) and herring ( Clupea harengus), are the keystone organisms in the Barents that create the basis for the rich assemblage of higher trophic level organisms, facilitating one of the worlds largest fisheries (capelin, cod, shrimps, seals and whales). Less than 1% of the harvestable production is channelled through the most dominating higher trophic levels such as cod, harp seals, minke whales and sea birds. Atlantic cod, seals, whales, birds and man compete for harvestable energy with similar shares. Climate variability and change, differences in recruitment, variable resource availability, harvesting restrictions and management schemes will influence the resource exploitation between these competitors, that basically depend upon the efficient energy transfer from primary production to highly successful, lipid-rich zooplankton and pelagic fishes.

Wassmann, Paul; Reigstad, Marit; Haug, Tore; Rudels, Bert; Carroll, Michael L.; Hop, Haakon; Gabrielsen, Geir Wing; Falk-Petersen, Stig; Denisenko, Stanislav G.; Arashkevich, Elena; Slagstad, Dag; Pavlova, Olga

2006-10-01

208

Analysis of governmental Web sites on food safety issues: a global perspective.  

PubMed

Despite a growing concern over food safety issues, as well as a growing dependence on the Internet as a source of information, little research has been done to examine the presence and relevance of food safety-related information on Web sites. The study reported here conducted Web site analysis in order to examine the current operational status of governmental Web sites on food safety issues. The study also evaluated Web site usability, especially information dimensionalities such as utility, currency, and relevance of content, from the perspective of the English-speaking consumer. Results showed that out of 192 World Health Organization members, 111 countries operated governmental Web sites that provide information about food safety issues. Among 171 searchable Web sites from the 111 countries, 123 Web sites (71.9 percent) were accessible, and 81 of those 123 (65.9 percent) were available in English. The majority of Web sites offered search engine tools and related links for more information, but their availability and utility was limited. In terms of content, 69.9 percent of Web sites offered information on foodborne-disease outbreaks, compared with 31.5 percent that had travel- and health-related information. PMID:17066944

Namkung, Young; Almanza, Barbara A

2006-10-01

209

Mercury in the Pelagic Food Web of Lake Champlain  

PubMed Central

Lake Champlain continues to experience mercury contamination resulting in public advisories to limit human consumption of top trophic level fish such as walleye. Prior research suggested that mercury levels in biota could be modified by differences in ecosystem productivity as well as mercury loadings. We investigated relationships between mercury in different trophic levels in Lake Champlain. We measured inorganic and methyl mercury in water, seston, and two size fractions of zooplankton from 13 sites representing a range of nutrient loading conditions and productivity. Biomass varied significantly across lake segments in all measured ecosystem compartments in response to significant differences in nutrient levels. Local environmental factors such as alkalinity influenced the partitioning of mercury between water and seston. Mercury incorporation into biota was influenced by the biomass and mercury content of different ecosystem strata. Pelagic fish tissue mercury was a function of fish length and the size of the mercury pool associated with large zooplankton. We used these observations to parameterize a model of mercury transfers in the Lake Champlain food web that accounts for ecosystem productivity effects. Simulations using the mercury trophic transfer model suggest that reductions of 25 to 75% in summertime dissolved eplimnetic total mercury will likely allow fish tissue mercury concentrations to drop to the target level of 0.3 µg g?1 in a 40-cm fish in all lake segments. Changes in nutrient loading and ecosystem productivity in eutrophic segments may delay any response to reduced dissolved mercury and may result in increases in fish tissue mercury. PMID:22193540

Chen, Celia; Kamman, Neil; Shanley, James; Chalmers, Ann; Jackson, Brian; Taylor, Vivien; Smeltzer, Eric; Stangel, Pete; Shambaugh, Angela

2013-01-01

210

Mercury in the pelagic food web of Lake Champlain.  

PubMed

Lake Champlain continues to experience mercury contamination resulting in public advisories to limit human consumption of top trophic level fish such as walleye. Prior research suggested that mercury levels in biota could be modified by differences in ecosystem productivity as well as mercury loadings. We investigated relationships between mercury in different trophic levels in Lake Champlain. We measured inorganic and methyl mercury in water, seston, and two size fractions of zooplankton from 13 sites representing a range of nutrient loading conditions and productivity. Biomass varied significantly across lake segments in all measured ecosystem compartments in response to significant differences in nutrient levels. Local environmental factors such as alkalinity influenced the partitioning of mercury between water and seston. Mercury incorporation into biota was influenced by the biomass and mercury content of different ecosystem strata. Pelagic fish tissue mercury was a function of fish length and the size of the mercury pool associated with large zooplankton. We used these observations to parameterize a model of mercury transfers in the Lake Champlain food web that accounts for ecosystem productivity effects. Simulations using the mercury trophic transfer model suggest that reductions of 25-75% in summertime dissolved eplimnetic total mercury will likely allow fish tissue mercury concentrations to drop to the target level of 0.3 ?g g(-1) in a 40-cm fish in all lake segments. Changes in nutrient loading and ecosystem productivity in eutrophic segments may delay any response to reduced dissolved mercury and may result in increases in fish tissue mercury. PMID:22193540

Miller, Eric K; Chen, Celia; Kamman, Neil; Shanley, James; Chalmers, Ann; Jackson, Brian; Taylor, Vivien; Smeltzer, Eric; Stangel, Pete; Shambaugh, Angela

2012-04-01

211

Dispersed Oil Disrupts Microbial Pathways in Pelagic Food Webs  

PubMed Central

Most of the studies of microbial processes in response to the Deepwater Horizon oil spill focused on the deep water plume, and not on the surface communities. The effects of the crude oil and the application of dispersants on the coastal microbial food web in the northern Gulf of Mexico have not been well characterized even though these regions support much of the fisheries production in the Gulf. A mesocosm experiment was carried out to determine how the microbial community off the coast of Alabama may have responded to the influx of surface oil and dispersants. While the addition of glucose or oil alone resulted in an increase in the biomass of ciliates, suggesting transfer of carbon to higher trophic levels was likely; a different effect was seen in the presence of dispersant. The addition of dispersant or dispersed oil resulted in an increase in the biomass of heterotrophic prokaryotes, but a significant inhibition of ciliates, suggesting a reduction in grazing and decrease in transfer of carbon to higher trophic levels. Similar patterns were observed in two separate experiments with different starting nutrient regimes and microbial communities suggesting that the addition of dispersant and dispersed oil to the northern Gulf of Mexico waters in 2010 may have reduced the flow of carbon to higher trophic levels, leading to a decrease in the production of zooplankton and fish on the Alabama shelf. PMID:22860136

Ortmann, Alice C.; Anders, Jennifer; Shelton, Naomi; Gong, Limin; Moss, Anthony G.; Condon, Robert H.

2012-01-01

212

Transfer of heavy metals through terrestrial food webs: a review.  

PubMed

Heavy metals are released into the environment by both anthropogenic and natural sources. Highly reactive and often toxic at low concentrations, they may enter soils and groundwater, bioaccumulate in food webs, and adversely affect biota. Heavy metals also may remain in the environment for years, posing long-term risks to life well after point sources of heavy metal pollution have been removed. In this review, we compile studies of the community-level effects of heavy metal pollution, including heavy metal transfer from soils to plants, microbes, invertebrates, and to both small and large mammals (including humans). Many factors contribute to heavy metal accumulation in animals including behavior, physiology, and diet. Biotic effects of heavy metals are often quite different for essential and non-essential heavy metals, and vary depending on the specific metal involved. They also differ for adapted organisms, including metallophyte plants and heavy metal-tolerant insects, which occur in naturally high-metal habitats (such as serpentine soils) and have adaptations that allow them to tolerate exposure to relatively high concentrations of some heavy metals. Some metallophyte plants are hyperaccumulators of certain heavy metals and new technologies using them to clean metal-contaminated soil (phytoextraction) may offer economically attractive solutions to some metal pollution challenges. These new technologies provide incentive to catalog and protect the unique biodiversity of habitats that have naturally high levels of heavy metals. PMID:25800370

Gall, Jillian E; Boyd, Robert S; Rajakaruna, Nishanta

2015-04-01

213

SEASONAL DYNAMICS OF PCB ACCUMULATION IN A GREAT LAKES FOOD WEB. (R825151)  

EPA Science Inventory

Seston, sediment, settling organic matter, and food web members were collected from Grand Traverse Bay, Lake Michigan, between April 1997 and September 1998 to examine PCB and toxaphene biomagnification. Stable isotopes of nitrogen and carbon were analyzed in sampl...

214

Contributions of stable-isotope data to elucidating food webs of Mediterranean rocky littoral fishes  

Microsoft Academic Search

The food webs of rocky infra-littoral ecosystems in the Mediterranean have been little studied. In this investigation stable\\u000a isotopes and dietary data were compared in an attempt to describe features of the food webs concerned. ?13C and ?15N were determined for plants, invertebrates and fishes from the Bay of Calvi, Corsica. Dietary data were derived from the\\u000a literature. ?13C of

John K. Pinnegar; N. V. C. Polunin

2000-01-01

215

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

USGS Publications Warehouse

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.

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

2009-01-01

216

Spatial Differences in East Scotia Ridge Hydrothermal Vent Food Webs: Influences of Chemistry, Microbiology and Predation on Trophodynamics  

PubMed Central

The hydrothermal vents on the East Scotia Ridge are the first to be explored in the Antarctic and are dominated by large peltospiroid gastropods, stalked barnacles (Vulcanolepas sp.) and anomuran crabs (Kiwa sp.) but their food webs are unknown. Vent fluid and macroconsumer samples were collected at three vent sites (E2, E9N and E9S) at distances of tens of metres to hundreds of kilometres apart with contrasting vent fluid chemistries to describe trophic interactions and identify potential carbon fixation pathways using stable isotopes. ?13C of dissolved inorganic carbon from vent fluids ranged from ?4.6‰ to 0.8‰ at E2 and from ?4.4‰ to 1.5‰ at E9. The lowest macroconsumer ?13C was observed in peltospiroid gastropods (?30.0‰ to ?31.1‰) and indicated carbon fixation via the Calvin-Benson-Bassham (CBB) cycle by endosymbiotic gamma-Proteobacteria. Highest ?13C occurred in Kiwa sp. (?19.0‰ to ?10.5‰), similar to that of the epibionts sampled from their ventral setae. Kiwa sp. ?13C differed among sites, which were attributed to spatial differences in the epibiont community and the relative contribution of carbon fixed via the reductive tricarboxylic acid (rTCA) and CBB cycles assimilated by Kiwa sp. Site differences in carbon fixation pathways were traced into higher trophic levels e.g. a stichasterid asteroid that predates on Kiwa sp. Sponges and anemones at the periphery of E2 assimilated a proportion of epipelagic photosynthetic primary production but this was not observed at E9N. Differences in the ?13C and ?34S values of vent macroconsumers between E2 and E9 sites suggest the relative contributions of photosynthetic and chemoautotrophic carbon fixation (rTCA v CBB) entering the hydrothermal vent food webs vary between the sites. PMID:23762393

Reid, William D. K.; Sweeting, Christopher J.; Wigham, Ben D.; Zwirglmaier, Katrin; Hawkes, Jeffrey A.; McGill, Rona A. R.; Linse, Katrin; Polunin, Nicholas V. C.

2013-01-01

217

Spatial differences in East scotia ridge hydrothermal vent food webs: influences of chemistry, microbiology and predation on trophodynamics.  

PubMed

The hydrothermal vents on the East Scotia Ridge are the first to be explored in the Antarctic and are dominated by large peltospiroid gastropods, stalked barnacles (Vulcanolepas sp.) and anomuran crabs (Kiwa sp.) but their food webs are unknown. Vent fluid and macroconsumer samples were collected at three vent sites (E2, E9N and E9S) at distances of tens of metres to hundreds of kilometres apart with contrasting vent fluid chemistries to describe trophic interactions and identify potential carbon fixation pathways using stable isotopes. ?(13)C of dissolved inorganic carbon from vent fluids ranged from -4.6‰ to 0.8‰ at E2 and from -4.4‰ to 1.5‰ at E9. The lowest macroconsumer ?(13)C was observed in peltospiroid gastropods (-30.0‰ to -31.1‰) and indicated carbon fixation via the Calvin-Benson-Bassham (CBB) cycle by endosymbiotic gamma-Proteobacteria. Highest ?(13)C occurred in Kiwa sp. (-19.0‰ to -10.5‰), similar to that of the epibionts sampled from their ventral setae. Kiwa sp. ?(13)C differed among sites, which were attributed to spatial differences in the epibiont community and the relative contribution of carbon fixed via the reductive tricarboxylic acid (rTCA) and CBB cycles assimilated by Kiwa sp. Site differences in carbon fixation pathways were traced into higher trophic levels e.g. a stichasterid asteroid that predates on Kiwa sp. Sponges and anemones at the periphery of E2 assimilated a proportion of epipelagic photosynthetic primary production but this was not observed at E9N. Differences in the ?(13)C and ?(34)S values of vent macroconsumers between E2 and E9 sites suggest the relative contributions of photosynthetic and chemoautotrophic carbon fixation (rTCA v CBB) entering the hydrothermal vent food webs vary between the sites. PMID:23762393

Reid, William D K; Sweeting, Christopher J; Wigham, Ben D; Zwirglmaier, Katrin; Hawkes, Jeffrey A; McGill, Rona A R; Linse, Katrin; Polunin, Nicholas V C

2013-01-01

218

The role of microorganisms in a planktonic food web of a floodplain lake.  

PubMed

Food webs include complex ecological interactions that define the flow of matter and energy, and are fundamental in understanding the functioning of an ecosystem. Temporal variations in the densities of communities belonging to the planktonic food web (i.e., microbial: bacteria, flagellate, and ciliate; and grazing: zooplankton and phytoplankton) were investigated, aiming to clarify the interactions between these organisms and the dynamics of the planktonic food web in a floodplain lake. We hypothesized that hydrological pulse determines the path of matter and energy flow through the planktonic food web of this floodplain lake. Data were collected monthly from March 2007 to February 2008 at three different sites in Guaraná Lake (Mato Grosso do Sul State, Brazil). The path analysis provided evidence that the dynamics of the planktonic food web was strongly influenced by the hydrological pulse. The high-water period favored interactions among the organisms of the microbial loop, rather than their relationships with zooplankton and phytoplankton. Therefore, in this period, the strong interaction among the organisms of the grazing food chain suggests that the microbial loop functions as a sink of matter and energy. In turn, in the low-water period, higher primary productivity appeared to favor different interactions between the components of the grazing food chain and microorganisms, which would function as a link to the higher trophic levels. PMID:25213653

Segovia, Bianca Trevizan; Pereira, Danielle Goeldner; Bini, Luis Mauricio; de Meira, Bianca Ramos; Nishida, Verônica Sayuri; Lansac-Tôha, Fabio Amodêo; Velho, Luiz Felipe Machado

2015-02-01

219

Deleting species from model food webs Christopher Quince, Paul G. Higgs and Alan J. McKane  

E-print Network

-down keystone species indices. We also considered which properties of the web as a whole influenced itsDeleting species from model food webs Christopher Quince, Paul G. Higgs and Alan J. McKane Quince, C., Higgs, P. G. and McKane, A. J. 2005. Deleting species from model food webs. Á/ Oikos 110: 283Á

McKane, Alan

220

Road Salts as Environmental Constraints in Urban Pond Food Webs  

PubMed Central

Freshwater salinization is an emerging environmental filter in urban aquatic ecosystems that receive chloride road salt runoff from vast expanses of impervious surface cover. Our study was designed to evaluate the effects of chloride contamination on urban stormwater pond food webs through changes in zooplankton community composition as well as density and biomass of primary producers and consumers. From May – July 2009, we employed a 2×2×2 full-factorial design to manipulate chloride concentration (low?=?177 mg L?1 Cl?/high?=?1067 mg L?1 Cl?), gray treefrog (Hyla versicolor) tadpoles (presence/absence) and source of stormwater pond algae and zooplankton inoculum (low conductance/high conductance urban ponds) in 40, 600-L mesocosms. Road salt did serve as a constraint on zooplankton community structure, driving community divergence between the low and high chloride treatments. Phytoplankton biomass (chlorophyll [a] µg L?1) in the mesocosms was significantly greater for the high conductance inoculum (P<0.001) and in the high chloride treatment (P?=?0.046), whereas periphyton biomass was significantly lower in the high chloride treatment (P?=?0.049). Gray treefrog tadpole time to metamorphosis did not vary significantly between treatments. However, mass at metamorphosis was greater among tadpoles that experienced a faster than average time to metamorphosis and exposure to high chloride concentrations (P?=?0.039). Our results indicate differential susceptibility to chloride salts among algal resources and zooplankton taxa, and further suggest that road salts can act as a significant environmental constraint on urban stormwater pond communities. PMID:24587259

Van Meter, Robin J.; Swan, Christopher M.

2014-01-01

221

Food web structure in oil sands reclaimed wetlands.  

PubMed

Boreal wetlands play an important role in global carbon balance. However, their ecosystem function is threatened by direct anthropogenic disturbance and climate change. Oil sands surface mining in the boreal regions of Western Canada denudes tracts of land of organic materials, leaves large areas in need of reclamation, and generates considerable quantities of extraction process-affected materials. Knowledge and validation of reclamation techniques that lead to self-sustaining wetlands has lagged behind development of protocols for reclaiming terrestrial systems. It is important to know whether wetlands reclaimed with oil sands process materials can be restored to levels equivalent to their original ecosystem function. We approached this question by assessing carbon flows and food web structure in naturally formed and oil sands-affected wetlands constructed in 1970-2004 in the postmining landscape. We evaluated whether a prescribed reclamation strategy, involving organic matter amendment, accelerated reclaimed wetland development, leading to wetlands that were more similar to their natural marsh counterparts than wetlands that were not supplemented with organic matter. We measured compartment standing stocks for bacterioplankton, microbial biofilm, macrophytes, detritus, and zoobenthos; concentrations of dissolved organic carbon and residual naphthenic acids; and microbial production, gas fluxes, and aquatic-terrestrial exports (i.e., aquatic insect emergence). The total biomass of several biotic compartments differed significantly between oil sands and reference wetlands. Submerged macrophyte biomass, macroinvertebrate trophic diversity, and predator biomass and richness were lower in oil sands-affected wetlands than in reference wetlands. There was insufficient evidence to conclude that wetland age and wetland amendment with peat-mineral mix mitigate effects of oil sands waste materials on the fully aquatic biota. Although high variability was observed within most compartments, our data show that 20-year-old wetlands containing oil sands material have not yet reached the same level of function as their reference counterparts. PMID:23967574

Kovalenko, K E; Ciborowski, J J H; Daly, C; Dixon, D G; Farwell, A J; Foote, A L; Frederick, K R; Costa, J M Gardner; Kennedy, K; Liber, K; Roy, M C; Slama, C A; Smits, J E G

2013-07-01

222

Interaction strength combinations and the overfishing of a marine food web  

Microsoft Academic Search

The stability of ecological communities largely depends on the strength of interactions between predators and their prey. Here we show that these interaction strengths are structured nonrandomly in a large Caribbean marine food web. Specifically, the cooccurrence of strong interactions on two consecutive levels of food chains occurs less frequently than expected by chance. Even when they occur, these strongly

Jordi Bascompte; Carlos J. Melián; Enric Sala

2005-01-01

223

Changes in the Pelagic Food Web of Southern Lake Michigan Primary Investigator: Henry Vanderploeg -NOAA GLERL  

E-print Network

for a number of fishes, has completely disappeared from the southern basin of Lake Michigan. This projectChanges in the Pelagic Food Web of Southern Lake Michigan Primary Investigator: Henry Vanderploeg and plankton in southern Lake Michigan. We seek to document recent and long-term changes in the pelagic food

224

Food Chains & Webs. A Multimedia CD-ROM. [CD-ROM].  

ERIC Educational Resources Information Center

This CD-ROM is designed for classroom and individual use to teach and learn about food chains and food webs. Integrated animations, custom graphics, three-dimensional representations, photographs, and sound are featured for use in user-controlled activities. Interactive lessons are available to reinforce the subject material. Pre- and post-testing…

2001

225

Methylmercury enters an aquatic food web through acidophilic microbial mats in Yellowstone National  

E-print Network

with a phototrophic green/purple Zygogonium microbial mat community that inhabits low-temperature regions of acidic (pHMethylmercury enters an aquatic food web through acidophilic microbial mats in Yellowstone National in concentra- tion through all trophic levels of the aquatic food chain. A consequence of this phenomenon

Tomberlin, Jeff

226

Nutrition Content of Food and Beverage Products on Web Sites Popular With Children  

PubMed Central

We assessed the nutritional quality of branded food and beverage products advertised on 28 Web sites popular with children. Of the 77 advertised products for which nutritional information was available, 49 met Institute of Medicine criteria for foods to avoid, 23 met criteria for foods to neither avoid nor encourage, and 5 met criteria for foods to encourage. There is a need for further research on the nature and extent of food and beverage advertising online to aid policymakers as they assess the impact of this marketing on children. PMID:19443816

Lingas, Elena O.; Bukofzer, Eliana

2009-01-01

227

Phylogeny determines the role of helminth parasites in intertidal food webs.  

PubMed

1. Parasites affect interactions among species in food webs and should be considered in any analysis of the structure, dynamics or resilience of trophic networks. 2. However, the roles of individual parasite species, such as their importance as connectors within the network, and what factors determine these roles, are yet to be investigated. Here, we test the hypotheses that the species roles of trematode, cestode and nematode parasites in aquatic food webs are influenced by the type of definitive host they use, and also determined by their phylogenetic affiliations. 3. We quantified the network role of 189 helminth species from six highly resolved intertidal food webs. We focused on four measures of centrality (node degree, closeness centrality, betweenness centrality and eigenvalue centrality), which characterize each parasite's position within the web, and on relative connectedness of a parasite species to taxa in its own module vs. other modules of the web (within-module degree and participation coefficient). 4. All six food webs displayed a significant modular structure, that is, they consisted of subsets of species interacting mostly with each other and less with species from other subsets. We demonstrated that the parasites themselves are not generating this modularity, though they contribute to intermodule connectivity. 5. Mixed-effects models revealed only a modest influence of the type of definitive host used (bird or fish) and of the web of origin on the different measures of parasite species roles. In contrast, the taxonomic affiliations of the parasites, included in the models as nested random factors, accounted for 37-93% of the total variance, depending on the measure of species role. 6. Our findings indicate that parasites are important intermodule connectors and thus contribute to web cohesion. We also uncover a very strong phylogenetic signal in parasite species roles, suggesting that the role of any parasite species in a food web, including new invasive species, is to some extent predictable based solely on its taxonomic affiliations. PMID:23800281

Poulin, Robert; Krasnov, Boris R; Pilosof, Shai; Thieltges, David W

2013-11-01

228

Cycling Through the Food Web: Let's Go on a Research Cruise  

NSDL National Science Digital Library

This site presents an account of a research cruise to investigate how the food webs in different oceanic habitats vary. The scientists wanted to see ocean life in its natural environment and conduct experiments that would not be possible in the laboratory. They looked specifically at three types of ocean habitat: the open ocean, the continental shelf, and an upwelling area. The researchers were hoping to learn the answers to two questions: 'How well do the actual marine food webs match our food chain models for the three habitats?' and 'How does the microbial community in each food web change with depth?'. Students can follow their research and fill out an activity and question checklist as they go along. There is also a page of information for teachers.

2007-12-12

229

Parameter uncertainty, sensitivity, and sediment coupling in bioenergetics-based food web models  

SciTech Connect

A bioenergetics-based food web model was developed and calibrated using measured PCB water and sediment concentrations in two Great Lakes food webs: Green Bay, Michigan and Lake Ontario. The model incorporated functional based trophic levels and sediment, water, and food chain exposures of PCBs to aquatic biota. Sensitivity analysis indicated the parameters with the greatest influence on PCBs in top predators were lipid content of plankton and benthos, planktivore assimilation efficiency, Kow, prey selection, and ambient temperature. Sediment-associated PCBs were estimated to contribute over 90% of PCBs in benthivores and less than 50% in piscivores. Ranges of PCB concentrations in top predators estimated by Monte Carlo simulation incorporating parameter uncertainty were within one order of magnitude of modal values. Model applications include estimation of exceedences of human and ecological thresholds. The results indicate that point estimates from bioenergetics-based food web models have substantial uncertainty that should be considered in regulatory and scientific applications.

Barron, M.G.; Cacela, D.; Beltman, D. [Hagler Bailly, Boulder, CO (United States)

1995-12-31

230

Mercury and other trace elements in a pelagic Arctic marine food web (Northwater Polynya, Baffin Bay).  

PubMed

Total mercury (THg), methylmercury (MeHg) and 22 other trace elements were measured in ice algae, three species of zooplankton, mixed zooplankton samples, Arctic cod (Boreogadus saida), ringed seals (Phoca hispida) and eight species of seabirds to examine the trophodynamics of these metals in an Arctic marine food web. All samples were collected in 1998 in the Northwater Polynya (NOW) located between Ellesmere Island and Greenland in Baffin Bay. THg and MeHg were found to biomagnify through the NOW food web, based on significant positive relationships between log THg and log MeHg concentrations vs. delta15N muscle and liver . The slope of these relationships for muscle THg and MeHg concentrations (slope=0.197 and 0.223, respectively) were similar to those reported for other aquatic food webs. The food web behavior of THg and delta15N appears constant, regardless of trophic state (eutrophic vs. oligotrophic), latitude (Arctic vs. tropical) or salinity (marine vs. freshwater) of the ecosystem. Rb in both liver and muscle tissue and Zn in muscle tissue were also found to biomagnify through this food web, although at a rate that is approximately 25% of that of THg. A number of elements (Cd, Pb and Ni in muscle tissue and Cd and Li in seabird liver tissue) were found to decrease trophically through the food web, as indicated by significantly negative relationships with tissue-specific delta15N. A diverse group of metals (Ag, Ba, La, Li, Sb, Sr, U and V) were found to have higher concentrations in zooplankton than seabirds or marine mammals due to bioconcentration from seawater. The remaining metals (As, Co, Cu, Ga, Mn, Mo and Se in muscle tissue) showed no relationship with trophic position, as indicated by delta15N values, although As in liver tissue showed significant biomagnification in the seabird portion of the food web. PMID:16061271

Campbell, Linda M; Norstrom, Ross J; Hobson, Keith A; Muir, Derek C G; Backus, Sean; Fisk, Aaron T

2005-12-01

231

Defining ecospace of Arctic marine food webs using a novel quantitative approach  

NASA Astrophysics Data System (ADS)

The Arctic is currently facing unprecedented change with developmental, physical and climatological changes. Food webs within the marine Arctic environment are highly susceptible to anthropogenic stressors and have thus far been understudied. Stable isotopes, in conjunction with a novel set of metrics, may provide a framework that allows us to understand which areas of the Arctic are most vulnerable to change. The objective of this study was to use linear distance metrics applied to stable isotopes to a) define and quantify four Arctic marine food webs in ecospace; b) enable quantifiable comparisons among the four food webs and with other ecosystems; and, c) evaluate vulnerability of the four food webs to anthropogenic stressors such as climate change. The areas studied were Hudson Bay, Beaufort Sea, Lancaster Sound and North Water Polynya. Each region was selected based on the abundance of previous research and published and available stable isotope data in peer-review literature. We selected species to cover trophic levels ranging from particulate matter to polar bears with consideration of pelagic, benthic and ice-associated energy pathways. We interpret higher diversity in baseline carbon energy as signifying higher stability in food web structure. Based on this, the Beaufort Sea food web had the highest stability; the Beaufort Sea food web occupied the largest isotopic niche space and was supported by multiple carbon sources. Areas with top-down control system, such as Lancaster Sound and North Water Polynya, would be the first to experience an increase in trophic redundancy and possible hardships from external stressors, as they have fewer basal carbon sources and greater numbers of mid-high level consumers. We conclude that a diverse carbon energy based ecosystem such as the Beaufort Sea and Hudson Bay regions are more resilient to change than a top down control system.

Gale, M.; Loseto, L. L.

2011-12-01

232

Isotopic evidence for the spatial heterogeneity of the planktonic food webs in the transition zone between river and lake ecosystems  

PubMed Central

Resources and organisms in food webs are distributed patchily. The spatial structure of food webs is important and critical to understanding their overall structure. However, there is little available information about the small-scale spatial structure of food webs. We investigated the spatial structure of food webs in a lake ecosystem at the littoral transition zone between an inflowing river and a lake. We measured the carbon isotope ratios of zooplankton and particulate organic matter (POM; predominantly phytoplankton) in the littoral zone of a saline lake. Parallel changes in the ? 13C values of zooplankton and their respective POMs indicated that there is spatial heterogeneity of the food web in this study area. Lake ecosystems are usually classified at the landscape level as either pelagic or littoral habitats. However, we showed small-scale spatial heterogeneity among planktonic food webs along an environmental gradient. Stable isotope data is useful for detecting spatial heterogeneity of habitats, populations, communities, and ecosystems. PMID:24392286

Zuykova, Elena I.; Shikano, Shuichi; Kikuchi, Eisuke; Ota, Hiroshi; Yurlova, Natalia I.; Yadrenkina, Elena

2013-01-01

233

Species richness and trophic diversity increase decomposition in a co-evolved food web.  

PubMed

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

Baiser, Benjamin; Ardeshiri, Roxanne S; Ellison, Aaron M

2011-01-01

234

The cesium:potassium index of food web structure -- A complementary approach to stable isotope indicators  

SciTech Connect

Stable isotope shifts with trophic or average feeding level are an important tool in characterizing sampled food webs for biomagnification and other studies. However, spatial and temporal variations in isotope ratios in the environment can introduce uncertainties in interpreting such data. An elemental index, the Cs/K ratio, has proved to be a useful tool in assessing the reliability of the trophic level approach to characterizing marine and estuarine food webs. A major advantage is the constant value of this elemental ratio in seawater. Studies conducted over the last three decades in a variety of aquatic ecosystems generally have yielded consistent results using the Cs/K Index. The mean Trophic Transfer Factor obtained from twelve food web surveys was 2.0 +/- 0.1 (SE), indicating substantial structure for most of the food webs sampled. An empirical technique, termed the Exponential Biomagnification Model, was developed to simplify the observed variation of Cs/K with Trophic Level Assignment. This approach has proved useful in assessing sampled food webs with non-integer Trophic Level Assignments, and obtaining average Trophic Transfer Factors for the Cs/K ratio and corresponding tissue concentrations of environmental contaminants.

Young, D. [Environmental Protection Agency, Newport, OR (United States)

1995-12-31

235

Linking Water Quality and Quantity in Environmental Flow Assessment in Deteriorated Ecosystems: A Food Web View  

PubMed Central

Most rivers worldwide are highly regulated by anthropogenic activities through flow regulation and water pollution. Environmental flow regulation is used to reduce the effects of anthropogenic activities on aquatic ecosystems. Formulating flow alteration–ecological response relationships is a key factor in environmental flow assessment. Traditional environmental flow models are characterized by natural relationships between flow regimes and ecosystem factors. However, food webs are often altered from natural states, which disturb environmental flow assessment in such ecosystems. In ecosystems deteriorated by heavy anthropogenic activities, the effects of environmental flow regulation on species are difficult to assess with current modeling approaches. Environmental flow management compels the development of tools that link flow regimes and food webs in an ecosystem. Food web approaches are more suitable for the task because they are more adaptive for disordered multiple species in a food web deteriorated by anthropogenic activities. This paper presents a global method of environmental flow assessment in deteriorated aquatic ecosystems. Linkages between flow regimes and food web dynamics are modeled by incorporating multiple species into an ecosystem to explore ecosystem-based environmental flow management. The approach allows scientists and water resources managers to analyze environmental flows in deteriorated ecosystems in an ecosystem-based way. PMID:23894669

Chen, He; Ma, Lekuan; Guo, Wei; Yang, Ying; Guo, Tong; Feng, Cheng

2013-01-01

236

Soil food web properties explain ecosystem services across European land use systems.  

PubMed

Intensive land use reduces the diversity and abundance of many soil biota, with consequences for the processes that they govern and the ecosystem services that these processes underpin. Relationships between soil biota and ecosystem processes have mostly been found in laboratory experiments and rarely are found in the field. Here, we quantified, across four countries of contrasting climatic and soil conditions in Europe, how differences in soil food web composition resulting from land use systems (intensive wheat rotation, extensive rotation, and permanent grassland) influence the functioning of soils and the ecosystem services that they deliver. Intensive wheat rotation consistently reduced the biomass of all components of the soil food web across all countries. Soil food web properties strongly and consistently predicted processes of C and N cycling across land use systems and geographic locations, and they were a better predictor of these processes than land use. Processes of carbon loss increased with soil food web properties that correlated with soil C content, such as earthworm biomass and fungal/bacterial energy channel ratio, and were greatest in permanent grassland. In contrast, processes of N cycling were explained by soil food web properties independent of land use, such as arbuscular mycorrhizal fungi and bacterial channel biomass. Our quantification of the contribution of soil organisms to processes of C and N cycling across land use systems and geographic locations shows that soil biota need to be included in C and N cycling models and highlights the need to map and conserve soil biodiversity across the world. PMID:23940339

de Vries, Franciska T; Thébault, Elisa; Liiri, Mira; Birkhofer, Klaus; Tsiafouli, Maria A; Bjørnlund, Lisa; Bracht Jørgensen, Helene; Brady, Mark Vincent; Christensen, Søren; de Ruiter, Peter C; d'Hertefeldt, Tina; Frouz, Jan; Hedlund, Katarina; Hemerik, Lia; Hol, W H Gera; Hotes, Stefan; Mortimer, Simon R; Setälä, Heikki; Sgardelis, Stefanos P; Uteseny, Karoline; van der Putten, Wim H; Wolters, Volkmar; Bardgett, Richard D

2013-08-27

237

A Circadian Clock in Antarctic Krill: An Endogenous Timing System Governs Metabolic Output Rhythms in the Euphausid Species Euphausia superba  

Microsoft Academic Search

Antarctic krill, Euphausia superba, shapes the structure of the Southern Ocean ecosystem. Its central position in the food web, the ongoing environmental changes due to climatic warming, and increasing commercial interest on this species emphasize the urgency of understanding the adaptability of krill to its environment. Krill has evolved rhythmic physiological and behavioral functions which are synchronized with the daily

Mathias Teschke; Sabrina Wendt; So Kawaguchi; Achim Kramer; Bettina Meyer; Michael N. Nitabach

2011-01-01

238

Hydrological and Biogeochemical Controls on Seasonal and Spatial Differences in Food Webs in the Everglades  

NASA Astrophysics Data System (ADS)

Stable isotopes can be used to determine the relative trophic positions of biota within a food web, and to improve our understanding of the biomagnification of contaminants. Plants at the base of the food web uptake dissolved organic carbon (DIC) and nitrogen (DIN) for growth, and their tissue reflects the isotopic composition of these sources. Animals then mirror the isotopic composition of the primary producers, as modified by consumer-diet fractionations at successive trophic steps. During 1995-99, we collected algae, macrophyte, invertebrate, and fish samples from 15 USGS sites in the Everglades and analyzed them for d13C and d15N with the goal of characterizing seasonal and spatial differences in food web relations. Carbon isotopes effectively distinguish between two main types of food webs: ones where algae is the dominant base of the food web, which are characteristic of relatively pristine marsh sites with long hydroperiods, and ones where macrophyte debris appears to be a significant source of nutrients, which are apparently characteristic of shorter hydroperiod sites, and nutrient-impacted marshes and canals. There usually is an inverse relation between d13C and d15N of organisms over time, especially in more pristine environments, reflecting seasonal changes in the d13C of DIC and the d15N of DIN. The d13C and d15N of algae also show strong positive correlations with seasonal changes in water levels. This variability is substantially damped up the food chain, probably because of the longer integration times of animals vs. plants. We speculate that these seasonal shifts in water level result in changes in biogeochemical reactions and nutrient levels, with corresponding variations in the d15N and d13C of biota. For example, small changes in water level may change the balance of photosynthesis, bacterial respiration, and atmospheric exchange reactions that control the d13C of DIC. Such changes will probably also affect the d15N of dissolved inorganic N (DIN) because of corresponding changes in N uptake and redox conditions. During the dry season, the marshes probably become more anoxic because of shallower water levels, less photosynthesis, and increased quantities of decaying vegetation. During this season, macrophyte debris appears to be a significant source of nutrients to local food webs. Our isotope data are consistent with seasonal differences in food webs, related to seasonal differences in water levels. Hence, biota isotopes provide a powerful tool for monitoring how future ecosystem changes, in particular changes in hydroperiod, will affect food webs across the Everglades.

Kendall, C.; Wankel, S. D.; Bemis, B. E.; Rawlik, P. S.; Krabbenhoft, D. P.; Lange, T.

2002-05-01

239

Seasonal variation in mercury and food web biomagnification in Lake Ontario, Canada.  

PubMed

Seasonal variation in mercury (Hg) concentrations and food web structure was assessed for eastern Lake Ontario. Hg concentrations, measured in 6 species of invertebrates and 8 species of fishes, tended to be highest in the spring and lowest in the summer for most biota. Yellow perch (Perca flavescens) exhibited significant ontogenetic shifts in diet and Hg, although such patterns were not evident for other species. Food web structure, as indicated by stable isotope values (?(15)N, ?(13)C) was not static. Log-transformed Hg data were strongly and consistently correlated with ?(15)N values for the whole food web in each of the three seasons (slopes, 0.17-0.24) and across the entire year (slope, 0.2). While significantly different between seasons, the regression slope values are still consistent with published global Hg biomagnification rates. Our results indicate that the assessment of Hg trends in Great Lakes must take into account seasonal patterns and time of sampling. PMID:22230083

Zhang, Liang; Campbell, Linda M; Johnson, Timothy B

2012-02-01

240

Indicator species for limited budgets: Profiles of trophic levels, food web placement, and ecotoxicological sensitivity  

SciTech Connect

The identification of indicator and/or keystone species is directly related to the success of a quantitative Ecological Risk Assessment (ERA) at a hazardous waste site. In a fiscally perfect world, species would be selected to represent each and every trophic level within the aquatic and/or terrestrial food web. However, because limited budgets are the norm, scientifically valid ``shortcuts`` are in high demand. LAW has conducted quantitative ERAs at more than thirty hazardous waste sites, with as many as ten indicator species per site (selected to represent trophic levels within each habitat type present). Data from these assessments have been compiled and evaluated for the purpose of identifying species which demonstrate the highest toxicological sensitivity within the food web. Budgets can be reduced by incorporating this proposed quantitative screening-level ERA approach. This presentation will specify quantitative ERA methodology, ecotoxicological extrapolations, uncertainties to consider, trophic level profiles, food web placement, and indicator species sensitivity.

Sorenson, M.T.; Margolin, J.A.

1995-12-31

241

Topographically driven predictions for river food webs: responses to land cover and climate change  

NASA Astrophysics Data System (ADS)

Fluxes of materials and energy, as well as the performances and interactions of organisms in food webs are strongly influenced by topography and vegetation. We have been using a "predictive mapping" approach to investigate how resource fluxes and food web interactions change down the Eel River drainage network in Northwestern California. In this talk, I will focus on hydrologic and food web controls on the production and fate of dominant primary producers in the river (macroalgae, diatoms and cyanobacteria). Algal mediated processes (e.g. nitrogen-fixation) and processes that limit algal abundance (e.g. grazer control) change abruptly through the season and down drainage networks. Field surveys and mensurative experiments that map the drainage network positions of these changes, and manipulative field experiments that uncover their causes, set the stage for predictive mapping, which is necessary if not sufficient for forecasts of river ecosystem response to changes in climate, land use, or biota.

Power, M. E.; Dietrich, W. E.; Finlay, J. C.; Bode, C. A.; Hondzo, M.; Limm, M.; National CenterEarth Surface Dynamics

2011-12-01

242

From the Top of the World...to the Bottom of the Food Web  

NSDL National Science Digital Library

Four teaching units show how NASA satellites measure ocean productivity. Topics cover: marine food web from producers to consumers and decomposers; phytoplankton diversity, classification and adaptations; studying photosynthesis with technology, from microscopes to satellites; and biology of algal blooms. Units include: background, lesson plans using on-line data or instructions for classroom and field activities; web links for further study. Lessons are aligned to teaching standards from McREL. Order educational CD-ROM, Phytopia. DLESE and Homeschool featured site.

243

Impacts of food web structure and feeding behavior on mercury exposure in Greenland Sharks (Somniosus microcephalus).  

PubMed

Benthic and pelagic food web components in Cumberland Sound, Canada were explored as sources of total mercury (THg) to Greenland Sharks (Somniosus microcephalus) via both bottom-up food web transfer and top-down shark feeding behavior. Log10THg increased significantly with ?(15)N and trophic position from invertebrates (0.01±0.01?g·g(-1) [113±1ng·g(-1)] dw in copepods) to Greenland Sharks (3.54±1.02?g·g(-1)). The slope of the log10THg vs. ?(15)N linear regression was higher for pelagic compared to benthic food web components (excluding Greenland Sharks, which could not be assigned to either food web), which resulted from THg concentrations being higher at the base of the benthic food web (i.e., in benthic than pelagic primary consumers). However, feeding habitat is unlikely to consistently influence shark THg exposure in Cumberland Sound because THg concentrations did not consistently differ between benthic and pelagic shark prey. Further, size, gender and feeding behavior (inferred from stable isotopes and fatty acids) were unable to significantly explain THg variability among individual Greenland Sharks. Possible reasons for this result include: 1) individual sharks feeding as generalists, 2) high overlap in THg among shark prey, and 3) differences in turnover time between ecological tracers and THg. This first assessment of Greenland Shark THg within an Arctic food web revealed high concentrations consistent with biomagnification, but low ability to explain intra-specific THg variability. Our findings of high THg levels and consumption of multiple prey types, however, suggest that Greenland Sharks acquire THg through a variety of trophic pathways and are a significant contributor to the total biotic THg pool in northern seas. PMID:24630590

McMeans, Bailey C; Arts, Michael T; Fisk, Aaron T

2015-03-15

244

Parasites Affect Food Web Structure Primarily through Increased Diversity and Complexity  

PubMed Central

Comparative research on food web structure has revealed generalities in trophic organization, produced simple models, and allowed assessment of robustness to species loss. These studies have mostly focused on free-living species. Recent research has suggested that inclusion of parasites alters structure. We assess whether such changes in network structure result from unique roles and traits of parasites or from changes to diversity and complexity. We analyzed seven highly resolved food webs that include metazoan parasite data. Our analyses show that adding parasites usually increases link density and connectance (simple measures of complexity), particularly when including concomitant links (links from predators to parasites of their prey). However, we clarify prior claims that parasites “dominate” food web links. Although parasites can be involved in a majority of links, in most cases classic predation links outnumber classic parasitism links. Regarding network structure, observed changes in degree distributions, 14 commonly studied metrics, and link probabilities are consistent with scale-dependent changes in structure associated with changes in diversity and complexity. Parasite and free-living species thus have similar effects on these aspects of structure. However, two changes point to unique roles of parasites. First, adding parasites and concomitant links strongly alters the frequency of most motifs of interactions among three taxa, reflecting parasites' roles as resources for predators of their hosts, driven by trophic intimacy with their hosts. Second, compared to free-living consumers, many parasites' feeding niches appear broader and less contiguous, which may reflect complex life cycles and small body sizes. This study provides new insights about generic versus unique impacts of parasites on food web structure, extends the generality of food web theory, gives a more rigorous framework for assessing the impact of any species on trophic organization, identifies limitations of current food web models, and provides direction for future structural and dynamical models. PMID:23776404

Dunne, Jennifer A.; Lafferty, Kevin D.; Dobson, Andrew P.; Hechinger, Ryan F.; Kuris, Armand M.; Martinez, Neo D.; McLaughlin, John P.; Mouritsen, Kim N.; Poulin, Robert; Reise, Karsten; Stouffer, Daniel B.; Thieltges, David W.; Williams, Richard J.; Zander, Claus Dieter

2013-01-01

245

Parasites affect food web structure primarily through increased diversity and complexity  

USGS Publications Warehouse

Comparative research on food web structure has revealed generalities in trophic organization, produced simple models, and allowed assessment of robustness to species loss. These studies have mostly focused on free-living species. Recent research has suggested that inclusion of parasites alters structure. We assess whether such changes in network structure result from unique roles and traits of parasites or from changes to diversity and complexity. We analyzed seven highly resolved food webs that include metazoan parasite data. Our analyses show that adding parasites usually increases link density and connectance (simple measures of complexity), particularly when including concomitant links (links from predators to parasites of their prey). However, we clarify prior claims that parasites ‘‘dominate’’ food web links. Although parasites can be involved in a majority of links, in most cases classic predation links outnumber classic parasitism links. Regarding network structure, observed changes in degree distributions, 14 commonly studied metrics, and link probabilities are consistent with scale-dependent changes in structure associated with changes in diversity and complexity. Parasite and free-living species thus have similar effects on these aspects of structure. However, two changes point to unique roles of parasites. First, adding parasites and concomitant links strongly alters the frequency of most motifs of interactions among three taxa, reflecting parasites’ roles as resources for predators of their hosts, driven by trophic intimacy with their hosts. Second, compared to free-living consumers, many parasites’ feeding niches appear broader and less contiguous, which may reflect complex life cycles and small body sizes. This study provides new insights about generic versus unique impacts of parasites on food web structure, extends the generality of food web theory, gives a more rigorous framework for assessing the impact of any species on trophic organization, identifies limitations of current food web models, and provides direction for future structural and dynamical models.

Dunne, Jennifer A.; Lafferty, Kevin D.; Dobson, Andrew P.; Hechinger, Ryan F.; Kuris, Armand M.; Martinez, Neo D.; McLaughlin, John P.; Mouritsen, Kim N.; Poulin, Robert; Reise, Karsten; Stouffer, Daniel B.; Thieltges, David W.; Williams, Richard J.; Zander, Claus Dieter

2013-01-01

246

Effects of lake acidification and recovery on the stability of zooplankton food webs  

SciTech Connect

The effect of food web structure on community stability and resilience has rarely been examined using empirical data. Yet there is a practical application for such studies insofar as resistance stability determines the ability of a system to adsorb' anthropogenic stress and adjustment stability determines the reversibility of resulting damage. The stability of zooplankton food webs in 46 Precambrian Shield lakes was examined using data collected in the 1970s, when pH ranged from 3.8 to 7.0, and in 1990, when pH had increased by up to two units in some lakes. Acidification overcame resistance stability at pH <5.0, as evidenced by decreases in species richness, numbers of predatory and competitive links, directed connectance, predator generalization, and linkage density, identified by analysis of variance. Adjustment stability was demonstrated by changes in food web attributes in lakes with higher pH in 1990 than in the 1970s. Species richness, numbers of predatory and competitive links, linkage density, and predator generalization all increased relative to the 1970s values. Food web attributes of recovering' lakes were statistically indistinguishable from those of lakes of similar pH that had not been more acidic in the 1970s. Similar trajectors of food web change were followed during environmental degradation and recovery. Planktonic food webs of anthropogenically acidified lakes may eventually recover to resemble their pre-acidification condition, given sufficient time without acidic inputs. Whether adjustment stability is a general feature of anthropogenically stressed systems remains to be determined. 42 refs., 2 figs., 4 tabs.

Locke, A. (Gulf Fisheries Centre, Moncton, News Brunswick (Canada)); Sprules, W.G. (Univ. of Toronto, Ontario (Canada))

1994-03-01

247

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

PubMed

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

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

2014-06-01

248

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

PubMed Central

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

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

2014-01-01

249

A non-equilibrium model for predicting bioaccumulation of organic contaminants in aquatic food-webs  

SciTech Connect

A sub-model describing bioaccumulation and biomagnification in benthic invertebrates was incorporated into a steady-state food-web model (Gobas, 1993) was modified, to estimate concentrations of organic contaminants in aquatic organisms based on chemical concentrations in water and sediments. Model predictions were in good agreement with field data when applied to western Lake Erie. The improved ability of the model to simulate bioaccumulation by benthic invertebrates, makes this model particularly useful for quantifying contaminant transfer in the benthic food-web.

Morrison, H.; Lazar, R.; Haffner, G.D. [Univ. of Windsor, Ontario (Canada). Dept. of Biological Sciences; Whittle, D.M. [Dept. of Fisheries and Oceans, Burlington, Ontario (Canada). Ecotoxicology Div.; Gobas, F.A.P.C. [Simon Fraser Univ., Burnaby, British Columbia (Canada)

1995-12-31

250

The Serengeti food web: empirical quantification and analysis of topological changes under increasing human impact.  

PubMed

1.?To address effects of land use and human overexploitation on wildlife populations, it is essential to better understand how human activities have changed species composition, diversity and functioning. Theoretical studies modelled how network properties change under human-induced, non-random species loss. However, we lack data on realistic species-loss sequences in threatened, real-world food webs to parameterize these models. 2.?Here, we present a first size-structured topological food web of one of the most pristine terrestrial ecosystems in the world, the Serengeti ecosystem (Tanzania). The food web consists of 95 grouped nodes and includes both invertebrates and vertebrates ranging from body masses between 10(-7) and 10(4) kg. 3.?We study the topological changes in this food web that result from the simulated IUCN-based species-loss sequence representing current species vulnerability to human disturbances in and around this savanna ecosystem. We then compare this realistic extinction scenario with other extinction sequences based on body size and connectance and perform an analysis of robustness of this savanna food web. 4.?We demonstrate that real-world species loss in this case starts with the biggest (mega) herbivores and top predators, causing higher predator-prey mass ratios. However, unlike theoretically modelled linear species deletion sequences, this causes poor-connected species to be lost first, while more highly connected species become lost as human impact progresses. This food web shows high robustness to decreasing body size and increasing connectance deletion sequences compared with a high sensitivity to the decreasing connectance deletion scenario. 5.?Furthermore, based on the current knowledge of the Serengeti ecosystem, we discuss how the focus on food web topology alone, disregarding nontrophic interactions, may lead to an underestimation of human impacts on wildlife communities, with the number of trophic links affected by a factor of two. 6.?This study underlines the importance of integrative efforts between the development of food web theory and basic field work approaches in the quantification of the structure of interaction networks to sustain natural ecosystems in a changing world. PMID:21155772

de Visser, Sara N; Freymann, Bernd P; Olff, Han

2011-03-01

251

The National Food Safety Database Web Site: Irradiation  

NSDL National Science Digital Library

The National Food Safety Database, a cooperative project of the United States Department of Agriculture and several universities, provides a section on food irradiation that discusses the process, the history of irradiation, and its relationship to food safety, among other features. It is highlighted by a 39-part, annotated slide show that supports the process. Previously approved for use on poultry and fruits and vegetables in the US, irradiation can kill disease-causing bacteria like Salmonella and Escherichia coli 0157:H7 (discussed in the Scout Report for Science and Engineering's In the News section, September 17, 1997), and molds and funguses that cause rot. With recent US Food and Drug Administration (FDA) approval, irradiation can now be used to process red meat (e.g., beef, pork, lamb, and byproducts). The process involves exposing food to a source of radiation such as gamma rays from radioactive cobalt 60, cesium 137, or x-rays. No radioactive material is added to the product, and the technique is routinely used on grains and spices, as well as for sterilizing disposable medical devices. In spite of a number of tests conducted over the last 30 years substantiating its safety, irradiation has not gained widespread public acceptance in the US. This is largely due to the public's general fear of processes utilizing radiation. Supporters of the technology claim that it will virtually eliminate food-borne illness in the US, while skeptics feel that technology such as steam treatment can accomplish adequate sterilization without the purported risks and public concern associated with irradiation. (8) The National Food Safety Database, a cooperative project of the United States Department of Agriculture and several universities, provides a section on food irradiation that discusses the process, history of irradiation, and its relationship to food safety, among other features. It features a 39-part, annotated slide show that strongly supports the process.

252

Food web pathway determines how selenium affects aquatic ecosystems: A San francisco Bay case study  

USGS Publications Warehouse

Chemical contaminants disrupt ecosystems, but specific effects may be under-appreciated when poorly known processes such as uptake mechanisms, uptake via diet, food preferences, and food web dynamics are influential. Here we show that a combination of food web structure and the physiology of trace element accumulation explain why some species in San Francisco Bay are threatened by a relatively low level of selenium contamination and some are not. Bivalves and crustacean Zooplankton form the base of two dominant food webs in estuaries. The dominant bivalve Potamocorbula amurensis has a 10-fold slower rate constant of loss for selenium than do common crustaceans such as copepods and the mysid Neomysis mercedis (rate constant of loss, ke = 0.025, 0.155, and 0.25 d-1, respectively). The result is much higher selenium concentrations in the bivalve than in the crustaceans. Stable isotope analyses show that this difference is propagated up the respective food webs in San Francisco Bay. Several predators of bivalves have tissue concentrations of selenium that exceed thresholds thought to be associated with teratogenesis or reproductive failure (liver Se > 15 ??g g-1 dry weight). Deformities typical of selenium-induced teratogenesis were observed in one of these species. Concentrations of selenium in tissues of predators of Zooplankton are less than the thresholds. Basic physiological and ecological processes can drive wide differences in exposure and effects among species, but such processes are rarely considered in traditional evaluations of contaminant impacts.

Stewart, A.R.; Luoma, S.N.; Schlekat, C.E.; Doblin, M.A.; Hieb, K.A.

2004-01-01

253

Ecological Processes Driving Trophic Transfer Of Metals In Aquatic Food Webs  

NASA Astrophysics Data System (ADS)

The transfer of metals in aquatic food webs from water to fish varies among lakes and metals. It is influenced by four ecological processes: biomagnification, biodiminution, biodilution (decreasing mass specific concentrations with increased biomass), and transfer by keystone conduit species. Data from three different field studies will be used to discuss the fate of Hg, Zn, As, and Pb in food webs typical of lakes throughout the northeast US. Metal concentrations were measured in the water, particulates, two size fractions of zooplankton, and in fish in a broad gradient of lakes and were related to ecological, physico-chemical and land use variables. Some metals biomagnified (Hg, Zn) while others biodiminished (As, Pb). Hg and Zn in zooplankton and fish were also correlated suggesting food is an important source of bioaccumulation. Both plankton abundance and species composition influenced the trophic transfer of metals, particularly Hg, to fish. Specifically, Hg concentrations in both zooplankton and fish were lower in lakes with higher plankton biomass. Moreover, Hg and As bioaccumulation was greater in cladocerans than copepods suggesting that cladocerans are major metal conduits in food webs. These results underscore the importance of biological interactions to trophic transfer of metals in aquatic food webs.

Chen, C. Y.; Folt, C. L.

2004-05-01

254

Role of detritus in a spatial food web model with diffusion  

NASA Astrophysics Data System (ADS)

One of the central themes in modern ecology is the enduring debate on whether there is a relationship between the complexity of a biological community and its stability. In this paper, we focus on the role of detritus and spatial dispersion on the stability of ecosystems. Using Monte Carlo simulations we analyze two three-level models of food webs: a grazing one with the basal species (i.e., primary producers) having unlimited food resources and a detrital one in which the basal species uses detritus as a food resource. While the vast majority of theoretical studies neglects detritus, from our results it follows that the detrital food web is more stable than its grazing counterpart, because the interactions mediated by detritus damp out fluctuations in species' densities. Since the detritus model is the more complex one in terms of interaction patterns, our results provide evidence for the advocates of the complexity as one of the factors enhancing stability of ecosystems.

Pekalski, Andrzej; Szwabi?ski, Janusz

2014-05-01

255

Sardine cycles, krill declines, and locust plagues: revisiting 'wasp-waist' food webs.  

PubMed

'Wasp-waist' systems are dominated by a mid trophic-level species that is thought to exert top-down control on its food and bottom-up control on its predators. Sardines, anchovy, and Antarctic krill are suggested examples, and here we use locusts to explore whether the wasp-waist concept also applies on land. These examples also display the traits of mobile aggregations and dietary diversity, which help to reduce the foraging footprint from their large, localised biomasses. This suggests that top-down control on their food operates at local aggregation scales and not at wider scales suggested by the original definition of wasp-waist. With this modification, the wasp-waist framework can cross-fertilise marine and terrestrial approaches, revealing how seemingly disparate but economically important systems operate. PMID:24755099

Atkinson, Angus; Hill, Simeon L; Barange, Manuel; Pakhomov, Evgeny A; Raubenheimer, David; Schmidt, Katrin; Simpson, Stephen J; Reiss, Christian

2014-06-01

256

Do Stable Isotopes Reflect the Food Web Development in Regenerating Ecosystems?  

Microsoft Academic Search

We evaluated the use of ?N- and ?C-values to monitor the development of food web complexity and biodiversity in a regenerating ecosystem. Therefore a model food chain was established feeding cultivated woodlice (Porcellio dilatatus) on a cellulolytic fungus (Chaetomium globosum) grown on cellulose paper. Two diets of different quality (C:N ratios of 54 vs. 200) with different ?N- (1.3‰ vs.

J. Rothe; G. Gleixner

2000-01-01

257

Bioaccumulation and biomagnification of polybrominated diphenyl ethers in a food web of Lake Michigan  

Microsoft Academic Search

Polybrominated diphenyl ethers are hydrophobic chemicals and can biomagnify in food chains. Little is known about the biomagnification\\u000a of PBDEs in the Lake Michigan food web. Plankton, Diporeia, lake whitefish, lake trout, and Chinook salmon were collected from Lake Michigan in 2006 between April and August. Fish\\u000a liver and muscle and whole invertebrates were analyzed for six PBDEs (BDE-47, 99,

Yin-Ming Kuo; Maria S. Sepúlveda; Inez Hua; Hugo G. Ochoa-Acuña; Trent M. Sutton

2010-01-01

258

FOOD WEB CHAOS WITHOUT SUBCHAIN OSCILLATORS BRIAN BOCKELMAN & BO DENG  

E-print Network

- petition Exclusion Principle ([16, 2, 31, 18]), which states that for most systems where two predators feed on a prey there cannot be any stable coexisting state. This principle has recently been shown not to hold not apply to such a 3-species competitive web mediated by an addi- tional super-predator as shown in [1

Logan, David

259

Distribution of Phthalate Esters in a Marine Aquatic Food Web  

E-print Network

equivalent concentrations of the high-molecular-weight DPEs (i.e., C8-C10 DPEs: di(2-ethylhexyl), di samples produced a direct comparison of the bioaccumulation behavior of PCBs and DPEs. Lipid equivalent-Web Magnification Factor (FWMF) of the PCB congeners ranged from 1.8 to 9.5. Lipid equivalent concentrations of low

Gobas, Frank

260

Analogous aquatic and terrestrial food webs in the high Arctic: The structuring force of a harsh climate  

Microsoft Academic Search

Understanding food web structure and dynamics remains a central theme in ecology. Whilst differences between aquatic and terrestrial food webs have been the focus of several studies, we aim to reveal similarities where abiotic conditions are particularly extreme such as in the high Arctic. We propose that here, the combination of a short growing season, low temperature and low light,

René van der Wal; Dag O. Hessen

2009-01-01

261

Analyzing pelagic food webs leading to top predators in the Pacific Ocean: A graph-theoretic approach  

E-print Network

Analyzing pelagic food webs leading to top predators in the Pacific Ocean: A graph using graph-theoretic methods, which included aggregating species based on food-web relationships underlines the need for detailed trophic databases to adequately describe regional pelagic ecosystems

Hawai'i at Manoa, University of

262

Comparing Polybrominated Diphenyl Ether and Polychlorinated Biphenyl Bioaccumulation in a Food Web in Grand Traverse Bay, Lake Michigan  

Microsoft Academic Search

Levels of polybrominated diphenyl ethers (BDEs) in Great Lakes salmonids and ambient air have been recently reported, but few studies worldwide have examined the accumulation of BDEs within aquatic food webs. Here we report some of the first measurements of six BDE congeners that are common components of the pentaBDE commercial mixture within an entire Lake Michigan food web. BDEs

H. M. Stapleton; J. E. Baker

2003-01-01

263

The detritus food-web and the diversity of soil fauna as indicators of disturbance regimes in agro-ecosystems  

Microsoft Academic Search

An ongoing study initiated in August 1990 investigated the effects of disturbances (organic mulching, cultivation, herbicides) on the detritus food-web in annual (maize) and perennial (asparagus) cropping systems. In this paper we attempt to simultaneously assess the functional and taxonomic structure of various components of this food-web. Biota in the perennial system was the most responsive to disturbance. The microflora

D. A. Wardle; G. W. Yeates; R. N. Watson; K. S. Nicholson

1995-01-01

264

Seasonal changes of trophic transfer efficiencies in a plankton food web derived from biomass size distributions and network analysis  

Microsoft Academic Search

The trophic transfer efficiencies in the planktonic food web of large, deep, and meso­ eutrophic Lake Constance were derived independently from biomass size distributions and from mass-balanced carbon flow diagrams based on comprehensive data for biomass, production, and food web structure. The main emphasis was on the transfer of primary production to herbivores since this process dominates the flow of

Ursula Gaedke; Dietmar Straile

1994-01-01

265

Towards a mechanistic understanding of temperature and enrichment effects on species interaction strength, omnivory and food-web structure.  

PubMed

Revealing the links between species functional traits, interaction strength and food-web structure is of paramount importance for understanding and predicting the relationships between food-web diversity and stability in a rapidly changing world. However, little is known about the interactive effects of environmental perturbations on individual species, trophic interactions and ecosystem functioning. Here, we combined modelling and laboratory experiments to investigate the effects of warming and enrichment on a terrestrial tritrophic system. We found that the food-web structure is highly variable and switches between exploitative competition and omnivory depending on the effects of temperature and enrichment on foraging behaviour and species interaction strength. Our model contributes to identifying the mechanisms that explain how environmental effects cascade through the food web and influence its topology. We conclude that considering environmental factors and flexible food-web structure is crucial to improve our ability to predict the impacts of global changes on ecosystem diversity and stability. PMID:24751223

Sentis, Arnaud; Hemptinne, Jean-Louis; Brodeur, Jacques

2014-07-01

266

Salmon Life Histories, Habitats, and Food Webs in the Columbia River Estuary  

E-print Network

Salmon Life Histories, Habitats, and Food Webs in the Columbia River Estuary Daniel J. Bottom NOAA management efforts in the Columbia River estuary on behalf of salmon: (1) the estuary is irrelevant to conservation because fresh water conditions limit salmon production; and (2) the estuary is a threat

267

Probabilistic patterns of interaction: the effects of link-strength variability on food web structure  

PubMed Central

Patterns of species interactions affect the dynamics of food webs. An important component of species interactions that is rarely considered with respect to food webs is the strengths of interactions, which may affect both structure and dynamics. In natural systems, these strengths are variable, and can be quantified as probability distributions. We examined how variation in strengths of interactions can be described hierarchically, and how this variation impacts the structure of species interactions in predator–prey networks, both of which are important components of ecological food webs. The stable isotope ratios of predator and prey species may be particularly useful for quantifying this variability, and we show how these data can be used to build probabilistic predator–prey networks. Moreover, the distribution of variation in strengths among interactions can be estimated from a limited number of observations. This distribution informs network structure, especially the key role of dietary specialization, which may be useful for predicting structural properties in systems that are difficult to observe. Finally, using three mammalian predator–prey networks (two African and one Canadian) quantified from stable isotope data, we show that exclusion of link-strength variability results in biased estimates of nestedness and modularity within food webs, whereas the inclusion of body size constraints only marginally increases the predictive accuracy of the isotope-based network. We find that modularity is the consequence of strong link-strengths in both African systems, while nestedness is not significantly present in any of the three predator–prey networks. PMID:22832361

Yeakel, Justin D.; Guimarães, Paulo R.; Novak, Mark; Fox-Dobbs, Kena; Koch, Paul L.

2012-01-01

268

BULLETIN OF MARINE SCIENCE, 73(3): 569591, 2003 PLANKTONIC FOOD WEB DYNAMICS IN TWO  

E-print Network

dominates phytoplankton biomass, a western region heavily influenced by the Gulf of Mexico where diatomsBULLETIN OF MARINE SCIENCE, 73(3): 569­591, 2003 569 PLANKTONIC FOOD WEB DYNAMICS IN TWO approach was used to examine carbon flows and trophic interactions in the planktonic system of two

Jackson, George

269

Molecular detection of trophic links in a complex insect hostparasitoid food web  

E-print Network

caterpillar­parasitoid food web from trop- ical rainforest of Papua New Guinea. We DNA barcoded hosts. Molecular detection proved especially useful in cases where distinguishing host species in caterpillar stage was difficult morphologi- cally, or when the caterpillar died during rearing. We have even detected a case

270

Carp Exclusion, Food-web Interactions, and the Restoration of Cootes Paradise Marsh  

E-print Network

dominated state. INDEX WORDS: Carp exclusion, coastal wetlands, restoration, food web. J. Great Lakes Res. 30(1):44­57 Internat. Assoc. Great Lakes Res., 2004 INTRODUCTION Since the time of European settlement, heavily settled areas of the lower Laurentian Great Lakes basin have lost a large proportion

McMaster University

271

Carp exclusion, food-web interactions and the restoration of Cootes Paradise Marsh.  

E-print Network

-1115 Submitted to: Journal of Great Lakes Research Running title: Carp exclusion, food-web and marsh restoration of European settlement, heavily settled areas of the lower Laurentian Great Lakes' basin have lost a large of nutrients. Many Great Lakes coastal wetlands, which were formerly clear-water, plant- dominated systems

McMaster University

272

Organochlorine compounds in Lake Superior: Chiral polychlorinated biphenyls and biotransformation in the aquatic food web  

USGS Publications Warehouse

The enantiomeric composition of seven chiral PCB congeners was measured in the Lake Superior aquatic food web sampled in 1998, to determine the extent of enantioselective biotransformation in aquatic biota. All chiral PCB congeners studied (CBs 91, 95, 136, 149, 174, 176, and 183) biomagnified in the Lake Superior aquatic food web, based on biomagnification and food web magnification factors greater than unity. PCB atropisomers were racemic in phytoplankton and zooplankton, suggesting no biotransformation potential toward PCBs for these low trophic level organisms. However, Diporeia and mysids had significantly nonracemic residues for most chiral congeners studied. This observation suggests that these macrozooplankton can stereoselectively metabolize chiral congeners. Alternatively, macrozooplankton obtained nonracemic residues from feeding on organic-rich suspended particles and sediments, which would imply that stereoselective microbial PCB biotransformation may be occurring in Lake Superior sediments at PCB concentrations far lower than that previously associated with such activity. Widely nonracemic PCB residues in forage fish (lake herring, rainbow smelt, and slimy sculpin) and lake trout suggest a combination of both in vivo biotransformation and uptake of nonracemic residues from prey for these species. Minimum biotransformation rates, calculated from enantiomer mass balances between predators and prey, suggest metabolic half-lives on the order of 8 yr for CB 136 in lake trout and 2.6 yr for CB 95 in sculpins. This result suggests that significant biotransformation may occur for metabolizable PCB congeners over the lifespan of these biota. This study highlights the potential of chiral analysis to study biotransformation processes in food webs.

Wong, Charles S.; Mabury, Scott A.; Whittle, D. Michael; Backus, Sean M.; Teixeira, Camilla; DeVault, David S.; Bronte, Charles R.; Muir, Derek C.G.

2004-01-01

273

The role of a water bug, Sigara striata, in freshwater food webs  

PubMed Central

Freshwater food webs are dominated by aquatic invertebrates whose trophic relationships are often poorly known. Here, I used laboratory experiments to study the role of a water bug, Sigara striata, as a potential predator and prey in food webs of stagnant waters. Multiple-choice predation experiment revealed that Sigara, which had been considered mostly herbivorous, also consumed larvae of Chironomus midges. Because they often occur in high densities and are among the most ubiquitous aquatic insects, Sigara water bugs may be important predators in fresh waters. A second experiment tested the role of Sigara as a potential prey for 13 common invertebrate predators. Mortality of Sigara inflicted by different predators varied widely, especially depending on body mass, foraging mode (ambush/searching) and feeding mode (chewing/suctorial) of the predators. Sigara was highly vulnerable to ambush predators, while searching predators caused on average 8.1 times lower mortality of Sigara. Additionally, suctorial predators consumed on average 6.6 times more Sigara individuals than chewing predators, which supports previous results hinting on potentially different predation pressures of these two types of predators on prey populations. The importance of these two foraging-related traits demonstrates the need to move from body mass based to multiple trait based descriptions of food web structure. Overall, the results suggests that detailed experimental studies of common but insufficiently known species can significantly enhance our understanding of food web structure. PMID:24883250

2014-01-01

274

Food web structure and mercury transfer in two contrasting Ugandan highland crater lakes (East Africa)  

E-print Network

Food web structure and mercury transfer in two contrasting Ugandan highland crater lakes (East.S.A. Abstract Volcanic crater lakes scattered throughout western Uganda are important local sources of water and fish. Two representative but contrasting crater lakes near the Kibale National Park were sampled

Chapman, Lauren J.

275

Food Web Structure and Basal Resource Utilization along a Tropical Island Stream Continuum, Puerto Rico  

Microsoft Academic Search

Tropical stream food webs are thought to be based primarily on terrestrial resources (leaf litter) in small forested headwater streams and algal resources in larger, wider streams. In tropical island streams, the dominant consumers are often omnivorous freshwater shrimps that consume algae, leaf litter, insects, and other shrimps. We used stable isotope analysis to examine (1) the relative importance of

James G. March; Catherine M. Pringle

2003-01-01

276

Indirect effects of metal contamination on energetics of yellow perch (Perca flavescens) resulting from food web  

E-print Network

Indirect effects of metal contamination on energetics of yellow perch (Perca flavescens) resulting (Perca flavescens) diet, growth and activity levels from lakes along a metal-contamination gradient were, lake food web, metal contamination, Perca flavescens, stunting, Sudbury, yellow perch Introduction

Rasmussen, Joseph

277

Tracing Fluxes Of Aquatic Production And Contaminants Into Terrestrial Food Webs With Nitrogen Stable Isotopes  

Microsoft Academic Search

Biomagnifying contaminants such as mercury can be transported and redistributed across the watershed by streams and rivers. Their fate and effects on consumers depend on food web transfer both within and between aquatic and terrestrial ecosystems. The Truckee River (Ca\\/Ne) is heavily contaminated by Hg originating from century-old upstream mining operations. We used nitrogen stable isotope analysis to trace the

A. Rivard; G. Cabana; W. Rainey; M. Power

2005-01-01

278

NEARSHORE-OFFSHORE PATTERNS IN FOOD WEB CHARACTERISTICS IN LAKE SUPERIOR  

EPA Science Inventory

We are exploring the use of food web properties to characterize nearshore and offshore habitats in the Great lakes. We analyzed the stable isotope signatures of benthos (predominantly Diporeia hoyi) and plankton from Lake Superior habitats ranging from 20m to 300m depth......

279

HYDROLOGY AND NUTRIENT EFFECTS ON FOOD-WEB STRUCTURE IN TEN LAKE SUPERIOR COASTAL WETLANDS  

EPA Science Inventory

The manuscript examines the effects of hydrology and nutrient enrichment on food-web structure. We find that the hydraulic residence time is a paramount constraint upon the relative contributions of planktonic versus benthic production to the fish community. Nutrient enrichment...

280

Diastereomer-specific bioaccumulation of hexabromocyclododecane (HBCD) in a coastal food web, Western Norway  

Microsoft Academic Search

The present study reports diastereomer-specific accumulation of HBCD from a point source in five marine species representing a typical food web in a Norwegian coastal area. Samples of mussels, polychaetes, crabs and seabird eggs were analyzed for the diastereomers ?-, ?- and ?-HBCD, as well as lipid content and stable isotopes of nitrogen (15N\\/14N) to estimate trophic level. Accumulated HBCD

Marianne Haukås; Ketil Hylland; Torgeir Nygård; John Arthur Berge; Espen Mariussen

2010-01-01

281

Infiltration by alien predators into invertebrate food webs in Hawaii: a molecular approach  

Microsoft Academic Search

Alien invertebrate predators have been introduced to Hawaii to control pests, particularly in lowland areas where most crops are grown. We developed techniques for assessing the impact of these predators on native food webs in relatively pristine upland areas where, it was hypothesized, few lowland predators might be found. Predator densities were assessed along transects within the Alakaii Swamp on

S. K. S HEPPARD; M. L. H ENNEMAN; J. MEMMOTT; W. O. C. SYMONDSON

2004-01-01

282

Are Algae Relevant to the Detritus-Based Food Web in Tank-Bromeliads?  

E-print Network

Are Algae Relevant to the Detritus-Based Food Web in Tank-Bromeliads? Olivier Brouard1 , Anne, Universite´ Paul Sabatier, UMR CNRS 5245, Toulouse, France Abstract We assessed the occurrence of algae and with regard to the structure of other aquatic microbial communities held in the tanks. Algae were retrieved

Boyer, Edmond

283

Columbia River food webs: Developing a broader scientific foundation for river restoration  

USGS Publications Warehouse

The objectives of this report are to provide a fundamental understanding of aquatic food webs in the Columbia River Basin and to illustrate and summarize their influences on native fish restoration efforts. The spatial scope addresses tributaries, impoundments, the free-flowing Columbia and Snake rivers, as well as the estuary and plume. Achieving the Council's vision for the Columbia River Fish and Wildlife Program (NPCC 2009-09) of sustaining a "productive and diverse community" that provides "abundant" harvest, is best accomplished through a time-prioritized action plan, one that complements other approaches while addressing important challenges and uncertainties related to the Basin's food webs. Note that the oceanic food webs, although of immense importance in sustaining fish populations, are not considered beyond the plume since they involve an additional set of complex and rapidly evolving issues. An analysis of oceanic food webs of relevance to the Columbia River requires a separately focused effort (e.g., Hoegh- Guldberg and Bruno 2010).

Alldredge, J. Richard; Beauchamp, David; Bisson, Peter A.; Congleton, James; Henny, Charles; Huntly, Nancy; Lamberson, Roland; Levings, Colin; Naiman, Robert J.; Pearcy, William; Rieman, Bruce; Ruggerone, Greg; Scarnecchia, Dennis; Smouse, Peter; Wood, Chris C.

2011-01-01

284

Detritus fuels ecosystem metabolism but not metazoan food webs in San Francisco estuary's freshwater delta  

USGS Publications Warehouse

Detritus from terrestrial ecosystems is the major source of organic matter in many streams, rivers, and estuaries, yet the role of detritus in supporting pelagic food webs is debated. We examined the importance of detritus to secondary productivity in the Sacramento and San Joaquin River Delta (California, United States), a large complex of tidal freshwater habitats. The Delta ecosystem has low primary productivity but large detrital inputs, so we hypothesized that detritus is the primary energy source fueling production in pelagic food webs. We assessed the sources, quantity, composition, and bioavailability of organic matter among a diversity of habitats (e.g., marsh sloughs, floodplains, tidal lakes, and deep river channels) over two years to test this hypothesis. Our results support the emerging principle that detritus dominates riverine and estuarine organic matter supply and supports the majority of ecosystem metabolism. Yet in contrast to prevailing ideas, we found that detritus was weakly coupled to the Delta's pelagic food web. Results from independent approaches showed that phytoplankton production was the dominant source of organic matter for the Delta's pelagic food web, even though primary production accounts for a small fraction of the Delta's organic matter supply. If these results are general, they suggest that the value of organic matter to higher trophic levels, including species targeted by programs of ecosystem restoration, is a function of phytoplankton production. ?? 2005 Estuarine Research Federation.

Sobczak, W.V.; Cloern, J.E.; Jassby, A.D.; Cole, B.E.; Schraga, T.S.; Arnsberg, A.

2005-01-01

285

UV Effects on Marine Planktonic Food Webs: A Synthesis of Results from Mesocosm Studies  

Microsoft Academic Search

UV irradiance has a broad range of effects on marine planktonic organisms. Direct and indirect effects on individual organisms have complex impacts on food-web structure and dynamics, with implications for carbon and nutrient cycling. Mesocosm experiments are well suited for the study of such complex interrelationships. Mesocosms offer the possibility to conduct well-controlled experiments with intact planktonic communities in physical,

Claude Belzile; Serge Demers; Gustavo A. Ferreyra; Irene Schloss; Christian Nozais; Karine Lacoste; Behzad Mostajir; Suzanne Roy; Michel Gosselin; Emilien Pelletier; Sônia M. F. Gianesella; Maria Vernet

2006-01-01

286

Dams and downstream aquatic biodiversity: Potential food web consequences of hydrologic and geomorphic change  

SciTech Connect

Responses of rivers and river ecosystems to dams are complex and varied, as they depend on local sediment supplies, geomorphic constraints, climate, dam structure and operation, and key attributes of the biota. Therefore, {open_quotes}one-size-fits-all{close_quotes} prescriptions cannot substitute for local knowledge in developing prescriptions for dam structure and operation to protect local biodiversity. One general principle is self-evident: that biodiversity is best protected in rivers where physical regimes are the most natural. A sufficiently natural regime of flow variation is particularly crucial for river biota and food webs. We review our research and that of others to illustrate the ecological importance of alternating periods of low an high flow, of periodic bed scour, and of floodplain inundation and dewatering. These fluctuations regulate both the life cycles of river biota and species interactions in the food webs that sustain them. Even if the focus of biodiversity conservation efforts is on a target species rather than whole ecosystems, a food web perspective is necessary, because populations of any species depend critically on how their resources, prey, and potential predators also respond to environmental change. In regulated rivers, managers must determine how the frequency, magnitude, and timing of hydrologic events interact to constrain or support species and food webs. Simple ecological modeling, tailored to local systems, may provide a framework and some insight into explaining ecosystem response to dams and should give direction to mitigation efforts. 78 refs.

Power, M.E.; Dietrich, W.E.; Finlay, J.C. [Univ. of California, Berkeley, CA (United States)

1996-11-01

287

Author's personal copy Mercury biomagnification in the food web of a neotropical stream  

E-print Network

Seasonal inundation Anthropogenic and natural mercury (Hg) contamination have been a major concern in SouthAuthor's personal copy Mercury biomagnification in the food web of a neotropical stream Sae Yun Available online 17 January 2012 Keywords: Prochilodus Mercury Stable isotope Trophic guild Tropical river

McIntyre, Peter

288

Food-web structure and network theory: The role of connectance and size  

Microsoft Academic Search

Networks from a wide range of physical, biological, and social systems have been recently described as ''small-world'' and ''scale- free.'' However, studies disagree whether ecological networks called food webs possess the characteristic path lengths, clustering coefficients, and degree distributions required for membership in these classes of networks. Our analysis suggests that the disagree- ments are based on selective use of

Jennifer A. Dunne; Richard J. Williams; Neo D. Martinez

2002-01-01

289

MONITORING FOOD WEB CHANGES IN TIDE-RESTORED SALT MARSHES: A CARBON STABLE ISOTOPE APPROACH  

EPA Science Inventory

Primary producer (angiosperms, macroalgae, submerged aquatic vegetation), suspended particulate matter, and Fundulus heteroclitus isotope values (d13C , d15N, d34S) were examined to assess their use as an indicator for changes in food web support functions in tidally-restored sal...

290

Estuarine Microbial Food Web Patterns in a Lake Erie Coastal Wetland  

Microsoft Academic Search

Composition and distribution of planktonic protists were examined relative to microbial food web dynamics (growth, grazing, and nitrogen cycling rates) at the Old Woman Creek (OWC) National Estuarine Research Reserve during an episodic storm event in July 2003. More than 150 protistan taxa were identified based on morphology. Species richness and microbial biomass measured via microscopy and flow cytometry increased

P. J. Lavrentyev; M. J. McCarthy; D. M. Klarer; F. Jochem; W. S. Gardner

2004-01-01

291

Effects of an Omnivorous Katydid, Salinity, and Nutrients on a Planthopper-Spartina Food Web  

E-print Network

Effects of an Omnivorous Katydid, Salinity, and Nutrients on a Planthopper-Spartina Food Web Juan M and nutrients. How omnivorous consumers respond to variation in prey availability and plant quality is poorly understood. We used a mesocosm experiment to examine how salinity, nutrients, an omnivore (the katydid

Pennings, Steven C.

292

The Importance of Allochthonous Subsidies to an Estuarine Food Web along a Salinity Gradient  

EPA Science Inventory

Estuarine food webs function within a heterogeneous mosaic and are supported by a mix of primary producers from both local and distant sources. Processes governing the exchange and consumption of organic matter (OM), however, are poorly understood. To study the contribution of ...

293

Seeking Emotional Involvement in Science Education: Food-Chains and Webs.  

ERIC Educational Resources Information Center

Documents a study of emotion in two grade 8 science classrooms. Describes a lesson on food-chains and webs designed with a conceptual and an emotional agenda. Discusses issues of emotion, sensation and relevance in science teaching. (Author/MM)

Alsop, Steve

2001-01-01

294

Indirect effects of zebra mussels (Dreissena polymorpha) on the planktonic food web  

E-print Network

Indirect effects of zebra mussels (Dreissena polymorpha) on the planktonic food web Erik G. Noonburg, Brian J. Shuter, and Peter A. Abrams Abstract: The exotic zebra mussel (Dreissena polymorpha) has. In some lakes, zebra mussels appear to have had little effect on zooplankton den- sity, despite decreasing

Noonburg, Erik

295

Farming practices change food web structures in cereal aphid-parasitoid-hyperparasitoid communities.  

PubMed

Agricultural intensification has been shown to result in a decline in biodiversity across many taxa, but the changes in community structure and species interactions remain little understood. We have analysed and compared the structure of feeding interactions for cereal aphids and their primary and secondary parasitoids in organically and conventionally managed winter wheat fields using quantitative food web metrics (interaction evenness, generality, vulnerability, link density). Despite little variation in the richness of each trophic group, food web structures between the two farming systems differed remarkably. In contrast to common expectations, aphids and primary parasitoids were characterized by (1) a higher evenness of interaction frequencies (interaction evenness) in conventional fields, which cascaded to interactions at the next trophic level, with (2) a higher interaction evenness, (3) a higher ratio of primary parasitoid taxa per secondary parasitoid (generality) and (4) a higher link density. Aphid communities in the organically managed fields almost exclusively consisted of a single ear-colonizing species, Sitobion avenae, while highly fertilized conventional fields were mainly infested by leaf-colonizing aphids that benefit from the nutritional status of winter wheat. In conclusion, agricultural intensification appears to foster the complexity of aphid-parasitoid food webs, thereby not supporting the general expectation on the importance of organic farming practices for species richness and food web complexity. PMID:22736196

Lohaus, Katharina; Vidal, Stefan; Thies, Carsten

2013-01-01

296

E.2. Electronic Appendix -Food Web Elements of the Fraser River Upper River (above rkm 210)  

E-print Network

) Food webs: Microbenthic algae (periphyton), detritus from riparian vegetation and littoral insects river to the lower river (Reynoldson et al. 2005). Juvenile stream-type Chinook rear along (Kelly et al. 2007). Logging has impacted the temperature regime and likely the productivity of insect

297

SHIFTS BETWEEN PERIPHYTON-AND PHYTOPLANKTON-BASED FOOD WEBS IN GREAT LAKES COASTAL WETLANDS  

EPA Science Inventory

Numerous studies have revealed the importance of algae as an energetic base for wetland food webs. Earlier carbon and nitrogen stable isotope analyses in a Lake Superior coastal wetland (Allouez Bay, WI) indicated that, despite the large amount of vascular plant biobass present, ...

298

Influence of streamside vegetation on inputs of terrestrial invertebrates to salmonid food webs  

E-print Network

Influence of streamside vegetation on inputs of terrestrial invertebrates to salmonid food webs J, and spawning migrations. We examined the contribution of terrestrially derived invertebrates (TI) to juvenile of invertebrate mass averaged across all sites; no significant differences associated with location (plant

Wagner, Diane

299

Effects of light reduction on food webs and associated ecosystem services of Yaquina Bay  

EPA Science Inventory

Reduced water clarity can affect estuarine primary production but little is known of its subsequent effects to consumer guilds or ecosystem services. We investigated those effects using inverse analysis of modeled food webs of the lower (polyhaline) and upper (mesohaline) reache...

300

Succession processes in a food web of a two autotroph-one herbivore system  

Microsoft Academic Search

This paper deals with the succession process of a food web model consisting of one herbivore, two autotrophs and available nutrient in the environment in a closed nutrient flux. The model provides a way of describing successional changes in the form of species replacement with increasing nutrient levels. It is shown that distinct threshold (with upper and lower) values of

Dipak Kesh; A. K. Sarkar; A. B. Roy

2000-01-01

301

Contribution of Allochthonous Carbon Subsidies to the Minho Estuary Lower Food Web  

EPA Science Inventory

To study the contribution of autochthonous and allochthonous organic matter (OM) sources fuelling the lower food web in Minho River estuary (N-Portugal, Europe), we characterized the carbon (?13C) and nitrogen (?15N) stable isotope ratios of zooplankton and their potential OM sou...

302

From the Top of the World...to the Bottom of the Food Web  

NSDL National Science Digital Library

This resource, by the Bigelow Laboratory, is designed to help teachers and students discover linkages among marine ecology, phytoplankton, the behavior of light at the ocean surface, and satellite-derived ocean color data. On-line standards, based educational activities, explore the topics of phytoplankton, food webs, and algal blooms using microscopy and remote sensing data.

Bigelow Laboratory for Ocean Sciences

303

BENTHIC PRODUCTION AS THE BASE FOR FOOD WEBS IN ALASKAN ARCTIC LAKES  

EPA Science Inventory

Plankton are traditionally viewed as the basis for limnetic food webs, with zooplankton acting as an energy gateway between phytoplanktonic primary producers and fish. Often, benthic production is considered to be important primarily to the benthos and in shallow systems, such as...

304

Evidence for biomagnification of rubidium in freshwater and marine food webs  

Microsoft Academic Search

Rubidium (Rb), a rarely studied alkali metal, may be an essential ultra-trace element for humans and other organisms. However, very little information exists in regard to the concentrations and distribution of Rb in freshwater and marine food webs. We measured Rb concentrations in freshwater fish from Lake Erie and two Arctic lakes (Lake Hazen and Resolute Lake) and in seabirds,

Linda M. Campbell; Aaron T. Fisk; Xiaowa Wang; Günter Köck; Derek C. G. Muir

2005-01-01

305

Differential support of lake food webs by three types of terrestrial organic carbon  

E-print Network

subsidize ecosystem metabolism and support the production of consumers of the receiving ecosystem (Vanni and James R. Hodgson3 1 Institute of Ecosystem Studies, Box AB (65 Sharon Turnpike), Millbrook, NY 12545 Organic carbon inputs from outside of ecosystem boundaries potentially subsidize recipient food webs. Four

Berkowitz, Alan R.

306

Linking Landscapes and Food Webs: Effects of Omnivorous Fish and Watersheds on Reservoir Ecosystems  

NSDL National Science Digital Library

This peer-reviewed article from BioScience is the effects of omnivorous fish and watersheds on reservoirs. Ecologists increasingly recognize the need to understand how landscapes and food webs interact. Reservoir ecosystems are heavily subsidized by nutrients and detritus from surrounding watersheds, and often contain abundant populations of gizzard shad, an omnivorous fish that consumes plankton and detritus. Gizzard shad link terrestrial landscapes and pelagic reservoir food webs by consuming detritus, translocating nutrients from sediment detritus to the water column, and consuming zooplankton. The abundance of gizzard shad increases with watershed agriculturalization, most likely through a variety of mechanisms operating on larval and adult life stages. Gizzard shad have myriad effects on reservoirs, including impacts on nutrients, phytoplankton, zooplankton, and fish, and many of their effects vary with ecosystem productivity (i.e., watershed land use). Interactive feedbacks among watersheds, gizzard shad populations, and reservoir food webs operate to maintain dominance of gizzard shad in highly productive systems. Thus, effective stewardship of reservoir ecosystems must incorporate both watershed and food-web perspectives.

MICHAEL J. VANNI, KRISTIN K. AREND, MARY T. BREMIGAN, DAVID B. BUNNELL, JAMES E. GARVEY, MARÍA J. GONZÁLEZ, WILLIAM H. RENWICK, PATRICIA A. SORANNO, and ROY A. STEIN (; )

2005-02-01

307

Common patterns of energy flow and biomass distribution on weighted food webs  

NASA Astrophysics Data System (ADS)

Weights of edges and nodes on food webs which are available from the empirical data hide much information about energy flows and biomass distributions in ecosystem. We define a set of variables related to weights for each species i, including the throughflow Ti, the total biomass Xi, and the dissipated flow Di (output to the environment) to uncover the following common patterns in 19 empirical weighted food webs: (1) DGBD distributions (Discrete version of a Generalized Beta Distribution), a kind of deformed Zipf's law, of energy flow and storage biomass; (2) The allometric scaling law Ti?Xi?, which can be viewed as the counterpart of the Kleiber's 3/4 law at the population level; (3) The dissipation law Di?Ti?; and (4) The gravity law, including univariate version f?( and bivariate approvement f?Ti?1Tj?2. These patterns are very common and significant in all collected webs, as a result, some remarkable regularities are hidden in weights.

Zhang, Jiang; Feng, Yuanjing

2014-07-01

308

Differences in methylmercury and inorganic mercury biomagnification in a tropical marine food web.  

PubMed

Methylmercury (MeHg), inorganic mercury (Hginorg) and their biomagnification factors (BMF) were evaluated along a non-degraded Brazilian bay food web. Highly significant differences (p < 0.0001) were found between MeHg and Hginorg concentrations among all organisms (microplankton, shrimp, fish and dolphin). MeHg increased with increasing trophic position while Hginorg did not present the same pattern. BMF values for MeHg were higher than 1 for all trophic interactions from source to consumer, indicating that MeHg was transferred more efficiently and biomagnified over the entire web. Only one BMF exceeding one was observed for Hginorg (27) between microplankton and their consumer, planktivorous fish. BMF values for Hginorg were significantly different than those found for MeHg (20) at the base of the food web. PMID:24452478

Seixas, Tércia G; Moreira, Isabel; Siciliano, Salvatore; Malm, Olaf; Kehrig, Helena A

2014-03-01

309

Food-Web Structure in Relation to Environmental Gradients and Predator-Prey Ratios in Tank-Bromeliad Ecosystems  

PubMed Central

Little is known of how linkage patterns between species change along environmental gradients. The small, spatially discrete food webs inhabiting tank-bromeliads provide an excellent opportunity to analyse patterns of community diversity and food-web topology (connectance, linkage density, nestedness) in relation to key environmental variables (habitat size, detrital resource, incident radiation) and predators:prey ratios. We sampled 365 bromeliads in a wide range of understorey environments in French Guiana and used gut contents of invertebrates to draw the corresponding 365 connectance webs. At the bromeliad scale, habitat size (water volume) determined the number of species that constitute food-web nodes, the proportion of predators, and food-web topology. The number of species as well as the proportion of predators within bromeliads declined from open to forested habitats, where the volume of water collected by bromeliads was generally lower because of rainfall interception by the canopy. A core group of microorganisms and generalist detritivores remained relatively constant across environments. This suggests that (i) a highly-connected core ensures food-web stability and key ecosystem functions across environments, and (ii) larger deviations in food-web structures can be expected following disturbance if detritivores share traits that determine responses to environmental changes. While linkage density and nestedness were lower in bromeliads in the forest than in open areas, experiments are needed to confirm a trend for lower food-web stability in the understorey of primary forests. PMID:23977128

Dézerald, Olivier; Leroy, Céline; Corbara, Bruno; Carrias, Jean-François; Pélozuelo, Laurent; Dejean, Alain; Céréghino, Régis

2013-01-01

310

Tracing organophosphorus and brominated flame retardants and plasticizers in an estuarine food web.  

PubMed

Nine organophosphorus flame retardants (PFRs) were detected in a pelagic and benthic food web of the Western Scheldt estuary, The Netherlands. Concentrations of several PFRs were an order of magnitude higher than those of the brominated flame retardants (BFRs). However, the detection frequency of the PFRs (6-56%) was lower than that of the BFRs (50-97%). Tris(2-butoxyethyl) phosphate (TBOEP), tris(isobutyl) phosphate (TIBP) and tris(2-chloroisopropyl) phosphate (TCIPP) were the dominant PFRs in sediment with median concentrations of 7.0, 8.1 and 1.8 ng/g dry weight (dw), respectively. PFR levels in the suspended particular matter (SPM) were 2-12 times higher than that in sediment. TBOEP, TCIPP, TIBP, tris(2-chloroethyl) phosphate (TCEP) and tris(phenyl) phosphate (TPHP) were found in organisms higher in the estuarine food web. The highest PFR concentrations in the benthic food web were found in sculpin, goby and lugworm with median concentrations of 17, 7.4, 4.6 and 2.0 ng/g wet weight (ww) for TBOEP, TIBP, TCIPP and TPHP, respectively. Comparable levels were observed in the pelagic food web, BDE209 was the predominant PBDE in sediment and SPM with median concentrations up to 9.7 and 385 ng/g dw, respectively. BDE47 was predominant in the biotic compartment of the food web with highest median levels observed in sculpin and common tern eggs of 79 ng/g lipid weight (lw) (2.5 ng/g ww) and 80 ng/g lw (11 ng/g ww), respectively. Trophic magnification was observed for all PBDEs with the exception of BDE209. Indications of trophic magnification of PFRs were observed in the benthic food web for TBOEP, TCIPP and TCEP with tentative trophic magnification factors of 3.5, 2.2 and 2.6, respectively (p<0.05). Most of the other PFRs showed trophic dilution in both food webs. The relative high PFR levels in several fish species suggest high emissions and substantial exposure of organisms to PFRs in the Western Scheldt. PMID:25306092

Brandsma, Sicco H; Leonards, Pim E G; Leslie, Heather A; de Boer, Jacob

2015-02-01

311

Reducing Methylmercury Accumulation in the Food Webs of San Francisco Bay and Its Local Watersheds  

PubMed Central

San Francisco Bay (California, USA) and its local watersheds present an interesting case study in estuarine mercury (Hg) contamination. This review focuses on the most promising avenues for attempting to reduce methylmercury (MeHg) contamination in Bay Area aquatic food webs and identifying the scientific information that is most urgently needed to support these efforts. Concern for human exposure to MeHg in the region has led to advisories for consumption of sport fish. Striped bass from the Bay have the highest average Hg concentration measured for this species in USA estuaries, and this degree of contamination has been constant for the past 40 years. Similarly, largemouth bass in some Bay Area reservoirs have some of the highest Hg concentrations observed in the entire US. Bay Area wildlife, particularly birds, face potential impacts to reproduction based on Hg concentrations in the tissues of several Bay species. Source control of Hg is one of the primary possible approaches for reducing MeHg accumulation in Bay Area aquatic food webs. Recent findings (particularly Hg isotope measurements) indicate that the decades-long residence time of particle-associated Hg in the Bay is sufficient to allow significant conversion of even the insoluble forms of Hg into MeHg. Past inputs have been thoroughly mixed throughout this shallow and dynamic estuary. The large pool of Hg already present in the ecosystem dominates the fraction converted to MeHg and accumulating in the food web. Consequently, decreasing external Hg inputs can be expected to reduce MeHg in the food web, but it will likely take many decades to centuries before those reductions are achieved. Extensive efforts to reduce loads from the largest Hg mining source (the historic New Almaden mining district) are underway. Hg is spread widely across the urban landscape, but there are a number of key sources, source areas, and pathways that provide opportunities to capture larger quantities of Hg and reduce loads from urban runoff. Atmospheric deposition is a lower priority for source control in the Bay Area due to a combination of a lack of major local sources and Hg isotope data indicating it is a secondary contributor to food web MeHg. Internal net production of MeHg is the dominant source of MeHg that enters the food web. Controlling internal net production is the second primary management approach, and has the potential to reduce food web MeHg more effectively and within a much shorter time-frame. MeHg cycling and control opportunities vary by habitat. Controlling net MeHg production and accumulation in the food web of upstream reservoirs and ponds is very promising due to the many features of these ecosystems that can be manipulated. The most feasible control options in tidal marshes relate to the design of flow patterns and subhabitats in restoration projects. Options for controlling MeHg production in open Bay habitat are limited due primarily to the highly dispersed distribution of Hg throughout the ecosystem. Other changes in these habitats may also have a large influence on food web MeHg, including temperature changes due to global warming, sea level rise, food web alterations due to introduced species and other causes, and changes in sediment supply. Other options for reducing or mitigating exposure and risk include controlling bioaccumulation, cleanup of contaminated sites, and reducing other factors (e.g., habitat availability) that limit at risk wildlife populations. PMID:23122771

Davis, J.A.; Looker, R.E.; Yee, D.; Marvin-DiPasquale, M.; Grenier, J.L.; Austin, C.M.; McKee, L.J.; Greenfield, B.K.; Brodberg, R.; Blum, J.D.

2013-01-01

312

Depth-specific Analyses of the Lake Superior Food Web  

EPA Science Inventory

Characteristics of large, deep aquatic systems include depth gradients in community composition, in the quality and distribution of food resources, and in the strategies that organisms use to obtain their nutrition. In Lake Superior, nearshore communities that rely upon a combina...

313

Food web interactions and nutrients dynamics in polyculture ponds  

Microsoft Academic Search

Artificial feed and fertilizers are the main sources of nutrients supporting fish growth in aquaculture ponds. The majority of the added nutrients are lost to the sediment, where they are no longer available for natural food production. By increasing resuspension of the sediment through the introduction of benthivorous fish, nutrient loss may be reduced, because of the re-mobilisation of nutrients

M. M. Rahman

2006-01-01

314

Insects for space agriculture and sustainable foods web on Earth  

Microsoft Academic Search

We propose the use insects for space foods. Since space agriculture will farm many different plant species, some of species require to be pollinated by the help of insects, which have been co-evolved with entomophilous flowering plants. Among major plant species defined for space agriculture, soybean is essential for providing proteins for our diet,. Soybean is an entomophilous species together

Naomi Katayama; T. Yoshimura; K. Baba; Masamichi Yamashita

2009-01-01

315

Carbon flows in the benthic food web at the deep-sea observatory HAUSGARTEN (Fram Strait)  

NASA Astrophysics Data System (ADS)

The HAUSGARTEN observatory is located in the eastern Fram Strait (Arctic Ocean) and used as long-term monitoring site to follow changes in the Arctic benthic ecosystem. Linear inverse modelling was applied to decipher carbon flows among the compartments of the benthic food web at the central HAUSGARTEN station (2500 m) based on an empirical data set consisting of data on biomass, prokaryote production, total carbon deposition and community respiration. The model resolved 99 carbon flows among 4 abiotic and 10 biotic compartments, ranging from prokaryotes up to megafauna. Total carbon input was 3.78±0.31 mmol C m -2 d -1, which is a comparatively small fraction of total primary production in the area. The community respiration of 3.26±0.20 mmol C m -2 d -1 is dominated by prokaryotes (93%) and has lower contributions from surface-deposit feeding macro- (1.7%) and suspension feeding megafauna (1.9%), whereas contributions from nematode and other macro- and megabenthic compartments were limited to <1%. The high prokaryotic contribution to carbon processing suggests that functioning of the benthic food web at the central HAUSGARTEN station is comparable to abyssal plain sediments that are characterised by strong energy limitation. Faunal diet compositions suggest that labile detritus is important for deposit-feeding nematodes (24% of their diet) and surface-deposit feeding macrofauna (˜44%), but that semi-labile detritus is more important in the diets of deposit-feeding macro- and megafauna. Dependency indices on these food sources were also calculated as these integrate direct (i.e. direct grazing and predator-prey interactions) and indirect (i.e. longer loops in the food web) pathways in the food web. Projected sea-ice retreats for the Arctic Ocean typically anticipate a decrease in the labile detritus flux to the already food-limited benthic food web. The dependency indices indicate that faunal compartments depend similarly on labile and semi-labile detritus, which suggests that the benthic biota may be more sensitive to changes in labile detritus inputs than when assessed from diet composition alone. Species-specific responses to different types of labile detritus inputs, e.g. pelagic algae versus sympagic algae, however, are presently unknown and are needed to assess the vulnerability of individual components of the benthic food web.

van Oevelen, Dick; Bergmann, Melanie; Soetaert, Karline; Bauerfeind, Eduard; Hasemann, Christiane; Klages, Michael; Schewe, Ingo; Soltwedel, Thomas; Budaeva, Nataliya E.

2011-11-01

316

Biochemical tracers reveal intra-specific differences in the food webs utilized by individual seabirds.  

PubMed

Food web structure regulates the pathways and flow rates of energy, nutrients, and contaminants to top predators. Ecologically and physiologically meaningful biochemical tracers provide a means to characterize and quantify these transfers within food webs. In this study, changes in the ratios of stable N isotopes (e.g., delta(15)N), fatty acids (FA), and persistent contaminants were used to trace food web pathways utilized by herring gulls (Larus argentatus) breeding along the shores of the St Lawrence River, Canada. Egg delta(15)N values varied significantly among years and were used as an indicator of gull trophic position. Temporal trends in egg delta(15)N values were related to egg FA profiles. In years when egg delta(15)N values were greater, egg FA patterns reflected the consumption of more aquatic prey. Egg delta(15)N values were also correlated with annual estimates of prey fish abundance. These results indicated that temporal changes in aquatic prey availability were reflected in the gull diet (as inferred from ecological tracer profiles in gull eggs). Analysis of individual eggs within years confirmed that birds consuming more aquatic prey occupied higher trophic positions. Furthermore, increases in trophic position were associated with increased concentrations of most persistent organic contaminants in eggs. However, levels of highly brominated polybrominated diphenyl ether congeners, e.g, 2,2',3,3',4,4',5,5',6,6'-decabromoDE (BDE-209), showed a negative relationship with trophic position. These contrasting findings reflected differences among contaminant groups/homologs in terms of their predominant routes of transfer, i.e., aquatic versus terrestrial food webs. High trophic level omnivores, e.g., herring gulls, are common in food webs. By characterizing ecological tracer profiles in such species we can better understand spatial, temporal, and individual differences in pathways of contaminant, energy, and nutrient flow. PMID:19219461

Hebert, Craig E; Weseloh, D V Chip; Gauthier, Lewis T; Arts, Michael T; Letcher, Robert J

2009-05-01

317

Nearshore energy subsidies support Lake Michigan fishes and invertebrates following major changes in food web structure.  

PubMed

Aquatic food webs that incorporate multiple energy channels (e.g., nearshore benthic and pelagic) with varying productivity and turnover rates convey stability to biological communities by providing independent energy sources. Within the Lake Michigan food web, invasive dreissenid mussels have caused rapid changes to food web structure and potentially altered the channels through which consumers acquire energy. We used stable C and N isotopes to determine how Lake Michigan food web structure has changed in the past decade, coincident with the expansion of dreissenid mussels, decreased pelagic phytoplankton production, and increased nearshore benthic algal production. Fish and invertebrate samples collected from sites around Lake Michigan were analyzed to determine taxa-specific 13C:12C (delta13C) and 15N:14N (delta15N) ratios. Sampling took place during two distinct periods, 2002-2003 and 2010-2012, that spanned the period of dreissenid expansion, and included nearshore, pelagic and profundal fish and invertebrate taxa. The magnitude and direction of the delta13C shift indicated significantly greater reliance upon nearshore benthic energy sources among nearly all fish taxa as well as profundal invertebrates following dreissenid expansion. Although the mechanisms underlying this delta13C shift likely varied among species, possible causes include the transport of benthic algal production to offshore waters and increased feeding on nearshore prey items by pelagic and profundal species. delta15N shifts were more variable and of smaller magnitude across taxa, although declines in delta15N among some pelagic fishes suggest a shift to alternative prey resources. Lake Michigan fishes and invertebrates appear to have responded to dreissenid-induced changes in nutrient and energy pathways by switching from pelagic to alternative nearshore energy subsidies. Although large shifts in energy allocation (i.e., pelagic to nearshore benthic) resulting from invasive species appear to affect total production at upper trophic levels, changes in trophic structure and utilization of novel energy pathways may help to stabilize food webs following species invasions. PMID:25000756

Turschak, Benjamin A; Bunnell, David; Czesny, Sergiusz; Höök, Tomas O; Janssen, John; Warner, David; Bootsma, Harvey A

2014-05-01

318

Hydrogeomorphic features mediate the effects of land use/cover on reservoir productivity and food webs  

USGS Publications Warehouse

Although effects of land use/cover on nutrient concentrations in aquatic systems are well known, half or more of the variation in nutrient concentration remains unexplained by land use/cover alone. Hydrogeomorphic (HGM) landscape features can explain much remaining variation and influence food web interactions. To explore complex linkages among land use/cover, HGM features, reservoir productivity, and food webs, we sampled 11 Ohio reservoirs, ranging broadly in agricultural catchment land use/cover, for 3 years. We hypothesized that HGM features mediate the bottom-up effects of land use/cover on reservoir productivity, chlorophyll a, zooplankton, and recruitment of gizzard shad, an omnivorous fish species common throughout southeastern U.S. reservoirs and capable of exerting strong effects on food web and nutrient dynamics. We tested specific hypotheses using a model selection approach. Percent variation explained was highest for total nitrogen (R2 = 0.92), moderately high for total phosphorus, chlorophyll a, and rotifer biomass (R2 = 0.57 to 0.67), relatively low for crustacean zooplankton biomass and larval gizzard shad hatch abundance (R2 = 0.43 and 0.42), and high for larval gizzard shad survivor abundance (R2 = 0.79). The trophic status models included agricultural land use/cover and an HGM predictor, whereas the zooplankton models had few HGM predictors. The larval gizzard shad models had the highest complexity, including more than one HGM feature and food web components. We demonstrate the importance of integrating land use/cover, HGM features, and food web interactions to investigate critical interactions and feedbacks among physical, chemical, and biological components of linked land-water ecosystems.

Bremigan, M.T.; Soranno, P.A.; Gonzalez, M.J.; Bunnell, D.B.; Arend, K.K.; Renwick, W.H.; Stein, R.A.; Vanni, M.J.

2008-01-01

319

The authors of the ISAB Report Columbia River Basin Food Webs: Developing a Broader Scientific Foundation for Fish and Wildlife Restoration (ISAB 2011-1)  

E-print Network

The authors of the ISAB Report Columbia River Basin Food Webs: Developing a Broader Scientific published online in Early Editions, November 28, 2012. Developing a broader scientific foundation for river restoration: Columbia River food webs Abstract. Well-functioning food webs are fundamental for sustaining

320

Protozoans as a food source for Antarctic krill, Euphausia superba: Complementary insights from stomach content, fatty acids, and stable isotopes  

Microsoft Academic Search

We studied the diet of Antarctic krill, Euphausia superba, at five stations across the southwest Atlantic sector in summer 2003 by analyzing stomach content, fatty acids, and stable isotopes on the same individuals. Our aim was to examine what each method could contribute to our understanding of krill nutrition and whether differences seen in growth rates were linked to their

Katrin Schmidt; Angus Atkinson; Klaus-Jürgen Petzke; Maren Voss; David W. Pond

2006-01-01

321

Food web structure in exotic and native mangroves: a Hawaii-Puerto Rico comparison.  

PubMed

Plant invasions can fundamentally alter detrital inputs and the structure of detritus-based food webs. We examined the detrital pathways in mangrove food webs in native (Puerto Rican) and introduced (Hawaiian) Rhizophora mangle forests using a dual isotope approach and a mixing model. Based on trophic-level fractionation of 0-1 per thousand for delta(13)C and 2-3 per thousand for delta(15)N, among the invertebrates, only nematodes, oligochaetes, and nereid polychaetes from native mangroves exhibited stable isotopes consistent with a mangrove-derived diet. Certain fauna, in particular tubificid oligochaetes, had delta(13)C values consistent with the consumption of mangrove leaves, but they were depleted in (15)N, suggesting their primary nitrogen source was low in (15)N, and was possibly N(2)-fixing bacteria. In introduced mangroves, all feeding groups appeared to rely heavily on non-mangrove sources, especially phytoplankton inputs. Mixing model results and discriminant analysis showed clear separation of introduced and native mangrove sites based on differential food source utilization within feeding groups, with stronger and more diverse use of benthic foods observed in native forests. Observed differences between native and invasive mangrove food webs may be due to Hawaiian detritivores being poorly adapted to utilizing the tannin-rich, nitrogen-poor mangrove detritus. In addition, differential utilization of mangrove detritus between native and introduced mangroves may be a consequence of forest age. We postulate that increasing mangrove forest age may promote diversification of bacterial food webs important in N and S cycling. Our results also suggest a potentially important role for sulfur bacteria in supporting the most abundant infaunal consumers, nematodes, in the most mature systems. PMID:17587064

Demopoulos, Amanda W J; Fry, Brian; Smith, Craig R

2007-09-01

322

Food web structure in exotic and native mangroves: A Hawaii-Puerto Rico comparison  

USGS Publications Warehouse

Plant invasions can fundamentally alter detrital inputs and the structure of detritus-based food webs. We examined the detrital pathways in mangrove food webs in native (Puerto Rican) and introduced (Hawaiian) Rhizophora mangle forests using a dual isotope approach and a mixing model. Based on trophic-level fractionation of 0-1??? for ?? 13C and 2-3??? for ?? 15N, among the invertebrates, only nematodes, oligochaetes, and nereid polychaetes from native mangroves exhibited stable isotopes consistent with a mangrove-derived diet. Certain fauna, in particular tubificid oligochaetes, had ?? 13C values consistent with the consumption of mangrove leaves, but they were depleted in 15N, suggesting their primary nitrogen source was low in 15N, and was possibly N 2-fixing bacteria. In introduced mangroves, all feeding groups appeared to rely heavily on non-mangrove sources, especially phytoplankton inputs. Mixing model results and discriminant analysis showed clear separation of introduced and native mangrove sites based on differential food source utilization within feeding groups, with stronger and more diverse use of benthic foods observed in native forests. Observed differences between native and invasive mangrove food webs may be due to Hawaiian detritivores being poorly adapted to utilizing the tannin-rich, nitrogen-poor mangrove detritus. In addition, differential utilization of mangrove detritus between native and introduced mangroves may be a consequence of forest age. We postulate that increasing mangrove forest age may promote diversification of bacterial food webs important in N and S cycling. Our results also suggest a potentially important role for sulfur bacteria in supporting the most abundant infaunal consumers, nematodes, in the most mature systems. ?? 2007 Springer-Verlag.

Demopoulos, A.W.J.; Fry, B.; Smith, C.R.

2007-01-01

323

Isotopic studies in Pacific Panama mangrove estuaries reveal lack of effect of watershed deforestation on food webs.  

PubMed

Stable isotopic N, C, and S in food webs of 8 mangrove estuaries on the Pacific coast of Panama were measured to 1) determine whether the degree of deforestation of tropical forests on the contributing watersheds was detectable within the estuarine food web, and 2) define external sources of the food webs within the mangrove estuaries. Even though terrestrial rain forest cover on the contributing watersheds differed between 23 and 92%, the effect of deforestation was not detectable on stable isotopic values in food webs present at the mouth of the receiving estuaries. We used stable isotopic measures to identify producers or organic sources that supported the estuarine food web. N isotopic values of consumers spanned a broad range, from about 2.7 to 12.3‰. Mean ?(15)N of primary producers and organic matter varied from 3.3 for macroalgae to 4.7‰ for suspended particulate matter and large particulate matter. The ?(13)C consumer data varied between -26 and -9‰, but isotopic values of the major apparent producers or organic matter sampled could not account for this range variability. The structure of the food web was clarified when we added literature isotopic values of microphytobenthos and coralline algae, suggesting that these, or other producers with similar isotopic signature, may be part of the food webs. PMID:25481652

Viana, Inés G; Valiela, Ivan; Martinetto, Paulina; Monteiro Pierce, Rita; Fox, Sophia E

2015-02-01

324

From projected species distribution to food-web structure under climate change.  

PubMed

Climate change is inducing deep modifications in species geographic ranges worldwide. However, the consequences of such changes on community structure are still poorly understood, particularly the impacts on food-web properties. Here, we propose a new framework, coupling species distribution and trophic models, to predict climate change impacts on food-web structure across the Mediterranean Sea. Sea surface temperature was used to determine the fish climate niches and their future distributions. Body size was used to infer trophic interactions between fish species. Our projections reveal that 54 fish species of 256 endemic and native species included in our analysis would disappear by 2080-2099 from the Mediterranean continental shelf. The number of feeding links between fish species would decrease on 73.4% of the continental shelf. However, the connectance of the overall fish web would increase on average, from 0.26 to 0.29, mainly due to a differential loss rate of feeding links and species richness. This result masks a systematic decrease in predator generality, estimated here as the number of prey species, from 30.0 to 25.4. Therefore, our study highlights large-scale impacts of climate change on marine food-web structure with potential deep consequences on ecosystem functioning. However, these impacts will likely be highly heterogeneous in space, challenging our current understanding of climate change impact on local marine ecosystems. PMID:24214576

Albouy, Camille; Velez, Laure; Coll, Marta; Colloca, Francesco; Le Loc'h, François; Mouillot, David; Gravel, Dominique

2014-03-01

325

River Food Web Response to Large-Scale Riparian Zone Manipulations  

PubMed Central

Conservation programs often focus on select species, leading to management plans based on the autecology of the focal species, but multiple ecosystem components can be affected both by the environmental factors impacting, and the management targeting, focal species. These broader effects can have indirect impacts on target species through the web of interactions within ecosystems. For example, human activity can strongly alter riparian vegetation, potentially impacting both economically-important salmonids and their associated river food web. In an Olympic Peninsula river, Washington state, USA, replicated large-scale riparian vegetation manipulations implemented with the long-term (>40 yr) goal of improving salmon habitat did not affect water temperature, nutrient limitation or habitat characteristics, but reduced canopy cover, causing reduced energy input via leaf litter, increased incident solar radiation (UV and PAR) and increased algal production compared to controls. In response, benthic algae, most insect taxa, and juvenile salmonids increased in manipulated areas. Stable isotope analysis revealed a predominant contribution of algal-derived energy to salmonid diets in manipulated reaches. The experiment demonstrates that riparian management targeting salmonids strongly affects river food webs via changes in the energy base, illustrates how species-based management strategies can have unanticipated indirect effects on the target species via the associated food web, and supports ecosystem-based management approaches for restoring depleted salmonid stocks. PMID:23284786

Wootton, J. Timothy

2012-01-01

326

River food web response to large-scale riparian zone manipulations.  

PubMed

Conservation programs often focus on select species, leading to management plans based on the autecology of the focal species, but multiple ecosystem components can be affected both by the environmental factors impacting, and the management targeting, focal species. These broader effects can have indirect impacts on target species through the web of interactions within ecosystems. For example, human activity can strongly alter riparian vegetation, potentially impacting both economically-important salmonids and their associated river food web. In an Olympic Peninsula river, Washington state, USA, replicated large-scale riparian vegetation manipulations implemented with the long-term (>40 yr) goal of improving salmon habitat did not affect water temperature, nutrient limitation or habitat characteristics, but reduced canopy cover, causing reduced energy input via leaf litter, increased incident solar radiation (UV and PAR) and increased algal production compared to controls. In response, benthic algae, most insect taxa, and juvenile salmonids increased in manipulated areas. Stable isotope analysis revealed a predominant contribution of algal-derived energy to salmonid diets in manipulated reaches. The experiment demonstrates that riparian management targeting salmonids strongly affects river food webs via changes in the energy base, illustrates how species-based management strategies can have unanticipated indirect effects on the target species via the associated food web, and supports ecosystem-based management approaches for restoring depleted salmonid stocks. PMID:23284786

Wootton, J Timothy

2012-01-01

327

Reducing methylmercury accumulation in the food webs of San Francisco Bay and its local watersheds  

SciTech Connect

San Francisco Bay (California, USA) and its local watersheds present an interesting case study in estuarine mercury (Hg) contamination. This review focuses on the most promising avenues for attempting to reduce methylmercury (MeHg) contamination in Bay Area aquatic food webs and identifying the scientific information that is most urgently needed to support these efforts. Concern for human exposure to MeHg in the region has led to advisories for consumption of sport fish. Striped bass from the Bay have the highest average Hg concentration measured for this species in USA estuaries, and this degree of contamination has been constant for the past 40 years. Similarly, largemouth bass in some Bay Area reservoirs have some of the highest Hg concentrations observed in the entire US. Bay Area wildlife, particularly birds, face potential impacts to reproduction based on Hg concentrations in the tissues of several Bay species. Source control of Hg is one of the primary possible approaches for reducing MeHg accumulation in Bay Area aquatic food webs. Recent findings (particularly Hg isotope measurements) indicate that the decades-long residence time of particle-associated Hg in the Bay is sufficient to allow significant conversion of even the insoluble forms of Hg into MeHg. Past inputs have been thoroughly mixed throughout this shallow and dynamic estuary. The large pool of Hg already present in the ecosystem dominates the fraction converted to MeHg and accumulating in the food web. Consequently, decreasing external Hg inputs can be expected to reduce MeHg in the food web, but it will likely take many decades to centuries before those reductions are achieved. Extensive efforts to reduce loads from the largest Hg mining source (the historic New Almaden mining district) are underway. Hg is spread widely across the urban landscape, but there are a number of key sources, source areas, and pathways that provide opportunities to capture larger quantities of Hg and reduce loads from urban runoff. Atmospheric deposition is a lower priority for source control in the Bay Area due to a combination of a lack of major local sources. Internal net production of MeHg is the dominant source of MeHg that enters the food web. Controlling internal net production is the second primary management approach, and has the potential to reduce food web MeHg in some habitats more effectively and within a much shorter time-frame. Controlling net MeHg production and accumulation in the food web of upstream reservoirs and ponds is very promising due to the many features of these ecosystems that can be manipulated. The most feasible control options in tidal marshes relate to the design of flow patterns and subhabitats in restoration projects. Options for controlling MeHg production in open Bay habitat are limited due primarily to the highly dispersed distribution of Hg throughout the ecosystem. Other changes in these habitats may also have a large influence on food web MeHg, including temperature changes due to global warming, sea level rise, food web alterations due to introduced species and other causes, and changes in sediment supply. Other options for reducing or mitigating exposure and risk include controlling bioaccumulation, cleanup of contaminated sites, and reducing other factors (e.g., habitat availability) that limit at-risk wildlife populations.

Davis, J.A., E-mail: jay@sfei.org [San Francisco Estuary Institute, 4911 Central Avenue, Richmond, CA 94804 (United States); Looker, R.E. [San Francisco Bay Regional Water Quality Control Board, 1515 Clay Street, Suite 1400, Oakland, CA 94612 (United States)] [San Francisco Bay Regional Water Quality Control Board, 1515 Clay Street, Suite 1400, Oakland, CA 94612 (United States); Yee, D. [San Francisco Estuary Institute, 4911 Central Avenue, Richmond, CA 94804 (United States)] [San Francisco Estuary Institute, 4911 Central Avenue, Richmond, CA 94804 (United States); Marvin-Di Pasquale, M. [U.S. Geological Survey, Water Resources Division/MS 480, 345 Middlefield Road, Menlo Park, CA 94025 (United States)] [U.S. Geological Survey, Water Resources Division/MS 480, 345 Middlefield Road, Menlo Park, CA 94025 (United States); Grenier, J.L. [San Francisco Estuary Institute, 4911 Central Avenue, Richmond, CA 94804 (United States)] [San Francisco Estuary Institute, 4911 Central Avenue, Richmond, CA 94804 (United States); Austin, C.M. [San Francisco Bay Regional Water Quality Control Board, 1515 Clay Street, Suite 1400, Oakland, CA 94612 (United States)] [San Francisco Bay Regional Water Quality Control Board, 1515 Clay Street, Suite 1400, Oakland, CA 94612 (United States); McKee, L.J.; Greenfield, B.K. [San Francisco Estuary Institute, 4911 Central Avenue, Richmond, CA 94804 (United States)] [San Francisco Estuary Institute, 4911 Central Avenue, Richmond, CA 94804 (United States); Brodberg, R. [California Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, 1001 I Street, Sacramento, CA 95812 (United States)] [California Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, 1001 I Street, Sacramento, CA 95812 (United States); Blum, J.D. [Department of Geological Sciences, University of Michigan, 1100 North University Avenue, Ann Arbor, MI 48109 (United States)] [Department of Geological Sciences, University of Michigan, 1100 North University Avenue, Ann Arbor, MI 48109 (United States)

2012-11-15

328

Reducing methylmercury accumulation in the food webs of San Francisco Bay and its local watersheds.  

PubMed

San Francisco Bay (California, USA) and its local watersheds present an interesting case study in estuarine mercury (Hg) contamination. This review focuses on the most promising avenues for attempting to reduce methylmercury (MeHg) contamination in Bay Area aquatic food webs and identifying the scientific information that is most urgently needed to support these efforts. Concern for human exposure to MeHg in the region has led to advisories for consumption of sport fish. Striped bass from the Bay have the highest average Hg concentration measured for this species in USA estuaries, and this degree of contamination has been constant for the past 40 years. Similarly, largemouth bass in some Bay Area reservoirs have some of the highest Hg concentrations observed in the entire US. Bay Area wildlife, particularly birds, face potential impacts to reproduction based on Hg concentrations in the tissues of several Bay species. Source control of Hg is one of the primary possible approaches for reducing MeHg accumulation in Bay Area aquatic food webs. Recent findings (particularly Hg isotope measurements) indicate that the decades-long residence time of particle-associated Hg in the Bay is sufficient to allow significant conversion of even the insoluble forms of Hg into MeHg. Past inputs have been thoroughly mixed throughout this shallow and dynamic estuary. The large pool of Hg already present in the ecosystem dominates the fraction converted to MeHg and accumulating in the food web. Consequently, decreasing external Hg inputs can be expected to reduce MeHg in the food web, but it will likely take many decades to centuries before those reductions are achieved. Extensive efforts to reduce loads from the largest Hg mining source (the historic New Almaden mining district) are underway. Hg is spread widely across the urban landscape, but there are a number of key sources, source areas, and pathways that provide opportunities to capture larger quantities of Hg and reduce loads from urban runoff. Atmospheric deposition is a lower priority for source control in the Bay Area due to a combination of a lack of major local sources. Internal net production of MeHg is the dominant source of MeHg that enters the food web. Controlling internal net production is the second primary management approach, and has the potential to reduce food web MeHg in some habitats more effectively and within a much shorter time-frame. Controlling net MeHg production and accumulation in the food web of upstream reservoirs and ponds is very promising due to the many features of these ecosystems that can be manipulated. The most feasible control options in tidal marshes relate to the design of flow patterns and subhabitats in restoration projects. Options for controlling MeHg production in open Bay habitat are limited due primarily to the highly dispersed distribution of Hg throughout the ecosystem. Other changes in these habitats may also have a large influence on food web MeHg, including temperature changes due to global warming, sea level rise, food web alterations due to introduced species and other causes, and changes in sediment supply. Other options for reducing or mitigating exposure and risk include controlling bioaccumulation, cleanup of contaminated sites, and reducing other factors (e.g., habitat availability) that limit at-risk wildlife populations. PMID:23122771

Davis, J A; Looker, R E; Yee, D; Marvin-Di Pasquale, M; Grenier, J L; Austin, C M; McKee, L J; Greenfield, B K; Brodberg, R; Blum, J D

2012-11-01

329

Spatial Guilds in the Serengeti Food Web Revealed by a Bayesian Group Model  

PubMed Central

Food webs, networks of feeding relationships in an ecosystem, provide fundamental insights into mechanisms that determine ecosystem stability and persistence. A standard approach in food-web analysis, and network analysis in general, has been to identify compartments, or modules, defined by many links within compartments and few links between them. This approach can identify large habitat boundaries in the network but may fail to identify other important structures. Empirical analyses of food webs have been further limited by low-resolution data for primary producers. In this paper, we present a Bayesian computational method for identifying group structure using a flexible definition that can describe both functional trophic roles and standard compartments. We apply this method to a newly compiled plant-mammal food web from the Serengeti ecosystem that includes high taxonomic resolution at the plant level, allowing a simultaneous examination of the signature of both habitat and trophic roles in network structure. We find that groups at the plant level reflect habitat structure, coupled at higher trophic levels by groups of herbivores, which are in turn coupled by carnivore groups. Thus the group structure of the Serengeti web represents a mixture of trophic guild structure and spatial pattern, in contrast to the standard compartments typically identified. The network topology supports recent ideas on spatial coupling and energy channels in ecosystems that have been proposed as important for persistence. Furthermore, our Bayesian approach provides a powerful, flexible framework for the study of network structure, and we believe it will prove instrumental in a variety of biological contexts. PMID:22219719

Baskerville, Edward B.; Dobson, Andy P.; Bedford, Trevor; Allesina, Stefano; Anderson, T. Michael; Pascual, Mercedes

2011-01-01

330

Methylmercury enters an aquatic food web through acidophilic microbial mats in Yellowstone National Park, Wyoming  

USGS Publications Warehouse

Summary Microbial mats are a visible and abundant life form inhabiting the extreme environments in Yellowstone National Park (YNP), WY, USA. Little is known of their role in food webs that exist in the Park's geothermal habitats. Eukaryotic green algae associated with a phototrophic green/purple Zygogonium microbial mat community that inhabits low-temperature regions of acidic (pH ??? 3.0) thermal springs were found to serve as a food source for stratiomyid (Diptera: Stratiomyidae) larvae. Mercury in spring source water was taken up and concentrated by the mat biomass. Monomethylmercury compounds (MeHg +), while undetectable or near the detection limit (0.025 ng l -1) in the source water of the springs, was present at concentrations of 4-7 ng g-1 dry weight of mat biomass. Detection of MeHg + in tracheal tissue of larvae grazing the mat suggests that MeHg+ enters this geothermal food web through the phototrophic microbial mat community. The concentration of MeHg+ was two to five times higher in larval tissue than mat biomass indicating MeHg+ biomagnification occurred between primary producer and primary consumer trophic levels. The Zygogonium mat community and stratiomyid larvae may also play a role in the transfer of MeHg+ to species in the food web whose range extends beyond a particular geothermal feature of YNP. ?? 2008 The Authors. Journal compilation ?? 2008 Society for Applied Microbiology and Blackwell Publishing Ltd.

Boyd, E.S.; King, S.; Tomberlin, J.K.; Nordstrom, D.K.; Krabbenhoft, D.P.; Barkay, T.; Geesey, G.G.

2009-01-01

331

Density outbursts in a food web model with a closed nutrient cycle  

NASA Astrophysics Data System (ADS)

A spatial three level food web model with a closed nutrient cycle is presented and analyzed via Monte Carlo simulations. The food web consists of three trophic levels. The basal level species (called resources, R) corresponds to primary producers in real ecosystems. The species at an intermediate level (consumers, C) relates to herbivores. It feeds on the resources. The consumers themselves constitute food for the top level species (predators, P), which corresponds to carnivores. The remains of the consumers and predators (detritus, D) provide nutrient for the resources. The time evolution of the model reveals two asymptotic states: an absorbing one with all species being extinct, and a coexisting one, in which concentrations of all species are non-zero. There are two possible ways for the system to reach the absorbing state. In some cases the densities increase very quickly at the beginning of a simulation and then decline slowly and almost monotonically. In others, well pronounced peaks in the R, C and D densities appear regularly before the extinction. Those peaks correspond to density outbursts (waves) traveling through the system. We investigate the mechanisms leading to the waves. In particular, we show that the percolation of the detritus (i.e. the accumulation of nutrients) is necessary for the emergence of the waves. Moreover, our results corroborate the hypothesis that top-level predators play an essential role in maintaining the stability of a food web (top-down control).

Szwabi?ski, Janusz

2013-09-01

332

Methylmercury enters an aquatic food web through acidophilic microbial mats in Yellowstone National Park, Wyoming.  

PubMed

Microbial mats are a visible and abundant life form inhabiting the extreme environments in Yellowstone National Park (YNP), WY, USA. Little is known of their role in food webs that exist in the Park's geothermal habitats. Eukaryotic green algae associated with a phototrophic green/purple Zygogonium microbial mat community that inhabits low-temperature regions of acidic (pH approximately 3.0) thermal springs were found to serve as a food source for stratiomyid (Diptera: Stratiomyidae) larvae. Mercury in spring source water was taken up and concentrated by the mat biomass. Monomethylmercury compounds (MeHg(+)), while undetectable or near the detection limit (0.025 ng l(-1)) in the source water of the springs, was present at concentrations of 4-7 ng g(-1) dry weight of mat biomass. Detection of MeHg(+) in tracheal tissue of larvae grazing the mat suggests that MeHg(+) enters this geothermal food web through the phototrophic microbial mat community. The concentration of MeHg(+) was two to five times higher in larval tissue than mat biomass indicating MeHg(+) biomagnification occurred between primary producer and primary consumer trophic levels. The Zygogonium mat community and stratiomyid larvae may also play a role in the transfer of MeHg(+) to species in the food web whose range extends beyond a particular geothermal feature of YNP. PMID:19170726

Boyd, Eric S; King, Susan; Tomberlin, Jeffery K; Nordstrom, D Kirk; Krabbenhoft, David P; Barkay, Tamar; Geesey, Gill G

2009-04-01

333

Food-web structure in low- and high-dimensional trophic niche spaces  

PubMed Central

A question central to modelling and, ultimately, managing food webs concerns the dimensionality of trophic niche space, that is, the number of independent traits relevant for determining consumer–resource links. Food-web topologies can often be interpreted by assuming resource traits to be specified by points along a line and each consumer's diet to be given by resources contained in an interval on this line. This phenomenon, called intervality, has been known for 30 years and is widely acknowledged to indicate that trophic niche space is close to one-dimensional. We show that the degrees of intervality observed in nature can be reproduced in arbitrary-dimensional trophic niche spaces, provided that the processes of evolutionary diversification and adaptation are taken into account. Contrary to expectations, intervality is least pronounced at intermediate dimensions and steadily improves towards lower- and higher-dimensional trophic niche spaces. PMID:20462875

Rossberg, Axel G.; Brännström, Åke; Dieckmann, Ulf

2010-01-01

334

Impact of biodiversity loss on production in complex marine food webs mitigated by prey-release  

PubMed Central

Public concern over biodiversity loss is often rationalized as a threat to ecosystem functioning, but biodiversity-ecosystem functioning (BEF) relations are hard to empirically quantify at large scales. We use a realistic marine food-web model, resolving species over five trophic levels, to study how total fish production changes with species richness. This complex model predicts that BEF relations, on average, follow simple Michaelis–Menten curves when species are randomly deleted. These are shaped mainly by release of fish from predation, rather than the release from competition expected from simpler communities. Ordering species deletions by decreasing body mass or trophic level, representing ‘fishing down the food web’, accentuates prey-release effects and results in unimodal relationships. In contrast, simultaneous unselective harvesting diminishes these effects and produces an almost linear BEF relation, with maximum multispecies fisheries yield at ?40% of initial species richness. These findings have important implications for the valuation of marine biodiversity. PMID:25799523

Fung, Tak; Farnsworth, Keith D.; Reid, David G.; Rossberg, Axel G.

2015-01-01

335

Mercury and nitrogen isotope in a marine species from a tropical coastal food web.  

PubMed

The present study raised the hypothesis that the trophic status in a tropical coastal food web from southeastern Brazil can be measured by the relation between total mercury (THg) and nitrogen isotope (?(15)N) in their components. The analysed species were grouped into six trophic positions: primary producer (phytoplankton), primary consumer (zooplankton), consumer 1 (omnivore shrimp), consumer 2 (pelagic carnivores represented by squid and fish species), consumer 3 (demersal carnivores represented by fish species) and consumer 4 (pelagic-demersal top carnivore represented by the fish Trichiurus lepturus). The values of THg, ?(15)N, and trophic level (TLv) increased significantly from primary producer toward top carnivore. Our data regarding trophic magnification (6.84) and biomagnification powers (0.25 for ?(15)N and 0.83 for TLv) indicated that Hg biomagnification throughout trophic positions is high in this tropical food web, which could be primarily related to the quality of the local water. PMID:21858737

Di Beneditto, Ana Paula Madeira; Bittar, Vanessa Trindade; Camargo, Plínio Barbosa; Rezende, Carlos Eduardo; Kehrig, Helena Amaral

2012-02-01

336

Impact of biodiversity loss on production in complex marine food webs mitigated by prey-release.  

PubMed

Public concern over biodiversity loss is often rationalized as a threat to ecosystem functioning, but biodiversity-ecosystem functioning (BEF) relations are hard to empirically quantify at large scales. We use a realistic marine food-web model, resolving species over five trophic levels, to study how total fish production changes with species richness. This complex model predicts that BEF relations, on average, follow simple Michaelis-Menten curves when species are randomly deleted. These are shaped mainly by release of fish from predation, rather than the release from competition expected from simpler communities. Ordering species deletions by decreasing body mass or trophic level, representing 'fishing down the food web', accentuates prey-release effects and results in unimodal relationships. In contrast, simultaneous unselective harvesting diminishes these effects and produces an almost linear BEF relation, with maximum multispecies fisheries yield at ?40% of initial species richness. These findings have important implications for the valuation of marine biodiversity. PMID:25799523

Fung, Tak; Farnsworth, Keith D; Reid, David G; Rossberg, Axel G

2015-01-01

337

North Atlantic Oscillation synchronizes food-web interactions in central European lakes.  

PubMed Central

A regular and distinct feature of seasonal plankton succession in temperate lakes is the early summer period of algal suppression by herbivores, i.e. the clear water phase. Within the last 30 years the timing of this food-web interaction between algae and herbivores has advanced on average by approximately two weeks in central European lakes due to faster population growth of herbivores in warmer water. Trend and inter-annual variability in clear water timing were strongly related to the climate dynamics of the North Atlantic, i.e. the North Atlantic Oscillation (NAO). Due to its large-scale effects, the NAO synchronized plankton succession in central European lakes, causing a striking temporal coherence of a food-web interaction over several hundreds of kilometers. PMID:11886627

Straile, Dietmar

2002-01-01

338

Highly resolved early Eocene food webs show development of modern trophic structure after the end-Cretaceous extinction.  

PubMed

Generalities of food web structure have been identified for extant ecosystems. However, the trophic organization of ancient ecosystems is unresolved, as prior studies of fossil webs have been limited by low-resolution, high-uncertainty data. We compiled highly resolved, well-documented feeding interaction data for 700 taxa from the 48 million-year-old latest early Eocene Messel Shale, which contains a species assemblage that developed after an interval of protracted environmental and biotal change during and following the end-Cretaceous extinction. We compared the network structure of Messel lake and forest food webs to extant webs using analyses that account for scale dependence of structure with diversity and complexity. The Messel lake web, with 94 taxa, displays unambiguous similarities in structure to extant webs. While the Messel forest web, with 630 taxa, displays differences compared to extant webs, they appear to result from high diversity and resolution of insect-plant interactions, rather than substantive differences in structure. The evidence presented here suggests that modern trophic organization developed along with the modern Messel biota during an 18 Myr interval of dramatic post-extinction change. Our study also has methodological implications, as the Messel forest web analysis highlights limitations of current food web data and models. PMID:24648225

Dunne, Jennifer A; Labandeira, Conrad C; Williams, Richard J

2014-05-01

339

Highly resolved early Eocene food webs show development of modern trophic structure after the end-Cretaceous extinction  

PubMed Central

Generalities of food web structure have been identified for extant ecosystems. However, the trophic organization of ancient ecosystems is unresolved, as prior studies of fossil webs have been limited by low-resolution, high-uncertainty data. We compiled highly resolved, well-documented feeding interaction data for 700 taxa from the 48 million-year-old latest early Eocene Messel Shale, which contains a species assemblage that developed after an interval of protracted environmental and biotal change during and following the end-Cretaceous extinction. We compared the network structure of Messel lake and forest food webs to extant webs using analyses that account for scale dependence of structure with diversity and complexity. The Messel lake web, with 94 taxa, displays unambiguous similarities in structure to extant webs. While the Messel forest web, with 630 taxa, displays differences compared to extant webs, they appear to result from high diversity and resolution of insect–plant interactions, rather than substantive differences in structure. The evidence presented here suggests that modern trophic organization developed along with the modern Messel biota during an 18 Myr interval of dramatic post-extinction change. Our study also has methodological implications, as the Messel forest web analysis highlights limitations of current food web data and models. PMID:24648225

Dunne, Jennifer A.; Labandeira, Conrad C.; Williams, Richard J.

2014-01-01

340

Food web analysis of southern California coastal wetlands using multiple stable isotopes  

Microsoft Academic Search

Carbon, nitrogen, and sulfur stable isotopes were used to characterize the food webs (i.e., sources of carbon and trophic\\u000a status of consumers) in Tijuana Estuary and San Dieguito Lagoon. Producer groups were most clearly differentiated by carbon,\\u000a then by sulfur, and least clearly by nitrogen isotope measurements. Consumer 15N isotopic enrichment suggested that there are four trophic levels in the

Thomas J. Kwak; Joy B. Zedler

1997-01-01

341

Current opinions: Zeros in host–parasite food webs: Are they real??  

PubMed Central

As the data have poured in, and the number of published food webs containing parasites has increased, questions have been raised as to why free-living species consistently outnumber parasites, even though most general reviews on the subject of host:parasite species richness suggest the contrary. Here, I describe this pattern as it exists in the literature, posit both real and artifactual sources of these findings, and suggest ways that we might interpret existing parasite-inclusive food webs. In large part, the reporting of free-living species devoid of any associated parasites (termed here in the coding of food web matrices as “zeros”) is a consequence of either sampling issues or the intent of the study. However, there are also several powerful explanatory features that validate real cases of this phenomenon. Some hosts appear to authentically lack parasitism in portions of their geographic ranges, and parasites are often lost from systems that are either in early phases of community re-colonization or are compromised by environmental perturbation. Additionally, multi-stage parasite life cycles and broad host spectra allow some parasite species to partially saturate systems without providing a corresponding increase in parasite species richness, leading to low parasite species richness values relative to the free-living community. On the whole, the existing published food webs are sufficient to, at least in principle, determine basic patterns and pathways associated with parasite establishment and persistence in free-living communities because (1) for the purpose of those features, species rarity is roughly analogous to absence and (2) the existing data seem to suggest that the addition of more parasite taxa would reinforce the patterns already observed. This is particularly true for helminth parasites, in which our understanding and the resolution of our work is most robust. PMID:24533341

Rossiter, Wayne

2013-01-01

342

Ant-Hemipteran Mutualisms: Keystone Interactions that Alter Food Web Dynamics and Influence Plant Fitness  

Microsoft Academic Search

Predicting the direct and indirect effects of natural enemies on herbivorous insects in species-rich, highly connected arthropod\\u000a food webs can be extremely difficult. Community ecologists developed the keystone species concept to help simplify this task.\\u000a Keystone species are species that have disproportionately large effects on the abundance of many interacting species in a\\u000a community. Keystone species, however, can be difficult

Micky D. Eubanks; John D. Styrsky

343

Trait-Mediated Indirect Interactions in a Simple Aquatic Food Web  

Microsoft Academic Search

This investigation examines the role of trait-mediated indirect interactions in a simple aquatic food web. We conducted the experiments in cattle watering tanks in order to establish whether competitive and predator-prey interactions between two species are affected by other species in the system; i.e., are pairwise interaction strengths affected by the background species assemblage? We examined the survival and growth

Scott D. Peacor; Earl E. Werner

1997-01-01

344

Use of Metabolic Inhibitors to Characterize Ecological Interactions in an Estuarine Microbial Food Web  

Microsoft Academic Search

  Understanding microbial food web dynamics is complicated by the multitude of competitive or interdependent trophic interactions\\u000a involved in material and energy flow. Metabolic inhibitors can be used to gain information on the relative importance of trophic\\u000a pathways by uncoupling selected microbial components and examining the net effect on ecosystem structure and function. A eukaryotic\\u000a growth inhibitor (cycloheximide), a prokaryotic growth

M. E. DeLorenzo; A. J. Lewitus; G. I. Scott; P. E. Ross

2001-01-01

345

Benthic and Pelagic Pathways of Methylmercury Bioaccumulation in Estuarine Food Webs of the Northeast United States  

PubMed Central

Methylmercury (MeHg) is a contaminant of global concern that bioaccumulates and bioamagnifies in marine food webs. Lower trophic level fauna are important conduits of MeHg from sediment and water to estuarine and coastal fish harvested for human consumption. However, the sources and pathways of MeHg to these coastal fisheries are poorly known particularly the potential for transfer of MeHg from the sediment to biotic compartments. Across a broad gradient of human land impacts, we analyzed MeHg concentrations in food webs at ten estuarine sites in the Northeast US (from the Hackensack Meadowlands, NJ to the Gulf of Maine). MeHg concentrations in water column particulate material, but not in sediments, were predictive of MeHg concentrations in fish (killifish and Atlantic silversides). Moreover, MeHg concentrations were higher in pelagic fauna than in benthic-feeding fauna suggesting that MeHg delivery to the water column from methylation sites from within or outside of the estuary may be an important driver of MeHg bioaccumulation in estuarine pelagic food webs. In contrast, bulk sediment MeHg concentrations were only predictive of concentrations of MeHg in the infaunal worms. Our results across a broad gradient of sites demonstrate that the pathways of MeHg to lower trophic level estuarine organisms are distinctly different between benthic deposit feeders and forage fish. Thus, even in systems with contaminated sediments, transfer of MeHg into estuarine food webs maybe driven more by the efficiency of processes that determine MeHg input and bioavailability in the water column. PMID:24558491

Chen, Celia Y.; Borsuk, Mark E.; Bugge, Deenie M.; Hollweg, Terill; Balcom, Prentiss H.; Ward, Darren M.; Williams, Jason; Mason, Robert P.

2014-01-01

346

Selection of an Aquatic Indicator Species to Monitor Organic Contaminants in Trophically Simple Lotic Food Webs  

Microsoft Academic Search

.   A four-step procedure was used to identify an aquatic macroinvertebrate with which to monitor organic contaminant burdens\\u000a in trophically simple lake food webs of Alberta, Canada. We identified leeches (Oligochaeta: Hirudinea) as the potential indicator\\u000a assemblage (Step 1), and then documented their abundance and distribution in 16 lakes to identify a species-level bioindicator\\u000a (Step 2). The latter two steps

G. J. Scrimgeour; D. Wicklum; S. D. Pruss

1998-01-01

347

Propagation of Cascades in Complex Networks: From Supply Chains to Food Webs  

E-print Network

A general theory of top-down cascades in complex networks is described which explains two similar types of perturbation amplifications in the complex networks of business supply chains (the `bullwhip effect') and ecological food webs (trophic cascades). The dependence of the strength of the effects on the interaction strength and covariance in the dynamics as well as the graph structure allows both explanation and prediction of widely recognized effects in each type of system.

Smith, Reginald D

2011-01-01

348

Simulating the effects of biomanipulation on the food web of Lake Ringsjön  

Microsoft Academic Search

A dynamic, process-oriented, deterministic and phosphorus-based model was developed to simulate the food web dynamics of Lake Ringsjön, in particular the long-term effects of biomanipulation in terms of reduction of omnivorous fish. The model contains 14 state variables, each with a differential equation describing sources and sinks of phosphorus. The state variables encompass piscivorous and omnivorous fish, zooplankton, phytoplankton, sediment

Anders Persson; Andreas Barkman; Lars-Anders Hansson

1999-01-01

349

Bottom-up effects of species diversity on the functioning and stability of food webs.  

PubMed

1. The importance of species diversity for the stability of populations, communities and ecosystem functions is a central question in ecology. 2. Biodiversity experiments have shown that diversity can impact both the average and variability of stocks and rates at these levels of ecological organization in single trophic-level ecosystems. Whether these impacts hold in food webs and across trophic levels is still unclear. 3. We asked whether resource species diversity, community composition and consumer feeding selectivity in planktonic food webs impact the stability of resource or consumer populations, community biomass and ecosystem functions. We also tested the relative importance of resource diversity and community composition. 4. We found that resource diversity negatively affected resource population stability, but had no effect on consumer population stability, regardless of the consumer's feeding selectivity. Resource diversity had positive effects on most ecosystem functions and their stability, including primary production, resource biomass and particulate carbon, nitrogen and phosphorus concentrations. 5. Community composition, however, generally explained more variance in population, community and ecosystem properties than species diversity per se. This result points to the importance of the outcomes of particular species interactions and individual species' effect traits in determining food web properties and stability. 6. Among the stabilizing mechanisms tested, an increase in the average resource community biomass with increasing resource diversity had the greatest positive impact on stability. 7. Our results indicate that resource diversity and composition are generally important for the functioning and stability of whole food webs, but do not have straightforward impacts on consumer populations. PMID:22325003

Narwani, Anita; Mazumder, Asit

2012-05-01

350

Longer and Less Overlapping Food Webs in Anthropogenically Disturbed Marine Ecosystems: Confirmations from the Past  

PubMed Central

The human exploitation of marine resources is characterised by the preferential removal of the largest species. Although this is expected to modify the structure of food webs, we have a relatively poor understanding of the potential consequences of such alteration. Here, we take advantage of a collection of ancient consumer tissues, using stable isotope analysis and SIBER to assess changes in the structure of coastal marine food webs in the South-western Atlantic through the second half of the Holocene as a result of the sequential exploitation of marine resources by hunter-gatherers, western sealers and modern fishermen. Samples were collected from shell middens and museums. Shells of both modern and archaeological intertidal herbivorous molluscs were used to reconstruct changes in the stable isotopic baseline, while modern and archaeological bones of the South American sea lion Otaria flavescens, South American fur seal Arctocephalus australis and Magellanic penguin Spheniscus magellanicus were used to analyse changes in the structure of the community of top predators. We found that ancient food webs were shorter, more redundant and more overlapping than current ones, both in northern-central Patagonia and southern Patagonia. These surprising results may be best explained by the huge impact of western sealing on pinnipeds during the fur trade period, rather than the impact of fishing on fish populations. As a consequence, the populations of pinnipeds at the end of the sealing period were likely well below the ecosystem's carrying capacity, which resulted in a release of intraspecific competition and a shift towards larger and higher trophic level prey. This in turn led to longer and less overlapping food webs. PMID:25076042

Saporiti, Fabiana; Bearhop, Stuart; Silva, Laura; Vales, Damián G.; Zenteno, Lisette; Crespo, Enrique A.; Aguilar, Alex; Cardona, Luis

2014-01-01

351

Food web model of the Upper Paraná River Floodplain: description and aggregation effects  

Microsoft Academic Search

To describe the Upper Paraná River Floodplain (the last non-dammed stretch of the Paraná River, Brazil) a food web model was quantified using ECOPATH. The modeled ecosystem showed maturity because of the total primary production\\/total respiration ratio (close to 2), Finn’s cycling index (7%) and overhead (65%). The first model elaborated had 40 compartments\\/groups, but its transfer efficiencies among trophic

Ronaldo Angelini; Angelo Antonio Agostinho

2005-01-01

352

Resource Pulses and Spatial Subsidies in Ozark Karst Springs: Effects on Community Structure and Food Webs  

E-print Network

x LIST OF TABLES Table Page 1. General Characteristics of Study Springs………………………………...….32 2. Summary of the summer sampling physicochemical measures…….....…….36 3. Summary of the winter sampling physicochemical measures... dependent on allochthonous organic matter (e.g. Lindegaard 1995). Although the relative importance of autochthonous production has been noted in rivers (e.g., Thorp and Delong 2002), the general consensus is that food webs in forested headwaters...

Carroll, Teresa Mae

2009-06-23

353

Stable isotopes and organochlorines in the food webs of Lakes Baikal and Superior  

SciTech Connect

Quantifying organochlorine biomagnification in aquatic ecosystems is traditionally accomplished by assigning discreet trophic levels, which does not adequately describe feeding relationships except in well defined systems. {delta}{sup 15}N and {delta}{sup 13}C, particularly {delta}{sup 15}N values, measured in aquatic food webs provide additional information on trophic position such that it may be treated as a continuous variable. To evaluate this technique, samples were collected from the pelagic zone of Lake Baikal in August and September, 1993 for organochlorine (PCBs, DDTs, chlordanes and HCHS) and stable isotope ({delta}{sup 13}C and {delta}{sup 15}N) analyzed. These included high volume water samples, seston, net plankton, two species of pelagic sculpin Comephorus dybowskii, C. baikalensis, the omul, (Coregonus autumnalis migratorious), and 9 seal (Phoca siberica) samples of known sex and age. Food web samples from Lake Superior will be collected in June, 1994 to include benthic infauna, sculpins, Mysis and surface phytoplankton and zooplankton. Results from this study will provide a comparison of organochlorine trophodynamics between a system with a predominant pelagic food web (Lake Baikal) to one with substantial benthic/pelagic coupling (Lake Superior).

Kucklick, J.R.; Baker, J.E. [Univ. of Maryland System, Solomons, MD (United States). Chesapeake Biological Lab.; Ostrom, N.E.; Ostrom, P.H. [Michigan State Univ., East Lansing, MI (United States). Dept. of Geological Sciences; Lee, D.S. [Univ. of Connecticut, Groton, CT (United States)

1994-12-31

354

Using food web dominator trees to catch secondary extinctions in action  

PubMed Central

In ecosystems, a single extinction event can give rise to multiple ‘secondary’ extinctions. Conservation effort would benefit from tools that help forecast the consequences of species removal. One such tool is the dominator tree, a graph-theoretic algorithm that when applied to food webs unfolds their complex architecture, yielding a simpler topology made of linear pathways that are essential for energy delivery. Each species along these chains is responsible for passing energy to the taxa that follow it and, as such, it is indispensable for their survival. To assess the predictive potential of the dominator tree, we compare its predictions with the effects that followed the collapse of the capelin (Mallotus villosus) in the Barents Sea ecosystem. To this end, we first compiled a food web for this ecosystem, then we built the corresponding dominator tree and, finally, we observed whether model predictions matched the empirical observations. This analysis shows the potential and the drawbacks of the dominator trees as a tool for understanding the causes and consequences of extinctions in food webs. PMID:19451123

Bodini, Antonio; Bellingeri, Michele; Allesina, Stefano; Bondavalli, Cristina

2009-01-01

355

Tracing Fluxes Of Aquatic Production And Contaminants Into Terrestrial Food Webs With Nitrogen Stable Isotopes  

NASA Astrophysics Data System (ADS)

Biomagnifying contaminants such as mercury can be transported and redistributed across the watershed by streams and rivers. Their fate and effects on consumers depend on food web transfer both within and between aquatic and terrestrial ecosystems. The Truckee River (Ca/Ne) is heavily contaminated by Hg originating from century-old upstream mining operations. We used nitrogen stable isotope analysis to trace the incorporation of Hg transported by the Truckee and transferred by emerging aquatic insects into the riparian food web. N-isotope ratios and Hg of aquatic primary consumers were significantly elevated compared to that of terrestrial arthropods (13.3 vs 5.6 % and 110 vs 17 ngg-1). Estimates of dependence on aquatics in 16 riparian passerine bird species based on blood delta 15N ranged between 0.0 and 0.95 and were significantly related to Hg in blood. Similar correlations between Hg and delta 15N measured in tail tips of western fence lizard (Sceloporus occidentalis) collected at increasing distances from the river were observed. High inter-individual variation in bird Hg was highly correlated with delta 15N. These results show how stable isotopes and contaminant fluxes can reveal important food web linkages across aquatic/terrestrial ecotones.

Rivard, A.; Cabana, G.; Rainey, W.; Power, M.

2005-05-01

356

Habitat modification alters the structure of tropical host-parasitoid food webs.  

PubMed

Global conversion of natural habitats to agriculture has led to marked changes in species diversity and composition. However, it is less clear how habitat modification affects interactions among species. Networks of feeding interactions (food webs) describe the underlying structure of ecological communities, and might be crucially linked to their stability and function. Here, we analyse 48 quantitative food webs for cavity-nesting bees, wasps and their parasitoids across five tropical habitat types. We found marked changes in food-web structure across the modification gradient, despite little variation in species richness. The evenness of interaction frequencies declined with habitat modification, with most energy flowing along one or a few pathways in intensively managed agricultural habitats. In modified habitats there was a higher ratio of parasitoid to host species and increased parasitism rates, with implications for the important ecosystem services, such as pollination and biological control, that are performed by host bees and wasps. The most abundant parasitoid species was more specialized in modified habitats, with reduced attack rates on alternative hosts. Conventional community descriptors failed to discriminate adequately among habitats, indicating that perturbation of the structure and function of ecological communities might be overlooked in studies that do not document and quantify species interactions. Altered interaction structure therefore represents an insidious and functionally important hidden effect of habitat modification by humans. PMID:17215842

Tylianakis, Jason M; Tscharntke, Teja; Lewis, Owen T

2007-01-11

357

Carbon fluxes through food webs of the eastern equatorial Pacific: an inverse approach  

NASA Astrophysics Data System (ADS)

We used inverse and network analyses to examine food web interactions at 0°, 140°W during EqPac time-series cruises in March-April and October 1992. Our goal was to characterize carbon flows and trophic transfers while synthesizing the available information into a complete picture of ecosystem dynamics. The inverse approach allowed us to trace the pathway of fixed carbon through a representative food web and to characterize the role of various food web components in the recycling of carbon within, and export of carbon from, the euphotic zone. The key findings of these analyses were: (1) primary production of the larger phytoplankton size classes was most often dominated by the prymnesiophytes and pelagophytes and not by the diatoms, (2) picoplankton primary production was not always balanced by protozoan and microzooplankton grazing, despite conventional views of balanced microbial producer/grazer interactions in this system, (3) the picoplankton played an important direct + indirect role in the export of carbon from the euphotic zone through a pathway involving production of detritus from picoplankton carbon and subsequent grazing of this picoplankton-based detritus by the mesozooplankton, and (4) export of carbon through consumption of mesozooplankton by higher trophic levels was of the same magnitude as DOC export (9-25 mmol C m -2 d -1), yet this pathway is rarely considered in equatorial carbon balances.

Richardson, Tammi L.; Jackson, George A.; Ducklow, Hugh W.; Roman, Michael R.

2004-09-01

358

Perfluorinated and polyfluorinated compounds in lake food webs from the canadian high arctic.  

PubMed

Per- and polyfluorinated alkyl substances (PFASs) enter Arctic lakes through long-range atmospheric transport and local contamination, but their behavior in aquatic food webs at high latitudes is poorly understood. This study compared the concentrations of perfluorocarboxylates, perfluorosulfonates, and fluorotelomer sulfonates (FTS) in biotic and abiotic samples from six high Arctic lakes near Resolute Bay, Nunavut, Canada. Two of these lakes are known to be locally contaminated by a small airport and Arctic char (Salvelinus alpinus) from these lakes had over 100 times higher total [PFAS] when compared to fish from neighboring lakes. Perfluorononanoate (PFOA) and perfluorooctanesulfonate (PFOS) dominated in char, benthic chironomids (their main prey), and sediments, while pelagic zooplankton and water were dominated by lower chain acids and perfluorodecanesulfonate (PFDS). This study also provides the first measures of perfluoroethylcyclohexanesulfonate (PFECHS) and FTS compounds in water, sediment, juvenile char, and benthic invertebrates from lakes in the high Arctic. Negative relationships between [PFAS] and ?(15)N values (indicative of trophic position) within these food webs indicated no biomagnification. Overall, these results suggest that habitat use and local sources of contamination, but not trophic level, are important determinants of [PFAS] in biota from freshwater food webs in the Canadian Arctic. PMID:25604756

Lescord, Gretchen L; Kidd, Karen A; De Silva, Amila O; Williamson, Mary; Spencer, Christine; Wang, Xiaowa; Muir, Derek C G

2015-03-01

359

On the interplay of speciation and dispersal: an evolutionary food web model in space.  

PubMed

We introduce an evolutionary metacommunity of multitrophic food webs on several habitats coupled by migration. In contrast to previous studies that focus either on evolutionary or on spatial aspects, we include both and investigate the interplay between them. Locally, the species emerge, interact and go extinct according to the rules of the well-known evolutionary food web model proposed by Loeuille and Loreau (2005). Additionally, species are able to migrate between the habitats. With random migration, we are able to reproduce common trends in diversity-dispersal relationships: Regional diversity decreases with increasing migration rates, whereas local diversity can increase in case of a low level of dispersal. Moreover, we find that the total biomasses in the different patches become similar even when species composition remains different. With adaptive migration, we observe species compositions that differ considerably between patches and contain species that are descendant from ancestors on both patches. This result indicates that the combination of spatial aspects and evolutionary processes affects the structure of food webs in different ways than each of them alone. PMID:25446710

Allhoff, Korinna T; Weiel, Eva Marie; Rogge, Tobias; Drossel, Barbara

2015-02-01

360

Evolution mediates the effects of apex predation on aquatic food webs  

PubMed Central

Ecological and evolutionary mechanisms are increasingly thought to shape local community dynamics. Here, I evaluate if the local adaptation of a meso-predator to an apex predator alters local food webs. The marbled salamander (Ambystoma opacum) is an apex predator that consumes both the spotted salamander (Ambystoma maculatum) and shared zooplankton prey. Common garden experiments reveal that spotted salamander populations which co-occur with marbled salamanders forage more intensely than those that face other predator species. These foraging differences, in turn, alter the diversity, abundance and composition of zooplankton communities in common garden experiments and natural ponds. Locally adapted spotted salamanders exacerbate prey biomass declines associated with apex predation, but dampen the top-down effects of apex predation on prey diversity. Countergradient selection on foraging explains why locally adapted spotted salamanders exacerbate prey biomass declines. The two salamander species prefer different prey species, which explains why adapted spotted salamanders buffer changes in prey composition owing to apex predation. Results suggest that local adaptation can strongly mediate effects from apex predation on local food webs. Community ecologists might often need to consider the evolutionary history of populations to understand local diversity patterns, food web dynamics, resource gradients and their responses to disturbance. PMID:23720548

Urban, Mark C.

2013-01-01

361

An isotopic investigation of mercury accumulation in terrestrial food webs adjacent to an Arctic seabird colony.  

PubMed

At Cape Vera (Devon Island, Nunavut, Canada), a seabird colony of northern fulmars (Fulmarus glacialis) congregates and releases nutrients through the deposition of guano to the coastal terrestrial environment, thus creating nutrient-fertilized habitats important to insects, birds, and mammals. Here we determined whether mercury was similarly enriched in various terrestrial food web components in this High Arctic coastal ecosystem due to seabird inputs. Stable isotopes (delta(15)N, delta(13)C) were used to identify trophic linkages and possible routes of contaminant transfer in the food web. Values of delta(15)N were significantly higher in lichens and certain plants collected closer to the bird colony, demonstrating a gradient of seabird influence, and were higher at Cape Vera than our reference site at Cape Herschel, on eastern Ellesmere Island, an area relatively unaffected by seabirds. In contrast, delta(13)C showed little variation among terrestrial species, suggesting minimal influence by seabirds. Concentrations of total mercury (THg) in primary producers and phyto/zooplankton were not significantly correlated with distance from the seabird colony or delta(15)N values, and were similar to other taxa from the High Arctic. Our results provide novel data on THg in several Arctic taxa where concentrations have not been reported previously. Moreover, the analyses indicate that delta(15)N is significantly enriched in the adjacent environment by guano fertilization, but our study was unable to show an enrichment of THg and delta(13)C in the terrestrial food web near the seabird colony. PMID:20153017

Choy, Emily S; Gauthier, Martine; Mallory, Mark L; Smol, John P; Douglas, Marianne S V; Lean, David; Blais, Jules M

2010-03-15

362

Mercury Bioavailability and Bioaccumulation in Estuarine Food Webs in the Gulf of Maine  

PubMed Central

Marine food webs are important links between Hg in the environment and human exposure via consumption of fish. Estuaries contain sediment repositories of Hg and are also critical habitat for marine fish and shellfish species consumed by humans. MeHg biotransfers from sites of production in estuarine sediments to higher trophic levels via both benthic and pelagic pathways. In this study, we investigated the potential for Hg biotransfer to estuarine food webs across a Hg contamination gradient in the Gulf of Maine. Despite the variation in sediment Hg concentrations across sites (>100 fold), Hg concentrations in biota ranged by only 2–4 fold for each species across sites. Sediment contamination alone explained some variation in Hg and MeHg concentrations in biota across sites. However, biogeochemical and ecological factors also explained significant variation in Hg bioaccumulation across species. Contaminated sites had higher total organic carbon concentrations in sediments, which related to a decrease in Hg bioaccumulation (measured as biota-sediment concentration factors, BSCF). Moreover, concentrations of MeHg were higher in pelagic-feeding than benthic-feeding fauna (determined from delta 13C) indicating the importance of pelagic pathways in transferring MeHg. Lastly, the proportion of total Hg as MeHg increased with trophic level (measured as delta 15N). These results reveal the importance of both biogeochemical and ecological factors in determining the bioavailability and trophic transfer of MeHg in estuarine food webs. PMID:19368175

Chen, Celia Y.; Dionne, Michele; Mayes, Brandon M.; Ward, Darren M.; Sturup, Stefan; Jackson, Brian P.

2009-01-01

363

Lipids of Prokaryotic Origin at the Base of Marine Food Webs  

PubMed Central

In particular niches of the marine environment, such as abyssal trenches, icy waters and hot vents, the base of the food web is composed of bacteria and archaea that have developed strategies to survive and thrive under the most extreme conditions. Some of these organisms are considered “extremophiles” and modulate the fatty acid composition of their phospholipids to maintain the adequate fluidity of the cellular membrane under cold/hot temperatures, elevated pressure, high/low salinity and pH. Bacterial cells are even able to produce polyunsaturated fatty acids, contrarily to what was considered until the 1990s, helping the regulation of the membrane fluidity triggered by temperature and pressure and providing protection from oxidative stress. In marine ecosystems, bacteria may either act as a sink of carbon, contribute to nutrient recycling to photo-autotrophs or bacterial organic matter may be transferred to other trophic links in aquatic food webs. The present work aims to provide a comprehensive review on lipid production in bacteria and archaea and to discuss how their lipids, of both heterotrophic and chemoautotrophic origin, contribute to marine food webs. PMID:23342392

de Carvalho, Carla C. C. R.; Caramujo, Maria José

2012-01-01

364

Nitrogen Addition and Warming Independently Influence the Belowground Micro-Food Web in a Temperate Steppe  

PubMed Central

Climate warming and atmospheric nitrogen (N) deposition are known to influence ecosystem structure and functioning. However, our understanding of the interactive effect of these global changes on ecosystem functioning is relatively limited, especially when it concerns the responses of soils and soil organisms. We conducted a field experiment to study the interactive effects of warming and N addition on soil food web. The experiment was established in 2006 in a temperate steppe in northern China. After three to four years (2009–2010), we found that N addition positively affected microbial biomass and negatively influenced trophic group and ecological indices of soil nematodes. However, the warming effects were less obvious, only fungal PLFA showed a decreasing trend under warming. Interestingly, the influence of N addition did not depend on warming. Structural equation modeling analysis suggested that the direct pathway between N addition and soil food web components were more important than the indirect connections through alterations in soil abiotic characters or plant growth. Nitrogen enrichment also affected the soil nematode community indirectly through changes in soil pH and PLFA. We conclude that experimental warming influenced soil food web components of the temperate steppe less than N addition, and there was little influence of warming on N addition effects under these experimental conditions. PMID:23544140

Li, Qi; Bai, Huahua; Liang, Wenju; Xia, Jianyang; Wan, Shiqiang; van der Putten, Wim H.

2013-01-01

365

Metamorphosis alters contaminants and chemical tracers in insects: implications for food webs.  

PubMed

Insects are integral to most freshwater and terrestrial food webs, but due to their accumulation of environmental pollutants they are also contaminant vectors that threaten reproduction, development, and survival of consumers. Metamorphosis from larvae to adult can cause large chemical changes in insects, altering contaminant concentrations and fractionation of chemical tracers used to establish contaminant biomagnification in food webs, but no framework exists for predicting and managing these effects. We analyzed data from 39 studies of 68 analytes (stable isotopes and contaminants), and found that metamorphosis effects varied greatly. ?(15)N, widely used to estimate relative trophic position in biomagnification studies, was enriched by ? 1‰ during metamorphosis, while ?(13)C used to estimate diet, was similar in larvae and adults. Metals and polycyclic aromatic hydrocarbons (PAHs) were predominantly lost during metamorphosis leading to ? 2 to 125-fold higher larval concentrations and higher exposure risks for predators of larvae compared to predators of adults. In contrast, manufactured organic contaminants (such as polychlorinated biphenyls) were retained and concentrated in adults, causing up to ? 3-fold higher adult concentrations and higher exposure risks to predators of adult insects. Both food web studies and contaminant management and mitigation strategies need to consider how metamorphosis affects the movement of materials between habitats and ecosystems, with special regard for aquatic-terrestrial linkages. PMID:25136925

Kraus, Johanna M; Walters, David M; Wesner, Jeff S; Stricker, Craig A; Schmidt, Travis S; Zuellig, Robert E

2014-09-16

366

Chain or Web?  

NSDL National Science Digital Library

This reference provides a brief description of marine food webs. It presents food web terminology, explains the relationship between food chains and food webs, and introduces the concept of microbial loops.

367

Microalgal productivity, community composition, and pelagic food web dynamics in a subtropical, turbid salt marsh isolated from freshwater inflow  

Microsoft Academic Search

Carbon entering the food web originating from microalgal productivity may be as important to salt marsh consumers as carbon\\u000a originating from vascular plant production. The objective of this study was to further our understanding of the role played\\u000a by microalgae in salt marshes. We focused on microalgal productivity, community dynamics, and pelagic food web linkages. Across\\u000a three consecutive springs (2001–2003),

Elizabeth Fejes; Daniel Roelke; George Gable; James Heilman; Kevin McInnes; David Zuberer

2005-01-01

368

Spatial and temporal operation of the Scotia Sea ecosystem: a review of large-scale links in a krill centred food web.  

PubMed

The Scotia Sea ecosystem is a major component of the circumpolar Southern Ocean system, where productivity and predator demand for prey are high. The eastward-flowing Antarctic Circumpolar Current (ACC) and waters from the Weddell-Scotia Confluence dominate the physics of the Scotia Sea, leading to a strong advective flow, intense eddy activity and mixing. There is also strong seasonality, manifest by the changing irradiance and sea ice cover, which leads to shorter summers in the south. Summer phytoplankton blooms, which at times can cover an area of more than 0.5 million km2, probably result from the mixing of micronutrients into surface waters through the flow of the ACC over the Scotia Arc. This production is consumed by a range of species including Antarctic krill, which are the major prey item of large seabird and marine mammal populations. The flow of the ACC is steered north by the Scotia Arc, pushing polar water to lower latitudes, carrying with it krill during spring and summer, which subsidize food webs around South Georgia and the northern Scotia Arc. There is also marked interannual variability in winter sea ice distribution and sea surface temperatures that is linked to southern hemisphere-scale climate processes such as the El Niño-Southern Oscillation. This variation affects regional primary and secondary production and influences biogeochemical cycles. It also affects krill population dynamics and dispersal, which in turn impacts higher trophic level predator foraging, breeding performance and population dynamics. The ecosystem has also been highly perturbed as a result of harvesting over the last two centuries and significant ecological changes have also occurred in response to rapid regional warming during the second half of the twentieth century. This combination of historical perturbation and rapid regional change highlights that the Scotia Sea ecosystem is likely to show significant change over the next two to three decades, which may result in major ecological shifts. PMID:17405210

Murphy, E J; Watkins, J L; Trathan, P N; Reid, K; Meredith, M P; Thorpe, S E; Johnston, N M; Clarke, A; Tarling, G A; Collins, M A; Forcada, J; Shreeve, R S; Atkinson, A; Korb, R; Whitehouse, M J; Ward, P; Rodhouse, P G; Enderlein, P; Hirst, A G; Martin, A R; Hill, S L; Staniland, I J; Pond, D W; Briggs, D R; Cunningham, N J; Fleming, A H

2007-01-29

369

Spatial and temporal operation of the Scotia Sea ecosystem: a review of large-scale links in a krill centred food web  

PubMed Central

The Scotia Sea ecosystem is a major component of the circumpolar Southern Ocean system, where productivity and predator demand for prey are high. The eastward-flowing Antarctic Circumpolar Current (ACC) and waters from the Weddell–Scotia Confluence dominate the physics of the Scotia Sea, leading to a strong advective flow, intense eddy activity and mixing. There is also strong seasonality, manifest by the changing irradiance and sea ice cover, which leads to shorter summers in the south. Summer phytoplankton blooms, which at times can cover an area of more than 0.5 million km2, probably result from the mixing of micronutrients into surface waters through the flow of the ACC over the Scotia Arc. This production is consumed by a range of species including Antarctic krill, which are the major prey item of large seabird and marine mammal populations. The flow of the ACC is steered north by the Scotia Arc, pushing polar water to lower latitudes, carrying with it krill during spring and summer, which subsidize food webs around South Georgia and the northern Scotia Arc. There is also marked interannual variability in winter sea ice distribution and sea surface temperatures that is linked to southern hemisphere-scale climate processes such as the El Niño–Southern Oscillation. This variation affects regional primary and secondary production and influences biogeochemical cycles. It also affects krill population dynamics and dispersal, which in turn impacts higher trophic level predator foraging, breeding performance and population dynamics. The ecosystem has also been highly perturbed as a result of harvesting over the last two centuries and significant ecological changes have also occurred in response to rapid regional warming during the second half of the twentieth century. This combination of historical perturbation and rapid regional change highlights that the Scotia Sea ecosystem is likely to show significant change over the next two to three decades, which may result in major ecological shifts. PMID:17405210

Murphy, E.J; Watkins, J.L; Trathan, P.N; Reid, K; Meredith, M.P; Thorpe, S.E; Johnston, N.M; Clarke, A; Tarling, G.A; Collins, M.A; Forcada, J; Shreeve, R.S; Atkinson, A; Korb, R; Whitehouse, M.J; Ward, P; Rodhouse, P.G; Enderlein, P; Hirst, A.G; Martin, A.R; Hill, S.L; Staniland, I.J; Pond, D.W; Briggs, D.R; Cunningham, N.J; Fleming, A.H

2006-01-01

370

Antarctic Benthic Fauna in the Global Climate Change  

NASA Astrophysics Data System (ADS)

In the last 50 years a significant climatic shift has been observed along the Antarctic Peninsula (air and seawater temperature rise, glacial retreat, localized instances of lowered shallow waters salinities). Many Antarctic marine benthic invertebrates are adapted to specific environmental conditions (e.g. low stable temperatures, high salinity and oxygen content). Changes caused by global climate changes and subsequent glacial melting can be expected to have significant impacts on species physiology and distribution. The rise of sea water temperature coupled with such additional stress factors as melt water run-off, increased ice disturbance, disruption of food webs or invasion of alien species can be a serious problem for their long-term survival.

Kidawa, Anna; Janecki, Tomasz

2011-01-01

371

The Impact of 850,000 Years of Climate Changes on the Structure and Dynamics of Mammal Food Webs  

PubMed Central

Most evidence of climate change impacts on food webs comes from modern studies and little is known about how ancient food webs have responded to climate changes in the past. Here, we integrate fossil evidence from 71 fossil sites, body-size relationships and actualism to reconstruct food webs for six large mammal communities that inhabited the Iberian Peninsula at different times during the Quaternary. We quantify the long-term dynamics of these food webs and study how their structure changed across the Quaternary, a period for which fossil data and climate changes are well known. Extinction, immigration and turnover rates were correlated with climate changes in the last 850 kyr. Yet, we find differences in the dynamics and structural properties of Pleistocene versus Holocene mammal communities that are not associated with glacial-interglacial cycles. Although all Quaternary mammal food webs were highly nested and robust to secondary extinctions, general food web properties changed in the Holocene. These results highlight the ability of communities to re-organize with the arrival of phylogenetically similar species without major structural changes, and the impact of climate change and super-generalist species (humans) on Iberian Holocene mammal communities. PMID:25207754

Nenzén, Hedvig K.; Montoya, Daniel; Varela, Sara

2014-01-01

372

Trophic transfer of methyl siloxanes in the marine food web from coastal area of northern china.  

PubMed

Methyl siloxanes, which belong to organic silicon compounds and have linear and cyclic structures, are of particular concern because of their potential characteristic of persistent, bioaccumulated, toxic, and ecological harm. This study investigated the trophic transfer of four cyclic methyl siloxanes (octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), and tetradecamethylcycloheptasiloxane (D7)) in a marine food web from coastal area of Northern China. Trophic magnification of D4, D5, D6, and D7 were assessed as the slope of lipid equivalent concentrations regressed against trophic levels of marine food web configurations. A significant positive correlation (R = 0.44, p < 0.0001) was found between lipid normalized D5 concentrations and trophic levels in organisms, showing the trophic magnification potential of this chemical in the marine food web. The trophic magnification factor (TMF) of D5 was estimated to be 1.77 (95% confidence interval (CI): 1.41-2.24, 99.8% probability of the observing TMF > 1). Such a significant link, however, was not found for D4 (R = 0.14 and p = 0.16), D6 (R = 0.01 and p = 0.92), and D7 (R = -0.15 and p = 0.12); and the estimated values of TMFs (95% CI, probability of the observing TMF > 1) were 1.16 (0.94-1.44, 94.7%), 1.01 (0.84-1.22, 66.9%) and 0.85 (0.69-1.04, 48.6%) for D4, D6, and D7, respectively. The TMF value for the legacy contaminant BDE-99 was also estimated as a benchmark, and a significant positive correlation (R = 0.65, p < 0.0001) was found between lipid normalized concentrations and trophic levels in organisms. The TMF value of BDE-99 was 3.27 (95% CI: 2.49-4.30, 99.7% probability of the observing TMF > 1), showing the strong magnification in marine food webs. To the best of our knowledge, this is the first report on the trophic magnification of methyl siloxanes in China, which provided important information for trophic transformation of these compounds in marine food webs. PMID:25625298

Jia, Hongliang; Zhang, Zifeng; Wang, Chaoqun; Hong, Wen-Jun; Sun, Yeqing; Li, Yi-Fan

2015-03-01

373

Linking ecosystems, food webs, and fish production: Subsidies in salmonid watersheds  

USGS Publications Warehouse

Physical characteristics of riverine habitats, such as large wood abundance, pool geometry and abundance, riparian vegetation cover, and surface flow conditions, have traditionally been thought to constrain fish production in these ecosystems. Conversely, the role of food resources (quantity and quality) in controlling fish production has received far less attention and consideration, though they can also be key productivity drivers. Traditional freshwater food web illustrations have typically conveyed the notion that most fish food is produced within the local aquatic habitat itself, but the concepts and model we synthesize in this article show that most fish food comes from external or very distant sources-including subsidies from marine systems borne from adult returns of anadromous fishes, from fishless headwater tributaries that transport prey to downstream fish, and from adjacent streamside vegetation and associated habitats. The model we propose further illustrates how key trophic pathways and food sources vary through time and space throughout watersheds. Insights into how food supplies affect fishes can help guide how we view riverine ecosystems, their structure and function, their interactions with marine and terrestrial systems, and how we manage natural resources, including fish, riparian habitats, and forests.

Wipfli, M.S.; Baxter, C.V.

2010-01-01

374

Evidence supporting the importance of terrestrial carbon in a large-river food web.  

PubMed

Algal carbon has been increasingly recognized as the primary carbon source supporting large-river food webs; however, many of the studies that support this contention have focused on lotic main channels during low-flow periods. The flow variability and habitat-heterogeneity characteristic of these systems has the potential to significantly influence food web structure and must be integrated into models of large-river webs. We used stable-isotope analysis and IsoSource software to model terrestrial and algal sources of organic carbon supporting consumer taxa in the main channel and oxbow lakes of the Brazos River, Texas, USA, during a period of frequent hydrologic connectivity between these habitat types. Standardized sampling was conducted monthly to collect production sources and consumer species used in isotopic analysis. Predictability of hydrologic connections between habitat types was based on the previous 30 years of flow data. IsoSource mixing models identified terrestrial C3 macrophytes (riparian origin) as the primary carbon source supporting virtually all consumers in the main channel and most consumers in oxbow lakes. Small-bodied consumers (<100 mm) in oxbow lakes assimilated large fractions of algal carbon whereas this pattern was not apparent in the main channel. Estimates of detritivore trophic positions based on delta15N values indicated that terrestrial material was likely assimilated via invertebrates rather than directly from detritus. High flows in the river channel influenced algal standing stock, and differences in the importance of terrestrial and algal production sources among consumers in channel vs. oxbow habitats were associated with patterns of flooding. The importance of terrestrial material contradicts the findings of recent studies of large-river food webs that have emphasized the importance of algal carbon and indicates that there can be significant spatial, temporal, and taxonomic variation in carbon sources supporting consumers in large rivers. PMID:18589537

Zeug, Steven C; Winemiller, Kirk O

2008-06-01

375

Factors affecting biotic mercury concentrations and biomagnification through lake food webs in the Canadian high Arctic.  

PubMed

In temperate regions of Canada, mercury (Hg) concentrations in biota and the magnitude of Hg biomagnification through food webs vary between neighboring lakes and are related to water chemistry variables and physical lake features. However, few studies have examined factors affecting the variable Hg concentrations in landlocked Arctic char (Salvelinus alpinus) or the biomagnification of Hg through their food webs. We estimated the food web structure of six high Arctic lakes near Resolute Bay, Nunavut, Canada, using stable carbon (?(13)C) and nitrogen (?(15)N) isotopes and measured Hg (total Hg (THg) in char, the only fish species, and methylmercury (MeHg) in chironomids and zooplankton) concentrations in biota collected in 2010 and 2011. Across lakes, ?(13)C showed that benthic carbon (chironomids) was the dominant food source for char. Regression models of log Hg versus ?(15)N (of char and benthic invertebrates) showed positive and significant slopes, indicting Hg biomagnification in all lakes, and higher slopes in some lakes than others. However, no principal components (PC) generated using all water chemistry data and physical characteristics of the lakes predicted the different slopes. The PC dominated by aqueous ions was a negative predictor of MeHg concentrations in chironomids, suggesting that water chemistry affects Hg bioavailability and MeHg concentrations in these lower-trophic-level organisms. Furthermore, regression intercepts were predicted by the PCs dominated by catchment area, aqueous ions, and MeHg. Weaker relationships were also found between THg in small char or MeHg in pelagic invertebrates and the PCs dominated by catchment area, and aqueous nitrate and MeHg. Results from these high Arctic lakes suggest that Hg biomagnification differs between systems and that their physical and chemical characteristics affect Hg concentrations in lower-trophic-level biota. PMID:24909711

Lescord, Gretchen L; Kidd, Karen A; Kirk, Jane L; O'Driscoll, Nelson J; Wang, Xiaowa; Muir, Derek C G

2015-03-15

376

Nutrient Enrichment and Food Web Composition Affect Ecosystem Metabolism in an Experimental Seagrass Habitat  

PubMed Central

Background Food web composition and resource levels can influence ecosystem properties such as productivity and elemental cycles. In particular, herbivores occupy a central place in food webs as the species richness and composition of this trophic level may simultaneously influence the transmission of resource and predator effects to higher and lower trophic levels, respectively. Yet, these interactions are poorly understood. Methodology/Principal Findings Using an experimental seagrass mesocosm system, we factorially manipulated water column nutrient concentrations, food chain length, and diversity of crustacean grazers to address two questions: (1) Does food web composition modulate the effects of nutrient enrichment on plant and grazer biomasses and stoichiometry? (2) Do ecosystem fluxes of dissolved oxygen and nutrients more closely reflect above-ground biomass and community structure or sediment processes? Nutrient enrichment and grazer presence generally had strong effects on biomass accumulation, stoichiometry, and ecosystem fluxes, whereas predator effects were weaker or absent. Nutrient enrichment had little effect on producer biomass or net ecosystem production but strongly increased seagrass nutrient content, ecosystem flux rates, and grazer secondary production, suggesting that enhanced production was efficiently transferred from producers to herbivores. Gross ecosystem production (oxygen evolution) correlated positively with above-ground plant biomass, whereas inorganic nutrient fluxes were unrelated to plant or grazer biomasses, suggesting dominance by sediment microbial processes. Finally, grazer richness significantly stabilized ecosystem processes, as predators decreased ecosystem production and respiration only in the zero- and one- species grazer treatments. Conclusions/Significance Overall, our results indicate that consumer presence and species composition strongly influence ecosystem responses to nutrient enrichment, and that increasing herbivore diversity can stabilize ecosystem flux rates in the face of perturbations. PMID:19829713

Spivak, Amanda C.; Canuel, Elizabeth A.; Duffy, J. Emmett; Richardson, J. Paul

2009-01-01

377

Bioaccumulation patterns of methyl mercury and essential fatty acids in lacustrine planktonic food webs and fishB  

E-print Network

Bioaccumulation patterns of methyl mercury and essential fatty acids in lacustrine planktonic food September 2005 Available online 14 October 2005 Abstract Organisms of the planktonic food web convey essential nutrients as well as contaminants to animals at higher trophic levels. We measured concentrations

Mazumder, Asit

378

Isotopic evidence for anthropogenic impacts on aquatic food web dynamics and mercury cycling in a subtropical wetland ecosystem in  

E-print Network

Direct Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv #12;clear evidenceIsotopic evidence for anthropogenic impacts on aquatic food web dynamics and mercury cycling impacts of land-use change on food chains and Hg bioaccu- mulation. · In reference wetlands, fishes relied

Wang, Yang

379

Antarctic Meteorology Online from the British Antarctic Survey  

NSDL National Science Digital Library

The Antarctic Meteorology Online Web site is provided by the British Antarctic Survey and the Natural Environment Research Council. Visitors will find weather reports provided by the dozens of stations located in the Antarctic. The Web master has made these data accessible by each specific station; by a clickable map; by a list of all land, ship, or buoy stations; or by an oracle database interface. The reports are at least 10 minutes old and are normally not more than six hours old. The information provided includes a graph of pressure and temperature, as well as links to previous reports, which make the site a good and easily accessible resource. This site is also reviewed in the November 27, 2002 Scout Report.

380

THE CONTRIBUTION OF MICROARTHROPODS TO ABOVE GROUND FOOD WEBS: A REVIEW AND MODEL OF BELOW GROUND TRANSFER IN A CONIFEROUS FOREST  

EPA Science Inventory

Although belowground food webs have received much attention, studies concerning microarthropods in nondetrital food webs are scarce. Because adult oribatid mites often number between 250,000-500,000/m(2) in coniferous forests, microarthropods are a potential food resource for mic...

381

Bioaccumulation and trophic transfer of perfluorinated compounds in a eutrophic freshwater food web.  

PubMed

In this study, the bioaccumulation of perfluorinated compounds from a food web in Taihu Lake in China was investigated. The organisms included egret bird species, carnivorous fish, omnivorous fish, herbivorous fish, zooplankton, phytoplankton, zoobenthos and white shrimp. Isotope analysis by ?(13)C and ?(15)N indicated that the carnivorous fish and egret were the top predators in the studied web, occupying trophic levels intermediate between 3.66 and 4.61, while plankton was at the lowest trophic level. Perfluorinated carboxylates (PFCAs) with 9-12 carbons were significantly biomagnified, with trophic magnification factors (TMFs) ranging from 2.1 to 3.7. The TMF of perfluorooctane sulfonate (PFOS) (2.9) was generally comparable to or lower than those of the PFCAs in the same food web. All hazard ratio (HR) values reported for PFOS and perfluorooctanoate (PFOA) were less than unity, suggesting that the detected levels would not cause any immediate health effects to the people in Taihu Lake region through the consumption of shrimps and fish. PMID:24077253

Xu, Jian; Guo, Chang-Sheng; Zhang, Yuan; Meng, Wei

2014-01-01

382

Common Patterns of Energy Flow and Biomass Distribution on Weighted Food Webs  

E-print Network

Weights of edges and nodes on food webs which are available from the empirical data hide much information about energy flows and biomass distributions in ecosystem. We define a set of variables related to weights for each species $i$, including the throughflow $T_i$, the total biomass $X_i$, and the dissipated flow $D_i$ (output to the environment) to uncover the following common patterns in 19 empirical weighted food webs: (1) DGBD distributions (Discrete version of a Generalized Beta Distribution), a kind of deformed Zipf's law, of energy flow and storage biomass; (2) The allometric scaling law $T_i\\propto X_i^{\\alpha}$, which can be viewed as the counterpart of the Kleiber's 3/4 law at the population level; (3) The dissipation law $D_i\\propto T_i^{\\beta}$; and (4) The gravity law, including univariate version $f_{ij}\\propto (T_iT_j)^{\\gamma}$ and bivariate approvement $f_{ij}\\propto T_i^{\\gamma_1}T_j^{\\gamma_2}$. These patterns are very common and significant in all collected webs, as a result, some remark...

Zhang, Jiang

2012-01-01

383

River and Wetland Food Webs in Australia's Wet-Dry Tropics: General Principles and Implications for Management.  

NASA Astrophysics Data System (ADS)

The tropical rivers of northern Australia are internationally recognised for their high ecological and cultural values. They have largely unmodified flow regimes and are comparatively free of the impacts associated with intensive land use. However, there is growing demand for agricultural development and existing pressures, such as weeds and feral animals, threaten their ecological integrity. Using the international literature to provide a conceptual framework and drawing on limited published and unpublished data on rivers in northern Australia, we have derived five general principles about food webs and related ecosystem processes that both characterise tropical rivers of northern Australia and have important implications for their management. These are: (1) Seasonal hydrology is a strong driver of ecosystem processes and food web structure; (2) Hydrological connectivity is largely intact and underpins important terrestrial-aquatic food web subsidies; (3) River and wetland food webs are strongly dependent on algal production; (4) A few common macroconsumers species have a strong influence on benthic food webs; (5) Omnivory is widespread and food chains are short. These principles have implications for the management and protection of tropical rivers and wetlands of northern Australia and provide a framework for the formation of testable hypotheses in future research programs.

Douglas, M. M.; Bunn, S. E.; Davies, P. M.

2005-05-01

384

An innovative statistical approach to constructing a readily comprehensible food web for a demersal fish community  

NASA Astrophysics Data System (ADS)

Many food webs are so complex that it is difficult to distinguish the relationships between predators and their prey. We have therefore developed an approach that produces a food web which clearly demonstrates the strengths of the relationships between the predator guilds of demersal fish and their prey guilds in a coastal ecosystem. Subjecting volumetric dietary data for 35 abundant predators along the lower western Australia coast to cluster analysis and the SIMPROF routine separated the various species × length class combinations into 14 discrete predator guilds. Following nMDS ordination, the sequence of points for these predator guilds represented a 'trophic' hierarchy. This demonstrated that, with increasing body size, several species progressed upwards through this hierarchy, reflecting a marked change in diet, whereas others remained within the same guild. A novel use of cluster analysis and SIMPROF then identified each group of prey that was ingested in a common pattern across the full suite of predator guilds. This produced 12 discrete groups of taxa (prey guilds) that each typically comprised similar ecological/functional prey, which were then also aligned in a hierarchy. The hierarchical arrangements of the predator and prey guilds were plotted against each other to show the percentage contribution of each prey guild to the diet of each predator guild. The resultant shade plot demonstrates quantitatively how food resources are spread among the fish species and revealed that two prey guilds, one containing cephalopods and teleosts and the other small benthic/epibenthic crustaceans and polychaetes, were consumed by all predator guilds.

French, Ben; Clarke, K. Robert; Platell, Margaret E.; Potter, Ian C.

2013-07-01

385

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

USGS Publications Warehouse

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.

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

2002-01-01

386

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

USGS Publications Warehouse

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.

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

2002-01-01

387

Effects of zebra mussels on food webs: Interactions with juvenile bluegill and water residence time  

USGS Publications Warehouse

We evaluated how water residence time mediated the impact of zebra mussels Dreissena polymorpha and bluegill sunfish Lepomis macrochirus on experimental food webs established in 1100-1 outdoor mesocosms. Water residence time was manipulated as a surrogate for seston resupply - a critical variable affecting growth and survival of suspension-feeding invertebrates. We used a 2 x 2 x 2 factorial experimental design with eight treatment combinations (3 replicates/treatment) including the presence or absence of Dreissena (2000 per m2), juvenile bluegill (40 per mesocosm), and short (1100 1 per d) or long (220 1 per d) water residence time. Measures of seston concentration (chlorophyll a, turbidity and suspended solids) were greater in the short- compared to long water-residence mesocosms, but intermediate in short water-residence mesocosms containing Dreissena. Abundance of rotifers (Keratella and Polyarthra) was reduced in Dreissena mesocosms and elevated in short residence time mesocosms. Cladocera abundance, in general, was unaffected by the presence of Dreissena; densities were higher in short-residence time mesocosms, and reduced in the presence of Lepomis. The growth of juvenile Lepomis were unaffected by Dreissena because of abundant benthic food. The final total mass of Dreissena was significantly greater in short- than long-residence mesocosms. Impacts of Dreissena on planktonic food webs may not only depend on the density of zebra mussels but also on the residence time of the surrounding water and the resupply of seston. ?? 1997 Kluwer Academic Publishers.

Richardson, W.B.; Bartsch, L.A.

1997-01-01

388

Age and trophic position dominate bioaccumulation of mercury and organochlorines in the food web of Lake Washington  

USGS Publications Warehouse

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.

McIntyre, J.K.; Beauchamp, D.A.

2007-01-01

389

Antarctic Fishes.  

ERIC Educational Resources Information Center

Explains the adaptations to Antarctic waters that Notothenioidei, a group of advanced bony fishes, have exhibited. Discusses the fishes' mechanisms of production of antifreeze properties and their capacities for neutral buoyancy in water. (ML)

Eastman, Joseph T.; DeVries, Arthur L.

1986-01-01

390

Antarctic Ecosystem  

NSDL National Science Digital Library

In contrast with its largely lifeless interior, the Antarctic coastal marine environment supports a vibrant and diverse ecosystem. Explore the region's living bounty in this interactive activity adapted from the Woods Hole Oceanographic Institution.

WGBH Educational Foundation

2008-01-17

391

Antarctic Krill 454 Pyrosequencing Reveals Chaperone and Stress Transcriptome  

PubMed Central

Background The Antarctic krill Euphausia superba is a keystone species in the Antarctic food chain. Not only is it a significant grazer of phytoplankton, but it is also a major food item for charismatic megafauna such as whales and seals and an important Southern Ocean fisheries crop. Ecological data suggest that this species is being affected by climate change and this will have considerable consequences for the balance of the Southern Ocean ecosystem. Hence, understanding how this organism functions is a priority area and will provide fundamental data for life history studies, energy budget calculations and food web models. Methodology/Principal Findings The assembly of the 454 transcriptome of E. superba resulted in 22,177 contigs with an average size of 492bp (ranging between 137 and 8515bp). In depth analysis of the data revealed an extensive catalogue of the cellular chaperone systems and the major antioxidant proteins. Full length sequences were characterised for the chaperones HSP70, HSP90 and the super-oxide dismutase antioxidants, with the discovery of potentially novel duplications of these genes. The sequence data contained 41,470 microsatellites and 17,776 Single Nucleotide Polymorphisms (SNPs/INDELS), providing a resource for population and also gene function studies. Conclusions This paper details the first 454 generated data for a pelagic Antarctic species or any pelagic crustacean globally. The classical “stress proteins”, such as HSP70, HSP90, ferritin and GST were all highly expressed. These genes were shown to be over expressed in the transcriptomes of Antarctic notothenioid fish and hypothesized as adaptations to living in the cold, with the associated problems of decreased protein folding efficiency and increased vulnerability to damage by reactive oxygen species. Hence, these data will provide a major resource for future physiological work on krill, but in particular a suite of “stress” genes for studies understanding marine ectotherms' capacities to cope with environmental change. PMID:21253607

Clark, Melody S.; Thorne, Michael A. S.; Toullec, Jean-Yves; Meng, Yan; Guan, Le Luo; Peck, Lloyd S.; Moore, Stephen

2011-01-01

392

Are Algae Relevant to the Detritus-Based Food Web in Tank-Bromeliads?  

PubMed Central

We assessed the occurrence of algae in five species of tank-bromeliads found in contrasting environmental sites in a Neotropical, primary rainforest around the Nouragues Research Station, French Guiana. The distributions of both algal abundance and biomass were examined based on physical parameters, the morphological characteristics of bromeliad species and with regard to the structure of other aquatic microbial communities held in the tanks. Algae were retrieved in all of the bromeliad species with mean densities ranging from ?102 to 104 cells/mL. Their biomass was positively correlated to light exposure and bacterial biomass. Algae represented a tiny component of the detrital food web in shaded bromeliads but accounted for up to 30 percent of the living microbial carbon in the tanks of Catopsis berteroniana, located in a highly exposed area. Thus, while nutrient supplies are believed to originate from wind-borne particles and trapped insects (i.e., allochtonous organic matter), our results indicate that primary producers (i.e., autochtonous organic matter) are present in this insectivorous bromeliad. Using a 24-h incubation of size-fractionated and manipulated samples from this plant, we evaluated the impact of mosquito foraging on algae, other microorganisms and rotifers. The prey assemblages were greatly altered by the predation of mosquito larvae. Grazing losses indicated that the dominant algal taxon, Bumilleriopsis sp., like protozoa and rotifers, is a significant part of the diet of mosquito larvae. We conclude that algae are a relevant functional community of the aquatic food web in C. berteroniana and might form the basis of a complementary non-detrital food web. PMID:21625603

Brouard, Olivier; Le Jeune, Anne-Hélène; Leroy, Céline; Cereghino, Régis; Roux, Olivier; Pelozuelo, Laurent; Dejean, Alain; Corbara, Bruno; Carrias, Jean-François

2011-01-01

393

Bioaccumulation syndrome: identifying factors that make some stream food webs prone to elevated mercury bioaccumulation  

PubMed Central

Mercury is a ubiquitous contaminant in aquatic ecosystems, posing a significant health risk to humans and wildlife that eat fish. Mercury accumulates in aquatic food webs as methylmercury (MeHg), a particularly toxic and persistent organic mercury compound. While mercury in the environment originates largely from anthropogenic activities, MeHg accumulation in freshwater aquatic food webs is not a simple function of local or regional mercury pollution inputs. Studies show that even sites with similar mercury inputs can produce fish with mercury concentrations ranging over an order of magnitude. While much of the foundational work to identify the drivers of variation in mercury accumulation has focused on freshwater lakes, mercury contamination in stream ecosystems is emerging as an important research area. Here, we review recent research on mercury accumulation in stream-dwelling organisms. Taking a hierarchical approach, we identify a suite of characteristics of individual consumers, food webs, streams, watersheds, and regions that are consistently associated with elevated MeHg concentrations in stream fish. We delineate a conceptual, mechanistic basis for explaining the ecological processes that underlie this vulnerability to MeHg. Key factors, including suppressed individual growth of consumers, low rates of primary and secondary production, hydrologic connection to methylation sites (e.g. wetlands), heavily forested catchments, and acidification are frequently associated with increased MeHg concentrations in fish across both streams and lakes. Hence, we propose that these interacting factors define a syndrome of characteristics that drive high MeHg production and bioaccumulation rates across these freshwater aquatic ecosystems. Finally, based on an understanding of the ecological drivers of MeHg accumulation, we identify situations when anthropogenic effects and management practices could significantly exacerbate or ameliorate MeHg accumulation in stream fish. PMID:20536817

Ward, Darren M.; Nislow, Keith H.; Folt, Carol L.

2010-01-01

394

Modeling selenium bioaccumulation through arthropod food webs in San Francisco Bay, California, USA  

USGS Publications Warehouse

Trophic transfer is the main process by which upper trophic level wildlife are exposed to selenium. Transfers through lower levels of a predator's food web thus can be instrumental in determining the threat of selenium in an ecosystem. Little is known about Se transfer through pelagic, zooplankton-based food webs in San Francisco Bay ([SFB], CA, USA), which serve as an energy source for important predators such as striped bass. A dynamic multipathway bioaccumulation model was used to model Se transfer from phytoplankton to pelagic copepods to carnivorous mysids (Neomysis mercedis). Uptake rates of dissolved Se, depuration rates, and assimilation efficiencies (AE) for the model were determined for copepods and mysids in the laboratory. Small (73-250 ??m) and large (250-500 ??m) herbivorous zooplankton collected from SFB (Oithona/Limnoithona and Acartia sp.) assimilated Se with similar efficiencies (41-52%) from phytoplankton. Mysids assimilated 73% of Se from small herbivorous zooplankton; Se AE was significantly lower (61%) than larger herbivorous zooplankton. Selenium depuration rates were high for both zooplankton and mysids (12-25% d-1), especially compared to bivalves (2-3% d-1). The model predicted steady state Se concentrations in mysids similar to those observed in the field. The predicted concentration range (1.5-5.4 ??g g -1) was lower than concentrations of 4.5 to 24 ??g g-1 observed in bivalves from the bay. Differences in efflux between mysids and bivalves were the best explanation for the differences in uptake. The results suggest that the risk of selenium toxicity to predators feeding on N. mercedis would be less than the risk to predators feeding on bivalves. Management of selenium contamination should include food webs analyses to focus on the most important exposure pathways identified for a given watershed.

Schlekat, C.E.; Purkerson, D.G.; Luoma, S.N.

2004-01-01

395

Terrestrial Contributions to the Aquatic Food Web in the Middle Yangtze River  

PubMed Central

Understanding the carbon sources supporting aquatic consumers in large rivers is essential for the protection of ecological integrity and for wildlife management. The relative importance of terrestrial and algal carbon to the aquatic food webs is still under intensive debate. The Yangtze River is the largest river in China and the third longest river in the world. The completion of the Three Gorges Dam (TGD) in 2003 has significantly altered the hydrological regime of the middle Yangtze River, but its immediate impact on carbon sources supporting the river food web is unknown. In this study, potential production sources from riparian and the main river channel, and selected aquatic consumers (invertebrates and fish) at an upstream constricted-channel site (Luoqi), a midstream estuarine site (Huanghua) and a near dam limnetic site (Maoping) of the TGD were collected for stable isotope (?13C and ?15N) and IsoSource analyses. Model estimates indicated that terrestrial plants were the dominant carbon sources supporting the consumer taxa at the three study sites. Algal production appeared to play a supplemental role in supporting consumer production. The contribution from C4 plants was more important than that of C3 plants at the upstream site while C3 plants were the more important carbon source to the consumers at the two impacted sites (Huanghua and Maoping), particularly at the midstream site. There was no trend of increase in the contribution of autochthonous production from the upstream to the downstream sites as the flow rate decreased dramatically along the main river channel due to the construction of TGD. Our findings, along with recent studies in rivers and lakes, are contradictory to studies that demonstrate the importance of algal carbon in the aquatic food web. Differences in system geomorphology, hydrology, habitat heterogeneity, and land use may account for these contradictory findings reported in various studies. PMID:25047656

Wang, Jianzhu; Gu, Binhe; Huang, Jianhui; Han, Xingguo; Lin, Guanghui; Zheng, Fawen; Li, Yuncong

2014-01-01

396

Microbial food web dynamics along a soil chronosequence of a glacier forefield  

NASA Astrophysics Data System (ADS)

Microbial food webs are critical for efficient nutrient turnover providing the basis for functional and stable ecosystems. However, the successional development of such microbial food webs and their role in "young" ecosystems is unclear. Due to a continuous glacier retreat since the middle of the 19th century, glacier forefields have expanded offering an excellent opportunity to study food web development at differently developed soils. In the present study, litter degradation and the corresponding C fluxes into microbial communities were investigated along the forefield of the Damma glacier (Switzerland). 13C-enriched litter of the pioneering plant Leucanthemopsis alpina (L.) Heywood was incorporated into the soil at sites that have been free from ice for approximately 10, 60, 100 and more than 700 years. The structure and function of microbial communities were identified by 13C analysis of phospholipid fatty acids (PLFA) and phospholipid ether lipids (PLEL). Results showed increasing microbial diversity and biomass, and enhanced proliferation of bacterial groups as ecosystem development progressed. Initially, litter decomposition proceeded faster at the more developed sites, but at the end of the experiment loss of litter mass was similar at all sites, once the more easily-degradable litter fraction was processed. As a result incorporation of 13C into microbial biomass was more evident during the first weeks of litter decomposition. 13C enrichments of both PLEL and PUFA biomarkers following litter incorporation were observed at all sites, suggesting similar microbial foodwebs at all stages of soil development. Nonetheless, the contribution of bacteria and actinomycetes to litter turnover became more pronounced as soil age increased in detriment of archaea, fungi and protozoa, more prominent in recently deglaciated terrain.

Esperschütz, J.; Pérez-de-Mora, A.; Schreiner, K.; Welzl, G.; Buegger, F.; Zeyer, J.; Hagedorn, F.; Munch, J. C.; Schloter, M.

2011-02-01

397

Microbial food web dynamics along a soil chronosequence of a glacier forefield  

NASA Astrophysics Data System (ADS)

Microbial food webs are critical for efficient nutrient turnover providing the basis for functional and stable ecosystems. However, the successional development of such microbial food webs and their role in "young" ecosystems is unclear. Due to a continuous glacier retreat since the middle of the 19th century, glacier forefields have expanded offering an excellent opportunity to study food web dynamics in soils at different developmental stages. In the present study, litter degradation and the corresponding C fluxes into microbial communities were investigated along the forefield of the Damma glacier (Switzerland). 13C-enriched litter of the pioneering plant Leucanthemopsis alpina (L.) Heywood was incorporated into the soil at sites that have been free from ice for approximately 10, 60, 100 and more than 700 years. The structure and function of microbial communities were identified by 13C analysis of phospholipid fatty acids (PLFA) and phospholipid ether lipids (PLEL). Results showed increasing microbial diversity and biomass, and enhanced proliferation of bacterial groups as ecosystem development progressed. Initially, litter decomposition proceeded faster at the more developed sites, but at the end of the experiment loss of litter mass was similar at all sites, once the more easily-degradable litter fraction was processed. As a result incorporation of 13C into microbial biomass was more evident during the first weeks of litter decomposition. 13C enrichments of both PLEL and PLFA biomarkers following litter incorporation were observed at all sites, suggesting similar microbial foodwebs at all stages of soil development. Nonetheless, the contribution of bacteria, especially actinomycetes to litter turnover became more pronounced as soil age increased in detriment of archaea, fungi and protozoa, more prominent in recently deglaciated terrain.

Esperschütz, J.; Pérez-de-Mora, A.; Schreiner, K.; Welzl, G.; Buegger, F.; Zeyer, J.; Hagedorn, F.; Munch, J. C.; Schloter, M.

2011-11-01

398

Terrestrial contributions to the aquatic food web in the middle Yangtze River.  

PubMed

Understanding the carbon sources supporting aquatic consumers in large rivers is essential for the protection of ecological integrity and for wildlife management. The relative importance of terrestrial and algal carbon to the aquatic food webs is still under intensive debate. The Yangtze River is the largest river in China and the third longest river in the world. The completion of the Three Gorges Dam (TGD) in 2003 has significantly altered the hydrological regime of the middle Yangtze River, but its immediate impact on carbon sources supporting the river food web is unknown. In this study, potential production sources from riparian and the main river channel, and selected aquatic consumers (invertebrates and fish) at an upstream constricted-channel site (Luoqi), a midstream estuarine site (Huanghua) and a near dam limnetic site (Maoping) of the TGD were collected for stable isotope (?13C and ?15N) and IsoSource analyses. Model estimates indicated that terrestrial plants were the dominant carbon sources supporting the consumer taxa at the three study sites. Algal production appeared to play a supplemental role in supporting consumer production. The contribution from C4 plants was more important than that of C3 plants at the upstream site while C3 plants were the more important carbon source to the consumers at the two impacted sites (Huanghua and Maoping), particularly at the midstream site. There was no trend of increase in the contribution of autochthonous production from the upstream to the downstream sites as the flow rate decreased dramatically along the main river channel due to the construction of TGD. Our findings, along with recent studies in rivers and lakes, are contradictory to studies that demonstrate the importance of algal carbon in the aquatic food web. Differences in system geomorphology, hydrology, habitat heterogeneity, and land use may account for these contradictory findings reported in various studies. PMID:25047656

Wang, Jianzhu; Gu, Binhe; Huang, Jianhui; Han, Xingguo; Lin, Guanghui; Zheng, Fawen; Li, Yuncong

2014-01-01

399

Oil carbon entered the coastal planktonic food web during the Deepwater Horizon oil spill  

NASA Astrophysics Data System (ADS)

The Deepwater Horizon oil spill was unprecedented in total loading of petroleum hydrocarbons accidentally released to a marine ecosystem. Controversial application of chemical dispersants presumably accelerated microbial consumption of oil components, especially in warm Gulf of Mexico surface waters. We employed ?13C as a tracer of oil-derived carbon to resolve two periods of isotopic carbon depletion in two plankton size classes. Carbon depletion was coincident with the arrival of surface oil slicks in the far northern Gulf, and demonstrated that subsurface oil carbon was incorporated into the plankton food web.

Graham, William M.; Condon, Robert H.; Carmichael, Ruth H.; D'Ambra, Isabella; Patterson, Heather K.; Linn, Laura J.; Hernandez, Frank J., Jr.

2010-10-01

400

Disruption of the lower food web in Lake Ontario: Did it affect alewife growth or condition?  

USGS Publications Warehouse

From the early 1980s to the late 1990s, a succession of non-native invertebrates colonized Lake Ontario and the suite of consequences caused by their colonization became known as "food web disruption". For example, the native burrowing amphipod Diporeia spp., a key link in the profundal food web, declined to near absence, exotic predaceous cladocerans with long spines proliferated, altering the zooplankton community, and depth distributions of fishes shifted. These changes had the potential to affect growth and condition of planktivorous alewife Alosa pseudoharengus, the most abundant fish in the lake. To determine if food web disruption affected alewife, we used change-point analysis to examine alewife growth and adult alewife condition during 1976-2006 and analysis-of-variance to determine if values between change points differed significantly. There were no change points in growth during the first year of life. Of three change points in growth during the second year of life, one coincided with the shift in springtime distribution of alewife to deeper water but it was not associated with a significant change in growth. After the second year of life, no change points in growth were evident, although growth in the third year of life spiked in those years when Bythotrephes, the largest of the exotic cladocerans, was abundant suggesting that it was a profitable prey item for age-2 fish. We detected two change points in condition of adult alewife in fall, but the first occurred in 1981, well before disruption began. A second change point occurred in 2003, well after disruption began. After the springtime distribution of alewife shifted deeper during 1992-1994, growth in the first two years of life became more variable, and growth in years of life two and older became correlated (P < 0.05). In conclusion, food web disruption had no negative affect on growth and condition of alewife in Lake Ontario although it appears to have resulted in growth in the first two years of life becoming more variable, growth in years of life two and older becoming correlated (P < 0.05), and growth spurts in year of life three. Copyright ?? 2008 AEHMS.

O'Gorman, R.; Prindle, S.E.; Lantry, J.R.; Lantry, B.F.

2008-01-01

401

Disentangling trophic relationships in a High Arctic tundra ecosystem through food web modeling.  

PubMed

Determining the manner in which food webs will respond to environmental changes is difficult because the relative importance of top-down vs. bottom-up forces in controlling ecosystems is still debated. This is especially true in the Arctic tundra where, despite relatively simple food webs, it is still unclear which forces dominate in this ecosystem. Our primary goal was to assess the extent to which a tundra food web was dominated by plant-herbivore or predator-prey interactions. Based on a 17-year (1993-2009) study of terrestrial wildlife on Bylot Island, Nunavut, Canada, we developed trophic mass balance models to address this question. Snow Geese were the dominant herbivores in this ecosystem, followed by two sympatric lemming species (brown and collared lemmings). Arctic foxes, weasels, and several species of birds of prey were the dominant predators. Results of our trophic models encompassing 19 functional groups showed that <10% of the annual primary production was consumed by herbivores in most years despite the presence of a large Snow Goose colony, but that 20-100% of the annual herbivore production was consumed by predators. The impact of herbivores on vegetation has also weakened over time, probably due to an increase in primary production. The impact of predators was highest on lemmings, intermediate on passerines, and lowest on geese and shorebirds, but it varied with lemming abundance. Predation of collared lemmings exceeded production in most years and may explain why this species remained at low density. In contrast, the predation rate on brown lemmings varied with prey density and may have contributed to the high-amplitude, periodic fluctuations in the abundance of this species. Our analysis provided little evidence that herbivores are limited by primary production on Bylot Island. In contrast, we measured strong predator-prey interactions, which supports the hypothesis that this food web is primarily controlled by top-down forces. The presence of allochthonous resources subsidizing top predators and the absence of large herbivores may partly explain the predominant role of predation in this low-productivity ecosystem. PMID:22919916

Legagneux, P; Gauthier, G; Berteaux, D; Bêty, J; Cadieux, M C; Bilodeau, F; Bolduc, E; McKinnon, L; Tarroux, A; Therrien, J F; Morissette, L; Krebs, C J

2012-07-01

402

Trophodynamics of some PFCs and BFRs in a western Canadian Arctic marine food web.  

PubMed

The trophodynamics of per- and polyfluorinated compounds and bromine-based flame retardants were examined in components of a marine food web from the western Canadian Arctic. The animals studied and their relative trophic status in the food web, established using stable isotopes of nitrogen (delta15N), were beluga (Delphinapterus leucas) > ringed seal (Phoca hispida) > Arctic cod (Boreogadus saida) > Pacific herring (Clupea pallasi) approximately equal to Arctic cisco (Coregonus autumnalis) > pelagic amphipod (Themisto libellula) > Arctic copepod (Calanus hyperboreus). For the brominated diphenyl ethers, the lipid adjusted concentrations of the seven congeners analyzed (Sigma7BDEs: -47, -85, -99, -100, -153, -154, and -209) ranged from 205.4 +/- 52.7 ng/g in Arctic cod to 2.6 +/- 0.4 ng/g in ringed seals. Mean Sigma7BDEs concentrations in Arctic copepods, 16.4 ng/g (n = 2, composite sample), were greater than those in the top trophic level (TL) marine mammals and suggests that (i) Arctic copepods are an important dietary component that delivers BDEs to the food web and (ii) because these compounds are bioaccumulative, metabolism and depletion of BDE congeners in top TL mammals is an important biological process. There were differences in the concentration profiles of the isomers of hexabromocyclododecane (HBCD) in the food web. The most notable difference was observed for beluga, where the alpha-isomer was enriched (accounting for approximately 90% of the SigmaHBCD body burden), relative to its primary prey species, Arctic cod, where the alpha-isomer accounted for only 20% of the SigmaHBCD body burden (beta: 4% and gamma: 78%). For the C8-C11 perfluorinated carboxylic acids, the trophic magnification factors (TMFs) were all greater than unity and increased with increasing carbon chain length. PFOS and its neutral precursor, PFOSA, also had TMF values greater than one. There were also pronounced differences in the PFOSA to PFOS ratio in ringed seal (0.04) and in beluga (1.4) and suggests that, in part, there are differences in the efficacy of biotransforming PFOSA by whale and seal top predators that both preferentially feed on Arctic cod. PMID:19569333

Tomy, Gregg T; Pleskach, Kerri; Ferguson, Steve H; Hare, Jonathon; Stern, Gary; Macinnis, Gordia; Marvin, Chris H; Loseto, Lisa

2009-06-01

403

Divergent composition but similar function of soil food webs of individual plants: plant species and community effects.  

PubMed

Soils are extremely rich in biodiversity, and soil organisms play pivotal roles in supporting terrestrial life, but the role that individual plants and plant communities play in influencing the diversity and functioning of soil food webs remains highly debated. Plants, as primary producers and providers of resources to the soil food web, are of vital importance for the composition, structure, and functioning of soil communities. However, whether natural soil food webs that are completely open to immigration and emigration differ underneath individual plants remains unknown. In a biodiversity restoration experiment we first compared the soil nematode communities of 228 individual plants belonging to eight herbaceous species. We included grass, leguminous, and non-leguminous species. Each individual plant grew intermingled with other species, but all plant species had a different nematode community. Moreover, nematode communities were more similar when plant individuals were growing in the same as compared to different plant communities, and these effects were most apparent for the groups of bacterivorous, carnivorous, and omnivorous nematodes. Subsequently, we analyzed the composition, structure, and functioning of the complete soil food webs of 58 individual plants, belonging to two of the plant species, Lotus corniculatus (Fabaceae) and Plantago lanceolata (Plantaginaceae). We isolated and identified more than 150 taxa/groups of soil organisms. The soil community composition and structure of the entire food webs were influenced both by the species identity of the plant individual and the surrounding plant community. Unexpectedly, plant identity had the strongest effects on decomposing soil organisms, widely believed to be generalist feeders. In contrast, quantitative food web modeling showed that the composition of the plant community influenced nitrogen mineralization under individual plants, but that plant species identity did not affect nitrogen or carbon mineralization or food web stability. Hence, the composition and structure of entire soil food webs vary at the scale of individual plants and are strongly influenced by the species identity of the plant. However, the ecosystem functions these food webs provide are determined by the identity of the entire plant community. PMID:21058562

Bezemer, T M; Fountain, M T; Barea, J M; Christensen, S; Dekker, S C; Duyts, H; van Hal, R; Harvey, J A; Hedlund, K; Maraun, M; Mikola, J; Mladenov, A G; Robin, C; de Ruiter, P C; Scheu, S; Setälä, H; Smilauer, P; van der Putten, W H

2010-10-01

404

Short-term effects of different genetically modified maize varieties on arthropod food web properties: an experimental field assessment  

PubMed Central

There is concern that genetically modified (GM) plants may have adverse affects on the arthropod biodiversity comprising agricultural landscapes. The present study report on a two year field experimental test of whether four different genotypic lines, some are novel with no previous field tests, of GM maize hybrids alter the structure of arthropod food webs that they harbour, relative to non-GM maize (control) that is widely used in agriculture. The different GM genotypes produced either Bt toxins, conferred glyphosate tolerance or a combination of the two traits. Quantitative food web analysis, based on short-term assessment assigning a total of 243,896 arthropod individuals collected from the treatments to their positions in food webs, revealed that complex and stable food webs persisted in each maize treatment. Moreover, food web structure remained relatively unchanged by the GM-genotype. The results suggest that at least in short-term period these particular GM maize genotypes will not have adverse effects on arthropod biota of agricultural landscapes. PMID:24937207

Szénási, Ágnes; Pálinkás, Zoltán; Zalai, Mihály; Schmitz, Oswald J.; Balog, Adalbert

2014-01-01

405

Prey Vulnerability Limits Top-Down Control and Alters Reciprocal Feedbacks in a Subsidized Model Food Web  

PubMed Central

Resource subsidies increase the productivity of recipient food webs and can affect ecosystem dynamics. Subsidies of prey often support elevated predator biomass which may intensify top-down control and reduce the flow of reciprocal subsidies into adjacent ecosystems. However, top-down control in subsidized food webs may be limited if primary consumers posses morphological or behavioral traits that limit vulnerability to predation. In forested streams, terrestrial prey support high predator biomass creating the potential for strong top-down control, however armored primary consumers often dominate the invertebrate assemblage. Using empirically based simulation models, we tested the response of stream food webs to variations in subsidy magnitude, prey vulnerability, and the presence of two top predators. While terrestrial prey inputs increased predator biomass (+12%), the presence of armored primary consumers inhibited top-down control, and diverted most aquatic energy (?75%) into the riparian forest through aquatic insect emergence. Food webs without armored invertebrates experienced strong trophic cascades, resulting in higher algal (?50%) and detrital (?1600%) biomass, and reduced insect emergence (?90%). These results suggest prey vulnerability can mediate food web responses to subsidies, and that top-down control can be arrested even when predator-invulnerable consumers are uncommon (20%) regardless of the level of subsidy. PMID:24465732

Atlas, William I.; Palen, Wendy J.

2014-01-01

406

Short-term effects of different genetically modified maize varieties on arthropod food web properties: an experimental field assessment.  

PubMed

There is concern that genetically modified (GM) plants may have adverse affects on the arthropod biodiversity comprising agricultural landscapes. The present study report on a two year field experimental test of whether four different genotypic lines, some are novel with no previous field tests, of GM maize hybrids alter the structure of arthropod food webs that they harbour, relative to non-GM maize (control) that is widely used in agriculture. The different GM genotypes produced either Bt toxins, conferred glyphosate tolerance or a combination of the two traits. Quantitative food web analysis, based on short-term assessment assigning a total of 243,896 arthropod individuals collected from the treatments to their positions in food webs, revealed that complex and stable food webs persisted in each maize treatment. Moreover, food web structure remained relatively unchanged by the GM-genotype. The results suggest that at least in short-term period these particular GM maize genotypes will not have adverse effects on arthropod biota of agricultural landscapes. PMID:24937207

Szénási, Ágnes; Pálinkás, Zoltán; Zalai, Mihály; Schmitz, Oswald J; Balog, Adalbert

2014-01-01

407

Food-web structure and ecosystem services: insights from the Serengeti  

PubMed Central

The central organizing theme of this paper is to discuss the dynamics of the Serengeti grassland ecosystem from the perspective of recent developments in food-web theory. The seasonal rainfall patterns that characterize the East African climate create an annually oscillating, large-scale, spatial mosaic of feeding opportunities for the larger ungulates in the Serengeti; this in turn creates a significant annual variation in the food available for their predators. At a smaller spatial scale, periodic fires during the dry season create patches of highly nutritious grazing that are eaten in preference to the surrounding older patches of less palatable vegetation. The species interactions between herbivores and plants, and carnivores and herbivores, are hierarchically nested in the Serengeti food web, with the largest bodied consumers on each trophic level having the broadest diets that include species from a large variety of different habitats in the ecosystem. The different major habitats of the Serengeti are also used in a nested fashion; the highly nutritious forage of the short grass plains is available only to the larger migratory species for a few months each year. The longer grass areas, the woodlands and kopjes (large partially wooded rocky islands in the surrounding mosaic of grassland) contain species that are resident throughout the year; these species often have smaller body size and more specialized diets than the migratory species. Only the larger herbivores and carnivores obtain their nutrition from all the different major habitat types in the ecosystem. The net effect of this is to create a nested hierarchy of subchains of energy flow within the larger Serengeti food web; these flows are seasonally forced by rainfall and operate at different rates in different major branches of the web. The nested structure that couples sequential trophic levels together interacts with annual seasonal variation in the fast and slow chains of nutrient flow in a way that is likely to be central to the stability of the whole web. If the Serengeti is to be successfully conserved as a fully functioning ecosystem, then it is essential that the full diversity of natural habitats be maintained within the greater Serengeti ecosystem. The best way to do this is by controlling the external forces that threaten the boundaries of the ecosystem and by balancing the economic services the park provides between local, national and international needs. I conclude by discussing how the ecosystem services provided by the Serengeti are driven by species on different trophic levels. Tourism provides the largest financial revenue to the national economy, but it could be better organized to provide more sustained revenue to the park. Ultimately, ecotourism needs to be developed in ways that take lessons from the structure of the Serengeti food webs, and in ways that provide tangible benefits to people living around the park while also improving the experience of all visitors. PMID:19451118

Dobson, Andy

2009-01-01

408

Complexity of the food web structure of the Ascophyllum nodosum zone evidenced by a ?13C and ?15N study  

NASA Astrophysics Data System (ADS)

Rocky shores dominated by canopy-forming macroalgae are characterized by complex communities making it difficult to assess whether the most abundant primary producers are at the base of the food web. This difficulty is exacerbated by the seasonal- and regional-scale variations of environmental and biotic factors that can affect the main trophic pathways. The food web structure of the Ascophyllum nodosum zone was studied during three seasons and at two sites separated by several 100s of kilometers by measuring the ?13C and ?15N of the major food sources and the dominant consumers of the zone. Despite the variability in isotopic compositions, both sites underwent similar significant seasonal variations. The main primary producers of the zone, A.nodosum, Fucus vesiculosus and Fucus serratus, were not at the base of the main trophic pathway but part of the diverse number of basal resources supporting the food web. The use of community-wide metric indices allowed further defining the food web structure of the A. nodosum zone as one characterized by trophic redundancy and numerous major trophic pathways. Indeed, grazers were dominated by generalists, filter-feeders utilized both planktonic and benthic organic matter, and predators displayed a high degree of omnivory. The range of values in ?15N showed a high spatiotemporal variability within and an important overlap between trophic groups. This prevented establishing distinctive trophic levels and further emphasized the complexity of the food web structure. The spatiotemporal stability of the relative isotopic composition of the dominant consumers within trophic groups and the low variability of the community-wide indices suggested a stability of the food web structure of the A.nodosum zone at a regional scale.

Golléty, Claire; Riera, Pascal; Davoult, Dominique

2010-10-01

409

Food microbe tracker: a web-based tool for storage and comparison of food-associated microbes.  

PubMed

Large amounts of molecular subtyping information are generated by the private sector, academia, and government agencies. However, use of subtype data is limited by a lack of effective data storage and sharing mechanisms that allow comparison of subtype data from multiple sources. Currently available subtype databases are generally limited in scope to a few data types (e.g., MLST. net) or are not publicly available (e.g., PulseNet). We describe the development and initial implementation of Food Microbe Tracker, a public Web-based database that allows archiving and exchange of a variety of molecular subtype data that can be cross-referenced with isolate source data, genetic data, and phenotypic characteristics. Data can be queried with a variety of search criteria, including DNA sequences and banding pattern data (e.g., ribotype or pulsed-field gel electrophoresis type). Food Microbe Tracker allows the deposition of data on any bacterial genus and species, bacteriophages, and other viruses. The bacterial genera and species that currently have the most entries in this database are Listeria monocytogenes, Salmonella, Streptococcus spp., Pseudomonas spp., Bacillus spp., and Paenibacillus spp., with over 40,000 isolates. The combination of pathogen and spoilage microorganism data in the database will facilitate source tracking and outbreak detection, improve discovery of emerging subtypes, and increase our understanding of transmission and ecology of these microbes. Continued addition of subtyping, genetic or phenotypic data for a variety of microbial species will broaden the database and facilitate large-scale studies on the diversity of food-associated microbes. PMID:23433376

Vangay, Pajau; Fugett, Eric B; Sun, Qi; Wiedmann, Martin

2013-02-01

410

Evaluation of web-based, self-administered, graphical food frequency questionnaire.  

PubMed

Computer-administered food frequency questionnaires (FFQs) can address limitations inherent in paper questionnaires by allowing very complex skip patterns, portion size estimation based on food pictures, and real-time error checking. We evaluated a web-based FFQ, the Graphical Food Frequency System (GraFFS). Participants completed the GraFFS, six telephone-administered 24-hour dietary recalls over the next 12 weeks, followed by a second GraFFS. Participants were 40 men and 34 women, aged 18 to 69 years, living in the Columbus, OH, area. Intakes of energy, macronutrients, and 17 micronutrients/food components were estimated from the GraFFS and the mean of all recalls. Bias (second GraFFS minus recalls) was -9%, -5%, +4%, and -4% for energy and percentages of energy from fat, carbohydrate, and protein, respectively. De-attenuated, energy-adjusted correlations (intermethod reliability) between the recalls and the second GraFFS for fat, carbohydrate, protein, and alcohol were 0.82, 0.79, 0.67, and 0.90, respectively; for micronutrients/food components the median was 0.61 and ranged from 0.40 for zinc to 0.92 for beta carotene. The correlations between the two administrations of the GraFFS (test-retest reliability) for fat, carbohydrate, protein, and alcohol were 0.60, 0.63, 0.73, and 0.87, respectively; among micronutrients/food components the median was 0.67 and ranged from 0.49 for vitamin B-12 to 0.82 for fiber. The measurement characteristics of the GraFFS were at least as good as those reported for most paper FFQs, and its high intermethod reliability suggests that further development of computer-administered FFQs is warranted. PMID:24462267

Kristal, Alan R; Kolar, Ann S; Fisher, James L; Plascak, Jesse J; Stumbo, Phyllis J; Weiss, Rick; Paskett, Electra D

2014-04-01

411

Paradata for 'The flow of energy and mineral nutrients through food chains and food webs in a marsh/pond system. Animal of the marsh, their adaptations, habitat requirements and interactions.'  

NSDL National Science Digital Library

This record contains paradata for the resource 'The flow of energy and mineral nutrients through food chains and food webs in a marsh/pond system. Animal of the marsh, their adaptations, habitat requirements and interactions.'

412

Tracing Carbon Sources through Aquatic and Terrestrial Food Webs Using Amino Acid Stable Isotope Fingerprinting  

PubMed Central

Tracing the origin of nutrients is a fundamental goal of food web research but methodological issues associated with current research techniques such as using stable isotope ratios of bulk tissue can lead to confounding results. We investigated whether naturally occurring ?13C patterns among amino acids (?13CAA) could distinguish between multiple aquatic and terrestrial primary production sources. We found that ?13CAA patterns in contrast to bulk ?13C values distinguished between carbon derived from algae, seagrass, terrestrial plants, bacteria and fungi. Furthermore, we showed for two aquatic producers that their ?13CAA patterns were largely unaffected by different environmental conditions despite substantial shifts in bulk ?13C values. The potential of assessing the major carbon sources at the base of the food web was demonstrated for freshwater, pelagic, and estuarine consumers; consumer ?13C patterns of essential amino acids largely matched those of the dominant primary producers in each system. Since amino acids make up about half of organismal carbon, source diagnostic isotope fingerprints can be used as a new complementary approach to overcome some of the limitations of variable source bulk isotope values commonly encountered in estuarine areas and other complex environments with mixed aquatic and terrestrial inputs. PMID:24069196

Larsen, Thomas; Ventura, Marc; Andersen, Nils; O’Brien, Diane M.; Piatkowski, Uwe; McCarthy, Matthew D.

2013-01-01

413

Donor-Control of Scavenging Food Webs at the Land-Ocean Interface  

PubMed Central

Food webs near the interface of adjacent ecosystems are potentially subsidised by the flux of organic matter across system boundaries. Such subsidies, including carrion of marine provenance, are predicted to be instrumental on open-coast sandy shores where in situ productivity is low and boundaries are long and highly permeable to imports from the sea. We tested the effect of carrion supply on the structure of consumer dynamics in a beach-dune system using broad-scale, repeated additions of carcasses at the strandline of an exposed beach in eastern Australia. Carrion inputs increased the abundance of large invertebrate scavengers (ghost crabs, Ocypode spp.), a numerical response most strongly expressed by the largest size-class in the population, and likely due to aggregative behaviour in the short term. Consumption of carrion at the beach-dune interface was rapid and efficient, driven overwhelmingly by facultative avian scavengers. This guild of vertebrate scavengers comprises several species of birds of prey (sea eagles, kites), crows and gulls, which reacted strongly to concentrations of fish carrion, creating hotspots of intense scavenging activity along the shoreline. Detection of carrion effects at several trophic levels suggests that feeding links arising from carcasses shape the architecture and dynamics of food webs at the land-ocean interface. PMID:23826379

Schlacher, Thomas A.; Strydom, Simone; Connolly, Rod M.; Schoeman, David

2013-01-01

414

Millennial-aged organic carbon subsidies to a modern river food web.  

PubMed

Recent studies indicate that highly aged material is a major component of organic matter transported by most rivers. However, few studies have used natural 14C to trace the potential entry of this aged material into modern river food webs. Here we use natural abundance 14C, 13C, and deuterium (2H) to trace the contribution of aged and contemporary organic matter to an important group of consumers, crustacean zooplankton, in a large temperate river (the Hudson River, New York, USA). Zooplankton were highly 14C depleted (mean delta14C = -240 per thousand) compared to modern primary production in the river or its watershed (delta14C = -60 per thousand to +50 per thousand). In order to account for the observed 14C depletion, zooplankton must be subsidized by highly aged particulate organic carbon. IsoSource modeling suggests that the range of the aged dietary subsidy is between approximately 57%, if the aged organic matter source was produced 3400 years ago, and approximately 21%, if the organic carbon used is > or = 50 000 years in age, including fossil material that is millions of years in age. The magnitude of this aged carbon subsidy to river zooplankton suggests that modern river food webs may in some cases be buffered from the limitations set by present-day primary production. PMID:20836460

Caraco, Nina; Bauer, James E; Cole, Jonathan J; Petsch, Steven; Raymond, Peter

2010-08-01

415

An indicator-based evaluation of Black Sea food web dynamics during 1960-2000  

NASA Astrophysics Data System (ADS)

Four Ecopath mass-balance models were implemented for evaluating the structure and function of the Black Sea ecosystem using several ecological indicators during four distinctive periods (1960s, 1980-1987, 1988-1994 and 1995-2000). The results exemplify how the Black Sea ecosystem structure started to change after the 1960s as a result of a series of trophic transformations, i.e., shifts in the energy flow pathways through the food web. These transformations were initiated by anthropogenic factors, such as eutrophication and overfishing, that led to the transfer of large quantities of energy to the trophic dead-end species, which had no natural predators in the ecosystem, i.e., jellyfish whose biomass increased from 0.03 g C m- 2 in 1960-1969 to 0.933 g C m- 2 in 1988-1994. Concurrently, an alternative short pathway for energy transfer was formed that converted significant amounts of system production back to detritus. This decreased the transfer efficiency of energy flow from the primary producers to the higher trophic levels from 9% in the 1960s to 3% between 1980 and 1987. We conclude that the anchovy stock collapse and successful establishment of the alien comb-jelly Mnemiopsis in 1989 were rooted in the trophic interactions in the food web, all of which were exacerbated because of the long-term establishment of a combination of anthropogenic stressors.

Akoglu, Ekin; Salihoglu, Baris; Libralato, Simone; Oguz, Temel; Solidoro, Cosimo

2014-06-01

416

Invasive crayfish as vectors of mercury in freshwater food webs of the Pacific Northwest.  

PubMed

Invasive species are important drivers of environmental change in aquatic ecosystems and can alter habitat characteristics, community composition, and ecosystem energetics. Such changes have important implications for many ecosystem processes, including the bioaccumulation and biomagnification of contaminants through food webs. Mercury concentrations were measured in 2 nonnative and 1 native crayfish species from western Oregon (USA). Nonnative red swamp crayfish had mercury concentrations similar to those in native signal crayfish (0.29?±?0.05?µg/g dry wt and 0.36?±?0.06?µg/g dry wt, respectively), whereas the nonnative ringed crayfish had lower mercury concentrations (0.10?±?0.02?µg/g dry wt) than either of the other species. The mean energy content of muscle was similar between the native signal crayfish and nonnative ringed crayfish but was significantly higher in the nonnative red swamp crayfish. Across species, mercury concentrations were negatively correlated with energy density. Such energetic differences could exacerbate changes in mercury transfer through trophic pathways of food webs, especially via alterations to the growth dynamics of consumers. Thus, it is important to consider the role of energy content in determining effective mercury exposure even when mercury concentrations on a per-unit mass basis do not differ between species. Environ Toxicol Chem 2014;33:2639-2645. Published 2014 Wiley Periodicals, Inc. on behalf of SETAC. This article is a US Government work and as such, is in the public domain in the United States of America. PMID:25143076

Johnson, Branden L; Willacker, James J; Eagles-Smith, Collin A; Pearl, Christopher A; Adams, Michael J

2014-11-01

417

Distribution of PCB congeners in seven lake systems: Interactions between sediment and food-web transport  

SciTech Connect

A study was conducted to examine the role of two processes, partitioning of PCBs between sediment and biota and food-web transport, in determining the concentration of PCB congeners in the biota of seven lakes. Biota PCB concentration (lipid)-to-sediment PCB concentration (organic carbon), or BSF, ratios were calculated as markers of the partitioning of PCBs between biota and sediment, and biota PCB concentration (lipid)-to-zooplankton PCB concentration (lipid), or BAS, ratios were calculated as markers of the transport of PCBs through food webs. The lakes ranged from a shallow, well-mixed lake with a historic input of Aroclor technical mixtures to deeper, oligotrophic systems in which atmospheric deposition was the only known source. BSF ratios ranged from approximately one in cyprinids and zooplankton in all lakes to 30 in yellow perch in one lake. A significant correlation between lake maximum depth and combined BSF ratios for all biota indicated that PCBs were generally more available for accumulation in the shallower lakes, regardless of the PCB source. Principal component analysis (PCA) showed that the biota in the shallower lakes had higher ratios of higher chlorinated congeners, suggesting that predictions of equal concentrations of hydrophobic contaminants on a lipid basis in sediment and lower trophic levels may significantly underestimate the accumulation of very hydrophobic compounds in the organisms of some lake systems. BAF ratios ranged from approximately one in the lower trophic levels to approximately 10 in lake trout.

MacDonald, C.R.; Metcalfe, C.D.; Balch, G.C.; Metcalfe, T.L. (Trent Univ., Peterborough, Ontario (Canada). Environmental and Resource Studies)

1993-11-01

418

Combining food web and species distribution models for improved community projections  

PubMed Central

The ability to model biodiversity patterns is of prime importance in this era of severe environmental crisis. Species assemblage along environmental gradients is subject to the interplay of biotic interactions in complement to abiotic filtering and stochastic forces. Accounting for complex biotic interactions for a wide array of species remains so far challenging. Here, we propose using food web models that can infer the potential interaction links between species as a constraint in species distribution models. Using a plant–herbivore (butterfly) interaction dataset, we demonstrate that this combined approach is able to improve species distribution and community forecasts. The trophic interaction network between butterfly larvae and host plant was phylogenetically structured and driven by host plant nitrogen content allowing forecasting the food web model to unknown interactions links. This combined approach is very useful in rendering models of more generalist species that have multiple potential interaction links, where gap in the literature may occur. Our combined approach points toward a promising direction for modeling the spatial variation in entire species interaction networks. PMID:24340196

Pellissier, Loïc; Rohr, Rudolf P; Ndiribe, Charlotte; Pradervand, Jean-Nicolas; Salamin, Nicolas; Guisan, Antoine; Wisz, Mary

2013-01-01

419

Indirect food web interactions mediated by predator–rodent dynamics: relative roles of lemmings and voles  

PubMed Central

Production cycles in birds are proposed as prime cases of indirect interactions in food webs. They are thought to be driven by predators switching from rodents to bird nests in the crash phase of rodent population cycles. Although rodent cycles are geographically widespread and found in different rodent taxa, bird production cycles appear to be most profound in the high Arctic where lemmings dominate. We hypothesized that this may be due to arctic lemmings inducing stronger predator responses than boreal voles. We tested this hypothesis by estimating predation rates in dummy bird nests during a rodent cycle in low-Arctic tundra. Here, the rodent community consists of a spatially variable mix of one lemming (Lemmus lemmus) and two vole species (Myodes rufocanus and Microtus oeconomus) with similar abundances. In consistence with our hypothesis, lemming peak abundances predicted well crash-phase nest predation rates, whereas the vole abundances had no predictive ability. Corvids were found to be the most important nest predators. Lemmings appear to be accessible to the whole predator community which makes them particularly powerful drivers of food web dynamics. PMID:24173526

Ims, Rolf A.; Henden, John-André; Thingnes, Anders V.; Killengreen, Siw T.

2013-01-01

420

Contrasting Food Web Factor and Body Size Relationships with Hg and Se Concentrations in Marine Biota  

PubMed Central

Marine fish and shellfish are primary sources of human exposure to mercury, a potentially toxic metal, and selenium, an essential element that may protect against mercury bioaccumulation and toxicity. Yet we lack a thorough understanding of Hg and Se patterns in common marine taxa, particularly those that are commercially important, and how food web and body size factors differ in their influence on Hg and Se patterns. We compared Hg and Se content among marine fish and invertebrate taxa collected from Long Island, NY, and examined associations between Hg, Se, body length, trophic level (measured by ?15N) and degree of pelagic feeding (measured by ?13C). Finfish, particularly shark, had high Hg content whereas bivalves generally had high Se content. Both taxonomic differences and variability were larger for Hg than Se, and Hg content explained most of the variation in Hg:Se molar ratios among taxa. Finally, Hg was more strongly associated with length and trophic level across taxa than Se, consistent with a greater degree of Hg bioaccumulation in the body over time, and biomagnification through the food web, respectively. Overall, our findings indicate distinct taxonomic and ecological Hg and Se patterns in commercially important marine biota, and these patterns have nutritional and toxicological implications for seafood-consuming wildlife and humans. PMID:24019976

Karimi, Roxanne; Frisk, Michael; Fisher, Nicholas S.

2013-01-01

421

Tracing carbon sources through aquatic and terrestrial food webs using amino acid stable isotope fingerprinting.  

PubMed

Tracing the origin of nutrients is a fundamental goal of food web research but methodological issues associated with current research techniques such as using stable isotope ratios of bulk tissue can lead to confounding results. We investigated whether naturally occurring ?(13)C patterns among amino acids (?(13)CAA) could distinguish between multiple aquatic and terrestrial primary production sources. We found that ?(13)CAA patterns in contrast to bulk ?(13)C values distinguished between carbon derived from algae, seagrass, terrestrial plants, bacteria and fungi. Furthermore, we showed for two aquatic producers that their ?(13)CAA patterns were largely unaffected by different environmental conditions despite substantial shifts in bulk ?(13)C values. The potential of assessing the major carbon sources at the base of the food web was demonstrated for freshwater, pelagic, and estuarine consumers; consumer ?(13)C patterns of essential amino acids largely matched those of the dominant primary producers in each system. Since amino acids make up about half of organismal carbon, source diagnostic isotope fingerprints can be used as a new complementary approach to overcome some of the limitations of variable source bulk isotope values commonly encountered in estuarine areas and other complex environments with mixed aquatic and terrestrial inputs. PMID:24069196

Larsen, Thomas; Ventura, Marc; Andersen, Nils; O'Brien, Diane M; Piatkowski, Uwe; McCarthy, Matthew D

2013-01-01

422

Herbivore diet breadth mediates the cascading effects of carnivores in food webs  

PubMed Central

Predicting the impact of carnivores on plants has challenged community and food web ecologists for decades. At the same time, the role of predators in the evolution of herbivore dietary specialization has been an unresolved issue in evolutionary ecology. Here, we integrate these perspectives by testing the role of herbivore diet breadth as a predictor of top-down effects of avian predators on herbivores and plants in a forest food web. Using experimental bird exclosures to study a complex community of trees, caterpillars, and birds, we found a robust positive association between caterpillar diet breadth (phylodiversity of host plants used) and the strength of bird predation across 41 caterpillar and eight tree species. Dietary specialization was associated with increased enemy-free space for both camouflaged (n = 33) and warningly signaled (n = 8) caterpillar species. Furthermore, dietary specialization was associated with increased crypsis (camouflaged species only) and more stereotyped resting poses (camouflaged and warningly signaled species), but was unrelated to caterpillar body size. These dynamics in turn cascaded down to plants: a metaanalysis (n = 15 tree species) showed the beneficial effect of birds on trees (i.e., reduced leaf damage) decreased with the proportion of dietary specialist taxa composing a tree species’ herbivore fauna. We conclude that herbivore diet breadth is a key functional trait underlying the trophic effects of carnivores on both herbivores and plants. PMID:24979778

Singer, Michael S.; Lichter-Marck, Isaac H.; Farkas, Timothy E.; Aaron, Eric; Whitney, Kenneth D.; Mooney, Kailen A.

2014-01-01

423

Dreissenid mussels are not a "dead end" in Great Lakes food webs  

USGS Publications Warehouse

Dreissenid mussels have been regarded as a “dead end” in Great Lakes food webs because the degree of predation on dreissenid mussels, on a lakewide basis, is believed to be low. Waterfowl predation on dreissenid mussels in the Great Lakes has primarily been confined to bays, and therefore its effects on the dreissenid mussel population have been localized rather than operating on a lakewide level. Based on results from a previous study, annual consumption of dreissenid mussels by the round goby (Neogobius melanostomus) population in central Lake Erie averaged only 6 kilotonnes (kt; 1 kt = one thousand metric tons) during 1995–2002. In contrast, our coupling of lake whitefish (Coregonus clupeaformis) population models with a lake whitefish bioenergetics model revealed that lake whitefish populations in Lakes Michigan and Huron consumed 109 and 820 kt, respectively, of dreissenid mussels each year. Our results indicated that lake whitefish can be an important predator on dreissenid mussels in the Great Lakes, and that dreissenid mussels do not represent a “dead end” in Great Lakes food webs. The Lake Michigan dreissenid mussel population has been estimated to be growing more than three times faster than the Lake Huron dreissenid mussel population during the 2000s. One plausible explanation for the higher population growth rate in Lake Michigan would be the substantially higher predation rate by lake whitefish on dreissenid mussels in Lake Huron.

Madenijan, Char