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Sample records for zooplankton community structure

  1. COMPARISONS OF ZOOPLANKTON COMMUNITY SIZE STRUCTURE IN THE GREAT LAKES

    EPA Science Inventory

    Zooplankton mean-size and size-spectra distribution potentially reflect the condition of trophic interactions and ecosystem health because they are affected by both resource availability and planktivore pressure. We assessed zooplankton mean-size and size-spectra using an optical...

  2. Community Structure and Standing Stock of Epibenthic Zooplankton at Five Sites in Grays Harbor, Washington

    DTIC Science & Technology

    1981-09-01

    4 GRAYS HARBOR AND CHEHALIS RIVER IMPROVEMENTS TO NAVIGATION ENVIRONMENTAL STUDIES COMMUNITY STRUCTURE AND STANDING © STOCK OF EPIBENTHIC... FISHERIES RESEARCH INSTITUTE %r UNIVERSITY OF WASHINGTON B of Engineers SEPTEMBER 1981 Seattle District(DISTRIBUTION STATEM EN T. -A-8-1 2 7 Approved...PERIOD COVERED Community Structure and Standing Stock of Final May 7. 1981 Epibenthic Zooplankton at Five Sites in 6. PERFORMING ORG. REPORT NUMBER

  3. Determinants of community structure of zooplankton in heavily polluted river ecosystems

    NASA Astrophysics Data System (ADS)

    Xiong, Wei; Li, Jie; Chen, Yiyong; Shan, Baoqing; Wang, Weimin; Zhan, Aibin

    2016-02-01

    River ecosystems are among the most affected habitats globally by human activities, such as the release of chemical pollutants. However, it remains largely unknown how and to what extent many communities such as zooplankton are affected by these environmental stressors in river ecosystems. Here, we aim to determine major factors responsible for shaping community structure of zooplankton in heavily polluted river ecosystems. Specially, we use rotifers in the Haihe River Basin (HRB) in North China as a case study to test the hypothesis that species sorting (i.e. species are “filtered” by environmental factors and occur at environmental suitable sites) plays a key role in determining community structure at the basin level. Based on an analysis of 94 sites across the plain region of HRB, we found evidence that both local and regional factors could affect rotifer community structure. Interestingly, further analyses indicated that local factors played a more important role in determining community structure. Thus, our results support the species sorting hypothesis in highly polluted rivers, suggesting that local environmental constraints, such as environmental pollution caused by human activities, can be stronger than dispersal limitation caused by regional factors to shape local community structure of zooplankton at the basin level.

  4. Effects of pond management on biodiversity patterns and community structure of zooplankton in urban environments.

    PubMed

    Suski, Jamie G; Swan, Christopher M; Salice, Christopher J; Wahl, Charles F

    2018-04-01

    As urban areas continue expanding, major cities become connected forming megacities. Urban encroachment into natural areas transforms the landscape into a built environment with heterogeneously distributed patches of novel habitat. Community structure within novel habitats is influenced by anthropogenic factors including fragmentation and species interactions. Alterations in complex biodiversity patterns may be used to assess how urban stressors impact community assemblages which, ultimately, may inform sustainable management decisions. To manage algal blooms, Aquashade® is applied directly to ponds. We investigated the effects of Aquashade®, nutrient loading and dispersal on local species diversity and compositional turnover of zooplankton communities from suburban ponds in Columbia, MD, USA using a mesocosm approach. We found that Aquashade® acted as an environmental filter by increasing local species diversity and decreasing compositional turnover. This ultimately could have an overall homogenizing effect on the regional species pool (or γ-diversity). The same pattern was observed in mesocosms that received simulated dispersal events of zooplankton. Nutrients, overall, increased autotrophic biomass and while Aquashade® had no effect on autotrophic biomass, the interaction of nutrients and Aquashade® similarly caused a homogenization of the zooplankton community. Additionally, there was an overall increase in cladoceran ephippia in mesocosms receiving Aquashade® compared to those not, suggesting there is a 'trigger' switching cladocerans from parthenogenic to sexual reproduction. Taken together, our results show the application of Aquashade®, nutrient loading and dispersal shift biodiversity patterns in urban zooplankton communities. We hypothesize these shifts originate at the resource level through alterations in the phytoplankton community either through composition or nutritive value in ponds receiving Aquashade®. Our study illustrates the importance

  5. Climate-mediated changes in zooplankton community structure for the eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Eisner, Lisa B.; Napp, Jeffrey M.; Mier, Kathryn L.; Pinchuk, Alexei I.; Andrews, Alexander G.

    2014-11-01

    Zooplankton are critical to energy transfer between higher and lower trophic levels in the eastern Bering Sea ecosystem. Previous studies from the southeastern Bering Sea shelf documented substantial differences in zooplankton taxa in the Middle and Inner Shelf Domains between warm and cold years. Our investigation expands this analysis into the northern Bering Sea and the south Outer Domain, looking at zooplankton community structure during a period of climate-mediated, large-scale change. Elevated air temperatures in the early 2000s resulted in regional warming and low sea-ice extent in the southern shelf whereas the late 2000s were characterized by cold winters, extensive spring sea ice, and a well-developed pool of cold water over the entire Middle Domain. The abundance of large zooplankton taxa such as Calanus spp. (C. marshallae and C. glacialis), and Parasagitta elegans, increased from warm to cold periods, while the abundance of gelatinous zooplankton (Cnidaria) and small taxa decreased. Biomass followed the same trends as abundance, except that the biomass of small taxa in the southeastern Bering Sea remained constant due to changes in abundance of small copepod taxa (increases in Acartia spp. and Pseudocalanus spp. and decreases in Oithona spp.). Statistically significant changes in zooplankton community structure and individual species were greatest in the Middle Domain, but were evident in all shelf domains, and in both the northern and southern portions of the eastern shelf. Changes in community structure did not occur abruptly during the transition from warm to cold, but seemed to begin gradually and build as the influence of the sea ice and cold water temperatures persisted. The change occurred one year earlier in the northern than the southern Middle Shelf. These and previous observations demonstrate that lower trophic levels within the eastern Bering Sea respond to climate-mediated changes on a variety of time scales, including those shorter than

  6. Community structure of zooplankton in the main entrance of Bahía Magdalena, México during 1996.

    PubMed

    Gómez-Gutiérrez, J; Palomares-García, R; Hernández-Trujillo, S; Carballido-Carranza, A

    2001-06-01

    The zooplankton community structure, including copepods, euphausiids, chaetognaths, and decapod larvae, was monitored during six circadian cycles using Bongo net (500 microns mesh net) samples from Bahía Magdalena, on the southwest coast of Baja California, México. Samples were obtained during three oceanographic surveys (March, July, and December 1996) to describe the changes in the zooplankton community structure throughout the main mouth of Bahía Magdalena. The zooplankton community structure showed strong changes with a close relation to environmental conditions. During March, a well-mixed water column with low temperature and salinity indicated an influence of the California Current water and local upwelling processes. During July, temperature increased and a wide salinity range was recorded. The stratification of the water column was intense during summer, enhancing the thermocline. The highest temperatures and salinity were recorded in December, related to the presence of the Costa Rica Coastal Current (CRCC). The thermocline deepened as water temperature increased. A typical temperate community structure with low specific richness dominated by Calanus pacificus, Nyctiphanes simplex, and Acartia clausi and high zooplankton biomass (average 9.3 and 5.5 ml 1000 m-3 respectively) during March and July shifted to a more complex tropical community structure with a low zooplankton biomass in December (average 0.37 ml 1000 m-3). The mouth of Bahía Magdalena has a vigorous exchange of water caused by tidal currents. The zooplankton community structure was not significantly different between the central part of Bahía Magdalena and the continental shelf outside the bay for all months. The results suggest a more dynamic inside-outside interaction of zooplankton assemblages than first thought.

  7. Effects of nutrients and zooplankton on the phytoplankton community structure in Marudu Bay

    NASA Astrophysics Data System (ADS)

    Tan, Kar Soon; Ransangan, Julian

    2017-07-01

    Current study was carried out to provide a better understanding on spatial and temporal variations in the phytoplankton community structure in Marudu Bay, an important nursery ground for fishery resources within the Tun Mustapha Marine Park and Coral Triangle Initiative, and their relationship with environmental variables. Samplings were conducted monthly from April 2014 to April 2015 in Marudu Bay, Malaysia. Water samples were collected for nutrients analysis, zooplankton and phytoplankton counting. Moreover, the in situ environmental parameters were also examined. The field study showed a total of forty seven phytoplankton genera, representative of 33 families were identified. The nutrient concentrations in Marudu Bay was low (mesotrophic) throughout the year, where the phytoplankton community was often dominated by Chaetoceros spp. and Bacteriastrum spp. In general, increase in nitrate concentration triggered the bloom of centric diatom, Chaetoceros spp. and Bacteriastrum spp. in Marudu Bay. However, the bloom of these phytoplankton taxa did not occur in the presence of high ammonia concentration. In addition, high abundance of zooplankton also a limiting factor of the phytoplankton blooms particularly at end of southwest monsoon. High silica concentration promoted the growth of pennate diatoms, Proboscia spp. and Thallassionema spp., but the depletion of silica quickly terminated the bloom. Interestingly, our study showed that Chaetoceros spp., tolerated silica depletion condition, but the average cell size of this taxon reduced significantly. In summary, the phytoplankton community structure in mesotrophic environment is more sensitive to the changes in zooplankton abundance, nutrient concentration and its ratio than that in nutrient rich environments. This study also recommends that bivalve farming at industrial scale is not recommended in Marudu Bay because it potentially depletes the primary productivity hence jeopardizing the availability of live food for

  8. Spatial variations in zooplankton community structure along the Japanese coastline in the Japan Sea: influence of the coastal current

    NASA Astrophysics Data System (ADS)

    Kodama, Taketoshi; Wagawa, Taku; Iguchi, Naoki; Takada, Yoshitake; Takahashi, Takashi; Fukudome, Ken-Ichi; Morimoto, Haruyuki; Goto, Tsuneo

    2018-06-01

    This study evaluates spatial variations in zooplankton community structure and potential controlling factors along the Japanese coast under the influence of the coastal branch of the Tsushima Warm Current (CBTWC). Variations in the density of morphologically identified zooplankton in the surface layer in May were investigated for a 15-year period. The density of zooplankton (individuals per cubic meter) varied between sampling stations, but there was no consistent west-east trend. Instead, there were different zooplankton community structures in the west and east, with that in Toyama Bay particularly distinct: Corycaeus affinis and Calanus sinicus were dominant in the west and Oithona atlantica was dominant in Toyama Bay. Distance-based redundancy analysis (db-RDA) was used to characterize the variation in zooplankton community structure, and four axes (RD1-4) provided significant explanation. RD2-4 only explained < 4.8 % of variation in the zooplankton community and did not show significant spatial difference; however, RD1, which explained 89.9 % of variation, did vary spatially. Positive and negative species scores on RD1 represent warm- and cold-water species, respectively, and their variation was mainly explained by water column mean temperature, and it is considered to vary spatially with the CBTWC. The CBTWC intrusion to the cold Toyama Bay is weak and occasional due to the submarine canyon structure of the bay. Therefore, the varying bathymetric characteristics along the Japanese coast of the Japan Sea generate the spatial variation in zooplankton community structure, and dominance of warm-water species can be considered an indicator of the CBTWC.

  9. Seasonal variation of zooplankton abundance and community structure in Prince William Sound, Alaska, 2009-2016

    NASA Astrophysics Data System (ADS)

    McKinstry, Caitlin A. E.; Campbell, Robert W.

    2018-01-01

    Large calanoid copepods and other zooplankters comprise the prey field for ecologically and economically important predators such as juvenile pink salmon, herring, and seabirds in Prince William Sound (PWS).​ From 2009-2016, the Gulf Watch Alaska program collected zooplankton 5-10 times each year at 12 stations in PWS to establish annual patterns. Surveys collected 188 species of zooplankton with Oithona similis, Limacina helicina, Pseudocalanus spp., and Acartia longiremis as the most common species present in 519 samples. Generalized additive models assessed seasonal abundance and showed peak abundance in July (mean: 9826 no. m-3 [95% CI: 7990-12,084]) and lowest abundance in January (503 no. m-3 [373 to 678]). Significantly higher zooplankton abundance occurred in 2010 (542 no. m-3 ± 55 SE) and lowest in 2013 (149 no. m-3 ± 13). The species composition of communities, determined via hierarchical cluster analysis and indicator species analysis, produced six distinct communities based on season and location. The winter community, characterized by warm-water indicator species including Mesocalanus tenuicornis, Calanus pacificus, and Corycaeus anglicus, diverged into four communities throughout the spring and summer. The first spring community, characterized by copepods with affinities for lower salinities, occurred sound-wide. The second spring community, comprised of planktonic larvae, appeared sporadically in PWS bays in 2011-2013. Spring and summer open water stations were defined by the presence of large calanoid copepods. A summer community including the most abundant taxa was common in 2010 and 2011, absent in 2013, then sporadically appeared in 2014 and 2015 suggesting interannual variability of zooplankton assemblages. The zooplankton community shifted to a uniform assemblage characterized by cnidarians in the early autumn. Community assemblages showed significant correlations to a set of environmental variables including SST, mixed layer depth

  10. [Effects of large bio-manipulation fish pen on community structure of crustacean zooplankton in Meiliang Bay of Taihu Lake].

    PubMed

    Ke, Zhi-Xin; Xie, Ping; Guo, Long-Gen; Xu, Jun; Zhou, Qiong

    2012-08-01

    In 2005, a large bio-manipulation pen with the stock of silver carp and bighead carp was built to control the cyanobacterial bloom in Meiliang Bay of Taihu Lake. This paper investigated the seasonal variation of the community structure of crustacean zooplankton and the water quality within and outside the pen. There were no significant differences in the environmental parameters and phytoplankton biomass within and outside the pen. The species composition and seasonal dynamics of crustacean zooplankton within and outside the pen were similar, but the biomass of crustacean zooplankton was greatly suppressed by silver carp and bighead carp. The total crustacean zooplankton biomass and cladocerans biomass were significantly lower in the pen (P < 0.05). In general, silver carp and bighead carp exerted more pressure on cladoceran species than on copepod species. A distinct seasonal succession of crustacean zooplankton was observed in the Bay. Many crustacean species were only dominated in given seasons. Large-sized crustacean (mainly Daphnia sp. and Cyclops vicnus) dominated in winter and spring, while small-sized species (mainly Bosmina sp., Ceriodaphnia cornuta, and Limnoithona sinensis) dominated in summer and autumn. Canonical correspondence analysis showed that water transparency, temperature, and phytoplankton biomass were the most important factors affecting the seasonal succession of the crustacean.

  11. The synergetic effects of turbulence and turbidity on the zooplankton community structure in large, shallow Lake Taihu.

    PubMed

    Zhou, Jian; Qin, Boqiang; Han, Xiaoxia

    2018-01-01

    Climate change is predicted to influence the heat budget of aquatic ecosystems and, in turn, affect the stability of the water column leading to increased turbulence coupled with enhanced turbidity. However, the synergetic effects of turbulence and turbidity on zooplankton community structure remain to be understood in large, shallow lakes. To determine the possible synergetic effects of these factors on zooplankton communities, a 15-day mesocosm experiment was carried out and tested under four turbulence and turbidity regimes namely control (ɛ = 0, 7.6 ± 4.2 NTU), low (ɛ = 6.01 × 10 -8  m 2  s -3 , 19.4 ± 8.6 NTU), medium (ɛ = 2.95 × 10 -5  m 2  s -3 , 55.2 ± 14.4 NTU), and high (ɛ = 2.39 × 10 -4  m 2  s -3 , 741.6 ± 105.2 NTU) conditions, which were comparable to the natural conditions in Lake Taihu. Results clearly showed the negative effects of turbulence and turbidity on zooplankton survival, which also differed among taxa. Specifically, increased turbulence and turbidity levels influenced the competition among zooplankton species, which resulted to the shift from being large body crustacean-dominated (copepods and cladocerans) to rotifer-dominated community after 3 days. The shift could be associated with the decrease in vulnerability of crustaceans in such environments. Our findings suggested that changes in the level of both turbidity and turbulence in natural aquatic systems would have significant repercussions on the zooplankton communities, which could contribute to the better understanding of community and food web dynamics in lake ecosystems exposed to natural mixing/disturbances.

  12. Zooplankton community structure during a transition from dry to wet state in a shallow, subtropical estuarine lake

    NASA Astrophysics Data System (ADS)

    Carrasco, Nicola K.; Perissinotto, Renzo

    2015-12-01

    Lake St Lucia is among the most important shallow ecosystems globally and Africa's largest estuarine lake. It has long been regarded as a resilient system, oscillating through periods of hypersalinity and freshwater conditions, depending on the prevailing climate. The alteration of the system's catchment involving the diversion of the Mfolozi River away from Lake St Lucia, however, challenged the resilience of the system, particularly during the most recent drought (2002-2011), sacrificing much of its biodiversity. This study reports on the transition of the St Lucia zooplankton community from a dry hypersaline state to a new wet phase. Sampling was undertaken during routine quarterly surveys at five representative stations along the lake system from February 2011 to November 2013. A total of 54 taxa were recorded during the study period. The zooplankton community was numerically dominated by the calanoid copepods Acartiella natalensis and Pseudodiaptomus stuhlmanni and the cyclopoid copepod Oithona brevicornis. While the mysid Mesopodopsis africana was still present in the system during the wet phase, it was not found in the swarming densities that were recorded during the previous dry phase, possibly due to increased predation pressure, competition with other taxa and or the reconnection with the Mfolozi River via a beach spillway. The increase in zooplankton species richness recorded during the present study shows that the system has undergone a transition to wet state, with the zooplankton community structure reflecting that recorded during the past. It is likely, though, that only a full restoration of natural mouth functioning will result in further diversity increases.

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

    PubMed

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

    2017-11-01

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

  14. Late-summer zooplankton community structure, abundance, and distribution in the Hudson Bay system (Canada) and their relationships with environmental conditions, 2003-2006

    NASA Astrophysics Data System (ADS)

    Estrada, Rafael; Harvey, Michel; Gosselin, Michel; Starr, Michel; Galbraith, Peter S.; Straneo, Fiammetta

    2012-08-01

    weakly stratified Arctic-North Atlantic waters coming from southwestern Davis Strait (inflow). In general, the RDA models tested among the HBS regions were very consistent with its general surface circulation pattern for summer conditions in terms of environmental variables and distinct zooplankton assemblages. Overall, zooplankton biomass and diversity indices (H‧, J‧, and S) were lower in the most stratified environment (i.e., HB) than in the deeper (FB) and more dynamic (HS) regions. The results of this work clearly show that the spatial differentiation and structure of the zooplankton communities are strongly influenced by the hydrodynamic conditions in the HBS that, trough their actions on temperature, salinity, stratification, mixing conditions and depth strata, lead to the spatial differentiation of these communities.

  15. Planktivory in the changing Lake Huron zooplankton community: Bythotrephes consumption exceeds that of Mysis and fish

    Bunnell, D.B.; Hunter, R. Douglas; Warner, D.M.; Chriscinske, M.A.; Roseman, E.F.

    2011-01-01

    Oligotrophic lakes are generally dominated by calanoid copepods because of their competitive advantage over cladocerans at low prey densities. Planktivory also can alter zooplankton community structure. We sought to understand the role of planktivory in driving recent changes to the zooplankton community of Lake Huron, a large oligotrophic lake on the border of Canada and the United States. We tested the hypothesis that excessive predation by fish (rainbow smelt Osmerus mordax, bloater Coregonus hoyi) and invertebrates (Mysis relicta, Bythotrephes longimanus) had driven observed declines in cladoceran and cyclopoid copepod biomass between 2002 and 2007. We used a field sampling and bioenergetics modelling approach to generate estimates of daily consumption by planktivores at two 91-m depth sites in northern Lake Huron, U.S.A., for each month, May-October 2007. Daily consumption was compared to daily zooplankton production. Bythotrephes was the dominant planktivore and estimated to have eaten 78% of all zooplankton consumed. Bythotrephes consumption exceeded total zooplankton production between July and October. Mysis consumed 19% of all the zooplankton consumed and exceeded zooplankton production in October. Consumption by fish was relatively unimportant - eating only 3% of all zooplankton consumed. Because Bythotrephes was so important, we explored other consumption estimation methods that predict lower Bythotrephes consumption. Under this scenario, Mysis was the most important planktivore, and Bythotrephes consumption exceeded zooplankton production only in August. Our results provide no support for the hypothesis that excessive fish consumption directly contributed to the decline of cladocerans and cyclopoid copepods in Lake Huron. Rather, they highlight the importance of invertebrate planktivores in structuring zooplankton communities, especially for those foods webs that have both Bythotrephes and Mysis. Together, these species occupy the epi-, meta- and

  16. Zooplankton species composition, abundance and biomass on the eastern Bering Sea shelf during summer: The potential role of water-column stability and nutrients in structuring the zooplankton community

    NASA Astrophysics Data System (ADS)

    Coyle, Kenneth O.; Pinchuk, Alexei I.; Eisner, Lisa B.; Napp, Jeffrey M.

    2008-08-01

    The southeastern Bering Sea sustains one of the largest fisheries in the United States, as well as wildlife resources that support valuable tourist and subsistence economies. The fish and wildlife populations in turn are sustained by a food web linking primary producers to apex predators through the zooplankton community. Recent shifts in climate toward warmer conditions may threaten these resources by altering productivity and trophic relationships in the ecosystem on the southeastern Bering Sea shelf. We examined the zooplankton community near the Pribilof Islands and on the middle shelf of the southeastern Bering Sea in summer of 1999 and 2004 to document differences and similarities in species composition, abundance and biomass by region and year. Between August 1999 and August 2004, the summer zooplankton community of the middle shelf shifted from large to small species. Significant declines were observed in the biomass of large scyphozoans ( Chrysaora melanaster), large copepods ( Calanus marshallae), arrow worms ( Sagitta elegans) and euphausiids ( Thysanoessa raschii, T. inermis) between 1999 and 2004. In contrast, significantly higher densities of the small copepods ( Pseudocalanus spp., Oithona similis) and small hydromedusae ( Euphysa flammea) were observed in 2004 relative to 1999. Stomach analyses of young-of-the-year (age 0) pollock ( Theragra chalcogramma) from the middle shelf indicated a dietary shift from large to small copepods in 2004 relative to 1999. The shift in the zooplankton community was accompanied by a 3-fold increase in water-column stability in 2004 relative to 1999, primarily due to warmer water above the thermocline, with a mean temperature of 7.3 °C in 1999 and 12.6 °C in 2004. The elevated water-column stability and warmer conditions may have influenced the zooplankton composition by lowering summer primary production and selecting for species more tolerant of a warm, oligotrophic environment. A time series of temperature from

  17. The impact of fish predation and cyanobacteria on zooplankton size structure in 96 subtropical lakes.

    PubMed

    Zhang, Jing; Xie, Ping; Tao, Min; Guo, Longgen; Chen, Jun; Li, Li; Xuezhen Zhang; Zhang, Lu

    2013-01-01

    Zooplankton are relatively small in size in the subtropical regions. This characteristic has been attributed to intense predation pressure, high nutrient loading and cyanobacterial biomass. To provide further information on the effect of predation and cyanobacteria on zooplankton size structure, we analyzed data from 96 shallow aquaculture lakes along the Yangtze River. Contrary to former studies, both principal components analysis and multiple regression analysis showed that the mean zooplankton size was positively related to fish yield. The studied lakes were grouped into three types, namely, natural fishing lakes with low nutrient loading (Type1), planktivorous fish-dominated lakes (Type 2), and eutrophic lakes with high cyanobacterial biomass (Type 3). A marked difference in zooplankton size structure was found among these groups. The greatest mean zooplankton size was observed in Type 2 lakes, but zooplankton density was the lowest. Zooplankton abundance was highest in Type 3 lakes and increased with increasing cyanobacterial biomass. Zooplankton mean size was negatively correlated with cyanobacterial biomass. No obvious trends were found in Type 1 lakes. These results were reflected by the normalized biomass size spectrum, which showed a unimodal shape with a peak at medium sizes in Type 2 lakes and a peak at small sizes in Type 3 lakes. These results indicated a relative increase in medium-sized and small-sized species in Types 2 and 3 lakes, respectively. Our results suggested that fish predation might have a negative effect on zooplankton abundance but a positive effect on zooplankton size structure. High cyanobacterial biomass most likely caused a decline in the zooplankton size and encouraged the proliferation of small zooplankton. We suggest that both planktivorous fish and cyanobacteria have substantial effects on the shaping of zooplankton community, particularly in the lakes in the eastern plain along the Yangtze River where aquaculture is widespread

  18. The Impact of Fish Predation and Cyanobacteria on Zooplankton Size Structure in 96 Subtropical Lakes

    PubMed Central

    Zhang, Jing; Xie, Ping; Tao, Min; Guo, Longgen; Chen, Jun; Li, Li; XueZhen Zhang; Zhang, Lu

    2013-01-01

    Zooplankton are relatively small in size in the subtropical regions. This characteristic has been attributed to intense predation pressure, high nutrient loading and cyanobacterial biomass. To provide further information on the effect of predation and cyanobacteria on zooplankton size structure, we analyzed data from 96 shallow aquaculture lakes along the Yangtze River. Contrary to former studies, both principal components analysis and multiple regression analysis showed that the mean zooplankton size was positively related to fish yield. The studied lakes were grouped into three types, namely, natural fishing lakes with low nutrient loading (Type1), planktivorous fish-dominated lakes (Type 2), and eutrophic lakes with high cyanobacterial biomass (Type 3). A marked difference in zooplankton size structure was found among these groups. The greatest mean zooplankton size was observed in Type 2 lakes, but zooplankton density was the lowest. Zooplankton abundance was highest in Type 3 lakes and increased with increasing cyanobacterial biomass. Zooplankton mean size was negatively correlated with cyanobacterial biomass. No obvious trends were found in Type 1 lakes. These results were reflected by the normalized biomass size spectrum, which showed a unimodal shape with a peak at medium sizes in Type 2 lakes and a peak at small sizes in Type 3 lakes. These results indicated a relative increase in medium-sized and small-sized species in Types 2 and 3 lakes, respectively. Our results suggested that fish predation might have a negative effect on zooplankton abundance but a positive effect on zooplankton size structure. High cyanobacterial biomass most likely caused a decline in the zooplankton size and encouraged the proliferation of small zooplankton. We suggest that both planktivorous fish and cyanobacteria have substantial effects on the shaping of zooplankton community, particularly in the lakes in the eastern plain along the Yangtze River where aquaculture is widespread

  19. Zooplankton community analysis in the Changjiang River estuary by single-gene-targeted metagenomics

    NASA Astrophysics Data System (ADS)

    Cheng, Fangping; Wang, Minxiao; Li, Chaolun; Sun, Song

    2014-07-01

    DNA barcoding provides accurate identification of zooplankton species through all life stages. Single-gene-targeted metagenomic analysis based on DNA barcode databases can facilitate longterm monitoring of zooplankton communities. With the help of the available zooplankton databases, the zooplankton community of the Changjiang (Yangtze) River estuary was studied using a single-gene-targeted metagenomic method to estimate the species richness of this community. A total of 856 mitochondrial cytochrome oxidase subunit 1 (cox1) gene sequences were determined. The environmental barcodes were clustered into 70 molecular operational taxonomic units (MOTUs). Forty-two MOTUs matched barcoded marine organisms with more than 90% similarity and were assigned to either the species (similarity>96%) or genus level (similarity<96%). Sibling species could also be distinguished. Many species that were overlooked by morphological methods were identified by molecular methods, especially gelatinous zooplankton and merozooplankton that were likely sampled at different life history phases. Zooplankton community structures differed significantly among all of the samples. The MOTU spatial distributions were influenced by the ecological habits of the corresponding species. In conclusion, single-gene-targeted metagenomic analysis is a useful tool for zooplankton studies, with which specimens from all life history stages can be identified quickly and effectively with a comprehensive database.

  20. Some ecological implications of a neem (azadirachtin) insecticide disturbance to zooplankton communities in forest pond enclosures.

    PubMed

    Kreutzweiser, David P; Sutton, Trent M; Back, Richard C; Pangle, Kevin L; Thompson, Dean G

    2004-04-28

    A neem-based insecticide, Neemix 4.5, was applied to forest pond enclosures at concentrations of 10, 17, and 28 microg l(-1) azadirachtin (the active ingredient). At these test concentrations, significant, concentration-dependent reductions in numbers of adult copepods were observed, but immature copepod and cladoceran populations were unaffected. There was no evidence of recovery of adult copepods within the sampling season (May to October). The ecological significance of this disturbance to the zooplankton community was examined by determining biomass as a measure of food availability for higher predators, plankton community respiration, dissolved oxygen (DO) concentrations, and conductivity as functional indicators of ecosystem stress, and zooplankton food web stability as a measure of effects on trophic structure. The selective removal or reduction of adult copepods was sufficient to measurably reduce total zooplankton biomass for several weeks mid-season. During the period of maximal impact (about 4-9 weeks after the applications), total plankton community respiration was significantly reduced, and this appeared to contribute to significant, concentration-dependent increases in dissolved oxygen and decreases in conductivity among treated enclosures. The reductions in adult copepods resulted in negative effects on zooplankton food web stability through eliminations of a trophic link and reduced interactions and connectance. Comparing the results here to those from a previous study with tebufenozide, which was selectively toxic to cladocerans and had little effect on food web stability, indicates that differential sensitivity among taxa can influence the ecological significance of pesticide effects on zooplankton communities.

  1. FORAGE FISH AND ZOOPLANKTON COMMUNITY COMPOSITION IN WESTERN LAKE SUPERIOR

    EPA Science Inventory

    We assessed the abundance, size, and species composition of the fish and zooplankton communities of western Lake Superior during 1996 and 1997. Data were analyzed for 3 ecoregions (Duluth-Superior (1), Apostle Islands (2), Minnesota coast (3) differing in lake bathymetry, phsiodo...

  2. Variability of zooplankton communities at Condor seamount and surrounding areas, Azores (NE Atlantic)

    NASA Astrophysics Data System (ADS)

    Carmo, Vanda; Santos, Mariana; Menezes, Gui M.; Loureiro, Clara M.; Lambardi, Paolo; Martins, Ana

    2013-12-01

    Seamounts are common topographic features around the Azores archipelago (NE Atlantic). Recently there has been increasing research effort devoted to the ecology of these ecosystems. In the Azores, the mesozooplankon is poorly studied, particularly in relation to these seafloor elevations. In this study, zooplankton communities in the Condor seamount area (Azores) were investigated during March, July and September 2010. Samples were taken during both day and night with a Bongo net of 200 µm mesh that towed obliquely within the first 100 m of the water column. Total abundance, biomass and chlorophyll a concentrations did not vary with sampling site or within the diel cycle but significant seasonal variation was observed. Moreover, zooplankton community composition showed the same strong seasonal pattern regardless of spatial or daily variability. Despite seasonal differences, the zooplankton community structure remained similar for the duration of this study. Seasonal variability better explained our results than mesoscale spatial variability. Spatial homogeneity is probably related with island proximity and local dynamics over Condor seamount. Zooplankton literature for the region is sparse, therefore a short review of the most important zooplankton studies from the Azores is also presented.

  3. High frequency mesozooplankton monitoring: Can imaging systems and automated sample analysis help us describe and interpret changes in zooplankton community composition and size structure — An example from a coastal site

    NASA Astrophysics Data System (ADS)

    Romagnan, Jean Baptiste; Aldamman, Lama; Gasparini, Stéphane; Nival, Paul; Aubert, Anaïs; Jamet, Jean Louis; Stemmann, Lars

    2016-10-01

    The present work aims to show that high throughput imaging systems can be useful to estimate mesozooplankton community size and taxonomic descriptors that can be the base for consistent large scale monitoring of plankton communities. Such monitoring is required by the European Marine Strategy Framework Directive (MSFD) in order to ensure the Good Environmental Status (GES) of European coastal and offshore marine ecosystems. Time and cost-effective, automatic, techniques are of high interest in this context. An imaging-based protocol has been applied to a high frequency time series (every second day between April 2003 to April 2004 on average) of zooplankton obtained in a coastal site of the NW Mediterranean Sea, Villefranche Bay. One hundred eighty four mesozooplankton net collected samples were analysed with a Zooscan and an associated semi-automatic classification technique. The constitution of a learning set designed to maximize copepod identification with more than 10,000 objects enabled the automatic sorting of copepods with an accuracy of 91% (true positives) and a contamination of 14% (false positives). Twenty seven samples were then chosen from the total copepod time series for detailed visual sorting of copepods after automatic identification. This method enabled the description of the dynamics of two well-known copepod species, Centropages typicus and Temora stylifera, and 7 other taxonomically broader copepod groups, in terms of size, biovolume and abundance-size distributions (size spectra). Also, total copepod size spectra underwent significant changes during the sampling period. These changes could be partially related to changes in the copepod assemblage taxonomic composition and size distributions. This study shows that the use of high throughput imaging systems is of great interest to extract relevant coarse (i.e. total abundance, size structure) and detailed (i.e. selected species dynamics) descriptors of zooplankton dynamics. Innovative

  4. Impacts of hypoxia on the structure and processes in the pelagic community (zooplankton, macro-invertebrates and fish)

    NASA Astrophysics Data System (ADS)

    Ekau, W.; Auel, H.; Pörtner, H.-O.; Gilbert, D.

    2009-05-01

    Dissolved oxygen (DO) concentration in the water column is an environmental parameter that is crucial for the successful development of many pelagic organisms. Hypoxia tolerance and threshold values are species- and stage-specific and can vary enormously. While some fish species may suffer from oxygen values of less than 3 ml L-1 and show impact on growth, development and behaviour, other organisms such as euphausiids may survive DO levels as low as 0.1 ml L-1. A change in the average or the minimum or maximum DO in an area may have significant impacts on the survival of certain species and hence on the species composition in the ecosystem with consequent changes in trophic pathways and productivity. Evidence of the deleterious effects of oxygen depletion on species of the pelagic realm is scarce, particularly in terms of the effect of low oxygen on development, recruitment and patterns of migration and distribution. While planktonic organisms have to cope with different DOs and find adaptive mechanisms, nektonic species may avoid areas of inconvenient DO and develop adapted migrational strategies. Planktonic organisms may only be able to escape vertically, above or beneath the Oxygen Minimum Zone (OMZ). In shallow areas only the surface layer can serve as a refuge, in deep waters many organisms have developed vertical migration strategies to use, pass and cope with the OMZ. This paper elucidates the role of DO for different taxa in the pelagic realm and the consequences of low oxygen for foodweb structure and system productivity.

  5. Impacts of hypoxia on the structure and processes in pelagic communities (zooplankton, macro-invertebrates and fish)

    NASA Astrophysics Data System (ADS)

    Ekau, W.; Auel, H.; Pörtner, H.-O.; Gilbert, D.

    2010-05-01

    Dissolved oxygen (DO) concentration in the water column is an environmental parameter that is crucial for the successful development of many pelagic organisms. Hypoxia tolerance and threshold values are species- and stage-specific and can vary enormously. While some fish species may suffer from oxygen values of less than 3 mL O2 L-1 through impacted growth, development and behaviour, other organisms such as euphausiids may survive DO levels as low as 0.1 mL O2 L-1. A change in the average or the range of DO may have significant impacts on the survival of certain species and hence on the species composition in the ecosystem with consequent changes in trophic pathways and productivity. Evidence for the deleterious effects of oxygen depletion on pelagic species is scarce, particularly in terms of the effect of low oxygen on development, recruitment and patterns of migration and distribution. While planktonic organisms have to cope with variable DOs and exploit adaptive mechanisms, nektonic species may avoid areas of unfavourable DO and develop adapted migration strategies. Planktonic organisms may only be able to escape vertically, above or beneath the Oxygen Minimum Zone (OMZ). In shallow areas only the surface layer can serve as a refuge, but in deep waters many organisms have developed vertical migration strategies to use, pass through and cope with the OMZ. This paper elucidates the role of DO for different taxa in the pelagic realm and the consequences of low oxygen for foodweb structure and system productivity. We describe processes in two contrasting systems, the semi-enclosed Baltic Sea and the coastal upwelling system of the Benguela Current to demonstrate the consequences of increasing hypoxia on ecosystem functioning and services.

  6. Effects of physical forcing on COastal ZOoplankton community structure: study of the unusual case of a MEDiterranean ecosystem under strong tidal influence (Project COZOMED-MERMEX)

    NASA Astrophysics Data System (ADS)

    Pagano, Marc

    2017-04-01

    Groupe COZOMED: R. Arfi (1), A. Atoui (2), H. Ayadi (6), B. Bejaoui (1), N. Bhairy (1), N. Barraj (2), M. Belhassen (2), S. Benismail (2), M.Y Benkacem (2), J. Blanchot (1), M. Cankovic(5), F. Carlotti (1), C. Chevalier (1), I Ciglenecki-Jusic (5), D. Couet (1), N. Daly Yahia (3), L. Dammak (2), J.-L. Devenon (1), Z. Drira (6), A. Hamza (2), S. Kmia (6), N. Makhlouf (3), M. Mahfoudi (2), M. Moncef (4), M. Pagano (1), C. Sammari (2), H. Smeti (2), A. Zouari (2) The COZOMED-MERMEX project aims at understanding how hydrodynamic forcing (currents, tides, winds) combine with anthropogenic forcing and climate to affect the variability of coastal Mediterranean zooplankton communities under contrasting tidal influence. This study includes (i) a zero state of knowledge via a literature review of existing data and (ii) a case study on the system Boughrara lagoon - Gulf of Gabes. This ecosystem gives major services for Tunisia (about 65% of national fish production) but is weakened by its situation in a heavily anthropized area and under influence of urban, industrial and agricultural inputs. Besides this region is subject to specific climate forcing (Sahelian winds, scorching heat, intense evaporation, flooding) which possible changes will be considered. The expected issues are (i) to improve our knowledge of hydrodynamic forcing on zooplankton and ultimately on the functioning of coastal Mediterranean ecosystems impacted by anthropogenic and climatic effects and (ii) to elaborate management tools to help preserving good ecological status of these ecosystems: hydrodynamic circulation model, mapping of isochrones of residence times, mapping of the areas of highest zooplankton abundances (swarms), and sensitive areas, etc. This project strengthens existing scientific collaborations within the MERMEX program (The MerMex Group, 2011) and in the frame of an international joint laboratory (COSYS-Med) created in 2014. A first field mulidisciplinary campaign was performed in October

  7. The Lake Ontario zooplankton community before (1987-1991) and after (2001-2005) invasion-induced ecosystem change

    Stewart, T.J.; Johannsson, O.E.; Holeck, K.; Sprules, W.G.; O'Gorman, R.

    2010-01-01

    We assessed changes in Lake Ontario zooplankton biomass, production, and community composition before (1987–1991) and after (2001–2005) invasion-induced ecosystem changes. The ecosystem changes were associated with establishment of invasive dreissenid mussels and invasive predatory cladocerans (Bythotrephes and Cercopagis). Whole-lake total epilimnetic plus metalimnetic zooplankton production declined by approximately half from 42.45 (g dry wt∙m−2∙ year−1) during 1987–1991 to 21.91 (g dry wt∙m−2∙ year−1) in 2003 and averaged 21.01 (g dry wt∙m−2∙ year−1) during 2001–2005. Analysis of two independent data sets indicates that the mean biomass and biomass proportion of cyclopoid copepods declined while the same measures increased for the invasive predatory cladocerans. Changes in means and proportions of all other zooplankton groups were not consistent between the data sets. Cyclopoid copepod biomass and production declined by factors ranging from 3.6 to 5.7. Invasive predatory cladoceran biomass averaged from 5.0% to 8.0% of the total zooplankton biomass. The zooplankton community was otherwise resilient to the invasion-induced disruption as zooplankton species richness and diversity were unaffected. Zooplankton production was likely reduced by declines in primary productivity but may have declined further due to increased predation by alewives and invasive predatory cladocerans. Shifts in zooplankton community structure were consistent with increased predation pressure on cyclopoid copepods by alewives and invasive predatory cladocerans. Predicted declines in the proportion of small cladocerans were not evident. This study represents the first direct comparison of changes in Lake Ontario zooplankton production before and after the invasion-induced disruption and will be important to food web-scale investigations of invasion effects.

  8. Indicators: Zooplankton

    EPA Pesticide Factsheets

    Zooplankton are small, free-floating aquatic microorganisms including crustaceans, rotifers, open water insect larvae, and aquatic mites. The zooplankton community is composed of both primary consumers and secondary consumers.

  9. Fate of thiamethoxam in mesocosms and response of the zooplankton community.

    PubMed

    Lobson, C; Luong, K; Seburn, D; White, M; Hann, B; Prosser, R S; Wong, C S; Hanson, M L

    2018-05-14

    Thiamethoxam is a neonicotinoid insecticide that can reach wetlands in agro-ecosystems through runoff. The fate and effects of thiamethoxam on non-target organisms in shallow wetland ecosystems have not been well characterized. To this end, a mesocosm study was conducted with a focus on characterizing zooplankton community responses. A single pulse application of thiamethoxam (0, 25, 50, 100, 250, and 500 μg/L; n = 3) was applied to experimental systems and monitored for 8 weeks. The mean half-life of thiamethoxam among the different treatments was 3.7 days in the water column with concentrations of <0.8 μg/L in the majority of mesocosms by 56 days. Principal response curve analysis did not show any significant concentration-dependent differences in the zooplankton community among treatments over the course of the study. The minimum detectable difference (MDD%) values for abundance of potentially sensitive arthropod taxa (nauplius larvae, cyclopoid copepods) allowed the detections from controls as low as 42 and 59% effect, respectively. The MDD% values for total abundance of zooplankton (including the potentially less sensitive taxonomic group of Rotifera) allowed the detection from controls as low as 41% effect. There were no statistically significant differences in zooplankton abundance or diversity between control and treated mesocosms at the end of the study. There were also no statistically significant differences for individual taxa that were sustained between sampling points, or manifested as a concentration-response. We conclude that acute exposure to thiamethoxam at environmentally relevant concentrations (typically ng/L) likely does not represent a significant adverse ecological risk to wetland zooplankton community abundance and structure. Copyright © 2018 Elsevier B.V. All rights reserved.

  10. Community response of zooplankton to oceanographic changes (2002-2012) in the central/southern upwelling system of Chile

    NASA Astrophysics Data System (ADS)

    Medellín-Mora, Johanna; Escribano, Ruben; Schneider, Wolfgang

    2016-03-01

    A 10-year time series (2002-2012) at Station 18 off central/southern Chile allowed us to study variations in zooplankton along with interannual variability and trends in oceanographic conditions. We used an automated analysis program (ZooImage) to assess changes in the mesozooplankton size structure and the composition of the taxa throughout the entire community. Oceanographic conditions changed over the decade: the water column became less stratified, more saline, and colder; the mixed layer deepened; and the oxygen minimum zone became shallower during the second half of the time series (2008-2012) in comparison with the first period (2002-2007). Both the size structure and composition of the zooplankton were significantly associated with oceanographic changes. Taxonomic and size diversity of the zooplankton community increased to the more recent period. For the second period, small sized copepods (<1 mm) decreased in abundance, being replaced by larger sized (>1.5 mm) and medium size copepods (1-1.5 mm), whereas euphausiids, decapod larvae, appendicularian and ostracods increased their abundance during the second period. These findings indicated that the zooplankton community structure in this eastern boundary ecosystem was strongly influenced by variability of the upwelling process. Thus, climate-induced forcing of upwelling trends can alter the zooplankton community in this highly productive region with potential consequences for the ecosystem food web.

  11. The Interactive Effect of Multiple Stressors on Crustacean Zooplankton Communities in Montane Lakes

    NASA Astrophysics Data System (ADS)

    Brittain, Jeffrey T.; Strecker, Angela L.

    2018-02-01

    Nonnative fish introductions have altered thousands of naturally fishless montane lakes, resulting in cascading food web repercussions. Nitrogen deposition has been recognized as an anthropogenic contributor to acidification and eutrophication of freshwater ecosystems, which may affect the abundance and composition of planktonic communities. This study identified responses of zooplankton communities from two lakes (fish present versus absent) in Mount Rainier National Park to manipulations simulating an episodic disturbance of acidification and eutrophication via nitrogen addition in mesocosms. Zooplankton communities from lakes with different food web structure (i.e., fish present or absent) responded differently to the singular effects of acid and nitrogen addition. For instance, zooplankton biomass decreased in the acid treatment of the fishless lake experiment, but increased in response to acid in the fish-present experiment. In contrast, the combination of acid and nitrogen often resulted in weak responses for both lake types, resulting in nonadditive effects, i.e., the net effect of the stressors was in the opposite direction than predicted, which is known as a reversal or "ecological surprise." This experiment demonstrates the difficulty in predicting the interactive effects of multiple stressors on aquatic communities, which may pose significant challenges for habitat restoration through fish removal.

  12. Metabarcoding Baseline for the Sargasso Sea Zooplankton Community

    NASA Astrophysics Data System (ADS)

    Blanco-Bercial, L.; Alam, S.

    2016-02-01

    Understanding the responses and evolution of any community over space and time requires a deep knowledge of the species present at each location and their interactions. Where taxonomy turns out to be challenging, as it is in the case of zooplankton, supra-species grouping is a common resort in community characterization. Although this makes morphological identification manageable, there is the associated price of a limited depth of study and the risk of mixing different species' organismal responses. As global change begins to influence species distributions and physiologies, it becomes ever more important to discriminate at a species specific level. The development of DNA-based identification protocols during the last decades are rapidly driving these limitations away, increasing our understanding of the existing complexity of even very close taxa to different stressors or environmental conditions. Beyond the mere taxonomic discrimination of the analyzed community, the use of DNA sequences allows for the rapid integration of phylogenetic measurements and related indexes. In this presentation, we show our first results tackling one of the regions with the highest zooplankton diversity, the Subtropical North Atlantic at the Bermuda Atlantic Time-Series Study (BATS) site. The chosen metabarcoding region was the hypervariable V9 region of the 18S rRNA gene. In this first investigation, we establish the baseline information needed for further and more comprehensive analyses on the time series: minimum coverage depth per sample, taxonomic and phylogenetic diversity of the community and effect of the Diel Vertical Migration in the epipelagic community. We also analyze the limitations of the species identification in relation to the variability of the V9 region within and between species.

  13. River discharge as a major driving force on spatial and temporal variations in zooplankton biomass and community structure in the Godavari estuary India.

    PubMed

    Venkataramana, V; Sarma, V V S S; Matta Reddy, Alavala

    2017-08-28

    Variability in horizontal zooplankton biomass distribution was investigated over 13 months in the Godavari estuary, along with physical (river discharge, temperature, salinity), chemical (nutrients, particulate organic matter), biological (phytoplankton biomass), and geological (suspended matter) properties to examine the influencing factors on their spatial and temporal variabilities. The entire estuary was filled with freshwater during peak discharge period and salinity near zero, increased to ~ 34 psu during dry period with relatively high nutrient levels during former than the latter period. Due to low flushing time (< 1 day) and high suspended load (> 500 mg L -1 ) during peak discharge period, picoplankton (cyanophyceae) contributed significantly to the phytoplankton biomass (Chl-a) whereas microplankton and nanoplankton (bacillariophyceae, and chlorophyceae) during moderate and mostly microplankton during dry period. Zooplankton biomass was the lowest during peak discharge period and increased during moderate followed by dry period. The zooplankton abundance was controlled by dead organic matter during peak discharge period, while both phytoplankton biomass and dead organic matter during moderate discharge and mostly phytoplankton biomass during dry period. This study suggests that significant modification of physico-chemical properties by river discharge led to changes in phytoplankton composition and dead organic matter concentrations that alters biomass, abundance, and composition of zooplankton in the Godavari estuary.

  14. Ocean acidification alters zooplankton communities and increases top-down pressure of a cubozoan predator.

    PubMed

    Hammill, Edd; Johnson, Ellery; Atwood, Trisha B; Harianto, Januar; Hinchliffe, Charles; Calosi, Piero; Byrne, Maria

    2018-01-01

    The composition of local ecological communities is determined by the members of the regional community that are able to survive the abiotic and biotic conditions of a local ecosystem. Anthropogenic activities since the industrial revolution have increased atmospheric CO 2 concentrations, which have in turn decreased ocean pH and altered carbonate ion concentrations: so called ocean acidification (OA). Single-species experiments have shown how OA can dramatically affect zooplankton development, physiology and skeletal mineralization status, potentially reducing their defensive function and altering their predatory and antipredatory behaviors. This means that increased OA may indirectly alter the biotic conditions by modifying trophic interactions. We investigated how OA affects the impact of a cubozoan predator on their zooplankton prey, predominantly Copepoda, Pleocyemata, Dendrobranchiata, and Amphipoda. Experimental conditions were set at either current (pCO 2 370 μatm) or end-of-the-century OA (pCO 2 1,100 μatm) scenarios, crossed in an orthogonal experimental design with the presence/absence of the cubozoan predator Carybdea rastoni. The combined effects of exposure to OA and predation by C. rastoni caused greater shifts in community structure, and greater reductions in the abundance of key taxa than would be predicted from combining the effect of each stressor in isolation. Specifically, we show that in the combined presence of OA and a cubozoan predator, populations of the most abundant member of the zooplankton community (calanoid copepods) were reduced 27% more than it would be predicted based on the effects of these stressors in isolation, suggesting that OA increases the susceptibility of plankton to predation. Our results indicate that the ecological consequences of OA may be greater than predicted from single-species experiments, and highlight the need to understand future marine global change from a community perspective. © 2017 John Wiley & Sons

  15. Cyanobacteria dominance influences resource use efficiency and community turnover in phytoplankton and zooplankton communities.

    PubMed

    Filstrup, Christopher T; Hillebrand, Helmut; Heathcote, Adam J; Harpole, W Stanley; Downing, John A

    2014-04-01

    Freshwater biodiversity loss potentially disrupts ecosystem services related to water quality and may negatively impact ecosystem functioning and temporal community turnover. We analysed a data set containing phytoplankton and zooplankton community data from 131 lakes through 9 years in an agricultural region to test predictions that plankton communities with low biodiversity are less efficient in their use of limiting resources and display greater community turnover (measured as community dissimilarity). Phytoplankton resource use efficiency (RUE = biomass per unit resource) was negatively related to phytoplankton evenness (measured as Pielou's evenness), whereas zooplankton RUE was positively related to phytoplankton evenness. Phytoplankton and zooplankton RUE were high and low, respectively, when Cyanobacteria, especially Microcystis sp., dominated. Phytoplankton communities displayed slower community turnover rates when dominated by few genera. Our findings, which counter findings of many terrestrial studies, suggest that Cyanobacteria dominance may play important roles in ecosystem functioning and community turnover in nutrient-enriched lakes. © 2014 John Wiley & Sons Ltd/CNRS.

  16. Evaluation of the Zooplankton Community of Livingston Reservoir, Texas, as Related to Paddlefish Food Resources

    DTIC Science & Technology

    1993-12-01

    EVALUATION OF THE ZOOPLANKTON COMMUNITY OF LIVINGSTON RESERVOIR. TEXAS, AS RELATED TO PADDLEFISH FOOD RESOURCES A Thesis by CASEY KENNETH MOORE...OF LIVINGSTON RESERVOIR, TEXAS. AS RELATED TO PADDLEFISH FOOD RESOURCES A Thesis by CASEY KENNETH MOORE Submitted to Texas A&M University in partial...Fisheries Sciences iii ABSTRACT Evaluation of the Zooplankton Community of Livingston Reservoir, Texas, as Related to Paddlefish Food Resources

  17. Roles of predation, food, and temperature in structuring the epilimnetic zooplankton populations in Lake Ontario, 1981-1986

    Johannsson, Ora E.; O'Gorman, Robert

    1991-01-01

    We sampled phytoplankton, zooplankton, and alewives Alosa pseudoharengus and measured water temperature in Lake Ontario during 1981–1986. Through the use of general linear regression models we then sought evidence of control of the eplimnetic zooplankton community (mid-July to mid-October) by producers, consumers, and temperature. Our measures of the zooplankton community were total biomass, cladoceran biomass, and the ratio of large to small Daphnia spp. (D. galeata mendotae andD. retrocurva). Zooplankton population variables assessed were abundance, egg ratio, and productivity. Through factor analysis, factors were created from the standardized, transformed independent variables for use in the regression analyses. Regression models showed significant inverse relationships (P < 0.05) between alewives and Bosmina longirostris (abundance, production, and egg ratio), Ceriodaphnia lacustris (egg ratio), andDaphnia retrocurva (egg ratio). Bosmina longirostris and D. retrocurva egg ratios were inversely related to algae biomass (<20 μm), thus the smaller algae might be controlled in part by the zooplankton community. Production of C. lacustris was directly related to temperature, as was the production and abundance of Tropocyclops prasinus. The annual size-frequency distributions of B. longirostris and D. retrocurva were inversely related to yearling alewife abundance and directly related to adult alewife abundance, which suggested that yearlings use a particulate-feeding mode on these zooplankton species more frequently than adults. We found no significant negative correlations among the zooplankton species, which suggested that interzooplankton predation and competition were not as important in structuring the community as were planktivory and temperature.

  18. Examining shifts in zooplankton community as a response of environmental change in Lakes

    NASA Astrophysics Data System (ADS)

    Ghadouani, Anas; Mines, Conor; Legendre, Pierre; Yan, Norman

    2014-05-01

    We examined 20 years of zooplankton samples from Harp Lake for shifts in zooplankton variability following invasion by zooplankton predator Bythotrephes longimanus, using organism body size—as measured at high resolution by Laser Optical Plankton Counter (LOPC)—as the primary metric of investigation. A period of transitory high variability in the 2yr post-invasion was observed for both body size compositional variability and aggregate variability metrics, with both measures of variability shifting from low or intermediate to high variability immediately following invasion, before shifting again to intermediate variability, 2 yr post-invasion. Aggregate and compositional variability dynamics were also considered in combination over the study period, revealing that the period of transitory high variability coincided with a shift from a community-wide stasis variability pattern to one of asynchrony, before a shift back to stasis 2 yr post-invasion. These dynamics were related to changes in the significant zooplankton species within the Harp Lake community over the pre- and post- invasion periods, and are likely to be indicative of changes in the stability in the zooplankton community following invasion by Bythotrephes. The dual consideration of aggregate and compositional variability as measured by LOPC was found to provide a valuable means to assess the ecological effects of biological invasion on zooplankton communities as a whole, extending our knowledge of the effects of invasion beyond that already revealed through more traditional taxonomic investigation.

  19. Seasonal and interannual changes in zooplankton community in the coastal zone of the North-Eastern Black Sea.

    NASA Astrophysics Data System (ADS)

    Nikishina, A. B.; Arashkevich, E. G.; Louppova, N. E.; Soloviev, K. A.

    2009-04-01

    The phenological response of zooplankton community is a result of simultaneous effect of several factors: feeding conditions, predation abundance, periods of reproduction of common species and hydrodynamic regime. The Black sea ecosystem is one of the best studied in the world, otherwise there is still some illegibility about ecosystem functioning and especially about environmental factors influence on zooplankton dynamics. For the last twenty years pelagic system of the Black Sea has changed dramatically. The invasion of ctenophore Mnemiopsis leidyi in the middle of eighties caused significant decrease in zooplankton biomass. It also altered plankton structure and shifted periods of mass reproduction of the abundant species and biomass maximums. For instance, before the invasion of Mnemiopsis the maximum of zooplankton biomass was observed in autumn (data by A. Pasternak, 1983), and after that the maximum moved to the spring (data by V.S. Khoroshilov, 1999). The incursion of ctenophore Beroe ovata feeding on Mnemiopsis in the nineties has led to the enhancement of zooplankton community. Although the detailed analysis of seasonal zooplankton dynamics wasn't performed in the recent years. The object of our research was to study seasonal and interannual changes in zooplankton community in the coastal area of the North-Eastern Black Sea. Analysis of interannual, seasonal and spatial changes in zooplankton distribution, abundance and species composition along with age structure of dominant populations were performed based on investigations during 2005-2008 years in the North-Eastern Black Sea. Plankton samples were obtained monthly since June 2005 till December 2008. Plankton was collected at three stations at depths 25m, 50m and 500-1000m along the transect from the Blue Bay to the open sea. Sampling of gelatinous animals was conducted in parallel to the zooplankton sampling. Simultaneously with plankton sampling CTD data were obtained. The feeding conditions were

  20. Impact of climate change on zooplankton communities, seabird populations and arctic terrestrial ecosystem—A scenario

    NASA Astrophysics Data System (ADS)

    Stempniewicz, Lech; Błachowiak-Samołyk, Katarzyna; Węsławski, Jan M.

    2007-11-01

    Many arctic terrestrial ecosystems suffer from a permanent deficiency of nutrients. Marine birds that forage at sea and breed on land can transport organic matter from the sea to land, and thus help to initiate and sustain terrestrial ecosystems. This organic matter initiates the emergence of local tundra communities, increasing primary and secondary production and species diversity. Climate change will influence ocean circulation and the hydrologic regime, which will consequently lead to a restructuring of zooplankton communities between cold arctic waters, with a dominance of large zooplankton species, and Atlantic waters in which small species predominate. The dominance of large zooplankton favours plankton-eating seabirds, such as the little auk ( Alle alle), while the presence of small zooplankton redirects the food chain to plankton-eating fish, up through to fish-eating birds (e.g., guillemots Uria sp.). Thus, in regions where the two water masses compete for dominance, such as in the Barents Sea, plankton-eating birds should dominate the avifauna in cold periods and recess in warmer periods, when fish-eaters should prevail. Therefore under future anthropogenic climate scenarios, there could be serious consequences for the structure and functioning of the terrestrial part of arctic ecosystems, due in part to changes in the arctic marine avifauna. Large colonies of plankton-eating little auks are located on mild mountain slopes, usually a few kilometres from the shore, whereas colonies of fish-eating guillemots are situated on rocky cliffs at the coast. The impact of guillemots on the terrestrial ecosystems is therefore much smaller than for little auks because of the rapid washing-out to sea of the guano deposited on the seabird cliffs. These characteristics of seabird nesting sites dramatically limit the range of occurrence of ornithogenic soils, and the accompanying flora and fauna, to locations where talus-breeding species occur. As a result of climate

  1. Lake Ontario zooplankton in 2003 and 2008: Community changes and vertical redistribution

    Rudstam, Lars G.; Holeck, Kristen T.; Bowen, Kelly L.; Watkins, James M.; Weidel, Brian C.; Luckey, Frederick J.

    2014-01-01

    Lake-wide zooplankton surveys are critical for documenting and understanding food web responses to ecosystem change. Surveys in 2003 and 2008 during the binational intensive field year in Lake Ontario found that offshore epilimnetic crustacean zooplankton declined by a factor of 12 (density) and factor of 5 (biomass) in the summer with smaller declines in the fall. These declines coincided with an increase in abundance of Bythotrephes and are likely the result of direct predation by, or behavioral responses to this invasive invertebrate predator. Whole water column zooplankton density also declined from 2003 to 2008 in the summer and fall (factor of 4), but biomass only declined in the fall (factor of 2). The decline in biomass was less than the decline in density because the average size of individual zooplankton increased. This was due to changes in the zooplankton community composition from a cyclopoid/bosminid dominated community in 2003 to a calanoid dominated community in 2008. The increase in calanoid copepods was primarily due to the larger species Limnocalanus macrurus and Leptodiaptomus sicilis. These cold water species were found in and below the thermocline associated with a deep chlorophyll layer. In 2008, most of the zooplankton biomass resided in or below the thermocline during the day. Increased importance of copepods in deeper, colder water may favor Cisco and Rainbow Smelt over Alewife because these species are better adapted to cold temperatures than Alewife.

  2. Latitudinal distribution of zooplankton communities in the Western Pacific along 160°E during summer 2014

    NASA Astrophysics Data System (ADS)

    Sun, Dong; Wang, Chunsheng

    2017-05-01

    A total of 51 mesozooplankton samples collected with a WP2 net from 0 to 200 m depth along 160°E (4°S-46°N) in the Western Pacific from June to July 2014 were analyzed. The latitudinal distribution of mesozooplankton community structure was analyzed. The average biomass and abundance in different provinces generally increased with latitude: the biomass of zooplankton ranged from 1.18 mg DW m- 3 (11°N) to 97.81 mg DW m- 3 (45°N), and the abundance of zooplankton ranged from 45.11 ind. m- 3 (3°S) to 439.84 ind. m- 3 (41°N). The community structure of zooplankton also showed a significant latitudinal variation. At lower latitudes, calanoid copepods were the most abundant group, while cyclopoid copepods were the most abundant group at higher latitudes. Multidimensional scaling analysis of community structure and other physical/chemical/biological characteristics supported five ecological provinces in the northwestern Pacific: the Western Pacific Warm Pool Province (WARM), the North Pacific Tropical Gyre (NPTG), the North Pacific Subtropical Gyre (NPST), the Kuroshio Current Province (KURO) and the Pacific Subarctic Gyres Province (PSAG). The Kuroshio Current Province can be regarded as a transitional zone between the subarctic and northern subtropical area, and this transitional zone corresponds much more closely to the ecocline concept, rather than the ecotone concept.

  3. SPATIAL PATTERNS IN ASSEMBLAGE STRUCTURES OF PELAGIC FORAGE FISH AND ZOOPLANKTON IN WESTERN LAKE SUPERIOR

    EPA Science Inventory

    This manuscript reports on the spatial distribution of zooplankton and forage fish in western Lake Superior. Fish and zooplankton assemblages are shown to differ substantially in abundance and size structure both between the open lake and nearshore regions and between two differe...

  4. Variations in the structural and functional diversity of zooplankton over vertical and horizontal environmental gradients en route to the Arctic Ocean through the Fram Strait.

    PubMed

    Gluchowska, Marta; Trudnowska, Emilia; Goszczko, Ilona; Kubiszyn, Anna Maria; Blachowiak-Samolyk, Katarzyna; Walczowski, Waldemar; Kwasniewski, Slawomir

    2017-01-01

    A multi-scale approach was used to evaluate which spatial gradient of environmental variability is the most important in structuring zooplankton diversity in the West Spitsbergen Current (WSC). The WSC is the main conveyor of warm and biologically rich Atlantic water to the Arctic Ocean through the Fram Strait. The data set included 85 stratified vertical zooplankton samples (obtained from depths up to 1000 metres) covering two latitudinal sections (76°30'N and 79°N) located across the multi-path WSC system. The results indicate that the most important environmental variables shaping the zooplankton structural and functional diversity and standing stock variability are those associated with depth, whereas variables acting in the horizontal dimension are of lesser importance. Multivariate analysis of the zooplankton assemblages, together with different univariate descriptors of zooplankton diversity, clearly illustrated the segregation of zooplankton taxa in the vertical plane. The epipelagic zone (upper 200 m) hosted plentiful, Oithona similis-dominated assemblages with a high proportion of filter-feeding zooplankton. Although total zooplankton abundance declined in the mesopelagic zone (200-1000 m), zooplankton assemblages in that zone were more diverse and more evenly distributed, with high contributions from both herbivorous and carnivorous taxa. The vertical distribution of integrated biomass (mg DW m-2) indicated that the total zooplankton biomass in the epipelagic and mesopelagic zones was comparable. Environmental gradients acting in the horizontal plane, such as the ones associated with different ice cover and timing of the spring bloom, were reflected in the latitudinal variability in protist community structure and probably caused differences in succession in the zooplankton community. High abundances of Calanus finmarchicus in the WSC core branch suggest the existence of mechanisms advantageous for higher productivity or/and responsible for physical

  5. Metagenetic Sequencing of Zooplankton Communities in the High-Diversity Central North Pacific

    NASA Astrophysics Data System (ADS)

    Matthews, S. A.; van Woudenberg, L.; Iacchei, M.; Lenz, P. H.; Goetze, E.

    2016-02-01

    Marine zooplankton are important intermediate trophic level consumers in the ocean, and the subtropical North Pacific holds global maxima in species diversity for these communities. Zooplankton assemblages in this region include several species complexes, with many understudied and morphologically cryptic species. We used metagenetic sequencing to characterize zooplankton community composition across depth (0-1500m) at an open ocean time series site in the central North Pacific (Station ALOHA), using depth-stratified 1m2 MOCNESS samples that were size fractionated into 5 size classes (0.2-0.5 mm, 0.5-1 mm, 1-2 mm, 2-5 mm, >5 mm). Our goals were to quantify the fraction of the community that is currently undescribed, identify taxonomic groups that contain large numbers of undescribed species and may be important to biogeochemical cycling in the ocean, and establish a metagenetic method that can be used to effectively characterize the species richness of epipelagic and mesopelagic communities in this region. Amplicons from several DNA loci, including mitochondrial cytochrome c oxidase subunit I and 12S rRNA, and nuclear 18S and 28S rRNA genes were sequenced on the MiSeq Illumina platform to characterize community composition. We evaluate species composition across metagenetic marker regions, pelagic depth zones, day and night-time MOCNESS tows, and compare our findings with prior species lists from the region. Our results are an important contribution to establishing standardized metagenetic methods for marine zooplankton communities.

  6. Size and species diversity of zooplankton communities in fluctuating Mediterranean salt marshes

    NASA Astrophysics Data System (ADS)

    Brucet, Sandra; Boix, Dani; López-Flores, Rocío; Badosa, Anna; Quintana, Xavier D.

    2006-04-01

    Differences in size and species diversity were analysed in a zooplankton community of a Mediterranean salt marsh (Empordà wetlands, NE Iberian Peninsula), where the dominance of a single species was frequent. In the permanent salt marsh, species diversity and size diversity had similar patterns along zooplankton succession. In the temporary salt marsh species diversity was high after flooding and diminished once water inputs ceased. As species diversity declined size diversity increased. Eventually, one species of calanoid dominated the zooplankton community. The high size diversity in situations of calanoid dominance was possibly due to the co-occurrence of different developmental stages, each of which have different diets. Size diversity would thus indicate trophic niche segregation among different sizes. The combined use of species and size diversity values allows the identification of the successional phases.

  7. Zooplankton communities and Bythotrephes longimanus in lakes of the montane region of the northern Alps

    PubMed Central

    Horváth, Zsófia; Vad, Csaba F.; Preiler, Christian; Birtel, Julia; Matthews, Blake; Ptáčníková, Radka; Ptáčník, Robert

    2017-01-01

    Abstract Lakes in the Alps represent a considerable fraction of nutrient-poor lakes in Central Europe, with unique biodiversity and ecosystem properties. Although some individual lakes are well studied, less knowledge is available on large-scale patterns essential to general understanding of their functioning. Here, we aimed to describe crustacean zooplankton communities (Cladocera, Copepoda) and identify their environmental drivers in the pelagic zone of 54 oligotrophic lakes in the montane region of the Alps (400–1200 m) in Austria, Germany, and Switzerland, covering a spatial scale of 650 km. Moreover, we aimed to provide data on the distribution and ecological requirements of the North American invader Bythotrephes longimanus in its Central European native range. Communities were mainly dominated by widespread species typical of lowland habitats, and only a few true specialists of oligotrophic alpine lakes were present. The most frequent taxa were the Daphnia longispina complex and Eudiaptomus gracilis, with 48 and 45 occurrences, respectively. Species richness decreased with altitude and increased with lake area. The main structuring factors of community composition were chlorophyll a concentration and depth, which drove an apparent separation of mesotrophic and oligotrophic communities. Bythotrephes had 13 occurrences, showing a preference for deep oligotrophic lakes. Its presence was not coupled with lower crustacean species richness, as was repeatedly observed in North America. Additionally, it frequently co-occurred with the other large predatory cladoceran, Leptodora kindtii. B. longimanus might be considered a truly montane species in Central Europe, given its absence in lowland and alpine lakes. PMID:28824797

  8. A Functional Approach to Zooplankton Communities in Mountain Lakes Stocked With Non-Native Sportfish Under a Changing Climate

    NASA Astrophysics Data System (ADS)

    Redmond, Laura E.; Loewen, Charlie J. G.; Vinebrooke, Rolf D.

    2018-03-01

    Cumulative impacts of multiple stressors on freshwater biodiversity and ecosystem function likely increase with elevation, thereby possibly placing alpine communities at greatest risk. Here, consideration of species traits enables stressor effects on taxonomic composition to be translated into potential functional impacts. We analyzed data for 47 taxa across 137 mountain lakes and ponds spanning large latitudinal (491 km) and elevational (1,399 m) gradients in western Canada, to assess regional and local factors of the taxonomic composition and functional structure of zooplankton communities. Multivariate community analyses revealed that small body size, clonal reproduction via parthenogenesis, and lack of pigmentation were species traits associated with both introduced non-native sportfish and also environmental conditions reflecting a warmer and drier climate—namely higher water temperatures, shallower water depths, and more chemically concentrated water. Thus, historical introductions of sportfish appear to have potentially induced greater tolerance in zooplankton communities of future climatic warming, especially in previously fishless alpine lakes. Although alpine lake communities occupied a relatively small functional space (i.e., low functional diversity), they were contained within the broader regional functional structure. Therefore, our findings point to the importance of dispersal by lower montane species to the future functional stability of alpine communities.

  9. Zooplankton community response to the winter 2013 deep convection process in the NW Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Donoso, Katty; Carlotti, François; Pagano, Marc; Hunt, Brian P. V.; Escribano, Rubén.; Berline, Léo.

    2017-03-01

    The Gulf of Lion is an important area of deep convection, where intense winter vertical mixing brings nutrients up from deeper layers, promoting the largest bloom in the Mediterranean at the end of winter/early spring. The DEWEX program conducted cruises in February and April 2013 to investigate the ecosystem level impacts of deep water convection. Zooplankton data were collected through net sampling and imaging with an Underwater Vision Profiler. In winter, low zooplankton abundance and biomass were observed in the Deep Convection Zone (DCZ) and higher values on its periphery. In spring, this pattern reversed with high biomass in the DCZ and lower values on the periphery. On average for the whole area, the potential grazing impact was estimated to increase by one order of magnitude from winter to spring. In April, all areas except the DCZ incurred top-down control by zooplankton on the phytoplankton stock. In the DCZ, the chlorophyll-a values remained high despite the high zooplankton biomass and carbon demand, indicating a sustained bottom-up control. The zooplankton community composition was comparable for both periods, typified by high copepod dominance, but with some differences between the DCZ and peripheral regions. In spring the DCZ was characterized by a strong increase in herbivorous species such as Centropages typicus and Calanus helgolandicus, and an increase in the number of large zooplankton individuals. Our study indicates that the DCZ is likely an area of both enhanced energy transfer to higher trophic levels and organic matter export in the North Western Mediterranean Sea.

  10. Identifying zooplankton community changes between shallow and upper-mesophotic reefs on the Mesoamerican Barrier Reef, Caribbean.

    PubMed

    Andradi-Brown, Dominic A; Head, Catherine E I; Exton, Dan A; Hunt, Christina L; Hendrix, Alicia; Gress, Erika; Rogers, Alex D

    2017-01-01

    Mesophotic coral ecosystems (MCEs, reefs 30-150 m) are understudied, yet the limited research conducted has been biased towards large sessile taxa, such as scleractinian corals and sponges, or mobile taxa such as fishes. Here we investigate zooplankton communities on shallow reefs and MCEs around Utila on the southern Mesoamerican Barrier Reef using planktonic light traps. Zooplankton samples were sorted into broad taxonomic groups. Our results indicate similar taxonomic zooplankton richness and overall biomass between shallow reefs and MCEs. However, the abundance of larger bodied (>2 mm) zooplanktonic groups, including decapod crab zoea, mysid shrimps and peracarid crustaceans, was higher on MCEs than shallow reefs. Our findings highlight the importance of considering zooplankton when identifying broader reef community shifts across the shallow reef to MCE depth gradient.

  11. Changes in zooplankton community, and seston and zooplankton fatty acid profiles at the freshwater/saltwater interface of the Chowan River, North Carolina

    PubMed Central

    Rinchard, Jacques; Kimmel, David G.

    2017-01-01

    The variability in zooplankton fatty acid composition may be an indicator of larval fish habitat quality as fatty acids are linked to fish larval growth and survival. We sampled an anadromous fish nursery, the Chowan River, during spring of 2013 in order to determine how the seston fatty acid composition varied in comparison with the zooplankton community composition and fatty acid composition during the period of anadromous larval fish residency. The seston fatty acid profiles showed no distinct pattern in relation to sampling time or location. The mesozooplankton community composition varied spatially and the fatty acid profiles were typical of freshwater species in April. The Chowan River experienced a saltwater intrusion event during May, which resulted in brackish water species dominating the zooplankton community and the fatty acid profile showed an increase in polyunsaturated fatty acids (PUFA), in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The saltwater intrusion event was followed by an influx of freshwater due to high precipitation levels in June. The zooplankton community composition once again became dominated by freshwater species and the fatty acid profiles shifted to reflect this change; however, EPA levels remained high, particularly in the lower river. We found correlations between the seston, microzooplankton and mesozooplankton fatty acid compositions. Salinity was the main factor correlated to the observed pattern in species composition, and fatty acid changes in the mesozooplankton. These data suggest that anadromous fish nursery habitat likely experiences considerable spatial variability in fatty acid profiles of zooplankton prey and that are correlated to seston community composition and hydrodynamic changes. Our results also suggest that sufficient prey density as well as a diverse fatty acid composition is present in the Chowan River to support larval fish production. PMID:28828262

  12. Zooplankton community resilience and aquatic environmental stability on aquaculture practices: a study using net cages.

    PubMed

    Dias, J D; Simões, N R; Bonecker, C C

    2012-02-01

    Fish farming in net cages causes changes in environmental conditions. We evaluated the resilience of zooplankton concerning this activity in Rosana Reservoir (Paranapanema River, PR-SP). Samples were taken near the net cages installed at distances upstream and downstream, before and after net cage installation. The resilience was estimated by the decrease in the groups' abundance after installing the net cages. The zooplankton community was represented by 106 species. The most abundant species were Synchaeta pectinata, S. oblonga, Conochilus coenobasis, Polyarthra dolichoptera and C. unicornis (Rotifera), Ceriodaphnia cornuta, Moina minuta, Bosmina hagmanni and C. silvestrii (Cladocera) and Notodiaptomus amazonicus (Copepoda). The resilience of microcrustaceans was affected in the growing points as this activity left the production environment for longer, delaying the natural ability of community responses. Microcrustaceans groups, mainly calanoid and cyclopoid copepods, had a different return rate. The net cage installation acted as a stress factor on the zooplankton community. Management strategies that cause fewer risks to the organisms and maximize energy flow may help in maintaining system stability.

  13. Zooplankton communities and Bythotrephes longimanus in lakes of the montane region of the northern Alps

    PubMed Central

    Horváth, Zsófia; Vad, Csaba F.; Preiler, Christian; Birtel, Julia; Matthews, Blake; Ptáčníková, Radka; Ptacnik, Robert

    2017-01-01

    Lakes in the Alps represent a considerable fraction of nutrient-poor lakes in Central Europe, with unique biodiversity and ecosystem properties. Although some individual lakes are well-studied, less knowledge is available on large-scale patterns essential to generalise the understanding of their functioning. Here, we aimed to describe crustacean zooplankton communities (Cladocera, Copepoda) and identify their environmental drivers in the pelagic zone of 54 oligotrophic lakes in the montane region of the Alps (400–1200 m) in Austria, Germany, and Switzerland, covering a spatial scale of 650 km. Moreover, we aimed to provide data on the distribution and ecological requirements of the North American invader Bytotrephes longimanus in its Central European native range. Communities were mainly dominated by widespread species typical of lowland habitats, and only a few true specialists of oligotrophic alpine lakes were present. The most frequent taxa were the Daphnia longispina complex and Eudiaptomus gracilis, with 48 and 45 occurrences, respectively. Species richness decreased with altitude and increased with lake area. The main structuring factors of community composition were chlorophyll a concentration and depth, which drove an apparent separation of mesotrophic and oligotrophic communities. Bytotrephes had 13 occurrences, showing a preference for deep oligotrophic lakes. Its presence was not coupled with lower crustacean species richness as it was repeatedly observed in North America. Additionally, it frequently co-occurred with the other large predatory cladoceran, Leptodora kindtii. B. longimanus might be considered a truly montane species in Central Europe, given its absence in lowland and alpine lakes. PMID:28649318

  14. Seasonal variation in the biochemical compositions of phytoplankton and zooplankton communities in the southwestern East/Japan Sea

    NASA Astrophysics Data System (ADS)

    Jo, Naeun; Kang, Jae Joong; Park, Won Gyu; Lee, Bo Ram; Yun, Mi Sun; Lee, Jang Han; Kim, Su Min; Lee, Dasom; Joo, HuiTae; Lee, Jae Hyung; Ahn, So Hyun; Lee, Sang Heon

    2017-09-01

    The macromolecular composition of phytoplankton communities and the proximate composition of zooplankton communities were measured monthly in the southwestern East/Japan Sea from April to November 2014 in order to identify seasonal changes in, and relationships among, the biochemical compositions in both phytoplankton and zooplankton. The carbohydrate content of phytoplankton was highest in June, whereas the protein content was highest in August and lipids were highest in April. Overall, carbohydrates were dominant (53.2 ± 12.5%) in the macromolecular composition of phytoplankton during the study period. This composition is believed to result from the dominance of diatoms and/or nutrient-depleted conditions. In comparison, the protein level of zooplankton was highest in November, whereas lipids were slightly higher in May than other months. Overall, proteins were the dominant organic compounds (47.9±8.6% DW) in zooplankton communities, whereas lipids were minor components (5.5±0.6% DW). The high protein content of zooplankton might be related to the abundance of copepods, whereas the low lipid content might be due to a relatively high primary production that could provide a sufficient food supply for zooplankton so that they do not require high lipid storage. A significant positive correlation (r=0.971, n=7, p<0.01) was found between the lipid compositions of phytoplankton and zooplankton during our study period with a time lag, which is consistent with the findings from previous studies. More detailed studies on the biochemical composition of phytoplankton and zooplankton are needed to better understand the East/Japan Sea ecosystem's response to the many environmental changes associated with global warming.

  15. Effects of a new molt-inducing insecticide, tebufenozide, on zooplankton communities in lake enclosures.

    PubMed

    Kreutzweiser, D P; Thomas, D R

    1995-10-01

    : A potent ecdysone agonist, tebufenozide, has recently been developed as a molt-inducing insecticide to control defoliating lepidopterans. As part of continuing research efforts to assess the effectiveness and environmental safety of this material for insect pest management in Canadian forests, tebufenozide (RH-5992-2F) was applied to large lake enclosures and the effects on zooplankton communities were evaluated. There were significant treatment effects at all test concentrations (0.07-0.66 mg L(-1) tebufenozide). Concentration-dependent reductions in the abundance of cladocerans indicated that there were direct toxic effects of tebufenozide on this group of macrozooplankton. There were no indications of direct toxic effects on copepods. Significant increases in abundance of rotifers in treated enclosures at the three higher test concentrations were coincident with reductions in cladocerans and indicated secondary effects of the insecticide on the abundance of microzooplankton. There were no significant differences among treated and control enclosures in chlorophyll a concentrations, indicating that tebufenozide did not have direct effects on phytoplankton biomass, nor did the alterations in the zooplankton communities of treated enclosures have measurable secondary effects on phytoplankton biomass. Daytime dissolved oxygen concentrations were significantly higher in treated enclosures than in controls, indicating that the perturbation to biotic communities of some treated enclosures was sufficient to induce measurable changes in system-level functional attributes. Recovery of zooplankton communities in the enclosures occurred within 1-2 months at 0.07 and 0.13 mg l(-1) and by the following summer (12-13 months) at 0.33 and 0.66 mg l(-1).

  16. Spatial patterns in assemblage structures of pelagic forage fish and zooplankton in western Lake Superior

    Johnson, Timothy B.; Hoff, Michael H.; Trebitz, Anett S.; Bronte, Charles R.; Corry, Timothy D.; Kitchell, James F.; Lozano, Stephen J.; Mason, Doran M.; Scharold, Jill V.; Schram, Stephen T.; Schreiner, Donald R.

    2004-01-01

    We assessed abundance, size, and species composition of forage fish and zooplankton communities of western Lake Superior during August 1996 and July 1997. Data were analyzed for three ecoregions (Duluth-Superior, Apostle Islands, and the open lake) differing in bathymetry and limnological and biological patterns. Zooplankton abundance was three times higher in the Duluth-Superior and Apostle Islands regions than in the open lake due to the large numbers of rotifers. Copepods were far more abundant than Cladocera in all ecoregions. Mean zooplankton size was larger in the open lake due to dominance by large calanoid copepods although size of individual taxa was similar among ecoregions. Forage fish abundance and biomass was highest in the Apostle Islands region and lowest in the open lake ecoregion. Lake herring (Coregonus artedi), rainbow smelt (Osmerus mordax) and deepwater ciscoes (Coregonus spp.) comprised over 90% of the abundance and biomass of fishes caught in midwater trawls and recorded with hydroacoustics. Growth and condition of fish was good, suggesting they were not resource limited. Fish and zooplankton assemblages differed among the three ecoregions of western Lake Superior, due to a combination of physical and limnological factors related to bathymetry and landscape position.

  17. Ecology of selected marine communities in Glacier Bay: Zooplankton, forage fish, seabirds and marine mammals

    Robards, Martin D.; Drew, Gary S.; Piatt, John F.; Anson, Jennifer Marie; Abookire, Alisa A.; Bodkin, James L.; Hooge, Philip N.; Speckman, Suzann G.

    2003-01-01

    We studied oceanography (including primary production), secondary production, small schooling fish (SSF), and marine bird and mammal predators in Glacier Bay during 1999 and 2000. Results from these field efforts were combined with a review of current literature relating to the Glacier Bay environment. Since the conceptual model developed by Hale and Wright (1979) ‘changes and cycles’ continue to be the underlying theme of the Glacier Bay ecosystem. We found marked seasonality in many of the parameters that we investigated over the two years of research, and here we provide a comprehensive description of the distribution and relative abundance of a wide array of marine biota. Glacier Bay is a tidally mixed estuary that leads into basins, which stratify in summer, with the upper arms behaving as traditional estuaries. The Bay is characterized by renewal and mixing events throughout the year, and markedly higher primary production than in many neighboring southeast Alaska fjords (Hooge and Hooge, 2002). Zooplankton diversity and abundance within the upper 50 meters of the water column in Glacier Bay is similar to communities seen throughout the Gulf of Alaska. Zooplankton in the lower regions of Glacier Bay peak in abundance in late May or early June, as observed at Auke Bay and in the Gulf of Alaska. The key distinction between the lower Bay and other estuaries in the Gulf of Alaska is that a second smaller peak in densities occurs in August. The upper Bay behaved uniformly in temporal trends, peaking in July. Densities had begun to decline in August, but were still more than twice those observed in that region in May. The highest density of zooplankton observed was 17,870 organisms/m3 in Tarr Inlet during July. Trends in zooplankton community abundance and diversity within the lower Bay were distinct from upper-Glacier Bay trends. Whereas the lower Bay is strongly influenced by Gulf of Alaska processes, local processes are the strongest influence in the upper

  18. SPATIAL AND TEMPORAL VARIABILITY IN ZOOPLANKTON COMMUNITY DYNAMICS IN THREE URBANIZED BAYOUS OF THE PENSACOLA BAY SYSTEM, FLORIDA, USA

    EPA Science Inventory

    Spatial and temporal patterns in zooplankton community composition and abundance in near-coastal areas of the Gulf of Mexico are not well understood. This survey provides information on spatial and temporal differences in zoolplankton community composition and abundance for a coa...

  19. Determine Age-structure of Gelatinous Zooplankton Using Optical Coherence Tomography

    NASA Astrophysics Data System (ADS)

    Bi, H.; Shahrestani, S.; He, Y.

    2016-02-01

    Gelatinous are delicate and transparent by nature, but are conspicuous in many ecosystems when in bloom. Their proliferations are a bothersome and costly nuisance and influencing important food webs and species interactions. More importantly, gelatinous zooplankton respond to climate change rapidly and understanding their upsurge needs information on their recruitment and population dynamics which in turn require their age-structure. However, ageing gelatinous zooplankton is often restricted by the fact that they shrink under unfavorable conditions. In the present study, we examine the potential of using optical coherence tomography (OCT) to age gelatinous zooplankton. OCT is a non-invasive imaging technique that uses light waves to examine 2D or 3D structure of target objects at a resolution of 3-5 µm. We were able to successfully capture both 3D and 2D images of sea nettle muscle fibers. Preliminary results on ctenophores will be discussed. Overall, this non-destructive sampling allows us to scan and capture images of mesoglea from jellyfish cultured in the lab, using the same individual repeatedly through time, documenting its growth which will provide precise measurements to construct an age key that will be applied to gelatinous zooplankton captured in the field. Coupled with information on abundance, we can start to quantify their recruitment timing and success rate.

  20. Effects of hydrology on zooplankton communities in high-mountain ponds, Mount Rainier National Park, USA

    Girdner, Scott; Larson, Gary L.

    1995-01-01

    Ten high-mountain ponds in Mount Rainier National Park, Washington State, were studied from ice-out in June through September1992 to investigate the influences of fluctuating pond volumes on zooplankton communities. All of the ponds were at maximum volume immediately after ice-out. The temporary pond with the shortest wet phase was inhabited by rotifer taxa with short generation times and a crustacean taxon with the ability to encyst as drought-resistant resting bodies at immature stages of development. Dominant zooplankton taxa in three other temporary ponds and six permanent ponds were similar. Rotifer densities typically were lower in temporary ponds relative to those in permanent ponds, although Brachionus urceolaris was abundant shortly before the temporary ponds dried. Large volume loss was associated with large declines in total abundances of crustacean populations. Daphnia rosea was not present in temporary ponds following fall recharge. In deep-permanent ponds, copepods had slower developmental rates, smaller temporal changes in total abundances of crustacean populations and two additional large-bodied crustacean taxa were present relative to the characteristics of crustacean communities in shallow-permanent ponds. Owing to their small sizes and sensitivity to environmental change, collectively ponds such as these may provide an early signal of long-term climate change in aquatic systems.

  1. Effects of repeated exposure to 4-nonylphenol on the zooplankton community in littoral enclosures

    SciT

    O`Halloran, S.L.; Liber, K.; Gangl, J.A.

    1999-03-01

    The effects of 4-nonylphenol (NP) on freshwater zooplankton were evaluated in 18 littoral enclosure mesocosms in northeastern Minnesota. The 18 enclosures were allocated to three blocks of six units with each block including two untreated control enclosures and one enclosure for each of four NP treatments. Treated enclosures received 11 applications of NP over a 20-d period between July 8 and 28, 1993. Maximum NP concentrations measured in the water column 2 h after each application averaged ({+-} SD) 5 {+-} 4, 23 {+-} 11, 76 {+-} 21, and 243 {+-} 41 {micro}g/L over the 11 applications. Nonylphenol dissipated rapidlymore » from the water column but was more persistent in sediments and in/on macrophytes. All cladoceran and copepod taxa were significantly reduced in abundance at 243 {+-} 41 {micro}g/L; some sensitive taxa were also affected by 76 {+-} 21 and 23 {+-} 11 {micro}g/L. While many rotifer taxa were unaffected at any of the test concentrations, several were affected at {ge} 76 {+-} 21 {micro}g/L. Ostracods were only affected at 2,243 {+-} 41 {micro}g/L. No zooplankton taxon was affected at 5 {+-} 4 {micro}g/L. The period of maximum impact usually occurred within 1 to 7 d of the last NP application, and recovery to control abundance levels generally occurred within 7 to 28 d of the last NP application. Two sensitive taxa, Acroperus and Calanoida, did not recover at {ge} 76 {+-} 21 {micro}g/L by the end of the study. The maximum acceptable toxicant concentration for protection of all zooplankton taxa was estimated at {approximately} 10 {micro}g/L, although overall community diversity was unaffected at 23 {+-} 11. The water was the most probable route of NP exposure, but the greater persistence of NP residues in/on macrophytes may have contributed to the lack of recovery of some macrophyte-associated taxa.« less

  2. Zooplankton and the Ocean Carbon Cycle.

    PubMed

    Steinberg, Deborah K; Landry, Michael R

    2017-01-03

    Marine zooplankton comprise a phylogenetically and functionally diverse assemblage of protistan and metazoan consumers that occupy multiple trophic levels in pelagic food webs. Within this complex network, carbon flows via alternative zooplankton pathways drive temporal and spatial variability in production-grazing coupling, nutrient cycling, export, and transfer efficiency to higher trophic levels. We explore current knowledge of the processing of zooplankton food ingestion by absorption, egestion, respiration, excretion, and growth (production) processes. On a global scale, carbon fluxes are reasonably constrained by the grazing impact of microzooplankton and the respiratory requirements of mesozooplankton but are sensitive to uncertainties in trophic structure. The relative importance, combined magnitude, and efficiency of export mechanisms (mucous feeding webs, fecal pellets, molts, carcasses, and vertical migrations) likewise reflect regional variability in community structure. Climate change is expected to broadly alter carbon cycling by zooplankton and to have direct impacts on key species.

  3. From the epipelagic zone to the abyss: Trophic structure at two seamounts in the subtropical and tropical Eastern Atlantic - Part I zooplankton and micronekton

    NASA Astrophysics Data System (ADS)

    Denda, Anneke; Stefanowitsch, Benjamin; Christiansen, Bernd

    2017-12-01

    Specific mechanisms, driving trophic interactions within the pelagic community may be highly variable in different seamount systems. This study investigated the trophic structure of zooplankton and micronekton above and around Ampère and Senghor, two shallow seamounts in the subtropical and tropical Eastern Atlantic, and over the adjacent abyssal plains. For the identification of food sources and trophic positions stable isotope ratios (δ13C and δ15N) were used. δ13C ranged from -24.7‰ to -15.0‰ and δ15N covered a total range of 0.9-15.9‰. Based on epipelagic particulate organic matter, zooplankton and micronekton usually occupied the 1st-3rd trophic level, including herbivorous, omnivorous and carnivorous taxa. δ13C and δ15N values were generally lower in zooplankton and micronekton of the subtropical waters as compared to the tropical region, due to the differing nutrient availability and phytoplankton communities. Correlations between δ13C and δ15N values of particulate organic matter, zooplankton, micronekton and benthopelagic fishes suggest a linear food chain based on a single energy source from primary production for Ampère Seamount, but no evidence was found for an autochthonus seamount production as compared to the open ocean reference site. Between Senghor Seamount and the open ocean δ13C signatures indicate that hydrodynamic effects at seamounts may modify the energy supply at times, but evidence for a seamount effect on the trophic structure of the pelagic communities was weak, which supports the assumption that seamount communities rely to a large extent on advected food sources.

  4. An evaluation of the zooplankton community at the Sheboygan River Area of Concern and non-Area of Concern comparison sites in western Lake Michigan rivers and harbors in 2016

    Olds, Hayley T.; Scudder Eikenberry, Barbara C.; Burns, Daniel J.; Bell, Amanda H.

    2017-12-22

    The Great Lakes Areas of Concern (AOCs) are considered to be the most severely degraded areas within the Great Lakes basin, as defined in the Great Lakes Water Quality Agreement and amendments. Among the 43 designated AOCs are four Lake Michigan AOCs in the State of Wisconsin. The smallest of these AOCs is the Sheboygan River AOC, which was designated as an AOC because of sediment contamination from polychlorinated biphenyl compounds (PCBs), polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), and heavy metals. The Sheboygan River AOC has 9 of 14 possible Beneficial Use Impairments (BUIs), which must be addressed to improve overall water-quality, and to ultimately delist the AOC. One of the BUIs associated with this AOC is the “degradation of phytoplankton and zooplankton populations,” which can be removed from the list of impairments when it has been determined that zooplankton community composition and structure at the AOC do not differ significantly from communities at non-AOC comparison sites. In 2012 and 2014, the U.S. Geological Survey collected plankton (phytoplankton and zooplankton) community samples at the Sheboygan River AOC and selected non-AOC sites as part of a larger Great Lakes Restoration Initiative study evaluating both the benthos and plankton communities in all four of Wisconsin’s Lake Michigan AOCs. Although neither richness nor diversity of phytoplankton or zooplankton in the Sheboygan River AOC were found to differ significantly from the non-AOC sites in 2012, results from the 2014 data indicated that zooplankton diversity was significantly lower, and so rated as degraded, when compared to the Manitowoc and Kewaunee Rivers, two non-AOC sites of similar size, land use, and close geographic proximity.As a follow-up to the 2014 results, zooplankton samples were collected at the same locations in the AOC and non-AOC sites during three sampling trips in spring, summer, and fall 2016. An analysis of similarity indicated

  5. Effect of Main-stem Dams on Zooplankton Communities of the Missouri River (USA)

    EPA Science Inventory

    We examined the distribution and abundance of zooplankton from 146 sites on the Missouri River and found large shifts in the dominance of major taxa between management zones of this regulated river. Crustacean zooplankton were dominant in the inter-reservoir zone of the river, an...

  6. The ICES Working Group on Zooplankton Ecology: Accomplishments of the first 25 years

    NASA Astrophysics Data System (ADS)

    Wiebe, Peter H.; Harris, Roger; Gislason, Astthor; Margonski, Piotr; Skjoldal, Hein Rune; Benfield, Mark; Hay, Steve; O'Brien, Todd; Valdés, Luis

    2016-02-01

    The ICES Study Group on Zooplankton Ecology was created in 1991 to address issues of current and future concern within the field of zooplankton ecology. Within three years it became the ICES Working Group on Zooplankton Ecology (ICES WGZE) and this unique group in the world's oceanographic community has now been active for 25 years. This article reviews and synthesizes the products, and major accomplishments of the group. Achievements of the group, including the Zooplankton Methodology Manual, the Zooplankton Status Reports, and the International Zooplankton Symposia, have had an important impact on the wider field. Among the future issues that remain to be addressed by the group are the assessment of exploratory fisheries on zooplankton and micronekton species; further development of the zooplankton time-series; compilation and integration of allometric relationships for zooplankton species, and evaluation of new methodologies for the study of zooplankton distribution, abundance, physiology, and genetics. Marine science is an increasingly global undertaking and groups such as the ICES WGZE will continue to be essential to the advancement of understanding of zooplankton community structure and population dynamics in the world's oceans.

  7. Community composition, abundance and biomass of zooplankton in Zhangzi Island waters, Northern Yellow Sea

    NASA Astrophysics Data System (ADS)

    Yin, Jiehui; Zhang, Guangtao; Li, Chaolun; Wang, Shiwei; Zhao, Zengxia; Wan, Aiyong

    2017-09-01

    Samples were collected monthly from the sea area around Zhangzi Island, northern Yellow Sea, from July 2009 to June 2010. Vertical net towing was used to examine spatial and temporal variability in zooplankton abundance and biomass. Overall, Calanus sinicus and Saggita crassa were the dominant species found during the study period, while the amphipod Themisto gracilipes was dominant in winter and spring. Vast numbers of the ctenophore species of the genus Beroe were found in October and November. It was not possible to count them, but they constituted a large portion of the total zooplankton biomass. Zooplankton species diversity was highest in October, and species evenness was highest in April. Zooplankton abundance (non-jellyfish) and biomass were highest in June and lowest in August, with annual averages of 131.3 ind./m³ and 217.5 mg/m³, respectively. Water temperature may be responsible for the variations in zooplankton abundance and biomass. Beroe biomass was negatively correlated with other zooplankton abundance. Longterm investigations will be carried out to learn more about the influence of the environment on zooplankton assemblages.

  8. Habitat size modulates the influence of heterogeneity on species richness patterns in a model zooplankton community.

    PubMed

    Schuler, Matthew S; Chase, Jonathan M; Knight, Tiffany M

    2017-06-01

    Habitat heterogeneity is a primary mechanism influencing species richness. Despite the general expectation that increased heterogeneity should increase species richness, there is considerable variation in the observed relationship, including many studies that show negative effects of heterogeneity on species richness. One mechanism that can create such disparate results is the predicted trade-off between habitat area and heterogeneity, sometimes called the area-heterogeneity-trade-off (AHTO) hypothesis. The AHTO hypothesis predicts positive effects of heterogeneity on species richness in large habitats, but negative effects in small habitats. We examined the interplay between habitat size and habitat heterogeneity in experimental mesocosms that mimic freshwater ponds, and measured responses in a species-rich zooplankton community. We used the AHTO hypothesis and related mechanisms to make predictions about how heterogeneity would affect species richness and diversity in large compared to small habitats. We found that heterogeneity had a positive influence on species richness in large, but not small habitats, and that this likely resulted because habitat specialists were able to persist only when habitat size was sufficiently large, consistent with the predictions of the AHTO hypothesis. Our results emphasize the importance of considering context (e.g., habitat size in this case) when investigating the relative importance of ecological drivers of diversity, like heterogeneity. © 2017 by the Ecological Society of America.

  9. Zooplankton in the Arctic outflow

    NASA Astrophysics Data System (ADS)

    Soloviev, K. A.; Dritz, A. V.; Nikishina, A. B.

    2009-04-01

    Climate changes in the Arctic cause the changes in the current system that may have cascading effect on the structure of plankton community and consequently on the interlinked and delicately balanced food web. Zooplankton species are by definition incapable to perform horizontal moving. Their transport is connected with flowing water. There are zooplankton species specific for the definite water masses and they can be used as markers for the different currents. That allows us to consider zooplankton community composition as a result of water mixing in the studied area. Little is known however about the mechanisms by which spatial and temporal variability in advection affect dynamics of local populations. Ice conditions are also very important in the function of pelagic communities. Melting time is the trigger to all "plankton blooming" processes, and the duration of ice-free conditions determines the food web development in the future. Fram Strait is one of the key regions for the Arctic: the cold water outflow comes through it with the East Greenland Current and meets warm Atlantic water, the West Spitsbergen Current, producing complicated hydrological situation. During 2007 and 2008 we investigated the structure functional characteristics of zooplankton community in the Fram Strait region onboard KV "Svalbard" (April 2007, April and May 2008) and RV "Jan Mayen" (May 2007, August 2008). This study was conducted in frame of iAOOS Norway project "Closing the loop", which, in turn, was a part of IPY. During this cruises multidisciplinary investigations were performed, including sea-ice observations, CTD and ADCP profiling, carbon flux, nutrients and primary production measurements, phytoplankton sampling. Zooplankton was collected with the Hydro-Bios WP2 net and MultiNet Zooplankton Sampler, (mouth area 0.25 m2, mesh size 180 um).Samples were taken from the depth strata of 2000-1500, 1500-1000, 1000-500,500-200, 200-100, 100-60, 60-30, 30-0 m. Gut fluorescence

  10. First results on zooplankton community composition and contamination by some persistent organic pollutants in the Gulf of Tadjoura (Djibouti).

    PubMed

    Boldrocchi, G; Moussa Omar, Y; Rowat, D; Bettinetti, R

    2018-06-15

    The Gulf of Tadjoura is located in the Horn of Africa and is widely recognized as an important site where the zooplanktivorous whale sharks seasonally aggregate from October to February. The surface zooplankton community (0-3m) was weekly sampled from November 2016 to February 2017 in two sites during the whale shark aggregation period. A total of 12 phyla were identified. Copepoda represented the most abundant and diverse group with 29 different genera, and contributed with an average of 82% of the mean zooplankton density of approximately 6600indm -3 . During the sampling period, copepods were dominated numerically by Calanoida (3600indm -3 ), followed by Poicilostomatatoida (1300indm -3 ). Within the copepods, Paracalanidae, Calanidae, Oncaeidae and Miraciidae were the most common families. The temporal trend in zooplankton biomass at both stations revealed the highest peak in December (41.3±36.4mgm -3 ), and the lowest in February (6.6±3.3mgm -3 ). As no information is available on the occurrence of legacy contaminants use and release in this area, analysis revealed the consistent presence of both DDT and PCB residues in zooplankton samples in the Gulf of Tadjoura. Total PCB ranged from approximately 110 to 637ngg -1 d.w., while total DDT from 21 to 80ngg -1 d.w. The proportion of primary DDT in the total residue was higher than DDE and DDD, which strongly suggests that the area might actually be subjected to DDT inputs of the parent compound. Copyright © 2018 Elsevier B.V. All rights reserved.

  11. Trophic accumulation of PSP toxins in zooplankton during Alexandrium fundyense blooms in Casco Bay, Gulf of Maine, April-June 1998. II. . Zooplankton abundance and size-fractionated community composition

    NASA Astrophysics Data System (ADS)

    Turner, Jefferson T.; Doucette, Gregory J.; Keafer, Bruce A.; Anderson, Donald M.

    2005-09-01

    During spring blooms of the toxic dinoflagellate Alexandrium fundyense in Casco Bay, Maine in 1998, we investigated vectorial intoxication of various zooplankton size fractions with PSP toxins, including zooplankton community composition from quantitative zooplankton samples (>102 μm), as well as zooplankton composition in relation to toxin levels in various size fractions (20-64, 64-100, 100-200, 200-500, >500 μm). Zooplankton abundance in 102 μm mesh samples was low (most values<10,000 animals m -3) from early April through early May, but increased to maxima in mid-June (cruise mean=121,500 animals m -3). Quantitative zooplankton samples (>102 μm) were dominated by copepod nauplii, and Oithona similis copepodites and adults at most locations except for those furthest inshore. At these inshore locations, Acartia hudsonica copepodites and adults were usually dominant. Larger copepods such as Calanus finmarchicus, Centropages typicus, and Pseudocalanus spp. were found primarily offshore, and at much lower abundances than O. similis. Rotifers, mainly present from late April to late May, were most abundant inshore. The marine cladoceran Evadne nordmani was sporadically abundant, particularly in mid-June. Microplankton in 20-64 μm size fractions was generally dominated by A. fundyense, non-toxic dinoflagellates, and tintinnids. Microplankton in 64-100 μm size fractions was generally dominated by larger non-toxic dinoflagellates, tintinnids, aloricate ciliates, and copepod nauplii, and in early May, rotifers. Some samples (23%) in the 64-100 μm size fractions contained abundant cells of A. fundyense, presumably due to sieve clogging, but most did not contain A. fundyense cells. This suggests that PSP toxin levels in those samples were due to vectorial intoxication of microzooplankters such as heterotrophic dinoflagellates, tintinnids, aloricate ciliates, rotifers, and copepod nauplii via feeding on A. fundyense cells. Dominant taxa in zooplankton fractions varied

  12. Trophic ecology and vertical patterns of carbon and nitrogen stable isotopes in zooplankton from oxygen minimum zone regions

    NASA Astrophysics Data System (ADS)

    Williams, Rebecca L.; Wakeham, Stuart; McKinney, Rick; Wishner, Karen F.

    2014-08-01

    The unique physical and biogeochemical characteristics of oxygen minimum zones (OMZs) influence plankton ecology, including zooplankton trophic webs. Using carbon and nitrogen stable isotopes, this study examined zooplankton trophic webs in the Eastern Tropical North Pacific (ETNP) OMZ. δ13C values were used to indicate zooplankton food sources, and δ15N values were used to indicate zooplankton trophic position and nitrogen cycle pathways. Vertically stratified MOCNESS net tows collected zooplankton from 0 to 1000 m at two stations along a north-south transect in the ETNP during 2007 and 2008, the Tehuantepec Bowl and the Costa Rica Dome. Zooplankton samples were separated into four size fractions for stable isotope analyses. Particulate organic matter (POM), assumed to represent a primary food source for zooplankton, was collected with McLane large volume in situ pumps. The isotopic composition and trophic ecology of the ETNP zooplankton community had distinct spatial and vertical patterns influenced by OMZ structure. The most pronounced vertical isotope gradients occurred near the upper and lower OMZ oxyclines. Material with lower δ13C values was apparently produced in the upper oxycline, possibly by chemoautotrophic microbes, and was subsequently consumed by zooplankton. Between-station differences in δ15N values suggested that different nitrogen cycle processes were dominant at the two locations, which influenced the isotopic characteristics of the zooplankton community. A strong depth gradient in zooplankton δ15N values in the lower oxycline suggested an increase in trophic cycling just below the core of the OMZ. Shallow POM (0-110 m) was likely the most important food source for mixed layer, upper oxycline, and OMZ core zooplankton, while deep POM was an important food source for most lower oxycline zooplankton (except for samples dominated by the seasonally migrating copepod Eucalanus inermis). There was no consistent isotopic progression among the four

  13. Impact of moderate silver carp biomass gradient on zooplankton communities in a eutrophic reservoir. Consequences for the use of silver carp in biomanipulation.

    PubMed

    Domaizon, I; Dévaux, J

    1999-07-01

    We examined the impacts of moderate gradient silver carp biomass (five levels from 0 to 36 g.m-3, i.e. about 0-792 kg.ha-1) on zooplankton communities of the eutrophic Villerest reservoir (France). During our mesocosm experiment changes in zooplankton assemblages were dependent on silver carp biomass. In the fishless and low fish biomass treatments, zooplankton abundance increased through time, owing to a peak in cladoceran density, but decreased (mainly cladocerans) at highest fish biomass. Copepods and rotifers were less affected at the highest fish biomass and dominated zooplankton communities. We highlighted that the presence of high silver carp biomass could lead to changes in phytoplankton assemblage via the impact on herbivorous zooplankton. Since silver carp efficiently graze on particles > 20 microns, the suppression of herbivorous cladocerans could result in an increase in small size algae (< 20 microns) abundance since these species would be released from grazers as well as competitors (large algae grazed by silver carp) and nutrients levels would be enhanced by fish internal loading. Our results showed that the use of low silver carp biomass (< 200 kg.ha-1) would allow us to minimize these negative effects.

  14. Zooplankton communities in Cenderawasih Bay National Park, West Papua: can their composition be used to predict whale shark Rhincodon typus Smith, 1828 appearance frequencies?

    NASA Astrophysics Data System (ADS)

    Marliana, S. N.; Bataona, M.; Ihsan, E. N.

    2018-03-01

    The use of lift net fishing vessels in Cenderawasih Bay National Park (CBNP) along with the increased popularity of CBNP as an ecotourism area is suspected to have an impact on the behavior and population of its whale sharks Rhincodon typus Smith, 1828. The differing frequency of whale shark appearances along the waters of CBNP has been alleged to be related to the distribution of the whale sharks’ food sources, one of which is zooplankton. This preliminary research aimed to investigate the composition of the zooplankton community in CBNP based on distance from the coast and difference in locations, and to use the pattern of zooplankton compositional variation as a basis for indication of the frequency of whale shark appearances. There were clear differences in the composition and diversity of zooplankton communities among sampling stations, but these differences were not strong enough to infer the cause of the different whale shark appearance frequencies in different locations. Nevertheless, the waters of CBNP had an equal availability of zooplankton for whale sharks. With the increasing popularity of whale shark tourism, understanding the species’ feeding habits is critical to the sustainability of both the industry and the enigmatic species on which it depends.

  15. The response of zooplankton communities to the 2016 extreme hydrological cycle in floodplain lakes connected to the Yangtze River in China.

    PubMed

    Zhang, Kun; Xu, Mei; Wu, Qili; Lin, Zhi; Jiang, Fangyuan; Chen, Huan; Zhou, Zhongze

    2018-06-04

    The Huayanghe Lakes play an important role in the Yangtze floodplain in China and had extremely high water levels during the summer of 2016. Monitoring data was collected in an effort to understand the impact of this change on the crustacean zooplankton composition and abundance and the biomass variation in the Huayanghe Lakes between a regular hydrological cycle (RHC) and an extreme hydrological cycle (EHC). The crustacean zooplankton community composition, abundance, and biomass in the floodplain lakes were markedly affected by the water-level disturbance. The number of species was lower in the RHC, but the mean density and biomass decreased from 93.84 ± 13.29 ind./L and 6.11 ± 0.89 mg/L, respectively, in the RHC to 66.62 ± 10.88 ind./L and 1.22 ± 0.26 mg/L, respectively, in the EHC. Pearson correlations and redundancy analyses revealed the environmental factors with the most significant impact on the crustacean zooplankton community differed between the RHC and EHC cycles. Little previous information exists on the zooplankton in these lakes, and the present study provides data on the zooplankton composition, abundance, and biomass, both at baseline and in response to hydrological changes.

  16. Temporal and spatial variability of zooplankton on the Faroe shelf in spring 1997-2016

    NASA Astrophysics Data System (ADS)

    Jacobsen, Sólvá; Gaard, Eilif; Larsen, Karin Margretha Húsgarð; Eliasen, Sólvá Káradóttir; Hátún, Hjálmar

    2018-01-01

    Zooplankton availability during spring and summer determines the growth and survival of first-feeding fish larvae, and thus impacts the recruitment to both fish prey species and commercial fish stocks. On the Faroe shelf, however, the relative importance of oceanic versus neritic zooplankton species has hitherto not been well understood. In this study, spatio-temporal variability in zooplankton community structure and size spectra on the Faroe shelf is investigated using observations from late April during the period 1997-2016. The main objective was to explore which environmental variables influence the zooplankton community structure in early spring. The zooplankton community in the permanently well mixed central shelf inside the tidal front consists of a mixture of neritic, cosmopolitan and oceanic species. In this region, redundancy analyses showed that chlorophyll concentration had a positive effect on abundance of neritic copepods and meroplankton as well as all zooplankton < 1.2 mm. The abundance variability of these species shows increased production around 2000 and 2008-2009. The highest zooplankton abundance, mainly consisting of Calanus finmarchicus, is however observed off-shore from the tidal front, especially on the western side of the Faroe Plateau. A shift in C. finmarchicus phenology occurred around 2007, resulting in earlier reproduction of this species, and this variability could not be explained by the employed regional environmental parameters. Our results indicate that the Faroe shelf biological production is more dependent on the local primary production and neritic zooplankton species than on the large oceanic C. finmarchicus stock.

  17. Estimation of mortality for stage-structured zooplankton populations: What is to be done?

    NASA Astrophysics Data System (ADS)

    Ohman, Mark D.

    2012-05-01

    Estimation of zooplankton mortality rates in field populations is a challenging task that some contend is inherently intractable. This paper examines several of the objections that are commonly raised to efforts to estimate mortality. We find that there are circumstances in the field where it is possible to sequentially sample the same population and to resolve biologically caused mortality, albeit with error. Precision can be improved with sampling directed by knowledge of the physical structure of the water column, combined with adequate sample replication. Intercalibration of sampling methods can make it possible to sample across the life history in a quantitative manner. Rates of development can be constrained by laboratory-based estimates of stage durations from temperature- and food-dependent functions, mesocosm studies of molting rates, or approximation of development rates from growth rates, combined with the vertical distributions of organisms in relation to food and temperature gradients. Careful design of field studies guided by the assumptions of specific estimation models can lead to satisfactory mortality estimates, but model uncertainty also needs to be quantified. We highlight additional issues requiring attention to further advance the field, including the need for linked cooperative studies of the rates and causes of mortality of co-occurring holozooplankton and ichthyoplankton.

  18. Zooplankton responses to sandbar opening in a tropical eutrophic coastal lagoon

    NASA Astrophysics Data System (ADS)

    Santangelo, Jayme M.; de M. Rocha, Adriana; Bozelli, Reinaldo L.; Carneiro, Luciana S.; de A. Esteves, Francisco

    2007-02-01

    The effects of a disturbance by sandbar opening on the zooplankton community were evaluated through a long-term study in an eutrophic and oligohaline system, Imboassica Lagoon, Rio de Janeiro, Brazil. Zooplankton samples and limnological data were collected monthly from March 2000 to February 2003. Before the sandbar was opened in February 2001, the lagoon showed eutrophic conditions, with high mean nutrient concentrations and low salinity (total nitrogen - TN = 190.28 μM, chlorophyll a content - Chl. a = 104.60 μg/L and salinity = 0.87'). During this period, the zooplankton species present, such as the rotifers Brachionus calyciflorus and Brachionus havanaensis, were typical of freshwater to oligohaline and eutrophic environments. After the sandbar opening, the lagoon changed to a lower trophic status and increased salinity (TN = 55.11 μM, Chl. a = 27.56 μg/L and salinity = 19.64'). As a result, the zooplankton community came to consist largely of the rotifer Brachionus plicatilis, marine copepods and meroplanktonic larvae, mainly Gastropoda. Salinity was the main force structuring the zooplankton community after the sandbar opening. Two years after this episode, the prior zooplankton community had not reestablished itself, indicating a low resilience to this disturbance. The conditions developed prior to a sandbar opening can be crucial to the community responses in the face of this disturbance and for the capacity of the original zooplankton community to re-establish itself.

  19. A New Trait-Based Auto-Emergent Model for Zooplankton and Confrontation with Size-Structured Observations from the Bay of Biscay

    NASA Astrophysics Data System (ADS)

    Vandromme, Pieter; Sourisseau, Marc; Huret, Martin

    2013-04-01

    Zooplankton plays a significant role in marine ecosystems bridging the gap between primary producers and top consumers and interacting with the particle flux through complex dynamics. Scarcity of data and complexity of observing zooplankton make it difficult to integrate it in biogeochemical models where it is most often formulated in a simpler manner, i.e. classic box models with usually two compartments (micro and meso/macro zooplankton). Recent advances in automatic sizing, counting and identification allow better estimates of the dynamics and distribution of zooplankton, notably through the measurement of its size structure, and for zooplankton size matter. Most zooplankton physiological rates as well as predator:prey interactions can be significantly relied to individuals size through allometric relations. Such size-dependency was used in recent models. Yet, these models were neither confronted to observations nor integrated in 3D biogeochemical models. Here we propose a newly developed model of zooplankton dynamics based on size-dependent allometric relations but which allows various diet types regardless of the size. A size and a degree of herbivory is randomly drawn for each zooplankton species generated within the model (up to 400 here, limited by actual computational costs). By generating random degree of herbivory zooplankton species of same size could have various diet (from herbivore to carnivore). Other parameters leading to various reproductive strategies or vertical migration could also be drawn randomly (not tested here). The zooplankton model is coupled to the 3D biogeochemical model MARS3D on a test case representing a simplified view of the Bay of Biscay (i.e., continental shelf, estuary, tides). The model shows auto-emergent properties with the selection of size/diet most adapted to local conditions (here offshore vs. coastal, estuary…). Then, patterns of the modeled size-structure of the zooplankton are confronted to the ones observed during

  20. Effects of drought and pluvial periods on fish and zooplankton communities in prairie lakes: systematic and asystematic responses.

    PubMed

    Starks, Elizabeth; Cooper, Ryan; Leavitt, Peter R; Wissel, Björn

    2014-04-01

    The anticipated impacts of climate change on aquatic biota are difficult to evaluate because of potentially contrasting effects of temperature and hydrology on lake ecosystems, particularly those closed-basin lakes within semiarid regions. To address this shortfall, we quantified decade-scale changes in chemical and biological properties of 20 endorheic lakes in central North America in response to a pronounced transition from a drought to a pluvial period during the early 21st century. Lakes exhibited marked temporal changes in chemical characteristics and formed two discrete clusters corresponding to periods of substantially different effective moisture (as Palmer Drought Severity Index, PDSI). Discriminant function analysis (DFA) explained 90% of variability in fish assemblage composition and showed that fish communities were predicted best by environmental conditions during the arid interval (PDSI <-2). DFA also predicted that lakes could support more fish species during pluvial periods, but their occurrences may be limited by periodic stress due to recurrent droughts and physical barriers to colonization. Zooplankton taxonomic assemblages in fishless lakes were resilient to short-term changes in meteorological conditions, and did not vary between drought and deluge periods. Conversely, zooplankton taxa in fish-populated lakes decreased substantially in biomass during the wet interval, likely due to increased zooplanktivory by fish. The powerful effects of such climatic variability on hydrology and the strong subsequent links to water chemistry and biota indicate that future changes in global climate could result in significant restructuring of aquatic communities. Together these findings suggest that semiarid lakes undergoing temporary climate shifts provide a useful model system for anticipating the effects of global climate change on lake food webs. © 2013 John Wiley & Sons Ltd.

  1. [Effects of environmental factors on β diversity of zooplankton community in thermal discharge seawaters near Guohua Power Plant in Xiangshan Bay, Zhejiang, China].

    PubMed

    Zhu, Yi-feng; Dai, Mei-xia; Zhou, Xiao-hong; Lin, Xia; Mao, Shuo-qian; Yan, Xiao-jun

    2015-08-01

    Zooplankton samples were seasonally collected at 10 stations in thermal discharge seawaters near Guohua Power Plant in Xiangshan Bay. The abundance data from these samples were pooled and further combined with field environmental factors, then generalised dissimilarity modelling (GDM) was used to explore the effects of environmental factors on β diversity of zooplankton community. The results showed that altogether 95 species of zooplankton belonging to 14 taxa were found. In these taxa, small zooplankton with 62.6% of abundance was the main taxa, while copepods dominated in adult groups, which abundance accounted for 35.3%. According to Whittaker's definition and additive partition, a diversity accounted for 36.3% and β diversity 63.7%. Environmental factors explained 43.8% of β diversity, and geographical distance between sampling sites had no effect on β diversity. However, there were still 19.9% of β diversity remained to be explained. After GDM fitting, there were nine environmental variables affecting zooplankton β diversity and explaining 68.8% of β diversity. The variables contributing to β diversity from high to low were seasonal water temperature, dissolved oxygen, seawater temperature increment, conductivity, suspended particulate matter, salinity, transparency, water depth and redox potential, respectively. Seasonal water temperature, dissolved oxygen and seawater temperature increment were the most important factors for driving β diversity changes, and accounted for 23.9%, 13.7% and 9.7% of absolute contribution to the interpretable portion of the β diversity, respectively. When seasonal water temperature, dissolved oxygen and seawater temperature increment were below 25 °C, greater than 5 mg · L(-1) and over 1 °C, respectively, β diversity rapidly increased with the increasing variable gradients. Furthermore, other predictors had little effect on β diversity.

  2. Ecological and Evolutionary Effects of Stickleback on Community Structure

    PubMed Central

    Des Roches, Simone; Shurin, Jonathan B.; Schluter, Dolph; Harmon, Luke J.

    2013-01-01

    Species’ ecology and evolution can have strong effects on communities. Both may change concurrently when species colonize a new ecosystem. We know little, however, about the combined effects of ecological and evolutionary change on community structure. We simultaneously examined the effects of top-predator ecology and evolution on freshwater community parameters using recently evolved generalist and specialist ecotypes of three-spine stickleback (Gasterosteus aculeatus). We used a mesocosm experiment to directly examine the effects of ecological (fish presence and density) and evolutionary (phenotypic diversity and specialization) factors on community structure at lower trophic levels. We evaluated zooplankton biomass and composition, periphyton and phytoplankton chlorophyll-a concentration, and net primary production among treatments containing different densities and diversities of stickleback. Our results showed that both ecological and evolutionary differences in the top-predator affect different aspects of community structure and composition. Community structure, specifically the abundance of organisms at each trophic level, was affected by stickleback presence and density, whereas composition of zooplankton was influenced by stickleback diversity and specialization. Primary productivity, in terms of chlorophyll-a concentration and net primary production was affected by ecological but not evolutionary factors. Our results stress the importance of concurrently evaluating both changes in density and phenotypic diversity on the structure and composition of communities. PMID:23573203

  3. Indicator Properties of Baltic Zooplankton for Classification of Environmental Status within Marine Strategy Framework Directive.

    PubMed

    Gorokhova, Elena; Lehtiniemi, Maiju; Postel, Lutz; Rubene, Gunta; Amid, Callis; Lesutiene, Jurate; Uusitalo, Laura; Strake, Solvita; Demereckiene, Natalja

    2016-01-01

    The European Marine Strategy Framework Directive requires the EU Member States to estimate the level of anthropogenic impacts on their marine systems using 11 Descriptors. Assessing food web response to altered habitats is addressed by Descriptor 4 and its indicators, which are being developed for regional seas. However, the development of simple foodweb indicators able to assess the health of ecologically diverse, spatially variable and complex interactions is challenging. Zooplankton is a key element in marine foodwebs and thus comprise an important part of overall ecosystem health. Here, we review work on zooplankton indicator development using long-term data sets across the Baltic Sea and report the main findings. A suite of zooplankton community metrics were evaluated as putative ecological indicators that track community state in relation to Good Environmental Status (GES) criteria with regard to eutrophication and fish feeding conditions in the Baltic Sea. On the basis of an operational definition of GES, we propose mean body mass of zooplankton in the community in combination with zooplankton stock measured as either abundance or biomass to be applicable as an integrated indicator that could be used within the Descriptor 4 in the Baltic Sea. These metrics performed best in predicting zooplankton being in-GES when considering all datasets evaluated. However, some other metrics, such as copepod biomass, the contribution of copepods to the total zooplankton biomass or biomass-based Cladocera: Copepoda ratio, were equally reliable or even superior in certain basin-specific assessments. Our evaluation suggests that in several basins of the Baltic Sea, zooplankton communities currently appear to be out-of-GES, being comprised by smaller zooplankters and having lower total abundance or biomass compared to the communities during the reference conditions; however, the changes in the taxonomic structure underlying these trends vary widely across the sea basins due to

  4. Acoustic classification of zooplankton

    NASA Astrophysics Data System (ADS)

    Martin Traykovski, Linda V.

    1998-11-01

    Work on the forward problem in zooplankton bioacoustics has resulted in the identification of three categories of acoustic scatterers: elastic-shelled (e.g. pteropods), fluid-like (e.g. euphausiids), and gas-bearing (e.g. siphonophores). The relationship between backscattered energy and animal biomass has been shown to vary by a factor of ~19,000 across these categories, so that to make accurate estimates of zooplankton biomass from acoustic backscatter measurements of the ocean, the acoustic characteristics of the species of interest must be well-understood. This thesis describes the development of both feature based and model based classification techniques to invert broadband acoustic echoes from individual zooplankton for scatterer type, as well as for particular parameters such as animal orientation. The feature based Empirical Orthogonal Function Classifier (EOFC) discriminates scatterer types by identifying characteristic modes of variability in the echo spectra, exploiting only the inherent characteristic structure of the acoustic signatures. The model based Model Parameterisation Classifier (MPC) classifies based on correlation of observed echo spectra with simplified parameterisations of theoretical scattering models for the three classes. The Covariance Mean Variance Classifiers (CMVC) are a set of advanced model based techniques which exploit the full complexity of the theoretical models by searching the entire physical model parameter space without employing simplifying parameterisations. Three different CMVC algorithms were developed: the Integrated Score Classifier (ISC), the Pairwise Score Classifier (PSC) and the Bayesian Probability Classifier (BPC); these classifiers assign observations to a class based on similarities in covariance, mean, and variance, while accounting for model ambiguity and validity. These feature based and model based inversion techniques were successfully applied to several thousand echoes acquired from broadband (~350 k

  5. Feeding ecology of pelagic fish species in the Gulf of Riga (Baltic Sea): the importance of changes in the zooplankton community.

    PubMed

    Lankov, A; Ojaveer, H; Simm, M; Põllupüü, M; Möllmann, C

    2010-12-01

    The feeding ecology of four pelagic fish species was studied in relation to their prey availability in the Gulf of Riga (Baltic Sea) during the summer 1999-2006. The zooplankton community was dominated by the cladoceran Bosmina longispina, rotifers Keratella cochlearis and K. quadrata and the copepod Eurytemora affinis, with the highest interannual variability in abundance recorded for B. longispina. The last influenced the diet of adult sprat Sprattus sprattus, juvenile smelt Osmerus eperlanus and three-spined stickleback Gasterosteus aculeatus as these were strongly selecting for B. longispina. The fish feeding activity did not match the abundance dynamics of their preferred prey, suggesting that fishes may switch to consume other prey in case the preferred diet was limited. A considerable dietary overlap indicated high potential competition between pelagic fish species. While herring Clupea harengus membras and G. aculeatus were relying on very different food, the diets of young O. eperlanus and G. aculeatus were very similar. Interannual variability in zooplankton composition and abundance significantly affected the diet composition of fishes, but those changes were insufficient to exert a consistent influence upon fish feeding activity and total amounts of zooplankton consumed. © 2010 The Authors. Journal of Fish Biology © 2010 The Fisheries Society of the British Isles.

  6. Spatial patterns of littoral zooplankton assemblages along a salinity gradient in a brackish sea: A functional diversity perspective

    NASA Astrophysics Data System (ADS)

    Helenius, Laura K.; Leskinen, Elina; Lehtonen, Hannu; Nurminen, Leena

    2017-11-01

    The distribution patterns and diversity of littoral zooplankton are both key baseline information for understanding the functioning of coastal ecosystems, and for identifying the mechanisms by which the impacts of recently increased eutrophication are transferred through littoral food webs. In this study, zooplankton community structure and diversity along a shallow coastal area of the northern Baltic Sea were determined in terms of horizontal environmental gradients. Spatial heterogeneity of the zooplankton community was examined along the gradient. Altogether 31 sites in shallow sandy bays on the coast of southwest Finland were sampled in the summer periods of 2009 and 2010 for zooplankton and environmental variables (surface water temperature, salinity, turbidity, wave exposure, macrophyte coverage, chlorophyll a and nutrients). Zooplankton diversity was measured as both taxonomic as well as functional diversity, using trait-based classification of planktonic crustaceans. Salinity, and to a lesser extent turbidity and temperature, were found to be the main predictors of the spatial patterns and functional diversity of the zooplankton community. Occurrence of cyclopoid copepods, as well as abundances of the calanoid copepod genus Acartia and the rotifer genus Keratella were found to be key factors in differentiating sites along the gradient. As far as we know, this is the first extensive study of functional diversity in Baltic Sea coastal zooplankton communities.

  7. Comparing seasonal dynamics of the Lake Huron zooplankton community between 1983-1984 and 2007 and revisiting the impact of Bythotrephes planktivory

    Bunnell, David B.; Keeler, Kevin M.; Puchala, Elizabeth A.; Davis, Bruce M.; Pothoven, Steven A.

    2012-01-01

    Zooplankton community composition can be influenced by lake productivity as well as planktivory by fish or invertebrates. Previous analyses based on long-term Lake Huron zooplankton data from August reported a shift in community composition between the 1980s and 2000s: proportional biomass of calanoid copepods increased while that of cyclopoid copepods and herbivorous cladocerans decreased. Herein, we used seasonally collected data from Lake Huron in 1983–1984 and 2007 and reported similar shifts in proportional biomass. We also used a series of generalized additive models to explore differences in seasonal abundance by species and found that all three cyclopoid copepod species (Diacyclops thomasi, Mesocylops edax, Tropocyclops prasinus mexicanus) exhibited higher abundance in 1983–1984 than in 2007. Surprisingly, only one (Epischura lacustris) of seven calanoid species exhibited higher abundance in 2007. The results for cladocerans were also mixed with Bosmina spp. exhibiting higher abundance in 1983–1984, while Daphnia galeata mendotae reached a higher level of abundance in 2007. We used a subset of the 2007 data to estimate not only the vertical distribution of Bythotrephes longimanus and their prey, but also the consumption by Bythotrephes in the top 20 m of water. This epilimnetic layer was dominated by copepod copepodites and nauplii, and consumption either exceeded (Hammond Bay site) or equaled 65% (Detour site) of epilimnetic zooplankton production. The lack of spatial overlap between Bythotrephes and herbivorous cladocerans and cyclopoid copepod prey casts doubt on the hypothesis that Bythotrephes planktivory was the primary driver underlying the community composition changes in the 2000s.

  8. Zooplankton research off Peru: A review

    NASA Astrophysics Data System (ADS)

    Ayón, Patricia; Criales-Hernandez, Maria I.; Schwamborn, Ralf; Hirche, Hans-Jürgen

    2008-10-01

    A review of zooplankton studies conducted in Peruvian marine waters is given. After a short history of the development of zooplankton research off Peru, we review zooplankton methodology, taxonomy, biodiversity, spatial distribution, seasonal and interannual variability, trophodynamics, secondary production, and modelling. We review studies on several micro-, meso-, macro-, and meroplankton groups, and give a species list from both published and unpublished reports. Three regional zooplankton groups have been identified: (1) a continental shelf group dominated by Acartia tonsa and Centropages brachiatus; (2) a continental slope group characterized by siphonophores, bivalves, foraminifera and radiolaria; (3) and a species-rich oceanic group. The highest zooplankton abundances and biomasses were often found between 4-6°S and 14-16°S, where continental shelves are narrow. Species composition changes with distance from the shore. Species composition and biomass also vary strongly on short time scales due to advection, peaks of larval production, trophic interactions, and community succession. The relation of zooplankton to climatic variability (ENSO and multi-decadal) and fish stocks is discussed in the context of ecological regime shifts. An intermediate upwelling hypothesis is proposed, based on the negative effects of low upwelling intensity in summer or extremely strong and enduring winter upwelling on zooplankton abundance off Peru. According to this hypothesis, intermediate upwelling creates an optimal environmental window for zooplankton communities. Finally, we highlight important knowledge gaps that warrant attention in future.

  9. Dynamics of suprabenthos-zooplankton communities around the Balearic Islands (western Mediterranean): Influence of environmental variables and effects on the biological cycle of Aristeus antennatus

    NASA Astrophysics Data System (ADS)

    Cartes, J. E.; Madurell, T.; Fanelli, E.; López-Jurado, J. L.

    salinity close to the bottom, suggesting a link between suprabenthos abundance and changes in the oceanographic condition of water masses close to the bottom. It is suggested that a higher suprabenthos biomass recorded off Sóller in comparison to that off Cabrera in June could, in turn, be related to a seasonal inflow of Levantine Intermediate Water (LIW) in April-June in this area at mid bathyal depths (350-650 m). This trend would be based on: 1) it was evident only at mid-slope depths between 350-750 m, coinciding with the LIW distribution, and 2) it was not recorded among zooplankton (collected throughout the water column). The possible effect of the fluctuations of suprabenthos and zooplankton on higher trophic levels has been explored studying the diet and food consumption rates of the red shrimp Aristeus antennatus, as indicator species by its dominance in bathyal communities. A. antennatus increased its food consumption from February to April-June 2004 off Sóller, which in the case of large (CL > 40 mm) specimens was found in both areas. In addition, there was a shift of diet from winter to spring-early summer. In this last period, A. antennatus preyed upon euphausiids and mesopelagic decapods and fish, while benthos (e.g. polychaetes and bivalves) decreased in the diet. This indicates an increase in the food consumption and probably in the caloric content of the diet in pre-spawning females in April-June 2004, which is synchronized with the period when gonad development begins in A. antennatus females (May-June). Anyway, macrozooplankton, and not suprabenthos, is crucial as a high energetic food source in the coupling between food intake and reproduction in the red shrimp.

  10. Seasonal Phenology of Zooplankton Composition in the Southeastern Bering Sea, 2008-2010

    NASA Astrophysics Data System (ADS)

    Eisner, L. B.; Pinchuk, A. I.; Harpold, C.; Siddon, E. C.; Mier, K.

    2016-02-01

    The availability of large crustacean zooplankton prey is critical to the condition and survival of forage fish (e.g., age-0 Walleye Pollock), sea birds, and marine mammals in the eastern Bering Sea. Zooplankton community composition and abundances of large lipid-rich copepods (e.g., Calanus spp.) have been evaluated for single seasons, but few studies have investigated seasonal variations in this region. Here, we investigate seasonal changes in taxa (community structure), stage composition (where appropriate), and diversity from spring through late summer/early fall over three consecutive colder than average years. Zooplankton taxonomic samples were collected with oblique bongo tows over the water column during spring (April-May), mid-summer (June-July) and late summer/early fall (August-September) across the southeastern Bering Sea shelf in 2008-2010. Zooplankton abundances were evaluated by oceanographic region, season and year, and related to water mass characteristics (temperature and salinity) and other environmental drivers. Finally, zooplankton phenology was compared to changes in forage fish composition to determine potential overlap of fish predators and zooplankton prey.

  11. Biotic and abiotic factors influencing zooplankton vertical distribution in Lake Huron

    Nowicki, Carly J.; Bunnell, David B.; Armenio, Patricia M.; Warner, David M.; Vanderploeg, Henry A.; Cavaletto, Joann F.; Mayer, Christine M.; Adams, Jean V.

    2017-01-01

    The vertical distribution of zooplankton can have substantial influence on trophic structure in freshwater systems, particularly by determining spatial overlap for predator/prey dynamics and influencing energy transfer. The zooplankton community in some of the Laurentian Great Lakes has undergone changes in composition and declines in total biomass, especially after 2003. Mechanisms underlying these zooplankton changes remain poorly understood, in part, because few studies have described their vertical distributions during daytime and nighttime conditions or evaluated the extent to which predation, resources, or environmental conditions could explain their distribution patterns. Within multiple 24-h periods during July through October 2012 in Lake Huron, we conducted daytime and nighttime sampling of zooplankton, and measured food (chlorophyll-a), temperature, light (Secchi disk depth), and planktivory (biomass of Bythotrephes longimanus and Mysis diluviana). We used linear mixed models to determine whether the densities for 22 zooplankton taxa varied between day and night in the epi-, meta-, and hypolimnion. For eight taxa, higher epilimnetic densities were observed at night than during the day; general linear models revealed these patterns were best explained by Mysis diluviana (four taxa), Secchi disk depth (three taxa), epilimnetic water temperature (three taxa), chlorophyll (one taxon), and biomass of Bythotrephes longimanus (one taxon). By investigating the potential effects of both biotic and abiotic variables on the vertical distribution of crustacean zooplankton and rotifers, we provide descriptions of the Lake Huron zooplankton community and discuss how future changes in food web dynamics or climate change may alter zooplankton distribution in freshwater environments.

  12. The impact of different hydrographic conditions and zooplankton communities on provisioning Little Auks along the West coast of Spitsbergen

    NASA Astrophysics Data System (ADS)

    Kwasniewski, Slawomir; Gluchowska, Marta; Jakubas, Dariusz; Wojczulanis-Jakubas, Katarzyna; Walkusz, Wojciech; Karnovsky, Nina; Blachowiak-Samolyk, Katarzyna; Cisek, Malgorzata; Stempniewicz, Lech

    2010-10-01

    Composition and abundance of zooplankton were studied simultaneously with feeding ecology of planktivorous Little Auks ( Alle alle) in two different sea shelf areas of West Spitsbergen, Norway, in summer 2007. Zooplankton was collected adjacent to bird colonies in Magdalenefjorden (influenced by Atlantic West Spitsbergen Current) and Hornsund (dominated by the Arctic Sørkapp Current). In spite of different hydrological situations, the abundance of prey preferred by Little Auks, Arctic Calanus glacialis copepodids stage V, among zooplankton was similar in both localities. However, there was much more of Atlantic Calanus finmarchicus on the shelf outside Magdalenefjorden compared to Hornsund, resulting in different abundance ratios of Arctic to Atlantic copepods in the two areas (1:14 and 1:1, respectively). Even greater differences between the two areas occurred in the ratio of C. glacialis CV to other zooplankters, amounting to 1:40 in Magdalenefjorden and 1:6 in Hornsund. In both Little Auk colonies food brought by parents to their chicks contained mainly C. glacialis CV, albeit the proportion of this copepod in meals was significantly higher in Hornsund. Meals delivered to Little Auk chicks in Hornsund had also higher zooplankton numbers, biomass and energy content. In Magdalenefjorden, on the other hand, a higher number of feedings and longer duration of foraging trips were recorded. These differences became more apparent with increasing energy requirements of the fast growing nestlings. This was probably a consequence of lower relative abundance of the Little Auks’ preferred prey in the sea adjacent to Magdalenefjorden colony. It seems that searching for the preferred food items, such as C. glacialis, among abundant but less favored C. finmarchicus, may require more time and energy demanding foraging behavior. As a consequence, foraging effort of the Little Auk parents from Magdalenefjorden was higher, and feeding efficiency lower, than those of birds from

  13. Community structure in networks

    NASA Astrophysics Data System (ADS)

    Newman, Mark

    2004-03-01

    Many networked systems, including physical, biological, social, and technological networks, appear to contain ``communities'' -- groups of nodes within which connections are dense, but between which they are sparser. The ability to find such communities in an automated fashion could be of considerable use. Communities in a web graph for instance might correspond to sets of web sites dealing with related topics, while communities in a biochemical network or an electronic circuit might correspond to functional units of some kind. We present a number of new methods for community discovery, including methods based on ``betweenness'' measures and methods based on modularity optimization. We also give examples of applications of these methods to both computer-generated and real-world network data, and show how our techniques can be used to shed light on the sometimes dauntingly complex structure of networked systems.

  14. The structure and evolution of plankton communities

    NASA Astrophysics Data System (ADS)

    Longhurst, Alan R.

    New understanding of the circulation of ancient oceans is not yet matched by progress in our understanding of their pelagic ecology, though it was the planktonic ecosystems that generated our offshore oil and gas reserves. Can we assume that present-day models of ecosystem function are also valid for ancient seas? This question is addressed by a study of over 4000 plankton samples to derive a comprehensive, global description of zooplankton community structure in modern oceans: this shows that copepods form only 50% of the biomass of all plankton, ranging from 70% in polar to 35% in tropical seas. Comparable figures are derived from 14 other taxonomic categories of zooplankton. For trophic groupings, the data indicate globally: geletinous predators - 14%; gelatinous herbivores - 4%; raptorial predators - 33%; macrofiltering herbivores - 20%; macrofiltering omnivores - 25%; and detritivores - 3%. A simple, idealized model for the modern pelagic ecosystem is derived from these percentages which indicates that metazooplankton are not the most important consumers of pico- and nano-plankton production which itself probably constitutes 90% of primary production in warm oceans. This model is then compared with candidate life-forms available in Palaeozoic and Mesozoic oceans to determine to what extent it is also valid for ancient ecosystems: it is concluded that it is probably unnecessary to postulate models fundamentally differing from it in order to accommodate the life-forms, both protozoic and metazoic, known to have populated ancient seas. Remarkably few life-forms have existed which cannot be paralleled in the modern ocean, which contains remarkably few life-forms which cannot be paralleled in the Palaeozoic ocean. As a first assumption, then, it is reasonable to assume that energy pathways were similar in ancient oceans to those we study today.

  15. DNA Barcoding of Zooplankton in the Hampton Roads Area: A Biodiversity Assessment

    NASA Astrophysics Data System (ADS)

    Salcedo, A.; Rodríguez, Á. E.; Gibson, D. M.

    2016-02-01

    The study of zooplankton biodiversity and distribution is crucial to understand oceanic ecosystems and anticipate the effects of climate change. Previously, identification of zooplankton relied in morphological identification employed by expert taxonomists. DNA barcoding, a technique that uses the mitochondrial DNA (mtDNA) Cytochrome Oxidase 1 (CO1) gene is widely used for taxonomic identification. Thus, this molecular technique will be used to begin a detailed characterization of zooplankton diversity, abundance and community structure in the Hampton Roads Area (HRA). Stations 1 (Jones Creek) and 3 (lower Chesapeake Bay) were sampled in June 19, 2015. Stations 1, 2 (James River), and 3 were sampled in September 2015. Zooplankton samples were collected in triplicates with a 0.5m, 200 µm mesh net. Physical parameters (dissolved oxygen, salinity, temperature and, water transparency) were measured. Species identified as Opistonema oglinum (Atlantic Thread Herring) and Paracalanus parvus copepods were found at station 3; Anchoa mitchilli and Acartia tonsa copepods were found at stations 1 and 3. This study indicates that mtDNA-CO1 barcoding is suitable to identify zooplankton to the species level and helps validate DNA barcoding as a faster, more accurate taxonomic approach. The long term objective of this project is to provide a comprehensive assessment of zooplankton in the HRA and to generate a reference record for broad monitoring programs; vital for a better understanding and management of ecologically and commercially important species.

  16. Estimating carnivore community structures

    PubMed Central

    Jiménez, José; Nuñez-Arjona, Juan Carlos; Rueda, Carmen; González, Luis Mariano; García-Domínguez, Francisco; Muñoz-Igualada, Jaime; López-Bao, José Vicente

    2017-01-01

    Obtaining reliable estimates of the structure of carnivore communities is of paramount importance because of their ecological roles, ecosystem services and impact on biodiversity conservation, but they are still scarce. This information is key for carnivore management: to build support for and acceptance of management decisions and policies it is crucial that those decisions are based on robust and high quality information. Here, we combined camera and live-trapping surveys, as well as telemetry data, with spatially-explicit Bayesian models to show the usefulness of an integrated multi-method and multi-model approach to monitor carnivore community structures. Our methods account for imperfect detection and effectively deal with species with non-recognizable individuals. In our Mediterranean study system, the terrestrial carnivore community was dominated by red foxes (0.410 individuals/km2); Egyptian mongooses, feral cats and stone martens were similarly abundant (0.252, 0.249 and 0.240 individuals/km2, respectively), whereas badgers and common genets were the least common (0.130 and 0.087 individuals/km2, respectively). The precision of density estimates improved by incorporating multiple covariates, device operation, and accounting for the removal of individuals. The approach presented here has substantial implications for decision-making since it allows, for instance, the evaluation, in a standard and comparable way, of community responses to interventions. PMID:28120871

  17. Avoidance of strobe lights by zooplankton

    Hamel, Martin J.; Richards, Nathan S.; Brown, Michael L.; Chipps, Steven R.

    2010-01-01

    Underwater strobe lights can influence the behavior and distribution of fishes and are increasingly used as a technique to divert fish away from water intake structures on dams. However, few studies examine how strobe lights may affect organisms other than targeted species. To gain insight on strobe lighting effects on nontarget invertebrates, we investigated whether underwater strobe lights influence zooplankton distributions and abundance in Lake Oahe, South Dakota. Zooplankton were collected using vertical tows at 3 discrete distances from an underwater strobe light to quantify the influence of light intensity on zooplankton density. Samples were collected from 3 different depth ranges (0–10 m, 10–20 m and 20–30 m) at <1 m, 15 m and ⩾100 m distance intervals away from the strobe light. Copepods represented 67.2% and Daphnia spp. represented 23.3% of all zooplankton sampled from 17 August to 15 September 2004. Night time zooplankton densities significantly decreased in surface waters when strobe lights were activated. Copepods exhibited the greatest avoidance patterns, while Daphnia avoidance varied throughout sampling depths. These results indicate that zooplankton display negative phototaxic behavior to strobe lights and that researchers must be cognizant of potential effects to the ecosystem such as altering predator–prey interactions or affecting zooplankton distribution and growth.

  18. If you see one, have you seen them all?: Community-wide effects of insecticide cross-resistance in zooplankton populations near and far from agriculture.

    PubMed

    Bendis, Randall J; Relyea, Rick A

    2016-08-01

    The worldwide use of pesticides has led to increases in agricultural yields by reducing crop losses. However, increased pesticide use has resulted in pesticide-resistant pest species and recent studies have discovered pesticide-resistance in non-target species living close to farms. Such increased tolerance not only affects the species, but can alter the entire food web. Given that some species can evolve not only resistance to a single pesticide, but also cross-resistance to other pesticides that share the same mode of action, one would predict that cross-resistance to pesticides would also have effects on the entire community and affect community stability. To address this hypothesis, we conducted an outdoor mesocosm experiment comprised of 200 identical aquatic communities with phytoplankton, periphyton, and leopard frog (Lithobates pipiens) tadpoles. To these communities, we added one of four Daphnia pulex populations that we previously discovered were either resistant or sensitive to the insecticide of chlorpyrifos as a result of living close to or far from agriculture, respectively. We then exposed the communities to either no insecticide or three different concentrations of AChE-inhibiting insecticides (chlorpyrifos, malathion or carbaryl) or sodium channel-inhibiting insecticides (permethrin or cypermethrin). We discovered that communities containing sensitive Daphnia pulex experienced phytoplankton blooms and subsequent cascades through all trophic groups including amphibians at moderate to high concentrations of all five insecticides. However, communities containing resistant D. pulex were buffered from these effects at low to moderate concentrations of all AChE-inhibiting insecticides, but were not buffered against the pyrethroid insecticides. These data suggest that a simple change in the population-level resistance of zooplankton to a single insecticide can have widespread consequences for community stability and that the effects can be extrapolated

  19. UV radiation and freshwater zooplankton: damage, protection and recovery

    PubMed Central

    Rautio, Milla; Tartarotti, Barbara

    2011-01-01

    While many laboratory and field studies show that zooplankton are negatively affected when exposed to high intensities of ultraviolet radiation (UVR), most studies also indicate that zooplankton are well adapted to cope with large variations in their UVR exposure in the pelagic zone of lakes. The response mechanisms of zooplankton are diverse and efficient and may explain the success and richness of freshwater zooplankton in optically variable waters. While no single behavioural or physiological protection mechanism seems to be superior, and while several unexplained and contradictory patterns exist in zooplankton UVR ecology, recent increases in our understanding are consistent with UVR playing an important role for zooplankton. This review examines the variability in freshwater zooplankton responses to UVR, with a focus on crustacean zooplankton (Cladocera and Copepoda). We present an overview of UVR-induced damages, and the protection and recovery mechanisms freshwater zooplankton use when exposed to UVR. We review the current knowledge of UVR impact on freshwater zooplankton at species and community levels, and discuss briefly how global change over the last three decades has influenced the UVR milieu in lakes. PMID:21516254

  20. Using occupancy modeling to compare traditional versus DNA metabarcoding methods for characterizing zooplankton biodiversity

    EPA Science Inventory

    DNA metabarcoding tools could increase our ability to detect changes in zooplankton communities and to detect invasive zooplankton taxa while they are still rare. Nonetheless, the use of DNA-metabarcoding for characterizing zooplankton biodiversity in the Great Lakes has not bee...

  1. High evolutionary potential of marine zooplankton

    PubMed Central

    Peijnenburg, Katja T C A; Goetze, Erica

    2013-01-01

    Abstract Open ocean zooplankton often have been viewed as slowly evolving species that have limited capacity to respond adaptively to changing ocean conditions. Hence, attention has focused on the ecological responses of zooplankton to current global change, including range shifts and changing phenology. Here, we argue that zooplankton also are well poised for evolutionary responses to global change. We present theoretical arguments that suggest plankton species may respond rapidly to selection on mildly beneficial mutations due to exceptionally large population size, and consider the circumstantial evidence that supports our inference that selection may be particularly important for these species. We also review all primary population genetic studies of open ocean zooplankton and show that genetic isolation can be achieved at the scale of gyre systems in open ocean habitats (100s to 1000s of km). Furthermore, population genetic structure often varies across planktonic taxa, and appears to be linked to the particular ecological requirements of the organism. In combination, these characteristics should facilitate adaptive evolution to distinct oceanographic habitats in the plankton. We conclude that marine zooplankton may be capable of rapid evolutionary as well as ecological responses to changing ocean conditions, and discuss the implications of this view. We further suggest two priority areas for future research to test our hypothesis of high evolutionary potential in open ocean zooplankton, which will require (1) assessing how pervasive selection is in driving population divergence and (2) rigorously quantifying the spatial and temporal scales of population differentiation in the open ocean. Recent attention has focused on the ecological responses of open ocean zooplankton to current global change, including range shifts and changing phenology. Here, we argue that marine zooplankton also are well poised for evolutionary responses to global change. PMID:24567838

  2. Emergent Macrophytes Support Zooplankton in a Shallow Tropical Lake: A Basis for Wetland Conservation

    NASA Astrophysics Data System (ADS)

    Gebrehiwot, Mesfin; Kifle, Demeke; Triest, Ludwig

    2017-12-01

    Understanding the biodiversity value of littoral zones of lakes is a priority for aquatic biodiversity conservation. However, less emphasis has been given to the littoral part of tropical African lakes, with many of the previous researches focusing only on the open water side. The aim of the present study was, therefore, to investigate the impact of the littoral zone of a shallow freshwater tropical lake (Ziway, Ethiopia), dominated by two emergent macrophytes, on zooplankton community structure. We hypothesized that the wetland vegetation serves as a preferred microhabitat for zooplankton communities. A lake with substantial coverage of emergent macrophytes was monitored monthly from January to August, 2016. The monitoring included the measurements of physical, chemical, and biological parameters. Sampling sites were selected to represent areas of the macrophyte vegetation ( Typha latifolia and Phragmites australis) and the open water part of the lake. Sites with macrophyte vegetation were found to be the home of more dense and diverse zooplankton community. However, during the period of high vegetation loss, the density of crustacean zooplankton showed significant reduction within the patches of macrophytes. From biodiversity conservation perspective, it was concluded that the preservation of such small areas of macrophytes covering the littoral zone of lakes could be as important as protecting the whole lake. However, the rapid degradation of wetland vegetation by human activities is a real threat to the lake ecosystem. In the not-too-far future, it could displace and evict riparian vegetation and the biota it supports.

  3. Zooplankton time-series in the Balearic Sea (Western Mediterranean): Variability during the decade 1994 2003

    NASA Astrophysics Data System (ADS)

    Fernández de Puelles, Maria Luz; Alemany, Francisco; Jansá, Javier

    2007-08-01

    Studies of plankton time-series from the Balearic islands waters are presented for the past decade, with main emphasis on the variability of zooplankton and how it relates to the environment. The seasonal and interannual patterns of temperature, salinity, nutrients, chlorophyll concentration and zooplankton abundance are described with data obtained between 1994 and 2003. Samples were collected every 10 days at a monitoring station in the Mallorca channel, an area with marked hydrographic variability in the Western Mediterranean. Mesoscale variability was also assessed using data from monthly sampling survey carried out between 1994 and 1999 in a three station transect located in the same study area. The copepods were the most abundant group with three higher peaks (March, May and September) distinguished during the annual cycle and a clear coastal-offshore decreasing gradient. Analysis of the zooplankton community revealed two distinct periods: the mixing period during winter and early spring, where copepods, siphonophores and ostracods were most abundant and, the stratified period characterised by an increase of cladocerans and meroplankton abundances. Remarkable interannual zooplankton variability was observed in relation to hydrographic regime with higher abundances of main groups during cool years, when northern Mediterranean waters prevailed in the area. The warmer years showed the lowest zooplankton abundances, associated with the inflow of less saline and nutrient-depleted Atlantic Waters. Moreover, the correlation found between copepod abundance and large scale climatic factors (e.g., NAO) suggested that they act as main driver of the zooplankton variability. Therefore, the seasonal but particularly the interannual variation observed in plankton abundance and structure patterns of the Balearic Sea seems to be highly modulated by large-scale forcing and can be considered an ideal place where to investigate potential consequences of global climate change.

  4. Functional diversity of zooplankton communities in two tropical estuaries (NE Brazil) with different degrees of human-induced disturbance.

    PubMed

    Veríssimo, Helena; Patrício, Joana; Gonçalves, Érica; Moura, Gustavo C; Barbosa, José Etham L; Gonçalves, Ana M M

    2017-08-01

    This study assessed the functional diversity (FD) of copepod communities along the environmental gradient of two tropical estuaries with different intensities of human impact - the environmentally protected "Mamanguape" and the urbanised "Paraiba". Different trait-based approaches were used: functional groups identification and description, and FD indices estimation. The results showed similar functional groups and functional indices between the two estuaries with some variability attributed to seasonality. Copepods in each estuary seemed to perform similar functions. Overall, biomass was more evenly distributed among groups, and mean total biomass and FD indices were slightly higher in the Mamanguape. Nevertheless, both estuaries presented comparable FD, indicating that environmental filters may be the main driver of species coexistence within systems. Results also pointed towards anthropogenic disturbance, despite the protection status of the Mamanguape. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Synchronous dynamics of zooplankton competitors prevail in temperate lake ecosystems.

    PubMed

    Vasseur, David A; Fox, Jeremy W; Gonzalez, Andrew; Adrian, Rita; Beisner, Beatrix E; Helmus, Matthew R; Johnson, Catherine; Kratina, Pavel; Kremer, Colin; de Mazancourt, Claire; Miller, Elizabeth; Nelson, William A; Paterson, Michael; Rusak, James A; Shurin, Jonathan B; Steiner, Christopher F

    2014-08-07

    Although competing species are expected to exhibit compensatory dynamics (negative temporal covariation), empirical work has demonstrated that competitive communities often exhibit synchronous dynamics (positive temporal covariation). This has led to the suggestion that environmental forcing dominates species dynamics; however, synchronous and compensatory dynamics may appear at different length scales and/or at different times, making it challenging to identify their relative importance. We compiled 58 long-term datasets of zooplankton abundance in north-temperate and sub-tropical lakes and used wavelet analysis to quantify general patterns in the times and scales at which synchronous/compensatory dynamics dominated zooplankton communities in different regions and across the entire dataset. Synchronous dynamics were far more prevalent at all scales and times and were ubiquitous at the annual scale. Although we found compensatory dynamics in approximately 14% of all combinations of time period/scale/lake, there were no consistent scales or time periods during which compensatory dynamics were apparent across different regions. Our results suggest that the processes driving compensatory dynamics may be local in their extent, while those generating synchronous dynamics operate at much larger scales. This highlights an important gap in our understanding of the interaction between environmental and biotic forces that structure communities. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  6. Ecological Principles Affecting Community Structure and Secondary Production by Zooplankton in Marine and Freshwater Environments

    DTIC Science & Technology

    1988-01-01

    Bialv~al can be common lipid -accumulating copepods or euphau- siids. The latitudinal trend in species rich- ness of freshwaters is the opposite...Cretaceous large- dinosaur com- er. For this reason it is most secure to focus munity (Oldman Formation). Ecology 57: 841- measurement effort on the

  7. Changes to zooplankton community structure following colonization of a small lake by Leptodora kindti

    McNaught, A.S.; Kiesling, R.L.; Ghadouani, A.

    2004-01-01

    The predaceous cladoceran Leptodora kindti (Focke) became established in Third Sister Lake, Michigan, after individuals escaped from experimental enclosures in 1987. By 1988, the Leptodora population exhibited seasonal dynamics characteristic of natural populations. The maximum seasonal abundance of Leptodora increased to 85 individuals m-3 3 yr following the introduction. After the appearance of Leptodora, small-bodied cladocerans (Ceriodaphnia and Bosmina) virtually disappeared from the lake. There were strong seasonal shifts in the dominance patterns of both cladocerans and copepods, and Daphnia species diversity increased. Results from this unplanned introduction suggest that invertebrate predators can have a rapid and lasting effect on prey populations, even in the presence of planktivorous fish. Small-scale (<20 km) geographic barriers might be as important as large-scale barriers to dispersal of planktonic animals.

  8. Seasonal cycles of zooplankton from San Francisco Bay

    Ambler, Julie W.; Cloern, James E.; Hutchinson, Anne

    1985-01-01

    Seasonal cycles of zooplankton abundance appear to be constant among years (1978–1981) and are similar in the deep (>10 m) channels and lateral shoals (<3 m). The seasonal zooplankton community dynamics are discussed in relation to: (1) river discharge which alters salinity distribution and residence time of plankton; (2) temperature which induces production and hatching of dormant copepod eggs; (3) coastal hydrography which brings neritic copepods of different zoogeographic affinities into the bay; and (4) seasonal cycles of phytoplankton.

  9. Characterization of Lake Michigan coastal lakes using zooplankton assemblages

    Whitman, Richard L.; Nevers, Meredith B.; Goodrich, Maria L.; Murphy, Paul C.; Davis, Bruce M.

    2004-01-01

    Zooplankton assemblages and water quality were examined bi-weekly from 17 April to 19 October 1998 in 11 northeastern Lake Michigan coastal lakes of similar origin but varied in trophic status and limnological condition. All lakes were within or adjacent to Sleeping Bear Dunes National Lakeshore, Michigan. Zooplankton (principally microcrustaceans and rotifers) from triplicate Wisconsin net (80 I?m) vertical tows taken at each lake's deepest location were analyzed. Oxygen-temperature-pH-specific conductivity profiles and surface water quality were concurrently measured. Bray-Curtis similarity analysis showed small variations among sample replicates but large temporal differences. The potential use of zooplankton communities for environmental lake comparisons was evaluated by means of BIOENV (Primer 5.1) and principal component analyses. Zooplankton analyzed at the lowest identified taxonomic level yielded greatest sensitivity to limnological variation. Taxonomic and ecological aggregations of zooplankton data performed comparably, but less well than the finest taxonomic analysis. Secchi depth, chlorophyll a, and sulfate concentrations combined to give the best correlation with patterns of variation in the zooplankton data set. Principal component analysis of these variables revealed trophic status as the most influential major limnological gradient among the study lakes. Overall, zooplankton abundance was an excellent indicator of variation in trophic status.

  10. Zooplankton intermittency and turbulence

    NASA Astrophysics Data System (ADS)

    Schmitt, François G.

    2010-05-01

    Planktonic organisms usually live in a turbulent world. Since marine turbulence is characterized by very high Reynolds numbers, it possesses very intermittent fluctuations which in turn affect marine life. We consider here such influence on zooplankton on 2 aspects. First we consider zooplankton motion in the lab. Many copepods display swimming abilities. More and more species have been recently recorded using normal or high speed cameras, and many trajectories have been extracted from these movies and are now available for analysis. These trajectories can be complex, stochastic, with random switching from low velocity to high velocity events and even jumps. These complex trajectories show that an adequate modeling is necessary to understand and characterize them. Here we review the results published in the literature on copepod trajectories. We discuss the random walk, Levy walk modeling and introduce also multifractal random walks. We discuss the way to discriminate between these different walks using experimental data. Stochastic simulations will be performed to illustrate the different families. Second, we consider zooplankton contact rates in the framework of intermittent turbulence. Intermittency may have influence on plankton contact rates. We consider the Particle Stokes number of copepods, in a intermediate dissipation range affected by intermittent fluctuations. We show that they may display preferential concentration effects, and we consider the influence on contact rates of this effect in the intermediate dissipation range.

  11. Spatial and geographical changes in the mesozooplankton community in the Bering and Chukchi Seas during the summers of 2007 and 2008

    NASA Astrophysics Data System (ADS)

    Matsuno, Kohei; Landeira Sanchez, Jose M.; Yamaguchi, Atsushi; Hirawake, Toru; Kikuchi, Takashi

    2016-09-01

    From July to August 2007 and June to July 2008, the horizontal/geographical changes in the zooplankton community in the Bering and Chukchi Seas were studied. The geographical patterns, which were common for these two years, were observed for salinity, chlorophyll a (Chl. a), zooplankton chaetognaths, hydrozoans and the whole zooplankton community. Among them, the patterns of salinity and Chl. a were related with the horizontal distribution of the water masses. The distributions of the two carnivorous taxa were correlated with their prey (copepods or barnacle larvae). The analysis of the structural equation model (SEM) revealed that the horizontal distribution of the zooplankton abundance and biomass were governed by the different taxa. Thus, the zooplankton abundance was governed by the numerically dominant but smaller-bodied taxa, such as the barnacle larvae and copepod Pseudocalanus spp., while the zooplankton biomass was determined by the large-bodied copepods, such as Calanus glacialis/marshallae and Eucalanus bungii.

  12. Interannual abundance changes of gelatinous carnivore zooplankton unveil climate-driven hydrographic variations in the Iberian Peninsula, Portugal.

    PubMed

    D'Ambrosio, Mariaelena; Molinero, Juan C; Azeiteiro, Ulisses M; Pardal, Miguel A; Primo, Ana L; Nyitrai, Daniel; Marques, Sónia C

    2016-09-01

    The persistent massive blooms of gelatinous zooplankton recorded during recent decades may be indicative of marine ecosystem changes. In this study, we investigated the potential influence of the North Atlantic climate (NAO) variability on decadal abundance changes of gelatinous carnivore zooplankton in the Mondego estuary, Portugal, over the period 2003-2013. During the 11-year study, the community of gelatinous carnivores encompassed a larger diversity of hydromedusae than siphonophores; the former dominated by Obelia spp., Lizzia blondina, Clythia hemisphaerica, Liriope tetraphylla and Solmaris corona, while the latter dominated by Muggiaea atlantica. Gelatinous carnivore zooplankton displayed marked interannual variability and mounting species richness over the period examined. Their pattern of abundance shifted towards larger abundances ca. 2007 and significant phenological changes. The latter included a shift in the mean annual pattern (from unimodal to bimodal peak, prior and after 2007 respectively) and an earlier timing of the first annual peak concurrent with enhanced temperatures. These changes were concurrent with the climate-driven environmental variability mainly controlled by the NAO, which displayed larger variance after 2007 along with an enhanced upwelling activity. Structural equation modelling allowed depicting cascading effects derived from the NAO influence on regional climate and upwelling variability further shaping water temperature. Such cascading effect percolated the structure and dynamics of the community of gelatinous carnivore zooplankton in the Mondego estuary. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Mesozooplankton respiration and community structure in a seamount region of the eastern South Pacific

    NASA Astrophysics Data System (ADS)

    Frederick, Leissing; Escribano, Ruben; Morales, Carmen E.; Hormazabal, Samuel; Medellín-Mora, Johanna

    2018-05-01

    Seamounts in the Juan Fernandez Ridge, as well as in other seamount regions in the eastern South Pacific and in the world oceans, remain poorly studied ecosystems in terms of structure and functioning. Here, community respiration by epipelagic mesozooplankton in three seamounts of the Juan Fernandez Ridge, including the O`Higgins Seamount close to the coastal upwelling zone and two oceanic seamounts near the Juan Fernandez Archipelago ( 33°S-78°W), was assessed. Oxygen consumption by mixed assemblages was estimated using continuous measurements of dissolved oxygen concentration under controlled temperature during onboard, short-term incubations (2-4 h). Mesozooplankton composition was analyzed with a ZooScan device and expressed in terms of community normalized size spectra, and taxa and size diversity (Shannon-Wiener index). Carbon-specific community respiration rates in the upper 100 m layer were in the range of 0.3-1.9 mg O2 m-2 d-1, indicating that up to 3.1% of the mesozooplankton biomass can be respired on a daily basis. The mesozooplankton community was dominated by small-size copepods but the proportions of small copepods, large copepods, and gelatinous zooplankton (mostly salps) changed between the seamounts, in association with modifications in taxa composition, size diversity, and the slope of the size spectrum. Community respiration was significantly correlated to these community descriptors, suggesting the composition of the pelagic community has a direct impact on the total amount of respired-C. Connectivity between the coastal upwelling zone and the Juan Fernandez Ridge region mediated by mesoscale activity, interacting with the seamounts, is suggested as a most important process in controlling zooplankton community structure and in turn community metabolism.

  14. A comparison of mesopelagic mesozooplankton community structure in the subtropical and subarctic North Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Steinberg, Deborah K.; Cope, Joseph S.; Wilson, Stephanie E.; Kobari, T.

    2008-07-01

    Mesopelagic mesozooplankton communities of an oligotrophic (Hawaii Ocean Time series-HOT station ALOHA) and a mesotrophic (Japanese time-series station K2) environment in the North Pacific Ocean are compared as part of a research program investigating the factors that control the efficiency of particle export to the deep sea (VERtical Transport In the Global Ocean—VERTIGO). We analyzed zooplankton (>350 μm) collected from net tows taken between 0 and 1000 m at each site to investigate the biomass size structure and the abundance of the major taxonomic groups in discrete depth intervals throughout the water column. Biomass of zooplankton at K2 over all depths was approximately an order of a magnitude higher than at ALOHA, with a significantly higher proportion of the biomass at K2 in the larger (>2 mm) size classes. This difference was mostly due to the abundance at K2 of the large calanoid copepods Neocalanus spp. and Eucalanus bungii, which undergo ontogenetic (seasonal) vertical migration. The overall strength of diel vertical migration was higher at K2, with a mean night:day biomass ratio in the upper 150 m of 2.5, vs. a ratio of 1.7 at ALOHA. However, the amplitude of the diel migration (change in weighted mean depth between day and night) was higher at ALOHA for all biomass size classes, perhaps due to deeper light penetration causing deeper migration to avoid visual predators. A number of taxa known to feed on suspended or sinking detritus showed distinct peaks in the mesopelagic zone, which affects particle transport efficiency at both sites. These taxa include calanoid and poecilostomatoid (e.g., Oncaea spp.) copepods, salps, polychaetes, and phaeodarian radiolaria at K2, harpacticoid copepods at ALOHA, and ostracods at both sites. We found distinct layers of carnivores (mainly gelatinous zooplankton) in the mesopelagic at K2 including chaetognaths, hydrozoan medusae, polychaetes, and gymnosome pteropods, and, in the upper mesopelagic zone, of

  15. Seasonal dynamics of zooplankton in Columbia–Snake River reservoirs,with special emphasis on the invasive copepod Pseudodiaptomus forbesi

    Emerson, Joshua E.; Bollens, Stephen M.; Counihan, Timothy D.

    2015-01-01

    The Asian copepod Pseudodiaptomus forbesi has recently become established in the Columbia River. However, little is known about its ecology and effects on invaded ecosystems. We undertook a 2-year (July 2009 to June 2011) field study of the mesozooplankton in four reservoirs in the Columbia and Snake Rivers, with emphasis on the relation of the seasonal variation in distribution and abundance of P. forbesi to environmental variables. Pseudodiaptomus forbesi was abundant in three reservoirs; the zooplankton community of the fourth reservoir contained no known non-indigenous taxa. The composition and seasonal succession of zooplankton were similar in the three invaded reservoirs: a bloom of rotifers occurred in spring, native cyclopoid and cladoceran species peaked in abundance in summer, and P. forbesi was most abundant in late summer and autumn. In the uninvaded reservoir, total zooplankton abundance was very low year-round. Multivariate ordination indicated that temperature and dissolved oxygen were strongly associated with zooplankton community structure, with P. forbesi appearing to exhibit a single generation per year . The broad distribution and high abundance of P. forbesi in the Columbia–Snake River System could result in ecosystem level effects in areas intensively managed to improve conditions for salmon and other commercially and culturally important fish species. 

  16. Zooplankton Structure of the La Paz Bay southern Gulf of California and their Relation with the Hydrography during the summer 2004

    NASA Astrophysics Data System (ADS)

    Mojica-Ramirez, E.; Monreal-Gomez, M. A.; Salas-de-Leon, D. A.

    2007-05-01

    Physical and biological data were gathered in Bay of La Paz, Southern Gulf of California, in summer, 2004. These include hydrographical data, ADP currents, backscattering signals, in vivo natural fluorescence, as well as, zooplankton samples. The topography of the 15°C shows a dome in the central part of the bay that becomes deeper towards the periphery suggesting the existence of a cyclonic eddy. The 35 salinity topography shows an uplift of 35 m. The eddy has a north-south diameter of approximately 35 km and cover almost all the bay. The zooplankton samples reveal the existence of 23 groups the most abundant were cladocera, copepods, siphonophores, chaetognaths and larvae of crustaceans. The zooplankton biomass presents higher values in the periphery of the eddy indicating an influence of the cyclonic circulation in their distribution.

  17. Lessons learned from multifrequency acoustic studies of zooplankton and micronekton in the western Antarctic Peninsula and the Gulf of Maine

    NASA Astrophysics Data System (ADS)

    Lavery, Andone C.; Lawson, Gareth L.; Wiebe, Peter H.

    2005-09-01

    A series of acoustic surveys of zooplankton and micronekton have been performed in the Gulf of Maine (GOM), off the northeast United States, and along the western Antarctic Peninsula (WAP). Similar techniques were used to survey these regions, including multifrequency acoustic backscatter (43, 120, 200, 420, 1000 kHz), MOCNESS, CTD, VPR, and in some instances physical microstructure measurements. The GOM is characterized by heterogeneous zooplankton communities in which biomass is dominated by abundant millimeter sized copepods, but the scattering is frequently dominated by a smaller number of strong scatterers, such as shelled pteropods and gas-bearing siphonophores. Heterogeneous zooplankton communities are also observed in the WAP, but patches of comparatively large (40 mm) Antarctic krill are present and often dominate the scattering. In both regions, striking patterns are evident in the backscatter that can be related to the biological community structure and physical processes. Differences in community structure, however, strongly affect the quantitative inferences that can be made based on the acoustic data. Combining direct biological and environmental information with recently developed scattering models has allowed dominant scatterers to be identified and inferences to be made regarding the physical factors influencing backscatter variability, though only under limited conditions. Highlights from these studies and lessons learned regarding our ability to interpret multifrequency acoustics are presented.

  18. Bacterioplankton communities of Crater Lake, OR: Dynamic changes with euphotic zone food web structure and stable deep water populations

    Urbach, E.; Vergin, K.L.; Larson, G.L.; Giovannoni, S.J.

    2007-01-01

    The distribution of bacterial and archaeal species in Crater Lake plankton varies dramatically over depth and with time, as assessed by hybridization of group-specific oligonucleotides to RNA extracted from lakewater. Nonmetric, multidimensional scaling (MDS) analysis of relative bacterial phylotype densities revealed complex relationships among assemblages sampled from depth profiles in July, August and September of 1997 through 1999. CL500-11 green nonsulfur bacteria (Phylum Chloroflexi) and marine Group I crenarchaeota are consistently dominant groups in the oxygenated deep waters at 300 and 500 m. Other phylotypes found in the deep waters are similar to surface and mid-depth populations and vary with time. Euphotic zone assemblages are dominated either by ??-proteobacteria or CL120-10 verrucomicrobia, and ACK4 actinomycetes. MDS analyses of euphotic zone populations in relation to environmental variables and phytoplankton and zooplankton population structures reveal apparent links between Daphnia pulicaria zooplankton population densities and microbial community structure. These patterns may reflect food web interactions that link kokanee salmon population densities to community structure of the bacterioplankton, via fish predation on Daphnia with cascading consequences to Daphnia bacterivory and predation on bacterivorous protists. These results demonstrate a stable bottom-water microbial community. They also extend previous observations of food web-driven changes in euphotic zone bacterioplankton community structure to an oligotrophic setting. ?? 2007 Springer Science+Business Media B.V.

  19. Leveraging disjoint communities for detecting overlapping community structure

    NASA Astrophysics Data System (ADS)

    Chakraborty, Tanmoy

    2015-05-01

    Network communities represent mesoscopic structure for understanding the organization of real-world networks, where nodes often belong to multiple communities and form overlapping community structure in the network. Due to non-triviality in finding the exact boundary of such overlapping communities, this problem has become challenging, and therefore huge effort has been devoted to detect overlapping communities from the network. In this paper, we present PVOC (Permanence based Vertex-replication algorithm for Overlapping Community detection), a two-stage framework to detect overlapping community structure. We build on a novel observation that non-overlapping community structure detected by a standard disjoint community detection algorithm from a network has high resemblance with its actual overlapping community structure, except the overlapping part. Based on this observation, we posit that there is perhaps no need of building yet another overlapping community finding algorithm; but one can efficiently manipulate the output of any existing disjoint community finding algorithm to obtain the required overlapping structure. We propose a new post-processing technique that by combining with any existing disjoint community detection algorithm, can suitably process each vertex using a new vertex-based metric, called permanence, and thereby finds out overlapping candidates with their community memberships. Experimental results on both synthetic and large real-world networks show that PVOC significantly outperforms six state-of-the-art overlapping community detection algorithms in terms of high similarity of the output with the ground-truth structure. Thus our framework not only finds meaningful overlapping communities from the network, but also allows us to put an end to the constant effort of building yet another overlapping community detection algorithm.

  20. Selenium in San Francisco Bay zooplankton: Potential effects of hydrodynamics and food web interactions

    Purkerson, D.G.; Doblin, M.A.; Bollens, S.M.; Luoma, S.N.; Cutter, G.A.

    2003-01-01

    The potential toxicity of elevated selenium (Se) concentrations in aquatic ecosystems has stimulated efforts to measure Se concentrations in benthos, nekton, and waterfowl in San Francisco Bay (SF Bay). In September 1998, we initiated a 14 mo field study to determine the concentration of Se in SF Bay zooplankton, which play a major role in the Bay food web, but which have not previously been studied with respect to Se. Monthly vertical plankton tows were collected at several stations throughout SF Bay, and zooplankton were separated into two operationally defined size classes for Se analyses: 73-2,000 ??m, and ???2,000 ??m. Selenium values ranged 1.02-6.07 ??g Se g-1 dry weight. No spatial differences in zooplankton Se concentrations were found. However, there were inter- and intra-annual differences. Zooplankton Se concentrations were enriched in the North Bay in Fall 1999 when compared to other seasons and locations within and outside SF Bay. The abundance and biovolume of the zooplankton community varied spatially between stations, but not seasonally within each station. Smaller herbivorous-omnivorous zooplankton had higher Se concentrations than larger omnivorous-carnivorous zooplankton. Selenium concentrations in zooplankton were negatively correlated with the proportion of total copepod biovolume comprising the large carnivorous copepod Tortanus dextrilobatus, but positively correlated with the proportion of copepod biovolume comprising smaller copepods of the family Oithonidae, suggesting an important role of trophic level and size in regulating zooplankton Se concentrations.

  1. Discovering Network Structure Beyond Communities

    NASA Astrophysics Data System (ADS)

    Nishikawa, Takashi; Motter, Adilson E.

    2011-11-01

    To understand the formation, evolution, and function of complex systems, it is crucial to understand the internal organization of their interaction networks. Partly due to the impossibility of visualizing large complex networks, resolving network structure remains a challenging problem. Here we overcome this difficulty by combining the visual pattern recognition ability of humans with the high processing speed of computers to develop an exploratory method for discovering groups of nodes characterized by common network properties, including but not limited to communities of densely connected nodes. Without any prior information about the nature of the groups, the method simultaneously identifies the number of groups, the group assignment, and the properties that define these groups. The results of applying our method to real networks suggest the possibility that most group structures lurk undiscovered in the fast-growing inventory of social, biological, and technological networks of scientific interest.

  2. Zooplankton Responses to Low-Oxygen Condition upon a Shallow Oxygen Minimum Zone in the Upwelling Region off Chile

    NASA Astrophysics Data System (ADS)

    Hidalgo, P.; Escribano, R.

    2015-12-01

    A shallow oxygen minimum zone (OMZ) is a critical component in the coastal upwelling ecosystem off Chile. This OMZ causes oxygen-deficient water entering the photic layer and affecting plankton communities having low tolerance to hypoxia. Variable, and usually species-dependent, responses of zooplankton to hypoxia condition can be found. Most dominant species avoid hypoxia by restricting their vertical distribution, while others can temporarily enter and even spent part of their life cycle within the OMZ. Whatever the case, low-oxygen conditions appear to affect virtually all vital rates of zooplankton, such as mortality, fecundity, development and growth and metabolism, and early developmental stages seem more sensitive, with significant consequences for population and community dynamics. For most study cases, these effects are negative at individual and population levels. Observations and predictions upon increasing upwelling intensity over the last 20-30 years indicate a gradual shoaling of the OMZ, and so that an expected enhancement of these negative effects of hypoxia on the zooplankton community. Unknown processes of adaptation and community-structure adjustments are expected to take place with uncertain consequences for the food web of this highly productive eastern boundary current ecosystem.

  3. Mechanisms shaping size structure and functional diversity of phytoplankton communities in the ocean

    PubMed Central

    Acevedo-Trejos, Esteban; Brandt, Gunnar; Bruggeman, Jorn; Merico, Agostino

    2015-01-01

    The factors regulating phytoplankton community composition play a crucial role in structuring aquatic food webs. However, consensus is still lacking about the mechanisms underlying the observed biogeographical differences in cell size composition of phytoplankton communities. Here we use a trait-based model to disentangle these mechanisms in two contrasting regions of the Atlantic Ocean. In our model, the phytoplankton community can self-assemble based on a trade-off emerging from relationships between cell size and (1) nutrient uptake, (2) zooplankton grazing, and (3) phytoplankton sinking. Grazing ‘pushes’ the community towards larger cell sizes, whereas nutrient uptake and sinking ‘pull’ the community towards smaller cell sizes. We find that the stable environmental conditions of the tropics strongly balance these forces leading to persistently small cell sizes and reduced size diversity. In contrast, the seasonality of the temperate region causes the community to regularly reorganize via shifts in species composition and to exhibit, on average, bigger cell sizes and higher size diversity than in the tropics. Our results raise the importance of environmental variability as a key structuring mechanism of plankton communities in the ocean and call for a reassessment of the current understanding of phytoplankton diversity patterns across latitudinal gradients. PMID:25747280

  4. Significant Scales in Community Structure

    NASA Astrophysics Data System (ADS)

    Traag, V. A.; Krings, G.; van Dooren, P.

    2013-10-01

    Many complex networks show signs of modular structure, uncovered by community detection. Although many methods succeed in revealing various partitions, it remains difficult to detect at what scale some partition is significant. This problem shows foremost in multi-resolution methods. We here introduce an efficient method for scanning for resolutions in one such method. Additionally, we introduce the notion of ``significance'' of a partition, based on subgraph probabilities. Significance is independent of the exact method used, so could also be applied in other methods, and can be interpreted as the gain in encoding a graph by making use of a partition. Using significance, we can determine ``good'' resolution parameters, which we demonstrate on benchmark networks. Moreover, optimizing significance itself also shows excellent performance. We demonstrate our method on voting data from the European Parliament. Our analysis suggests the European Parliament has become increasingly ideologically divided and that nationality plays no role.

  5. Potential retention effect at fish farms boosts zooplankton abundance

    NASA Astrophysics Data System (ADS)

    Fernandez-Jover, D.; Toledo-Guedes, K.; Valero-Rodríguez, J. M.; Fernandez-Gonzalez, V.; Sanchez-Jerez, P.

    2016-11-01

    Coastal aquaculture activities influence wild macrofauna in natural environments due to the introduction of artificial structures, such as floating cages, that provide structural complexity in the pelagic system. This alters the abundance and distribution of the affected species and also their feeding behaviour and diet. Despite this, the effects of coastal aquaculture on zooplankton assemblages and the potential changes in their abundance and distribution remain largely unstudied. Traditional plankton sampling hauls between the farm mooring systems entail some practical difficulties. As an alternative, light traps were deployed at 2 farms in the SW Mediterranean during a whole warm season. Total zooplankton capture by traps at farms was higher than at control locations on every sampling night. It ranged from 3 to 10 times higher for the taxonomic groups: bivalvia, cladocera, cumacea, fish early-life-stages, gastropoda, polychaeta and tanaidacea; 10-20 times higher for amphipoda, chaetognatha, isopoda, mysidacea and ostracoda, and 22 times higher for copepoda and the crustacean juvenile stages zoea and megalopa. Permutational analysis showed significant differences for the most abundant zooplankton groups (copepoda, crustacean larvae, chaetognatha, cladocera, mysidacea and polychaeta). This marked incremental increase in zooplankton taxa at farms was consistent, irrespective of the changing environmental variables registered every night. Reasons for the greater abundance of zooplankton at farms are discussed, although results suggest a retention effect caused by cage structures rather than active attraction through physical or chemical cues.

  6. A compilation of quantitative functional traits for marine and freshwater crustacean zooplankton.

    PubMed

    Hébert, Marie-Pier; Beisner, Beatrix E; Maranger, Roxane

    2016-04-01

    This data compilation synthesizes 8609 individual observations and ranges of 13 traits from 201 freshwater and 191 marine crustacean taxa belonging to either Copepoda or Cladocera, two important zooplankton groups across all major aquatic habitats. Most data were gathered from the literature, with the balance being provided by zooplankton ecologists. With the aim of more fully assessing zooplankton effects on elemental processes such as nitrogen (N), phosphorus (P) and carbon (C) stocks and fluxes in aquatic ecosystems, this data set provides information on the following traits: body size (length and mass), trophic group, elemental and biochemical corporal composition (N, P, C, lipid and protein content), respiration rates, N- and P-excretion rates, as well as stoichiometric ratios. Although relationships for zooplankton metabolism as a function of body mass or requirements have been explored in the past three decades, data have not been systematically compiled nor examined from an integrative and large-scale perspective across crustacean taxa and habitat types. While this contribution likely represents the most comprehensive assembly of traits for both marine and freshwater species, this data set is not exhaustive either. As a result, this compilation also identifies knowledge gaps: a fact that should encourage researchers to disclose information they may have to help complete such databases. This trait matrix is made available for the first time in this data paper; prior to its release, the data set has been analyzed in a meta-analysis published as a companion paper. This data set should prove extremely valuable for aquatic ecologists for trait-based characterization of plankton community structure as well as biogeochemical modeling. These data are also well-suited for deriving shortcut relationships that predict more difficult to measure trait values, most of which can be directly related to ecosystem properties (i.e., effect traits), from simpler traits (e

  7. Prey-driven control of predator assemblages: zooplankton abundance drives aquatic beetle colonization.

    PubMed

    Pintar, Matthew R; Resetarits, William J

    2017-08-01

    Trophic interactions are critical determinants of community structure and ecosystem function. In freshwater habitats, top predators are traditionally viewed as drivers of ecosystem structure, shaping populations of consumers and primary producers. The temporary nature of small water bodies makes them dependent on colonization by many organisms, particularly insects that form highly diverse predator assemblages. We conducted mesocosm experiments with naturally colonizing populations of aquatic beetles to assess how prey (zooplankton) abundances influenced colonization and assemblages of natural populations of aquatic beetles. We experimentally demonstrate that zooplankton populations can be proximate regulators of predator populations and assemblages via prey-density-dependent predator recruitment. Our results provide support for the importance of prey populations in structuring predator populations and the role of habitat selection in structuring communities. We indicate that traditional views of predators as drivers of ecosystem structure in many systems may not provide a comprehensive picture, particularly in the context of highly disturbed or ephemeral habitats. © 2017 by the Ecological Society of America.

  8. Factors driving the seasonal distribution of zooplankton in a eutrophicated Mediterranean Lagoon.

    PubMed

    Ziadi, Boutheina; Dhib, Amel; Turki, Souad; Aleya, Lotfi

    2015-08-15

    The distribution of the zooplankton community was studied along with environmental factors at five sampling stations in Ghar El Melh Lagoon (GML) (Mediterranean Sea, northern Tunisia). GML is characterized by specific following properties: broad and shallow, freshwater supply (Station 1); connection to the sea (S2); stagnation (S3 especially), and eutrophic conditions with enhanced nutrient concentrations (S4 and S5). Samples were taken twice monthly from February 2011 to January 2012. Twenty-three zooplankton groups comprising 10 larval stages were identified. Zooplankton assemblages were largely dominated by copepods (37.25%), followed respectively by ciliates (21.09%), bivalve larvae (14.88%) and gastropod veligers (12.53%). Redundancy analysis indicated that while no significant difference was found in the distribution of zooplankton at any station, a strong difference was observed according to season. Both temporal and physicochemical fluctuations explain more than 50% of changes in zooplankton abundances. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Epidemics in adaptive networks with community structure

    NASA Astrophysics Data System (ADS)

    Shaw, Leah; Tunc, Ilker

    2010-03-01

    Models for epidemic spread on static social networks do not account for changes in individuals' social interactions. Recent studies of adaptive networks have modeled avoidance behavior, as non-infected individuals try to avoid contact with infectives. Such models have not generally included realistic social structure. Here we study epidemic spread on an adaptive network with community structure. We model the effect of heterogeneous communities on infection levels and epidemic extinction. We also show how an epidemic can alter the community structure.

  10. Retention and characteristics of microplastics in natural zooplankton taxa from the East China Sea.

    PubMed

    Sun, Xiaoxia; Liu, Tao; Zhu, Mingliang; Liang, Junhua; Zhao, Yongfang; Zhang, Bo

    2018-05-30

    The ubiquitous presence and persistence of microplastics (MPs) in aquatic environments have become of particular concern in recent years. Biological interactions are among the key processes that affect the impact and fate of MPs in the oceans. Zooplankton is one of the most sensitive taxa because their prey is approximately the same size as MPs. However, the status of MPs in zooplankton within natural marine environments remains largely unknown. By focusing on zooplankton in the East China Sea, the characteristics, bioaccumulated concentration, and retention of MPs for 10 zooplankton groups were systematically studied. Three types of MPs were found in zooplankton: fibres, pellets, and fragments. The fibres (54.6%) were more common than the other two types. The average lengths of the fibres, pellets, and fragments were 295.2 ± 348.6 μm, 20.3 ± 11.0 μm, and 82.4 ± 80.5 μm, respectively. Nineteen polymers were detected in the zooplankton via the Thermo Scientific Nicolet iN10 Infrared Microscope. Polymerized oxidized organic material and polyester were dominant, accounting for 35.9% and 25.6% of the polymers, respectively. The bioaccumulated concentration of MPs in the 10 zooplankton taxa varied from 0.13 pieces/zooplankton for Copepoda to 0.35 pieces/zooplankton for Pteropoda. The bioaccumulated concentration was negatively correlated with the abundance of zooplankton, showing a significant biological dilution effect. The bioaccumulated concentration was also influenced by the feeding mode of zooplankton, showing a trend of omnivorous > carnivorous > herbivorous. High retention of MPs was found in the zooplankton community of the East China Sea, achieving 19.7 ± 22.4 pieces/m 3 . This is much higher than the MP retention in zooplankton from other reported sea areas. By revealing the characteristics and retention of MPs in the natural zooplankton taxa from the East China Sea, this research identified the influence that MPs have

  11. Changes in fecal pellet characteristics with depth as indicators of zooplankton repackaging of particles in the mesopelagic zone of the subtropical and subarctic North Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Wilson, Stephanie E.; Steinberg, Deborah K.; Buesseler, Ken O.

    2008-07-01

    We investigated how fecal pellet characteristics change with depth in order to quantify the extent of particle repackaging by mesopelagic zooplankton in two contrasting open-ocean systems. Material from neutrally buoyant sediment traps deployed in the summer of 2004 and 2005 at 150, 300, and 500 m was analyzed from both a mesotrophic (Japanese time-series station K2) and an oligotrophic (Hawaii Ocean Time series—HOT station ALOHA) environment in the Pacific Ocean as part of the VERtical Transport In the Global Ocean (VERTIGO) project. We quantified changes in the flux, size, shape, and color of particles recognizable as zooplankton fecal pellets to determine how these parameters varied with depth and location. Flux of K2 fecal pellet particulate organic carbon (POC) at 150 and 300 m was four to five times higher than at ALOHA, and at all depths, fecal pellets were two to five times larger at K2, reflective of the disparate zooplankton community structure at the two sites. At K2, the proportion of POC flux that consisted of fecal pellets generally decreased with depth from 20% at 150 m to 5% at 500 m, whereas at ALOHA this proportion increased with depth (and was more variable) from 14% to 35%. This difference in the fecal fraction of POC with increasing depth is hypothesized to be due to differences in the extent of zooplankton-mediated fragmentation (coprohexy) and in zooplankton community structure between the two locations. Both regions provided indications of sinking particle repackaging and zooplankton carnivory in the mesopelagic. At ALOHA, this was reflected in a significant increase in the mean flux of larvacean fecal pellets from 150 to 500 m of 3-46 μg C m -2 d -1, respectively, and at K2 a large peak in larvacean mean pellet flux at 300 m of 3.1 mg C m -2 d -1. Peaks in red pellets produced by carnivores occurred at 300 m at K2, and a variety of other fecal pellet classes showed significant changes in their distribution with depth. There was also

  12. High mortality of Red Sea zooplankton under ambient solar radiation.

    PubMed

    Al-Aidaroos, Ali M; El-Sherbiny, Mohsen M O; Satheesh, Sathianeson; Mantha, Gopikrishna; Agustī, Susana; Carreja, Beatriz; Duarte, Carlos M

    2014-01-01

    High solar radiation along with extreme transparency leads to high penetration of solar radiation in the Red Sea, potentially harmful to biota inhabiting the upper water column, including zooplankton. Here we show, based on experimental assessments of solar radiation dose-mortality curves on eight common taxa, the mortality of zooplankton in the oligotrophic waters of the Red Sea to increase steeply with ambient levels of solar radiation in the Red Sea. Responses curves linking solar radiation doses with zooplankton mortality were evaluated by exposing organisms, enclosed in quartz bottles, allowing all the wavelengths of solar radiation to penetrate, to five different levels of ambient solar radiation (100%, 21.6%, 7.2%, 3.2% and 0% of solar radiation). The maximum mortality rates under ambient solar radiation levels averaged (±standard error of the mean, SEM) 18.4±5.8% h(-1), five-fold greater than the average mortality in the dark for the eight taxa tested. The UV-B radiation required for mortality rates to reach ½ of maximum values averaged (±SEM) 12±5.6 h(-1)% of incident UVB radiation, equivalent to the UV-B dose at 19.2±2.7 m depth in open coastal Red Sea waters. These results confirm that Red Sea zooplankton are highly vulnerable to ambient solar radiation, as a consequence of the combination of high incident radiation and high water transparency allowing deep penetration of damaging UV-B radiation. These results provide evidence of the significance of ambient solar radiation levels as a stressor of marine zooplankton communities in tropical, oligotrophic waters. Because the oligotrophic ocean extends across 70% of the ocean surface, solar radiation can be a globally-significant stressor for the ocean ecosystem, by constraining zooplankton use of the upper levels of the water column and, therefore, the efficiency of food transfer up the food web in the oligotrophic ocean.

  13. Strategies of zooplanktivory shape the dynamics and diversity of littoral plankton communities: a mesocosm approach

    PubMed Central

    Helenius, Laura K; Aymà Padrós, Anna; Leskinen, Elina; Lehtonen, Hannu; Nurminen, Leena

    2015-01-01

    Planktivorous fish can exert strong top-down control on zooplankton communities. By incorporating different feeding strategies, from selective particulate feeding to cruising filter feeding, fish species target distinct prey. In this study, we investigated the effects of two species with different feeding strategies, the three-spined stickleback (Gasterosteus aculeatus (L.)) and roach (Rutilus rutilus (L.)), on a low-diversity brackish water zooplankton community using a 16-day mesocosm experiment. The experiment was conducted on a small-bodied spring zooplankton community in high-nutrient conditions, as well as a large-bodied summer community in low-nutrient conditions. Effects were highly dependent on the initial zooplankton community structure and hence seasonal variation. In a small-bodied community with high predation pressure and no dispersal or migration, the selective particulate-feeding stickleback depleted the zooplankton community and decreased its diversity more radically than the cruising filter-feeding roach. Cladocerans rather than copepods were efficiently removed by predation, and their removal caused altered patterns in rotifer abundance. In a large-bodied summer community with initial high taxonomic and functional diversity, predation pressure was lower and resource availability was high for omnivorous crustaceans preying on other zooplankton. In this community, predation maintained diversity, regardless of predator species. During both experimental periods, predation influenced the competitive relationship between the dominant calanoid copepods, and altered species composition and size structure of the zooplankton community. Changes also occurred to an extent at the level of nontarget prey, such as microzooplankton and rotifers, emphasizing the importance of subtle predation effects. We discuss our results in the context of the adaptive foraging mechanism and relate them to the natural littoral community. PMID:26045953

  14. Tripartite community structure in social bookmarking data

    NASA Astrophysics Data System (ADS)

    Neubauer, Nicolas; Obermayer, Klaus

    2011-12-01

    Community detection is a branch of network analysis concerned with identifying strongly connected subnetworks. Social bookmarking sites aggregate datasets of often hundreds of millions of triples (document, user, and tag), which, when interpreted as edges of a graph, give rise to special networks called 3-partite, 3-uniform hypergraphs. We identify challenges and opportunities of generalizing community detection and in particular modularity optimization to these structures. Two methods for community detection are introduced that preserve the hypergraph's special structure to different degrees. Their performance is compared on synthetic datasets, showing the benefits of structure preservation. Furthermore, a tool for interactive exploration of the community detection results is introduced and applied to examples from real datasets. We find additional evidence for the importance of structure preservation and, more generally, demonstrate how tripartite community detection can help understand the structure of social bookmarking data.

  15. A meta-analysis of zooplankton functional traits influencing ecosystem function.

    PubMed

    Hébert, Marie-Pier; Beisner, Beatrix E; Maranger, Roxane

    2016-04-01

    The use of functional traits to characterize community composition has been proposed as a more effective way to link community structure to ecosystem functioning. Organismal morphology, body stoichiometry, and physiology can be readily linked to large-scale ecosystem processes through functional traits that inform on interspecific and species-environment interactions; yet such effect traits are still poorly included in trait-based approaches. Given their key trophic position in aquatic ecosystems, individual zooplankton affect energy fluxes and elemental processing. We compiled a large database of zooplankton traits contributing to carbon, nitrogen, and phosphorus cycling and examined the effect of classification and habitat (marine vs. freshwater) on trait relationships. Respiration and nutrient excretion rates followed mass-dependent scaling in both habitats, with exponents ranging from 0.70 to 0.90. Our analyses revealed surprising differences in allometry and respiration between habitats, with freshwater species having lower length-specific mass and three times higher mass-specific respiration rates. These differences in traits point to implications for ecological strategies as well as overall carbon storage and fluxes based on habitat type. Our synthesis quantifies multiple trait relationships and links organisms to ecosystem processes they influence, enabling a more complete integration of aquatic community ecology and biogeochemistry through the promising use of effect traits.

  16. Nutrient supply, surface currents, and plankton dynamics predict zooplankton hotspots in coastal upwelling systems

    NASA Astrophysics Data System (ADS)

    Messié, Monique; Chavez, Francisco P.

    2017-09-01

    A simple combination of wind-driven nutrient upwelling, surface currents, and plankton growth/grazing equations generates zooplankton patchiness and hotspots in coastal upwelling regions. Starting with an initial input of nitrate from coastal upwelling, growth and grazing equations evolve phytoplankton and zooplankton over time and space following surface currents. The model simulates the transition from coastal (large phytoplankton, e.g., diatoms) to offshore (picophytoplankton and microzooplankton) communities, and in between generates a large zooplankton maximum. The method was applied to four major upwelling systems (California, Peru, Northwest Africa, and Benguela) using latitudinal estimates of wind-driven nitrate supply and satellite-based surface currents. The resulting zooplankton simulations are patchy in nature; areas of high concentrations coincide with previously documented copepod and krill hotspots. The exercise highlights the importance of the upwelling process and surface currents in shaping plankton communities.

  17. Social significance of community structure: Statistical view

    NASA Astrophysics Data System (ADS)

    Li, Hui-Jia; Daniels, Jasmine J.

    2015-01-01

    Community structure analysis is a powerful tool for social networks that can simplify their topological and functional analysis considerably. However, since community detection methods have random factors and real social networks obtained from complex systems always contain error edges, evaluating the significance of a partitioned community structure is an urgent and important question. In this paper, integrating the specific characteristics of real society, we present a framework to analyze the significance of a social community. The dynamics of social interactions are modeled by identifying social leaders and corresponding hierarchical structures. Instead of a direct comparison with the average outcome of a random model, we compute the similarity of a given node with the leader by the number of common neighbors. To determine the membership vector, an efficient community detection algorithm is proposed based on the position of the nodes and their corresponding leaders. Then, using a log-likelihood score, the tightness of the community can be derived. Based on the distribution of community tightness, we establish a connection between p -value theory and network analysis, and then we obtain a significance measure of statistical form . Finally, the framework is applied to both benchmark networks and real social networks. Experimental results show that our work can be used in many fields, such as determining the optimal number of communities, analyzing the social significance of a given community, comparing the performance among various algorithms, etc.

  18. Effects of increased zooplankton biomass on phytoplankton and cyanotoxins: A tropical mesocosm study.

    PubMed

    Dos Santos Severiano, Juliana; Dos Santos Almeida-Melo, Viviane Lúcia; Bittencourt-Oliveira, Maria do Carmo; Chia, Mathias Ahii; do Nascimento Moura, Ariadne

    2018-01-01

    Zooplankton are important biocontrol agents for algal blooms in temperate lakes, while their potential in tropical and subtropical environments is not well understood. The aim of the present study was to evaluate the influence of increased zooplankton biomass on phytoplankton community and cyanotoxins (microcystins and saxitoxin) content of a tropical reservoir (Ipojuca reservoir, Brazil) using in situ mesocosms. Mesocosms consisted of 50L transparent polyethylene bags suspended in the reservoir for twelve days. Phytoplankton populations were exposed to treatments having 1 (control), 2, 3 and 4 times the biomass of zooplankton found in the reservoir at the beginning of the experiment. Filamentous cyanobacteria such as Planktothrix agardhii and Cylindrospermopsis raciborskii were not negatively influenced by increasing zooplankton biomass. In contrast, the treatments with 3 and 4 times zooplankton biomass negatively affected the cyanobacteria Aphanocapsa sp., Chroococcus sp., Dolichospermum sp., Merismopedia tenuissima, Microcystis aeruginosa and Pseudanabaena sp.; the diatom Cyclotella meneghiniana; and the cryptophyte Cryptomonas sp. Total microcystin concentration both increased and decreased at different times depending on zooplankton treatment, while saxitoxin level was not significantly different between the treatments and control. The results of the present study suggest that zooplankton biomass can be manipulated to control the excessive proliferation of non-filamentous bloom forming cyanobacteria (e.g. M. aeruginosa) and their associated cyanotoxins. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Afforestation alters community structure of soil fungi.

    PubMed

    Carson, Jennifer K; Gleeson, Deirdre B; Clipson, Nicholas; Murphy, Daniel V

    2010-07-01

    Relatively little is known about the effect of afforestation on soil fungal communities. This study demonstrated that afforestation altered fungal community structure and that changes were correlated to pools of soil C. Pasture at three locations on the same soil type was afforested with Eucalyptus globulus or Pinus pinaster. The structure of fungal communities under the three land uses was measured after 13y using automated ribosomal intergenic spacer analysis (ARISA). Afforestation significantly altered the structure of fungal communities. The effect of location on the structure of fungal communities was limited to pasture soils; although these contained the same plant species, the relative composition of each species varied between locations. Differences in the structure of fungal communities between pasture, E. globulus and P. pinaster were significantly correlated with changes in the amount of total organic C and microbial biomass-C in soil. Afforestation of patches of agricultural land may contribute to conserving soil fungi in agricultural landscapes by supporting fungal communities with different composition to agricultural soils. Copyright © 2010 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.

  20. Protocol for Automated Zooplankton Analysis

    DTIC Science & Technology

    2010-01-01

    on maximum dimension on the smallest axis: organisms > 50 microns (urn) (nominally zooplankton), organisms > 10 um to < 50 um (nominally protists ...viability of protists . Recent work has focused on performing measurements at a variety of geographic locations to demonstrate that these stains...provide a location-independent means to identify viable protists in test samples. NRL recommends staining samples with a combination of two vital stains

  1. Metacommunity ecology meets biogeography: effects of geographical region, spatial dynamics and environmental filtering on community structure in aquatic organisms.

    PubMed

    Heino, Jani; Soininen, Janne; Alahuhta, Janne; Lappalainen, Jyrki; Virtanen, Risto

    2017-01-01

    Metacommunity patterns and underlying processes in aquatic organisms have typically been studied within a drainage basin. We examined variation in the composition of six freshwater organismal groups across various drainage basins in Finland. We first modelled spatial structures within each drainage basin using Moran eigenvector maps. Second, we partitioned variation in community structure among three groups of predictors using constrained ordination: (1) local environmental variables, (2) spatial variables, and (3) dummy variable drainage basin identity. Third, we examined turnover and nestedness components of multiple-site beta diversity, and tested the best fit patterns of our datasets using the "elements of metacommunity structure" analysis. Our results showed that basin identity and local environmental variables were significant predictors of community structure, whereas within-basin spatial effects were typically negligible. In half of the organismal groups (diatoms, bryophytes, zooplankton), basin identity was a slightly better predictor of community structure than local environmental variables, whereas the opposite was true for the remaining three organismal groups (insects, macrophytes, fish). Both pure basin and local environmental fractions were, however, significant after accounting for the effects of the other predictor variable sets. All organismal groups exhibited high levels of beta diversity, which was mostly attributable to the turnover component. Our results showed consistent Clementsian-type metacommunity structures, suggesting that subgroups of species responded similarly to environmental factors or drainage basin limits. We conclude that aquatic communities across large scales are mostly determined by environmental and basin effects, which leads to high beta diversity and prevalence of Clementsian community types.

  2. Predator personality structures prey communities and trophic cascades.

    PubMed

    Start, Denon; Gilbert, Benjamin

    2017-03-01

    Intraspecific variation is central to our understanding of evolution and population ecology, yet its consequences for community ecology are poorly understood. Animal personality - consistent individual differences in suites of behaviours - may be particularly important for trophic dynamics, where predator personality can determine activity rates and patterns of attack. We used mesocosms with aquatic food webs in which the top predator (dragonfly nymphs) varied in activity and subsequent attack rates on zooplankton, and tested the effects of predator personality. We found support for four hypotheses: (1) active predators disproportionately reduce the abundance of prey, (2) active predators select for predator-resistant prey species, (3) active predators strengthen trophic cascades (increase phytoplankton abundance) and (4) active predators are more likely to cannibalise one another, weakening all other trends when at high densities. These results suggest that intraspecific variation in predator personality is an important determinant of prey abundance, community composition and trophic cascades. © 2017 John Wiley & Sons Ltd/CNRS.

  3. Temporal variations of water quality and the taxonomic structures of phytoplankton and zooplankton assemblages in mountain lakes, Mount Rainier National Park, Washington USA

    Larson, Gary L.; McIntire, C.D.; Jacobs, Ruth W.; Truitt, R.

    1999-01-01

    A synoptic inventory of physical and chemical properties and plankton assemblages of 27 mountain lakes was conducted at Mount Rainier National Park in 1988. From 1990–1993, die opportunity was presented to resurvey six of these lakes to determine inter-annual change within die set of characteristics surveyed in 1988. If changes were evident, a second objective was to provide guidance to park management about the value of a long-term lake monitoring program.Secchi-disk clarity, water temperature, and pH of the lakes in 1988 were within the range of values obtained between 1990 and 1993. Conductivities and concentration of nutrients in some lakes were not consistent in 1990–1993 with the values recorded in 1988. Although the dominant phytoplankton taxa in die lakes varied among years, die taxa in individual lakes were in consistent among years, with die exception of two lakes. Rotifer assemblages were consistent among years, but most of die lakes exhibited dramatic changes in some years, as did crustacean zooplankton assemblages. Suggestions were made about die need for a long-term monitoring program to evaluate die status and trends of park lakes.

  4. Zooplankton responses to increasing sea surface temperatures in the southeastern Australia global marine hotspot

    NASA Astrophysics Data System (ADS)

    Kelly, Paige; Clementson, Lesley; Davies, Claire; Corney, Stuart; Swadling, Kerrie

    2016-10-01

    Southeastern Australia is a 'hotspot' for oceanographic change. Here, rapidly increasing sea surface temperatures, rising at more than double the global trend, are largely associated with a southerly extension of the East Australian Current (EAC) and its eddy field. Maria Island, situated at the southern end of the EAC extension at 42°S, 148°E, has been used as a site to study temperature-driven biological trends in this region of accelerated change. Zooplankton have short life cycles (usually < 1 year) and are highly sensitive to environmental change, making them an ideal indicator of the biological effects of an increased southward flow of the EAC. Data from in-situ net drops and the Continuous Plankton Recorder (CPR), collected since 2009, together with historical zooplankton abundance data, have been analysed in this study. Like the North Atlantic, zooplankton communities of southeastern Australia are responding to increased temperatures through relocation, long-term increases in warm-water species and a shift towards a zooplankton community dominated by small copepods. The biological trends present evidence of extended EAC influence at Maria Island into autumn and winter months, which has allowed for the rapid establishment of warm-water species during these seasons, and has increased the similarity between Maria Island and the more northerly Port Hacking zooplankton community. Generalised Linear Models (GLM) suggest the high salinity and low nutrient properties of EAC-water to be the primary drivers of increasing abundances of warm-water species off southeastern Australia. Changes in both the species composition and size distribution of the Maria Island zooplankton community will have effects for pelagic fisheries. This study provides an indication of how zooplankton communities influenced by intensifying Western Boundary currents may respond to rapid environmental change.

  5. Network community structure and loop coefficient method

    NASA Astrophysics Data System (ADS)

    Vragović, I.; Louis, E.

    2006-07-01

    A modular structure, in which groups of tightly connected nodes could be resolved as separate entities, is a property that can be found in many complex networks. In this paper, we propose a algorithm for identifying communities in networks. It is based on a local measure, so-called loop coefficient that is a generalization of the clustering coefficient. Nodes with a large loop coefficient tend to be core inner community nodes, while other vertices are usually peripheral sites at the borders of communities. Our method gives satisfactory results for both artificial and real-world graphs, if they have a relatively pronounced modular structure. This type of algorithm could open a way of interpreting the role of nodes in communities in terms of the local loop coefficient, and could be used as a complement to other methods.

  6. The effects of juvenile American shad planktivory on zooplankton production in Columbia River food webs

    Haskell, Craig A.; Tiffan, Kenneth F.; Rondorf, Dennis W.

    2013-01-01

    Columbia River reservoirs support a large population of nonnative American Shad Alosa sapidissima that consume the zooplankton that native fishes also rely on. We hypothesized that the unprecedented biomass of juvenile American Shad in John Day Reservoir is capable of altering the zooplankton community if these fish consume a large portion of the zooplankton production. We derived taxon-specific estimates of zooplankton production using field data and a production model from the literature. Empirical daily ration was estimated for American Shad and expanded to population-level consumption using abundance and biomass data from hydroacoustic surveys. Daphnia spp. production was high in early summer but declined to near zero by September as shad abundance increased. American Shad sequentially consumed Daphnia spp., copepods, and Bosmina spp., which tracked the production trends of these taxa. American Shad evacuation rates ranged from 0.09 to 0.24/h, and daily rations ranged from 0.008 to 0.045 g·g−1·d−1 (dry weight) over all years. We observed peak American Shad biomass (45.2 kg/ha) in 1994, and daily consumption (1.6 kg/ha) approached 30% (5.3 kg/ha) of zooplankton production. On average, American Shad consumed 23.6% of the available zooplankton production (range, <1–83%). The changes in the zooplankton community are consistent with a top-down effect of planktivory by American Shad associated with their unprecedented biomass and consumption, but the effects are likely constrained by temperature, nutrient flux, and the seasonal production patterns of zooplankton in John Day Reservoir. American Shad add to the planktivory exerted by other species like Neomysis mercedis to reduce the capacity of the reservoir to support other planktivorous fishes. The introduction of American Shad and other nonnative species will continue to alter the food web in John Day Reservoir, potentially affecting native fishes, including Pacific salmon Oncorhynchus spp.

  7. Soil shapes community structure through fire.

    PubMed

    Ojeda, Fernando; Pausas, Juli G; Verdú, Miguel

    2010-07-01

    Recurrent wildfires constitute a major selecting force in shaping the structure of plant communities. At the regional scale, fire favours phenotypic and phylogenetic clustering in Mediterranean woody plant communities. Nevertheless, the incidence of fire within a fire-prone region may present strong variations at the local, landscape scale. This study tests the prediction that woody communities on acid, nutrient-poor soils should exhibit more pronounced phenotypic and phylogenetic clustering patterns than woody communities on fertile soils, as a consequence of their higher flammability and, hence, presumably higher propensity to recurrent fire. Results confirm the predictions and show that habitat filtering driven by fire may be detected even in local communities from an already fire-filtered regional flora. They also provide a new perspective from which to consider a preponderant role of fire as a key evolutionary force in acid, infertile Mediterranean heathlands.

  8. Lack of congruence in species diversity indices and community structures of planktonic groups based on local environmental factors.

    PubMed

    Doi, Hideyuki; Chang, Kwang-Hyeon; Nishibe, Yuichiro; Imai, Hiroyuki; Nakano, Shin-ichi

    2013-01-01

    The importance of analyzing the determinants of biodiversity and community composition by using multiple trophic levels is well recognized; however, relevant data are lacking. In the present study, we investigated variations in species diversity indices and community structures of the plankton taxonomic groups-zooplankton, rotifers, ciliates, and phytoplankton-under a range of local environmental factors in pond ecosystems. For each planktonic group, we estimated the species diversity index by using linear models and analyzed the community structure by using canonical correspondence analysis. We showed that the species diversity indices and community structures varied among the planktonic groups and according to local environmental factors. The observed lack of congruence among the planktonic groups may have been caused by niche competition between groups with similar trophic guilds or by weak trophic interactions. Our findings highlight the difficulty of predicting total biodiversity within a system, based upon a single taxonomic group. Thus, to conserve the biodiversity of an ecosystem, it is crucial to consider variations in species diversity indices and community structures of different taxonomic groups, under a range of local conditions.

  9. Environmental Regulation of Microbial Community Structure

    NASA Technical Reports Server (NTRS)

    Bebout, Leslie; DesMarais, D.; Heyenga, G.; Nelson, F.; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    Most naturally occurring microbes live in complex microbial communities consisting of thousands of phylotypes of microorganisms living in close proximity. Each of these draws nutrients from the environment and releases metabolic waste products, which may in turn serve as substrates for other microbial groups. Gross environmental changes, such as irradiance level, hydrodynamic flow regime, temperature or water chemistry can directly affect the productivity of some community members, which in turn will affect other dependent microbial populations and rate processes. As a first step towards the development of "standard" natural communities of microorganisms for a variety of potential NASA applications, we are measuring biogeochemical cycling in artificially structured communities of microorganisms, created using natural microbial mat communities as inoculum. The responses of these artificially assembled communities of microorganisms to controlled shifts in ecosystem incubation conditions is being determined. This research requires close linking of environmental monitoring, with community composition in a closed and controlled incubation setting. We are developing new incubation chamber designs to allow for this integrated approach to examine the interplay between environmental conditions, microbial community composition and biogeochemical processes.

  10. Steryl chlorin esters are formed by zooplankton herbivory

    NASA Astrophysics Data System (ADS)

    Harradine, Paul J.; Harris, Philip G.; Head, Robert N.; Harris, Roger P.; Maxwell, James R.

    1996-06-01

    Steryl chlorin esters (SCEs) were formed in laboratory feeding experiments when starved females of the copepod Calanus helgolandicus were allowed to graze on a culture of the diatom Thalassiosira weissflogii. They were found when the zooplankton had grazed for 48 hours and were also identified in fecal pellets subsequently left in seawater in the dark. The distribution contained the diatom sterols in approximately the same relative abundance as the free sterols in the substrate, as well as the most abundant copepod sterol, all esterified to the chlorophyll a degradation product, pyropheophorbide a. Hence, in studies aimed at using sedimentary SCE sterol distributions as indicators of phytoplankton community structure, cholesterol should not be considered since the cholesteryl ester of pyropheophorbide a was a significant component in the fecal pellet SCEs. The findings represent a step forward in unravelling the transformations undergone by chlorophyll a in aquatic environments, since the abundance and wide occurrence of sedimentary SCEs indicate that they are a significant preservational sink for the chlorophyll a biosynthesised in the photic zone.

  11. Microscale nutrient patches produced by zooplankton

    PubMed Central

    Lehman, John T.; Scavia, Donald

    1982-01-01

    Both track autoradiography and grain-density autoradiography show that individual zooplankton create miniature patches of dissolved nutrients and that algae exploit those regions to absorb phosphate. The patches are short lived and can be dispersed artificially by small-scale turbulence. Our data support a simple model of encounters between algae and nutrient plumes produced by swimming zooplankton. PMID:16593218

  12. Acoustic Scattering Models of Zooplankton and Microstructure

    DTIC Science & Technology

    1997-09-30

    shelled (gastropods), and gas-bearing ( siphonophores )). 5) LABORATORY EXPERIMENTATION: ZOOPLANKTON. An extensive set of laboratory measurements on the...zooplankton ( siphonophores and pteropods) that have high enough target strengths and occur in sufficiently high numbers that they could interfere with

  13. Acoustic Scattering Models of Zooplankton and Microstructures

    DTIC Science & Technology

    1998-09-30

    scattering by the seafloor. SCATTERING BY GAS-BEARING ZOOPLANKTON. In earlier work we showed that the scattering by gas-bearing zooplankton ( siphonophores ... siphonophores and pteropods) that have high enough target strengths and occur in sufficiently high numbers that they could interfere with the performance of

  14. Zooplankton trophic niches respond to different water types of the western Tasman Sea: A stable isotope analysis

    NASA Astrophysics Data System (ADS)

    Henschke, Natasha; Everett, Jason D.; Suthers, Iain M.; Smith, James A.; Hunt, Brian P. V.; Doblin, Martina A.; Taylor, Matthew D.

    2015-10-01

    The trophic relationships of 21 species from an oceanic zooplankton community were studied using stable isotopes of carbon and nitrogen. Zooplankton and suspended particulate organic matter (POM) were sampled in three different water types in the western Tasman Sea: inner shelf (IS), a cold core eddy (CCE) and a warm core eddy (WCE). δ15N values ranged from 3.9‰ for the parasitic copepod Sapphirina augusta to 10.2‰ for the euphausiid, Euphausia spinifera. δ13C varied from -22.6 to -19.4‰ as a result of the copepod Euchirella curticauda and E. spinifera. The isotopic composition of POM varied significantly among water types; as did the trophic enrichment of zooplankton over POM, with the lowest enrichment in the recently upwelled IS water type (0.5‰) compared to the warm core eddy (1.6‰) and cold core eddy (2.7‰). The WCE was an oligotrophic environment and was associated with an increased trophic level for omnivorous zooplankton (copepods and euphausiids) to a similar level as carnivorous zooplankton (chaetognaths). Therefore carnivory in zooplankton can increase in response to lower abundance and reduced diversity in their phytoplankton and protozoan prey. Trophic niche width comparisons across three zooplankton species: the salp Thalia democratica, the copepod Eucalanus elongatus and the euphausiid Thysanoessa gregaria, indicated that both niche partitioning and competition can occur within the zooplankton community. We have shown that trophic relationships among the zooplankton are dynamic and respond to different water types. The changes to the zooplankton isotopic niche, however, were still highly variable as result of oceanographic variation within water types.

  15. Ocean acidification reduces demersal zooplankton that reside in tropical coral reefs

    NASA Astrophysics Data System (ADS)

    Smith, Joy N.; de'Ath, Glenn; Richter, Claudio; Cornils, Astrid; Hall-Spencer, Jason M.; Fabricius, Katharina E.

    2016-12-01

    The in situ effects of ocean acidification on zooplankton communities remain largely unexplored. Using natural volcanic CO2 seep sites around tropical coral communities, we show a threefold reduction in the biomass of demersal zooplankton in high-CO2 sites compared with sites with ambient CO2. Differences were consistent across two reefs and three expeditions. Abundances were reduced in most taxonomic groups. There were no regime shifts in zooplankton community composition and no differences in fatty acid composition between CO2 levels, suggesting that ocean acidification affects the food quantity but not the quality for nocturnal plankton feeders. Emergence trap data show that the observed reduction in demersal plankton may be partly attributable to altered habitat. Ocean acidification changes coral community composition from branching to massive bouldering coral species, and our data suggest that bouldering corals represent inferior daytime shelter for demersal zooplankton. Since zooplankton represent a major source of nutrients for corals, fish and other planktivores, this ecological feedback may represent an additional mechanism of how coral reefs will be affected by ocean acidification.

  16. Diet compositions and trophic guild structure of the eastern Chukchi Sea demersal fish community

    NASA Astrophysics Data System (ADS)

    Whitehouse, George A.; Buckley, Troy W.; Danielson, Seth L.

    2017-01-01

    Fishes are an important link in Arctic marine food webs, connecting production of lower trophic levels to apex predators. We analyzed 1773 stomach samples from 39 fish species collected during a bottom trawl survey of the eastern Chukchi Sea in the summer of 2012. We used hierarchical cluster analysis of diet dissimilarities on 21 of the most well sampled species to identify four distinct trophic guilds: gammarid amphipod consumers, benthic invertebrate generalists, fish and shrimp consumers, and zooplankton consumers. The trophic guilds reflect dominant prey types in predator diets. We used constrained analysis of principal coordinates (CAP) to determine if variation within the composite guild diets could be explained by a suite of non-diet variables. All CAP models explained a significant proportion of the variance in the diet matrices, ranging from 7% to 25% of the total variation. Explanatory variables tested included latitude, longitude, predator length, depth, and water mass. These results indicate a trophic guild structure is present amongst the demersal fish community during summer in the eastern Chukchi Sea. Regular monitoring of the food habits of the demersal fish community will be required to improve our understanding of the spatial, temporal, and interannual variation in diet composition, and to improve our ability to identify and predict the impacts of climate change and commercial development on the structure and functioning of the Chukchi Sea ecosystem.

  17. Finding community structure in very large networks

    NASA Astrophysics Data System (ADS)

    Clauset, Aaron; Newman, M. E. J.; Moore, Cristopher

    2004-12-01

    The discovery and analysis of community structure in networks is a topic of considerable recent interest within the physics community, but most methods proposed so far are unsuitable for very large networks because of their computational cost. Here we present a hierarchical agglomeration algorithm for detecting community structure which is faster than many competing algorithms: its running time on a network with n vertices and m edges is O(mdlogn) where d is the depth of the dendrogram describing the community structure. Many real-world networks are sparse and hierarchical, with mtilde n and dtilde logn , in which case our algorithm runs in essentially linear time, O(nlog2n) . As an example of the application of this algorithm we use it to analyze a network of items for sale on the web site of a large on-line retailer, items in the network being linked if they are frequently purchased by the same buyer. The network has more than 400 000 vertices and 2×106 edges. We show that our algorithm can extract meaningful communities from this network, revealing large-scale patterns present in the purchasing habits of customers.

  18. Optimal community structure for social contagions

    NASA Astrophysics Data System (ADS)

    Su, Zhen; Wang, Wei; Li, Lixiang; Stanley, H. Eugene; Braunstein, Lidia A.

    2018-05-01

    Community structure is an important factor in the behavior of real-world networks because it strongly affects the stability and thus the phase transition order of the spreading dynamics. We here propose a reversible social contagion model of community networks that includes the factor of social reinforcement. In our model an individual adopts a social contagion when the number of received units of information exceeds its adoption threshold. We use mean-field approximation to describe our proposed model, and the results agree with numerical simulations. The numerical simulations and theoretical analyses both indicate that there is a first-order phase transition in the spreading dynamics, and that a hysteresis loop emerges in the system when there is a variety of initially adopted seeds. We find an optimal community structure that maximizes spreading dynamics. We also find a rich phase diagram with a triple point that separates the no-diffusion phase from the two diffusion phases.

  19. Emergence of structured communities through evolutionary dynamics.

    PubMed

    Shtilerman, Elad; Kessler, David A; Shnerb, Nadav M

    2015-10-21

    Species-rich communities, in which many competing species coexist in a single trophic level, are quite frequent in nature, but pose a formidable theoretical challenge. In particular, it is known that complex competitive systems become unstable and unfeasible when the number of species is large. Recently, many studies have attributed the stability of natural communities to the structure of the interspecific interaction network, yet the nature of such structures and the underlying mechanisms responsible for them remain open questions. Here we introduce an evolutionary model, based on the generic Lotka-Volterra competitive framework, from which a stable, structured, diverse community emerges spontaneously. The modular structure of the competition matrix reflects the phylogeny of the community, in agreement with the hierarchial taxonomic classification. Closely related species tend to have stronger niche overlap and weaker fitness differences, as opposed to pairs of species from different modules. The competitive-relatedness hypothesis and the idea of emergent neutrality are discussed in the context of this evolutionary model. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Zooplankton taxonomic and size diversity in Mediterranean coastal lagoons (NE Iberian Peninsula): Influence of hydrology, nutrient composition, food resource availability and predation

    NASA Astrophysics Data System (ADS)

    Badosa, Anna; Boix, Dani; Brucet, Sandra; López-Flores, Rocío; Gascón, Stéphanie; Quintana, Xavier D.

    2007-01-01

    The influence of hydrology, nutrient composition, food resource availability and predation on zooplankton taxonomic and size diversity was analyzed in several shallow lagoons of a Mediterranean salt marsh (Baix Ter Wetlands, NE Iberian Peninsula). Taxonomic diversity correlated better with variables related to the trophic state, such as nutrient concentrations, whereas size diversity was more sensitive to fish predation. However, the fish predation influence on the size diversity was only significant when fishes reached high densities. Under low fish densities no predation effects were observed and the food resource availability (FR a) appeared to be more important in structuring the zooplankton community. Nevertheless, the two diversity indexes showed opposite responses to this factor. With increasing FR a the taxonomic diversity increased and the size diversity decreased. Neither taxonomic nor size diversity of the zooplankton community correlated with other physical or biotic factors such as hydrological variability or macroinvertebrate predation. The relationships found suggest that the size diversity is mainly related to biotic interactions, such as fish predation or inter/intraspecific competition, while the taxonomic diversity appears to be more sensitive to abiotic factors such as the nutrient composition.

  1. Information transfer in community structured multiplex networks

    NASA Astrophysics Data System (ADS)

    Solé Ribalta, Albert; Granell, Clara; Gómez, Sergio; Arenas, Alex

    2015-08-01

    The study of complex networks that account for different types of interactions has become a subject of interest in the last few years, specially because its representational power in the description of users interactions in diverse online social platforms (Facebook, Twitter, Instagram, etc.). The mathematical description of these interacting networks has been coined under the name of multilayer networks, where each layer accounts for a type of interaction. It has been shown that diffusive processes on top of these networks present a phenomenology that cannot be explained by the naive superposition of single layer diffusive phenomena but require the whole structure of interconnected layers. Nevertheless, the description of diffusive phenomena on multilayer networks has obviated the fact that social networks have strong mesoscopic structure represented by different communities of individuals driven by common interests, or any other social aspect. In this work, we study the transfer of information in multilayer networks with community structure. The final goal is to understand and quantify, if the existence of well-defined community structure at the level of individual layers, together with the multilayer structure of the whole network, enhances or deteriorates the diffusion of packets of information.

  2. Feeding and production of zooplankton in the Catalan Sea (NW Mediterranean)

    NASA Astrophysics Data System (ADS)

    Saiz, Enric; Calbet, Albert; Atienza, Dacha; Alcaraz, Miquel

    2007-08-01

    Zooplankton are key components of the structure and functioning of marine planktonic food webs. They are the main link of planktonic primary production towards top pelagic consumer levels (fish), and play a relevant role on the nutrient recycling in the water column and on the export of particulate matter out of the photic zone. In this paper, we review the present knowledge on the feeding and production of zooplankton in the Catalan Sea (NW Mediterranean), with special emphasis on copepods. Feeding of zooplankton in the Catalan Sea appears typically food limited, with average daily rations on a yearly basis in the order of 48% body C d -1. Heterotrophic prey constitute a relevant fraction of their diet, as an alternative to the scarce phytoplankton in the area. From a structural point of view, the trophic impact and control of their prey populations are low on standing stocks but, at certain times, zooplankton can exert a meaningful effect on their prey production. Regarding zooplankton production, the available estimates of growth rates in the area are based on the egg production rate of copepods. Egg production rates appear to be limited, especially in summer. Tentative estimates of copepod production in the area are in the order of 20-40 mg C m -2 d -1. In conclusion, this review confirms that the oligotrophic character of the NW Mediterranean constrains the feeding activity and production of zooplankton.

  3. Changes in seasonal nearshore zooplankton abundance patterns in Lake Ontario following establishment of the exotic predator Cercopagis pengoi

    Warner, David M.; Rudstam, Lars G.; Benoit, Hugues; Mills, Edward L.; Johannsson, Ora E.

    2006-01-01

    Cercopagis pengoi, a zooplanktivore first discovered in Lake Ontario in 1998, may reduce availability of prey for planktivorous fish. Cercoapgis pengoi is most abundant in late summer and fall. Therefore, we hypothesized that abundance of small zooplankton (bosminids and cyclopoids) species would decrease at that time. To determine if the establishment of C. pengoi was followed by changes in the zooplankton community, seasonal patterns in nearshore zooplankton collected from May to October 1995–2000 were examined. Early summer density of small zooplankton was similar in all years while late summer and fall densities were significantly lower in 1998–2000 than in 1995–1997. The declines of small zooplankton coincided seasonally with the peak in C. pengoidensity. Other possible causes for the observed changes in small zooplankton are less likely. High levels of fish predation should have resulted in smaller zooplankton in 1998–2000 than in 1995–1997 and larger declines in Daphnia than other groups. This was not observed. There was no significant decline in chlorophyll-a concentrations or changes in temperature between 1995–1997 and 1998–2000. Therefore, the declines in density of small zooplankton were most likely the result of C. pengoi predation. The effect of C. pengoi establishment on alewives is increased competition for zooplankton prey but C. pengoi has replaced a portion of the zooplankton biomass and adult alewife diet formerly dominated by Diacyclops thomasi and Bosmina longirostris.

  4. Estimating Diversity of Florida Keys Zooplankton Using New Environmental DNA Methods

    NASA Astrophysics Data System (ADS)

    Djurhuus, A.; Goldsmith, D. B.; Sawaya, N. A.; Breitbart, M.

    2016-02-01

    Zooplankton are of great importance in marine food webs, where they serve to link the phytoplankton and bacteria with higher trophic levels. Zooplankton are a diverse group containing molluscs, crustaceans, fish larvae and many other taxa. The sheer number of species and often minor morphological distinctions between species makes it challenging and exceptionally time consuming to identify the species composition of marine zooplankton samples. As a part of the Marine Biodiversity Observation Network (MBON) project, we have developed and groundtruthed an alternative, relatively time-efficient method for zooplankton identification using environmental DNA (eDNA). Samples were collected from Molasses reef, Looe Key, and Western Sambo along the Florida Keys from five bi-monthly cruises on board the RV Walton Smith. Samples were collected for environmental DNA (eDNA) by filtering 1 L of water on to a 0.22 µm filter and zooplankton samples were collected using nets with three mesh sizes (64μm, 200μm, and 500μm) to catch different size fractions. Half of zooplankton samples were fixed in 70% ethanol and half in 10% formalin, for DNA extraction and morphological identification, respectively. Individuals representing visually abundant taxa were picked into individual wells for PCR with universal 18S rRNA gene primers and subsequent sequencing to build a reference barcode database for zooplankton species commonly found in the study region. PCR and Illumina MiSeq next generation sequencing was applied to the eDNA extracted from the 0.22 μm filters and sequences were be compared to our local custom database as well as publicly available databases to determine zooplankton community composition. Finally, composition and diversity analyses were performed to compare results obtained with the new eDNA approach to standard morphological classification of zooplankton communities. Results show that the eDNA approach can enable the determination of zooplankton diversity through

  5. Meso-zooplankton abundance and spatial distribution off Lützow-Holm Bay during austral summer 2007-2008

    NASA Astrophysics Data System (ADS)

    Makabe, Ryosuke; Tanimura, Atsushi; Tamura, Takeshi; Hirano, Daisuke; Shimada, Keishi; Hashihama, Fuminori; Fukuchi, Mitsuo

    2017-06-01

    To elucidate spatial differences in mesozooplankton community structure in local scale, vertical hauls using a 60-μm mesh closing net were carried out off Lützow-Holm Bay in January 2008. All of the zooplankton samples collected from three layers (0-100, 100-200, and 200-500 m) at seven stations were dominated by Oithona spp., Oncaea spp., Ctenocalanus citer, Microcalanus pygmaeus, and copepod nauplii. The cluster analysis of mesozooplankton abundances showed three distinct groups according to sampling depth, which appeared to be due to the preferential vertical distribution of dominant copepods. The other cluster analysis on integrated abundance upper 500 m revealed that mesozooplankton community structures at stations located on the western and eastern edges of the observation area (Cluster A) differed from those at the central stations (Cluster B). Abundance of copepod nauplii, Oithona spp., and C. citer differed between Clusters A and B, which was likely caused by differences in recruitment and early development in the dominant copepods, being associated with the timing and duration of ice edge blooms. This suggests that such heterogeneity in abundance and recruitment/development of dominant taxa was likely caused by local heterogeneity in sea ice dynamics. This may affect our understanding of zooplankton distribution.

  6. Persistence of an unusual pelagic zooplankton assemblage in a clear, mountain lake

    Larson, G.L.; Hoffman, R.L.; C. David, McIntire

    2002-01-01

    The planktonic zooplankton assemblage in Mowich Lake, Mount Rainier National Park (MORA), was composed almost entirely of rotifers in 1966 and 1967. Adult pelagic crustacean taxa were rare. Their paucity was attributed to predation by kokanee salmon (Oncorhynchus nerka), which had been stocked in 1961. During a park-wide survey of 24 lakes in 1988, Mowich Lake was the only one that did not contain at least one planktonic crustacean species. Given the apparent persistence of the unusual pelagic zooplankton assemblage in Mowich Lake, the first objective of this study was to document the interannual variation in the taxonomic structure of the zooplankton assemblages in the lake from 1988 through 1999. A second objective was to determine if it was possible to predict the taxonomic composition of the pelagic crustacean zooplankton assemblage in Mowich Lake prior to the stocking of kokanee salmon. The Mowich Lake zooplankton assemblages in 1988-1999 were consistent with those in 1966 and 1967. Crustacean taxa were extremely rare, but they included most of the primary taxa collected from 23 MORA lakes surveyed in 1988. Nonetheless, the 1988 collections showed that the September rotifer assemblage in Mowich Lake was similar to 10 of the 24 lakes sampled. Seven of the 10 lakes were dominated by cladocerans, primarily Daphnia rosea and Holopedium gibberum. Therefore, it appeared that either one or both of these species may have numerically dominated the crustacean zooplankton assemblage in the lake prior to 1961.

  7. Zooplankton assemblages in montane lakes and ponds of Mount Rainier National Park, Washington State, USA

    Larson, G.L.; Hoffman, R.; McIntire, C.D.; Lienkaemper, G.; Samora, B.

    2009-01-01

    Water quality and zooplankton samples were collected during the ice-free periods between 1988 and 2005 from 103 oligotrophic montane lakes and ponds located in low forest to alpine vegetation zones in Mount Rainier National Park, Washington State, USA. Collectively, 45 rotifer and 44 crustacean taxa were identified. Most of the numerically dominant taxa appeared to have wide niche breadths. The average number of taxa per lake decreased with elevation and generally increased as maximum lake depths increased (especially for rotifers). With one exception, fish presence/absence did not explain the taxonomic compositions of crustacean zooplankton assemblages. Many rotifer species were common members of zooplankton assemblages in montane lakes and ponds in western North America, whereas the crustacean taxa were common to some areas of the west, but not others. Constraints of the environmental variables did not appear to provide strong gradients to separate the distributions of most zooplankton species. This suggests that interspecific competitive interactions and stochastic processes regulate the taxonomic structures of the zooplankton assemblages at the landscape level. Crustacean species that had broad niche breadths were associated with different rotifer taxa across the environmental gradients. Studies of zooplankton assemblages need to address both crustacean and rotifer taxa, not one or the other.

  8. Persistence of an unusual pelagic zooplankton assemblage in a clear mountain lake

    Larson, Gary L.; Hoffman, Robert L.; McIntire, C.D.

    2002-01-01

    The planktonic zooplankton assemblage in Mowich Lake, Mount Rainier National Park (MORA), was composed almost entirely of rotifers in 1966 and 1967. Adult pelagic crustacean taxa were rare. Their paucity was attributed to predation by kokanee salmon (Oncorhynchus nerka), which had been stocked in 1961. During a park-wide survey of 24 lakes in 1988, Mowich Lake was the only one that did not contain at least one planktonic crustacean species. Given the apparent persistence of the unusual pelagic zooplankton assemblage in Mowich Lake, the first objective of this study was to document the interannual variation in the taxonomic structure of the zooplankton assemblages in the lake from 1988 through 1999. A second objective was to determine if it was possible to predict the taxonomic composition of the pelagic crustacean zooplankton assemblage in Mowich Lake prior to the stocking of kokanee salmon. The Mowich Lake zooplankton assemblages in 1988a??1999 were consistent with those in 1966 and 1967. Crustacean taxa were extremely rare, but they included most of the primary taxa collected from 23 MORA lakes surveyed in 1988. Nonetheless, the 1988 collections showed that the September rotifer assemblage in Mowich Lake was similar to 10 of the 24 lakes sampled. Seven of the 10 lakes were dominated by cladocerans, primarily Daphnia rosea and Holopedium gibberum. Therefore, it appeared that either one or both of these species may have numerically dominated the crustacean zooplankton assemblage in the lake prior to 1961.

  9. Overheated and Out of Breath: Temperature Regulation of Respiration and Oxygen Supply in Coastal Zooplankton

    NASA Astrophysics Data System (ADS)

    Roman, M.; Elliott, D. T.; Pierson, J. J.

    2016-02-01

    Increasing global coastal hypoxia occurs under a large range of temperature and salinity conditions. Temperature directly influences oxygen solubility in seawater as well as the oxygen demand of zooplankton, thus oxygen concentration alone is not sufficient to categorize the biological impact of hypoxia for pelagic organisms. To effectively assess the impacts of hypoxic stress on zooplankton habitat space and production, it is necessary to consider the effects of temperature on both oxygen availability and zooplankton metabolism. Our analysis and modeling evaluate available oxygen (partial pressure and concentration) in the context of ambient temperature conditions and zooplankton oxygen demand. We will present allometric models, accounting for both body size and temperature that predict temperature-dependent oxygen supply and demand in coastal zooplankton. Our goal is to develop generalized, functional relationships that describe and quantify the interactive effects of temperature and low oxygen on coastal zooplankton that can lead to improved size-structured models that serve to predict impacts of increasing coastal hypoxia on pelagic food webs.

  10. Taxonomies of networks from community structure

    NASA Astrophysics Data System (ADS)

    Onnela, Jukka-Pekka; Fenn, Daniel J.; Reid, Stephen; Porter, Mason A.; Mucha, Peter J.; Fricker, Mark D.; Jones, Nick S.

    2012-09-01

    The study of networks has become a substantial interdisciplinary endeavor that encompasses myriad disciplines in the natural, social, and information sciences. Here we introduce a framework for constructing taxonomies of networks based on their structural similarities. These networks can arise from any of numerous sources: They can be empirical or synthetic, they can arise from multiple realizations of a single process (either empirical or synthetic), they can represent entirely different systems in different disciplines, etc. Because mesoscopic properties of networks are hypothesized to be important for network function, we base our comparisons on summaries of network community structures. Although we use a specific method for uncovering network communities, much of the introduced framework is independent of that choice. After introducing the framework, we apply it to construct a taxonomy for 746 networks and demonstrate that our approach usefully identifies similar networks. We also construct taxonomies within individual categories of networks, and we thereby expose nontrivial structure. For example, we create taxonomies for similarity networks constructed from both political voting data and financial data. We also construct network taxonomies to compare the social structures of 100 Facebook networks and the growth structures produced by different types of fungi.

  11. Taxonomies of networks from community structure

    PubMed Central

    Reid, Stephen; Porter, Mason A.; Mucha, Peter J.; Fricker, Mark D.; Jones, Nick S.

    2014-01-01

    The study of networks has become a substantial interdisciplinary endeavor that encompasses myriad disciplines in the natural, social, and information sciences. Here we introduce a framework for constructing taxonomies of networks based on their structural similarities. These networks can arise from any of numerous sources: they can be empirical or synthetic, they can arise from multiple realizations of a single process (either empirical or synthetic), they can represent entirely different systems in different disciplines, etc. Because mesoscopic properties of networks are hypothesized to be important for network function, we base our comparisons on summaries of network community structures. Although we use a specific method for uncovering network communities, much of the introduced framework is independent of that choice. After introducing the framework, we apply it to construct a taxonomy for 746 networks and demonstrate that our approach usefully identifies similar networks. We also construct taxonomies within individual categories of networks, and we thereby expose nontrivial structure. For example, we create taxonomies for similarity networks constructed from both political voting data and financial data. We also construct network taxonomies to compare the social structures of 100 Facebook networks and the growth structures produced by different types of fungi. PMID:23030977

  12. Contrasted structuring effects of mesoscale features on the seabird community in the Mozambique Channel

    NASA Astrophysics Data System (ADS)

    Jaquemet, S.; Ternon, J. F.; Kaehler, S.; Thiebot, J. B.; Dyer, B.; Bemanaja, E.; Marteau, C.; Le Corre, M.

    2014-02-01

    of mescoscale features in structuring the tropical seabird community in the Mozambique Channel, in addition to segregating tropical and non-tropical species. The mechanisms underlying the segregation of tropical seabirds seem to partially differ from that of other tropical regions, and this may be a consequence of the strong local mesoscale activity, affecting prey size and availability schemes. Beyond characterising the foraging habitats of the seabird community of the Mozambique Channel, this study highlights the importance of this region as a hot spot for seabirds; especially the southern part, where several endangered sub-Antarctic species over-winter.

  13. Regional and inter-annual variability in Atlantic zooplankton en route to the Arctic Ocean: potential effects of multi-path Atlantic water advection through Fram Strait and the Barents Sea

    NASA Astrophysics Data System (ADS)

    Kwasniewski, Slawomir; Gluchowska, Marta; Trudnowska, Emilia; Ormanczyk, Mateusz; Walczowski, Waldemar; Beszczynska-Moeller, Agnieszka

    2016-04-01

    The Arctic is among the regions where the climate change effects on ecosystem will be the most rapid and consequential, with Arctic amplification recognized as an integral part of the process. Great part of the changes are forced by advection of warm waters from the North Atlantic and the expected modifications of Arctic marine ecosystem will be induced not only by changing environmental conditions but also as a result of introducing Atlantic biota. Thus, the knowledge of physical and biological heterogeneity of Atlantic inflow is requisite for understanding the effects of climate change on biological diversity and ecosystem functioning in the Arctic. The complex and variable two-branched structure of the Atlantic Water flow via Fram Strait and the Barents Sea most likely has a strong influence on the ocean biology in these regions, especially in the pelagic realm. Zooplankton are key components of marine ecosystems which form essential links between primary producers and grazer/predator consumers, thus they are important for functioning of the biological carbon pump. Changes in zooplankton distribution and abundance may have cascading effects on ecosystem functioning, with regulatory effects on climate. Based on data collected in summers of 2012-2014, within the scope of the Polish-Norwegian PAVE research project, we investigate zooplankton distribution, abundance and selected structural characteristics of communities, in relation to water mass properties in the Atlantic Water complex flow to the Arctic Ocean. The main questions addressed here are: what are the differences in zooplankton patterns between the Fram Strait and Barents Sea branches, and how does the inter-annual variability of Atlantic Water advection relate to changes in zooplankton? The results of the investigation are precondition for foreseeing changes in the pelagic realm in the Arctic Ocean and are necessary for constructing and tuning plankton components of ecosystem models.

  14. Deep-water zooplankton in the Mediterranean Sea: Results from a continuous, synchronous sampling over different regions using sediment traps

    NASA Astrophysics Data System (ADS)

    Danovaro, R.; Carugati, L.; Boldrin, A.; Calafat, A.; Canals, M.; Fabres, J.; Finlay, K.; Heussner, S.; Miserocchi, S.; Sanchez-Vidal, A.

    2017-08-01

    Information on the dynamics of deep-sea biota is extremely scant particularly for long-term time series on deep-sea zooplankton. Here, we present the results of a deep-sea zooplankton investigation over one annual cycle based on samples from sediment trap moorings in three sub-basins along the Mediterranean Sea. Deep-sea zooplankton assemblages were dominated by copepods, as in shallow waters, only in the Adriatic Sea (>60% of total abundance), but not in the deep Ionian Sea, where ostracods represented >80%, neither in the deep Alboran Sea, where polychaetes were >70%. We found that deep-sea zooplankton assemblages: i) are subjected to changes in their abundance and structure over time, ii) are characterized by different dominant taxa in different basins, and iii) display clear taxonomic segregation between shallow and near-bottom waters. Zooplankton biodiversity decreases with increasing water depth, but the equitability increases. We suggest here that variations of zooplankton abundance and assemblage structure are likely influenced by the trophic condition characterizing the basins. Our findings provide new insights on this largely unknown component of the deep ocean, and suggest that changes in the export of organic matter from the photic zone, such as those expected as a consequence of global change, can significantly influence zooplankton assemblages in the largest biome on Earth.

  15. Epidemic spreading on complex networks with community structures

    PubMed Central

    Stegehuis, Clara; van der Hofstad, Remco; van Leeuwaarden, Johan S. H.

    2016-01-01

    Many real-world networks display a community structure. We study two random graph models that create a network with similar community structure as a given network. One model preserves the exact community structure of the original network, while the other model only preserves the set of communities and the vertex degrees. These models show that community structure is an important determinant of the behavior of percolation processes on networks, such as information diffusion or virus spreading: the community structure can both enforce as well as inhibit diffusion processes. Our models further show that it is the mesoscopic set of communities that matters. The exact internal structures of communities barely influence the behavior of percolation processes across networks. This insensitivity is likely due to the relative denseness of the communities. PMID:27440176

  16. A hybrid spectral representation of phytoplankton growth and zooplankton response: The ''control rod'' model of plankton interaction

    NASA Astrophysics Data System (ADS)

    Armstrong, Robert A.

    2003-11-01

    Phytoplankton species interact through competition for light and nutrients; they also interact through grazers they hold in common. Both interactions are expected to be size-dependent: smaller phytoplankton species will be at an advantage when nutrients are scarce due to surface/volume considerations, while species that are similar in size are more likely to be consumed by grazers held in common than are species that differ greatly in size. While phytoplankton competition for nutrients and light has been extensively characterized, size-based interaction through shared grazers has not been represented systematically. The latter situation is particularly unfortunate because small changes in community structure can give rise to large changes in ecosystem dynamics and, in inverse modeling, to large changes in estimated parameter values. A simple, systematic way to represent phytoplankton interaction through shared grazers, one resistant to unintended idiosyncrasy of model construction yet capable of representing scientifically justifiable idiosyncrasy, would aid greatly in the modeling process. Here I develop a model structure that allows systematic representation of plankton interaction. In this model, the zooplankton community is represented as a continuous size spectrum, while phytoplankton species can be represented individually. The mechanistic basis of the model is a shift in the zooplankton community from carnivory to omnivory to herbivory as phytoplankton density increases. I discuss two limiting approximations in some detail, and fit both to data from the IronEx II experiment. The first limiting case represents a community with no grazer-based interaction among phytoplankton species; this approximation illuminates the general structure of the model. In particular, the zooplankton spectrum can be viewed as the analog of a control rod in a nuclear reactor, which prevents (or fails to prevent) an exponential bloom of phytoplankton. A second, more complex limiting

  17. Phytoplankton Composition and Abundance in Restored Maltański Reservoir under the Influence of Physico-Chemical Variables and Zooplankton Grazing Pressure

    PubMed Central

    Kozak, Anna; Gołdyn, Ryszard; Dondajewska, Renata

    2015-01-01

    In this paper we present the effects of environmental factors and zooplankton food pressure on phytoplankton in the restored man-made Maltański Reservoir (MR). Two methods of restoration: biomanipulation and phosphorus inactivation have been applied in the reservoir. Nine taxonomical groups of phytoplankton represented in total by 183 taxa were stated there. The richest groups in respect of taxa number were green algae, cyanobacteria and diatoms. The diatoms, cryptophytes, chrysophytes, cyanobacteria, green algae and euglenophytes dominated in terms of abundance and/or biomass. There were significant changes among environmental parameters resulting from restoration measures which influenced the phytoplankton populations in the reservoir. These measures led to a decrease of phosphorus concentration due to its chemical inactivation and enhanced zooplankton grazing as a result of planktivorous fish stocking. The aim of the study is to analyse the reaction of phytoplankton to the restoration measures and, most importantly, to determine the extent to which the qualitative and quantitative composition of phytoplankton depends on variables changing under the influence of restoration in comparison with other environmental variables. We stated that application of restoration methods did cause significant changes in phytoplankton community structure. The abundance of most phytoplankton taxa was negatively correlated with large zooplankton filter feeders, and positively with zooplankton predators and concentrations of ammonium nitrogen and partly of phosphates. However, restoration was insufficient in the case of decreasing phytoplankton abundance. The effects of restoration treatments were of less importance for the abundance of phytoplankton than parameters that were independent of the restoration. This was due to the continuous inflow of large loads of nutrients from the area of the river catchment. PMID:25906352

  18. Phytoplankton Composition and Abundance in Restored Maltański Reservoir under the Influence of Physico-Chemical Variables and Zooplankton Grazing Pressure.

    PubMed

    Kozak, Anna; Gołdyn, Ryszard; Dondajewska, Renata

    2015-01-01

    In this paper we present the effects of environmental factors and zooplankton food pressure on phytoplankton in the restored man-made Maltański Reservoir (MR). Two methods of restoration: biomanipulation and phosphorus inactivation have been applied in the reservoir. Nine taxonomical groups of phytoplankton represented in total by 183 taxa were stated there. The richest groups in respect of taxa number were green algae, cyanobacteria and diatoms. The diatoms, cryptophytes, chrysophytes, cyanobacteria, green algae and euglenophytes dominated in terms of abundance and/or biomass. There were significant changes among environmental parameters resulting from restoration measures which influenced the phytoplankton populations in the reservoir. These measures led to a decrease of phosphorus concentration due to its chemical inactivation and enhanced zooplankton grazing as a result of planktivorous fish stocking. The aim of the study is to analyse the reaction of phytoplankton to the restoration measures and, most importantly, to determine the extent to which the qualitative and quantitative composition of phytoplankton depends on variables changing under the influence of restoration in comparison with other environmental variables. We stated that application of restoration methods did cause significant changes in phytoplankton community structure. The abundance of most phytoplankton taxa was negatively correlated with large zooplankton filter feeders, and positively with zooplankton predators and concentrations of ammonium nitrogen and partly of phosphates. However, restoration was insufficient in the case of decreasing phytoplankton abundance. The effects of restoration treatments were of less importance for the abundance of phytoplankton than parameters that were independent of the restoration. This was due to the continuous inflow of large loads of nutrients from the area of the river catchment.

  19. Structure of the pelagic cnidarian community in Lützow-Holm Bay in the Indian sector of the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Toda, R.; Moteki, M.; Ono, A.; Horimoto, N.; Tanaka, Y.; Ishimaru, T.

    2010-08-01

    The structure of the pelagic cnidarian community in Lützow-Holm Bay in the Indian sector of East Antarctica was investigated in January 2005 and 2006. Zooplankton samples from six discrete depths (surface to 2000 m) obtained using an RMT-8 yielded 4666 individuals of 31 species of cnidarian. Cnidarian abundance and carbon biomass were far greater in 2005 than in 2006. The biomass of macrozooplankton was large in the upper 200 m in 2005, but concentrated at 200-500 m in 2006, except for Euphausiacea. The most dominant species was Diphyes antarctica, followed by Dimophyes arctica and Muggiaea bargmannae. Four species had never been collected from East Antarctica; of these, Solmissus incisa was a first record in the Southern Ocean. Cluster analysis revealed the following three major communities: the epipelagic (0-200 m), in summer surface, winter, and upper modified circumpolar deep waters (MCDW); the upper mesopelagic (200-500 m), in upper MCDW; and the lower meso- and bathypelagic (500-2000 m), in lower MCDW. The epipelagic and lower meso- and bathypelagic communities are likely reduced in abundance/biomass when primary production is low, due to bottom-up control, while the upper mesopelagic community remains stable.

  20. Investigating long-term interactions between phytoplankton and zooplankton in the NE Atlantic and North Sea

    NASA Astrophysics Data System (ADS)

    Khouri, R.; Beaulieu, C.; Henson, S.; Martin, A. P.; Edwards, M.

    2016-02-01

    It is believed that changes in phytoplankton community have happened in the North Sea and NE Atlantic in the past decades. Since phytoplankton are the base of the marine food web, it is essential to understand the causes of such behaviour due its potential to induce change in the wider ecosystem. Whilst the impact of environmental controls, such as climate, have received considerable attention, phytoplankton can also be affected by zooplankton grazing. We investigate how changes in zooplankton impact phytoplankton populations and community composition, and vice-versa. We use data from the Continuous Plankton Recorder survey, an unique dataset that uses the same sampling methodology since 1958 and thus provides long and comparable plankton time-series. We apply statistical modelling to describe the interaction between phytoplankton and zooplankton. The analysis is inspired from techniques available in econometrics literature, which do not require assumptions of normality, independence or stationarity of the time-series. In particular, we discuss wether climatic factors or zooplankton grazing are more relevant to the variability in phytoplankton abundance and community composition.

  1. Mesozooplankton community structure and variability in the Scotia Sea: A seasonal comparison

    NASA Astrophysics Data System (ADS)

    Ward, Peter; Atkinson, Angus; Tarling, Geraint

    2012-01-01

    Mesozooplankton distribution and community structure was investigated during 3 cruises to the Scotia Sea in austral spring, summer and autumn. Three mesh sizes of Bongo nets were used during each cruise with a 53 μm mesh net yielding on average 1.76 times higher densities (median 923,000 ind. m -2, 0-400 m) than a 100 μm net and 7.42 times more than a 200 μm net across all cruises. Small copepods dominated numerically across all nets with Oithona spp., Oncaea spp., Ctenocalanus citer and Microcalanus pygmaeus being particularly abundant, with sample densities of up to 3.5×10 6 ind. m -2 recorded within the top 400 m. A more even distribution of biomass among net sizes was apparent, with median net ratios (1.15-1.25) smaller and more even than for abundance. To the south of the Scotia Sea plankton maxima occurred in autumn, consistent with a later spawning in many species, whereas further north, abundance in 53 and 100 μm nets varied little across seasons, although in the 200 μm net there was a clear summer maximum. Median biomass increased through summer and by autumn was twice than found during spring in all parts of the Scotia Sea. Cluster analysis indicated two main station groups in all 3 seasons. To the south of the Southern boundary of the ACC (SB-ACC), Group 1 contained stations, that lay within the seasonal sea-ice zone and where zooplankton abundance and biomass was persistently low. In contrast at Group 2 stations, north of the Southern Antarctic Circumpolar Current Front (SACCF) abundance and biomass was consistently higher. Differences between the two groups were largely apparent at the population rather than at the taxonomic level. LHPR hauls to 1000 m indicated that the large seasonal migrant copepods Calanoides acutus and Rhincalanus gigas were at a more advanced stage of development in the north in spring and summer where they were generally present in the upper water column. In autumn, at all stations, C. acutus was dominated by later stages

  2. Community Structure in Online Collegiate Social Networks

    NASA Astrophysics Data System (ADS)

    Traud, Amanda; Kelsic, Eric; Mucha, Peter; Porter, Mason

    2009-03-01

    Online social networking sites have become increasingly popular with college students. The networks we studied are defined through ``friendships'' indicated by Facebook users from UNC, Oklahoma, Caltech, Georgetown, and Princeton. We apply the tools of network science to study the Facebook networks from these five different universities at a single point in time. We investigate each single-institution network's community structure, which we obtain through partitioning the graph using an eigenvector method. We use both graphical and quantitative tools, including pair-counting methods, which we interpret through statistical analysis and permutation tests to measure the correlations between the network communities and a set of characteristics given by each user (residence, class year, major, and high school). We also analyze the single gender subsets of these networks, and the impact of missing demographical data. Our study allows us to compare the online social networks for the five schools as well as infer differences in offline social interactions. At the schools studied, we were able to define which characteristics of the Facebook users correlate best with friendships.

  3. Bipartite Community Structure of eQTLs.

    PubMed

    Platig, John; Castaldi, Peter J; DeMeo, Dawn; Quackenbush, John

    2016-09-01

    Genome Wide Association Studies (GWAS) and expression quantitative trait locus (eQTL) analyses have identified genetic associations with a wide range of human phenotypes. However, many of these variants have weak effects and understanding their combined effect remains a challenge. One hypothesis is that multiple SNPs interact in complex networks to influence functional processes that ultimately lead to complex phenotypes, including disease states. Here we present CONDOR, a method that represents both cis- and trans-acting SNPs and the genes with which they are associated as a bipartite graph and then uses the modular structure of that graph to place SNPs into a functional context. In applying CONDOR to eQTLs in chronic obstructive pulmonary disease (COPD), we found the global network "hub" SNPs were devoid of disease associations through GWAS. However, the network was organized into 52 communities of SNPs and genes, many of which were enriched for genes in specific functional classes. We identified local hubs within each community ("core SNPs") and these were enriched for GWAS SNPs for COPD and many other diseases. These results speak to our intuition: rather than single SNPs influencing single genes, we see groups of SNPs associated with the expression of families of functionally related genes and that disease SNPs are associated with the perturbation of those functions. These methods are not limited in their application to COPD and can be used in the analysis of a wide variety of disease processes and other phenotypic traits.

  4. Typology of State-Level Community College Governance Structures

    ERIC Educational Resources Information Center

    Fletcher, Jeffrey A.; Friedel, Janice Nahra

    2017-01-01

    Despite having a well-documented history about community colleges across the United States, relatively few discussions have covered state-level governance structures. To understand the typology of state community college governance structures, it must first be recognized that community college governance is characterized as a complex web of…

  5. A new modelling approach for zooplankton behaviour

    NASA Astrophysics Data System (ADS)

    Keiyu, A. Y.; Yamazaki, H.; Strickler, J. R.

    We have developed a new simulation technique to model zooplankton behaviour. The approach utilizes neither the conventional artificial intelligence nor neural network methods. We have designed an adaptive behaviour network, which is similar to BEER [(1990) Intelligence as an adaptive behaviour: an experiment in computational neuroethology, Academic Press], based on observational studies of zooplankton behaviour. The proposed method is compared with non- "intelligent" models—random walk and correlated walk models—as well as observed behaviour in a laboratory tank. Although the network is simple, the model exhibits rich behavioural patterns similar to live copepods.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  7. Dynamics and control of diseases in networks with community structure.

    PubMed

    Salathé, Marcel; Jones, James H

    2010-04-08

    The dynamics of infectious diseases spread via direct person-to-person transmission (such as influenza, smallpox, HIV/AIDS, etc.) depends on the underlying host contact network. Human contact networks exhibit strong community structure. Understanding how such community structure affects epidemics may provide insights for preventing the spread of disease between communities by changing the structure of the contact network through pharmaceutical or non-pharmaceutical interventions. We use empirical and simulated networks to investigate the spread of disease in networks with community structure. We find that community structure has a major impact on disease dynamics, and we show that in networks with strong community structure, immunization interventions targeted at individuals bridging communities are more effective than those simply targeting highly connected individuals. Because the structure of relevant contact networks is generally not known, and vaccine supply is often limited, there is great need for efficient vaccination algorithms that do not require full knowledge of the network. We developed an algorithm that acts only on locally available network information and is able to quickly identify targets for successful immunization intervention. The algorithm generally outperforms existing algorithms when vaccine supply is limited, particularly in networks with strong community structure. Understanding the spread of infectious diseases and designing optimal control strategies is a major goal of public health. Social networks show marked patterns of community structure, and our results, based on empirical and simulated data, demonstrate that community structure strongly affects disease dynamics. These results have implications for the design of control strategies.

  8. Community Structure and Vietnamese Refugee Adaptation: The Significance of Context.

    ERIC Educational Resources Information Center

    Starr, Paul D.; Roberts, Alden E.

    1982-01-01

    Describes research investigating the effects of community structure on the adjustment of Vietnamese refugees in America. Emphasizes how congruence between individual characteristics and characteristics of the receiving community determine successful refugee adaptation to a new environment. (MJL)

  9. Zooplankton variability in the subtropical estuarine system of Paranaguá Bay, Brazil, in 2012 and 2013

    NASA Astrophysics Data System (ADS)

    Salvador, Bianca; Bersano, José Guilherme F.

    2017-12-01

    Spatial and temporal dynamics of zooplankton assemblages were studied in the Paranaguá Estuarine System (southern Brazil), including data from the summer (rainy) and winter (dry) periods of 2012 and 2013. Zooplankton and environmental data were collected at 37 stations along the estuary and examined by multivariate methods. The results indicated significantly distinct assemblages; differences in abundance were the major source of variability, mainly over the temporal scale. The highest abundances were observed during rainy periods, especially in 2012, when the mean density reached 16378 ind.m-3. Winter assemblages showed lower densities but higher species diversity, due to the more extensive intrusion of coastal waters. Of the 14 taxonomic groups recorded, Copepoda was the most abundant and diverse (92% of total abundance and 22 species identified). The coastal copepods Acartia lilljeborgi (44%) and Oithona hebes (26%) were the most important species in both abundance and frequency, followed by the estuarine Pseudodiaptomus acutus and the neritic Temora turbinata. The results indicated strong influences of environmental parameters on the community structure, especially in response to seasonal variations. The spatial distribution of species was probably determined mainly by their preferences and tolerances for specific salinity conditions. On the other hand, the abundances were strongly related to higher water temperature and precipitation rates, which can drive nutrient inputs and consequently food supply in the system, due to intense continental drainage.

  10. The way to uncover community structure with core and diversity

    NASA Astrophysics Data System (ADS)

    Chang, Y. F.; Han, S. K.; Wang, X. D.

    2018-07-01

    Communities are ubiquitous in nature and society. Individuals that share common properties often self-organize to form communities. Avoiding the shortages of computation complexity, pre-given information and unstable results in different run, in this paper, we propose a simple and efficient method to deepen our understanding of the emergence and diversity of communities in complex systems. By introducing the rational random selection, our method reveals the hidden deterministic and normal diverse community states of community structure. To demonstrate this method, we test it with real-world systems. The results show that our method could not only detect community structure with high sensitivity and reliability, but also provide instructional information about the hidden deterministic community world and the real normal diverse community world by giving out the core-community, the real-community, the tide and the diversity. Thizs is of paramount importance in understanding, predicting, and controlling a variety of collective behaviors in complex systems.

  11. Community Attachment and Satisfaction: The Role of a Community's Social Network Structure

    ERIC Educational Resources Information Center

    Crowe, Jessica

    2010-01-01

    This paper links the micro and macro levels of analysis by examining how different aspects of community sentiment are affected by one's personal ties to the community compared with the organizational network structure of the community. Using data collected from residents of six communities in Washington State, network analysis combined with…

  12. Do intraspecific or interspecific interactions determine responses to predators feeding on a shared size-structured prey community?

    PubMed

    ten Brink, Hanna; Mazumdar, Abul Kalam Azad; Huddart, Joseph; Persson, Lennart; Cameron, Tom C

    2015-03-01

    Coexistence of predators that share the same prey is common. This is still the case in size-structured predator communities where predators consume prey species of different sizes (interspecific prey responses) or consume different size classes of the same species of prey (intraspecific prey responses). A mechanism has recently been proposed to explain coexistence between predators that differ in size but share the same prey species, emergent facilitation, which is dependent on strong intraspecific responses from one or more prey species. Under emergent facilitation, predators can depend on each other for invasion, persistence or success in a size-structured prey community. Experimental evidence for intraspecific size-structured responses in prey populations remains rare, and further questions remain about direct interactions between predators that could prevent or limit any positive effects between predators [e.g. intraguild predation (IGP)]. Here, we provide a community-wide experiment on emergent facilitation including natural predators. We investigate both the direct interactions between two predators that differ in body size (fish vs. invertebrate predator), and the indirect interaction between them via their shared prey community (zooplankton). Our evidence supports the most likely expectation of interactions between differently sized predators that IGP rates are high, and interspecific interactions in the shared prey community dominate the response to predation (i.e. predator-mediated competition). The question of whether emergent facilitation occurs frequently in nature requires more empirical and theoretical attention, specifically to address the likelihood that its pre-conditions may co-occur with high rates of IGP. © 2014 The Authors. Journal of Animal Ecology © 2014 British Ecological Society.

  13. Grazing experiments and model simulations of the role of zooplankton in Phaeocystis food webs

    NASA Astrophysics Data System (ADS)

    Verity, P. G.

    2000-08-01

    A combined empirical and modelling study was conducted to further examine the potential importance of grazing by zooplankton in pelagic food webs in which Phaeocystis is a significant or dominant component. Laboratory experiments were designed to measure ingestion of Phaeocystis and other potential prey items which co-occur with Phaeocystis. Grazers included copepods and ciliates, and prey included Phaeocystis colonies and solitary cells, diatoms, ciliates, bacteria, and detritus. These data were expressed in the model currency of nitrogen units, and fit to hyperbolic tangent equations which included minimum prey thresholds. These equations and literature data were used to constrain a food web model whose purpose was to investigate trophic interactions rather than to mimic actual events. Nevertheless, the model output was similar to the general pattern and magnitude of development of Phaeocystis-diatom communities in some environments where they occur, e.g. north Norwegian waters. The model included three forms of nitrogen, three phytoplankton groups, bacteria, two zooplankton groups, and detritus, with detailed flows between compartments. An important component of the model was inclusion of variable prey preferences for zooplankton. The experiments and model simulations suggest several salient conclusions. Phaeocystis globosa colonies were eaten by a medium-sized copepod species, but ingestion appeared to be strongly dependent upon a proper size match between grazer and prey. If not, colonies were eaten little if at all. Phaeocystis solitary cells were ingested rapidly by ciliate microzooplankton, in agreement with prior literature observations. In contrast, detritus was eaten comparatively slowly by both ciliates and copepods. Both types of zooplankton exhibited apparent minimum prey thresholds below which grazing did not occur or was inconsequential. Model simulations implied that transitions between life cycle stages of Phaeocystis may potentially be important

  14. Zooplankton diel vertical migration and contribution to deep active carbon flux in the NW Mediterranean

    NASA Astrophysics Data System (ADS)

    Isla, Alejandro; Scharek, Renate; Latasa, Mikel

    2015-03-01

    The diel vertical migration (DVM) of zooplankton contributes to the biological pump transporting material from surface to deep waters. We examined the DVM of the zooplankton community in different size fractions (53-200 μm, 200-500 μm, 500-1000 μm, 1000-2000 μm and > 2000 μm) during three cruises carried out in the open NW Mediterranean Sea. We assessed their metabolic rates from empirical published relationships and estimated the active fluxes of dissolved carbon to the mesopelagic zone driven by migrant zooplankton. Within the predominantly oligotrophic Mediterranean Sea, the NW region is one of the most productive ones, with a seasonal cycle characterized by a prominent spring bloom. The study area was visited at three different phases of the seasonal cycle: during the spring bloom, the post-bloom, and strongly stratified oligotrophic conditions. We found seasonal differences in DVM, less evident during the bloom. Changes in DVM intensity were related to the composition of the zooplanktonic assemblage, which also varied between cruises. Euphausiids appeared as the most active migrants in all seasons, and their life cycle conditioned the observed pattern. Immature stages, which are unable to perform large diel vertical movements, dominated during the bloom, in contrast to the higher relative importance of migrating adults in the other two sampling periods. The amount of dissolved carbon exported was determined by the migrant zooplankton biomass, being highest during the post-bloom (2.2 mmol C respired m- 2 d- 1, and up to 3.1 mmol C exported m- 2 d- 1 when DOC release estimations are added). The active transport by diel migrants represented a substantial contribution to total carbon export to deep waters, especially under stratified oligotrophic conditions, revealing the importance of zooplankton in the biological pump operating in the study area.

  15. Moonlight Drives Ocean-Scale Mass Vertical Migration of Zooplankton during the Arctic Winter.

    PubMed

    Last, Kim S; Hobbs, Laura; Berge, Jørgen; Brierley, Andrew S; Cottier, Finlo

    2016-01-25

    In extreme high-latitude marine environments that are without solar illumination in winter, light-mediated patterns of biological migration have historically been considered non-existent [1]. However, diel vertical migration (DVM) of zooplankton has been shown to occur even during the darkest part of the polar night, when illumination levels are exceptionally low [2, 3]. This paradox is, as yet, unexplained. Here, we present evidence of an unexpected uniform behavior across the entire Arctic, in fjord, shelf, slope and open sea, where vertical migrations of zooplankton are driven by lunar illumination. A shift from solar-day (24-hr period) to lunar-day (24.8-hr period) vertical migration takes place in winter when the moon rises above the horizon. Further, mass sinking of zooplankton from the surface waters and accumulation at a depth of ∼50 m occurs every 29.5 days in winter, coincident with the periods of full moon. Moonlight may enable predation of zooplankton by carnivorous zooplankters, fish, and birds now known to feed during the polar night [4]. Although primary production is almost nil at this time, lunar vertical migration (LVM) may facilitate monthly pulses of carbon remineralization, as they occur continuously in illuminated mesopelagic systems [5], due to community respiration of carnivorous and detritivorous zooplankton. The extent of LVM during the winter suggests that the behavior is highly conserved and adaptive and therefore needs to be considered as "baseline" zooplankton activity in a changing Arctic ocean [6-9]. VIDEO ABSTRACT. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  16. Distinct zooplankton regime shift patterns across ecoregions of the U.S. Northeast continental shelf Large Marine Ecosystem

    NASA Astrophysics Data System (ADS)

    Morse, R. E.; Friedland, K. D.; Tommasi, D.; Stock, C.; Nye, J.

    2017-01-01

    We investigated regime shifts in seasonal zooplankton communities of the Northeast continental shelf Large Marine Ecosystem (NES) and its subcomponent ecoregions over a multi-decadal period (1977-2013). Our cross ecoregion analysis shows that regime shifts in different ecoregions often exhibited very distinct characteristics, emphasizing more granular fluctuations in NES plankton communities relative to previous work. Shifts early in the time series generally reflected an increase in abundance levels. The response of zooplankton abundance within fall communities was more similar among ecoregions than for spring communities. The Gulf of Maine exhibited highly distinct patterns from other ecoregions, with regime shifts identified in the early 1980s, early 2000s, and mid-2000s for spring communities. Regime shifts were identified in the early to mid-1990s for the NES, Georges Bank, and the Mid-Atlantic Bight ecoregions, while the fall communities experienced shifts in the early 1990s and late 1980s for the NES and Georges Bank, but in the late 1990s in the Mid-Atlantic Bight. A constrained correspondence analysis of zooplankton community against local and basin-scale climatological indices suggests that water temperature, stratification, and the Atlantic multidecadal oscillation (AMO) were the predominant factors in driving the zooplankton community composition.

  17. The seasonal succession of zooplankton in the Southern Ocean south of Australia, part II: The Sub-Antarctic to Polar Frontal Zones

    NASA Astrophysics Data System (ADS)

    Hunt, Brian P. V.; Hosie, Graham W.

    2006-07-01

    Between October 2001 and March 2002 six transects were completed at monthly intervals in the Sub-Antarctic Zone (SAZ) and Inter-Sub-Antarctic Front Zone (ISAFZ)/Polar Frontal Zone (PFZ) in the Southern Ocean south of Australia. Zooplankton were collected with a Continuous Plankton Recorder and NORPAC net and multivariate analysis was used to analyse the seasonal succession of communities. Despite strong, seasonally consistent, biogeographic differences between the SAZ and ISAFZ/PFZ, community structure in all zones was dominated by a suite of common taxa. These included the ubiquitous Oithona similis, foraminiferans and appendicularians (Core taxa), occurring in >97% of samples and contributing an average of 75% to total sample abundance, and Calanus simillimus, Rhincalanus gigas, Ctenocalanus citer, Clausocalanus brevipes, Clausocalanus laticeps, Oithona frigida, Limacina spp. and chaetognaths (Summer taxa), present in >57% of samples and occurring at seasonally high densities. Because of the dominance of the Core and Summer taxa, the seasonal succession was most clearly evident as a change in zooplankton densities. In October densities averaged <15 ind m -3, rising to 52 ind m -3 (max=92 ind m -3) in November, and subsequently increasing slowly through to January (ave=115 ind m -3; max=255 ind m -3). Densities peaked abruptly in February (ave=634 ind m -3; max=1593 ind m -3), and remained relatively high in March (ave=193 ind m -3; max=789 ind m -3). A latitudinal lag in seasonal development was observed with peak densities occurring first in the SAZ (February) and then in the ISAFZ/PFZ (March). The seasonal community succession was strongly influenced by species population cycles. The role of zooplankton in biogeochemical cycling in the SAZ and ISAFZ/PFZ was discussed in the light of past sediment trap data collected from the study area.

  18. A decade of predatory control of zooplankton species composition of Lake Michigan

    Makarewicz, Joseph C.; Bertram, Paul; Lewis, Theodore; Brown, Edward H.

    1995-01-01

    From 1983 to 1992, 71 species representing 38 genera from the Calanoida, Cladocera, Cyclopoida, Mysidacea, Rotifera, Mollusca and Harpacticoida comprised the offshore zooplankton community of Lake Michigan. Our data demonstrate that the composition and abundance of the calanoid community after 1983 is not unlike that of 1960s and that species diversity of the calanoid community is more diverse than the cladoceran community in the 1990s as compared to the early 1980s. Even though the relative biomass of the cladocerans has remained similar over the 1983-1993 period, the species diversity and evenness of the Cladocera community in the early 1990s is unlike anything that has been previously reported for Lake Michigan. Cladocera dominance is centered in one species, Daphnia galeata mendotae, and only three species of Cladocera were observed in the pelagic region of the lake in 1991 and 1992. Nutrient levels, phytoplankton biomass, and the abundance of planktivorous alewife and bloater chub and Bythotrephes are examined as possible causes of these changes in zooplankton species composition. The increase in Rotifera biomass, but not Crustacea, was correlated with an increase in relative biomass of unicellular algae. Food web models suggest Bythotrephes will cause Lake Michigan's plankton to return to a community similar to that of the 1970s; that is Diaptomus dominated. Such a change has occurred. However, correlational analysis suggest that alewife and bloater chubs (especially juveniles) are affecting size and biomass of larger species of zooplankton as well as Bythotrephes.

  19. Acoustic Scattering Classification of Zooplankton and Microstructure

    DTIC Science & Technology

    2001-09-30

    As part of this investigation, we have been observing concentrations of siphonulae, a larval form of the gas-bearing zooplankton siphonophore . The...situ measurements of acoustic target strengths of siphonophores , a gas-bearing zooplankter,” ICES J. Mar. Sci. 58: 740-749. Warren, J.D., T.K

  20. Zooplankton seasonality across a latitudinal gradient in the Northeast Atlantic Shelves Province

    NASA Astrophysics Data System (ADS)

    Fanjul, Alvaro; Iriarte, Arantza; Villate, Fernando; Uriarte, Ibon; Atkinson, Angus; Cook, Kathryn

    2018-05-01

    Zooplankton seasonality and its environmental drivers were studied at four coastal sites within the Northeast Atlantic Shelves Province (Bilbao35 (B35) and Urdaibai35 (U35) in the Bay of Biscay, Plymouth L4 (L4) in the English Channel and Stonehaven (SH) in the North Sea) using time series spanning 1999-2013. Seasonal community patterns were extracted at the level of broad zooplankton groups and copepod and cladoceran genera using redundancy analysis. Temperature was generally the environmental factor that explained most of the taxa seasonal variations at the four sites. However, between-site differences related to latitude and trophic status (i.e. from oligotrophic to mesotrophic) were observed in the seasonality of zooplankton community, mainly in the pattern of taxa that peaked in spring-summer as opposed to late autumn-winter zooplankton, which were linked primarily to differences in the seasonal pattern of phytoplankton. The percentage of taxa variations explained by environmental factors increased with latitude and trophic status likely related to the increase in the co-variation of temperature and chlorophyll a, as well as in the increase in regularity of the seasonal patterns of both temperature and chlorophyll a from south to north, and of chlorophyll a with trophic status. Cladocerans and cirripede larvae at B35 and U35, echinoderm larvae at L4 and decapod larvae at SH made the highest contribution to shape the main mode of seasonal pattern of zooplankton community, which showed a seasonal delay with latitude, as well as with the increase in trophic status.

  1. Community structure detection based on the neighbor node degree information

    NASA Astrophysics Data System (ADS)

    Tang, Li-Ying; Li, Sheng-Nan; Lin, Jian-Hong; Guo, Qiang; Liu, Jian-Guo

    2016-11-01

    Community structure detection is of great significance for better understanding the network topology property. By taking into account the neighbor degree information of the topological network as the link weight, we present an improved Nonnegative Matrix Factorization (NMF) method for detecting community structure. The results for empirical networks show that the largest improved ratio of the Normalized Mutual Information value could reach 63.21%. Meanwhile, for synthetic networks, the highest Normalized Mutual Information value could closely reach 1, which suggests that the improved method with the optimal λ can detect the community structure more accurately. This work is helpful for understanding the interplay between the link weight and the community structure detection.

  2. Zooplankton fecal pellets, marine snow, phytodetritus and the ocean's biological pump

    NASA Astrophysics Data System (ADS)

    Turner, Jefferson T.

    2015-01-01

    The 'biological pump' is the process by which photosynthetically-produced organic matter in the ocean descends from the surface layer to depth by a combination of sinking particles, advection or vertical mixing of dissolved organic matter, and transport by animals. Particulate organic matter that is exported downward from the euphotic zone is composed of combinations of fecal pellets from zooplankton and fish, organic aggregates known as 'marine snow' and phytodetritus from sinking phytoplankton. Previous reviews by Turner and Ferrante (1979) and Turner (2002) focused on publications that appeared through late 2001. Since that time, studies of the biological pump have continued, and there have been >300 papers on vertical export flux using sediment traps, large-volume filtration systems and other techniques from throughout the global ocean. This review will focus primarily on recent studies that have appeared since 2001. Major topics covered in this review are (1) an overview of the biological pump, and its efficiency and variability, and the role of dissolved organic carbon in the biological pump; (2) zooplankton fecal pellets, including the contribution of zooplankton fecal pellets to export flux, epipelagic retention of zooplankton fecal pellets due to zooplankton activities, zooplankton vertical migration and fecal pellet repackaging, microbial ecology of fecal pellets, sinking velocities of fecal pellets and aggregates, ballasting of sinking particles by mineral contents, phytoplankton cysts, intact cells and harmful algae toxins in fecal pellets, importance of fecal pellets from various types of zooplankton, and the role of zooplankton fecal pellets in picoplankton export; (3) marine snow, including the origins, abundance, and distributions of marine snow, particles and organisms associated with marine snow, consumption and fragmentation of marine snow by animals, pathogens associated with marine snow; (4) phytodetritus, including pulsed export of

  3. Nutrients, phytoplankton, zooplankton, and macrobenthos

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

    2017-01-01

    Lower trophic levels support the prey fish on which most sport fish depend. Therefore, understanding the production potential of lower trophic levels is integral to the management of Lake Ontario’s fishery resources. Lower trophic-level productivity differs among offshore and nearshore waters. In the offshore, there is concern about the ability of the lake to support Alewife (Table 1) production due to a perceived decline in productivity of phytoplankton and zooplankton whereas, in the nearshore, there is a concern about excessive attached algal production (e.g., Cladophora) associated with higher nutrient concentrations—the oligotrophication of the offshore and the eutrophication of the nearshore (Mills et al. 2003; Holeck et al. 2008; Dove 2009; Koops et al. 2015; Stewart et al. 2016). Even though the collapse of the Alewife population in Lake Huron in 2003 (and the associated decline in the Chinook Salmon fishery) may have been precipitated by a cold winter (Dunlop and Riley 2013), Alewife had not returned to high abundances in Lake Huron as of 2014 (Roseman et al. 2015). Failure of the Alewife population to recover from collapse has been attributed to declines in lower trophic-level production (Barbiero et al. 2011; Bunnell et al. 2014; but see He et al. 2015). In Lake Michigan, concerns of a similar Alewife collapse led to a decrease in the number of Chinook Salmon stocked. If lower trophic-level production declines in Lake Ontario, a similar management action could be considered. On the other hand, in Lake Erie, which supplies most of the water in Lake Ontario, eutrophication is increasing and so are harmful algal blooms. Thus, there is also a concern that nutrient levels and algal blooms could increase in Lake Ontario, especially in the nearshore. Solutions to the two processes of concern—eutrophication in the nearshore and oligotrophication in the offshore—may be mutually exclusive. In either circumstance, fisheries management needs information on

  4. A new hierarchical method to find community structure in networks

    NASA Astrophysics Data System (ADS)

    Saoud, Bilal; Moussaoui, Abdelouahab

    2018-04-01

    Community structure is very important to understand a network which represents a context. Many community detection methods have been proposed like hierarchical methods. In our study, we propose a new hierarchical method for community detection in networks based on genetic algorithm. In this method we use genetic algorithm to split a network into two networks which maximize the modularity. Each new network represents a cluster (community). Then we repeat the splitting process until we get one node at each cluster. We use the modularity function to measure the strength of the community structure found by our method, which gives us an objective metric for choosing the number of communities into which a network should be divided. We demonstrate that our method are highly effective at discovering community structure in both computer-generated and real-world network data.

  5. The community structure of the global corporate network.

    PubMed

    Vitali, Stefania; Battiston, Stefano

    2014-01-01

    We investigate the community structure of the global ownership network of transnational corporations. We find a pronounced organization in communities that cannot be explained by randomness. Despite the global character of this network, communities reflect first of all the geographical location of firms, while the industrial sector plays only a marginal role. We also analyze the meta-network in which the nodes are the communities and the links are obtained by aggregating the links among firms belonging to pairs of communities. We analyze the network centrality of the top 50 communities and we provide a quantitative assessment of the financial sector role in connecting the global economy.

  6. The Community Structure of the Global Corporate Network

    PubMed Central

    Vitali, Stefania; Battiston, Stefano

    2014-01-01

    We investigate the community structure of the global ownership network of transnational corporations. We find a pronounced organization in communities that cannot be explained by randomness. Despite the global character of this network, communities reflect first of all the geographical location of firms, while the industrial sector plays only a marginal role. We also analyze the meta-network in which the nodes are the communities and the links are obtained by aggregating the links among firms belonging to pairs of communities. We analyze the network centrality of the top 50 communities and we provide a quantitative assessment of the financial sector role in connecting the global economy. PMID:25126722

  7. Regional zooplankton dispersal provides spatial insurance for ecosystem function.

    PubMed

    Symons, Celia C; Arnott, Shelley E

    2013-05-01

    Changing environmental conditions are affecting diversity and ecosystem function globally. Theory suggests that dispersal from a regional species pool may buffer against changes in local community diversity and ecosystem function after a disturbance through the establishment of functionally redundant tolerant species. The spatial insurance provided by dispersal may decrease through time after environmental change as the local community monopolizes resources and reduces community invasibility. To test for evidence of the spatial insurance hypothesis and to determine the role dispersal timing plays in this response we conducted a field experiment using crustacean zooplankton communities in a subarctic region that is expected to be highly impacted by climate change - Churchill, Canada. Three experiments were conducted where nutrients, salt, and dispersal were manipulated. The three experiments differed in time-since-disturbance that the dispersers were added. We found that coarse measures of diversity (i.e. species richness, evenness, and Shannon-Weiner diversity) were generally resistant to large magnitude disturbances, and that dispersal had the most impact on diversity when dispersers were added shortly after disturbance. Ecosystem functioning (chl-a) was degraded in disturbed communities, but dispersal recovered ecosystem function to undisturbed levels. This spatial insurance for ecosystem function was mediated through changes in community composition and the relative abundance of functional groups. Results suggest that regional diversity and habitat connectivity will be important in the future to maintain ecosystem function by introducing functionally redundant species to promote compensatory dynamics. © 2012 Blackwell Publishing Ltd.

  8. Investigating Effects of Invasive Species on Plant Community Structure

    ERIC Educational Resources Information Center

    Franklin, Wilfred

    2008-01-01

    In this article, the author presents a field study project that explores factors influencing forest community structure and lifts the veil off of "plant blindness." This ecological study consists of three laboratories: (1) preliminary field trip to the study site; (2) plant survey; and (3) analyzing plant community structure with descriptive…

  9. Community Structural Instability, Anomie, Imitation and Adolescent Suicidal Behavior

    ERIC Educational Resources Information Center

    Thorlindsson, Thorolfur; Bernburg, Jon Gunnar

    2009-01-01

    The current study examines the contextual effects of community structural characteristics, as well as the mediating role of key social mechanisms, on youth suicidal behavior in Iceland. We argue that the contextual influence of community structural instability on youth suicidal behavior should be mediated by weak attachment to social norms and…

  10. Diversity and Phylogenetic Structure of Two Complex Marine Microbial Communities

    DTIC Science & Technology

    2004-09-01

    Science 190 and Engineering DOCTORAL DISSERTATION Diversity and Phylogenetic Structure of Two Complex Marine Microbial Communities by Vanja Klepac-Ceraj...Two Complex Marine Microbial Communities by Vanja Klepac-Ceraj Massachusetts Institute of Technology Cambridge, Massachusetts 02139 and Woods Hole...Phylogenetic Structure of Two Complex Marine Microbial Communities. Ph.D. Thesis. MIT/WHOI, 2004-11. Approved for publication; distribution unlimited

  11. Similarity between community structures of different online social networks and its impact on underlying community detection

    NASA Astrophysics Data System (ADS)

    Fan, W.; Yeung, K. H.

    2015-03-01

    As social networking services are popular, many people may register in more than one online social network. In this paper we study a set of users who have accounts of three online social networks: namely Foursquare, Facebook and Twitter. Community structure of this set of users may be reflected in these three online social networks. Therefore, high correlation between these reflections and the underlying community structure may be observed. In this work, community structures are detected in all three online social networks. Also, we investigate the similarity level of community structures across different networks. It is found that they show strong correlation with each other. The similarity between different networks may be helpful to find a community structure close to the underlying one. To verify this, we propose a method to increase the weights of some connections in networks. With this method, new networks are generated to assist community detection. By doing this, value of modularity can be improved and the new community structure match network's natural structure better. In this paper we also show that the detected community structures of online social networks are correlated with users' locations which are identified on Foursquare. This information may also be useful for underlying community detection.

  12. Annual cycle of zooplankton abundance and species composition in Izmit Bay (the northeastern Marmara Sea)

    NASA Astrophysics Data System (ADS)

    Isinibilir, Melek; Kideys, Ahmet E.; Tarkan, Ahmet N.; Yilmaz, I. Noyan

    2008-07-01

    The monthly abundance, biomass and taxonomic composition of zooplankton of Izmit Bay (the northeastern Marmara Sea) were studied from October 2001 to September 2002. Most species within the zooplankton community displayed a clear pattern of succession throughout the year. Generally copepods and cladocerans were the most abundant groups, while the contribution of meroplankton increased at inner-most stations and dominated the zooplankton. Both species number ( S) and diversity ( H') were positively influenced by the increase in salinity of upper layers ( r = 0.30 and r = 0.31, p < 0.001, respectively), while chlorophyll a was negatively affected ( r = -0.36, p < 0.001). Even though Noctiluca scintillans had a significant seasonality ( F11,120 = 8.45, p < 0.001, ANOVA), abundance was not related to fluctuations in temperature and only chlorophyll a was adversely correlated ( r = -0.35, p < 0.001). In general, there are some minor differences in zooplankton assemblages of upper and lower layers. A comparison of the species composition and abundance of Izmit Bay with other Black Sea bays reveals a high similarity between them.

  13. Parallel structure among environmental gradients and three trophic levels in a subarctic estuary

    Speckman, Suzann G.; Piatt, John F.; Minte-Vera, C. V.; Parrish, Julia K.

    2005-01-01

    We assessed spatial and temporal variability in the physical environment of a subarctic estuary, and examined concurrent patterns of chlorophyll α abundance (fluorescence), and zooplankton and forage fish community structure. Surveys were conducted in lower Cook Inlet, Alaska, during late July and early August from 1997 through 1999. Principle components analysis (PCA) revealed that spatial heterogeneity in the physical oceanographic environment of lower Cook Inlet could be modeled as three marine-estuarine gradients characterized by temperature, salinity, bottom depth, and turbidity. The gradients persisted from 1997 through 1999, and PCA explained 68% to 92% of the variance in physical oceanography for each gradient-year combination. Correlations between chlorophyll α abundance and distribution and the PCA axes were weak. Chlorophyll was reduced by turbidity, and low levels occurred in areas with high levels of suspended sediments. Detrended correspondence analysis (DCA) was used to order the sample sites based on species composition and to order the zooplankton and forage fish taxa based on similarities among sample sites for each gradient-year. Correlations between the structure of the physical environment (PCA axis 1) and zooplankton community structure (DCA axis 1) were strong (r = 0.43-0.86) in all years for the three marine-estuarine gradients, suggesting that zooplankton community composition was structured by the physical environment. The physical environment (PCA) and forage fish community structure (DCA) were weakly correlated in all years along Gradient 2, defined by halocline intensity and surface temperature and salinity, even though these physical variables were more important for defining zooplankton habitats. However, the physical environment (PCA) and forage fish community structure (DCA) were strongly correlated along the primary marine-estuarine gradient (#1) in 1997 (r = 0.87) and 1998 (r = 0.82). The correlation was poor (r = 0.32) in

  14. Parallel structure among environmental gradients and three trophic levels in a subarctic estuary

    NASA Astrophysics Data System (ADS)

    Speckman, Suzann G.; Piatt, John F.; Minte-Vera, Carolina V.; Parrish, Julia K.

    2005-07-01

    We assessed spatial and temporal variability in the physical environment of a subarctic estuary, and examined concurrent patterns of chlorophyll α abundance (fluorescence), and zooplankton and forage fish community structure. Surveys were conducted in lower Cook Inlet, Alaska, during late July and early August from 1997 through 1999. Principle components analysis (PCA) revealed that spatial heterogeneity in the physical oceanographic environment of lower Cook Inlet could be modeled as three marine-estuarine gradients characterized by temperature, salinity, bottom depth, and turbidity. The gradients persisted from 1997 through 1999, and PCA explained 68% to 92% of the variance in physical oceanography for each gradient-year combination. Correlations between chlorophyll α abundance and distribution and the PCA axes were weak. Chlorophyll was reduced by turbidity, and low levels occurred in areas with high levels of suspended sediments. Detrended correspondence analysis (DCA) was used to order the sample sites based on species composition and to order the zooplankton and forage fish taxa based on similarities among sample sites for each gradient-year. Correlations between the structure of the physical environment (PCA axis 1) and zooplankton community structure (DCA axis 1) were strong ( r = 0.43-0.86) in all years for the three marine-estuarine gradients, suggesting that zooplankton community composition was structured by the physical environment. The physical environment (PCA) and forage fish community structure (DCA) were weakly correlated in all years along Gradient 2, defined by halocline intensity and surface temperature and salinity, even though these physical variables were more important for defining zooplankton habitats. However, the physical environment (PCA) and forage fish community structure (DCA) were strongly correlated along the primary marine-estuarine gradient (#1) in 1997 ( r = 0.87) and 1998 ( r = 0.82). The correlation was poor ( r = 0.32) in

  15. Understanding Microbial Communities: Function, Structure and Dynamics

    DTIC Science & Technology

    2015-02-11

    allow us to characterise the species composition of these communities from a variety of environmentally and medically-relevant habitats. Despite this...ecology. The primary purpose of this program was to facilitate the building a scientific community around using and developing mathematical...biology and advancement of new biotechnologies and medical applications. Summary of results (a) Activities Over the course of the 4 months of

  16. A review of zooplankton investigations of the Black Sea over the last decade

    NASA Astrophysics Data System (ADS)

    Kideys, Ahmet E.; Kovalev, Alexander V.; Shulman, Gregory; Gordina, Anna; Bingel, Ferit

    2000-03-01

    Investigations performed in the last decade indicate that there have been important changes in the zooplankton composition and structure in the Black Sea. However, contrasting events taking place in different regions of the Black Sea indicate a non-uniform structure of its ecosystem. Several fodder zooplankton species have either disappeared from or substantially decreased in number at different sampling sites of the Black Sea over the last one or two decades. Some other species adapted to thrive in eutrophic conditions have either appeared or increased in quantity. Meanwhile the biomass of the fodder zooplankton has also fluctuated considerably through the years. However, there seems to be a reverse trend in the long-term variation of fodder zooplankton between the shallow western and deep eastern areas. Over the last few decades the abundance of fish larvae has decreased significantly when compared either to past records or with larval abundances of other seas. This was shown to be due mainly to malnutrition of larvae. One of the most striking changes in the ichthyoplankton has been the shift in the spawning areas of the main fish species, the anchovy Engraulis encrasicolus from the northwestern to the southeastern Black Sea. Even the invading ctenophore Mnemiopsis were found to be starving. The condition of other species ( Calanus euxinus and Pleurobrachia pileus) disclosed the fact that cyclonic regions where chlorophyll and nutrient concentrations are high, provide better nutrition than anticyclonic regions.

  17. Acoustic Scattering Models of Zooplankton and Microstructure

    DTIC Science & Technology

    1999-09-30

    1998, a remotely operated vehicle was used to deploy acoustic transducers so that the acoustic scattering by siphonophores , a gas-bearing animal, could...their high frequency acoustics systems. 4) In addition, we have identified two types of zooplankton ( siphonophores and pteropods) that have high...Benfield, P.H. Wiebe, and D. Chu, 1999. “In situ measurements of acoustic target strengths of siphonophores ,” Proceedings of the 2nd EAA

  18. A Stochastic Model for Detecting Overlapping and Hierarchical Community Structure

    PubMed Central

    Cao, Xiaochun; Wang, Xiao; Jin, Di; Guo, Xiaojie; Tang, Xianchao

    2015-01-01

    Community detection is a fundamental problem in the analysis of complex networks. Recently, many researchers have concentrated on the detection of overlapping communities, where a vertex may belong to more than one community. However, most current methods require the number (or the size) of the communities as a priori information, which is usually unavailable in real-world networks. Thus, a practical algorithm should not only find the overlapping community structure, but also automatically determine the number of communities. Furthermore, it is preferable if this method is able to reveal the hierarchical structure of networks as well. In this work, we firstly propose a generative model that employs a nonnegative matrix factorization (NMF) formulization with a l2,1 norm regularization term, balanced by a resolution parameter. The NMF has the nature that provides overlapping community structure by assigning soft membership variables to each vertex; the l2,1 regularization term is a technique of group sparsity which can automatically determine the number of communities by penalizing too many nonempty communities; and hence the resolution parameter enables us to explore the hierarchical structure of networks. Thereafter, we derive the multiplicative update rule to learn the model parameters, and offer the proof of its correctness. Finally, we test our approach on a variety of synthetic and real-world networks, and compare it with some state-of-the-art algorithms. The results validate the superior performance of our new method. PMID:25822148

  19. Warming alters community size structure and ecosystem functioning

    PubMed Central

    Dossena, Matteo; Yvon-Durocher, Gabriel; Grey, Jonathan; Montoya, José M.; Perkins, Daniel M.; Trimmer, Mark; Woodward, Guy

    2012-01-01

    Global warming can affect all levels of biological complexity, though we currently understand least about its potential impact on communities and ecosystems. At the ecosystem level, warming has the capacity to alter the structure of communities and the rates of key ecosystem processes they mediate. Here we assessed the effects of a 4°C rise in temperature on the size structure and taxonomic composition of benthic communities in aquatic mesocosms, and the rates of detrital decomposition they mediated. Warming had no effect on biodiversity, but altered community size structure in two ways. In spring, warmer systems exhibited steeper size spectra driven by declines in total community biomass and the proportion of large organisms. By contrast, in autumn, warmer systems had shallower size spectra driven by elevated total community biomass and a greater proportion of large organisms. Community-level shifts were mirrored by changes in decomposition rates. Temperature-corrected microbial and macrofaunal decomposition rates reflected the shifts in community structure and were strongly correlated with biomass across mesocosms. Our study demonstrates that the 4°C rise in temperature expected by the end of the century has the potential to alter the structure and functioning of aquatic ecosystems profoundly, as well as the intimate linkages between these levels of ecological organization. PMID:22496185

  20. Effects of drought on avian community structure

    Thomas P. Albright; Anna M. Pidgeon; Chadwick D. Rittenhouse; Murray K. Clayton; Curtis H. Flather; Patrick D. Culbert; Brian D. Wardlow; Volker C. Radeloff

    2010-01-01

    Droughts are expected to become more frequent under global climate change. Avifauna depend on precipitation for hydration, cover, and food. While there are indications that avian communities respond negatively to drought, little is known about the response of birds with differing functional and behavioural traits, what time periods and indicators of drought are most...

  1. Decision Making Structures in Community Colleges.

    ERIC Educational Resources Information Center

    Konrad, Abram G.

    The governance of community colleges in western Canada is increasingly influenced by the activities of federal and regional agencies, provincial legislatures, professional and trade associations, and advisory committees. Decision-making is increasingly centralized so that programs are standardized, procedures are routinized, and colleges lack…

  2. Triclosan alterations of estuarine phytoplankton community structure.

    PubMed

    Pinckney, James L; Thompson, Laura; Hylton, Sarah

    2017-06-15

    Antimicrobial additives in pharmaceutical and personal care products are a major environmental concern due to their potential ecological impacts on aquatic ecosystems. Triclosan (TCS) has been used as an antiseptic, disinfectant, and preservative in various media. The sublethal and lethal effects of TCS on estuarine phytoplankton community composition were investigated using bioassays of natural phytoplankton communities to measure phytoplankton responses to different concentrations of TCS ranging from 1 to 200μgl -1 . The EC 50 (the concentration of an inhibitor where the growth is reduced by half) for phytoplankton groups (diatoms, chlorophytes, cryptophytes) examined in this ranged from 10.7 to 113.8μg TCS l -1 . Exposures resulted in major shifts in phytoplankton community composition at concentrations as low as 1.0μg TCS l -1 . This study demonstrates estuarine ecosystem sensitivity to TCS exposure and highlights potential alterations in phytoplankton community composition at what are typically environmental concentrations of TCS in urbanized estuaries. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Learning Communities: A Structure for Educational Coherence.

    ERIC Educational Resources Information Center

    Matthews, Roberta; And Others

    1996-01-01

    College and university learning communities build a sense of group identity. Institutions are establishing them for varied purposes and student populations, including first-year interest groups, general education core courses, gateway courses, developmental and basic studies, honors programs, and work in the major or minor. For implementation,…

  4. Zooplankton and Micronekton Distribution and Interaction with Predators at the Northwest Atlantic Shelf Break and its Canyons

    DTIC Science & Technology

    2014-09-30

    with marine mammals and other predators . APPROACH The datasets being examined in this project include: 1. Depth-stratified net samples from 1...with Predators at the Northwest Atlantic Shelf Break and its Canyons Gareth L. Lawson, Andone C. Lavery, & Peter H. Wiebe Woods Hole...determining the distribution, abundance, and community composition of zooplankton and micronekton and their association with predators (including marine

  5. Changes in the pelagic crustacean zooplankton of high-boreal Island Lake, Saskatchewan, associated with uranium mining.

    PubMed

    Melville, G E

    1995-01-01

    Island Lake, Saskatchewan, has become eutrophic, subsaline (salinity between 0.5 and 3.0 g I(-1)) and contaminated with several metals over the last decade. In this study, the crustacean zooplankton community in the lake in early summer 1989 is compared to the community during the early summers of the baseline years 1978 and 1979, based on archived environmental impact assessment samples. Community composition has changed, probably because of salinization and perhaps, to a lesser extent, eutrophication. Calanoid copepods have disappeared, while the numbers of species of cyclopoid copepods and cladocerans have increased. Ceriodaphnia reticulata, present in 1988 only, was more numerous than any other species during all three years. Densities of all other species were very low in 1989, which has led to lower diversity (Simpsons Index). Predation by Chaoborus probably contributed to the low abundances in 1989. The characteristics of the zooplankton community in 1989 were very similar to those of zooplankton in culturally acidified lakes, and indicate that Island Lake is in poor health. The success of Ceriodaphnia, a standard toxicity bioassay genus, is noteworthy under such contaminated conditions. While the taxonomic changes are obvious, the zooplankton data are limited; therefore causes can only be inferred. The study demonstrates the need for more and better ecosystem-specific biological information in order to do environmental impact assessments, in this case for mining in the north.

  6. ANNUAL CYCLE OF PERIPHYTON, ZOOPLANKTON, AND WATER QUALITY PARAMETERS ALONG A 5 STATION TRANSECT OF ESCAMBIA BAY, FL

    EPA Science Inventory

    Phytoplankton, zooplankton and water quality parameters were monitored monthly along a 5-station transect in Escambia Bay (Pensacola, FL) from fall 1999 to fall 2000. To provide insight into nutrient processing in Escambia Bay and effects of grazers on phytoplankton community st...

  7. Bottom-up linkages between primary production, zooplankton, and fish in a shallow, hypereutrophic lake.

    PubMed

    Matsuzaki, Shin-Ichiro S; Suzuki, Kenta; Kadoya, Taku; Nakagawa, Megumi; Takamura, Noriko

    2018-06-09

    Nutrient supply is a key bottom-up control of phytoplankton primary production in lake ecosystems. Top-down control via grazing pressure by zooplankton also constrains primary production, and primary production may simultaneously affect zooplankton. Few studies have addressed these bidirectional interactions. We used convergent cross-mapping (CCM), a numerical test of causal associations, to quantify the presence and direction of the causal relationships among environmental variables (light availability, surface water temperature, NO 3 -N, and PO 4 -P), phytoplankton community composition, primary production, and the abundances of five functional zooplankton groups (large-cladocerans, small-cladocerans, rotifers, calanoids, and cyclopoids) in Lake Kasumigaura, a shallow, hypereutrophic lake in Japan. CCM suggested that primary production was causally influenced by NO 3 -N and phytoplankton community composition; there was no detectable evidence of a causal effect of zooplankton on primary production. Our results also suggest that rotifers and cyclopoids were forced by primary production, and cyclopoids were further influenced by rotifers. However, our CCM suggested that primary production was weakly influenced by rotifers (i.e., bidirectional interaction). These findings may suggest complex linkages between nutrients, primary production, and rotifers and cyclopoids, a pattern that has not been previously detected or has been neglected. We used linear regression analysis to examine the relationships between the zooplankton community and pond smelt (Hypomesus nipponensis), the most abundant planktivore and the most important commercial fish species in Lake Kasumigaura. The relative abundance of pond smelt was significantly and positively correlated with the abundances of rotifers and cyclopoids, which were causally influenced by primary production. This finding suggests that bottom-up linkages between nutrient, primary production, and zooplankton abundance might be a

  8. [Phytoplankton and zooplankton of the industrial reservoir R-9 (Lake Karachay)].

    PubMed

    Priakhin, E A; Triapitsina, G A; Atamaniuk, N I; Osipov, D I; Stukalov, P M; Ivanov, I A; Popova, I Ia; Akleev, A V

    2012-01-01

    Planktonic communities of the Reservoir-9 (Lake Karachay, storage reservoir of liquid medium-level radioactive waste of the Mayak Production Association) are exposed to the severe radioactive forcing (in 2010 the total beta-activity of the water was 1.8 x 10(7) Bq/L, total alpha-activity was 1.1 x 10(4) Bq/L), aswell as to the chemical contamination (level of nitrates in water 4.1 g/L). The calculated values of the absorbed dose rate were 130 Gy/day for phytoplankton and 4.0 Gy/day for zooplankton. Extremely low species diversity, the overwhelming dominance of one species (phytoplankton is close to a monoculture of ubiquitous cyanobacteria Geitlerinema amphibium, zooplankton--to a monoculture of rotifers Hexarthrafennica), wide fluctuations in numbers of algae, a low number of zooplankton were the most substantial characteristics of the plankton communities in Lake Karachay. So, plankton communities status is a sign of environmental retrogress in this ecosystem.

  9. Virality Prediction and Community Structure in Social Networks

    NASA Astrophysics Data System (ADS)

    Weng, Lilian; Menczer, Filippo; Ahn, Yong-Yeol

    2013-08-01

    How does network structure affect diffusion? Recent studies suggest that the answer depends on the type of contagion. Complex contagions, unlike infectious diseases (simple contagions), are affected by social reinforcement and homophily. Hence, the spread within highly clustered communities is enhanced, while diffusion across communities is hampered. A common hypothesis is that memes and behaviors are complex contagions. We show that, while most memes indeed spread like complex contagions, a few viral memes spread across many communities, like diseases. We demonstrate that the future popularity of a meme can be predicted by quantifying its early spreading pattern in terms of community concentration. The more communities a meme permeates, the more viral it is. We present a practical method to translate data about community structure into predictive knowledge about what information will spread widely. This connection contributes to our understanding in computational social science, social media analytics, and marketing applications.

  10. Virality Prediction and Community Structure in Social Networks

    PubMed Central

    Weng, Lilian; Menczer, Filippo; Ahn, Yong-Yeol

    2013-01-01

    How does network structure affect diffusion? Recent studies suggest that the answer depends on the type of contagion. Complex contagions, unlike infectious diseases (simple contagions), are affected by social reinforcement and homophily. Hence, the spread within highly clustered communities is enhanced, while diffusion across communities is hampered. A common hypothesis is that memes and behaviors are complex contagions. We show that, while most memes indeed spread like complex contagions, a few viral memes spread across many communities, like diseases. We demonstrate that the future popularity of a meme can be predicted by quantifying its early spreading pattern in terms of community concentration. The more communities a meme permeates, the more viral it is. We present a practical method to translate data about community structure into predictive knowledge about what information will spread widely. This connection contributes to our understanding in computational social science, social media analytics, and marketing applications. PMID:23982106

  11. Virality prediction and community structure in social networks.

    PubMed

    Weng, Lilian; Menczer, Filippo; Ahn, Yong-Yeol

    2013-01-01

    How does network structure affect diffusion? Recent studies suggest that the answer depends on the type of contagion. Complex contagions, unlike infectious diseases (simple contagions), are affected by social reinforcement and homophily. Hence, the spread within highly clustered communities is enhanced, while diffusion across communities is hampered. A common hypothesis is that memes and behaviors are complex contagions. We show that, while most memes indeed spread like complex contagions, a few viral memes spread across many communities, like diseases. We demonstrate that the future popularity of a meme can be predicted by quantifying its early spreading pattern in terms of community concentration. The more communities a meme permeates, the more viral it is. We present a practical method to translate data about community structure into predictive knowledge about what information will spread widely. This connection contributes to our understanding in computational social science, social media analytics, and marketing applications.

  12. Community structure in traffic zones based on travel demand

    NASA Astrophysics Data System (ADS)

    Sun, Li; Ling, Ximan; He, Kun; Tan, Qian

    2016-09-01

    Large structure in complex networks can be studied by dividing it into communities or modules. Urban traffic system is one of the most critical infrastructures. It can be abstracted into a complex network composed of tightly connected groups. Here, we analyze community structure in urban traffic zones based on the community detection method in network science. Spectral algorithm using the eigenvectors of matrices is employed. Our empirical results indicate that the traffic communities are variant with the travel demand distribution, since in the morning the majority of the passengers are traveling from home to work and in the evening they are traveling a contrary direction. Meanwhile, the origin-destination pairs with large number of trips play a significant role in urban traffic network's community division. The layout of traffic community in a city also depends on the residents' trajectories.

  13. Investigating brain community structure abnormalities in bipolar disorder using path length associated community estimation.

    PubMed

    Gadelkarim, Johnson J; Ajilore, Olusola; Schonfeld, Dan; Zhan, Liang; Thompson, Paul M; Feusner, Jamie D; Kumar, Anand; Altshuler, Lori L; Leow, Alex D

    2014-05-01

    In this article, we present path length associated community estimation (PLACE), a comprehensive framework for studying node-level community structure. Instead of the well-known Q modularity metric, PLACE utilizes a novel metric, Ψ(PL), which measures the difference between intercommunity versus intracommunity path lengths. We compared community structures in human healthy brain networks generated using these two metrics and argued that Ψ(PL) may have theoretical advantages. PLACE consists of the following: (1) extracting community structure using top-down hierarchical binary trees, where a branch at each bifurcation denotes a collection of nodes that form a community at that level, (2) constructing and assessing mean group community structure, and (3) detecting node-level changes in community between groups. We applied PLACE and investigated the structural brain networks obtained from a sample of 25 euthymic bipolar I subjects versus 25 gender- and age-matched healthy controls. Results showed community structural differences in posterior default mode network regions, with the bipolar group exhibiting left-right decoupling. Copyright © 2013 Wiley Periodicals, Inc.

  14. Looking inside the Ocean: Toward an Autonomous Imaging System for Monitoring Gelatinous Zooplankton

    PubMed Central

    Corgnati, Lorenzo; Marini, Simone; Mazzei, Luca; Ottaviani, Ennio; Aliani, Stefano; Conversi, Alessandra; Griffa, Annalisa

    2016-01-01

    Marine plankton abundance and dynamics in the open and interior ocean is still an unknown field. The knowledge of gelatinous zooplankton distribution is especially challenging, because this type of plankton has a very fragile structure and cannot be directly sampled using traditional net based techniques. To overcome this shortcoming, Computer Vision techniques can be successfully used for the automatic monitoring of this group.This paper presents the GUARD1 imaging system, a low-cost stand-alone instrument for underwater image acquisition and recognition of gelatinous zooplankton, and discusses the performance of three different methodologies, Tikhonov Regularization, Support Vector Machines and Genetic Programming, that have been compared in order to select the one to be run onboard the system for the automatic recognition of gelatinous zooplankton. The performance comparison results highlight the high accuracy of the three methods in gelatinous zooplankton identification, showing their good capability in robustly selecting relevant features. In particular, Genetic Programming technique achieves the same performances of the other two methods by using a smaller set of features, thus being the most efficient in avoiding computationally consuming preprocessing stages, that is a crucial requirement for running on an autonomous imaging system designed for long lasting deployments, like the GUARD1. The Genetic Programming algorithm has been installed onboard the system, that has been operationally tested in a two-months survey in the Ligurian Sea, providing satisfactory results in terms of monitoring and recognition performances. PMID:27983638

  15. Exploratory Visualization of Graphs Based on Community Structure

    ERIC Educational Resources Information Center

    Liu, Yujie

    2013-01-01

    Communities, also called clusters or modules, are groups of nodes which probably share common properties and/or play similar roles within a graph. They widely exist in real networks such as biological, social, and information networks. Allowing users to interactively browse and explore the community structure, which is essential for understanding…

  16. Faculty Scholarship at Community Colleges: Culture, Institutional Structures, and Socialization

    ERIC Educational Resources Information Center

    Morest, Vanessa Smith

    2015-01-01

    This chapter looks at community college faculty engagement in scholarship. Community college faculty spend the majority of their time engaged in teaching, and therefore their scholarship typically focuses on strengthening curriculum and instruction. The paper identifies some of the structural and cultural challenges and supports to scholarship at…

  17. Cascading failures in complex networks with community structure

    NASA Astrophysics Data System (ADS)

    Lin, Guoqiang; di, Zengru; Fan, Ying

    2014-12-01

    Much empirical evidence shows that when attacked with cascading failures, scale-free or even random networks tend to collapse more extensively when the initially deleted node has higher betweenness. Meanwhile, in networks with strong community structure, high-betweenness nodes tend to be bridge nodes that link different communities, and the removal of such nodes will reduce only the connections among communities, leaving the networks fairly stable. Understanding what will affect cascading failures and how to protect or attack networks with strong community structure is therefore of interest. In this paper, we have constructed scale-free Community Networks (SFCN) and Random Community Networks (RCN). We applied these networks, along with the Lancichinett-Fortunato-Radicchi (LFR) benchmark, to the cascading-failure scenario to explore their vulnerability to attack and the relationship between cascading failures and the degree distribution and community structure of a network. The numerical results show that when the networks are of a power-law distribution, a stronger community structure will result in the failure of fewer nodes. In addition, the initial removal of the node with the highest betweenness will not lead to the worst cascading, i.e. the largest avalanche size. The Betweenness Overflow (BOF), an index that we developed, is an effective indicator of this tendency. The RCN, however, display a different result. In addition, the avalanche size of each node can be adopted as an index to evaluate the importance of the node.

  18. Factors Affecting Soil Microbial Community Structure in Tomato Cropping Systems

    Soil and rhizosphere microbial communities in agroecosystems may be affected by soil, climate, plant species, and management. We identified some of the most important factors controlling microbial biomass and community structure in an agroecosystem utilizing tomato plants with the following nine tre...

  19. Covariance, correlation matrix, and the multiscale community structure of networks.

    PubMed

    Shen, Hua-Wei; Cheng, Xue-Qi; Fang, Bin-Xing

    2010-07-01

    Empirical studies show that real world networks often exhibit multiple scales of topological descriptions. However, it is still an open problem how to identify the intrinsic multiple scales of networks. In this paper, we consider detecting the multiscale community structure of network from the perspective of dimension reduction. According to this perspective, a covariance matrix of network is defined to uncover the multiscale community structure through the translation and rotation transformations. It is proved that the covariance matrix is the unbiased version of the well-known modularity matrix. We then point out that the translation and rotation transformations fail to deal with the heterogeneous network, which is very common in nature and society. To address this problem, a correlation matrix is proposed through introducing the rescaling transformation into the covariance matrix. Extensive tests on real world and artificial networks demonstrate that the correlation matrix significantly outperforms the covariance matrix, identically the modularity matrix, as regards identifying the multiscale community structure of network. This work provides a novel perspective to the identification of community structure and thus various dimension reduction methods might be used for the identification of community structure. Through introducing the correlation matrix, we further conclude that the rescaling transformation is crucial to identify the multiscale community structure of network, as well as the translation and rotation transformations.

  20. Jellyfish modulate bacterial dynamic and community structure.

    PubMed

    Tinta, Tinkara; Kogovšek, Tjaša; Malej, Alenka; Turk, Valentina

    2012-01-01

    Jellyfish blooms have increased in coastal areas around the world and the outbreaks have become longer and more frequent over the past few decades. The Mediterranean Sea is among the heavily affected regions and the common bloom-forming taxa are scyphozoans Aurelia aurita s.l., Pelagia noctiluca, and Rhizostoma pulmo. Jellyfish have few natural predators, therefore their carcasses at the termination of a bloom represent an organic-rich substrate that supports rapid bacterial growth, and may have a large impact on the surrounding environment. The focus of this study was to explore whether jellyfish substrate have an impact on bacterial community phylotype selection. We conducted in situ jellyfish-enrichment experiment with three different jellyfish species. Bacterial dynamic together with nutrients were monitored to assess decaying jellyfish-bacteria dynamics. Our results show that jellyfish biomass is characterized by protein rich organic matter, which is highly bioavailable to 'jellyfish-associated' and 'free-living' bacteria, and triggers rapid shifts in bacterial population dynamics and composition. Based on 16S rRNA clone libraries and denaturing gradient gel electrophoresis (DGGE) analysis, we observed a rapid shift in community composition from unculturable Alphaproteobacteria to culturable species of Gammaproteobacteria and Flavobacteria. The results of sequence analyses of bacterial isolates and of total bacterial community determined by culture independent genetic analysis showed the dominance of the Pseudoalteromonadaceae and the Vibrionaceae families. Elevated levels of dissolved proteins, dissolved organic and inorganic nutrient release, bacterial abundance and carbon production as well as ammonium concentrations characterized the degradation process. The biochemical composition of jellyfish species may influence changes in the amount of accumulated dissolved organic and inorganic nutrients. Our results can contribute insights into possible changes in

  1. A comparison of community and trophic structure in five marine ecosystems based on energy budgets and system metrics

    NASA Astrophysics Data System (ADS)

    Gaichas, Sarah; Skaret, Georg; Falk-Petersen, Jannike; Link, Jason S.; Overholtz, William; Megrey, Bernard A.; Gjøsæter, Harald; Stockhausen, William T.; Dommasnes, Are; Friedland, Kevin D.; Aydin, Kerim

    2009-04-01

    Energy budget models for five marine ecosystems were compared to identify differences and similarities in trophic and community structure. We examined the Gulf of Maine and Georges Bank in the northwest Atlantic Ocean, the combined Norwegian/Barents Seas in the northeast Atlantic Ocean, and the eastern Bering Sea and the Gulf of Alaska in the northeast Pacific Ocean. Comparable energy budgets were constructed for each ecosystem by aggregating information for similar species groups into consistent functional groups. Several ecosystem indices (e.g., functional group production, consumption and biomass ratios, cumulative biomass, food web macrodescriptors, and network metrics) were compared for each ecosystem. The comparative approach clearly identified data gaps for each ecosystem, an important outcome of this work. Commonalities across the ecosystems included overall high primary production and energy flow at low trophic levels, high production and consumption by carnivorous zooplankton, and similar proportions of apex predator to lower trophic level biomass. Major differences included distinct biomass ratios of pelagic to demersal fish, ranging from highest in the combined Norwegian/Barents ecosystem to lowest in the Alaskan systems, and notable differences in primary production per unit area, highest in the Alaskan and Georges Bank/Gulf of Maine ecosystems, and lowest in the Norwegian ecosystems. While comparing a disparate group of organisms across a wide range of marine ecosystems is challenging, this work demonstrates that standardized metrics both elucidate properties common to marine ecosystems and identify key distinctions useful for fisheries management.

  2. Trophic structure and avian communities across a salinity gradient in evaporation ponds of the San Francisco Bay estuary

    Takekawa, John Y.; Miles, A.K.; Schoellhamer, D.H.; Athearn, N.D.; Saiki, M.K.; Duffy, W.D.; Kleinschmidt, S.; Shellenbarger, G.G.; Jannusch, C.A.

    2006-01-01

    Commercial salt evaporation ponds comprise a large proportion of baylands adjacent to the San Francisco Bay, a highly urbanized estuary. In the past two centuries, more than 79% of the historic tidal wetlands in this estuary have been lost. Resource management agencies have acquired more than 10 000 ha of commercial salt ponds with plans to undertake one of the largest wetland restoration projects in North America. However, these plans have created debate about the ecological importance of salt ponds for migratory bird communities in western North America. Salt ponds are unique mesohaline (5–18 g l−1) to hyperhaline (> 40 g l−1) wetlands, but little is known of their ecological structure or value. Thus, we studied decommissioned salt ponds in the North Bay of the San Francisco Bay estuary from January 1999 through November 2001. We measured water quality parameters (salinity, DO, pH, temperature), nutrient concentrations, primary productivity, zooplankton, macroinvertebrates, fish, and birds across a range of salinities from 24 to 264 g l−1. Our studies documented how unique limnological characteristics of salt ponds were related to nutrient levels, primary productivity rates, invertebrate biomass and taxa richness, prey fish, and avian predator numbers. Salt ponds were shown to have unique trophic and physical attributes that supported large numbers of migratory birds. Therefore, managers should carefully weigh the benefits of increasing habitat for native tidal marsh species with the costs of losing these unique hypersaline systems.

  3. Floral colour versus phylogeny in structuring subalpine flowering communities.

    PubMed

    McEwen, Jamie R; Vamosi, Jana C

    2010-10-07

    The relative number of seeds produced by competing species can influence the community structure; yet, traits that influence seed production, such as pollinator attraction and floral colour, have received little attention in community ecology. Here, we analyse floral colour using reflectance spectra that include near-UV and examined the phylogenetic signal of floral colour. We found that coflowering species within communities tended to be more divergent in floral colour than expected by chance. However, coflowering species were not phylogenetically dispersed, in part due to our finding that floral colour is a labile trait with a weak phylogenetic signal. Furthermore, while we found that locally rare and common species exhibited equivalent floral colour distances from their coflowering neighbours, frequent species (those found in more communities) exhibited higher colour distances from their coflowering neighbours. Our findings support recent studies, which have found that (i) plant lineages exhibit frequent floral colour transitions; and (ii) traits that influence local population dynamics contribute to community structure.

  4. Upslope transport of near-bed zooplankton

    NASA Astrophysics Data System (ADS)

    Zimmer, Cheryl Ann

    2009-09-01

    Zooplankton residing just above the deep-sea floor is an important component of the benthic/benthopelagic food chain. Consuming planktonic particulates and organisms, holoplankton and meroplankton are prey for fish and large invertebrates. Mechanisms controlling their abundances have been explored over relatively long time scales (months to years). Here, zooplankton were sampled every 2 h for 2.2 d using a moored, automated, serial zooplankton pump. The physical regime (currents and temperature) 1-100 m above bottom was measured during an inclusive 24-d period. The study site was located on the upper continental slope (750 m) of the Mid-Atlantic Bight, between the productive shelf and more impoverished rise and abyss. The coupled biological and physical records indicated tidally driven, net upslope transport of the holoplankton. The copepod (74.5% of collections) time series showed marked periodicity with a peak frequency of ˜13 h, approximately the diurnal tide (Fourier analysis). Local maxima corresponded with minimal water temperatures. Moreover, tidal cross-slope flow was highly coherent and 90° out of phase with temperature. Thus, maximal copepod concentrations, originating in colder deeper water, would be transported up the slope by the tide. Estimated net displacement of ˜1 km/d would deliver the animals to continental-shelf depths within a couple weeks. Time series of the much less abundant larvaceans (urochordates) (15.3%) and polychaete larvae (8.9%) showed periodicities with peak frequencies of 8-9 h. Statistical significance of the periodic signals could not be determined due to low numbers. Revealing holoplankton dynamics on scales of hours, this study may contribute to understanding of, for example, copepod feeding and aggregation near the deep-sea floor.

  5. Acoustic discrimination of Southern Ocean zooplankton

    NASA Astrophysics Data System (ADS)

    Brierley, Andrew S.; Ward, Peter; Watkins, Jonathan L.; Goss, Catherine

    Acoustic surveys in the vicinity of the sub-Antarctic island of South Georgia during a period of exceptionally calm weather revealed the existence of a number of horizontally extensive yet vertically discrete scattering layers in the upper 250 m of the water column. These layers were fished with a Longhurst-Hardy plankton recorder (LHPR) and a multiple-opening 8 m 2 rectangular mid-water trawl (RMT8). Analysis of catches suggested that each scattering layer was composed predominantly of a single species (biovolume>95%) of either the euphausiids Euphausia frigida or Thysanöessa macrura, the hyperiid amphipod Themisto gaudichaudii, or the eucalaniid copepod Rhincalanus gigas. Instrumentation on the nets allowed their trajectories to be reconstructed precisely, and thus catch data to be related directly to the corresponding acoustic signals. Discriminant function analysis of differences between mean volume backscattering strength at 38, 120 and 200 kHz separated echoes originating from each of the dominant scattering layers, and other signals identified as originating from Antarctic krill ( Euphausia superba), with an overall correct classification rate of 77%. Using echo intensity data alone, gathered using hardware commonly employed for fishery acoustics, it is therefore possible to discriminate in situ between several zooplanktonic taxa, taxa which in some instances exhibit similar gross morphological characteristics and have overlapping length- frequency distributions. Acoustic signals from the mysid Antarctomysis maxima could also be discriminated once information on target distribution was considered, highlighting the value of incorporating multiple descriptors of echo characteristics into signal identification procedures. The ability to discriminate acoustically between zooplankton taxa could be applied to provide improved acoustic estimates of species abundance, and to enhance field studies of zooplankton ecology, distribution and species interactions.

  6. Spatio-temporal variability of the North Sea cod recruitment in relation to temperature and zooplankton.

    PubMed

    Nicolas, Delphine; Rochette, Sébastien; Llope, Marcos; Licandro, Priscilla

    2014-01-01

    The North Sea cod (Gadus morhua, L.) stock has continuously declined over the past four decades linked with overfishing and climate change. Changes in stock structure due to overfishing have made the stock largely dependent on its recruitment success, which greatly relies on environmental conditions. Here we focus on the spatio-temporal variability of cod recruitment in an effort to detect changes during the critical early life stages. Using International Bottom Trawl Survey (IBTS) data from 1974 to 2011, a major spatio-temporal change in the distribution of cod recruits was identified in the late 1990s, characterized by a pronounced decrease in the central and southeastern North Sea stock. Other minor spatial changes were also recorded in the mid-1980s and early 1990s. We tested whether the observed changes in recruits distribution could be related with direct (i.e. temperature) and/or indirect (i.e. changes in the quantity and quality of zooplankton prey) effects of climate variability. The analyses were based on spatially-resolved time series, i.e. sea surface temperature (SST) from the Hadley Center and zooplankton records from the Continuous Plankton Recorder Survey. We showed that spring SST increase was the main driver for the most recent decrease in cod recruitment. The late 1990s were also characterized by relatively low total zooplankton biomass, particularly of energy-rich zooplankton such as the copepod Calanus finmarchicus, which have further contributed to the decline of North Sea cod recruitment. Long-term spatially-resolved observations were used to produce regional distribution models that could further be used to predict the abundance of North Sea cod recruits based on temperature and zooplankton food availability.

  7. Spatio-Temporal Variability of the North Sea Cod Recruitment in Relation to Temperature and Zooplankton

    PubMed Central

    Nicolas, Delphine; Rochette, Sébastien; Llope, Marcos; Licandro, Priscilla

    2014-01-01

    The North Sea cod (Gadus morhua, L.) stock has continuously declined over the past four decades linked with overfishing and climate change. Changes in stock structure due to overfishing have made the stock largely dependent on its recruitment success, which greatly relies on environmental conditions. Here we focus on the spatio-temporal variability of cod recruitment in an effort to detect changes during the critical early life stages. Using International Bottom Trawl Survey (IBTS) data from 1974 to 2011, a major spatio-temporal change in the distribution of cod recruits was identified in the late 1990s, characterized by a pronounced decrease in the central and southeastern North Sea stock. Other minor spatial changes were also recorded in the mid-1980s and early 1990s. We tested whether the observed changes in recruits distribution could be related with direct (i.e. temperature) and/or indirect (i.e. changes in the quantity and quality of zooplankton prey) effects of climate variability. The analyses were based on spatially-resolved time series, i.e. sea surface temperature (SST) from the Hadley Center and zooplankton records from the Continuous Plankton Recorder Survey. We showed that spring SST increase was the main driver for the most recent decrease in cod recruitment. The late 1990s were also characterized by relatively low total zooplankton biomass, particularly of energy-rich zooplankton such as the copepod Calanus finmarchicus, which have further contributed to the decline of North Sea cod recruitment. Long-term spatially-resolved observations were used to produce regional distribution models that could further be used to predict the abundance of North Sea cod recruits based on temperature and zooplankton food availability. PMID:24551103

  8. Environmental Variability and Plankton Community Dynamics in the English Channel

    NASA Astrophysics Data System (ADS)

    Barton, A.; Gonzalez, F.; Atkinson, A.; Stock, C. A.

    2016-02-01

    Temporal environmental variation plays a key role in shaping plankton community structure and dynamics. In some cases, these ecological changes may be abrupt and long-lived, and constitute a significant change in overall ecosystem structure and function. The "Double Integration Hypothesis", posed recently by Di Lorenzo and Ohman to help explain these complex biophysical linkages, holds that atmospheric variability is filtered first through the ocean surface before secondarily imprinting on plankton communities. In this perspective, physical properties of the surface ocean, such as sea surface temperature (SST), integrate atmospheric white noise, resulting in a time series that is smoother and has more low than high frequency variability (red noise). Secondarily, long-lived zooplankton integrate over oceanographic conditions and further redden the power spectra. We test the generality of this hypothesis with extensive environmental and ecological data from the L4 station in the Western English Channel (1988-present), calculating power spectral slopes from anomaly time series for atmospheric forcing (wind stress and net heat fluxes), surface ocean conditions (SST and macronutrients), and the biomasses of well over 100 phytoplankton and zooplankton taxa. As expected, we find that SST and macronutrient concentrations are redder in character than white noise atmospheric forcing. However, we find that power spectral slopes for phytoplankton and zooplankton are generally not significantly less than found for oceanographic conditions. Moreover, we find a considerable range in power spectral slopes within the phytoplankton and zooplankton, reflecting the diversity of body sizes, traits, life histories, and predator-prey interactions. We interpret these findings using an idealized trait-based model with a single phytoplankton prey and zooplankton predator, configured to capture essential oceanographic properties at the L4 station, and discuss how changes in power spectral

  9. ZOOPLANKTON SIZE-SPECTRA IN GREAT LAKES COASTAL WATERS

    EPA Science Inventory

    Zooplankton mean size and size-distribution are affected by planktivore pressure and potentially reflect the condition of trophic interactions and ecosystem health. We used an optical plankton counter (OPC) to survey and assess zooplankton size-spectra for twenty locations in Lak...

  10. Indigenous species barcode database improves the identification of zooplankton

    PubMed Central

    Yang, Jianghua; Zhang, Wanwan; Sun, Jingying; Xie, Yuwei; Zhang, Yimin; Burton, G. Allen; Yu, Hongxia

    2017-01-01

    Incompleteness and inaccuracy of DNA barcode databases is considered an important hindrance to the use of metabarcoding in biodiversity analysis of zooplankton at the species-level. Species barcoding by Sanger sequencing is inefficient for organisms with small body sizes, such as zooplankton. Here mitochondrial cytochrome c oxidase I (COI) fragment barcodes from 910 freshwater zooplankton specimens (87 morphospecies) were recovered by a high-throughput sequencing platform, Ion Torrent PGM. Intraspecific divergence of most zooplanktons was < 5%, except Branchionus leydign (Rotifer, 14.3%), Trichocerca elongate (Rotifer, 11.5%), Lecane bulla (Rotifer, 15.9%), Synchaeta oblonga (Rotifer, 5.95%) and Schmackeria forbesi (Copepod, 6.5%). Metabarcoding data of 28 environmental samples from Lake Tai were annotated by both an indigenous database and NCBI Genbank database. The indigenous database improved the taxonomic assignment of metabarcoding of zooplankton. Most zooplankton (81%) with barcode sequences in the indigenous database were identified by metabarcoding monitoring. Furthermore, the frequency and distribution of zooplankton were also consistent between metabarcoding and morphology identification. Overall, the indigenous database improved the taxonomic assignment of zooplankton. PMID:28977035

  11. Fragmentation alters stream fish community structure in dendritic ecological networks.

    PubMed

    Perkin, Joshuah S; Gido, Keith B

    2012-12-01

    Effects of fragmentation on the ecology of organisms occupying dendritic ecological networks (DENs) have recently been described through both conceptual and mathematical models, but few hypotheses have been tested in complex, real-world ecosystems. Stream fishes provide a model system for assessing effects of fragmentation on the structure of communities occurring within DENs, including how fragmentation alters metacommunity dynamics and biodiversity. A recently developed habitat-availability measure, the "dendritic connectivity index" (DCI), allows for assigning quantitative measures of connectivity in DENs regardless of network extent or complexity, and might be used to predict fish community response to fragmentation. We characterized stream fish community structure in 12 DENs in the Great Plains, USA, during periods of dynamic (summer) and muted (fall) discharge regimes to test the DCI as a predictive model of fish community response to fragmentation imposed by road crossings. Results indicated that fish communities in stream segments isolated by road crossings had reduced species richness (alpha diversity) relative to communities that maintained connectivity with the surrounding DEN during summer and fall. Furthermore, isolated communities had greater dissimilarity (beta diversity) to downstream sites notisolated by road crossings during summer and fall. Finally, dissimilarity among communities within DENs decreased as a function of increased habitat connectivity (measured using the DCI) for summer and fall, suggesting that communities within highly connected DENs tend to be more homogeneous. Our results indicate that the DCI is sensitive to community effects of fragmentation in riverscapes and might be used by managers to predict ecological responses to changes in habitat connectivity. Moreover, our findings illustrate that relating structural connectivity of riverscapes to functional connectivity among communities might aid in maintaining metacommunity

  12. Community structure of copepods in the oceanic and neritic waters off Adélie and George V Land, East Antarctica, during the austral summer of 2008

    NASA Astrophysics Data System (ADS)

    Tachibana, Aiko; Watanabe, Yuko; Moteki, Masato; Hosie, Graham W.; Ishimaru, Takashi

    2017-06-01

    Copepods are one of the most important components of the Southern Ocean food web, and are widely distributed from surface to deeper waters. We conducted discrete depth sampling to clarify the community structure of copepods from the epi- to bathypelagic layers of the oceanic and neritic waters off Adélie and George V Land, East Antarctica, in the austral summer of 2008. Notably high diversity and species numbers were observed in the meso- and bathypelagic layers. Cluster analysis based on the similarity of copepod communities identified seven cluster groups, which corresponded well with water masses. In the epi- and upper- mesopelagic layers of the oceanic zone, the SB (Southern Boundary of the Antarctic Circumpolar Current) divided copepod communities. Conversely, in the lower meso- and bathypelagic layers (500-2000 m depth), communities were consistent across the SB. In these layers, the distributions of copepod species were separated by habitat depth ranges and feeding behaviour. The different food webs occur in the epipelagic layer with habitat segregation by zooplankton in their horizontal distribution ranges.

  13. Feeding on dispersed vs. aggregated particles: The effect of zooplankton feeding behavior on vertical flux.

    PubMed

    Koski, Marja; Boutorh, Julia; de la Rocha, Christina

    2017-01-01

    Zooplankton feeding activity is hypothesized to attenuate the downward flux of elements in the ocean. We investigated whether the zooplankton community composition could influence the flux attenuation, due to the differences of feeding modes (feeding on dispersed vs. aggregated particles) and of metabolic rates. We fed 5 copepod species-three calanoid, one harpacticoid and one poecilamastoid-microplankton food, in either dispersed or aggregated form and measured rates of respiration, fecal pellet production and egg production. Calanoid copepods were able to feed only on dispersed food; when their food was introduced as aggregates, their pellet production and respiration rates decreased to rates observed for starved individuals. In contrast, harpacticoids and the poecilamastoid copepod Oncaea spp. were able to feed only when the food was in the form of aggregates. The sum of copepod respiration, pellet production and egg production rates was equivalent to a daily minimum carbon demand of ca. 10% body weight-1 for all non-feeding copepods; the carbon demand of calanoids feeding on dispersed food was 2-3 times greater, and the carbon demand of harpacticoids and Oncaea spp. feeding on aggregates was >7 times greater, than the resting rates. The zooplankton species composition combined with the type of available food strongly influences the calculated carbon demand of a copepod community, and thus also the attenuation of vertical carbon flux.

  14. Feeding on dispersed vs. aggregated particles: The effect of zooplankton feeding behavior on vertical flux

    PubMed Central

    Boutorh, Julia; de la Rocha, Christina

    2017-01-01

    Zooplankton feeding activity is hypothesized to attenuate the downward flux of elements in the ocean. We investigated whether the zooplankton community composition could influence the flux attenuation, due to the differences of feeding modes (feeding on dispersed vs. aggregated particles) and of metabolic rates. We fed 5 copepod species—three calanoid, one harpacticoid and one poecilamastoid–microplankton food, in either dispersed or aggregated form and measured rates of respiration, fecal pellet production and egg production. Calanoid copepods were able to feed only on dispersed food; when their food was introduced as aggregates, their pellet production and respiration rates decreased to rates observed for starved individuals. In contrast, harpacticoids and the poecilamastoid copepod Oncaea spp. were able to feed only when the food was in the form of aggregates. The sum of copepod respiration, pellet production and egg production rates was equivalent to a daily minimum carbon demand of ca. 10% body weight-1 for all non-feeding copepods; the carbon demand of calanoids feeding on dispersed food was 2–3 times greater, and the carbon demand of harpacticoids and Oncaea spp. feeding on aggregates was >7 times greater, than the resting rates. The zooplankton species composition combined with the type of available food strongly influences the calculated carbon demand of a copepod community, and thus also the attenuation of vertical carbon flux. PMID:28545095

  15. Artificial neural networks and ecological communities (Book Review: Modelling community structure in freshwater ecosystems)

    DeAngelis, Donald L.

    2005-01-01

    Review info: Modeling community structure in freshwater ecosystems. Edited by Sovan Lek, Michele Scardi, Piet F.M. Verdonschot, Jean-Pierre Descy, and Young-Seuk Park, 2005. ISBN: 3-540-23940-5, 518 pp.

  16. Distributed network management in the flat structured mobile communities

    NASA Astrophysics Data System (ADS)

    Balandina, Elena

    2005-10-01

    Delivering proper management into the flat structured mobile communities is crucial for improving users experience and increase applications diversity in mobile networks. The available P2P applications do application-centric management, but it cannot replace network-wide management, especially when a number of different applications are used simultaneously in the network. The network-wide management is the key element required for a smooth transition from standalone P2P applications to the self-organizing mobile communities that maintain various services with quality and security guaranties. The classical centralized network management solutions are not applicable in the flat structured mobile communities due to the decentralized nature and high mobility of the underlying networks. Also the basic network management tasks have to be revised taking into account specialties of the flat structured mobile communities. The network performance management becomes more dependent on the current nodes' context, which also requires extension of the configuration management functionality. The fault management has to take into account high mobility of the network nodes. The performance and accounting managements are mainly targeted in maintain an efficient and fair access to the resources within the community, however they also allow unbalanced resource use of the nodes that explicitly permit it, e.g. as a voluntary donation to the community or due to the profession (commercial) reasons. The security management must implement the new trust models, which are based on the community feedback, professional authorization, and a mix of both. For fulfilling these and another specialties of the flat structured mobile communities, a new network management solution is demanded. The paper presents a distributed network management solution for flat structured mobile communities. Also the paper points out possible network management roles for the different parties (e.g. operators, service

  17. Nematode community structure in a vineyard soil.

    PubMed

    Ferris, H; McKenry, M V

    1976-04-01

    Distribution of the nematode community in a California vineyard was studied over a 13-month period. Omnivorous and microbivorous nematodes were similarly distributed in the root zone, with greatest densities occurring between vine rows and near the soil surface. Greatest densities of plant-parasitic nematodes were found in the vine row, with the individual species differing in their vertical distribution. Total nematode biomass was greatest between rows near the surface. Biomass of plant parasites was greatest in the upper 30 cm of soil in the row, whereas biomass of microbivores was greatest in this region between rows. Of the plant-parasitic nematodes, the variability in distribution among vines was greatest for Paratylenchus hamatus and least for Meloidogyne spp.

  18. The social structure of microbial community involved in colonization resistance.

    PubMed

    He, Xuesong; McLean, Jeffrey S; Guo, Lihong; Lux, Renate; Shi, Wenyuan

    2014-03-01

    It is well established that host-associated microbial communities can interfere with the colonization and establishment of microbes of foreign origins, a phenomenon often referred to as bacterial interference or colonization resistance. However, due to the complexity of the indigenous microbiota, it has been extremely difficult to elucidate the community colonization resistance mechanisms and identify the bacterial species involved. In a recent study, we have established an in vitro mice oral microbial community (O-mix) and demonstrated its colonization resistance against an Escherichia coli strain of mice gut origin. In this study, we further analyzed the community structure of the O-mix by using a dilution/regrowth approach and identified the bacterial species involved in colonization resistance against E. coli. Our results revealed that, within the O-mix there were three different types of bacterial species forming unique social structure. They act as 'Sensor', 'Mediator' and 'Killer', respectively, and have coordinated roles in initiating the antagonistic action and preventing the integration of E. coli. The functional role of each identified bacterial species was further confirmed by E. coli-specific responsiveness of the synthetic communities composed of different combination of the identified players. The study reveals for the first time the sophisticated structural and functional organization of a colonization resistance pathway within a microbial community. Furthermore, our results emphasize the importance of 'Facilitation' or positive interactions in the development of community-level functions, such as colonization resistance.

  19. Climate extremes drive changes in functional community structure.

    PubMed

    Boucek, Ross E; Rehage, Jennifer S

    2014-06-01

    The response of communities to climate extremes can be quite variable. Much of this variation has been attributed to differences in community-specific functional trait diversity, as well as community composition. Yet, few if any studies have explicitly tested the response of the functional trait structure of communities following climate extremes (CEs). Recently in South Florida, two independent, but sequential potential CEs took place, a 2010 cold front, followed by a 2011 drought, both of which had profound impacts on a subtropical estuarine fish community. These CEs provided an opportunity to test whether the structure of South Florida fish communities following each extreme was a result of species-specific differences in functional traits. From historical temperature (1927-2012) and freshwater inflows records into the estuary (1955-2012), we determined that the cold front was a statistically extreme disturbance, while the drought was not, but rather a decadal rare disturbance. The two disturbances predictably affected different parts of functional community structure and thus different component species. The cold front virtually eliminated tropical species, including large-bodied snook, mojarra species, nonnative cichlids, and striped mullet, while having little affect on temperate fishes. Likewise, the drought severely impacted freshwater fishes including Florida gar, bowfin, and two centrarchids, with little effect on euryhaline species. Our findings illustrate the ability of this approach to predict and detect both the filtering effects of different types of disturbances and the implications of the resulting changes in community structure. Further, we highlight the value of this approach to developing predictive frameworks for better understanding community responses to global change. © 2014 John Wiley & Sons Ltd.

  20. Influence of Kuroshio water on the annual copepod community structure in an estuary in the northwest Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Tseng, Li-Chun; Hsiao, Shih-Hui; Sarkar, Santosh Kumar; Bhattacharya, Bhaskar Deb; Chen, Qing-Chao; Hwang, Jiang-Shiou

    2016-04-01

    The influence of Kuroshio water on temporal distribution and copepod diversity was investigated in the Lanyang River estuary (LRE), the longest river in northeast Taiwan, to assess secondary productivity. Zooplankton samples were collected bimonthly from the surface waters (0-2 m) of the estuary during cruises in 2006. Hydrological parameters indicated that the water in the LRE was an admixture of the Lanyang River water and seawater. Among the different genera, 47 copepod species (including 10 species that were identified only to the generic level) belonging to 28 genera, 16 families, and 4 orders were identified. The abundance and proportion of copepods to the total zooplankton counts range from 0 to 3683.42 (304.9±692.7 individuals m-3) and from 0 to 100 (55.09±34.84%) respectively. The copepod community structure revealed a distinct seasonal succession and showed significant differences among the sampling cruises (p<0.05, One-way ANOVA). The 5 most abundant species were Parvocalanus crassirostris (relative abundance [RA]: 50.93%), Pseudodiaptomus serricaudatus (RA: 16.85%), Euterpina acutifrons (RA: 7.34%), Cyclops vicinus (RA: 4.82%), and Microcyclops tricolor (RA: 3.15%). The abundance, species number, indices of richness, evenness, and copepod diversity varied significantly (p<0.05, One-way ANOVA) for all the cruises. Pearson correlation analysis results demonstrated that salinity was positively correlated with the copepod species number (r=0.637), total copepod abundance (r=0.456), and Shannon-Wiener diversity index (r=0.375) with a 1% level of significance. By contrast, the evenness index was negatively correlated with salinity (r=-0.375, p=0.01), indicating that copepod diversity in the LRE was influenced mainly by seawater. The Kuroshio Current played a major role in transporting and distributing warm-water copepods to its affected area. Copepod species assemblages showed seasonal succession and varied drastically with tidal change. The latter

  1. Zooplankton Distribution in Four Western Norwegian Fjords

    NASA Astrophysics Data System (ADS)

    Gorsky, G.; Flood, P. R.; Youngbluth, M.; Picheral, M.; Grisoni, J.-M.

    2000-01-01

    A multi-instrumental array constructed in the Laboratoire d'Ecologie du Plancton Marin in Villefranche sur mer, France, named the Underwater Video Profiler (UVP), was used to investigate the vertical distribution of zooplankton in four western Norwegian fjords in the summer 1996. Six distinct zoological groups were monitored. The fauna included: (a) small crustaceans (mainly copepods), (b) ctenophores (mainly lobates), (c) siphonophores (mainly physonects), (d) a scyphomedusa Periphylla periphylla, (e) chaetognaths and (f) appendicularians. The use of the non-disturbing video technique demonstrated that the distribution of large zooplankton is heterogeneous vertically and geographically. Furthermore, the abundance of non-migrating filter feeders in the deep basins of the fjords indicates that there is enough food (living and non-living particulate organic matter) to support their dietary needs. This adaptation may be considered as a strategy for survival in fjords. Specifically, living in dark, deep water reduces visual predation and population loss encountered in the upper layer due to advective processes.

  2. Temporal Variability of Zooplankton (2000-2013) in the Levantine Sea: Significant Changes Associated to the 2005-2010 EMT-like Event?

    PubMed Central

    Ouba, Anthony; Abboud-Abi Saab, Marie; Stemmann, Lars

    2016-01-01

    In this study, we investigated, for the first time, the potential impact of environmental changes on zooplankton abundance over a fourteen year period (2000–2013) at an offshore station in the Eastern Mediterranean Sea (the Levantine basin, offshore Lebanon). Samples were collected monthly and analyzed using the semi-automated system ZooScan. Salinity, temperature and phytoplankton abundance (nano and microphytoplankton) were also measured. Results show no significant temporal trend in sea surface temperature over the years. Between 2005–2010, salinity in the upper layer (0–80 m) of the Levantine basin increased (~0.3°C). During this 5 year period, total zooplankton abundance significantly increased. These modifications were concomitant to the activation of Aegean Sea as a source of dense water formation as part of the “Eastern Mediterranean Transient-like” event. The results of the present study suggested that zooplankton benefited from enhanced phytoplankton production during the mixing years of the event. Changes in the phenology of some taxa were observed accordingly with a predominantly advanced peak of zooplankton abundance. In conclusion, long-term changes in zooplankton abundance were related to the Levantine thermohaline circulation rather than sea surface warming. Sampling must be maintained to assess the impact of long-term climate change on zooplankton communities. PMID:27459093

  3. Migrant biomass and respiratory carbon flux by zooplankton and micronekton in the subtropical northeast Atlantic Ocean (Canary Islands)

    NASA Astrophysics Data System (ADS)

    Ariza, A.; Garijo, J. C.; Landeira, J. M.; Bordes, F.; Hernández-León, S.

    2015-05-01

    Diel Vertical Migration (DVM) in marine ecosystems is performed by zooplankton and micronekton, promoting a poorly accounted export of carbon to the deep ocean. Major efforts have been made to estimate carbon export due to gravitational flux and to a lesser extent, to migrant zooplankton. However, migratory flux by micronekton has been largely neglected in this context, due to its time-consuming and difficult sampling. In this paper, we evaluated gravitational and migratory flux due to the respiration of zooplankton and micronekton in the northeast subtropical Atlantic Ocean (Canary Islands). Migratory flux was addressed by calculating the biomass of migrating components and measuring the electron transfer system (ETS) activity in zooplankton and dominant species representing micronekton (Euphausia gibboides, Sergia splendens and Lobianchia dofleini). Our results showed similar biomass in both components. The main taxa contributing to DVM within zooplankton were juvenile euphausiids, whereas micronekton were mainly dominated by fish, followed by adult euphausiids and decapods. The contribution to respiratory flux of zooplankton (3.4 ± 1.9 mg C m-2 d-1) was similar to that of micronekton (2.9 ± 1.0 mg C m-2 d-1). In summary, respiratory flux accounted for 53% (range 23-71) of the gravitational flux measured at 150 m depth (11.9 ± 5.8 mg C m-2 d-1). However, based on larger migratory ranges and gut clearance rates, micronekton are expected to be the dominant component that contributes to carbon export in deeper waters. Micronekton estimates in this paper as well as those in existing literature, although variable due to regional differences and difficulties in calculating their biomass, suggest that carbon fluxes driven by this community are important for future models of the biological carbon pump.

  4. Seasonal variations of zooplankton biomass and size-fractionated abundance in relation to environmental changes in a tropical mangrove estuary in the Straits of Malacca.

    PubMed

    Balqis, A R S; Yusoff, F M; Arshad, A; Nishikawa, J

    2016-07-01

    Seasonal variations of zooplankton community in terms of biomass and size-fractionated densities were studied in a tropical Sangga Kechil river, Matang, Perak from June 2010 to April 2011. Zooplankton and jellyfish (hydromedusae, siphonophores and ctenophores) samples were collected bimonthly from four sampling stations by horizontal towing of a 140-?m plankton net and 500 ?m bongo net, respectively. A total of 12 zooplankton groups consisting of six groups each of mesozooplankon (0.2 mm-2.0 mm) and macrozooplankton (2.0 mm-20.0 cm) were recorded. The total zooplankton density (12375?3339 ind m(-3)) and biomass (35.32?14.56 mg m(-3)) were highest during the northeast (NE) monsoon and southwest (SW) monsoon, respectively, indicating the presence of bigger individuals in the latter season. Mesozooplankton predominated (94%) over the macrozooplankton (6%) during all the seasons, and copepods contributed 84% of the total mesozooplankton abundance. Macrozooplankton was dominated by appendicularians during most of the seasons (43%-97%), except during the NE monsoon (December) when chaetognaths became the most abundant (89% of the total macrozooplankton). BIO-ENV analysis showed that total zooplankton density was correlated with turbidity, total nitrogen and total phosphorus, which in turn was positively correlated to chlorophyll a. Cluster analysis of the zooplankton community showed no significant temporal difference between the SW and NE monsoon season during the study period (> 90% similarity). The present study revealed that the zooplankton community in the tropical mangrove estuary in the Straits of Malacca was dominated by mesoplankton, especially copepods.

  5. Bioenergetics modeling of the annual consumption of zooplankton by pelagic fish feeding in the Northeast Atlantic

    PubMed Central

    Utne, Kjell Rong; Jansen, Teunis; Huse, Geir

    2018-01-01

    The present study uses bioenergetics modeling to estimate the annual consumption of the main zooplankton groups by some of the most commercially important planktivorous fish stocks in the Northeast Atlantic, namely Norwegian spring-spawning (NSS) herring (Clupea harengus), blue whiting (Micromesistius poutassou) and NEA mackerel (Scomber scombrus). The data was obtained from scientific surveys in the main feeding area (Norwegian Sea) in the period 2005–2010. By incorporating novel information about ambient temperature, seasonal growth and changes in the diet from stomach content analyses, annual consumption of the different zooplankton groups by pelagic fish is estimated. The present study estimates higher consumption estimates than previous studies for the three species and suggests that fish might have a greater impact on the zooplankton community as foragers. This way, NEA mackerel, showing the highest daily consumption rates, and NSS herring, annually consume around 10 times their total biomass, whereas blue whiting consume about 6 times their biomass in zooplankton. The three species were estimated to consume an average of 135 million (M) tonnes of zooplankton each year, consisting of 53–85 M tonnes of copepods, 20–32 M tonnes of krill, 8–42 M tonnes of appendicularians and 0.2–1.2 M tonnes of fish, depending on the year. For NSS herring and NEA mackerel the main prey groups are calanoids and appendicularians, showing a peak in consumption during June and June–July, respectively, and suggesting high potential for inter-specific feeding competition between these species. In contrast, blue whiting maintain a low consumption rate from April to September, consuming mainly larger euphausiids. Our results suggest that the three species can coexist regardless of their high abundance, zooplankton consumption rates and overlapping diet. Accordingly, the species might have niche segregation, as they are species specific, showing annual and inter

  6. Habitat, topographical, and geographical components structuring shrubsteppe bird communities

    Knick, S.T.; Rotenberry, J.T.; Leu, M.

    2008-01-01

    Landscapes available to birds to select for breeding locations are arrayed along multiple dimensions. Identifying the primary gradients structuring shrubsteppe bird communities in the western United States is important because widespread habitat loss and alteration are shifting the environmental template on which these birds depend. We integrated field habitat surveys, GIS coverages, and bird counts from 61 Breeding Bird Survey routes located in shrubsteppe habitats across a >800 000 km2 region to determine the gradients of habitat, topography, and geography underlying bird communities. A small set of habitat features dominated the primary environmental gradients in a canonical ordination; the 13 species in the shrubsteppe bird community were closely packed along the first two axes. Using hierarchical variance partitioning, we identified habitat as the most important pure (31% explained variation) or shared component. Topography (9%) and geography (4%) were minor components but each shared a larger contribution with habitat (habitat-topography 21%; habitat-geography 22%) in explaining the organization of the bird community. In a second tier partition of habitat structure, pure composition (% land cover) was more important (45%) than configuration (patch size and edge) (7%); the two components shared 27% of the explained variation in the bird community axes. Local (9%), community (14%), and landscape (10%) levels contributed equally. Adjacent organizational levels had a larger shared contribution (local-community 26%; community-landscape 27%) than more separated local-landscape levels (21%). Extensive conversion of shrubsteppe habitats to agriculture, exotic annual grasslands, or pinyon (Pinus spp.)-juniper (Juniperus spp.) woodlands is occurring along the primary axes of habitat structure. Because the shrubsteppe bird community was organized along short gradients dominated by habitat features, relatively small shifts in their available environment will exert a

  7. Contribution and pathways of diazotroph-derived nitrogen to zooplankton during the VAHINE mesocosm experiment in the oligotrophic New Caledonia lagoon

    NASA Astrophysics Data System (ADS)

    Hunt, Brian P. V.; Bonnet, Sophie; Berthelot, Hugo; Conroy, Brandon J.; Foster, Rachel A.; Pagano, Marc

    2016-05-01

    In oligotrophic tropical and subtropical oceans, where strong stratification can limit the replenishment of surface nitrate, dinitrogen (N2) fixation by diazotrophs can represent a significant source of nitrogen (N) for primary production. The VAHINE (VAriability of vertical and tropHIc transfer of fixed N2 in the south-wEst Pacific) experiment was designed to examine the fate of diazotroph-derived nitrogen (DDN) in such ecosystems. In austral summer 2013, three large ( ˜ 50 m3) in situ mesocosms were deployed for 23 days in the New Caledonia lagoon, an ecosystem that typifies the low-nutrient, low-chlorophyll environment, to stimulate diazotroph production. The zooplankton component of the study aimed to measure the incorporation of DDN into zooplankton biomass, and assess the role of direct diazotroph grazing by zooplankton as a DDN uptake pathway. Inside the mesocosms, the diatom-diazotroph association (DDA) het-1 predominated during days 5-15 while the unicellular diazotrophic cyanobacteria UCYN-C predominated during days 15-23. A Trichodesmium bloom was observed in the lagoon (outside the mesocosms) towards the end of the experiment. The zooplankton community was dominated by copepods (63 % of total abundance) for the duration of the experiment. Using two-source N isotope mixing models we estimated a mean ˜ 28 % contribution of DDN to zooplankton nitrogen biomass at the start of the experiment, indicating that the natural summer peak of N2 fixation in the lagoon was already contributing significantly to the zooplankton. Stimulation of N2 fixation in the mesocosms corresponded with a generally low-level enhancement of DDN contribution to zooplankton nitrogen biomass, but with a peak of ˜ 73 % in mesocosm 1 following the UCYN-C bloom. qPCR analysis targeting four of the common diazotroph groups present in the mesocosms (Trichodesmium, het-1, het-2, UCYN-C) demonstrated that all four were ingested by copepod grazers, and that their abundance in copepod

  8. High taxonomic variability despite stable functional structure across microbial communities.

    PubMed

    Louca, Stilianos; Jacques, Saulo M S; Pires, Aliny P F; Leal, Juliana S; Srivastava, Diane S; Parfrey, Laura Wegener; Farjalla, Vinicius F; Doebeli, Michael

    2016-12-05

    Understanding the processes that are driving variation of natural microbial communities across space or time is a major challenge for ecologists. Environmental conditions strongly shape the metabolic function of microbial communities; however, other processes such as biotic interactions, random demographic drift or dispersal limitation may also influence community dynamics. The relative importance of these processes and their effects on community function remain largely unknown. To address this uncertainty, here we examined bacterial and archaeal communities in replicate 'miniature' aquatic ecosystems contained within the foliage of wild bromeliads. We used marker gene sequencing to infer the taxonomic composition within nine metabolic functional groups, and shotgun environmental DNA sequencing to estimate the relative abundances of these groups. We found that all of the bromeliads exhibited remarkably similar functional community structures, but that the taxonomic composition within individual functional groups was highly variable. Furthermore, using statistical analyses, we found that non-neutral processes, including environmental filtering and potentially biotic interactions, at least partly shaped the composition within functional groups and were more important than spatial dispersal limitation and demographic drift. Hence both the functional structure and taxonomic composition within functional groups of natural microbial communities may be shaped by non-neutral and roughly separate processes.

  9. Gap formation following climatic events in spatially structured plant communities

    PubMed Central

    Liao, Jinbao; De Boeck, Hans J.; Li, Zhenqing; Nijs, Ivan

    2015-01-01

    Gaps play a crucial role in maintaining species diversity, yet how community structure and composition influence gap formation is still poorly understood. We apply a spatially structured community model to predict how species diversity and intraspecific aggregation shape gap patterns emerging after climatic events, based on species-specific mortality responses. In multispecies communities, average gap size and gap-size diversity increased rapidly with increasing mean mortality once a mortality threshold was exceeded, greatly promoting gap recolonization opportunity. This result was observed at all levels of species richness. Increasing interspecific difference likewise enhanced these metrics, which may promote not only diversity maintenance but also community invasibility, since more diverse niches for both local and exotic species are provided. The richness effects on gap size and gap-size diversity were positive, but only expressed when species were sufficiently different. Surprisingly, while intraspecific clumping strongly promoted gap-size diversity, it hardly influenced average gap size. Species evenness generally reduced gap metrics induced by climatic events, so the typical assumption of maximum evenness in many experiments and models may underestimate community diversity and invasibility. Overall, understanding the factors driving gap formation in spatially structured assemblages can help predict community secondary succession after climatic events. PMID:26114803

  10. Experimental sulfate amendment alters peatland bacterial community structure.

    PubMed

    Strickman, R J S; Fulthorpe, R R; Coleman Wasik, J K; Engstrom, D R; Mitchell, C P J

    2016-10-01

    As part of a long-term, peatland-scale sulfate addition experiment, the impact of varying sulfate deposition on bacterial community responses was assessed using 16S tag encoded pyrosequencing. In three separate areas of the peatland, sulfate manipulations included an eight year quadrupling of atmospheric sulfate deposition (experimental), a 3-year recovery to background deposition following 5years of elevated deposition (recovery), and a control area. Peat concentrations of methylmercury (MeHg), a bioaccumulative neurotoxin, were measured, the production of which is attributable to a growing list of microorganisms, including many sulfate-reducing Deltaproteobacteria. The total bacterial and Deltaproteobacterial community structures in the experimental treatment differed significantly from those in the control and recovery treatments that were either indistinguishable or very similar to one another. Notably, the relatively rapid return (within three years) of bacterial community structure in the recovery treatment to a state similar to the control, demonstrates significant resilience of the peatland bacterial community to changes in atmospheric sulfate deposition. Changes in MeHg accumulation between sulfate treatments correlated with changes in the Deltaproteobacterial community, suggesting that sulfate may affect MeHg production through changes in the community structure of this group. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Structure of Mesozooplankton Communities in the Coastal Waters of Morocco

    NASA Astrophysics Data System (ADS)

    Lidvanov, V. V.; Grabko, O. G.; Kukuev, E. I.; Korolkova, T. G.

    2018-03-01

    Mero- and holoplanktonic organisms from 23 large taxa have been detected in the coastal waters of Morocco. Seven Cladocera species and 164 Copepoda species were identified. Copepod fauna mostly consisted of oceanic epipelagic widely tropical species, but the constant species group (frequency of occurrence over 50%) included neritic and neritic-oceanic widely tropical species. The neritic community that formed a biotopic association with coastal upwelling waters and the distant-neritic community associated with Canary Current waters were the two major communities detected. The former community was characterized by a high abundance and biomass (5700 ind./m3 and 260 mg/m3) and predominance of neritic species. The trophic structure was dominated by thin filter feeders, mixed-food consumers, and small grabbers; the species structure was dominated by Paracalanus indicus, Acartia clausi, and Oncaea curta; the indices of species diversity (3.07 bit/ind.) and evenness (0.63) were relatively low. The latter community was characterized by low abundance and biomass (1150 ind./m3 and 90 mg/m3); variable biotopic, trophic, and species structure; and higher Shannon indices (3.99 bit/ind.) and Pielou (0.75). Seasonal variation of the abundance of organisms was not detected in the communities. Anomalous mesozooplankton states were observed in summer 1998 and winter 1998-1999.

  12. Observing and modelling phytoplankton community structure in the North Sea

    NASA Astrophysics Data System (ADS)

    Ford, David A.; van der Molen, Johan; Hyder, Kieran; Bacon, John; Barciela, Rosa; Creach, Veronique; McEwan, Robert; Ruardij, Piet; Forster, Rodney

    2017-03-01

    Phytoplankton form the base of the marine food chain, and knowledge of phytoplankton community structure is fundamental when assessing marine biodiversity. Policy makers and other users require information on marine biodiversity and other aspects of the marine environment for the North Sea, a highly productive European shelf sea. This information must come from a combination of observations and models, but currently the coastal ocean is greatly under-sampled for phytoplankton data, and outputs of phytoplankton community structure from models are therefore not yet frequently validated. This study presents a novel set of in situ observations of phytoplankton community structure for the North Sea using accessory pigment analysis. The observations allow a good understanding of the patterns of surface phytoplankton biomass and community structure in the North Sea for the observed months of August 2010 and 2011. Two physical-biogeochemical ocean models, the biogeochemical components of which are different variants of the widely used European Regional Seas Ecosystem Model (ERSEM), were then validated against these and other observations. Both models were a good match for sea surface temperature observations, and a reasonable match for remotely sensed ocean colour observations. However, the two models displayed very different phytoplankton community structures, with one better matching the in situ observations than the other. Nonetheless, both models shared some similarities with the observations in terms of spatial features and inter-annual variability. An initial comparison of the formulations and parameterizations of the two models suggests that diversity between the parameter settings of model phytoplankton functional types, along with formulations which promote a greater sensitivity to changes in light and nutrients, is key to capturing the observed phytoplankton community structure. These findings will help inform future model development, which should be coupled

  13. Arctic complexity: a case study on diel vertical migration of zooplankton

    PubMed Central

    Berge, Jørgen; Cottier, Finlo; Varpe, Øystein; Renaud, Paul E.; Falk-Petersen, Stig; Kwasniewski, Sawomir; Griffiths, Colin; Søreide, Janne E.; Johnsen, Geir; Aubert, Anais; Bjærke, Oda; Hovinen, Johanna; Jung-Madsen, Signe; Tveit, Martha; Majaneva, Sanna

    2014-01-01

    Diel vertical migration (DVM) of zooplankton is a global phenomenon, characteristic of both marine and limnic environments. At high latitudes, patterns of DVM have been documented, but rather little knowledge exists regarding which species perform this ecologically important behaviour. Also, in the Arctic, the vertically migrating components of the zooplankton community are usually regarded as a single sound scattering layer (SSL) performing synchronized patterns of migration directly controlled by ambient light. Here, we present evidence for hitherto unknown complexity of Arctic marine systems, where zooplankton form multiple aggregations through the water column seen via acoustics as distinct SSLs. We show that while the initiation of DVM during the autumnal equinox is light mediated, the vertical positioning of the migrants during day is linked more to the thermal characteristics of water masses than to irradiance. During night, phytoplankton biomass is shown to be the most important factor determining the vertical positioning of all migrating taxa. Further, we develop a novel way of representing acoustic data in the form of a Sound Image (SI) that enables a direct comparison of the relative importance of each potential scatterer based upon the theoretical contribution of their backscatter. Based on our comparison of locations with contrasting hydrography, we conclude that a continued warming of the Arctic is likely to result in more complex ecotones across the Arctic marine system. PMID:25221372

  14. Alternative community structures in a kelp-urchin community: A qualitative modeling approach

    Montano-Moctezuma, G.; Li, H.W.; Rossignol, P.A.

    2007-01-01

    Shifts in interaction patterns within a community may result from periodic disturbances and climate. The question arises as to the extent and significance of these shifting patterns. Using a novel approach to link qualitative mathematical models and field data, namely using the inverse matrix to identify the community matrix, we reconstructed community networks from kelp forests off the Oregon Coast. We simulated all ecologically plausible interactions among community members, selected the models whose outcomes match field observations, and identified highly frequent links to characterize the community network from a particular site. We tested all possible biologically reasonable community networks through qualitative simulations, selected those that matched patterns observed in the field, and further reduced the set of possibilities by retaining those that were stable. We found that a community can be represented by a set of alternative structures, or scenarios. From 11,943,936 simulated models, 0.23% matched the field observations; moreover, only 0.006%, or 748 models, were highly reliable in their predictions and met conditions for stability. Predator-prey interactions as well as non-predatory relationships were consistently found in most of the 748 models. These highly frequent connections were useful to characterize the community network in the study site. We suggest that alternative networks provide the community with a buffer to disturbance, allowing it to continuously reorganize to adapt to a variable environment. This is possible due to the fluctuating capacities of foraging species to consume alternate resources. This suggestion is sustained by our results, which indicate that none of the models that matched field observations were fully connected. This plasticity may contribute to the persistence of these communities. We propose that qualitative simulations represent a powerful technique to raise new hypotheses concerning community dynamics and to

  15. Loss of Rare Fish Species from Tropical Floodplain Food Webs Affects Community Structure and Ecosystem Multifunctionality in a Mesocosm Experiment

    PubMed Central

    Pendleton, Richard M.; Hoeinghaus, David J.; Gomes, Luiz C.; Agostinho, Angelo A.

    2014-01-01

    Experiments with realistic scenarios of species loss from multitrophic ecosystems may improve insight into how biodiversity affects ecosystem functioning. Using 1000 L mesocoms, we examined effects of nonrandom species loss on community structure and ecosystem functioning of experimental food webs based on multitrophic tropical floodplain lagoon ecosystems. Realistic biodiversity scenarios were developed based on long-term field surveys, and experimental assemblages replicated sequential loss of rare species which occurred across all trophic levels of these complex food webs. Response variables represented multiple components of ecosystem functioning, including nutrient cycling, primary and secondary production, organic matter accumulation and whole ecosystem metabolism. Species richness significantly affected ecosystem function, even after statistically controlling for potentially confounding factors such as total biomass and direct trophic interactions. Overall, loss of rare species was generally associated with lower nutrient concentrations, phytoplankton and zooplankton densities, and whole ecosystem metabolism when compared with more diverse assemblages. This pattern was also observed for overall ecosystem multifunctionality, a combined metric representing the ability of an ecosystem to simultaneously maintain multiple functions. One key exception was attributed to time-dependent effects of intraguild predation, which initially increased values for most ecosystem response variables, but resulted in decreases over time likely due to reduced nutrient remineralization by surviving predators. At the same time, loss of species did not result in strong trophic cascades, possibly a result of compensation and complexity of these multitrophic ecosystems along with a dominance of bottom-up effects. Our results indicate that although rare species may comprise minor components of communities, their loss can have profound ecosystem consequences across multiple trophic

  16. Zooplankton Distribution and Species Composition Along an Oxygen Gradient in Puget Sound, WA

    NASA Astrophysics Data System (ADS)

    Keister, J. E.; Essington, T.; Li, L.; Horne, J. K.; Sato, M.; Parker-Stetter, S. L.; Moriarty, P.

    2016-02-01

    Low dissolved oxygen (hypoxia) is one of the most pronounced, pervasive, and significant disturbances in marine ecosystems, yet our understanding of its effects is incomplete, particularly with respect to impacts on lower trophic levels. As part of a study of how hypoxia affects predator-prey relationships and energy flow through marine food webs, we are studying relationships between ocean chemistry and zooplankton in Puget Sound, Washington—a deep, seasonally hypoxic fjord in the Pacific Northwest that supports a productive and diverse pelagic community. From summer through fall in two years that differed in the timing and intensity of hypoxia, we conducted multi-frequency bioacoustic surveys, CTD casts, and depth-stratified zooplankton sampling to examine changes in distribution and species composition of animals in relation to oxygen concentrations. We exploited a natural gradient in oxygen along the axis of the fjord by sampling at moderately hypoxic and normoxic sites with otherwise similar hydrography and species composition to disentangle the effects of oxygen from changes in other environmental factors. Our results support the hypothesis that zooplankton species composition and vertical distributions are altered by hypoxia, but only when examined at the species and life-stage level. Relatively few taxa showed clear responses to hypoxia, and bioacoustic backscatter data (which was dominated by adult euphausiids and amphipods) indicated that those taxa were not affected by the levels of hypoxia we observed. Examination of net tow data revealed more subtle changes, including behavioral avoidance of low oxygen by some copepods and young euphausiid life stages. Overall, the high species diversity and relatively low susceptibility of many zooplankton to hypoxia in Puget Sound may confer ecosystem resilience to near-future projected changes in this region.

  17. [Fungal community structure in phase II composting of Volvariella volvacea].

    PubMed

    Chen, Changqing; Li, Tong; Jiang, Yun; Li, Yu

    2014-12-04

    To understand the fungal community succession during the phase II of Volvariella volvacea compost and clarify the predominant fungi in different fermentation stages, to monitor the dynamic compost at the molecular level accurately and quickly, and reveal the mechanism. The 18S rDNA-denaturing gradient gel electrophoresis (DGGE) and sequencing methods were used to analyze the fungal community structure during the course of compost. The DGGE profile shows that there were differences in the diversity of fungal community with the fermentation progress. The diversity was higher in the stages of high temperature. And the dynamic changes of predominant community and relative intensity was observed. Among the 20 predominant clone strains, 9 were unknown eukaryote and fungi, the others were Eurotiales, Aspergillus sp., Melanocarpus albomyces, Colletotrichum sp., Rhizomucor sp., Verticillium sp., Penicillium commune, Microascus trigonosporus and Trichosporon lactis. The 14 clone strains were detected in the stages of high and durative temperature. The fungal community structure and predominant community have taken dynamic succession during the phase II of Volvariella volvacea compost.

  18. Evidence of community structure in biomedical research grant collaborations.

    PubMed

    Nagarajan, Radhakrishnan; Kalinka, Alex T; Hogan, William R

    2013-02-01

    Recent studies have clearly demonstrated a shift towards collaborative research and team science approaches across a spectrum of disciplines. Such collaborative efforts have also been acknowledged and nurtured by popular extramurally funded programs including the Clinical Translational Science Award (CTSA) conferred by the National Institutes of Health. Since its inception, the number of CTSA awardees has steadily increased to 60 institutes across 30 states. One of the objectives of CTSA is to accelerate translation of research from bench to bedside to community and train a new genre of researchers under the translational research umbrella. Feasibility of such a translation implicitly demands multi-disciplinary collaboration and mentoring. Networks have proven to be convenient abstractions for studying research collaborations. The present study is a part of the CTSA baseline study and investigates existence of possible community-structure in Biomedical Research Grant Collaboration (BRGC) networks across data sets retrieved from the internally developed grants management system, the Automated Research Information Administrator (ARIA) at the University of Arkansas for Medical Sciences (UAMS). Fastgreedy and link-community community-structure detection algorithms were used to investigate the presence of non-overlapping and overlapping community-structure and their variation across years 2006 and 2009. A surrogate testing approach in conjunction with appropriate discriminant statistics, namely: the modularity index and the maximum partition density is proposed to investigate whether the community-structure of the BRGC networks were different from those generated by certain types of random graphs. Non-overlapping as well as overlapping community-structure detection algorithms indicated the presence of community-structure in the BRGC network. Subsequent, surrogate testing revealed that random graph models considered in the present study may not necessarily be appropriate

  19. Community structural characteristics and the adoption of fluoridation.

    PubMed Central

    Smith, R A

    1981-01-01

    A study of community structural characteristics associated with fluoridation outcomes was conducted in 47 communities. A three-part outcome distinction was utilized: communities never having publicly considered the fluoridation issue, those rejecting it, and those accepting it. The independent variables reflect the complexity of the community social and economic structure, social integration, and the centralization of authority. Results of mean comparisons show statistically significant differences between the three outcome types on the independent variables. A series of discriminant analyses provides furtheor evidence of how the independent variables are associated with each outcome type. Non-considering communities are shown to be low in complexity, and high in social integration and the centralization of governmental authority. Rejecters are shown to be high in complexity, but low in social integration and centralized authority. Adopters are relatively high on all three sets of variables. Theretical reasoning is provided to support the hypothesis and why these results are expected. The utility of these results and structural explanations in general are discussed, especially for public/environmental health planning and political activities. PMID:7258427

  20. Microbial Community Structure in Relation to Water Quality in ...

    EPA Pesticide Factsheets

    Weeks Bay is a shallow, microtidal, eutrophic sub-estuary of Mobile Bay, AL. High watershed nutrient inputs to the estuary contribute to a eutrophic condition characterized by frequent summertime diel-cycling hypoxia and dissolved oxygen (DO) oversaturation. Spatial and seasonal variability of microbial communities that contribute to estuarine ecosystem metabolism were characterized using high-throughput DNA sequencing. Surface water samples were collected from spring to fall at three sites along a transect of Weeks Bay from the Fish River to Mobile Bay. Water samples were analyzed for physiochemical properties and were also filtered onto Sterivex filters for DNA extraction. Genes for 16S rRNA and 18S rRNA were amplified and sequenced according to Earth Microbiome Project protocols. Sequences were assembled into contigs and clustered into OTUs with mothur using the Silva database. The prokaryotes were dominated by Cyanobacteria, Actinobacteria, and Spartobacteria, whereas the eukaryotes were dominated by Bacillariophyta (diatoms). Multivariate statistical analysis of microbial community composition and environmental data showed that Bacteria, Archaea and Eukaryota were clustered by season. BEST analysis by station showed that prokaryotic community structure was associated with salinity and CDOM (Rho=0.924), whereas eukaryotic community structure was most associated with salinity (Rho=0.846). Prokaryotic community structure within seasons was associated with six

  1. Functional and phylogenetic structure of island bird communities.

    PubMed

    Si, Xingfeng; Cadotte, Marc W; Zeng, Di; Baselga, Andrés; Zhao, Yuhao; Li, Jiaqi; Wu, Yiru; Wang, Siyu; Ding, Ping

    2017-05-01

    Biodiversity change in anthropogenically transformed habitats is often nonrandom, yet the nature and importance of the different mechanisms shaping community structure are unclear. Here, we extend the classic Theory of Island Biogeography (TIB) to account for nonrandom processes by incorporating species traits and phylogenetic relationships into a study of faunal relaxation following habitat loss and fragmentation. Two possible mechanisms can create nonrandom community patterns on fragment islands. First, small and isolated islands might consist of similar or closely related species because they are environmentally homogeneous or select for certain shared traits, such as dispersal ability. Alternatively, communities on small islands might contain more dissimilar or distantly related species than on large islands because limited space and resource availability result in greater competitive exclusion among species with high niche overlap. Breeding birds were surveyed on 36 islands and two mainland sites annually from 2010 to 2014 in the Thousand Island Lake region, China. We assessed community structure of breeding birds on these subtropical land-bridge islands by integrating species' trait and evolutionary distances. We additionally analysed habitat heterogeneity and variance in size ratios to distinguish biotic and abiotic processes of community assembly. Results showed that functional-phylogenetic diversity increased with island area, and decreased with isolation. Bird communities on the mainland were more diverse and generally less clustered than island bird communities and not different than randomly assembled communities. Bird communities on islands tend to be functionally similar and phylogenetically clustered, especially on small and isolated islands. The nonrandom decline in species diversity and change in bird community structure with island area and isolation, along with the relatively homogeneous habitats on small islands, support the environmental

  2. Community Structure in Social Networks: Applications for Epidemiological Modelling

    PubMed Central

    Kitchovitch, Stephan; Liò, Pietro

    2011-01-01

    During an infectious disease outbreak people will often change their behaviour to reduce their risk of infection. Furthermore, in a given population, the level of perceived risk of infection will vary greatly amongst individuals. The difference in perception could be due to a variety of factors including varying levels of information regarding the pathogen, quality of local healthcare, availability of preventative measures, etc. In this work we argue that we can split a social network, representing a population, into interacting communities with varying levels of awareness of the disease. We construct a theoretical population and study which such communities suffer most of the burden of the disease and how their awareness affects the spread of infection. We aim to gain a better understanding of the effects that community-structured networks and variations in awareness, or risk perception, have on the disease dynamics and to promote more community-resolved modelling in epidemiology. PMID:21789238

  3. Temporal variations in a phytoplankton community in a subtropical reservoir: An interplay of extrinsic and intrinsic community effects.

    PubMed

    Yang, Wen; Zheng, Zhongming; Zheng, Cheng; Lu, Kaihong; Ding, Dewen; Zhu, Jinyong

    2018-01-15

    The phytoplankton community structure is potentially influenced by both extrinsic effects originating from the surrounding environment and intrinsic effects relying on interspecific interactions between two species. However, few studies have simultaneously considered both types of effects and assessed the relative importance of these factors. In this study, we used data collected over nine months (August 2012-May 2013) from a typical subtropical reservoir in southeast China to analyze the temporal variation of its phytoplankton community structure and develop a quantitative understanding of the extrinsic and intrinsic effects on phytoplankton community dynamics. Significant temporal variations were observed in environmental variables as well as the phytoplankton and zooplankton communities, whereas their variational trajectories and directions were entirely different. Variance partitioning analysis showed that extrinsic factors significantly explained only 31% of the variation in the phytoplankton community, thus suggesting that these factors were incomplete predictors of the community structure. Random forest-based models showed that 48% of qualified responsible phytoplankton species were more accurately predicted by phytoplankton-only models, which revealed clear effects of interspecific species-to-species interactions. Furthermore, we used association networks to model the interactions among phytoplankton, zooplankton and the environment. Network comparisons indicated that interspecific interactions were widely present in the phytoplankton community and dominated the network rather than those between phytoplankton and extrinsic factors. These findings expand the current understanding of the underlying mechanisms that govern phytoplankton community dynamics. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Stable pelagic vertebrate community structure through extreme Paleogene greenhouse conditions

    NASA Astrophysics Data System (ADS)

    Sibert, E. C.; Friedman, M.; Hull, P. M.; Hunt, G.; Norris, R. D.

    2016-02-01

    The species composition (structure) and energy transfer (function) of an ecosystem is reflected by the presence and type of consumers that it supports. Here we use ichthyoliths, microfossil fish teeth and shark denticles, to assess the ecological variability of the pelagic fish community structure and composition from the Late Cretaceous to the middle Eocene from a drill core in the South Pacific gyre (DSDP Site 596). We find that the overall vertebrate community structure, as measured by the relative abundance of sharks to ray-finned fishes, has a punctuated change at the Cretaceous/Paleogene mass extinction. The vertebrate community structure remained stable throughout the Paleogene despite a five-fold increase in overall abundance of ichthyoliths during the extreme greenhouse of the Early Eocene. Further, we use a novel system to quantify the morphological variation in fish teeth. We find that the morphospace occupied by the tooth assemblage is conserved throughout the interval, with a slight expansion following the Cretaceous-Paleogene mass extinction, and the evolution of a distinct morphotype-group around the Paleocene-Eocene boundary. While there are elevated rates of morphotype origination and extinction following the Cretaceous-Paleogene mass extinction, the extreme greenhouse warming of the Early Eocene and associated increase in fish production produce near-zero origination and extinction rates. The relative stability in composition of the pelagic vertebrate community during intervals of extreme climate change and across large ranges of total fish accumulation, suggests that pelagic ecosystem structure is robust to climate events, and that the overall structure of the pelagic fish community may be decoupled from both climate and ecosystem function.

  5. Extinction order and altered community structure rapidly disrupt ecosystem functioning.

    PubMed

    Larsen, Trond H; Williams, Neal M; Kremen, Claire

    2005-05-01

    By causing extinctions and altering community structure, anthropogenic disturbances can disrupt processes that maintain ecosystem integrity. However, the relationship between community structure and ecosystem functioning in natural systems is poorly understood. Here we show that habitat loss appeared to disrupt ecosystem functioning by affecting extinction order, species richness and abundance. We studied pollination by bees in a mosaic of agricultural and natural habitats in California and dung burial by dung beetles on recently created islands in Venezuela. We found that large-bodied bee and beetle species tended to be both most extinction-prone and most functionally efficient, contributing to rapid functional loss. Simulations confirmed that extinction order led to greater disruption of function than predicted by random species loss. Total abundance declined with richness and also appeared to contribute to loss of function. We demonstrate conceptually and empirically how the non-random response of communities to disturbance can have unexpectedly large functional consequences.

  6. Falling palm fronds structure amazonian rainforest sapling communities.

    PubMed

    Peters, Halton A; Pauw, Anton; Silman, Miles R; Terborgh, John W

    2004-08-07

    The senescence and loss of photosynthetic and support structures is a nearly universal aspect of tree life history, and can be a major source of disturbance in forest understoreys, but the ability of falling canopy debris in determining the stature and composition of understorey communities seems not to have been documented. In this study, we show that senescent fronds of the palm Iriartea deltoidea cause substantial disturbance in tropical forest sapling communities. This disturbance influences the species composition of the canopy and subcanopy by acting as an ecological filter, favouring sapling species with characteristics conducive to recovery after physical damage. The scale of this dominance suggests that falling I. deltoidea debris may be influencing sapling community structure and species composition in Amazonian rainforests over very large spatial scales.

  7. Use of zooplankton to assess the movement and distribution of alewife (Alosa pseudoharengus) in south-central Lake Ontario in spring

    O'Gorman, Robert; Mills, Edward L.; DeGisi, Joe

    1991-01-01

    Data from assessments of fish and zooplankton conducted during April and May-June 1986-88 in south-central Lake Ontario were examined for evidence that zooplankton size structure can be used to follow the movement of alewife (Alosa pseudoharengus). The spring influx of alewife into nearshore waters was linked with water temperature and coincided with a decline in the mean length of crustacean zooplankton and the virtual disappearance of zooplankters a?Y 0.9 mm. Alewife moving inshore to spawn fed heavily on the largest zooplankters, negating the possibility that changes in zooplankton size were wholly a response to seasonal recruitment as waters warm and the competition shifts to Bosmina. Offshore, there was usually no significant (P < 0.05) change in mean lengths of zooplankton in the upper water column between April and May-June, and zooplankters a?Y 0.9 mm always remained abundant, suggesting that few alewife were there from April through mid-June. We conclude that in large freshwater lakes where a planktivore is abundant, yet spatially concentrated, changes in size of crustacean zooplankton can facilitate understanding of the fish's movement and distribution.

  8. Mission and Structure: The Community College in a Global Context.

    ERIC Educational Resources Information Center

    Levin, John S.

    This is an investigation of globalization and its effects upon seven community colleges in Canada and the U.S. As a study of organizational change, the investigation addresses the alteration of processes and structures over the 1990s, brought about in part by globalization and institutional responses to globalization. This report has 11 chapters,…

  9. Family Structure, Community Context, and Adolescent Problem Behaviors

    ERIC Educational Resources Information Center

    Hoffman, John P.

    2006-01-01

    A number of models have been proposed to explain the relationship between family structure and adolescent problem behaviors, including several that consider parent-child relations, family income, stress, and residential mobility. However, studies have not explored whether the different types of communities within which families reside affect the…

  10. Changes in Age Structure and Rural Community Growth.

    ERIC Educational Resources Information Center

    McGranahan, David A.

    1985-01-01

    Whatever migration patterns evolve, changes in the age structure mean that rural communities in general can expect fairly stable elementary school population, reduced high school population, slower growth in new business and employment, and continued increase in the elderly population. (JHZ)

  11. An Investigation of the Normative Structure for Community College Students

    ERIC Educational Resources Information Center

    Akin, Selenia Renea

    2010-01-01

    This exploratory study was designed to determine if a normative structure exists among a community college student body by extending the work of Caboni, Braxton, Deusterhous, Mundy, McClendon, and Lee (2005). The study also sought to determine if the level of espousal for the norms differed across student characteristics. This study analyzed data…

  12. Changes in Soil Microbial Community Structure with Flooding

    Flooding disturbs both above- and below-ground ecosystem processes. Although often ignored, changes in below-ground environments are no less important than those that occur above-ground. Shifts in soil microbial community structure are expected when anaerobic conditions develop from flooding. The ...

  13. Detecting Habitats and Ecosystem Functions Considering the Mesozooplankton Size and Diversity Structures and Environmental Conditions in the Gulf of Lion, NW Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Carlotti, F.; Espinasse, B.; Zhou, M.; Jean-Luc, D.

    2016-02-01

    Environmental conditions and zooplankton size structure and taxonomic diversity were investigated in the Gulf of Lion in May 2010 and January 2011. The integrated physical and biological measurements provided a 3D view with high spatial resolution of the physical and biological variables and their correlations over the whole gulf. The effects of physical processes such as freshwater input, coastal upwelling, and water column mixing by winds on phytoplankton and zooplankton distributions were analyzed using these data. Several analytic tests were performed in order to define several ecoregions representing different habitats of plankton communities. Three habitats were distinguished based on statistical analysis performed on biological and physical variables: (1) the coastal area characterized by shallow waters, high chl a concentrations, and a steep slope of the normalized biomass size spectrum (NBSS); (2) the area affected by the Rhône with high stratification and flat NBSS slope; and (3) the continental shelf with a deep mixed layer, relatively low particle concentrations, and moderate NBSS slope. The zooplankton diversity was characterized by spatial differences in community composition among the Rhône plume area, the coastal shelf, and shelf break waters. Defining habitat is a relevant approach to designing new zooplankton sampling strategies, validating distribution models and including the zooplankton compartment in trophodynamic studies.

  14. Seasonal zooplankton dynamics in Lake Michigan: disentangling impacts of resource limitation, ecosystem engineering, and predation during a critical ecosystem transition

    Vanderploeg, Henry A.; Pothoven, Steven A.; Fahnenstiel, Gary L.; Cavaletto, Joann F.; Liebig, James R.; Stow, Craig Stow; Nalepa, Thomas F.; Madenjian, Charles P.; Bunnell, David B.

    2012-01-01

    We examined seasonal dynamics of zooplankton at an offshore station in Lake Michigan from 1994 to 2003 and 2007 to 2008. This period saw variable weather, declines in planktivorous fish abundance, the introduction and expansion of dreissenid mussels, and a slow decline in total phosphorus concentrations. After the major expansion of mussels into deep water (2007–2008), chlorophyll in spring declined sharply, Secchi depth increased markedly in all seasons, and planktivorous fish biomass declined to record-low levels. Overlaying these dramatic ecosystem-level changes, the zooplankton community exhibited complex seasonal dynamics between 1994–2003 and 2007–2008. Phenology of the zooplankton maximum was affected by onset of thermal stratification, but there was no other discernable effect due to temperature. Interannual variability in zooplankton biomass during 1994 and 2003 was strongly driven by planktivorous fish abundance, particularly age-0 and age-1 alewives. In 2007–2008, there were large decreases in Diacyclops thomasi and Daphnia mendotae possibly caused by food limitation as well as increased predation and indirect negative effects from increases in Bythotrephes longimanus abundance and in foraging efficiency associated with increased light penetration. The Bythotrephes increase was likely driven in part by decreased predation from yearling and older alewife. While there was a major decrease in epilimnetic–metalimnetic herbivorous cladocerans in 2007–2008, there was an increase in large omnivorous and predacious calanoid copepods, especially those in the hypolimnion. Thus, changes to the zooplankton community are the result of cascading, synergistic interactions, including a shift from vertebrate to invertebrate planktivory and mussel ecosystem impacts on light climate and chlorophyll.

  15. Global dynamics of zooplankton and harmful algae in flowing habitats

    NASA Astrophysics Data System (ADS)

    Hsu, Sze-Bi; Wang, Feng-Bin; Zhao, Xiao-Qiang

    This paper is devoted to the study of two advection-dispersion-reaction models arising from the dynamics of harmful algae and zooplankton in flowing-water habitats where a main channel is coupled to a hydraulic storage zone, representing an ensemble of fringing coves on the shoreline. For the system modeling the dynamics of algae and their toxin that contains little limiting nutrient, we establish a threshold type result on the global attractivity in terms of the basic reproduction ratio for algae. For the model with zooplankton that eat the algae and are inhibited by the toxin produced by algae, we show that there exists a coexistence steady state and the zooplankton is uniformly persistent provided that two basic reproduction ratios for algae and zooplankton are greater than unity.

  16. Multilabel user classification using the community structure of online networks

    PubMed Central

    Papadopoulos, Symeon; Kompatsiaris, Yiannis

    2017-01-01

    We study the problem of semi-supervised, multi-label user classification of networked data in the online social platform setting. We propose a framework that combines unsupervised community extraction and supervised, community-based feature weighting before training a classifier. We introduce Approximate Regularized Commute-Time Embedding (ARCTE), an algorithm that projects the users of a social graph onto a latent space, but instead of packing the global structure into a matrix of predefined rank, as many spectral and neural representation learning methods do, it extracts local communities for all users in the graph in order to learn a sparse embedding. To this end, we employ an improvement of personalized PageRank algorithms for searching locally in each user’s graph structure. Then, we perform supervised community feature weighting in order to boost the importance of highly predictive communities. We assess our method performance on the problem of user classification by performing an extensive comparative study among various recent methods based on graph embeddings. The comparison shows that ARCTE significantly outperforms the competition in almost all cases, achieving up to 35% relative improvement compared to the second best competing method in terms of F1-score. PMID:28278242

  17. A framework for solving ill-structured community problems

    NASA Astrophysics Data System (ADS)

    Keller, William Cotesworth

    A multifaceted protocol for solving ill-structured community problems has been developed. It embodies the lessons learned from the past by refining and extending features of previous models from the systems thinkers, and the fields of behavioral decision making and creative problem solving. The protocol also embraces additional features needed to address the unique aspects of community decision situations. The essential elements of the protocol are participants from the community, a problem-solving process, a systems picture, a facilitator, a modified Delphi method of communications, and technical expertise. This interdisciplinary framework has been tested by a quasi experiment with a real world community problem (the high cost of electrical power on Long Island, NY). Results indicate the protocol can enable members of the community to understand a complicated, ill-structured problem and guide them to action to solve the issue. However, the framework takes time (over one year in the test case) and will be inappropriate for crises where quick action is needed.

  18. Multilabel user classification using the community structure of online networks.

    PubMed

    Rizos, Georgios; Papadopoulos, Symeon; Kompatsiaris, Yiannis

    2017-01-01

    We study the problem of semi-supervised, multi-label user classification of networked data in the online social platform setting. We propose a framework that combines unsupervised community extraction and supervised, community-based feature weighting before training a classifier. We introduce Approximate Regularized Commute-Time Embedding (ARCTE), an algorithm that projects the users of a social graph onto a latent space, but instead of packing the global structure into a matrix of predefined rank, as many spectral and neural representation learning methods do, it extracts local communities for all users in the graph in order to learn a sparse embedding. To this end, we employ an improvement of personalized PageRank algorithms for searching locally in each user's graph structure. Then, we perform supervised community feature weighting in order to boost the importance of highly predictive communities. We assess our method performance on the problem of user classification by performing an extensive comparative study among various recent methods based on graph embeddings. The comparison shows that ARCTE significantly outperforms the competition in almost all cases, achieving up to 35% relative improvement compared to the second best competing method in terms of F1-score.

  19. A clustering algorithm for determining community structure in complex networks

    NASA Astrophysics Data System (ADS)

    Jin, Hong; Yu, Wei; Li, ShiJun

    2018-02-01

    Clustering algorithms are attractive for the task of community detection in complex networks. DENCLUE is a representative density based clustering algorithm which has a firm mathematical basis and good clustering properties allowing for arbitrarily shaped clusters in high dimensional datasets. However, this method cannot be directly applied to community discovering due to its inability to deal with network data. Moreover, it requires a careful selection of the density parameter and the noise threshold. To solve these issues, a new community detection method is proposed in this paper. First, we use a spectral analysis technique to map the network data into a low dimensional Euclidean Space which can preserve node structural characteristics. Then, DENCLUE is applied to detect the communities in the network. A mathematical method named Sheather-Jones plug-in is chosen to select the density parameter which can describe the intrinsic clustering structure accurately. Moreover, every node on the network is meaningful so there were no noise nodes as a result the noise threshold can be ignored. We test our algorithm on both benchmark and real-life networks, and the results demonstrate the effectiveness of our algorithm over other popularity density based clustering algorithms adopted to community detection.

  20. Structure of Benthic Communities along the Taiwan Latitudinal Gradient

    PubMed Central

    De Palmas, Stéphane; Kuo, Chao-Yang; Hsieh, Hernyi Justin; Chen, Chaolun Allen

    2016-01-01

    The distribution and the structure of benthic assemblages vary with latitude. However, few studies have described benthic communities along large latitudinal gradients, and patterns of variation are not fully understood. Taiwan, lying between 21.90°N and 25.30°N, is located at the center of the Philippine-Japan arc and lies at the northern margin of coral reef development. A wide range of habitats is distributed along this latitudinal gradient, from extensive fringing coral reefs at the southern coast to non-reefal communities at the north. In this study, we examined the structure of benthic communities around Taiwan, by comparing its assemblages in four regions, analyzing the effects of the latitudinal gradient, and highlighting regional characteristics. A total of 25 sites, 125 transects, and 2,625 photographs were used to analyze the benthic communities. Scleractinian corals present an obvious gradient of increasing diversity from north to south, whereas macro-algae diversity is higher on the north-eastern coast. At the country scale, Taiwanese coral communities were dominated by turf algae (49%). At the regional scale, we observed an important heterogeneity that may be caused by local disturbances and habitat degradation that smooths out regional differences. In this context, our observations highlight the importance of managing local stressors responsible for reef degradation. Overall, this study provides an important baseline upon which future changes in benthic assemblages around Taiwan can be assessed. PMID:27513665

  1. Plankton community structure and connectivity in the Kimberley-Browse region of NW Australia

    NASA Astrophysics Data System (ADS)

    McKinnon, A. D.; Duggan, S.; Holliday, D.; Brinkman, R.

    2015-02-01

    We describe the zooplankton and ichthyoplankton communities of coastal waters of the Kimberley coast (North West Australia), sampled in macrotidal Camden Sound during both the wet and dry seasons of 2011, and compare these to six other Kimberley embayments during the wet season of 2013. Zooplankton abundance in Camden Sound was 7038 ± 3913 SD ind. m-3 in the wet season and 1892 ± 708 SD ind. m-3 in the dry season, with copepods accounting for 85% by number. In all, 78 species of copepods were recorded, with the families Paracalanidae and Oithonidae dominant. In Camden Sound, 48 families of larval fish occurred, with ichthyoplankton more abundant in the wet season than the dry season (1.16 ± 0.2 ind. m-3 cf 0.76 ± 0.2 ind. m-3). Larval gobiids (Subfamily Gobiinae) were most abundant, with other common families associated with either pelagic or soft-bottom habitats as adults. Multivariate analyses of both copepod and ichthyoplankton communities demonstrated strong seasonal contrasts, although an along-shelf gradient in copepod community composition was apparent along the embayments sampled in 2013. There was little spatial variation in plankton communities within Camden Sound as a result of the large tidal range (up to 11.7 m, with 2.5 m-1 velocities), although gradients in abundance and composition on cross-shelf transects occurred in the more northern embayments that had a lower tidal range, such as Napier Broome Bay. Copepod communities of the Kimberley-Browse region were placed in regional perspective by multivariate analyses of similar data collected in the eastern Indian Ocean at Scott Reef, in the Arafura Sea and on the southern North West (NW) shelf. The plankton communities of the NW shelf form a series of along-shore metacommunities linked by advection, with weaker cross-shelf connectivity. The presence of the larvae of mesopelagic fishes of the family Myctophidae in coastal waters confirms seasonal cross-shelf connectivity.

  2. Governance and Management Structures for Community Partnerships: Experiences from the Robert Wood Johnson Foundation's Community Partnerships for Older Adults Program

    ERIC Educational Resources Information Center

    Bolda, Elise J.; Saucier, Paul; Maddux, George L.; Wetle, Terrie; Lowe, Jane Isaacs

    2006-01-01

    Purpose: This article describes early efforts of four community partnerships in Boston, El Paso, Houston, and Milwaukee to address governance and management structures in ways that promote the sustainability of innovative community-based long-term care system improvements. The four communities are grantees of the Community Partnerships for Older…

  3. Changes in soil bacterial community structure with increasing disturbance frequency.

    PubMed

    Kim, Mincheol; Heo, Eunjung; Kang, Hojeong; Adams, Jonathan

    2013-07-01

    Little is known of the responsiveness of soil bacterial community structure to disturbance. In this study, we subjected a soil microcosm to physical disturbance, sterilizing 90 % of the soil volume each time, at a range of frequencies. We analysed the bacterial community structure using 454 pyrosequencing of the 16S rRNA gene. Bacterial diversity was found to decline with the increasing disturbance frequencies. Total bacterial abundance was, however, higher at intermediate and high disturbance frequencies, compared to low and no-disturbance treatments. Changing disturbance frequency also led to changes in community composition, with changes in overall species composition and some groups becoming abundant at the expense of others. Some phylogenetic groups were found to be relatively more disturbance-sensitive or tolerant than others. With increasing disturbance frequency, phylogenetic species variability (an index of community composition) itself became more variable from one sample to another, suggesting a greater role of chance in community composition. Compared to the tightly clustered community of the original undisturbed soil, in all the aged disturbed soils the lists of most abundant operational taxonomic units (OTUs) in each replicate were very different, suggesting a possible role of stochasticity in resource colonization and exploitation in the aged and disturbed soils. For example, colonization may be affected by whichever localized concentrations of bacterial populations happen to survive the last disturbance and be reincorporated in abundance into each pot. Overall, it appears that the soil bacterial community is very sensitive to physical disturbance, losing diversity, and that certain groups have identifiable 'high disturbance' vs. 'low disturbance' niches.

  4. Correlations between Community Structure and Link Formation in Complex Networks

    PubMed Central

    Liu, Zhen; He, Jia-Lin; Kapoor, Komal; Srivastava, Jaideep

    2013-01-01

    Background Links in complex networks commonly represent specific ties between pairs of nodes, such as protein-protein interactions in biological networks or friendships in social networks. However, understanding the mechanism of link formation in complex networks is a long standing challenge for network analysis and data mining. Methodology/Principal Findings Links in complex networks have a tendency to cluster locally and form so-called communities. This widely existed phenomenon reflects some underlying mechanism of link formation. To study the correlations between community structure and link formation, we present a general computational framework including a theory for network partitioning and link probability estimation. Our approach enables us to accurately identify missing links in partially observed networks in an efficient way. The links having high connection likelihoods in the communities reveal that links are formed preferentially to create cliques and accordingly promote the clustering level of the communities. The experimental results verify that such a mechanism can be well captured by our approach. Conclusions/Significance Our findings provide a new insight into understanding how links are created in the communities. The computational framework opens a wide range of possibilities to develop new approaches and applications, such as community detection and missing link prediction. PMID:24039818

  5. Oceanographic structure drives the assembly processes of microbial eukaryotic communities.

    PubMed

    Monier, Adam; Comte, Jérôme; Babin, Marcel; Forest, Alexandre; Matsuoka, Atsushi; Lovejoy, Connie

    2015-03-17

    Arctic Ocean microbial eukaryote phytoplankton form subsurface chlorophyll maximum (SCM), where much of the annual summer production occurs. This SCM is particularly persistent in the Western Arctic Ocean, which is strongly salinity stratified. The recent loss of multiyear sea ice and increased particulate-rich river discharge in the Arctic Ocean results in a greater volume of fresher water that may displace nutrient-rich saltier waters to deeper depths and decrease light penetration in areas affected by river discharge. Here, we surveyed microbial eukaryotic assemblages in the surface waters, and within and below the SCM. In most samples, we detected the pronounced SCM that usually occurs at the interface of the upper mixed layer and Pacific Summer Water (PSW). Poorly developed SCM was seen under two conditions, one above PSW and associated with a downwelling eddy, and the second in a region influenced by the Mackenzie River plume. Four phylogenetically distinct communities were identified: surface, pronounced SCM, weak SCM and a deeper community just below the SCM. Distance-decay relationships and phylogenetic structure suggested distinct ecological processes operating within these communities. In the pronounced SCM, picophytoplanktons were prevalent and community assembly was attributed to water mass history. In contrast, environmental filtering impacted the composition of the weak SCM communities, where heterotrophic Picozoa were more numerous. These results imply that displacement of Pacific waters to greater depth and increased terrigenous input may act as a control on SCM development and result in lower net summer primary production with a more heterotroph dominated eukaryotic microbial community.

  6. Fishing degrades size structure of coral reef fish communities.

    PubMed

    Robinson, James P W; Williams, Ivor D; Edwards, Andrew M; McPherson, Jana; Yeager, Lauren; Vigliola, Laurent; Brainard, Russell E; Baum, Julia K

    2017-03-01

    Fishing pressure on coral reef ecosystems has been frequently linked to reductions of large fishes and reef fish biomass. Associated impacts on overall community structure are, however, less clear. In size-structured aquatic ecosystems, fishing impacts are commonly quantified using size spectra, which describe the distribution of individual body sizes within a community. We examined the size spectra and biomass of coral reef fish communities at 38 US-affiliated Pacific islands that ranged in human presence from near pristine to human population centers. Size spectra 'steepened' steadily with increasing human population and proximity to market due to a reduction in the relative biomass of large fishes and an increase in the dominance of small fishes. Reef fish biomass was substantially lower on inhabited islands than uninhabited ones, even at inhabited islands with the lowest levels of human presence. We found that on populated islands size spectra exponents decreased (analogous to size spectra steepening) linearly with declining biomass, whereas on uninhabited islands there was no relationship. Size spectra were steeper in regions of low sea surface temperature but were insensitive to variation in other environmental and geomorphic covariates. In contrast, reef fish biomass was highly sensitive to oceanographic conditions, being influenced by both oceanic productivity and sea surface temperature. Our results suggest that community size structure may be a more robust indicator than fish biomass to increasing human presence and that size spectra are reliable indicators of exploitation impacts across regions of different fish community compositions, environmental drivers, and fisheries types. Size-based approaches that link directly to functional properties of fish communities, and are relatively insensitive to abiotic variation across biogeographic regions, offer great potential for developing our understanding of fishing impacts in coral reef ecosystems. © 2016

  7. Experimental whole-stream warming alters community size structure.

    PubMed

    Nelson, Daniel; Benstead, Jonathan P; Huryn, Alexander D; Cross, Wyatt F; Hood, James M; Johnson, Philip W; Junker, James R; Gíslason, Gísli M; Ólafsson, Jón S

    2017-07-01

    How ecological communities respond to predicted increases in temperature will determine the extent to which Earth's biodiversity and ecosystem functioning can be maintained into a warmer future. Warming is predicted to alter the structure of natural communities, but robust tests of such predictions require appropriate large-scale manipulations of intact, natural habitat that is open to dispersal processes via exchange with regional species pools. Here, we report results of a two-year whole-stream warming experiment that shifted invertebrate assemblage structure via unanticipated mechanisms, while still conforming to community-level metabolic theory. While warming by 3.8 °C decreased invertebrate abundance in the experimental stream by 60% relative to a reference stream, total invertebrate biomass was unchanged. Associated shifts in invertebrate assemblage structure were driven by the arrival of new taxa and a higher proportion of large, warm-adapted species (i.e., snails and predatory dipterans) relative to small-bodied, cold-adapted taxa (e.g., chironomids and oligochaetes). Experimental warming consequently shifted assemblage size spectra in ways that were unexpected, but consistent with thermal optima of taxa in the regional species pool. Higher temperatures increased community-level energy demand, which was presumably satisfied by higher primary production after warming. Our experiment demonstrates how warming reassembles communities within the constraints of energy supply via regional exchange of species that differ in thermal physiological traits. Similar responses will likely mediate impacts of anthropogenic warming on biodiversity and ecosystem function across all ecological communities. © 2016 John Wiley & Sons Ltd.

  8. Carbendazim induces a temporary change in soil bacterial community structure.

    PubMed

    Wang, Xiuguo; Song, Min; Gao, Chunming; Dong, Bin; Zhang, Qun; Fang, Hua; Yu, Yunlong

    2009-01-01

    The effect of carbendazim applications on the diversity and structure of a soil bacterial community was studied under field conditions using temperature gradient gel electrophoresis (TGGE) and partial sequence analysis of PCR-amplified 16S rRNA gene. After four successive introductions of carbendazim at a level of 0.94 kg active ingredient (a.i.)/ha, the genetic diversity (expressed as Shannon index, H') decreased from 1.43 in the control to 1.29 in treated soil. This harmful effect seems to increase with the concentration of carbendazim. The value of H' in the soil treated with carbendazim at 4.70 kg a.i./ha was reduced to 1.05 (P < or = 0.05). The structure of soil bacterial community was also affected after four repeated applications of carbendazim at levels of 0.94, 1.88 and 4.70 kg a.i./ha, as seen in the relative intensities of the individual band. However, the bacterial community in carbendazim-treated soil recovered to that in the control 360 d after the first treatment. The results indicated that repeated applications of carbendazim could reduce soil microbial diversity and alter the bacterial community structure temporarily.

  9. How mammalian predation contributes to tropical tree community structure.

    PubMed

    Paine, C E Timothy; Beck, Harald; Terborgh, John

    2016-12-01

    The recruitment of seedlings from seeds is the key demographic transition for rain forest trees. Though tropical forest mammals are known to consume many seeds, their effects on tree community structure remain little known. To evaluate their effects, we monitored 8,000 seeds of 24 tree species using exclosure cages that were selectively permeable to three size classes of mammals for up to 4.4 years. Small and medium-bodied mammals removed many more seeds than did large mammals, and they alone generated beta diversity and negative density dependence, whereas all mammals reduced diversity and shaped local species composition. Thus, small and medium-bodied mammals more strongly contributed to community structure and promoted species coexistence than did large mammals. Given that seedling recruitment is seed limited for most species, alterations to the composition of the community of mammalian seed predators is expected to have long-term consequences for tree community structure in tropical forests. © 2016 by the Ecological Society of America.

  10. The Influence of Individual Variability on Zooplankton Population Dynamics under Different Environmental Conditions

    NASA Astrophysics Data System (ADS)

    Bi, R.; Liu, H.

    2016-02-01

    Understanding how biological components respond to environmental changes could be insightful to predict ecosystem trajectories under different climate scenarios. Zooplankton are key components of marine ecosystems and changes in their dynamics could have major impact on ecosystem structure. We developed an individual-based model of a common coastal calanoid copepod Acartia tonsa to examine how environmental factors affect zooplankton population dynamics and explore the role of individual variability in sustaining population under various environmental conditions consisting of temperature, food concentration and salinity. Total abundance, egg production and proportion of survival were used to measure population success. Results suggested population benefits from high level of individual variability under extreme environmental conditions including unfavorable temperature, salinity, as well as low food concentration, and selection on fast-growers becomes stronger with increasing individual variability and increasing environmental stress. Multiple regression analysis showed that temperature, food concentration, salinity and individual variability have significant effects on survival of A. tonsa population. These results suggest that environmental factors have great influence on zooplankton population, and individual variability has important implications for population survivability under unfavorable conditions. Given that marine ecosystems are at risk from drastic environmental changes, understanding how individual variability sustains populations could increase our capability to predict population dynamics in a changing environment.

  11. The contribution of zooplankton faecal pellets to deep carbon transport in the Scotia Sea (Southern Ocean)

    NASA Astrophysics Data System (ADS)

    Manno, C.; Stowasser, G.; Enderlein, P.; Fielding, S.; Tarling, G. A.

    2014-11-01

    The northern Scotia Sea contains the largest seasonal uptake of atmospheric carbon dioxide yet measured in the Southern Ocean. This study examines one of the main routes by which this carbon fluxes to the deep ocean, through the production of faecal pellets (FPs) by the zooplankton community. Deep sediment traps were deployed in two sites with contrasting ocean productivity regimes (P3, naturally iron-fertilized and P2, iron-limited), within the same water mass. The magnitude and seasonal pattern of particulate organic carbon (POC) and FPs in the traps was markedly different between the two sites. Maximum fluxes at P3 (22.91 mg C m-2 d-1; 2534 × 10 FP m-2 d-1) were an order of magnitude higher than at P2 (4.01 mg C m-2 d-1; 915 × 10 FP m-2 d-1), with flux at P3 exhibiting a double seasonal peak, compared to a single flatter peak at P2. The maximum contribution of FP carbon to the total amount of POC was twice as high at P3 (91%) compared to P2 (40%). The dominant FP category at P3 varied between round, ovoidal, cylindrical and tabular over the course of the year while, at P2, ovoidal FPs were consistently dominant, always making up more than 60% of the FP assemblage. There was also a difference in the FP state between the two sites, with FPs being relatively intact at P3, while FPs were often fragmented with broken peritrophic membranes at P2. The exception was ovoidal FPs, which were relatively intact at both sites. Our observations suggest that there was community shift from an herbivorous to an omnivorous diet from spring through to autumn at P3 while detritivores had a higher relative importance over the year at P2. Furthermore, the flux was mainly a product of the vertically migrating zooplankton community at P3 while the FP flux was more likely to be generated by deeper-dwelling zooplankton feeding on recycled material at P2. The results demonstrate that the feeding behavior and vertical distribution of the zooplankton community plays a critical role in

  12. Multi-scale structural community organisation of the human genome.

    PubMed

    Boulos, Rasha E; Tremblay, Nicolas; Arneodo, Alain; Borgnat, Pierre; Audit, Benjamin

    2017-04-11

    Structural interaction frequency matrices between all genome loci are now experimentally achievable thanks to high-throughput chromosome conformation capture technologies. This ensues a new methodological challenge for computational biology which consists in objectively extracting from these data the structural motifs characteristic of genome organisation. We deployed the fast multi-scale community mining algorithm based on spectral graph wavelets to characterise the networks of intra-chromosomal interactions in human cell lines. We observed that there exist structural domains of all sizes up to chromosome length and demonstrated that the set of structural communities forms a hierarchy of chromosome segments. Hence, at all scales, chromosome folding predominantly involves interactions between neighbouring sites rather than the formation of links between distant loci. Multi-scale structural decomposition of human chromosomes provides an original framework to question structural organisation and its relationship to functional regulation across the scales. By construction the proposed methodology is independent of the precise assembly of the reference genome and is thus directly applicable to genomes whose assembly is not fully determined.

  13. Impacts of chemical gradients on microbial community structure

    SciT

    Chen, Jianwei; Hanke, Anna; Tegetmeyer, Halina E.

    Succession of redox processes is sometimes assumed to define a basic microbial community structure for ecosystems with oxygen gradients. In this paradigm, aerobic respiration, denitrification, fermentation and sulfate reduction proceed in a thermodynamically determined order, known as the ‘redox tower’. Here, we investigated whether redox sorting of microbial processes explains microbial community structure at low-oxygen concentrations. We subjected a diverse microbial community sampled from a coastal marine sediment to 100 days of tidal cycling in a laboratory chemostat. Oxygen gradients (both in space and time) led to the assembly of a microbial community dominated by populations that each performed aerobicmore » and anaerobic metabolism in parallel. This was shown by metagenomics, transcriptomics, proteomics and stable isotope incubations. Effective oxygen consumption combined with the formation of microaggregates sustained the activity of oxygen-sensitive anaerobic enzymes, leading to braiding of unsorted redox processes, within and between populations. Analyses of available metagenomic data sets indicated that the same ecological strategies might also be successful in some natural ecosystems.« less

  14. Impacts of chemical gradients on microbial community structure

    PubMed Central

    Chen, Jianwei; Hanke, Anna; Tegetmeyer, Halina E; Kattelmann, Ines; Sharma, Ritin; Hamann, Emmo; Hargesheimer, Theresa; Kraft, Beate; Lenk, Sabine; Geelhoed, Jeanine S; Hettich, Robert L; Strous, Marc

    2017-01-01

    Succession of redox processes is sometimes assumed to define a basic microbial community structure for ecosystems with oxygen gradients. In this paradigm, aerobic respiration, denitrification, fermentation and sulfate reduction proceed in a thermodynamically determined order, known as the ‘redox tower'. Here, we investigated whether redox sorting of microbial processes explains microbial community structure at low-oxygen concentrations. We subjected a diverse microbial community sampled from a coastal marine sediment to 100 days of tidal cycling in a laboratory chemostat. Oxygen gradients (both in space and time) led to the assembly of a microbial community dominated by populations that each performed aerobic and anaerobic metabolism in parallel. This was shown by metagenomics, transcriptomics, proteomics and stable isotope incubations. Effective oxygen consumption combined with the formation of microaggregates sustained the activity of oxygen-sensitive anaerobic enzymes, leading to braiding of unsorted redox processes, within and between populations. Analyses of available metagenomic data sets indicated that the same ecological strategies might also be successful in some natural ecosystems. PMID:28094795

  15. Impacts of chemical gradients on microbial community structure.

    PubMed

    Chen, Jianwei; Hanke, Anna; Tegetmeyer, Halina E; Kattelmann, Ines; Sharma, Ritin; Hamann, Emmo; Hargesheimer, Theresa; Kraft, Beate; Lenk, Sabine; Geelhoed, Jeanine S; Hettich, Robert L; Strous, Marc

    2017-04-01

    Succession of redox processes is sometimes assumed to define a basic microbial community structure for ecosystems with oxygen gradients. In this paradigm, aerobic respiration, denitrification, fermentation and sulfate reduction proceed in a thermodynamically determined order, known as the 'redox tower'. Here, we investigated whether redox sorting of microbial processes explains microbial community structure at low-oxygen concentrations. We subjected a diverse microbial community sampled from a coastal marine sediment to 100 days of tidal cycling in a laboratory chemostat. Oxygen gradients (both in space and time) led to the assembly of a microbial community dominated by populations that each performed aerobic and anaerobic metabolism in parallel. This was shown by metagenomics, transcriptomics, proteomics and stable isotope incubations. Effective oxygen consumption combined with the formation of microaggregates sustained the activity of oxygen-sensitive anaerobic enzymes, leading to braiding of unsorted redox processes, within and between populations. Analyses of available metagenomic data sets indicated that the same ecological strategies might also be successful in some natural ecosystems.

  16. Phylogenetic structure of soil bacterial communities predicts ecosystem functioning.

    PubMed

    Pérez-Valera, Eduardo; Goberna, Marta; Verdú, Miguel

    2015-05-01

    Quantifying diversity with phylogeny-informed metrics helps understand the effects of diversity on ecosystem functioning (EF). The sign of these effects remains controversial because phylogenetic diversity and taxonomic identity may interactively influence EF. Positive relationships, traditionally attributed to complementarity effects, seem unimportant in natural soil bacterial communities. Negative relationships could be attributed to fitness differences leading to the overrepresentation of few productive clades, a mechanism recently invoked to assemble soil bacteria communities. We tested in two ecosystems contrasting in terms of environmental heterogeneity whether two metrics of phylogenetic community structure, a simpler measure of phylogenetic diversity (NRI) and a more complex metric incorporating taxonomic identity (PCPS), correctly predict microbially mediated EF. We show that the relationship between phylogenetic diversity and EF depends on the taxonomic identity of the main coexisting lineages. Phylogenetic diversity was negatively related to EF in soils where a marked fertility gradient exists and a single and productive clade (Proteobacteria) outcompete other clades in the most fertile plots. However, phylogenetic diversity was unrelated to EF in soils where the fertility gradient is less marked and Proteobacteria coexist with other abundant lineages. Including the taxonomic identity of bacterial lineages in metrics of phylogenetic community structure allows the prediction of EF in both ecosystems. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  17. Impacts of chemical gradients on microbial community structure

    DOE PAGES

    Chen, Jianwei; Hanke, Anna; Tegetmeyer, Halina E.; ...

    2017-01-17

    Succession of redox processes is sometimes assumed to define a basic microbial community structure for ecosystems with oxygen gradients. In this paradigm, aerobic respiration, denitrification, fermentation and sulfate reduction proceed in a thermodynamically determined order, known as the ‘redox tower’. Here, we investigated whether redox sorting of microbial processes explains microbial community structure at low-oxygen concentrations. We subjected a diverse microbial community sampled from a coastal marine sediment to 100 days of tidal cycling in a laboratory chemostat. Oxygen gradients (both in space and time) led to the assembly of a microbial community dominated by populations that each performed aerobicmore » and anaerobic metabolism in parallel. This was shown by metagenomics, transcriptomics, proteomics and stable isotope incubations. Effective oxygen consumption combined with the formation of microaggregates sustained the activity of oxygen-sensitive anaerobic enzymes, leading to braiding of unsorted redox processes, within and between populations. Analyses of available metagenomic data sets indicated that the same ecological strategies might also be successful in some natural ecosystems.« less

  18. Changes in Soil Fungal Community Structure with Increasing Disturbance Frequency.

    PubMed

    Cho, Hyunjun; Kim, Mincheol; Tripathi, Binu; Adams, Jonathan

    2017-07-01

    Although disturbance is thought to be important in many ecological processes, responses of fungal communities to soil disturbance have been little studied experimentally. We subjected a soil microcosm to physical disturbance, at a range of frequencies designed to simulate ecological disturbance events. We analyzed the fungal community structure using Illumina HiSeq sequencing of the ITS1 region. Fungal diversity was found to decline with the increasing disturbance frequencies, with no sign of the "humpback" pattern found in many studies of larger sedentary organisms. There is thus no evidence of an effect of release from competition resulting from moderate disturbance-which suggests that competition and niche overlap may not be important in limiting soil fungal diversity. Changing disturbance frequency also led to consistent differences in community composition. There were clear differences in OTU-level composition, with different disturbance treatments each having distinct fungal communities. The functional profile of fungal groups (guilds) was changed by the level of disturbance frequency. These predictable differences in community composition suggest that soil fungi can possess different niches in relation to disturbance frequency, or time since last disturbance. Fungi appear to be most abundant relative to bacteria at intermediate disturbance frequencies, on the time scale we studied here.

  19. Clustering algorithm for determining community structure in large networks

    NASA Astrophysics Data System (ADS)

    Pujol, Josep M.; Béjar, Javier; Delgado, Jordi

    2006-07-01

    We propose an algorithm to find the community structure in complex networks based on the combination of spectral analysis and modularity optimization. The clustering produced by our algorithm is as accurate as the best algorithms on the literature of modularity optimization; however, the main asset of the algorithm is its efficiency. The best match for our algorithm is Newman’s fast algorithm, which is the reference algorithm for clustering in large networks due to its efficiency. When both algorithms are compared, our algorithm outperforms the fast algorithm both in efficiency and accuracy of the clustering, in terms of modularity. Thus, the results suggest that the proposed algorithm is a good choice to analyze the community structure of medium and large networks in the range of tens and hundreds of thousand vertices.

  20. Community structure from spectral properties in complex networks

    NASA Astrophysics Data System (ADS)

    Servedio, V. D. P.; Colaiori, F.; Capocci, A.; Caldarelli, G.

    2005-06-01

    We analyze the spectral properties of complex networks focusing on their relation to the community structure, and develop an algorithm based on correlations among components of different eigenvectors. The algorithm applies to general weighted networks, and, in a suitably modified version, to the case of directed networks. Our method allows to correctly detect communities in sharply partitioned graphs, however it is useful to the analysis of more complex networks, without a well defined cluster structure, as social and information networks. As an example, we test the algorithm on a large scale data-set from a psychological experiment of free word association, where it proves to be successful both in clustering words, and in uncovering mental association patterns.

  1. A community detection algorithm based on structural similarity

    NASA Astrophysics Data System (ADS)

    Guo, Xuchao; Hao, Xia; Liu, Yaqiong; Zhang, Li; Wang, Lu

    2017-09-01

    In order to further improve the efficiency and accuracy of community detection algorithm, a new algorithm named SSTCA (the community detection algorithm based on structural similarity with threshold) is proposed. In this algorithm, the structural similarities are taken as the weights of edges, and the threshold k is considered to remove multiple edges whose weights are less than the threshold, and improve the computational efficiency. Tests were done on the Zachary’s network, Dolphins’ social network and Football dataset by the proposed algorithm, and compared with GN and SSNCA algorithm. The results show that the new algorithm is superior to other algorithms in accuracy for the dense networks and the operating efficiency is improved obviously.

  2. Effects of a La Niña event on hydrological patterns and copepod community structure in a shallow tropical estuary (Taperaçu, Northern Brazil)

    NASA Astrophysics Data System (ADS)

    Andrade, Marcela P.; Magalhães, André; Pereira, Luci C. C.; Flores-Montes, Manuel J.; Pardal, Emarielle C.; Andrade, Thamara P.; Costa, Rauquírio M.

    2016-12-01

    The influences of the 2011 La Niña event on the hydrological patterns and copepod community structure were investigated in a shallow tropical estuary, the Taperaçu, in northern Brazil. Specifically, this study aimed to explore the response of the most dominant copepod species and ecological indices (diversity, evenness and richness) to temporal changes in rainfall regime and water parameters in a tropical meso-macro tidal setting. Zooplankton samples were collected from three sampling sites using a conical plankton net (120 μm mesh), with both water and zooplankton samples analyzed by standard methods. In 2011, the physical, chemical and biological parameters of the water were exacerbated by increased rainfall levels resulting from the La Niña event. This resulted in a reduction in the salinity and an increase in dissolved nutrient concentrations and phytoplankton biomass in the study area. These conditions had a direct effect on the monthly dynamics of copepods as a whole, and in particular of five species, O. oswaldocruzi (169,090 ± 254,609 ind. m- 3; p < 0.0001), P. acutus (301,133 ± 518,065 ind. m- 3; p < 0.05), P. marshi (329,391 ± 563,009 ind. m- 3; p > 0.05), O. hebes (40,888 ± 64,893 ind. m- 3; p < 0.05) and A. tonsa (10,680 ± 13,877 ind. m- 3; p > 0.05), all of which were represented by higher densities in February. An extremely high recruitment rate of copepod nauplii was also observed during this month (3,088,309 ± 5,206,645 ind. m- 3; p < 0.05), with this peak in density thus overlapping that of the adult forms. The anomalous period of rainfall was also reflected in reduced species richness and diversity, which not only affected the structure of the copepod community, but may also have provoked shifts in trophic dynamics at higher levels, such as zooplanktivorous fishes.

  3. The deep-sea zooplankton of the North, Central, and South Atlantic: Biomass, abundance, diversity

    NASA Astrophysics Data System (ADS)

    Vereshchaka, Alexander; Abyzova, Galina; Lunina, Anastasia; Musaeva, Eteri

    2017-03-01

    Ocean-scale surveys of vertical distribution of the zooplankton from the surface to the bathypelagic zone along transects are quite rare in the North Atlantic and absent in the Equatorial and South Atlantic. We present the first deep-sea quantitative survey of the zooplankton in the Equatorial and South Atlantic, analyze the interaction between environment (depth, water masses, surface productivity) and zooplankton abundance and biomass, and assess the biodiversity and role of copepods in various deep strata. Samples were taken at 20 sites along a submeridional transect between 40°N and 30°S at four discrete depth strata: epi- meso-, upper- and lower- bathypelagic. A closing Bogorov-Rass plankton net (1 m2 opening, 500 μm mesh size, towed at a speed of 1 m s-1) was used and three major plankton groups were defined: non-gelatinous mesozooplankton (mainly copepods and chaetognaths; 1-30 mm length), gelatinous mesozooplankton (mainly siphonophorans, medudae and salps; individual or zooid; 1-30 mm length) and macroplankton (mainly shrimps; over 30 mm length). Over 300 plankton taxa were identified, among which 243 belonged to Copepoda. Two-dimensional distribution (latitude versus depth zone) of major group biomass, total copepod abundance, and abundance of dominant species is presented as well as distribution of biodiversity parameters (number of species, Shannon and 'dominance' indices). Biomass and abundance of all major groups were depth-dependent. The number of taxa (N) was depended on surface productivity, diversity of the communities was strongly linked to depth, whilst 'evenness' was independant upon both variables. Each of depth strata was inhabited by distinct copepod assemblages, which significantly differed from each other. The paper is concluded with brief descriptions of the deep Atlantic plankton communities from studied strata.

  4. Diatom community structure on in-service cruise ship hulls.

    PubMed

    Hunsucker, Kelli Zargiel; Koka, Abhishek; Lund, Geir; Swain, Geoffrey

    2014-10-01

    Diatoms are an important component of marine biofilms found on ship hulls. However, there are only a few published studies that describe the presence and abundance of diatoms on ships, and none that relate to modern ship hull coatings. This study investigated the diatom community structure on two in-service cruise ships with the same cruise cycles, one coated with an antifouling (AF) system (copper self-polishing copolymer) and the other coated with a silicone fouling-release (FR) system. Biofilm samples were collected during dry docking from representative areas of the ship and these provided information on the horizontal and vertical zonation of the hull, and intact and damaged coating and niche areas. Diatoms from the genera Achnanthes, Amphora and Navicula were the most common, regardless of horizontal ship zonation and coating type. Other genera were abundant, but their presence was more dependent on the ship zonation and coating type. Samples collected from damaged areas of the hull coating had a similar community composition to undamaged areas, but with higher diatom abundance. Diatom fouling on the niche areas differed from that of the surrounding ship hull and paralleled previous studies that investigated differences in diatom community structure on static and dynamically exposed coatings; niche areas were similar to static immersion and the hull to dynamic immersion. Additionally, diatom richness was greater on the ship with the FR coating, including the identification of several new genera to the biofouling literature, viz. Lampriscus and Thalassiophysa. These results are the first to describe diatom community composition on in-service ship hulls coated with a FR system. This class of coatings appears to have a larger diatom community compared to copper-based AF systems, with new diatom genera that have the ability to stick to ship hulls and withstand hydrodynamic forces, thus creating the potential for new problematic species in the biofilm.

  5. Zooplankton data: Vertical distributions of zooplankton in the Norweigian and Greenland Seas during summer, 1989

    SciT

    Lane, P.V.Z.; Smith, S.L.; Schwarting, E.M.

    1993-08-01

    Recent studies of zooplankton populations in the Greenland Sea have focused on processes at the Marginal Ice Zone (MIZ) and the areas immediately adjacent to it under the ice and in open water. These studies have shown a relatively short period of intense secondary productivity which is closely linked temporally and spatially to phytoplankton blooms occurring near the ice edge in spring and early summer. During the summer of 1989 we participated in a project focusing on benthic and water column processes in the basins of the Norwegian and Greenland Seas. This study allowed us to compare biological processes atmore » the MIZ with those occurring in the open waters of the Greenland Sea, and to compare processes at both of these locations with those in the Norwegian Sea. The data presented in this report are the results of zooplankton net tows covering the upper 1000 meters of the water column over the Norwegian Sea basin and the Greenland Sea basin, and the upper 500 meters of open water adjacent to the MIZ in the Greenland Sea. Sampling was conducted between 12 and 29 July 1989.« less

  6. Oceanographic structure drives the assembly processes of microbial eukaryotic communities

    PubMed Central

    Monier, Adam; Comte, Jérôme; Babin, Marcel; Forest, Alexandre; Matsuoka, Atsushi; Lovejoy, Connie

    2015-01-01

    Arctic Ocean microbial eukaryote phytoplankton form subsurface chlorophyll maximum (SCM), where much of the annual summer production occurs. This SCM is particularly persistent in the Western Arctic Ocean, which is strongly salinity stratified. The recent loss of multiyear sea ice and increased particulate-rich river discharge in the Arctic Ocean results in a greater volume of fresher water that may displace nutrient-rich saltier waters to deeper depths and decrease light penetration in areas affected by river discharge. Here, we surveyed microbial eukaryotic assemblages in the surface waters, and within and below the SCM. In most samples, we detected the pronounced SCM that usually occurs at the interface of the upper mixed layer and Pacific Summer Water (PSW). Poorly developed SCM was seen under two conditions, one above PSW and associated with a downwelling eddy, and the second in a region influenced by the Mackenzie River plume. Four phylogenetically distinct communities were identified: surface, pronounced SCM, weak SCM and a deeper community just below the SCM. Distance–decay relationships and phylogenetic structure suggested distinct ecological processes operating within these communities. In the pronounced SCM, picophytoplanktons were prevalent and community assembly was attributed to water mass history. In contrast, environmental filtering impacted the composition of the weak SCM communities, where heterotrophic Picozoa were more numerous. These results imply that displacement of Pacific waters to greater depth and increased terrigenous input may act as a control on SCM development and result in lower net summer primary production with a more heterotroph dominated eukaryotic microbial community. PMID:25325383

  7. Bacterial community structure in aquifers corresponds to stratigraphy

    NASA Astrophysics Data System (ADS)

    Beyer, Andrea; Möller, Silke; Neumann, Stefan; Burow, Katja; Gutmann, Falko; Lindner, Julia; Müsse, Steffen; Kothe, Erika; Büchel, Georg

    2014-05-01

    So far, groundwater microbiology with respect to different host rocks has not been well described in the literature. However, factors influencing the communities would be of interest to provide a tool for mapping groundwater paths. The Thuringian Basin (Germany) studied here, contains formations of the Permian (Zechstein) and also Triassic period of Buntsandstein, Muschelkalk and Keuper, all of which can be found to crop out at the surface in different regions. We analyzed the bacterial community of nine natural springs and sixteen groundwater wells of the respective rock formations as well as core material from the Zechstein salts. For that we sampled in a mine 3 differnet salt rock samples (carnallitite, halite and sylvinitite). To validate the different approaches, similar rock formations were compared and a consistent microbial community for Buntsandstein could be verified. Similary, for Zechstein, the presence of halophiles was seen with cultivation, isolation directly from the rock material and also in groundwater with DNA-dependent approaches. A higher overlap between sandstone- and limestone-derived communities was visible as if compared to the salt formations. Principal component analysis confirmed formation specific patterns for Muschelkalk, Buntsandstein and Zechstein for the bacterial taxa present, with some overlaps. Bacilli and Gammaproteobacteria were the major groups, with the genera Pseudomonas, Marinomonas, Bacillus, Marinobacter and Pseudoalteromonas representing the communities. The bacteria are well adapted to their respective environment with survival strategies including a wide range of salinity which makes them suitable as tracers for fluid movement below the ground. The results indicate the usefulness and robustness of the approach taken here to investigate aquifer community structures in dependence of the stratigraphy of the groundwater reservoir.

  8. Bacterial community structure in experimental methanogenic bioreactors and search for pathogenic clostridia as community members.

    PubMed

    Dohrmann, Anja B; Baumert, Susann; Klingebiel, Lars; Weiland, Peter; Tebbe, Christoph C

    2011-03-01

    Microbial conversion of organic waste or harvested plant material into biogas has become an attractive technology for energy production. Biogas is produced in reactors under anaerobic conditions by a consortium of microorganisms which commonly include bacteria of the genus Clostridium. Since the genus Clostridium also harbors some highly pathogenic members in its phylogenetic cluster I, there has been some concern that an unintended growth of such pathogens might occur during the fermentation process. Therefore this study aimed to follow how process parameters affect the diversity of Bacteria in general, and the diversity of Clostridium cluster I members in particular. The development of both communities was followed in model biogas reactors from start-up during stable methanogenic conditions. The biogas reactors were run with either cattle or pig manures as substrates, and both were operated at mesophilic and thermophilic conditions. The structural diversity was analyzed independent of cultivation using a PCR-based detection of 16S rRNA genes and genetic profiling by single-strand conformation polymorphism (SSCP). Genetic profiles indicated that both bacterial and clostridial communities evolved in parallel, and the community structures were highly influenced by both substrate and temperature. Sequence analysis of 16S rRNA genes recovered from prominent bands from SSCP profiles representing Clostridia detected no pathogenic species. Thus, this study gave no indication that pathogenic clostridia would be enriched as dominant community members in biogas reactors fed with manure.

  9. Linking microbial community structure to function in representative simulated systems.

    PubMed

    Marcus, Ian M; Wilder, Hailey A; Quazi, Shanin J; Walker, Sharon L

    2013-04-01

    Pathogenic bacteria are generally studied as a single strain under ideal growing conditions, although these conditions are not the norm in the environments in which pathogens typically proliferate. In this investigation, a representative microbial community along with Escherichia coli O157:H7, a model pathogen, was studied in three environments in which such a pathogen could be found: a human colon, a septic tank, and groundwater. Each of these systems was built in the lab in order to retain the physical/chemical and microbial complexity of the environments while maintaining control of the feed into the models. The microbial community in the colon was found to have a high percentage of bacteriodetes and firmicutes, while the septic tank and groundwater systems were composed mostly of proteobacteria. The introduction of E. coli O157:H7 into the simulated systems elicited a shift in the structures and phenotypic cell characteristics of the microbial communities. The fate and transport of the microbial community with E. coli O157:H7 were found to be significantly different from those of E. coli O157:H7 studied as a single isolate, suggesting that the behavior of the organism in the environment was different from that previously conceived. The findings in this study clearly suggest that to gain insight into the fate of pathogens, cells should be grown and analyzed under conditions simulating those of the environment in which the pathogens are present.

  10. Microbial Community Structure in the Rhizosphere of Rice Plants

    PubMed Central

    Breidenbach, Björn; Pump, Judith; Dumont, Marc G.

    2016-01-01

    The microbial community in the rhizosphere environment is critical for the health of land plants and the processing of soil organic matter. The objective of this study was to determine the extent to which rice plants shape the microbial community in rice field soil over the course of a growing season. Rice (Oryza sativa) was cultivated under greenhouse conditions in rice field soil from Vercelli, Italy and the microbial community in the rhizosphere of planted soil microcosms was characterized at four plant growth stages using quantitative PCR and 16S rRNA gene pyrotag analysis and compared to that of unplanted bulk soil. The abundances of 16S rRNA genes in the rice rhizosphere were on average twice that of unplanted bulk soil, indicating a stimulation of microbial growth in the rhizosphere. Soil environment type (i.e., rhizosphere versus bulk soil) had a greater effect on the community structure than did time (e.g., plant growth stage). Numerous phyla were affected by the presence of rice plants, but the strongest effects were observed for Gemmatimonadetes, Proteobacteria, and Verrucomicrobia. With respect to functional groups of microorganisms, potential iron reducers (e.g., Geobacter, Anaeromyxobacter) and fermenters (e.g., Clostridiaceae, Opitutaceae) were notably enriched in the rhizosphere environment. A Herbaspirillum species was always more abundant in the rhizosphere than bulk soil and was enriched in the rhizosphere during the early stage of plant growth. PMID:26793175

  11. Linking Microbial Community Structure to Function in Representative Simulated Systems

    PubMed Central

    Marcus, Ian M.; Wilder, Hailey A.; Quazi, Shanin J.

    2013-01-01

    Pathogenic bacteria are generally studied as a single strain under ideal growing conditions, although these conditions are not the norm in the environments in which pathogens typically proliferate. In this investigation, a representative microbial community along with Escherichia coli O157:H7, a model pathogen, was studied in three environments in which such a pathogen could be found: a human colon, a septic tank, and groundwater. Each of these systems was built in the lab in order to retain the physical/chemical and microbial complexity of the environments while maintaining control of the feed into the models. The microbial community in the colon was found to have a high percentage of bacteriodetes and firmicutes, while the septic tank and groundwater systems were composed mostly of proteobacteria. The introduction of E. coli O157:H7 into the simulated systems elicited a shift in the structures and phenotypic cell characteristics of the microbial communities. The fate and transport of the microbial community with E. coli O157:H7 were found to be significantly different from those of E. coli O157:H7 studied as a single isolate, suggesting that the behavior of the organism in the environment was different from that previously conceived. The findings in this study clearly suggest that to gain insight into the fate of pathogens, cells should be grown and analyzed under conditions simulating those of the environment in which the pathogens are present. PMID:23396331

  12. Physical structure of artificial seagrass affects macrozoobenthic community recruitment

    NASA Astrophysics Data System (ADS)

    Ambo-Rappe, R.; Rani, C.

    2018-03-01

    Seagrass ecosystems are important in supporting marine biodiversity. However, the worldwide decline in seagrass areas due to anthropogenic factors leads to a decrease in the marine biodiversity they can support. There is growing awareness of the need for concepts to conserve and/or rehabilitate seagrass ecosystems. One option is to create artificial seagrass to provide a physical structure for the marine organisms to colonize. The objective of this research was to analyze the effect of some artificial seagrasses and seagrass transplants on marine biodiversity, with a focus on the macrozoobenthic community. The experimental design compared two types of artificial seagrass (polypropylene ribbons and shrub-shaped plastic leaves), and seagrass transplants from nearby seagrass meadows. The experimental plots were 4 x 4 m2 with 3 replicates. Macrozoobenthic communities were sampled fortnightly for 3.5 months. At the end of the experiment, makrozoobenthos were also sampled from a natural seagrass bed nearby. Of 116 macrozoobenthic species in the artificial seagrass plots, 91 were gastropods. The density of the macrobenthic fauna increased from the beginning to the end of the study in all treatments, but the increase was only significant for the artificial seagrass treatment (i.e. shrub-like plastic leaves). There was a distinct separation between the macrozoobenthic community structure found in the restoration plots (artificial seagrass and transplanted seagrass) compared to natural seagrass beds.

  13. A local immunization strategy for networks with overlapping community structure

    NASA Astrophysics Data System (ADS)

    Taghavian, Fatemeh; Salehi, Mostafa; Teimouri, Mehdi

    2017-02-01

    Since full coverage treatment is not feasible due to limited resources, we need to utilize an immunization strategy to effectively distribute the available vaccines. On the other hand, the structure of contact network among people has a significant impact on epidemics of infectious diseases (such as SARS and influenza) in a population. Therefore, network-based immunization strategies aim to reduce the spreading rate by removing the vaccinated nodes from contact network. Such strategies try to identify more important nodes in epidemics spreading over a network. In this paper, we address the effect of overlapping nodes among communities on epidemics spreading. The proposed strategy is an optimized random-walk based selection of these nodes. The whole process is local, i.e. it requires contact network information in the level of nodes. Thus, it is applicable to large-scale and unknown networks in which the global methods usually are unrealizable. Our simulation results on different synthetic and real networks show that the proposed method outperforms the existing local methods in most cases. In particular, for networks with strong community structures, high overlapping membership of nodes or small size communities, the proposed method shows better performance.

  14. Fungal endophyte communities reflect environmental structuring across a Hawaiian landscape

    PubMed Central

    Zimmerman, Naupaka B.; Vitousek, Peter M.

    2012-01-01

    We surveyed endophytic fungal communities in leaves of a single tree species (Metrosideros polymorpha) across wide environmental gradients (500–5,500 mm of rain/y; 10–22 °C mean annual temperature) spanning short geographic distances on Mauna Loa Volcano, Hawai’i. Using barcoded amplicon pyrosequencing at 13 sites (10 trees/site; 10 leaves/tree), we found very high levels of diversity within sites (a mean of 551 ± 134 taxonomic units per site). However, among-site diversity contributed even more than did within-site diversity to the overall richness of more than 4,200 taxonomic units observed in M. polymorpha, and this among-site variation in endophyte community composition correlated strongly with temperature and rainfall. These results are consistent with suggestions that foliar endophytic fungi are hyperdiverse. They further suggest that microbial diversity may be even greater than has been assumed and that broad-scale environmental controls such as temperature and rainfall can structure eukaryotic microbial diversity. Appropriately constrained study systems across strong environmental gradients present a useful means to understand the environmental factors that structure the diversity of microbial communities. PMID:22837398

  15. The CECAM Electronic Structure Library: community-driven development of software libraries for electronic structure simulations

    NASA Astrophysics Data System (ADS)

    Oliveira, Micael

    The CECAM Electronic Structure Library (ESL) is a community-driven effort to segregate shared pieces of software as libraries that could be contributed and used by the community. Besides allowing to share the burden of developing and maintaining complex pieces of software, these can also become a target for re-coding by software engineers as hardware evolves, ensuring that electronic structure codes remain at the forefront of HPC trends. In a series of workshops hosted at the CECAM HQ in Lausanne, the tools and infrastructure for the project were prepared, and the first contributions were included and made available online (http://esl.cecam.org). In this talk I will present the different aspects and aims of the ESL and how these can be useful for the electronic structure community.

  16. Influence of a breakwater on nearby rocky intertidal community structure.

    PubMed

    Martins, Gustavo M; Amaral, André F; Wallenstein, Francisco M; Neto, Ana I

    2009-01-01

    It is widely recognised that coastal-defence structures generally affect the structure of the assemblages they support, yet their impact on adjacent systems has been largely ignored. Breakwaters modify the nearby physical environment (e.g. wave action) suggesting a local impact on biological parameters. In the present study, an ACI (After-Control-Impact) design was used to test the general hypothesis that the artificial sheltering of an exposed coast has a strong effect on the structure and functioning of adjacent systems. The effects of a reduction in hydrodynamics were clear for a number of taxa and included the replacement of barnacles, limpets and frondose algae by an increasing cover of ephemeral algae. These effects were evident both at early and late successional stages. Results suggest that the artificial sheltering of naturally exposed coasts can have a strong impact promoting a shift from consumer- to producer-dominated communities, which has important ecological and energetic consequences for the ecosystem.

  17. Eco-evolutionary dynamics in urbanized landscapes: evolution, species sorting and the change in zooplankton body size along urbanization gradients.

    PubMed

    Brans, Kristien I; Govaert, Lynn; Engelen, Jessie M T; Gianuca, Andros T; Souffreau, Caroline; De Meester, Luc

    2017-01-19

    Urbanization causes both changes in community composition and evolutionary responses, but most studies focus on these responses in isolation. We performed an integrated analysis assessing the relative contribution of intra- and interspecific trait turnover to the observed change in zooplankton community body size in 83 cladoceran communities along urbanization gradients quantified at seven spatial scales (50-3200 m radii). We also performed a quantitative genetic analysis on 12 Daphnia magna populations along the same urbanization gradient. Body size in zooplankton communities generally declined with increasing urbanization, but the opposite was observed for communities dominated by large species. The contribution of intraspecific trait variation to community body size turnover with urbanization strongly varied with the spatial scale considered, and was highest for communities dominated by large cladoceran species and at intermediate spatial scales. Genotypic size at maturity was smaller for urban than for rural D. magna populations and for animals cultured at 24°C compared with 20°C. While local genetic adaptation likely contributed to the persistence of D. magna in the urban heat islands, buffering for the phenotypic shift to larger body sizes with increasing urbanization, community body size turnover was mainly driven by non-genetic intraspecific trait change.This article is part of the themed issue 'Human influences on evolution, and the ecological and societal consequences'. © 2016 The Author(s).

  18. Eco-evolutionary dynamics in urbanized landscapes: evolution, species sorting and the change in zooplankton body size along urbanization gradients

    PubMed Central

    Souffreau, Caroline

    2017-01-01

    Urbanization causes both changes in community composition and evolutionary responses, but most studies focus on these responses in isolation. We performed an integrated analysis assessing the relative contribution of intra- and interspecific trait turnover to the observed change in zooplankton community body size in 83 cladoceran communities along urbanization gradients quantified at seven spatial scales (50–3200 m radii). We also performed a quantitative genetic analysis on 12 Daphnia magna populations along the same urbanization gradient. Body size in zooplankton communities generally declined with increasing urbanization, but the opposite was observed for communities dominated by large species. The contribution of intraspecific trait variation to community body size turnover with urbanization strongly varied with the spatial scale considered, and was highest for communities dominated by large cladoceran species and at intermediate spatial scales. Genotypic size at maturity was smaller for urban than for rural D. magna populations and for animals cultured at 24°C compared with 20°C. While local genetic adaptation likely contributed to the persistence of D. magna in the urban heat islands, buffering for the phenotypic shift to larger body sizes with increasing urbanization, community body size turnover was mainly driven by non-genetic intraspecific trait change. This article is part of the themed issue ‘Human influences on evolution, and the ecological and societal consequences’. PMID:27920375

  19. Changes in fatty acid and hydrocarbon composition of zooplankton assemblages related to environmental conditions

    SciT

    Lambert, R.M.

    1989-01-01

    Changes in zooplankton fatty acid and hydrocarbon patterns are described in relation to changes in environmental conditions and species composition. The regulation of zooplankton abundance by sea nettle-ctenophore interaction was examined in a small Rhode Island coastal pond. Sea nettles were nettles were able to eliminate ctenophores from the pond and subsequently zooplankton abundance increased. During one increase in zooplankton abundance, it was found that polyunsaturated fatty acids decreased while monounsaturated fatty acids increased. It was concluded that this shift in biochemical pattern was due to food limitation. In addition, zooplankton fatty acids were used in multivariate discriminant analysis tomore » classify whether zooplankton were from coastal or estuarine environments. Zooplankton from coastal environments were characterized by higher monounsaturate fatty acids. Zooplankton hydrocarbon composition was affected by species composition and by pollution inputs. The presence of Calanus finmarchicus was detected by increased levels of pristane.« less

  20. Locomotor adaptations of some gelatinous zooplankton.

    PubMed

    Bone, Q

    1985-01-01

    cost of locomotion is greater in Doliolum. Few gelatinous zooplankton show special adaptations both for rapid escape movements, and for slow sustained swimming, those that do deserve further study.

  1. Interactions of phytoplankton, zooplankton and microorganisms

    NASA Astrophysics Data System (ADS)

    Pomeroy, L. R.; Paffenhöfer, G.-A.; Yoder, J. A.

    We present evidence that there are significant interactions between heterotrophic microorganisms, doliolids and Fritillaria within intrusions of nutrient-rich Gulf Stream water stranding on the continental shelf. During the summer of 1981 cold, nutrient-rich water from below the surface of the Gulf Stream was repeatedly intruded and stranded on the continental shelf off northeastern Florida. On August 6 old, stranded Gulf Stream water depleted of nitrate occupied the lower layer on the outer shelf. The upper water was continental shelf water, older but of undefined age. On August 6 free-living bacteria were >10 6ml -1 everywhere at all depths, an order of magnitude greater than normal bacterial numbers on the northeastern Florida continental shelf. Over 10 days the numbers of free bacteria doubled while bacteria attached to particles increased by a factor of four. The adenylate/chlorophyll ratio showed that phytoplankton dominated the lower layers of intruded water, while the surface water became increasingly dominated by heterotrophic microorganisms (bacteria and protozoa) over 10 days. There were significant, negative correlations between bacteria and doliolids and between bacteria and Fritillaria. Regions of maximum bacterial numbers did not coincide with locations of salp swarms. The increased numbers of bacteria at all depths in a highly stratified system in which most phytoplankton are in the lower layer suggests a diverse source of bacterial growth substrates, some of which involve zooplankton as intermediaries. Production of autotrophs is more than twice that of microheterotrophs on average, but because of their differential distribution, microheterotrophs are the dominant biomass in much of the surface water and may be significant in energy flux to metazoan consumers as well as competitors for mutually useable sources of nutrition.

  2. Glacial meltwater influences on plankton community structure and the importance of top-down control (of primary production) in a NE Greenland fjord

    NASA Astrophysics Data System (ADS)

    Arendt, Kristine Engel; Agersted, Mette Dalgaard; Sejr, Mikael Kristian; Juul-Pedersen, Thomas

    2016-12-01

    Freshwater runoff from the Greenland Ice Sheet (GIS) can be an important driver influencing plankton community structure in Greenland fjords. In the present study, we describe physical, taxonomic and functional differences in the plankton community in Young Sound, a NE Greenland fjord, from the inner fjord close to the GIS towards the coastal region in late summer. The fjord is influenced by runoff from land-terminating glaciers that separated the surface layer from cold underlying waters. The highest chlorophyll a concentration (<2.5 μg l-1) was found in the coastal region at 20-50 m depth. The most profound difference in the mesozooplankton community structure along the section was seen in the abundance of the copepods Microcalanus spp., which were present in the coastal region in the upper 100 m, and Pseudocalanus spp., which only occurred in the surface layers and mainly in the inner part of the fjord. In addition to this, both species have been observed to change in abundance within the last decade. Calanus spp. copepods made up > 74.9% of the total copepod biomass at all stations, and their grazing impact was the highest among the copepod groups. Copepod grazing impact on the phytoplankton standing stock, however, was exceeded by microzooplankton grazing, investigated by dilution experiments, with the highest grazing impact on the phytoplankton standing stock of 63% d-1 in the inner part of the fjord. In spite of high phytoplankton instantaneous growth rates at the innermost fjord station, proto-zooplankton was capable of controlling the phytoplankton production. The study showed functional differences within the system and provides indications of how dynamic the coastal ecosystem of Greenland can be.

  3. Perfluoroalkyl Acids Shift Microbial Community Structure Across Experimental Scales

    NASA Astrophysics Data System (ADS)

    Weathers, T. S.; Sharp, J.

    2016-12-01

    Perfluoroalkyl acids (PFAAs) are contaminants of emerging concern that have increasingly been found in groundwater and drinking water systems. Previously, we demonstrated that PFAAs significantly alter the abundance of specific microbial clades in batch reductive dechlorinating systems, resulting in decreased chlorinated solvent attenuation capabilities. To further understand the impacts of PFAA exposure on subsurface microbial processes and PFAA transport, we investigated changes in microbial community structure as a function of PFAA presence in flow-through columns simulating aquifer transport. Phylogenetic analysis using high throughput, next generation sequencing performed after exposure to 250 pore volumes of source zone concentrations of PFAAs (10 mg/L each of 11 analytes including PFOS and PFOA) resulted in patterns that mirrored those observed in batch systems, demonstrating a conservation of community dynamics across experimental scales. Of the nine clades observed in both batch and flow-through systems, six were similarly impacted as a function of PFAA exposure, regardless of the experimental differences in transport and redox state. Specifically, the presence of PFAAs enhanced the relative abundance of Archaea, Bacteroidetes (phylum), and the family Veillonellaceae in both systems. Repressed clades include the genus Sedimentibacter, Ruminococcaceae (family), and the Anaerolineales, which contains Dehalococcoides, a genus known for its ability to fully dechlorinate TCE. As PFAAs are often co-located with TCE and BTEX, changes in microbial community structure can result in hindered bioremediation of these co-contaminants. Consideration of community shifts and corresponding changes in behavior, such as repressed reductive dechlorination or increased biofilm formation, will aid in the development of conceptual site models that account for co-contaminant bioremediation potential and PFAA transport.

  4. Community detection for networks with unipartite and bipartite structure

    NASA Astrophysics Data System (ADS)

    Chang, Chang; Tang, Chao

    2014-09-01

    Finding community structures in networks is important in network science, technology, and applications. To date, most algorithms that aim to find community structures only focus either on unipartite or bipartite networks. A unipartite network consists of one set of nodes and a bipartite network consists of two nonoverlapping sets of nodes with only links joining the nodes in different sets. However, a third type of network exists, defined here as the mixture network. Just like a bipartite network, a mixture network also consists of two sets of nodes, but some nodes may simultaneously belong to two sets, which breaks the nonoverlapping restriction of a bipartite network. The mixture network can be considered as a general case, with unipartite and bipartite networks viewed as its limiting cases. A mixture network can represent not only all the unipartite and bipartite networks, but also a wide range of real-world networks that cannot be properly represented as either unipartite or bipartite networks in fields such as biology and social science. Based on this observation, we first propose a probabilistic model that can find modules in unipartite, bipartite, and mixture networks in a unified framework based on the link community model for a unipartite undirected network [B Ball et al (2011 Phys. Rev. E 84 036103)]. We test our algorithm on synthetic networks (both overlapping and nonoverlapping communities) and apply it to two real-world networks: a southern women bipartite network and a human transcriptional regulatory mixture network. The results suggest that our model performs well for all three types of networks, is competitive with other algorithms for unipartite or bipartite networks, and is applicable to real-world networks.

  5. Does salinity change determine zooplankton variability in the saline Qarun Lake (Egypt)?

    NASA Astrophysics Data System (ADS)

    El-Shabrawy, Gamal M.; Anufriieva, Elena V.; Germoush, Mousa O.; Goher, Mohamed E.; Shadrin, Nickolai V.

    2015-11-01

    Zooplankton and 14 abiotic variables were studied during August 2011 at 10 stations in Lake Qarun, Egypt. Stations with the lowest salinity and highest nutrient concentrations and turbidity were close to the discharge of waters from the El-Bats and El-Wadi drainage systems. A total of 15 holozooplankton species were identified. The salinity in Lake Qarun increased and fluctuated since 1901: 12 g/L in 1901; 8.5 g/L in 1905; 12.0 g/L in 1922; 30.0 g/L in 1985; 38.7 g/L in 1994; 35.3 g/L in 2006, and 33.4 g/L in 2011. The mean concentration of nutrients (nitrate, nitrite and orthophosphate) gradually increased from 35, 0.16 and 0.38 µg/L, respectively, in 1953-1955 to 113, 16.4, and 30.26 µg/L in 2011. From 1999-2003 some decrease of species diversity occurred. Average total zooplankton density was 30 000 ind./m3 in 1974-1977; 356 125 ind./m3 in 1989; 534 000 ind./m3 in 1994-1995; from 965 000 to 1 452 000 ind./m3 in 2006, and 595 000 ind./m3 in 2011. A range of long-term summer salinity variability during the last decades was very similar to a range of salinity spatial variability in summer 2011. There is no significant correlation between zooplankton abundance and salinity in spatial and long-term changes. We conclude that salinity fluctuations since at least 1955 did not directly drive the changes of composition and abundance of zooplankton in the lake. A marine community had formed in the lake, and it continues to change. One of the main drivers of this change is a regular introduction and a pressure of alien species on the existent community. Eutrophication also plays an important role. The introduction of Mnemiopsis leidyi, first reported in 2014, may lead to a start of a new stage of the biotic changes in Lake Qarun, when eutrophication and the population dynamics of this ctenophore will be main drivers of the ecosystem change.

  6. Exposure and effects of sediment-spiked fludioxonil on macroinvertebrates and zooplankton in outdoor aquatic microcosms.

    PubMed

    Yin, Xiao H; Brock, Theo C M; Barone, Lidia E; Belgers, J Dick M; Boerwinkel, Marie-Claire; Buijse, Laura; van Wijngaarden, René P A; Hamer, Mick; Roessink, Ivo

    2018-01-01

    Information from effects of pesticides in sediments at an ecosystem level, to validate current and proposed risk assessment procedures, is scarce. A sediment-spiked outdoor freshwater microcosm experiment was conducted with fludioxonil (lipophilic, non-systemic fungicide) to study exposure dynamics and treatment-related responses of benthic and pelagic macroinvertebrates and zooplankton. Besides blank control and solvent control systems the experiment had six different treatment levels (1.7-614mga.s./kg dry sediment) based around the reported 28-d No Observed Effect Concentration (NOEC) for Chironomus riparius (40mga.s./kg dry sediment). Twelve systems were available per treatment of which four were sacrificed on each of days 28, 56 and 84 after microcosm construction. Fludioxonil persisted in the sediment and mean measured concentrations were 53-82% of the initial concentration after 84days. The dissipation rate increased with the treatment level. Also exposure concentrations in overlying water were long-term, with highest concentrations 28days after initiation of the experiment. Sediment-dwelling Oligochaeta and pelagic Rotifera and Cladocera showed the most pronounced treatment-related declines. The most sensitive sediment-dwelling oligochaete was Dero digitata (population NOEC 14.2mga.s./kg dry sediment). The same NOEC was calculated for the sediment-dwelling macroinvertebrate community. The most sensitive zooplankton species was the cladoceran Diaphanosoma brachyurum (NOEC of 1.6μga.s./L in overlying water corresponding to 5.0mga.s./kg dry sediment). At the two highest treatments several rotifer taxa showed a pronounced decrease, while the zooplankton community-level NOEC was 5.6μga.s./L (corresponding to 14.2mga.s./kg dry sediment). Zooplankton taxa calanoid Copepoda and Daphnia gr. longispina showed a pronounced treatment-related increase (indirect effects). Consequently, an assessment factor of 10 to the chronic laboratory NOECs of Chironomus riparius

  7. Climate change effects on soil microarthropod abundance and community structure

    SciT

    Kardol, Paul; Reynolds, W. Nicholas; Norby, Richard J

    2011-01-01

    Long-term ecosystem responses to climate change strongly depend on how the soil subsystem and its inhabitants respond to these perturbations. Using open-top chambers, we studied the response of soil microarthropods to single and combined effects of ambient and elevated atmospheric [CO{sub 2}], ambient and elevated temperatures and changes in precipitation in constructed old-fields in Tennessee, USA. Microarthropods were assessed five years after treatments were initiated and samples were collected in both November and June. Across treatments, mites and collembola were the most dominant microarthropod groups collected. We did not detect any treatment effects on microarthropod abundance. In November, but notmore » in June, microarthropod richness, however, was affected by the climate change treatments. In November, total microarthropod richness was lower in dry than in wet treatments, and in ambient temperature treatments, richness was higher under elevated [CO{sub 2}] than under ambient [CO{sub 2}]. Differential responses of individual taxa to the climate change treatments resulted in shifts in community composition. In general, the precipitation and warming treatments explained most of the variation in community composition. Across treatments, we found that collembola abundance and richness were positively related to soil moisture content, and that negative relationships between collembola abundance and richness and soil temperature could be explained by temperature-related shifts in soil moisture content. Our data demonstrate how simultaneously acting climate change factors can affect the structure of soil microarthropod communities in old-field ecosystems. Overall, changes in soil moisture content, either as direct effect of changes in precipitation or as indirect effect of warming or elevated [CO{sub 2}], had a larger impact on microarthropod communities than did the direct effects of the warming and elevated [CO{sub 2}] treatments. Moisture-induced shifts in

  8. Benthic infaunal community structuring in an acidified tropical estuarine system.

    PubMed

    Hossain, M Belal; Marshall, David J

    2014-01-01

    Recent studies suggest that increasing ocean acidification (OA) should have strong direct and indirect influences on marine invertebrates. While most theory and application for OA is based on relatively physically-stable oceanic ecological systems, less is known about the effects of acidification on nearshore and estuarine systems. Here, we investigated the structuring of a benthic infaunal community in a tropical estuarine system, along a steep salinity and pH gradient, arising largely from acid-sulphate groundwater inflows (Sungai Brunei Estuary, Borneo, July 2011- June 2012). Preliminary data indicate that sediment pore-water salinity (range: 8.07 - 29.6 psu) declined towards the mainland in correspondence with the above-sediment estuarine water salinity (range: 3.58 - 31.2 psu), whereas the pore-water pH (range: 6.47- 7.72) was generally lower and less variable than the estuarine water pH (range: 5.78- 8.3), along the estuary. Of the thirty six species (taxa) recorded, the polychaetes Neanthes sp., Onuphis conchylega, Nereididae sp. and the amphipod Corophiidae sp., were numerically dominant. Calcified microcrustaceans (e.g., Cyclopoida sp. and Corophiidae sp.) were abundant at all stations and there was no clear distinction in distribution pattern along the estuarine between calcified and non-calcified groups. Species richness increased seawards, though abundance (density) showed no distinct directional trend. Diversity indices were generally positively correlated (Spearman's rank correlation) with salinity and pH (p <0.05) and negatively with clay and organic matter, except for evenness values (p >0.05). Three faunistic assemblages were distinguished: (1) nereid-cyclopoid-sabellid, (2) corophiid-capitellid and (3) onuphid- nereid-capitellid. These respectively associated with lower salinity/pH and a muddy bottom, low salinity/pH and a sandy bottom, and high salinity/pH and a sandy bottom. However, CCA suggested that species distribution and community

  9. Matrix composition and community structure analysis of a novel bacterial pyrite leaching community.

    PubMed

    Ziegler, Sibylle; Ackermann, Sonia; Majzlan, Juraj; Gescher, Johannes

    2009-09-01

    Here we describe a novel bacterial community that is embedded in a matrix of carbohydrates and bio/geochemical products of pyrite (FeS(2)) oxidation. This community grows in stalactite-like structures--snottites--on the ceiling of an abandoned pyrite mine at pH values of 2.2-2.6. The aqueous phase in the matrix contains 200 mM of sulfate and total iron concentrations of 60 mM. Micro-X-ray diffraction analysis showed that jarosite [(K,Na,H(3)O)Fe(3)(SO(4))(2)(OH)(6)] is the major mineral embedded in the snottites. X-ray absorption near-edge structure experiments revealed three different sulfur species. The major signal can be ascribed to sulfate, and the other two features may correspond to thiols and sulfoxides. Arabinose was detected as the major sugar component in the extracellular polymeric substance. Via restriction fragment length polymorphism analysis, a community was found that mainly consists of iron oxidizing Leptospirillum and Ferrovum species but also of bacteria that could be involved in dissimilatory sulfate and dissimilatory iron reduction. Each snottite can be regarded as a complex, self-contained consortium of bacterial species fuelled by the decomposition of pyrite.

  10. Securing the Future: Retention Models in Community Colleges--Study of Community College Structures for Student Success (SCCSSS)

    ERIC Educational Resources Information Center

    College Board Advocacy & Policy Center, 2012

    2012-01-01

    The Study of Community College Structures for Student Success (SCCSSS) was launched in 2010 with three goals at its center: (1) To explore a set of promising institutional practices and organizational structures identified through theory and research as having the potential to support community college student success; (2) To present a synthesized…

  11. The Interplay between Environmental Filtering and Spatial Processes in Structuring Communities: The Case of Neotropical Snake Communities

    PubMed Central

    Cavalheri, Hamanda; Both, Camila; Martins, Marcio

    2015-01-01

    Both habitat filters and spatial processes can influence community structure. Space alone affects species immigration from the regional species pool, whereas habitat filters affect species distribution and inter-specific interactions. This study aimed to understand how the interplay between environmental and geographical processes influenced the structure of Neotropical snake communities in different habitat types. We selected six studies that sampled snakes in forests, four conducted in savannas and two in grasslands (the latter two are grouped in a non-forest category). We used the net relatedness and nearest taxon indices to assess phylogenetic structure within forest and non-forest areas. We also used the phylogenetic fuzzy-weighting algorithm to characterize phylogenetic structure across communities and the relation of phylogenetic composition patterns to habitat type, structure, and latitude. Finally, we tested for morphological trait convergence and phylogenetic niche conservatism using four forest and four non-forest areas for which morphological data were available. Community phylogenetic composition changed across forest and non-forest areas suggesting that environmental filtering influences community structure. Species traits were affected by habitat type, indicating convergence at the metacommunity level. Tail length, robustness, and number of ventral scales maximized community convergence among forest and non-forest areas. The observed patterns suggested environmental filtering, indicating that less vertically structured habitats represent a strong filter. Despite the fact that phylogenetic structure was not detected individually for each community, we observed a trend towards communities composed by more closely related species in higher latitudes and more overdispersed compositions in lower latitudes. Such pattern suggests that the limited distribution of major snake lineages constrained species distributions. Structure indices for each community

  12. The Interplay between Environmental Filtering and Spatial Processes in Structuring Communities: The Case of Neotropical Snake Communities.

    PubMed

    Cavalheri, Hamanda; Both, Camila; Martins, Marcio

    2015-01-01

    Both habitat filters and spatial processes can influence community structure. Space alone affects species immigration from the regional species pool, whereas habitat filters affect species distribution and inter-specific interactions. This study aimed to understand how the interplay between environmental and geographical processes influenced the structure of Neotropical snake communities in different habitat types. We selected six studies that sampled snakes in forests, four conducted in savannas and two in grasslands (the latter two are grouped in a non-forest category). We used the net relatedness and nearest taxon indices to assess phylogenetic structure within forest and non-forest areas. We also used the phylogenetic fuzzy-weighting algorithm to characterize phylogenetic structure across communities and the relation of phylogenetic composition patterns to habitat type, structure, and latitude. Finally, we tested for morphological trait convergence and phylogenetic niche conservatism using four forest and four non-forest areas for which morphological data were available. Community phylogenetic composition changed across forest and non-forest areas suggesting that environmental filtering influences community structure. Species traits were affected by habitat type, indicating convergence at the metacommunity level. Tail length, robustness, and number of ventral scales maximized community convergence among forest and non-forest areas. The observed patterns suggested environmental filtering, indicating that less vertically structured habitats represent a strong filter. Despite the fact that phylogenetic structure was not detected individually for each community, we observed a trend towards communities composed by more closely related species in higher latitudes and more overdispersed compositions in lower latitudes. Such pattern suggests that the limited distribution of major snake lineages constrained species distributions. Structure indices for each community

  13. Experimental warming effects on the bacterial community structure and diversity

    NASA Astrophysics Data System (ADS)

    Kim, W.; Han, S.; Adams, J.; Son, Y.

    2014-12-01

    The objective of this study is to investigate the responses of soil bacterial community to future temperature increase by conducting open-field warming experiment. We conducted an open-field experimental warming system using infra-red heater in 2011 and regulated the temperature of warmed plots by 3oC higher than that of control plots constantly. The seeds of Pinus densiflora, Abies holophylla, Abies koreana, Betula costata, Quercus variabilis, Fraxinus rhynchophylla, and Zelkova serrata were planted in each 1 m × 1 m plot (n=3) in April, 2012. We collected soil samples from the rhizosphere of 7 tree species. DNA was extracted and PCR-amplified for the bacterial 16S gene targeting V1-V3 region. The paired-end sequencing was performed at Beijing Genome Institute (BGI, Hong Kong, China) using 2× 100 bp Hiseq2000 (Illumina). This study aimed to answer the following prediction/hypothesis: 1) Experimental warming will change the structure of soil bacterial community, 2) There will be distinct 'indicator group' which response to warming treatment relatively more sensitive than other groups. 3) Warming treatment will enhance the microbial activity in terms of soil respiration. 4) The rhizoplane bacterial communities for each of 7 tree species will show different response pattern to warming treatment. Since the sequence data does not arrive before the submission deadline, therefore, we would like to present the results and discussions on December 2014, AGU Fall Meeting.

  14. Impact of oil on bacterial community structure in bioturbated sediments.

    PubMed

    Stauffert, Magalie; Cravo-Laureau, Cristiana; Jézéquel, Ronan; Barantal, Sandra; Cuny, Philippe; Gilbert, Franck; Cagnon, Christine; Militon, Cécile; Amouroux, David; Mahdaoui, Fatima; Bouyssiere, Brice; Stora, Georges; Merlin, François-Xavier; Duran, Robert

    2013-01-01

    Oil spills threaten coastlines where biological processes supply essential ecosystem services. Therefore, it is crucial to understand how oil influences the microbial communities in sediments that play key roles in ecosystem functioning. Ecosystems such as sediments are characterized by intensive bioturbation due to burrowing macrofauna that may modify the microbial metabolisms. It is thus essential to consider the bioturbation when determining the impact of oil on microbial communities. In this study, an experimental laboratory device maintaining pristine collected mudflat sediments in microcosms closer to true environmental conditions--with tidal cycles and natural seawater--was used to simulate an oil spill under bioturbation conditions. Different conditions were applied to the microcosms including an addition of: standardized oil (Blend Arabian Light crude oil, 25.6 mg.g⁻¹ wet sediment), the common burrowing organism Hediste (Nereis) diversicolor and both the oil and H. diversicolor. The addition of H. diversicolor and its associated bioturbation did not affect the removal of petroleum hydrocarbons. After 270 days, 60% of hydrocarbons had been removed in all microcosms irrespective of the H. diversicolor addition. However, 16S-rRNA gene and 16S-cDNA T-RFLP and RT-PCR-amplicon libraries analysis showed an effect of the condition on the bacterial community structure, composition, and dynamics, supported by PerMANOVA analysis. The 16S-cDNA libraries from microcosms where H. diversicolor was added (oiled and un-oiled) showed a marked dominance of sequences related to Gammaproteobacteria. However, in the oiled-library sequences associated to Deltaproteobacteria and Bacteroidetes were also highly represented. The 16S-cDNA libraries from oiled-microcosms (with and without H. diversicolor addition) revealed two distinct microbial communities characterized by different phylotypes associated to known hydrocarbonoclastic bacteria and dominated by Gammaproteobacteria

  15. Impact of Oil on Bacterial Community Structure in Bioturbated Sediments

    PubMed Central

    Stauffert, Magalie; Cravo-Laureau, Cristiana; Jézéquel, Ronan; Barantal, Sandra; Cuny, Philippe; Gilbert, Franck; Cagnon, Christine; Militon, Cécile; Amouroux, David; Mahdaoui, Fatima; Bouyssiere, Brice; Stora, Georges; Merlin, François-Xavier; Duran, Robert

    2013-01-01

    Oil spills threaten coastlines where biological processes supply essential ecosystem services. Therefore, it is crucial to understand how oil influences the microbial communities in sediments that play key roles in ecosystem functioning. Ecosystems such as sediments are characterized by intensive bioturbation due to burrowing macrofauna that may modify the microbial metabolisms. It is thus essential to consider the bioturbation when determining the impact of oil on microbial communities. In this study, an experimental laboratory device maintaining pristine collected mudflat sediments in microcosms closer to true environmental conditions – with tidal cycles and natural seawater – was used to simulate an oil spill under bioturbation conditions. Different conditions were applied to the microcosms including an addition of: standardized oil (Blend Arabian Light crude oil, 25.6 mg.g−1 wet sediment), the common burrowing organism Hediste (Nereis) diversicolor and both the oil and H. diversicolor. The addition of H. diversicolor and its associated bioturbation did not affect the removal of petroleum hydrocarbons. After 270 days, 60% of hydrocarbons had been removed in all microcosms irrespective of the H. diversicolor addition. However, 16S-rRNA gene and 16S-cDNA T-RFLP and RT-PCR-amplicon libraries analysis showed an effect of the condition on the bacterial community structure, composition, and dynamics, supported by PerMANOVA analysis. The 16S-cDNA libraries from microcosms where H. diversicolor was added (oiled and un-oiled) showed a marked dominance of sequences related to Gammaproteobacteria. However, in the oiled-library sequences associated to Deltaproteobacteria and Bacteroidetes were also highly represented. The 16S-cDNA libraries from oiled-microcosms (with and without H. diversicolor addition) revealed two distinct microbial communities characterized by different phylotypes associated to known hydrocarbonoclastic bacteria and dominated by

  16. Mass media influence spreading in social networks with community structure

    NASA Astrophysics Data System (ADS)

    Candia, Julián; Mazzitello, Karina I.

    2008-07-01

    We study an extension of Axelrod's model for social influence, in which cultural drift is represented as random perturbations, while mass media are introduced by means of an external field. In this scenario, we investigate how the modular structure of social networks affects the propagation of mass media messages across a society. The community structure of social networks is represented by coupled random networks, in which two random graphs are connected by intercommunity links. Considering inhomogeneous mass media fields, we study the conditions for successful message spreading and find a novel phase diagram in the multidimensional parameter space. These findings show that social modularity effects are of paramount importance for designing successful, cost-effective advertising campaigns.

  17. Impact of anthropogenic activities on water quality and plankton communities in the Day River (Red River Delta, Vietnam).

    PubMed

    Hoang, Hang Thi Thu; Duong, Thi Thuy; Nguyen, Kien Trung; Le, Quynh Thi Phuong; Luu, Minh Thi Nguyet; Trinh, Duc Anh; Le, Anh Hung; Ho, Cuong Tu; Dang, Kim Dinh; Némery, Julien; Orange, Didier; Klein, Judith

    2018-01-08

    Planktons are a major component of food web structure in aquatic ecosystems. Their distribution and community structure are driven by the combination and interactions between physical, chemical, and biological factors within the environment. In the present study, water quality and the community structure of phytoplankton and zooplankton were monthly investigated from January to December 2015 at 11 sampling sites along the gradient course of the Day River (Red River Delta, northern Vietnam). The study demonstrated that the Day River was eutrophic with the average values of total phosphorus concentration 0.17 mg/L, total nitrogen concentration 1.98 mg/L, and Chl a 54 μg/L. Microscopic plankton analysis showed that phytoplankton comprised 87 species belonging to seven groups in which Chlorophyceae, Bacillariophyceae, and Cyanobacteria accounted for the most important constituents of the river's phytoplankton assemblage. A total 53 zooplankton species belonging to three main groups including Copepoda, Cladocera, and Rotatoria were identified. Plankton biomass values were greatest in rainy season (3002.10-3 cell/L for phytoplankton and 12.573 individuals/m 3 for zooplankton). Using principal correspondence and Pearson correlation analyses, it was found that the Day River was divided into three main site groups based on water quality and characteristics of plankton community. Temperature and nutrients (total phosphorus and total nitrogen) are key factors regulating plankton abundance and distribution in the Day River.

  18. Microbial Community Structure and Enzyme Activities in Semiarid Agricultural Soils

    NASA Astrophysics Data System (ADS)

    Acosta-Martinez, V. A.; Zobeck, T. M.; Gill, T. E.; Kennedy, A. C.

    2002-12-01

    The effect of agricultural management practices on the microbial community structure and enzyme activities of semiarid soils of different textures in the Southern High Plains of Texas were investigated. The soils (sandy clay loam, fine sandy loam and loam) were under continuous cotton (Gossypium hirsutum L.) or in rotations with peanut (Arachis hypogaea L.), sorghum (Sorghum bicolor L.) or wheat (Triticum aestivum L.), and had different water management (irrigated or dryland) and tillage (conservation or conventional). Microbial community structure was investigated using fatty acid methyl ester (FAME) analysis by gas chromatography and enzyme activities, involved in C, N, P and S cycling of soils, were measured (mg product released per kg soil per h). The activities of b-glucosidase, b-glucosaminidase, alkaline phosphatase, and arylsulfatase were significantly (P<0.05) increased in soils under cotton rotated with sorghum or wheat, and due to conservation tillage in comparison to continuous cotton under conventional tillage. Principal component analysis showed FAME profiles of these soils separated distinctly along PC1 (20 %) and PC2 (13 %) due to their differences in soil texture and management. No significant differences were detected in FAME profiles due to management practices for the same soils in this sampling period. Enzyme activities provide early indications of the benefits in microbial populations and activities and soil organic matter under crop rotations and conservation tillage in comparison to the typical practices in semiarid regions of continuous cotton and conventional tillage.

  19. Community structure and elevational diversity patterns of soil Acidobacteria.

    PubMed

    Zhang, Yuguang; Cong, Jing; Lu, Hui; Li, Guangliang; Qu, Yuanyuan; Su, Xiujiang; Zhou, Jizhong; Li, Diqiang

    2014-08-01

    Acidobacteria is one of the most dominant and abundant phyla in soil, and was believed to have a wide range of metabolic and genetic functions. Relatively little is known about its community structure and elevational diversity patterns. We selected four elevation gradients from 1000 to 2800 m with typical vegetation types of the northern slope of Shennongjia Mountain in central China. The vegetation types were evergreen broadleaved forest, deciduous broadleaved forest, coniferous forest and sub-alpine shrubs. We analyzed the soil acidobacterial community composition, elevational patterns and the relationship between Acidobacteria subdivisions and soil enzyme activities by using the 16S rRNA meta-sequencing technique and multivariate statistical analysis. The result found that 19 known subdivisions as well as an unclassified phylotype were presented in these forest sites, and Subdivision 6 has the highest number of detectable operational taxonomic units (OTUs). A significant single peak distribution pattern (P<0.05) between the OTU number and the elevation was observed. The Jaccard and Bray-Curtis index analysis showed that the soil Acidobacteria compositional similarity significantly decreased (P<0.01) with the increase in elevation distance. Mantel test analysis showed the most of the soil Acidobacteria subdivisions had the significant relationship (P<0.01) with different soil enzymes. Therefore, soil Acidobacteria may be involved in different ecosystem functions in global elemental cycles. Partial Mantel tests and CCA analysis showed that soil pH, soil temperature and plant diversity may be the key factors in shaping the soil Acidobacterial community structure. Copyright © 2014. Published by Elsevier B.V.

  20. Comparisons between POC and zooplankton swimmer flux from sediment traps in the subarctic and subtropical North Pacific

    NASA Astrophysics Data System (ADS)

    Yokoi, Naoya; Abe, Yoshiyuki; Kitamura, Minoru; Honda, Makio C.; Yamaguchi, Atsushi

    2018-03-01

    Seasonal changes in zooplankton swimmer (ZS) abundance, biomass and community structure were evaluated based on samples collected by moored sediment traps at a depth of 200 m in the subarctic (SA) and subtropical (ST) western North Pacific. Based on these samples, we made comparisons on two topics: 1) latitudinal (subarctic vs. subtropical) changes in ZS abundance, biomass and community and 2) quantitative differences between the ZS and particle organic carbon (POC) fluxes based on data from moored or drifting sediment traps. The results showed that the ZS flux was greater in the SA (annual mean: 311 ind. m-2 day-1 or 258 mg C m-2 day-1) than in the ST (135 ind. m-2 day-1 or 38 mg C m-2 day-1). The peak ZS flux was observed from July-August in the SA and from April-May in the ST. The dominant taxa were Copepoda and Chaetognatha in the SA and Ostracoda and Mollusca in the ST. These latitudinal differences are likely related to the dominance of large-sized Copepoda in the SA, regional differences in the timing of the spring phytoplankton bloom, and the magnitude and size structure of primary producers. The percent composition of ZS to the total C flux (= ZS+POC flux) varied by region: 85-95% in the SA and 47-75% in the ST. These differences between the ZS composition and the total C flux are most likely caused by the dominance of large-sized Copepoda (Neocalanus spp. and Eucalanus bungii) in the SA.

  1. Epipelagic mesozooplankton succession and community structure over a marine ouffall area in the northeastern South China Sea.

    PubMed

    Tseng, Li Chun; Kumar, Ram; Dahms, Hans Uwe; Chen, Chun Te; Chen, Qing Chao; Hwang, Jiang Shiou

    2008-05-01

    This study analyses distribution and abundance patterns of mesozooplankton communities at 13 stations in the coastal waters over a marine outfall area in the northeastern South China Sea. Cruises were conducted in March, June and September 2002, and plankton samples were collected with a 333 microm North Pacific net. The Mesozooplankton was dominated by calanoid Copepods, Cladocera, Chaetognatha and Pteropoda. Stations located near the entrance of the harbor provided a relatively higher abundance of Noctilucales and Radiolarians. In total, 20 zooplankton groups were identified in which, Calanoida, Cladocera, Chaetognatha, Pteropoda, Poecilostomatoida and Appendicularia comprised 92.77% of the total zooplankton abundance. Copepoda dominated in all three cruises, comprising 65.32% of the total mesozooplankton abundance. Samples collected in June recorded higher mesozooplankton abundance than March and September samples. Onshore stations recorded higher BOD values, higher abundance of Noctilucales and Radiolarians and a relativelylower abundance of the overall mesozooplankton. Total mesozooplankton abundance did not correlate significantly with temperature, pH, or dissolved oxygen, but correlated negatively with BOD.

  2. Metagenomic insights into zooplankton‐associated bacterial communities

    PubMed Central

    Srivastava, Abhishek; Koski, Marja; Garcia, Juan Antonio L.; Takaki, Yoshihiro; Yokokawa, Taichi; Nunoura, Takuro; Elisabeth, Nathalie H.; Sintes, Eva; Herndl, Gerhard J.

    2017-01-01

    Summary Zooplankton and microbes play a key role in the ocean's biological cycles by releasing and consuming copious amounts of particulate and dissolved organic matter. Additionally, zooplankton provide a complex microhabitat rich in organic and inorganic nutrients in which bacteria thrive. In this study, we assessed the phylogenetic composition and metabolic potential of microbial communities associated with crustacean zooplankton species collected in the North Atlantic. Using Illumina sequencing of the 16S rRNA gene, we found significant differences between the microbial communities associated with zooplankton and those inhabiting the surrounding seawater. Metagenomic analysis of the zooplankton‐associated microbial community revealed a highly specialized bacterial community able to exploit zooplankton as microhabitat and thus, mediating biogeochemical processes generally underrepresented in the open ocean. The zooplankton‐associated bacterial community is able to colonize the zooplankton's internal and external surfaces using a large set of adhesion mechanisms and to metabolize complex organic compounds released or exuded by the zooplankton such as chitin, taurine and other complex molecules. Moreover, the high number of genes involved in iron and phosphorus metabolisms in the zooplankton‐associated microbiome suggests that this zooplankton‐associated bacterial community mediates specific biogeochemical processes (through the proliferation of specific taxa) that are generally underrepresented in the ambient waters. PMID:28967193

  3. Sound scattering by several zooplankton groups. II. Scattering models.

    PubMed

    Stanton, T K; Chu, D; Wiebe, P H

    1998-01-01

    Mathematical scattering models are derived and compared with data from zooplankton from several gross anatomical groups--fluidlike, elastic shelled, and gas bearing. The models are based upon the acoustically inferred boundary conditions determined from laboratory backscattering data presented in part I of this series [Stanton et al., J. Acoust. Soc. Am. 103, 225-235 (1998)]. The models use a combination of ray theory, modal-series solution, and distorted wave Born approximation (DWBA). The formulations, which are inherently approximate, are designed to include only the dominant scattering mechanisms as determined from the experiments. The models for the fluidlike animals (euphausiids in this case) ranged from the simplest case involving two rays, which could qualitatively describe the structure of target strength versus frequency for single pings, to the most complex case involving a rough inhomogeneous asymmetrically tapered bent cylinder using the DWBA-based formulation which could predict echo levels over all angles of incidence (including the difficult region of end-on incidence). The model for the elastic shelled body (gastropods in this case) involved development of an analytical model which takes into account irregularities and discontinuities of the shell. The model for gas-bearing animals (siphonophores) is a hybrid model which is composed of the summation of the exact solution to the gas sphere and the approximate DWBA-based formulation for arbitrarily shaped fluidlike bodies. There is also a simplified ray-based model for the siphonophore. The models are applied to data involving single pings, ping-to-ping variability, and echoes averaged over many pings. There is reasonable qualitative agreement between the predictions and single ping data, and reasonable quantitative agreement between the predictions and variability and averages of echo data.

  4. Development of a Multimetric Indicator of Pelagic Zooplankton ...

    EPA Pesticide Factsheets

    We used zooplankton data collected for the 2012 National Lakes Assessment (NLA) to develop multimetric indices (MMIs) for five aggregated ecoregions of the conterminous USA (Coastal Plains, Eastern Highlands, Plains, Upper Midwest, and Western Mountains and Xeric [“West’]). We classified candidate metrics into six categories: We evaluated the performance of candidate metrics, and used metrics that had passed these screens to calculate all possible candidate MMIs that included at least one metric from each category. We selected the candidate MMI that had high responsiveness, a reasonable value for repeatability, low mean pairwise correlation among component metrics, and, when possible, a maximum pairwise correlation among component metrics that was <0.7. We were able to develop MMIs that were sufficiently responsive and repeatable to assess ecological condition for the NLA without the need to reduce the effects of natural variation using models. We did not observe effects of either lake size, lake origin, or site depth on the MMIs. The MMIs appear to respond more strongly to increased nutrient concentrations than to shoreline habitat conditions. Improving our understanding of how zooplankton assemblages respond to increased human disturbance, and obtaining more complete autecological information for zooplankton taxa would likely improve MMIs developed for future assessments. Using zooplankton assemblage data from the 2012 National Lakes Assessment (NLA),

  5. Lake St. Clair zooplankton: Evidence for post-Dreissena changes

    David, Katherine A.; Davis, Bruce M.; Hunter, R. Douglas

    2009-01-01

    We surveyed the zooplankton of Lake St. Clair at 12 sites over ten dates from May to October 2000. Mean zooplankton density by site and date was 168.6 individuals/L, with Dreissena spp. veligers the most abundant taxon at 122.7 individuals/L. Rotifers, copepods, and cladocerans were far lower in mean abundance than in the early 1970s (rotifers, 20.9/L; copepods, 18.1/L; and cladocerans, 6.8/L). Species richness of zooplankton taxa in 2000 was 147, which was virtually unchanged from that of the first reported survey in 1894. Overall, the decline in abundance was greatest for rotifers (-90%) and about equal for cladocerans (-69%) and copepods (-66%). The decrease in abundance of Daphnia spp. was especially dramatic in Canadian waters. The decline in the southeastern region was significant for all three major groups of zooplankton, whereas in the northwestern region the decline was significant only for rotifers. From June to August 2000, Lake St. Clair open waters were numerically dominated by Dreissena spp. veligers, with a reduced abundance of rotifers and crustaceans compared to pre-Dreissena spp. surveys. Mean nutrient concentrations were not different from the 1970s, but Secchi depth (greater) and chlorophyll a concentration (lower) were. Disproportionate reduction in rotifer abundance is consistent with hypotheses implicating direct consumption by settled Dreissena spp. Reduction of crustaceans is likely due to more complex interactions including removal of nauplii as well as resource competition for phytoplankton.

  6. Distribution and abundance of zooplankton populations in Crater Lake, Oregon

    Larson, G.L.; McIntire, C.D.; Buktenica, M.W.; Girdner, S.F.; Truitt, R.E.

    2007-01-01

    The zooplankton assemblages in Crater Lake exhibited consistency in species richness and general taxonomic composition, but varied in density and biomass during the period between 1988 and 2000. Collectively, the assemblages included 2 cladoceran taxa and 10 rotifer taxa (excluding rare taxa). Vertical habitat partitioning of the water column to a depth of 200 m was observed for most species with similar food habits and/or feeding mechanisms. No congeneric replacement was observed. The dominant species in the assemblages were variable, switching primarily between periods of dominance of Polyarthra-Keratella cochlearis and Daphnia. The unexpected occurrence and dominance of Asplanchna in 1991 and 1992 resulted in a major change in this typical temporal shift between Polyarthra-K. cochlearis and Daphnia. Following a collapse of the zooplankton biomass in 1993 that was probably caused by predation from Asplanchna, Kellicottia dominated the zooplankton assemblage biomass between 1994 and 1997. The decline in biomass of Kellicottia by 1998 coincided with a dramatic increase in Daphnia biomass. When Daphnia biomass declined by 2000, Keratella biomass increased again. Thus, by 1998 the assemblage returned to the typical shift between Keratella-Polyarthra and Daphnia. Although these observations provided considerable insight about the interannual variability of the zooplankton assemblages in Crater Lake, little was discovered about mechanisms behind the variability. When abundant, kokanee salmon may have played an important role in the disappearance of Daphnia in 1990 and 2000 either through predation, inducing diapause, or both. ?? 2007 Springer Science+Business Media B.V.

  7. Ecological value of macrophyte cover in creating habitat for microalgae (diatoms) and zooplankton (rotifers and crustaceans) in small field and forest water bodies.

    PubMed

    Celewicz-Gołdyn, Sofia; Kuczyńska-Kippen, Natalia

    2017-01-01

    Due to their small area and shallow depth ponds are usually treated as a single sampling unit, while various microhabitats offer different environmental conditions. Thus, we tested the effect of different habitat types typically found within small ponds on the microalgae and zooplankton communities. We found that submerged macrophytes have the strongest impact on microalgae and zooplankton communities out of all the analysed habitats. Some epontic diatoms (e.g. Fragilaria dilatata, Cymbella affinis) and littoral-associated zooplankton species (e.g. Simocephalus vetulus, Lecane bulla) were significantly related to elodeids. However, pelagic species (e.g. bosminids) preferred less complex helophytes, which suggests that the most heterogeneous elodeid habitats were not an anti-predator shelter for cladocerans. Selection of different macrophyte types by taxonomically various organisms suggests that it is not only macrophyte cover that is desired for healthy aquatic environment but that a level of habitat mosaic is required to ensure the well-being of aquatic food webs. Species-specific preferences for different types of macrophytes indicate the high ecological value of macrophyte cover in ponds and a potential direction for the management of small water bodies towards maintaining a great variation of aquatic plants. Moreover, the type of surrounding landscape, reflecting human-induced disturbance (28 field ponds) and natural catchment (26 forest ponds), significantly influenced only zooplankton, while diatoms were affected indirectly through the level of conductivity. Nutrient overload (higher content of TRP) and increased conductivity in the field landscape contributed to a rise in microalgae (e.g. Amphora pediculus, Gomphonema parvulum) and zooplankton (e.g. Thermocyclops oithonoides, Eubosmina coregoni) abundance. An awareness of the responses of both components of plankton communities to environmental factors is necessary for maintaining the good state of small

  8. A spectral method to detect community structure based on distance modularity matrix

    NASA Astrophysics Data System (ADS)

    Yang, Jin-Xuan; Zhang, Xiao-Dong

    2017-08-01

    There are many community organizations in social and biological networks. How to identify these community structure in complex networks has become a hot issue. In this paper, an algorithm to detect community structure of networks is proposed by using spectra of distance modularity matrix. The proposed algorithm focuses on the distance of vertices within communities, rather than the most weakly connected vertex pairs or number of edges between communities. The experimental results show that our method achieves better effectiveness to identify community structure for a variety of real-world networks and computer generated networks with a little more time-consumption.

  9. Pilot Study on Potential Impacts of Fisheries-Induced Changes in Zooplankton Mortality on Marine Biogeochemistry

    NASA Astrophysics Data System (ADS)

    Getzlaff, Julia; Oschlies, Andreas

    2017-11-01

    In this pilot study we link the yield of industrial fisheries to changes in the zooplankton mortality in an idealized way accounting for different target species (planktivorous fish—decreased zooplankton mortality; large predators—increased zooplankton mortality). This indirect approach is used in a global coupled biogeochemistry circulation model to estimate the range of the potential impact of industrial fisheries on marine biogeochemistry. The simulated globally integrated response on phytoplankton and primary production is in line with expectations—a high (low) zooplankton mortality results in a decrease (increase) of zooplankton and an increase (decrease) of phytoplankton. In contrast, the local response of zooplankton and phytoplankton depends on the region under consideration: In nutrient-limited regions, an increase (decrease) in zooplankton mortality leads to a decrease (increase) in both zooplankton and phytoplankton biomass. In contrast, in nutrient-replete regions, such as upwelling regions, we find an opposing response: an increase (decrease) of the zooplankton mortality leads to an increase (decrease) in both zooplankton and phytoplankton biomass. The results are further evaluated by relating the potential fisheries-induced changes in zooplankton mortality to those driven by CO2 emissions in a business-as-usual 21st century emission scenario. In our idealized case, the potential fisheries-induced impact can be of similar size as warming-induced changes in marine biogeochemistry.

  10. Interlinking backscatter, grain size and benthic community structure

    NASA Astrophysics Data System (ADS)

    McGonigle, Chris; Collier, Jenny S.

    2014-06-01

    The relationship between acoustic backscatter, sediment grain size and benthic community structure is examined using three different quantitative methods, covering image- and angular response-based approaches. Multibeam time-series backscatter (300 kHz) data acquired in 2008 off the coast of East Anglia (UK) are compared with grain size properties, macrofaunal abundance and biomass from 130 Hamon and 16 Clamshell grab samples. Three predictive methods are used: 1) image-based (mean backscatter intensity); 2) angular response-based (predicted mean grain size), and 3) image-based (1st principal component and classification) from Quester Tangent Corporation Multiview software. Relationships between grain size and backscatter are explored using linear regression. Differences in grain size and benthic community structure between acoustically defined groups are examined using ANOVA and PERMANOVA+. Results for the Hamon grab stations indicate significant correlations between measured mean grain size and mean backscatter intensity, angular response predicted mean grain size, and 1st principal component of QTC analysis (all p < 0.001). Results for the Clamshell grab for two of the methods have stronger positive correlations; mean backscatter intensity (r2 = 0.619; p < 0.001) and angular response predicted mean grain size (r2 = 0.692; p < 0.001). ANOVA reveals significant differences in mean grain size (Hamon) within acoustic groups for all methods: mean backscatter (p < 0.001), angular response predicted grain size (p < 0.001), and QTC class (p = 0.009). Mean grain size (Clamshell) shows a significant difference between groups for mean backscatter (p = 0.001); other methods were not significant. PERMANOVA for the Hamon abundance shows benthic community structure was significantly different between acoustic groups for all methods (p ≤ 0.001). Overall these results show considerable promise in that more than 60% of the variance in the mean grain size of the Clamshell grab

  11. Effects of Climate on the Zooplankton of the California Current

    NASA Astrophysics Data System (ADS)

    Lavaniegos, B. E.

    2007-05-01

    Almost six decades of sampling of the California Current system, carried out by the CalCOFI program (California Cooperative Fisheries Investigation) complemented by a decade of observations from the IMECOCAL program (Investigaciones Mexicanas de la Corriente de California), have revealed changing patterns in zooplankton abundances, species composition, and distributions over interannual through multidecadal time scales. Interannual changes associated with ENSO variability are manifested as strong but transitory perturbations in the mean annual cycle in seasonal abundances (and distributions) of particular species. An investigation of longer- term change, limited to the region off southern California, shows a persistent decline in zooplankton volumes (a proxy for overall biomass of macrozooplankton) between 1977 and 1998 that is considered to be a response to the well documented shift in basin-scale climate forcing that occurred in 1976-77. Further examination of this decline in zooplankton volumes indicates that it was due principally to the disappearance of several salp species after 1977. Other species and functional groups did not decline after the change in climate regime, while some species have followed persistent secular trends that appear to be associated more with the phenomenon of long-term global warming. Differences in the regional responses to climate change throughout the California Current system have also been observed recently in the spatial distribution of zooplankton biomass and changes in latitudinal ranges of certain species. For example, zooplankton biomass in the Baja California region show typical values for the 1997-98 El Niño that were followed by a decrease during the sharp transition to the cool La Niña conditions in 1999. This contrasts with the nearby region off southern California that was characterized by reduced biomass during the El Niño period and the subsequent recovery during the La Niña. Another regional contrast in

  12. Seasonal changes in the assembly mechanisms structuring tropical fish communities.

    PubMed

    Fitzgerald, Daniel B; Winemiller, Kirk O; Sabaj Pérez, Mark H; Sousa, Leandro M

    2017-01-01

    Despite growing interest in trait-based approaches to community assembly, little attention has been given to seasonal variation in trait distribution patterns. Mobile animals can rapidly mediate influences of environmental factors and species interactions through dispersal, suggesting that the relative importance of different assembly mechanisms can vary over short time scales. This study analyzes seasonal changes in functional trait distributions of tropical fishes in the Xingu River, a major tributary of the Amazon with large predictable temporal variation in hydrologic conditions and species density. Comparison of observed functional diversity revealed that species within wet-season assemblages were more functionally similar than those in dry-season assemblages. Further, species within wet-season assemblages were more similar than random expectations based on null model predictions. Higher functional richness within dry season communities is consistent with increased niche complementarity during the period when fish densities are highest and biotic interactions should be stronger; however, null model tests suggest that stochastic factors or a combination of assembly mechanisms influence dry-season assemblages. These results demonstrate that the relative influence of community assembly mechanisms can vary seasonally in response to changing abiotic conditions, and suggest that studies attempting to infer a single dominant mechanism from functional patterns may overlook important aspects of the assembly process. During the prolonged flood pulse of the wet season, expanded habitat and lower densities of aquatic organisms likely reduce the influence of competition and predation. This temporal shift in the influence of different assembly mechanisms, rather than any single mechanism, may play a large role in maintaining the structure and diversity of tropical rivers and perhaps other dynamic and biodiverse systems. © 2016 by the Ecological Society of America.

  13. Pregnancy and birth in an indigenous Huichol community: from structural violence to structural policy responses.

    PubMed

    Gamlin, Jennie B; Hawkes, Sarah J

    2015-01-01

    Mexico's indigenous regions are characterised by socio-economic marginalisation and poor health outcomes and the Maternal Mortality Rate in indigenous communities continues to be around six times higher than the national rate. Using as a case study the Huichol community of North-Western Mexico we will discuss how institutional health and welfare programmes which aim to address accepted risk factors for maternal health are undermined by a series of structural barriers which put indigenous women especially in harm's way. Semi-structured interviews and observational data were gathered between 2009 and 2011 in highland communities and on coastal tobacco plantations to where a large number of this ethnic group migrate. Many Huichol women birth alone, and to facilitate this process they maintain a low nutritional intake to reduce their infant's growth and seek spiritual guidance during pregnancy from a shaman. These practices are reinforced by feelings of shame and humiliation encountered when using institutional health provision. These are some of the structural barriers to care that need to be addressed. Effective interventions could include addressing the training of health professionals, focusing on educational inequalities and the structural determinants of poverty whilst designing locally specific programmes that encourage acceptance of available health care.

  14. Aphid-parasitoid community structure on genetically modified wheat.

    PubMed

    von Burg, Simone; van Veen, Frank J F; Álvarez-Alfageme, Fernando; Romeis, Jörg

    2011-06-23

    Since the introduction of genetically modified (GM) plants, one of the main concerns has been their potential effect on non-target insects. Many studies have looked at GM plant effects on single non-target herbivore species or on simple herbivore-natural enemy food chains. Agro-ecosystems, however, are characterized by numerous insect species which are involved in complex interactions, forming food webs. In this study, we looked at transgenic disease-resistant wheat (Triticum aestivum) and its effect on aphid-parasitoid food webs. We hypothesized that the GM of the wheat lines directly or indirectly affect aphids and that these effects cascade up to change the structure of the associated food webs. Over 2 years, we studied different experimental wheat lines under semi-field conditions. We constructed quantitative food webs to compare their properties on GM lines with the properties on corresponding non-transgenic controls. We found significant effects of the different wheat lines on insect community structure up to the fourth trophic level. However, the observed effects were inconsistent between study years and the variation between wheat varieties was as big as between GM plants and their controls. This suggests that the impact of our powdery mildew-resistant GM wheat plants on food web structure may be negligible and potential ecological effects on non-target insects limited.

  15. Structure of a cellulose degrading bacterial community during anaerobic digestion.

    PubMed

    O'Sullivan, Cathryn A; Burrell, Paul C; Clarke, William P; Blackall, Linda L

    2005-12-30

    It is widely accepted that cellulose is the rate-limiting substrate in the anaerobic digestion of organic solid wastes and that cellulose solubilisation is largely mediated by surface attached bacteria. However, little is known about the identity or the ecophysiology of cellulolytic microorganisms from landfills and anaerobic digesters. The aim of this study was to investigate an enriched cellulolytic microbial community from an anaerobic batch reactor. Chemical oxygen demand balancing was used to calculate the cellulose solubilisation rate and the degree of cellulose solubilisation. Fluorescence in situ hybridisation (FISH) was used to assess the relative abundance and physical location of three groups of bacteria belonging to the Clostridium lineage of the Firmicutes that have been implicated as the dominant cellulose degraders in this system. Quantitation of the relative abundance using FISH showed that there were changes in the microbial community structure throughout the digestion. However, comparison of these results to the process data reveals that these changes had no impact on the cellulose solubilisation in the reactor. The rate of cellulose solubilisation was approximately stable for much of the digestion despite changes in the cellulolytic population. The solubilisation rate appears to be most strongly affected by the rate of surface area colonisation and the biofilm architecture with the accepted model of first order kinetics due to surface area limitation applying only when the cellulose particles are fully covered with a thin layer of cells. Copyright 2005 Wiley Periodicals, Inc

  16. Phylogenetic tree and community structure from a Tangled Nature model.

    PubMed

    Canko, Osman; Taşkın, Ferhat; Argın, Kamil

    2015-10-07

    In evolutionary biology, the taxonomy and origination of species are widely studied subjects. An estimation of the evolutionary tree can be done via available DNA sequence data. The calculation of the tree is made by well-known and frequently used methods such as maximum likelihood and neighbor-joining. In order to examine the results of these methods, an evolutionary tree is pursued computationally by a mathematical model, called Tangled Nature. A relatively small genome space is investigated due to computational burden and it is found that the actual and predicted trees are in reasonably good agreement in terms of shape. Moreover, the speciation and the resulting community structure of the food-web are investigated by modularity. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Unraveling the Molecular Mechanisms Underlying the Nasopharyngeal Bacterial Community Structure.

    PubMed

    de Steenhuijsen Piters, Wouter A A; Bogaert, Debby

    2016-02-02

    The upper respiratory tract is colonized by a diverse array of commensal bacteria that harbor potential pathogens, such as Streptococcus pneumoniae. As long as the local microbial ecosystem-also called "microbiome"-is in balance, these potentially pathogenic bacterial residents cause no harm to the host. However, similar to macrobiological ecosystems, when the bacterial community structure gets perturbed, potential pathogens can overtake the niche and cause mild to severe infections. Recent studies using next-generation sequencing show that S. pneumoniae, as well as other potential pathogens, might be kept at bay by certain commensal bacteria, including Corynebacterium and Dolosigranulum spp. Bomar and colleagues are the first to explore a specific biological mechanism contributing to the antagonistic interaction between Corynebacterium accolens and S. pneumoniae in vitro [L. Bomar, S. D. Brugger, B. H. Yost, S. S. Davies, K. P. Lemon, mBio 7(1):e01725-15, 2016, doi:10.1128/mBio.01725-15]. The authors comprehensively show that C. accolens is capable of hydrolyzing host triacylglycerols into free fatty acids, which display antipneumococcal properties, suggesting that these bacteria might contribute to the containment of pneumococcus. This work exemplifies how molecular epidemiological findings can lay the foundation for mechanistic studies to elucidate the host-microbe and microbial interspecies interactions underlying the bacterial community structure. Next, translation of these results to an in vivo setting seems necessary to unveil the magnitude and importance of the observed effect in its natural, polymicrobial setting. Copyright © 2016 de Steenhuijsen Piters and Bogaert.

  18. Unraveling the Molecular Mechanisms Underlying the Nasopharyngeal Bacterial Community Structure

    PubMed Central

    de Steenhuijsen Piters, Wouter A. A.

    2016-01-01

    ABSTRACT The upper respiratory tract is colonized by a diverse array of commensal bacteria that harbor potential pathogens, such as Streptococcus pneumoniae. As long as the local microbial ecosystem—also called “microbiome”—is in balance, these potentially pathogenic bacterial residents cause no harm to the host. However, similar to macrobiological ecosystems, when the bacterial community structure gets perturbed, potential pathogens can overtake the niche and cause mild to severe infections. Recent studies using next-generation sequencing show that S. pneumoniae, as well as other potential pathogens, might be kept at bay by certain commensal bacteria, including Corynebacterium and Dolosigranulum spp. Bomar and colleagues are the first to explore a specific biological mechanism contributing to the antagonistic interaction between Corynebacterium accolens and S. pneumoniae in vitro [L. Bomar, S. D. Brugger, B. H. Yost, S. S. Davies, K. P. Lemon, mBio 7(1):e01725-15, 2016, doi:10.1128/mBio.01725-15]. The authors comprehensively show that C. accolens is capable of hydrolyzing host triacylglycerols into free fatty acids, which display antipneumococcal properties, suggesting that these bacteria might contribute to the containment of pneumococcus. This work exemplifies how molecular epidemiological findings can lay the foundation for mechanistic studies to elucidate the host-microbe and microbial interspecies interactions underlying the bacterial community structure. Next, translation of these results to an in vivo setting seems necessary to unveil the magnitude and importance of the observed effect in its natural, polymicrobial setting. PMID:26838716

  19. An estimate of the percentage of non-predatory dead variability in coastal zooplankton of the southern Humboldt Current System.

    PubMed

    Krautz, M C; Hernández-Miranda, E; Veas, R; Bocaz, P; Riquelme, P; Quiñones, R A

    2017-12-01

    Non-predatory dead variability in zooplankton remains poorly quantified worldwide. Here, we make the first estimation of the percentage of dead organisms in coastal zooplankton communities in the Humboldt Current System (HCS) under in situ conditions. The study was conducted in four coastal sites of the southern HCS (between 36 and 37°S) over a period of one year. Percentages of dead organisms were based on the classification as live or dead of 158,220 holoplankton and 17,591 meroplankton individuals using neutral red staining technique. The percentage of dead organisms in total-zooplankton was between 4.3% in Coronel Bay (summer) and 76.9% in Llico (autumn). The percentage of dead total-holoplankton varied from 4.2% (Itata River Mouth; autumn) to 77.6% (Llico; autumn), while the percentage of dead total-meroplankton ranged from 1.5% to 56.8% in Coronel Bay and Coliumo Bay, respectively. The most abundant taxa analyzed were the copepods Acartia sp., Paracalanus sp., Calanoides sp., Cladocera, Polychaeta, and the eggs of anchoveta Engraulis ringens. Among these taxa, there was a high degree of interspecific variability in the estimation of the dead organisms. The Pearson correlation shows significant relationships between maximum temperature, and minimum salinity, with the percentage of dead individuals of Acartia sp. and Paracalanus sp. Environmental factors explaining those relationships were: the El Niño 2015-2016 event, and freshwater river runoff. The use of vital staining to estimate non-predatory death for total-zooplankton and selected sentinel species is a promising tool to establish baselines to evaluate natural perturbations (e.g. ENSO), and anthropogenic alterations in coastal pelagic ecosystems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. ORGANIC VS CONVENTIONAL: SOIL NEMATODE COMMUNITY STRUCTURE AND FUNCTION.

    PubMed

    Kapp, C; Storey, S G; Malan, A P

    2014-01-01

    Global increases in human population are creating an ever-greater need for food production. Poor soil management practices have degraded soil to such an extent that rapidly improved management practices is the only way to ensure future food demands. In South Africa, deciduous fruit producers are realising the need for soil health, and for an increased understanding of the benefits of soil ecology, to ensure sustainable fruit production. This depends heavily on improved orchard management. Conventional farming relies on the addition of artificial fertilizers, and the application of chemicals, to prevent or minimise, the effects of the soil stages of pest insects, and of plant-parasitic nematodes. Currently, there is resistance toward conventional farming practices, which, it is believed, diminishes biodiversity within the soil. The study aimed to establish the soil nematode community structure and function in organically, and conventionally, managed deciduous fruit orchards. This was done by determining the abundance, the diversity, and the functionality of the naturally occurring free-living, and plant-parasitic, nematodes in deciduous fruit orchards in the Western Cape province of South Africa. The objective of the study was to form the basis for the use of nematodes as future indicators of soil health in deciduous fruit orchards. Orchards from neighbouring organic, and conventional, apricot farms, and from an organic apple orchard, were studied. All the nematodes were quantified, and identified, to family level. The five nematode-classified trophic groups were found at each site, while 14 families were identified in each orchard, respectively. Herbivores were dominant in all the orchards surveyed. Organic apples had the fewest herbivores and fungivores, with the highest number of carnivores. When comparing organic with conventional apricot orchards, higher numbers of plant-parasitic nematodes were found in the organic apricot orchards. The Maturity Index (MI

  1. Epidemic spreading on complex networks with overlapping and non-overlapping community structure

    NASA Astrophysics Data System (ADS)

    Shang, Jiaxing; Liu, Lianchen; Li, Xin; Xie, Feng; Wu, Cheng

    2015-02-01

    Many real-world networks exhibit community structure where vertices belong to one or more communities. Recent studies show that community structure plays an import role in epidemic spreading. In this paper, we investigate how the extent of overlap among communities affects epidemics. In order to experiment on the characteristic of overlapping communities, we propose a rewiring algorithm that can change the community structure from overlapping to non-overlapping while maintaining the degree distribution of the network. We simulate the Susceptible-Infected-Susceptible (SIS) epidemic process on synthetic scale-free networks and real-world networks by applying our rewiring algorithm. Experiments show that epidemics spread faster on networks with higher level of overlapping communities. Furthermore, overlapping communities' effect interacts with the average degree's effect. Our work further illustrates the important role of overlapping communities in the process of epidemic spreading.

  2. Biodiversity and ecosystem function in species-poor communities: community structure and leaf litter breakdown in a Pacific island stream

    Jonathan P. Benstead; James G. March; Catherine M. Pringle; Katherine C. Ewel; John W. Short

    2009-01-01

    Pacific island stream communities are species-poor because of the effects of extreme geographic isolation on colonization rates of taxa common to continental regions. The effects of such low species richness on stream ecosystem function are not well understood. Here, we provide data on community structure and leaf litter breakdown rate in a virtually pristine stream on...

  3. Soil phosphorus depletion and shifts in plant communities change bacterial community structure in a long-term grassland management trial.

    PubMed

    Adair, Karen L; Wratten, Steve; Lear, Gavin

    2013-06-01

    Agricultural systems rely on healthy soils and their sustainability requires understanding the long-term impacts of agricultural practices on soils, including microbial communities. We examined the impact of 17 years of land management on soil bacterial communities in a New Zealand randomized-block pasture trial. Significant variation in bacterial community structure related to mowing and plant biomass removal, while nitrogen fertilizer had no effect. Changes in soil chemistry and legume abundance described 52% of the observed variation in the bacterial community structure. Legumes (Trifolium species) were absent in unmanaged plots but increased in abundance with management intensity; 11% of the variation in soil bacterial community structure was attributed to this shift in the plant community. Olsen P explained 10% of the observed heterogeneity, which is likely due to persistent biomass removal resulting in P limitation; Olsen P was significantly lower in plots with biomass removed (14 mg kg(-1) ± 1.3SE) compared with plots that were not mown, or where biomass was left after mowing (32 mg kg(-1) ± 1.6SE). Our results suggest that removal of plant biomass and associated phosphorus, as well as shifts in the plant community, have greater long-term impacts on soil bacterial community structure than application of nitrogen fertilizers. © 2013 John Wiley & Sons Ltd and Society for Applied Microbiology.

  4. Multisensor sampling of pelagic ecosystem variables in a coastal environment to estimate zooplankton grazing impact

    NASA Astrophysics Data System (ADS)

    Sutton, Tracey; Hopkins, Thomas; Remsen, Andrew; Burghart, Scott

    2001-01-01

    Sampling was conducted on the west Florida continental shelf ecosystem modeling site to estimate zooplankton grazing impact on primary production. Samples were collected with the high-resolution sampler, a towed array bearing electronic and optical sensors operating in tandem with a paired net/bottle verification system. A close biological-physical coupling was observed, with three main plankton communities: 1. a high-density inshore community dominated by larvaceans coincident with a salinity gradient; 2. a low-density offshore community dominated by small calanoid copepods coincident with the warm mixed layer; and 3. a high-density offshore community dominated by small poecilostomatoid and cyclopoid copepods and ostracods coincident with cooler, sub-pycnocline oceanic water. Both high-density communities were associated with relatively turbid water. Applying available grazing rates from the literature to our abundance data, grazing pressure mirrored the above bio-physical pattern, with the offshore sub-pycnocline community contributing ˜65% of grazing pressure despite representing only 19% of the total volume of the transect. This suggests that grazing pressure is highly localized, emphasizing the importance of high-resolution sampling to better understand plankton dynamics. A comparison of our grazing rate estimates with primary production estimates suggests that mesozooplankton do not control the fate of phytoplankton over much of the area studied (<5% grazing of daily primary production), but "hot spots" (˜25-50% grazing) do occur which may have an effect on floral composition.

  5. Linking the community structure of arbuscular mycorrhizal fungi and plants: a story of interdependence?

    PubMed Central

    Horn, Sebastian; Hempel, Stefan; Verbruggen, Erik; Rillig, Matthias C; Caruso, Tancredi

    2017-01-01

    Arbuscular mycorrhizal fungi (AMF) are crucial to plants and vice versa, but little is known about the factors linking the community structure of the two groups. We investigated the association between AMF and the plant community structure in the nearest neighborhood of Festuca brevipila in a semiarid grassland with steep environmental gradients, using high-throughput sequencing of the Glomeromycotina (former Glomeromycota). We focused on the Passenger, Driver and Habitat hypotheses: (i) plant communities drive AMF (passenger); (ii) AMF communities drive the plants (driver); (iii) the environment shapes both communities causing covariation. The null hypothesis is that the two assemblages are independent and this study offers a spatially explicit novel test of it in the field at multiple, small scales. The AMF community consisted of 71 operational taxonomic units, the plant community of 47 species. Spatial distance and spatial variation in the environment were the main determinants of the AMF community. The structure of the plant community around the focal plant was a poor predictor of AMF communities, also in terms of phylogenetic community structure. Some evidence supports the passenger hypothesis, but the relative roles of the factors structuring the two groups clearly differed, leading to an apparent decoupling of the two assemblages at the relatively small scale of this study. Community phylogenetic structure in AMF suggests an important role of within-assemblage interactions. PMID:28244977

  6. Linking the community structure of arbuscular mycorrhizal fungi and plants: a story of interdependence?

    PubMed

    Horn, Sebastian; Hempel, Stefan; Verbruggen, Erik; Rillig, Matthias C; Caruso, Tancredi

    2017-06-01

    Arbuscular mycorrhizal fungi (AMF) are crucial to plants and vice versa, but little is known about the factors linking the community structure of the two groups. We investigated the association between AMF and the plant community structure in the nearest neighborhood of Festuca brevipila in a semiarid grassland with steep environmental gradients, using high-throughput sequencing of the Glomeromycotina (former Glomeromycota). We focused on the Passenger, Driver and Habitat hypotheses: (i) plant communities drive AMF (passenger); (ii) AMF communities drive the plants (driver); (iii) the environment shapes both communities causing covariation. The null hypothesis is that the two assemblages are independent and this study offers a spatially explicit novel test of it in the field at multiple, small scales. The AMF community consisted of 71 operational taxonomic units, the plant community of 47 species. Spatial distance and spatial variation in the environment were the main determinants of the AMF community. The structure of the plant community around the focal plant was a poor predictor of AMF communities, also in terms of phylogenetic community structure. Some evidence supports the passenger hypothesis, but the relative roles of the factors structuring the two groups clearly differed, leading to an apparent decoupling of the two assemblages at the relatively small scale of this study. Community phylogenetic structure in AMF suggests an important role of within-assemblage interactions.

  7. Microzooplankton herbivory and community structure in the Amundsen Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Yang, Eun Jin; Jiang, Yong; Lee, SangHoon

    2016-01-01

    We examined microzooplankton abundance, community structure, and grazing impact on phytoplankton in the Amundsen Sea, Western Antarctica, during the early austral summer from December 2010 to January 2011. Our study area was divided into three regions based on topography, hydrographic properties, and trophic conditions: (1) the Oceanic Zone (OZ), with free sea ice and low phytoplankton biomass dominated by diatoms; (2) the Sea Ice Zone (SIZ), covered by heavy sea ice with colder water, lower salinity, and dominated by diatoms; and (3) the Amundsen Sea Polynya (ASP), with high phytoplankton biomass dominated by Phaeocystis antarctica. Microzooplankton biomass and communities associated with phytoplankton biomass and composition varied among regions. Heterotrophic dinoflagellates (HDF) were the most significant grazers in the ASP and OZ, whereas ciliates co-dominated with HDF in the SIZ. Microzooplankton grazing impact is significant in our study area, particularly in the ASP, and consumed 55.4-107.6% of phytoplankton production (average 77.3%), with grazing impact increasing with prey and grazer biomass. This result implies that a significant proportion of the phytoplankton production is not removed by sinking or other grazers but grazed by microzooplankton. Compared with diatom-based systems, Phaeocystis-based production would be largely remineralized and/or channeled through the microbial food web through microzooplankton grazing. In these waters the major herbivorous fate of phytoplankton is likely mediated by the microzooplankton population. Our study confirms the importance of herbivorous protists in the planktonic ecosystems of high latitudes. In conclusion, microzooplankton herbivory may be a driving force controlling phytoplankton growth in early summer in the Amundsen Sea, particularly in the ASP.

  8. Guided Pathways to Careers: Four Dimensions of Structure in Community College Career-Technical Programs

    ERIC Educational Resources Information Center

    Van Noy, Michelle; Trimble, Madeline; Jenkins, Davis; Barnett, Elisabeth; Wachen, John

    2016-01-01

    Objective: Some have hypothesized that community college programs are not sufficiently structured to support student success and that students would benefit from more highly structured programs. This study examines the specific ways that structure is expressed in policy and practice at representative community colleges. Method: Using data obtained…

  9. Four Structures for Marketing in the American Public Community College.

    ERIC Educational Resources Information Center

    Bogart, Quentin J.

    Prepared for college officials considering the development of marketing programs, this paper examines the distinctive marketing practices for four geographically separated, public community college districts: Coastline Community College (CCC), California; Metropolitan Community College District (MCCD), Missouri; Triton College (TC), Illinois; and…

  10. Are gay communities dying or just in transition? Results from an international consultation examining possible structural change in gay communities.

    PubMed

    Simon Rosser, B R; West, William; Weinmeyer, Richard

    2008-05-01

    This study sought to identify how urban gay communities are undergoing structural change, reasons for that change, and implications for HIV prevention planning. Key informants (N=29) at the AIDS Impact Conference from 17 cities in 14 countries completed surveys and participated in a facilitated structured dialog about if gay communities are changing, and if so, how they are changing. In all cities, the virtual gay community was identified as currently larger than the offline physical community. Most cities identified that while the gay population in their cities appeared stable or growing, the gay community appeared in decline. Measures included greater integration of heterosexuals into historically gay-identified neighborhoods and movement of gay persons into suburbs, decreased number of gay bars/clubs, less attendance at gay events, less volunteerism in gay or HIV/AIDS organizations, and the overall declining visibility of gay communities. Participants attributed structural change to multiple factors including gay neighborhood gentrification, achievement of civil rights, less discrimination, a vibrant virtual community, and changes in drug use. Consistent with social assimilation, gay infrastructure, visibility, and community identification appears to be decreasing across cities. HIV prevention planning, interventions, treatment services, and policies need to be re-conceptualized for MSM in the future. Four recommendations for future HIV prevention and research are detailed.

  11. Seasonal and interannual variation in the planktonic communities of the northeastern Chukchi Sea during the summer and early fall

    NASA Astrophysics Data System (ADS)

    Questel, Jennifer M.; Clarke, Cheryl; Hopcroft, Russell R.

    2013-09-01

    We analyzed the seasonal and interannual variability of the planktonic communities in a densely sampled region of the northeastern Chukchi Sea as part of a multidisciplinary ecosystem study from 2008 to 2010. Observations of chlorophyll-a, inorganic macronutrients, and zooplankton (using both 150-μm and 505-μm mesh nets) were made within two 900-NM 2 grids (Klondike and Burger) at high spatial resolution three times each in 2008 and 2009, with a third grid (Statoil) sampled twice in 2010. Sea-ice conditions prior to sampling varied notably during the study: seasonal sea ice retreat was earlier and sea-surface temperatures (SSTs) were warmer in 2009 than in 2008, whereas SSTs for 2010 were intermediate between the 2008 and 2009 values. Eighty taxonomic categories of zooplankton, including 11 meroplanktonic categories, were recorded, with the greatest diversity found within the copepods (25 species), followed by the cnidarians (11 species). All species are typical for the region and most are seeded from the Bering Sea. A seasonal progression of the community structure was apparent over each survey area and was likely influenced by temperature. Cold oceanographic conditions in 2008 likely slowed growth and development of the zooplankton, such that holozooplankton abundance averaged 2389 and 106 individuals m-3 and biomass averaged 10.5 and 8.3 mg DW m-3 in the 150- and 505-μm nets, respectively. An early phytoplankton bloom in 2009 apparently supported a zooplankton community of greater abundance, but moderate biomass, averaging 6842 and 189 individuals m-3, and 16.3 and 7.0 mg DW m-3 in the 150- and 505-μm nets, respectively. Highest zooplankton abundance and biomass values among the three years occurred in 2010: 7396 and 198 individuals m-3 and 102.9 and 33.5 mg DW m-3 in the 150- and 505-μm nets, respectively. Holozooplankton biomass changes were driven by increases in large-bodied, lipid-rich copepods. The contribution of meroplankton was substantial in this

  12. In situ camera observations reveal major role of zooplankton in modulating marine snow formation during an upwelling-induced plankton bloom

    NASA Astrophysics Data System (ADS)

    Taucher, Jan; Stange, Paul; Algueró-Muñiz, María; Bach, Lennart T.; Nauendorf, Alice; Kolzenburg, Regina; Büdenbender, Jan; Riebesell, Ulf

    2018-05-01

    Particle aggregation and the consequent formation of marine snow alter important properties of biogenic particles (size, sinking rate, degradability), thus playing a key role in controlling the vertical flux of organic matter to the deep ocean. However, there are still large uncertainties about rates and mechanisms of particle aggregation, as well as the role of plankton community structure in modifying biomass transfer from small particles to large fast-sinking aggregates. Here we present data from a high-resolution underwater camera system that we used to observe particle size distributions and formation of marine snow (aggregates >0.5 mm) over the course of a 9-week in situ mesocosm experiment in the Eastern Subtropical North Atlantic. After an oligotrophic phase of almost 4 weeks, addition of nutrient-rich deep water (650 m) initiated the development of a pronounced diatom bloom and the subsequent formation of large marine snow aggregates in all 8 mesocosms. We observed a substantial time lag between the peaks of chlorophyll a and marine snow biovolume of 9-12 days, which is much longer than previously reported and indicates a marked temporal decoupling of phytoplankton growth and marine snow formation during our study. Despite this time lag, our observations revealed substantial transfer of biomass from small particle sizes (single phytoplankton cells and chains) to marine snow aggregates of up to 2.5 mm diameter (ESD), with most of the biovolume being contained in the 0.5-1 mm size range. Notably, the abundance and community composition of mesozooplankton had a substantial influence on the temporal development of particle size spectra and formation of marine snow aggregates: While higher copepod abundances were related to reduced aggregate formation and biomass transfer towards larger particle sizes, the presence of appendicularia and doliolids enhanced formation of large marine snow. Furthermore, we combined in situ particle size distributions with

  13. The Effect of Dilution on the Structure of Microbial Communities

    NASA Technical Reports Server (NTRS)

    Mills, Aaron L.

    2000-01-01

    To determine how dilution of microbial communities affects the diversity of the diluted assemblage a series of numerical simulations were conducted that determined the theoretical change in diversity, richness, and evenness of the community with serial dilution. The results of the simulation suggested that the effects are non linear with a high degree of dependence on the initial evenness of the community being diluted. A series of incubation experiments using a range of dilutions of raw sewage as an inoculum into sterile sewage was used for comparison to the simulations. The diluted communities were maintained in batch fed reactors (three day retention time) for nine days. The communities were harvested and examined by conventional plating and by molecular analysis of the whole-community DNA using AFLP and T-RFLP. Additional, CLPP analysis was also applied. The effects on richness predicted by the numerical simulations were confirmed by the analyses used. The diluted communities fell into three groups, a low dilution, intermediate dilution, and high dilution group, which corresponded well with the groupings obtained for community richness in simulation. The grouping demonstrated the non-linear nature of dilution of whole communities. Furthermore, the results implied that the undiluted community consisted of a few dominant types accompanied by a number of rare (low abundance) types as is typical in unevenly distributed communities.

  14. Bacterial bioluminescence as a lure for marine zooplankton and fish.

    PubMed

    Zarubin, Margarita; Belkin, Shimshon; Ionescu, Michael; Genin, Amatzia

    2012-01-17

    The benefits of bioluminescence for nonsymbiotic marine bacteria have not been elucidated fully. One of the most commonly cited explanations, proposed more than 30 y ago, is that bioluminescence augments the propagation and dispersal of bacteria by attracting fish to consume the luminous material. This hypothesis, based mostly on the prevalence of luminous bacteria in fish guts, has not been tested experimentally. Here we show that zooplankton that contacts and feeds on the luminescent bacterium Photobacterium leiognathi starts to glow, and demonstrate by video recordings that glowing individuals are highly vulnerable to predation by nocturnal fish. Glowing bacteria thereby are transferred to the nutritious guts of fish and zooplankton, where they survive digestion and gain effective means for growth and dispersal. Using bioluminescence as bait appears to be highly beneficial for marine bacteria, especially in food-deprived environments of the deep sea.

  15. Bacterial bioluminescence as a lure for marine zooplankton and fish

    PubMed Central

    Zarubin, Margarita; Belkin, Shimshon; Ionescu, Michael; Genin, Amatzia

    2012-01-01

    The benefits of bioluminescence for nonsymbiotic marine bacteria have not been elucidated fully. One of the most commonly cited explanations, proposed more than 30 y ago, is that bioluminescence augments the propagation and dispersal of bacteria by attracting fish to consume the luminous material. This hypothesis, based mostly on the prevalence of luminous bacteria in fish guts, has not been tested experimentally. Here we show that zooplankton that contacts and feeds on the luminescent bacterium Photobacterium leiognathi starts to glow, and demonstrate by video recordings that glowing individuals are highly vulnerable to predation by nocturnal fish. Glowing bacteria thereby are transferred to the nutritious guts of fish and zooplankton, where they survive digestion and gain effective means for growth and dispersal. Using bioluminescence as bait appears to be highly beneficial for marine bacteria, especially in food-deprived environments of the deep sea. PMID:22203999

  16. Mesozooplankton structure and functioning during the onset of the Kerguelen phytoplankton bloom during the Keops2 survey

    NASA Astrophysics Data System (ADS)

    Carlotti, F.; Jouandet, M.-P.; Nowaczyk, A.; Harmelin-Vivien, M.; Lefèvre, D.; Guillou, G.; Zhu, Y.; Zhou, M.

    2015-02-01

    This study presents results on the zooplankton response to the early phase of the northeastern Kerguelen bloom during the KEOPS2 survey (15 October-20 November 2011). The campaign combined a large coverage of the eastern part of the shelf and the adjacent oceanic regions with 2 quasi-perpendicular transects oriented south to north (between 49°08' and 46°50' S) and west to east (between 69°50' and 74°60' E) aiming to document the spatial extension of the bloom and its coastal-off shore gradient, and a pseudo-lagrangian survey located in a complex recirculation zone in a stationary meander of the Polar front nearly centered at the crossing of the 2 initial transects. In addition, 8 stations were performed for 24 h observations, distributed in key areas and some of them common with the KEOPS1 cruise (January-February 2005). The mesozooplankton biomass stocks observed at the beginning of the KEOPS2 cruise were around 2 g C m-2 both above the plateau and in oceanic waters. Zooplankton biomasses in oceanic waters were maintained in average below 2 g C m-2 over the study period, except for one station in the Polar Front Zone (FL), whereas zooplankton biomasses were around 4 g C m-2 on the plateau at the end of the cruise. Taxonomic composition and stable isotope ratios of size-fractionated zooplankton indicated the strong domination of herbivores. The most remarkable feature during the sampling period was the stronger increase in the integrated 0-250 m abundances in the oceanic waters (25 × 103 to 160 × 103 ind m-2) than on the plateau (25 × 103 to 90 × 103 ind m-2). The size structure and taxonomic distributions revealed a cumulative contribution of various larval stages of dominant copepods and euphausiids particularly in the oceanic waters, with clearly identifiable stages of progress during the Lagrangian survey. These different results during KEOPS2 suggested that the zooplankton community was able to respond to the growing phytoplankton blooms earlier on the

  17. Spatial variation of phytoplankton community structure in Daya Bay, China.

    PubMed

    Jiang, Zhao-Yu; Wang, You-Shao; Cheng, Hao; Zhang, Jian-Dong; Fei, Jiao

    2015-10-01

    Daya Bay is one of the largest and most important gulfs in the southern coast of China, in the northern part of the South China Sea. The phylogenetic diversity and spatial distribution of phytoplankton from the Daya Bay surface water and the relationship with the in situ water environment were investigated by the clone library of the large subunit of ribulose-1, 5-bisphosphate carboxylase (rbcL) gene. The dominant species of phytoplankton were diatoms and eustigmatophytes, which accounted for 81.9 % of all the clones of the rbcL genes. Prymnesiophytes were widely spread and wide varieties lived in Daya Bay, whereas the quantity was limited. The community structure of phytoplankton was shaped by pH and salinity and the concentration of silicate, phosphorus and nitrite. The phytoplankton biomass was significantly positively affected by phosphorus and nitrite but negatively by salinity and pH. Therefore, the phytoplankton distribution and biomass from Daya Bay were doubly affected by anthropic activities and natural factors.

  18. Evidence for the functional significance of diazotroph community structure in soil.

    PubMed

    Hsu, Shi-Fang; Buckley, Daniel H

    2009-01-01

    Microbial ecologists continue to seek a greater understanding of the factors that govern the ecological significance of microbial community structure. Changes in community structure have been shown to have functional significance for processes that are mediated by a narrow spectrum of organisms, such as nitrification and denitrification, but in some cases, functional redundancy in the community seems to buffer microbial ecosystem processes. The functional significance of microbial community structure is frequently obscured by environmental variation and is hard to detect in short-term experiments. We examine the functional significance of free-living diazotrophs in a replicated long-term tillage experiment in which extraneous variation is minimized and N-fixation rates can be related to soil characteristics and diazotroph community structure. Soil characteristics were found to be primarily impacted by tillage management, whereas N-fixation rates and diazotroph community structure were impacted by both biomass management practices and interactions between tillage and biomass management. The data suggest that the variation in diazotroph community structure has a greater impact on N-fixation rates than do soil characteristics at the site. N-fixation rates displayed a saturating response to increases in diazotroph community diversity. These results show that the changes in the community structure of free-living diazotrophs in soils can have ecological significance and suggest that this response is related to a change in community diversity.

  19. Zooplankton fecal pellets link fossil fuel and phosphate deposits

    Porter, K.G.; Robbins, E.I.

    1981-01-01

    Fossil zooplankton fecal pellets found in thinly bedded marine and lacustrine black shales associated with phosphate, oil, and coal deposits, link the deposition of organic matter and biologically associated minerals with planktonic ecosystems. The black shales were probably formed in the anoxic basins of coastal marine waters, inland seas, and rift valley lakes where high productivity was supported by runoff, upwelling, and outwelling. Copyright ?? 1981 AAAS.

  20. Ingestion of Microplastics by Zooplankton in the Northeast Pacific Ocean.

    PubMed

    Desforges, Jean-Pierre W; Galbraith, Moira; Ross, Peter S

    2015-10-01

    Microplastics are increasingly recognized as being widespread in the world's oceans, but relatively little is known about ingestion by marine biota. In light of the potential for microplastic fibers and fragments to be taken up by small marine organisms, we examined plastic ingestion by two foundation species near the base of North Pacific marine food webs, the calanoid copepod Neocalanus cristatus and the euphausiid Euphausia pacifia. We developed an acid digestion method to assess plastic ingestion by individual zooplankton and detected microplastics in both species. Encounter rates resulting from ingestion were 1 particle/every 34 copepods and 1/every 17 euphausiids (euphausiids > copepods; p = 0.01). Consistent with differences in the size selection of food between these two zooplankton species, the ingested particle size was greater in euphausiids (816 ± 108 μm) than in copepods (556 ± 149 μm) (p = 0.014). The contribution of ingested microplastic fibres to total plastic decreased with distance from shore in euphausiids (r (2) = 70, p = 0.003), corresponding to patterns in our previous observations of microplastics in seawater samples from the same locations. This first evidence of microplastic ingestion by marine zooplankton indicate that species at lower trophic levels of the marine food web are mistaking plastic for food, which raises fundamental questions about potential risks to higher trophic level species. One concern is risk to salmon: We estimate that consumption of microplastic-containing zooplankton will lead to the ingestion of 2-7 microplastic particles/day by individual juvenile salmon in coastal British Columbia, and ≤91 microplastic particles/day in returning adults.

  1. Development and Applications of Technology for Sensing Zooplankton

    DTIC Science & Technology

    2003-09-30

    zooplankton-like particles. WORK COMPLETED In support of our first objective, in prior years we occupied sites in both East and West Sound at Orcas ...Island in northern Puget Sound , WA. We have also made deployments at four sites on open linear coasts, including one just north of Oceanside, CA (Red...layers. Multi-static, multi-frequency methods Most active bioacoustical methods in oceanography exclusively utilize the sound that is scattered

  2. Deep-water zooplankton of the Guaymas basin hydrothermal vent field

    NASA Astrophysics Data System (ADS)

    Wiebe, Peter H.; Copley, Nancy; Van Dover, Cindy; Tamse, Armando; Manrique, Fernando

    1988-06-01

    Zooplankton from the Guaymas Basin deep-sea vent field were collected with a 1 m 2 MOCNESS to examine the distribution of total standing stock, taxonomic composition, size-frequency distribution of zooplankton, and the species composition of calanoid copepods. Low altitude (˜ 100 m above the bottom) horizontal tows along and across the axis of the basin's southern trough, and oblique tows from the bottom of the basin (˜ 2000 m) to the surface were made. Total biomass in near-bottom samples (range: 13-46 cc/1000 m 3) was only about a factor of 10 lower than in the upper 100 m. However, there was little or no evidence for enrichment of biomass in the ˜ 100 m zone above the vent site relative to biomass at the same depth horizon over non-vent areas. Total numbers of individuals ranged between 2600 and 4800/1000 m 3. Calanoid copepods consistently ranked first in abundance of counts of the taxa, followed by cyclopoid copepods, ostracods, chaetognaths, and amphipods. Other less abundant taxa, but in some cases important contributors to total biomass, were coelenterates (siphonophores, medusae), decapod shrimp, and polychaetes. Size-frequency analysis of individuals from each taxon indicated that the biomass and abundance spectra do not fit the theoretically expected spectra based on weight-dependent metabolism and growth. The pyramid of biomass was substantially different from the pyramid of numbers in this deep-sea community. Of the 67 species of copepods identified in two samples taken on low altitude tows, only 15 co-occurred in both samples. Many of the species in this relatively diverse community remain to be described. Larval and post-larval forms of benthic clams, gastropods, polychaetes, and crustaceans associated with the vents were collected 100-200 m above the southern trough, indicating the post-larvae may play an active role in dispersal of hydrothermal vent species.

  3. The contribution of zooplankton faecal pellets to deep-carbon transport in the Scotia Sea (Southern Ocean)

    NASA Astrophysics Data System (ADS)

    Manno, C.; Stowasser, G.; Enderlein, P.; Fielding, S.; Tarling, G. A.

    2015-03-01

    The northern Scotia Sea contains the largest seasonal uptake of atmospheric carbon dioxide yet measured in the Southern Ocean. This study examines one of the main routes by which this carbon fluxes to the deep ocean: through the production of faecal pellets (FPs) by the zooplankton community. Deep sediment traps were deployed at two sites with contrasting ocean productivity regimes (P3, naturally iron-fertilized, and P2, iron-limited) within the same water mass. The magnitude and seasonal pattern of particulate organic carbon (POC) and FPs in the traps was markedly different between the two sites. Maximum fluxes at P3 (22.91 mg C m-2 d-1; 2534 FP m-2 d1) were 1 order of magnitude higher than at P2 (4.01 mg C m-2 d-1; 915 FP m-2 d1, with flux at P3 exhibiting a double seasonal peak, compared to a single flatter peak at P2. The maximum contribution of FP carbon to the total amount of POC was twice as high at P3 (91%) compared to P2 (40%). The dominant FP category at P3 varied between round, ovoidal, cylindrical and tabular over the course of the year, while, at P2, ovoidal FPs were consistently dominant, always making up more than 60% of the FP assemblage. There was also a difference in the FP state between the two sites, with FPs being relatively intact at P3, while FPs were often fragmented with broken peritrophic membranes at P2. The exception was ovoidal FPs, which were relatively intact at both sites. Our observations suggest that there was a community shift from a herbivorous to an omnivorous diet from spring through to autumn at P3, while detritivores had a higher relative importance over the year at P2. Furthermore, the flux was mainly a product of the vertically migrating zooplankton community at P3, while the FP flux was more likely to be generated by deeper-dwelling zooplankton feeding on recycled material at P2. The results demonstrate that the feeding behaviour and vertical distribution of the zooplankton community plays a critical role in controlling

  4. Aquatic community structure in Mediterranean edge-of-field waterbodies as explained by environmental factors and the presence of pesticide mixtures.

    PubMed

    Pereira, Ana Santos; Dâmaso-Rodrigues, Maria Luísa; Amorim, Ana; Daam, Michiel A; Cerejeira, Maria José

    2018-06-16

    Studies addressing the predicted effects of pesticides in combination with abiotic and biotic factors on aquatic biota in ditches associated with typical Mediterranean agroecosystems are scarce. The current study aimed to evaluate the predicted effects of pesticides along with environmental factors and biota interactions on macroinvertebrate, zooplankton and phytoplankton community compositions in ditches adjacent to Portuguese maize and tomato crop areas. Data was analysed with the variance partitioning procedure based on redundancy analysis (RDA). The total variance in biological community composition was divided into the variance explained by the multi-substance potentially affected fraction [(msPAF) arthropods and primary producers], environmental factors (water chemistry parameters), biotic interactions, shared variance, and unexplained variance. The total explained variance reached 39.4% and the largest proportion of this explained variance was attributed to msPAF (23.7%). When each group (phytoplankton, zooplankton and macroinvertebrates) was analysed separately, biota interactions and environmental factors explained the largest proportion of variance. Results of this study indicate that besides the presence of pesticide mixtures, environmental factors and biotic interactions also considerably influence field freshwater communities. Subsequently, to increase our understanding of the risk of pesticide mixtures on ecosystem communities in edge-of-field water bodies, variations in environmental and biological factors should also be considered.

  5. Small-scale zooplankton aggregations at the front of a Kuroshio warm-core ring

    NASA Astrophysics Data System (ADS)

    Yamamoto, Tamiji; Nishizawa, Satoshi

    1986-11-01

    A Longhurst-Hardy Plankton Recorder was used to study the small-scale zooplankton distribution across the front of a Kuroshio warm-core ring in June 1979. Zooplankton were strongly aggregated in the frontal region; patches of zooplankton and phytoplankton were spatially separated. A major part of the zooplankton assemblage consisted of neritic forms such as cladocerans and indicator species of the cold Oyashio water. This implies that lateral entrainment of coastal waters, which is directly influenced by the Oyashio, was an important factor in the formation of the aggregations at the Kuroshio warm-core ring front. Variation in the distribution of abundance peaks of individual zooplankton species was also observed. Futhermore, zooplankton showed more intensive non-randomness (aggregation) than phytoplankton and non-motile euphausiid's eggs. Thus, biological processes, such as motility and prey-predator interaction, also appeared to be regulating the patchiness.

  6. Terrestrial carbohydrates support freshwater zooplankton during phytoplankton deficiency.

    PubMed

    Taipale, Sami J; Galloway, Aaron W E; Aalto, Sanni L; Kahilainen, Kimmo K; Strandberg, Ursula; Kankaala, Paula

    2016-08-11

    Freshwater food webs can be partly supported by terrestrial primary production, often deriving from plant litter of surrounding catchment vegetation. Although consisting mainly of poorly bioavailable lignin, with low protein and lipid content, the carbohydrates from fallen tree leaves and shoreline vegetation may be utilized by aquatic consumers. Here we show that during phytoplankton deficiency, zooplankton (Daphnia magna) can benefit from terrestrial particulate organic matter by using terrestrial-origin carbohydrates for energy and sparing essential fatty acids and amino acids for somatic growth and reproduction. Assimilated terrestrial-origin fatty acids from shoreline reed particles exceeded available diet, indicating that Daphnia may convert a part of their dietary carbohydrates to saturated fatty acids. This conversion was not observed with birch leaf diets, which had lower carbohydrate content. Subsequent analysis of 21 boreal and subarctic lakes showed that diet of herbivorous zooplankton is mainly based on high-quality phytoplankton rich in essential polyunsaturated fatty acids. The proportion of low-quality diets (bacteria and terrestrial particulate organic matter) was <28% of the assimilated carbon. Taken collectively, the incorporation of terrestrial carbon into zooplankton was not directly related to the concentration of terrestrial organic matter in experiments or lakes, but rather to the low availability of phytoplankton.

  7. Terrestrial carbohydrates support freshwater zooplankton during phytoplankton deficiency

    PubMed Central

    Taipale, Sami J.; Galloway, Aaron W. E.; Aalto, Sanni L.; Kahilainen, Kimmo K.; Strandberg, Ursula; Kankaala, Paula

    2016-01-01

    Freshwater food webs can be partly supported by terrestrial primary production, often deriving from plant litter of surrounding catchment vegetation. Although consisting mainly of poorly bioavailable lignin, with low protein and lipid content, the carbohydrates from fallen tree leaves and shoreline vegetation may be utilized by aquatic consumers. Here we show that during phytoplankton deficiency, zooplankton (Daphnia magna) can benefit from terrestrial particulate organic matter by using terrestrial-origin carbohydrates for energy and sparing essential fatty acids and amino acids for somatic growth and reproduction. Assimilated terrestrial-origin fatty acids from shoreline reed particles exceeded available diet, indicating that Daphnia may convert a part of their dietary carbohydrates to saturated fatty acids. This conversion was not observed with birch leaf diets, which had lower carbohydrate content. Subsequent analysis of 21 boreal and subarctic lakes showed that diet of herbivorous zooplankton is mainly based on high-quality phytoplankton rich in essential polyunsaturated fatty acids. The proportion of low-quality diets (bacteria and terrestrial particulate organic matter) was <28% of the assimilated carbon. Taken collectively, the incorporation of terrestrial carbon into zooplankton was not directly related to the concentration of terrestrial organic matter in experiments or lakes, but rather to the low availability of phytoplankton. PMID:27510848

  8. SEAPODYM-LTL: a parsimonious zooplankton dynamic biomass model

    NASA Astrophysics Data System (ADS)

    Conchon, Anna; Lehodey, Patrick; Gehlen, Marion; Titaud, Olivier; Senina, Inna; Séférian, Roland

    2017-04-01

    Mesozooplankton organisms are of critical importance for the understanding of early life history of most fish stocks, as well as the nutrient cycles in the ocean. Ongoing climate change and the need for improved approaches to the management of living marine resources has driven recent advances in zooplankton modelling. The classical modeling approach tends to describe the whole biogeochemical and plankton cycle with increasing complexity. We propose here a different and parsimonious zooplankton dynamic biomass model (SEAPODYM-LTL) that is cost efficient and can be advantageously coupled with primary production estimated either from satellite derived ocean color data or biogeochemical models. In addition, the adjoint code of the model is developed allowing a robust optimization approach for estimating the few parameters of the model. In this study, we run the first optimization experiments using a global database of climatological zooplankton biomass data and we make a comparative analysis to assess the importance of resolution and primary production inputs on model fit to observations. We also compare SEAPODYM-LTL outputs to those produced by a more complex biogeochemical model (PISCES) but sharing the same physical forcings.

  9. Estuarine and marine diets of out-migrating Chinook Salmon smolts in relation to local zooplankton populations, including harmful blooms

    NASA Astrophysics Data System (ADS)

    Chittenden, C. M.; Sweeting, R.; Neville, C. M.; Young, K.; Galbraith, M.; Carmack, E.; Vagle, S.; Dempsey, M.; Eert, J.; Beamish, R. J.

    2018-01-01

    Changes in food availability during the early marine phase of wild Chinook Salmon (O. tshawytscha) are being investigated as a cause of their recent declines in the Salish Sea. The marine survival of hatchery smolts, in particular, has been poor. This part of the Salish Sea Marine Survival Project examined the diet of young out-migrating Chinook Salmon for four consecutive years in the Cowichan River estuary and in Cowichan Bay, British Columbia, Canada. Local zooplankton communities were monitored during the final year of the study in the Cowichan River estuary, Cowichan Bay, and eastward to the Salish Sea to better understand the bottom-up processes that may be affecting Chinook Salmon survival. Rearing environment affected body size, diet, and distribution in the study area. Clipped smolts (hatchery-reared) were larger than the unclipped smolts (primarily naturally-reared), ate larger prey, spent very little time in the estuary, and disappeared from the bay earlier, likely due to emigration or mortality. Their larger body size may be a disadvantage for hatchery smolts if it necessitates their leaving the estuary prematurely to meet energy needs; the onset of piscivory began at a forklength of approximately 74 mm, which was less than the average forklength of the clipped fish in this study. The primary zooplankton bloom occurred during the last week of April/first week of May 2013, whereas the main release of hatchery-reared Chinook Salmon smolts occurs each year in mid-May-this timing mismatch may reduce their survival. Gut fullness was correlated with zooplankton biomass; however, both the clipped and unclipped smolts were not observed in the bay until the bloom of harmful Noctiluca was finished-20 days after the maximum recorded zooplankton abundance. Jellyfish medusa flourished in nearshore areas, becoming less prevalent towards the deeper waters of the Salish Sea. The sizable presence of Noctiluca and jellyfish in the zooplankton blooms may be repelling

  10. Refugee Adaptation and Community Structure: The Indochinese in Quebec City, Canada.

    ERIC Educational Resources Information Center

    Dorais, Louis-Jacques

    1991-01-01

    The ways in which Vietnamese, Cambodians, and Laotians now living in Quebec City (Canada) have established over the last 10-15 years distinct ethnic communities are discussed, and their community structure is described. A limited comparison with some other Indochinese communities highlights some features of the Quebec ethnic groups. (SLD)

  11. CHANGES IN EARTHWORM DENSITY AND COMMUNITY STRUCTURE DURING SECONDARY SUCCESSION IN ABANDONED TROPICAL PASTURES

    Xiaoming Zou; Grizelle Gonzalez

    1997-01-01

    Plant community succession alters the quantity and chemistry of organic inputs to soils. These differences in organic input may trigger changes in soil fertility and fauna1 activity. We examined earthworm density and community structure along a successional sequence of plant communities in abandoned tropical pastures in Puerto Rico. The chronological sequence of these...

  12. Detection of forest stand-level spatial structure in ectomycorrhizal fungal communities

    Erik A. Lilleskov; Thomas D. Bruns; Thomas R. Horton; D. Lee Taylor; Paul Grogan

    2004-01-01

    Ectomycorrhizal fungal (EMF) communities are highly diverse at the stand level. To begin to understand what might lead to such diversity, and to improve sampling designs, we investigated the spatial structure of these communities. We used EMF community data from a number of studies carried out in seven mature and one recently fire-initiated forest stand. We applied...

  13. Plant and litter influences on earthworm abundance and community structures in a tropical wet forest

    G. Gonzalez; X. Zou

    1999-01-01

    Plant communities differ in species composition and litter input. To examine the influence of plant species on the abundance and community structure of soil fauna, we sampled earthworms in areas close to and away from the bases of Dacryodes excelsa and Heliconia caribaea, two distinct plant communities within a tropical wet forest in Puerto Rico. We also carried out a...

  14. Development of a Method to Determine the Number of Viable Organisms or- 50 micrometers (Nominally Zooplankton) in Ships’ Ballast Water: A Combination of Two Vital, Fluorescent Stains

    DTIC Science & Technology

    2010-04-23

    dimension: ≥ 50 µm (nominally zooplankton), ≥ 10 µm and < 50 µm (nominally protists ), and < 10 µm (nominally bacteria). The IMO convention specifies the... protists comprise a small – but consistently present – fraction of the organisms found in the ≥ 50 µm size class, and many of these protists do...38 to 325 organisms l-1 from July 2008 to July 2009, and the community was consistently dominated by crustaceans except during summer protist blooms

  15. Plant Communities Rather than Soil Properties Structure Arbuscular Mycorrhizal Fungal Communities along Primary Succession on a Mine Spoil

    PubMed Central

    Krüger, Claudia; Kohout, Petr; Janoušková, Martina; Püschel, David; Frouz, Jan; Rydlová, Jana

    2017-01-01

    Arbuscular mycorrhizal fungal (AMF) community assembly during primary succession has so far received little attention. It remains therefore unclear, which of the factors, driving AMF community composition, are important during ecosystem development. We addressed this question on a large spoil heap, which provides a mosaic of sites in different successional stages under different managements. We selected 24 sites of c. 12, 20, 30, or 50 years in age, including sites with spontaneously developing vegetation and sites reclaimed by alder plantations. On each site, we sampled twice a year roots of the perennial rhizomatous grass Calamagrostis epigejos (Poaceae) to determine AMF root colonization and diversity (using 454-sequencing), determined the soil chemical properties and composition of plant communities. AMF taxa richness was unaffected by site age, but AMF composition variation increased along the chronosequences. AMF communities were unaffected by soil chemistry, but related to the composition of neighboring plant communities of the sampled C. epigejos plants. In contrast, the plant communities of the sites were more distinctively structured than the AMF communities along the four successional stages. We conclude that AMF and plant community successions respond to different factors. AMF communities seem to be influenced by biotic rather than by abiotic factors and to diverge with successional age. PMID:28473828

  16. Oxygen and the spatial structure of microbial communities.

    PubMed

    Fenchel, Tom; Finlay, Bland

    2008-11-01

    Oxygen has two faces. On one side it is the terminal electron acceptor of aerobic respiration - the most efficient engine of energy metabolism. On the other hand, oxygen is toxic because the reduction of molecular O2 creates reactive oxygen species such as the superoxide anion, peroxide, and the hydroxyl radical. Probably most prokaryotes, and virtually all eukaryotes, depend on oxygen respiration, and we show that the ambiguous relation to oxygen is both an evolutionary force and a dominating factor driving functional interactions and the spatial structure of microbial communities.We focus on microbial communities that are specialised for life in concentration gradients of oxygen, where they acquire the full panoply of specific requirements from limited ranges of PO2, which also support the spatial organisation of microbial communities. Marine and lake sediments provide examples of steep O2 gradients, which arise because consumption or production of oxygen exceeds transport rates of molecular diffusion. Deep lakes undergo thermal stratification in warm waters, resulting in seasonal anaerobiosis below the thermocline, and lakes with a permanent pycnocline often have permanent anoxic deep water. The oxycline is here biologically similar to sediments, and it harbours similar microbial biota, the main difference being the spatial scale. In sediments, transport is dominated by molecular diffusion, and in the water column, turbulent mixing dominates vertical transport. Cell size determines the minimum requirement of aerobic organisms. For bacteria (and mitochondria), the half-saturation constant for oxygen uptake ranges within 0.05-0.1% atmospheric saturation; for the amoeba Acanthamoeba castellanii it is 0.2%, and for two ciliate species measuring around 150 microm, it is 1-2 % atmospheric saturation. Protection against O2 toxicity has an energetic cost that increases with increasing ambient O2 tension. Oxygen sensing seems universal in aquatic organisms. Many aspects

  17. A Comparison of Microbial Community Structures by Depth and Season Under Switchgrass

    NASA Astrophysics Data System (ADS)

    Fansler, S. J.; Smith, J. L.; Bolton, H.; Bailey, V. L.

    2008-12-01

    As part of a multidisciplinary study of C sequestration in switchgrass production systems, the soil microbial community structure was monitored at 6 different depths (reaching 90 cm) in both spring and autumn. Microbial community structure was assessed using ribosomal intergenic spacer analysis (RISA), and primers were used specific to either bacteria or fungi, generating microbial community fingerprints for each taxonomic group. Diverse microbial communities for both groups were detected throughout the soil profile. It is notable that while community structure clearly changed with depth, there was the deepest soil samples still retained relatively diverse communities. Seasonally, differences are clearly evident within plots at the surface. As the plots were replicated, significant differences in the community fingerprints with depth and season are reported.

  18. Mixture of commercial herbicides based on 2,4-D and glyphosate mixture can suppress the emergence of zooplankton from sediments.

    PubMed

    Portinho, Jorge L; Nielsen, Daryl L; Daré, Luana; Henry, Raoul; Oliveira, Régis C; Branco, Ciro C Z

    2018-07-01

    It is generally assumed that zooplankton can recolonize lakes that have been exposed to pesticides, via their dormant egg banks. Hitherto, few studies have evaluated the relative importance of dormant egg bank recruitment in the re-establishment of zooplankton communities in the presence of pesticide. This study investigated the effects of commercial products Bratt ® (a.i. 2,4-D), Roundup ® (a.i. glyphosate) and their mixture on the emergence (abundance and taxon richness) of dormant zooplankton egg banks from natural lake sediment. Sediment samples were collected from the surface sediment (<10 cm depth) in four lakes in Southeast São Paulo, Brazil. We performed a hatching experiment, in which natural lake sediments containing dormant eggs were exposed separately to Bratt ® (applied concentrations ranging from 0.30 to 20 mg L -1 ), Roundup ® (0.28-8.5 mg L -1 ), and combined mixtures of all concentrations, plus one control (non-exposure to formulated herbicides) for a period of 28 days. All tested concentrations of Bratt ® , Roundup ® and their mixture reduced the abundance and taxon richness of emerging zooplankton (except 2 mg L -1 of Bratt ® ). This effect was more pronounced in rotifers. In comparison, there were no negative effects on the emergence of microcrustaceans. These findings suggest that commercial products Bratt ® , Roundup ® and their mixture can suppress the emergence of rotifers, thereby influencing zooplankton recruitment potential in lakes impacted by the presence of these commercial herbicides. Our results stress the importance of the need for additional studies to assess the effects of pesticides on dormant egg banks. Copyright © 2018 Elsevier Ltd. All rights reserved.

  19. Amino acid composition reveals functional diversity of zooplankton in tropical lakes related to geography, taxonomy and productivity.

    PubMed

    Aranguren-Riaño, Nelson J; Guisande, Cástor; Shurin, Jonathan B; Jones, Natalie T; Barreiro, Aldo; Duque, Santiago R

    2018-07-01

    Variation in resource use among species determines their potential for competition and co-existence, as well as their impact on ecosystem processes. Planktonic crustaceans consume a range of micro-organisms that vary among habitats and species, but these differences in resource consumption are difficult to characterize due to the small size of the organisms. Consumers acquire amino acids from their diet, and the composition of tissues reflects both the use of different resources and their assimilation in proteins. We examined the amino acid composition of common crustacean zooplankton from 14 tropical lakes in Colombia in three regions (the Amazon floodplain, the eastern range of the Andes, and the Caribbean coast). Amino acid composition varied significantly among taxonomic groups and the three regions. Functional richness in amino acid space was greatest in the Amazon, the most productive region, and tended to be positively related to lake trophic status, suggesting the niche breadth of the community could increase with ecosystem productivity. Functional evenness increased with lake trophic status, indicating that species were more regularly distributed within community-wide niche space in more productive lakes. These results show that zooplankton resource use in tropical lakes varies with both habitat and taxonomy, and that lake productivity may affect community functional diversity and the distribution of species within niche space.

  20. Strong influence of regional species pools on continent-wide structuring of local communities.

    PubMed

    Lessard, Jean-Philippe; Borregaard, Michael K; Fordyce, James A; Rahbek, Carsten; Weiser, Michael D; Dunn, Robert R; Sanders, Nathan J

    2012-01-22

    There is a long tradition in ecology of evaluating the relative contribution of the regional species pool and local interactions on the structure of local communities. Similarly, a growing number of studies assess the phylogenetic structure of communities, relative to that in the regional species pool, to examine the interplay between broad-scale evolutionary and fine-scale ecological processes. Finally, a renewed interest in the influence of species source pools on communities has shown that the definition of the source pool influences interpretations of patterns of community structure. We use a continent-wide dataset of local ant communities and implement ecologically explicit source pool definitions to examine the relative importance of regional species pools and local interactions for shaping community structure. Then we assess which factors underlie systematic variation in the structure of communities along climatic gradients. We find that the average phylogenetic relatedness of species in ant communities decreases from tropical to temperate regions, but the strength of this relationship depends on the level of ecological realism in the definition of source pools. We conclude that the evolution of climatic niches influences the phylogenetic structure of regional source pools and that the influence of regional source pools on local community structure is strong.

  1. Material properties of zooplankton and nekton from the California current

    NASA Astrophysics Data System (ADS)

    Becker, Kaylyn

    This study measured the material properties of zooplankton, Pacific hake (Merluccius productus), Humboldt squid (Dosidicus gigas), and two species of myctophids (Symbolophorus californiensis and Diaphus theta) collected from the California Current ecosystem. The density contrast (g) was measured for euphausiids, decapods (Sergestes similis), amphipods (Primno macropa, Phronima sp., and Hyperiid spp.), siphonophore bracts, chaetognaths, larval fish, crab megalopae, larval squid, and medusae. Morphometric data (length, width, and height) were collected for these taxa. Density contrasts varied within and between zooplankton taxa. The mean and standard deviation for euphausiid density contrast were 1.059 +/- 0.009. Relationships between zooplankton density contrast and morphometric measurements, geographic location, and environmental conditions were investigated. Site had a significant effect on euphausiid density contrast. Density contrasts of euphausiids collected in the same geographic area approximately 4-10 days apart were significantly higher (p < 0.001). Sound speed contrast (h) was measured for euphausiids and pelagic decapods (S. similis) and it varied between taxa. The mean and standard deviation for euphausiid sound speed were 1.019 +/- 0.009. Euphausiid mass was calculated from density measurements and volume, and a relationship between euphausiid mass and length was produced. We determined that euphausiid from volumes could be accurately estimated two dimensional measurements of animal body shape, and that biomass (or biovolume) could be accurately calculated from digital photographs of animals. Density contrast (g) was measured for zooplankton, pieces of hake flesh, myctophid flesh, and of the following Humboldt squid body parts: mantle, arms, tentacle, braincase, eyes, pen, and beak. The density contrasts varied within and between fish taxa, as well as among squid body parts. Effects of animal length and environmental conditions on nekton density

  2. Organizational Structures to Support Oakland Community Schools. Knowledge Brief

    ERIC Educational Resources Information Center

    John W. Gardner Center for Youth and Their Communities, 2015

    2015-01-01

    This brief is part of a series that shares findings from a research collaboration between the John W. Gardner Center for Youth and Their Communities at Stanford University and Oakland Unified School District (OUSD) focused on understanding implementation of the community school model in the district. This brief highlights findings related to…

  3. Unusual bacterioplankton community structure in ultra-oligotrophic Crater Lake

    Urbach, Ena; Vergin, Kevin L.; Morse, Ariel

    2001-01-01

    The bacterioplankton assemblage in Crater Lake, Oregon (U.S.A.), is different from communities found in other oxygenated lakes, as demonstrated by four small subunit ribosomal ribonucleic acid (SSU rRNA) gene clone libraries and oligonucleotide probe hybridization to RNA from lake water. Populations in the euphotic zone of this deep (589 m), oligotrophic caldera lake are dominated by two phylogenetic clusters of currently uncultivated bacteria: CL120-10, a newly identified cluster in the verrucomicrobiales, and ACK4 actinomycetes, known as a minor constituent of bacterioplankton in other lakes. Deep-water populations at 300 and 500 m are dominated by a different pair of uncultivated taxa: CL500-11, a novel cluster in the green nonsulfur bacteria, and group I marine crenarchaeota. b-Proteobacteria, dominant in most other freshwater environments, are relatively rare in Crater Lake (<=16% of nonchloroplast bacterial rRNA at all depths). Other taxa identified in Crater Lake libraries include a newly identified candidate bacterial division, ABY1, and a newly identified subcluster, CL0-1, within candidate division OP10. Probe analyses confirmed vertical stratification of several microbial groups, similar to patterns observed in open-ocean systems. Additional similarities between Crater Lake and ocean microbial populations include aphotic zone dominance of group I marine crenarchaeota and green nonsulfur bacteria. Comparison of Crater Lake to other lakes studied by rRNA methods suggests that selective factors structuring Crater Lake bacterioplankton populations may include low concentrations of available trace metals and dissolved organic matter, chemistry of infiltrating hydrothermal waters, and irradiation by high levels of ultraviolet light.

  4. Macrozooplankton community structure off East Antarctica (80 150°E) during the Austral summer of 1995/1996

    NASA Astrophysics Data System (ADS)

    Hosie, G. W.; Schultz, M. B.; Kitchener, J. A.; Cochran, T. G.; Richards, K.

    2000-08-01

    Zooplankton data from routine 0-200 m oblique trawls and targeted trawls were analysed using cluster analysis and non-metric multidimensional scaling to define the communities in Eastern Antarctica (80-150°E), their distribution patterns, indicator species, and species affinities. Three communities were defined based on routine trawls. The Main Oceanic Community comprising herbivorous copepods, chaetognaths, and the euphausiid Thysanoessa macrura dominated the area west of 120°E. The area east of 120°E was dominated by Salpa thompsoni. The third community located in the neritic zone was dominated by Euphausia crystallorophias. Antarctic krill Euphausia superba did not form a distinct community in its own right, unlike previous observations in Prydz Bay. Krill were distributed throughout most of the survey area but generally in higher abundances towards the shelf break. Overall, krill abundance was low compared with previous net surveys in Prydz Bay. Three main types of assemblages were identified based on target trawls. The first group was dominated by krill (mean 1149 individuals per 1000 m 3) which represented >99% of Group 1 catches in terms of numbers and biomass. Group 2 comprised the bulk of target trawls and comprised a wide diversity of species typical of the main oceanic community, with a mean abundance approximately half of that observed in the routine trawls. The third group comprised trawls in the neritic zone dominated by E. crystallorophias. No salp-dominated aggregation was found. While E. superba did not dominate a distinct community geographically as seen in previous Prydz Bay surveys, it did dominate discrete layers or aggregations, showing that both horizontal and vertical separation of communities exist.

  5. STRUCTURED POPULATION MODELS OF HERBIVEROUS ZOOPLANKTON. (R823588)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  6. Structure in Community College Career-Technical Programs: A Qualitative Analysis. CCRC Working Paper No. 50

    ERIC Educational Resources Information Center

    Van Noy, Michelle; Weiss, Madeline Joy; Jenkins, Davis; Barnett, Elisabeth A.; Wachen, John

    2012-01-01

    Using data obtained from interviews and program websites at Washington community and technical colleges, the authors of this study examine the structure of community college career-technical programs in allied health, business and marketing, computer and information studies, and mechanics and repair. A framework for structure with four…

  7. Paradoxes of Social Networking in a Structured Web 2.0 Language Learning Community

    ERIC Educational Resources Information Center

    Loiseau, Mathieu; Zourou, Katerina

    2012-01-01

    This paper critically inquires into social networking as a set of mechanisms and associated practices developed in a structured Web 2.0 language learning community. This type of community can be roughly described as learning spaces featuring (more or less) structured language learning resources displaying at least some notions of language learning…

  8. The Effect of Riparian Zones in Structuring Small Mammal Communities in the Southern Appalachians

    Joshua Laerm; Michael A. Menzel; Dorothy J. Wolf; James R. Welch

    1997-01-01

    Riparian zones have been shown to be important in structuring vertebrate communities and in maintaining biodiversity. We examined the role of riparian zones in structuring small mammal communities in a southern Appalachian watershed at Coweeta Hydrological Laboratory, Macon County, North Carolina. We established pitfall and live-trap grids in three replicates each of...

  9. Soils associated to different tree communities do not elicit predictable responses in lake bacterial community structure and function.

    PubMed

    Ruiz-González, Clara; Archambault, Esther; Laforest-Lapointe, Isabelle; Del Giorgio, Paul A; Kembel, Steven W; Messier, Christian; Nock, Charles A; Beisner, Beatrix E

    2018-06-14

    Freshwater bacterioplankton communities are influenced by the inputs of material and bacteria from the surrounding landscape, yet few studies have investigated how different terrestrial inputs affect bacterioplankton. We examined whether the addition of soils collected under various tree species combinations differentially influences lake bacterial communities. Lake water was incubated for 6 days following addition of five different soils. We assessed the taxonomic composition (16S rRNA gene sequencing) and metabolic activity (Biolog Ecoplates) of lake bacteria with and without soil addition, and compared these to initial soil communities. Soil bacterial assemblages showed a strong influence of tree composition, but such community differences were not reflected in the structure of lake communities that developed during the experiment. Bacterial taxa showing the largest abundance increases during incubation were initially present in both lake water and across most soils, and were related to Cytophagales, Burkholderiales and Rhizobiales. No clear metabolic profiles based on inoculum source were found, yet soil-amended communities used 60% more substrate than non-inoculated communities. Overall, we show that terrestrial inputs influence aquatic communities by stimulating the growth and activity of certain ubiquitous taxa distributed across the terrestrial-aquatic continuum, yet different forest soils did not cause predictable changes in lake bacterioplankton assemblages.

  10. The community structure and seasonal dynamics of plankton in Bange Lake, northern Tibet, China

    NASA Astrophysics Data System (ADS)

    Zhao, Wen; Zhao, Yuanyi; Wang, Qiaohan; Zheng, Mianping; Wei, Jie; Wang, Shan

    2016-11-01

    The seasonal variations in biomass, abundance, and species composition of plankton in relation to hydrography were studied in the saline Bange Lake, northern Tibet, China. Sampling was carried out between one to three times per month from May 2001 to July 2002. Salinity ranged from 14 to 146. The air and water temperature exhibited a clear seasonal pattern, and mean annual temperatures were approximately 4.8°C and 7.3°C, respectively. The lowest water temperature occurred in winter from December to March at -2°C and the highest in June and July at 17.7°C. Forty-one phytoplankton taxa, 21 zooplankton, and 5 benthic or facultative zooplankton were identified. The predominant phytoplankton species were Gloeothece linearis, Oscillatoria tenuis, Gloeocapsa punctata, Ctenocladus circinnatus, Dunaliella salina, and Spirulina major. The predominant zooplankton species included Holophrya actra, Brachionus plicatilis, Daphniopsis tibetana, Cletocamptus dertersi, and Arctodiaptomus salinus. The mean annual total phytoplankton density and biomass for the entire lake were 4.52×107 cells/L and 1.60 mg/L, respectively. The annual mean zooplankton abundance was 52, 162, 322, and 57, 144 ind./L, in the three sublakes. The annual mean total zooplankton biomass in Lakes 1-3 was 1.23, 9.98, and 2.13 mg/L, respectively. The annual mean tychoplankton abundances in Bg1, 2, and 3 were 47, 67, and 654 ind./L. The annual mean tychoplankton biomass was 2.36, 0.16, and 2.03 mg/L, respectively. The zooplankton biomass (including tychoplankton) in the lake was 9.11 mg/L. The total number of plankton species in the salt lake was significantly negatively correlated with salinity.

  11. Curating and sharing structures and spectra for the environmental community

    EPA Science Inventory

    The increasing popularity of high mass accuracy non-target mass spectrometry methods has yielded extensive identification efforts based on spectral and chemical compound databases in the environmental community and beyond. Increasingly, new methods are relying on open data resour...

  12. Seasonal cross-shelf distribution of major zooplankton taxa on the northern Gulf of Alaska shelf relative to water mass properties, species depth preferences and vertical migration behavior

    NASA Astrophysics Data System (ADS)

    Coyle, Kenneth O.; Pinchuk, Alexei I.

    2005-01-01

    The cross-shelf distribution of major zooplankton species was examined on the northern Gulf of Alaska (GOA) shelf during the production season for four years, between October 1997 and October 2001. The zooplankton community on the northern GOA shelf consisted of oceanic and neritic species of the North Pacific subarctic species complex. Cross-shelf distribution of the major zooplankton species was influenced by their depth preferences, vertical migration behavior, salinity-temperature preferences, and by cross-shelf water-mass distribution and movement. The neritic community, dominated by Pseudocalanus spp., Metridia pacifica and Calanus marshallae, had highest abundances on the inner shelf, in the Alaska Coastal Current, and in the adjacent fjords in late spring and early summer. The oceanic community, which contained primarily Neocalanus cristatus and Eucalanus bungii, was observed in the Alaskan Stream and adjacent waters near the shelf break. A mid-shelf transition zone contained a mixture of oceanic and neritic species. Prince William Sound (PWS) contained a unique species complex of large mesopelagic copepods, amphipods and shrimp. Neocalanus flemingeri and Oithona similis were abundant in all four regions during spring and early summer. The transition zone commonly crossed much of the shelf between the shelf break and the ACC, but satellite images and CTD data indicate that occasionally a narrow shelf-break front can form, in which case distinct zooplankton species groups are observed on either side of the front. Satellite data also revealed numerous large and small eddies, which probably contribute to cross-shelf mixing in the transition zone.

  13. Carbon and nitrogen stable isotope ratios of pelagic zooplankton elucidate ecohydrographic features in the oligotrophic Red Sea

    NASA Astrophysics Data System (ADS)

    Kürten, Benjamin; Al-Aidaroos, Ali M.; Kürten, Saskia; El-Sherbiny, Mohsen M.; Devassy, Reny P.; Struck, Ulrich; Zarokanellos, Nikolaos; Jones, Burton H.; Hansen, Thomas; Bruss, Gerd; Sommer, Ulrich

    2016-01-01

    Although zooplankton occupy key roles in aquatic biogeochemical cycles, little is known about the pelagic food web and trophodynamics of zooplankton in the Red Sea. Natural abundance stable isotope analysis (SIA) of carbon (δ13C) and N (δ15N) is one approach to elucidating pelagic food web structures and diet assimilation. Integrating the combined effects of ecological processes and hydrography, ecohydrographic features often translate into geographic patterns in δ13C and δ15N values at the base of food webs. This is due, for example, to divergent 15N abundances in source end-members (deep water sources: high δ15N, diazotrophs: low δ15N). Such patterns in the spatial distributions of stable isotope values were coined isoscapes. Empirical data of atmospheric, oceanographic, and biological processes, which drive the ecohydrographic gradients of the oligotrophic Red Sea, are under-explored and some rather anticipated than proven. Specifically, five processes underpin Red Sea gradients: (a) monsoon-related intrusions of nutrient-rich Indian Ocean water; (b) basin scale thermohaline circulation; (c) mesoscale eddy activity that causes up-welling of deep water nutrients into the upper layer; (d) the biological fixation of atmospheric nitrogen (N2) by diazotrophs; and (e) the deposition of dust and aerosol-derived N. This study assessed relationships between environmental samples (nutrients, chlorophyll a), oceanographic data (temperature, salinity, current velocity [ADCP]), particulate organic matter (POM), and net-phytoplankton, with the δ13C and δ15N values of zooplankton collected in spring 2012 from 16°28‧ to 26°57‧N along the central axis of the Red Sea. The δ15N of bulk POM and most zooplankton taxa increased from North (Duba) to South (Farasan). The potential contribution of deep water nutrient-fueled phytoplankton, POM, and diazotrophs varied among sites. Estimates suggested higher diazotroph contributions in the North, a greater contribution of

  14. The Organization and Structure of Community Education Offerings in Community Colleges

    ERIC Educational Resources Information Center

    Miller, Michael; Grover, Kenda S.; Kacirek, Kit

    2014-01-01

    One of the key services community colleges provide is community education, meaning those programs and activities that are often offered for leisure or self-improvement and not for credit. Programs of this nature are increasingly challenged to be self-financing, whether through user fees or externally funded grants. The current study explored 75…

  15. Strong Spatial Influence on Colonization Rates in a Pioneer Zooplankton Metacommunity

    PubMed Central

    Frisch, Dagmar; Cottenie, Karl; Badosa, Anna; Green, Andy J.

    2012-01-01

    The magnitude of community-wide dispersal is central to metacommunity models, yet dispersal is notoriously difficult to quantify in passive and cryptic dispersers such as many freshwater invertebrates. By overcoming the problem of quantifying dispersal rates, colonization rates into new habitats can provide a useful estimate of the magnitude of effective dispersal. Here we study the influence of spatial and local processes on colonization rates into new ponds that indicate differential dispersal limitation of major zooplankton taxa, with important implications for metacommunity dynamics. We identify regional and local factors that affect zooplankton colonization rates and spatial patterns in a large-scale experimental system. Our study differs from others in the unique setup of the experimental pond area by which we were able to test spatial and environmental variables at a large spatial scale. We quantified colonization rates separately for the Copepoda, Cladocera and Rotifera from samples collected over a period of 21 months in 48 newly constructed temporary ponds of 0.18–2.95 ha distributed in a restored wetland area of 2,700 ha in Doñana National Park, Southern Spain. Species richness upon initial sampling of new ponds was about one third of that in reference ponds, although the rate of detection of new species from thereon were not significantly different, probably owing to high turnover in the dynamic, temporary reference ponds. Environmental heterogeneity had no detectable effect on colonization rates in new ponds. In contrast, connectivity, space (based on latitude and longitude) and surface area were key determinants of colonization rates for copepods and cladocerans. This suggests dispersal limitation in cladocerans and copepods, but not in rotifers, possibly due to differences in propagule size and abundance. PMID:22792241

  16. Strong spatial influence on colonization rates in a pioneer zooplankton metacommunity.

    PubMed

    Frisch, Dagmar; Cottenie, Karl; Badosa, Anna; Green, Andy J

    2012-01-01

    The magnitude of community-wide dispersal is central to metacommunity models, yet dispersal is notoriously difficult to quantify in passive and cryptic dispersers such as many freshwater invertebrates. By overcoming the problem of quantifying dispersal rates, colonization rates into new habitats can provide a useful estimate of the magnitude of effective dispersal. Here we study the influence of spatial and local processes on colonization rates into new ponds that indicate differential dispersal limitation of major zooplankton taxa, with important implications for metacommunity dynamics. We identify regional and local factors that affect zooplankton colonization rates and spatial patterns in a large-scale experimental system. Our study differs from others in the unique setup of the experimental pond area by which we were able to test spatial and environmental variables at a large spatial scale. We quantified colonization rates separately for the Copepoda, Cladocera and Rotifera from samples collected over a period of 21 months in 48 newly constructed temporary ponds of 0.18-2.95 ha distributed in a restored wetland area of 2,700 ha in Doñana National Park, Southern Spain. Species richness upon initial sampling of new ponds was about one third of that in reference ponds, although the rate of detection of new species from thereon were not significantly different, probably owing to high turnover in the dynamic, temporary reference ponds. Environmental heterogeneity had no detectable effect on colonization rates in new ponds. In contrast, connectivity, space (based on latitude and longitude) and surface area were key determinants of colonization rates for copepods and cladocerans. This suggests dispersal limitation in cladocerans and copepods, but not in rotifers, possibly due to differences in propagule size and abundance.

  17. Resources alter the structure and increase stochasticity in bromeliad microfauna communities.

    PubMed

    Petermann, Jana S; Kratina, Pavel; Marino, Nicholas A C; MacDonald, A Andrew M; Srivastava, Diane S

    2015-01-01

    Although stochastic and deterministic processes have been found to jointly shape structure of natural communities, the relative importance of both forces may vary across different environmental conditions and across levels of biological organization. We tested the effects of abiotic environmental conditions, altered trophic interactions and dispersal limitation on the structure of aquatic microfauna communities in Costa Rican tank bromeliads. Our approach combined natural gradients in environmental conditions with experimental manipulations of bottom-up interactions (resources), top-down interactions (predators) and dispersal at two spatial scales in the field. We found that resource addition strongly increased the abundance and reduced the richness of microfauna communities. Community composition shifted in a predictable way towards assemblages dominated by flagellates and ciliates but with lower abundance and richness of algae and amoebae. While all functional groups responded strongly and predictably to resource addition, similarity among communities at the species level decreased, suggesting a role of stochasticity in species-level assembly processes. Dispersal limitation did not affect the communities. Since our design excluded potential priority effects we can attribute the differences in community similarity to increased demographic stochasticity of resource-enriched communities related to erratic changes in population sizes of some species. In contrast to resources, predators and environmental conditions had negligible effects on community structure. Our results demonstrate that bromeliad microfauna communities are strongly controlled by bottom-up forces. They further suggest that the relative importance of stochasticity may change with productivity and with the organizational level at which communities are examined.

  18. Resources Alter the Structure and Increase Stochasticity in Bromeliad Microfauna Communities

    PubMed Central

    Petermann, Jana S.; Kratina, Pavel; Marino, Nicholas A. C.; MacDonald, A. Andrew M.; Srivastava, Diane S.

    2015-01-01

    Although stochastic and deterministic processes have been found to jointly shape structure of natural communities, the relative importance of both forces may vary across different environmental conditions and across levels of biological organization. We tested the effects of abiotic environmental conditions, altered trophic interactions and dispersal limitation on the structure of aquatic microfauna communities in Costa Rican tank bromeliads. Our approach combined natural gradients in environmental conditions with experimental manipulations of bottom-up interactions (resources), top-down interactions (predators) and dispersal at two spatial scales in the field. We found that resource addition strongly increased the abundance and reduced the richness of microfauna communities. Community composition shifted in a predictable way towards assemblages dominated by flagellates and ciliates but with lower abundance and richness of algae and amoebae. While all functional groups responded strongly and predictably to resource addition, similarity among communities at the species level decreased, suggesting a role of stochasticity in species-level assembly processes. Dispersal limitation did not affect the communities. Since our design excluded potential priority effects we can attribute the differences in community similarity to increased demographic stochasticity of resource-enriched communities related to erratic changes in population sizes of some species. In contrast to resources, predators and environmental conditions had negligible effects on community structure. Our results demonstrate that bromeliad microfauna communities are strongly controlled by bottom-up forces. They further suggest that the relative importance of stochasticity may change with productivity and with the organizational level at which communities are examined. PMID:25775464

  19. Light Structures Phototroph, Bacterial and Fungal Communities at the Soil Surface

    PubMed Central

    Davies, Lawrence O.; Schäfer, Hendrik; Marshall, Samantha; Bramke, Irene; Oliver, Robin G.; Bending, Gary D.

    2013-01-01

    The upper few millimeters of soil harbour photosynthetic microbial communities that are structurally distinct from those of underlying bulk soil due to the presence of light. Previous studies in arid zones have demonstrated functional importance of these communities in reducing soil erosion, and enhancing carbon and nitrogen fixation. Despite being widely distributed, comparative understanding of the biodiversity of the soil surface and underlying soil is lacking, particularly in temperate zones. We investigated the establishment of soil surface communities on pasture soil in microcosms exposed to light or dark conditions, focusing on changes in phototroph, bacterial and fungal communities at the soil surface (0–3 mm) and bulk soil (3–12 mm) using ribosomal marker gene analyses. Microbial community structure changed with time and structurally similar phototrophic communities were found at the soil surface and in bulk soil in the light exposed microcosms suggesting that light can influence phototroph community structure even in the underlying bulk soil. 454 pyrosequencing showed a significant selection for diazotrophic cyanobacteria such as Nostoc punctiforme and Anabaena spp., in addition to the green alga Scenedesmus obliquus. The soil surface also harboured distinct heterotrophic bacterial and fungal communities in the presence of light, in particular, the selection for the phylum Firmicutes. However, these light driven changes in bacterial community structure did not extend to the underlying soil suggesting a discrete zone of influence, analogous to the rhizosphere. PMID:23894406

  20. Locating Structural Centers: A Density-Based Clustering Method for Community Detection

    PubMed Central

    Liu, Gongshen; Li, Jianhua; Nees, Jan P.

    2017-01-01

    Uncovering underlying community structures in complex networks has received considerable attention because of its importance in understanding structural attributes and group characteristics of networks. The algorithmic identification of such structures is a significant challenge. Local expanding methods have proven to be efficient and effective in community detection, but most methods are sensitive to initial seeds and built-in parameters. In this paper, we present a local expansion method by density-based cluste