Depth-specific patterns in benthic–planktonic food web relationships in Lake Superior

2006 ◽  
Vol 63 (7) ◽  
pp. 1496-1503 ◽  
Author(s):  
Michael E Sierszen ◽  
Gregory S Peterson ◽  
Jill V Scharold
Keyword(s):  
Great Lakes ◽  
Food Web ◽  
Food Webs ◽  
Water Column ◽  
Trophic Position ◽  
Lake Superior ◽  
Benthic Algae ◽  
Isotope Ratios ◽  
Food Sources ◽  
Large Lakes

In an investigation of the spatial characteristics of Laurentian Great Lakes food webs, we examined the trophic relationship between benthic amphipods (Diporeia) and plankton in Lake Superior. We analyzed the carbon and nitrogen stable isotope ratios of Diporeia and plankton at stations in water column depths of 4–300 m. Neither δ15N nor δ13C of plankton from the upper 50 m of the water column varied significantly with station depth. Diporeia isotope ratios exhibited depth-specific patterns reflecting changes in food sources and food web relationships with plankton. Diporeia was 13C enriched at station depths of <40 m, reflecting increased dietary importance of benthic algae. There was a systematic increase in Diporeia δ15N with depth, which appeared to result from a combination of dietary shifts in the nearshore and decompositional changes in Diporeia's principal food, sedimented plankton, in deep habitats. Diporeia δ13C and δ15N together described changes in food web isotope baseline with depth. They also discriminated three depth strata representing photic, mid-depth, and profundal zones. These findings have implications for our understanding of Great Lakes food webs and analyses of trophic position within them, the ecology of zoobenthos and plankton communities, and sampling designs for large lakes.

Long-term food web change in Lake Superior

2009 ◽  
Vol 66 (12) ◽  
pp. 2118-2129 ◽  
Author(s):  
Stephanie N. Schmidt ◽  
M. Jake Vander Zanden ◽  
James F. Kitchell
Keyword(s):  
Stable Isotope ◽  
Great Lakes ◽  
Food Web ◽  
Stable Isotope Analysis ◽  
Native Species ◽  
Trophic Position ◽  
Lake Superior ◽  
Isotope Analysis ◽  
Food Web Structure

Restoration and rehabilitation of native species in the Laurentian Great Lakes is a priority for fisheries management agencies. Restoration efforts are increasingly incorporating a perspective that considers species within a broader food web context. We used stable isotope analysis and museum-preserved specimens to describe and quantify 100 years of food web changes in the Lake Superior fish community. We validated stable isotope analysis of museum specimens by showing a positive correlation between isotope- and diet-based estimates of trophic position. While introductions have created a more trophically diverse food web than historically found in Lake Superior, two separate metrics revealed little community-wide change in the food web. Our species-specific analysis revealed trophic niche differences between shortjaw ( Coregonus zenithicus ) and shortnose ( Coregonus reighardi ) ciscoes, two species previously argued to be indistinguishable based on morphological characteristics. By providing a historical context, our findings show the ability of the Lake Superior food web to accommodate non-native species introductions over the last century while still supporting native species populations. This long-term information about food web structure can help guide management and restoration goals in Lake Superior. Furthermore, Lake Superior can serve as a basis for comparing food web changes in other, more highly altered Great Lakes.

Depth gradients in food-web processes linking habitats in large lakes: Lake Superior as an exemplar ecosystem

2014 ◽  
Vol 59 (10) ◽  
pp. 2122-2136 ◽  
Author(s):  
Michael E. Sierszen ◽  
Thomas R. Hrabik ◽  
Jason D. Stockwell ◽  
Anne M. Cotter ◽  
Joel C. Hoffman ◽  
...  
Keyword(s):  
Food Web ◽  
Lake Superior ◽  
Large Lakes ◽  
Depth Gradients

Functional plasticity of benthic macroinvertebrates: implications for trophic dynamics in acid streams

2002 ◽  
Vol 59 (9) ◽  
pp. 1563-1573 ◽  
Author(s):  
Olivier Dangles
Keyword(s):  
Food Web ◽  
Benthic Macroinvertebrates ◽  
Trophic Position ◽  
Benthic Algae ◽  
Functional Plasticity ◽  
Vosges Mountains ◽  
Acid Streams ◽  
Diet Analyses ◽  
One Year ◽  
Species Specific

Functional plasticity of benthic macroinvertebrates was investigated over one year in four acid streams in the Vosges Mountains (northeastern France). The trophic position of macroinvertebrate species within the benthic food web was determined using gut content analyses. Diet analyses revealed that only 24–36% of biomass of putative shredders consumed leaf fragments, whereas up to 44% consumed benthic algae and bryophytes. Although most Nemouromorpha stoneflies were generalist consumers, several other taxa (e.g., Brachyptera seticornis, Chaetopterygopsis maclachlani) specialised on benthic algae and bryophytes. Our study showed that acid streams unexpectedly had very few specialised leaf-shredding species (e.g., Chaetopteryx villosa) that could explain the slow leaf detritus processing rates observed in these systems. Primary producers appear to be an alternative resource for shredders, playing an important role in supporting food webs in forested acid streams. The food web built in this study suggests that overlooking species-specific functional plasticity of invertebrates may result in a misconception of invertebrate community structure in acid streams.

Fish on the roof of the world: densities, habitats and trophic position of stone loaches (Triplophysa) in Tibetan streams

2017 ◽  
Vol 68 (1) ◽  
pp. 53 ◽  
Author(s):  
Dean Jacobsen ◽  
Søren Kock Laursen ◽  
Ladislav Hamerlik ◽  
Karen Moltesen ◽  
Anders Michelsen ◽  
...  
Keyword(s):  
Trophic Position ◽  
Stomach Contents ◽  
Benthic Algae ◽  
Stomach Content Analysis ◽  
Food Sources ◽  
Fish Length ◽  
The Tibetan Plateau ◽  
Running Waters ◽  
Ecological Data ◽  
Percentage Cover

The fast increase in temperature on the Tibetan Plateau, with anticipated future changes in aquatic ecosystems and biodiversity, highlights the urgent need for ecological data on the sparsely studied Tibetan running waters. In the present study we surveyed eight Tibetan streams to obtain data on densities, feeding selectivity and trophic position of the stone loach Triplophysa. Benthic algae, detritus, macroinvertebrates and fish were quantified and collected for stable isotope and stomach content analysis. Triplophysa density (mean 0.70 individuals m–2, maximum 1.6 individuals m–2) decreased with altitude and increased with the percentage cover of fine substratum. Glacier-fed sites tended to have the lowest fish densities, whereas the highest densities were found near lakes. Mean fish length (4.1–9.6cm) was positively related to the percentage cover of coarse substratum. Triplophysa was omnivorous, but the composition of the stomach contents varied greatly between sites and among individuals. Algal matter was ingested at most sites, but macroinvertebrates (Chironomidae, Baetidae and Simuliidae) dominated the ingestion (average 50–100%). The trophic position of Triplophysa, identified from δ15N (‰) of the biota, varied between 2.6 and 4.2 among localities (mean 3.6) and was inversely related to the biomass of benthic algae, but unrelated to quantities of other potential food sources.

Biology and Management of Dogfish Sharks

2009 ◽  
Keyword(s):  
Stable Isotope ◽  
Pacific Ocean ◽  
Food Webs ◽  
Trophic Position ◽  
Nitrogen Isotope ◽  
Isotope Ratios ◽  
Gulf Of Alaska ◽  
The North ◽  
Northeastern Pacific ◽  
The Mean

Abstract.—Spiny dogfish <em>Squalus acanthias </em>biomass has increased in the Gulf of Alaska, yet little is known about the ecological niche that dogfish fill in this ecosystem. Trophic position is an important indicator of the ecological role of an organism. To explore the trophic position of dogfish we analyzed the nitrogen and carbon stable isotope ratios of 60 dogfish from five locations between Washington and the Gulf of Alaska. The mean δ<sup>15</sup>N values for dogfish ranged from 12.0‰ (central Gulf of Alaska) to 13.4‰ (Howe Sound, British Columbia) and the mean δ<sup>13</sup>C values ranged from –21.3‰ (Yakutat Bay, Alaska) to –17.9‰ (Puget Sound, Washington). Sites to the north tended to be significantly depleted in the heavy isotopes of both nitrogen and carbon. The differences in nitrogen isotope ratios among sites were attributed to potential changes in dogfish feeding behavior and trophic position. Differences in carbon isotope ratios suggested that dogfish utilize different food webs along the northeastern Pacific Ocean shelf. Additionally it was hypothesized that feeding differentially in offshore versus inshore food webs or targeting pelagic versus benthic prey species may explain the isotopic variability. These results are preliminary and require additional tests before conclusions can be made about the trophic position of dogfish in this region. Future work will explore stable isotope variability at lower trophic levels to test the hypothesis that entire food webs are isotopically shifted owing to differences in isotopic fractionation at the base of the food web. Also, trophic level differences among dogfish size classes and between sexes will be explored among a greater diversity of locations to better describe the ecological consequences of increased biomass of dogfish in the northeastern Pacific Ocean.

scholarly journals Aquatic food webs in mangrove and seagrass habitats of Centla Wetland, a Biosphere Reserve in Southeastern Mexico

2010 ◽  
Vol 8 (1) ◽  
pp. 171-178 ◽  
Author(s):  
Manuel Mendoza-Carranza ◽  
David J Hoeinghaus ◽  
Alexandre M Garcia ◽  
Ángel Romero-Rodriguez
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Native Species ◽  
Human Impacts ◽  
Biosphere Reserve ◽  
Isotope Ratios ◽  
Future Research ◽  
Carbon And Nitrogen ◽  
Aquatic Food Webs ◽  
Aquatic Food

Mangrove and seagrass habitats are important components of tropical coastal zones worldwide, and are conspicuous habitats of Centla Wetland Biosphere Reserve (CWBR) in Tabasco, Mexico. In this study, we examine food webs in mangrove- and seagrass-dominated habitats of CWBR using stable isotope ratios of carbon and nitrogen. Our objective was to identify the importance of carbon derived from mangroves and seagrasses to secondary production of aquatic consumers in this poorly studied conservation area. Carbon and nitrogen isotope ratios of basal sources and aquatic consumers indicated that the species-rich food webs of both habitats are dependent on riparian production sources. The abundant Red mangrove Rhizophora mangle appears to be a primary source of carbon for the mangrove creek food web. Even though dense seagrass beds were ubiquitous, most consumers in the lagoon food web appeared to rely on carbon derived from riparian vegetation (e.g. Phragmites australis). The introduced Amazon sailfin catfish Pterygoplichthys pardalis had isotope signatures overlapping with native species (including high-value fisheries species), suggesting potential competition for resources. Future research should examine the role played by terrestrial insects in linking riparian and aquatic food webs, and impacts of the expanding P. pardalis population on ecosystem function and fisheries in CWBR. Our findings can be used as a baseline to reinforce the conservation and management of this important reserve in the face of diverse external and internal human impacts.

scholarly journals Loss of functionally unique species may gradually undermine ecosystems

2010 ◽  
Vol 278 (1713) ◽  
pp. 1886-1893 ◽  
Author(s):  
Eoin J. O'Gorman ◽  
Jon M. Yearsley ◽  
Tasman P. Crowe ◽  
Mark C. Emmerson ◽  
Ute Jacob ◽  
...  
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Ecosystem Functioning ◽  
Trophic Position ◽  
Interaction Strength ◽  
Natural Systems ◽  
Interacting Species ◽  
Weakly Interacting ◽  
Taxonomic Groups ◽  
Unique Species

Functionally unique species contribute to the functional diversity of natural systems, often enhancing ecosystem functioning. An abundance of weakly interacting species increases stability in natural systems, suggesting that loss of weakly linked species may reduce stability. Any link between the functional uniqueness of a species and the strength of its interactions in a food web could therefore have simultaneous effects on ecosystem functioning and stability. Here, we analyse patterns in 213 real food webs and show that highly unique species consistently tend to have the weakest mean interaction strength per unit biomass in the system. This relationship is not a simple consequence of the interdependence of both measures on body size and appears to be driven by the empirical pattern of size structuring in aquatic systems and the trophic position of each species in the web. Food web resolution also has an important effect, with aggregation of species into higher taxonomic groups producing a much weaker relationship. Food webs with fewer unique and less weakly interacting species also show significantly greater variability in their levels of primary production. Thus, the loss of highly unique, weakly interacting species may eventually lead to dramatic state changes and unpredictable levels of ecosystem functioning.

Trophic positions and predator–prey mass ratio of the pelagic food web in the East China Sea and Sea of Japan

2016 ◽  
Vol 67 (11) ◽  
pp. 1692 ◽  
Author(s):  
Seiji Ohshimo ◽  
Hiroshige Tanaka ◽  
Koh Nishiuchi ◽  
Tohya Yasuda
Keyword(s):  
Food Web ◽  
Food Webs ◽  
East China Sea ◽  
Sea Of Japan ◽  
Trophic Position ◽  
Mass Ratio ◽  
The East China Sea ◽  
Predator Prey ◽  
Prey Mass ◽  
Scaled Models

Size-based food webs analysis is essential for understanding food web structure and evaluating the effects of human exploitation on food webs. We estimated the predator–prey mass ratio (PPMR) of the pelagic food web in the East China Sea and Sea of Japan by using the relationships between body mass and trophic position. Trophic position was calculated by additive and scaled models based on nitrogen stable isotope ratios (δ15N). The PPMRs based on additive and scaled models were 5032 (95% confidence interval (CI) 2066–15506) and 3430 (95% CI 1463–10083) respectively. The comparatively high PPMRs could reflect low ecosystem transfer efficiency and high metabolic rate.

A stable isotope evaluation of the structure and spatial heterogeneity of a Lake Superior food web

2000 ◽  
Vol 57 (7) ◽  
pp. 1395-1403 ◽  
Author(s):  
Chris J Harvey ◽  
James F Kitchell
Keyword(s):  
Stable Isotope ◽  
Spatial Heterogeneity ◽  
Food Web ◽  
Lake Trout ◽  
Trophic Position ◽  
Lake Superior ◽  
Salvelinus Namaycush ◽  
Trophic Relationships ◽  
Rainbow Smelt ◽  
Western Lake

We used stable isotope analysis to derive trophic relationships and movement patterns for components of the western Lake Superior food web. Trophic linkages implied by previous gut content studies were only marginally supported by stable isotope data. Siscowet lake trout (Salvelinus namaycush siscowet) were the top predators, and trophic overlap between siscowet and lean lake trout (Salvelinus namaycush) was low. Exotic Pacific salmon (Oncorhynchus spp.) occupied a lower trophic position than native piscivores because the latter relied more on coregonids. To evaluate spatial heterogeneity of the food web, we assumed that the adjacent cities of Duluth and Superior (DS) were a point source of 15N, and we measured isotopes of organisms close to and far from DS. Slimy sculpin (Cottus cognatus) were enriched in the DS area relative to other sites, implying that they are relatively sedentary. Rainbow smelt (Osmerus mordax) showed no differences at any sites, implying high vagility. Other organisms showed differences that could not be attributed to DS, implying that other mechanisms, such as trophic ontogeny, were influencing their isotopic signatures.

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