Ecosystem differences in the trophic enrichment of 13C in aquatic food webs

1997 ◽  
Vol 54 (6) ◽  
pp. 1255-1258 ◽  
Author(s):  
R L France ◽  
R H Peters
Keyword(s):  
Food Webs ◽  
Trophic Position ◽  
Open Ocean ◽  
Food Sources ◽  
Regression Equations ◽  
Combining Data ◽  
Trophic Enrichment ◽  
Aquatic Food ◽  
Alternative Food Sources ◽  
Estuarine Coastal

Data from 35 published studies were collated to examine patterns in the trophic enrichment of 13C of consumers. Because both delta 13C and delta 14N vary systematically across ecosystems, it was necessary to standardize for such differences before combining data from numerous sources. Relationships of these measures of ecosystem-standardized delta 13C to ecosystem-standardized trophic position ( DELTA delta 15N) for freshwater, estuarine, coastal, and open-ocean and for all aquatic ecosystems yielded regression equations of low predictive capability (average of 20% explained variance in delta 13C). However, differences were observed in the slopes between delta 13C and standardized trophic position when data were examined study-specifically: the average trophic fractionation of 13C was found to increase from + 0.2omicron for freshwater to + 0.5omicron for estuarine to + 0.8omicron for coastal, and to + 1.1omicron for open-ocean food webs. This ecosystem-specific gradient in 13C enrichment for consumers supports previous findings of a similar continuum existing for zooplankton - particulate organic matter differences in delta 13C. Possible mechanisms to explain these ecosystem-specific patterns in 13C enrichment may be related to the relative importance of detritus, heterotrophic respiration, partial reliance on alternative food sources, and lipid influences in the different ecosystems.

scholarly journals Eutrophication induces shifts in the trophic position of invertebrates in aquatic food webs

Ecology ◽  
2020 ◽  
Author(s):  
Gea H. Lee ◽  
J. Arie Vonk ◽  
Ralf C.M. Verdonschot ◽  
Michiel H.S. Kraak ◽  
Piet F.M. Verdonschot ◽  
...  
Keyword(s):  
Food Webs ◽  
Trophic Position ◽  
Aquatic Food Webs ◽  
Aquatic Food

scholarly journals On the Use of Stable Hydrogen Isotope Measurements (δ2H) to Discern Trophic Level in Avian Terrestrial Food Webs

Diversity ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 202
Author(s):  
Rien E. van Wijk ◽  
Yahkat Barshep ◽  
Keith A. Hobson
Keyword(s):  
Food Webs ◽  
Hydrogen Isotope ◽  
Trophic Position ◽  
Terrestrial Ecosystems ◽  
Forest Site ◽  
Trophic Enrichment ◽  
Terrestrial Environments ◽  
Closed Canopy ◽  
Stable Hydrogen Isotope ◽  
Δ15n And Δ13c

The measurement of stable hydrogen isotope ratios (δ2H) in animal tissues is a popular means of inferring spatial origins and migratory connections. However, the use of this isotope to infer diet and potentially trophic position remains poorly understood, especially in non-aquatic terrestrial ecosystems. In many animal communities, tissue δ15N values are strongly associated with trophic position. Correlations between tissue δ2H and δ15N are expected, then, if δ2H is affected by trophic enrichment of 2H. In addition, within sites, we would expect higher tissue δ2H values in insectivorous species compared to granivores or nectarivores. We tested these hypotheses for two resident avian communities in Nigeria consisting of 30 species representing a range of dietary guilds (granivores, frugivores, nectarivores, omnivores, insectivores) by comparing feather δ2H, δ15N and δ13C values. We found considerable isotopic overlap among all guilds except granivores, with no clear pattern of enrichment in 2H with trophic position. However, at one of our sites (open scrubland), feather δ2H was positively correlated with feather δ15N (R2 = 0.30) compared to a closed canopy forest site (R2 = 0.09). Our results indicate weak evidence for predictable trophic enrichment in 2H in terrestrial environments and indicate that controlled studies are now required to definitively elucidate the behavior of H isotopes in terrestrial food webs.

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.

Comparative dietary ecology of turtles (Chelodina burrungandjii and Emydura victoriae) across the Kimberley Plateau, Western Australia, prior to the arrival of cane toads

2016 ◽  
Vol 67 (11) ◽  
pp. 1611 ◽  
Author(s):  
N. N. FitzSimmons ◽  
P. Featherston ◽  
A. D. Tucker
Keyword(s):  
Land Use ◽  
Food Webs ◽  
Western Australia ◽  
Prey Availability ◽  
Food Sources ◽  
Dietary Ecology ◽  
Aquatic Food ◽  
Land Use Practices ◽  
Prey Items ◽  
Specific Food

Food webs in north-western Australian rivers exist in dynamic environments and will be influenced by land use practices, invasion of toxic cane toads (Rhinella marina) and the effects of climate change on river flows. Baseline studies are needed to understand aquatic food webs before these impacts. In the present study, we investigated the diets of two turtles (Emydura victoriae and Chelodina burrungandjii) in four upland rivers across a gradient of rainfall and land uses in the Kimberley Plateau of Western Australia. We captured turtles by snorkelling and recovered their prey by stomach lavage. We enumerated 2720 prey items from 390 E. victoriae samples and 308 prey items from 155 C. burrungandjii samples. Prey compositions distinguished E. victoriae as an omnivorous generalist relying on a diversity of animal and plant prey and C. burrungandjii as a piscivorous specialist, but with both species as likely predators of toxic cane toad eggs or tadpoles. Comparisons among the rivers showed variation in diets for both species that reflect differences in prey availability and location-specific food webs. Terrestrially based food sources were observed in 26% of E. victoriae samples and 3% of C. burrungandjii samples, which indicates the importance of the aquatic–terrestrial interface and land use practices within these rivers.

Carbon sources for aquatic food webs of riverine and lacustrine tropical waterholes with variable groundwater influence

2017 ◽  
Vol 68 (3) ◽  
pp. 442 ◽  
Author(s):  
N. E. Pettit ◽  
D. M. Warfe ◽  
P. G. Close ◽  
B. J. Pusey ◽  
R. Dobbs ◽  
...  
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Isotope Analysis ◽  
Carbon Sources ◽  
Freshwater Wetlands ◽  
Food Sources ◽  
Web Studies ◽  
Aquatic Food Webs ◽  
Aquatic Food ◽  
Groundwater Reserves

Food web studies integrate ecological information and provide understanding of ecosystem function. Aquatic ecosystems of the Kimberley region (north-western Australia) have high conservation significance as hotspots for maintaining local and regional biodiversity. This study investigated the influence of waterhole type and persistence on the strength of consumer reliance on local energy resources for aquatic food webs. Changes in water isotopic composition indicated groundwater inputs were enough to overcome evaporative losses in some waterholes. Other waterholes had varying levels of isotope enrichment suggesting insufficient groundwater input to ‘compensate’ for evaporative loss. C and N isotope analysis indicated considerable overlap among energy sources in waterholes between macrophytes and periphyton but gradient analysis indicated that periphyton is a major carbon source for aquatic consumers. Groundwater-fed waterholes appeared to have higher quality food sources (indicated by lower C:N ratios), but there was minimal evidence that direct groundwater contributions were related to food web processes. Nonetheless, in a region where groundwater is influential in maintaining aquatic habitats, future development of groundwater reserves will likely affect the ecological and cultural value of freshwater wetlands by either reducing their permanence or size or indirectly through possible alteration to the role of periphyton in supporting the food web.

scholarly journals Unlocking the power of fatty acids as dietary tracers and metabolic signals in fishes and aquatic invertebrates

2020 ◽  
Vol 375 (1804) ◽  
pp. 20190639 ◽  
Author(s):  
Timothy D. Jardine ◽  
Aaron W. E. Galloway ◽  
Martin J. Kainz
Keyword(s):  
Fatty Acids ◽  
Food Webs ◽  
Muscle Tissue ◽  
Dietary Fatty Acids ◽  
Regression Equations ◽  
Biochemical Modification ◽  
Selective Retention ◽  
Aquatic Food ◽  
Transformation Of Organic Matter ◽  
High Degree

Determining the transfer and transformation of organic matter in food webs is a fundamental challenge that has implications for sustainable management of ecosystems. Fatty acids (FA) offer a potential approach for resolving complex diet mixtures of organisms because they provide a suite of molecular tracers. Yet, uncertainties in the degree of their biochemical modification by consumers, due to selective retention or metabolism, have limited their application. Here, we consolidated 316 controlled feeding studies of aquatic ectotherms (fishes and invertebrates) involving 1404 species–diet combinations to assess the degree of trophic modification of FA in muscle tissue. We found a high degree of variability within and among taxa in the %FA in consumer muscle tissue versus %FA in diet regression equations. Most saturated FA had weak relationships with the diet ( r 2 < 0.30) and shallow slopes ( m < 0.30), suggesting a lack of retention in muscle when fed in increasing amounts. Contrarily, several essential FA, including linoleic (18:2n-6) and α-linolenic acid (18:3n-3), exhibited significant relationships with the diet ( m > 0.35, r 2 > 0.50), suggesting supply limitations and selective retention in muscle by consumers. For all FA, relationships strengthened with increasing taxonomic specificity. We also demonstrated the utility of new correction equations by calculating the potential contributions of approximately 20 prey items to the diet of selected species of generalist fishes using a FA mixing model. Our analyses further reveal how a broad range of fishes and invertebrates convert or store these compounds in muscle tissue to meet physiological needs and point to their power in resolving complex diets in aquatic food webs. This article is part of the theme issue ‘The next horizons for lipids as ‘trophic biomarkers’: evidence and significance of consumer modification of dietary fatty acids’.

scholarly journals Elevated temperature and browning increase dietary methylmercury, but decrease essential fatty acids at the base of lake food webs

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Pianpian Wu ◽  
Martin J. Kainz ◽  
Fernando Valdés ◽  
Siwen Zheng ◽  
Katharina Winter ◽  
...  
Keyword(s):  
Climate Change ◽  
Fatty Acids ◽  
Organic Matter ◽  
Food Webs ◽  
Essential Fatty Acids ◽  
Trophic Levels ◽  
Climate Change Scenarios ◽  
Essential Nutrients ◽  
Aquatic Food Webs ◽  
Aquatic Food

AbstractClimate change scenarios predict increases in temperature and organic matter supply from land to water, which affect trophic transfer of nutrients and contaminants in aquatic food webs. How essential nutrients, such as polyunsaturated fatty acids (PUFA), and potentially toxic contaminants, such as methylmercury (MeHg), at the base of aquatic food webs will be affected under climate change scenarios, remains unclear. The objective of this outdoor mesocosm study was to examine how increased water temperature and terrestrially-derived dissolved organic matter supply (tDOM; i.e., lake browning), and the interaction of both, will influence MeHg and PUFA in organisms at the base of food webs (i.e. seston; the most edible plankton size for zooplankton) in subalpine lake ecosystems. The interaction of higher temperature and tDOM increased the burden of MeHg in seston (< 40 μm) and larger sized plankton (microplankton; 40–200 μm), while the MeHg content per unit biomass remained stable. However, PUFA decreased in seston, but increased in microplankton, consisting mainly of filamentous algae, which are less readily bioavailable to zooplankton. We revealed elevated dietary exposure to MeHg, yet decreased supply of dietary PUFA to aquatic consumers with increasing temperature and tDOM supply. This experimental study provides evidence that the overall food quality at the base of aquatic food webs deteriorates during ongoing climate change scenarios by increasing the supply of toxic MeHg and lowering the dietary access to essential nutrients of consumers at higher trophic levels.

scholarly journals Assessing the utility of sulfur isotope values for understanding mercury concentrations in water and biota from high Arctic lakes

2019 ◽  
Vol 5 (2) ◽  
pp. 90-106 ◽  
Author(s):  
Gretchen L. Lescord ◽  
Meredith G. Clayden ◽  
Karen A. Kidd ◽  
Jane L. Kirk ◽  
Xiaowa Wang ◽  
...  
Keyword(s):  
Food Webs ◽  
Total Mercury ◽  
Nitrogen Isotopes ◽  
Sulfur Isotopes ◽  
High Arctic ◽  
Arctic Lakes ◽  
Carbon And Nitrogen ◽  
Resolute Bay ◽  
Aquatic Food ◽  
Globally Stable

Methylmercury (MeHg) biomagnifies through aquatic food webs resulting in elevated concentrations in fish globally. Stable carbon and nitrogen isotopes are frequently used to determine dietary sources of MeHg and to model its biomagnification. However, given the strong links between MeHg and sulfur cycling, we investigated whether sulfur isotopes (δ34S) would improve our understanding of MeHg concentrations ([MeHg]) in Arctic lacustrine food webs. Delta34S values and total mercury (THg) or MeHg were measured in water, sediments, and biota from six lakes near Resolute Bay, NU, Canada. In two lakes impacted by historical eutrophication, aqueous sulfate δ34S was ∼8‰ more positive than sedimentary δ34S, suggestive of bacterial sulfate reduction in the sediment. In addition, aqueous δ34S showed a significant positive relationship with aqueous [MeHg] across lakes. Within taxa across lakes, [THg] in Arctic char muscle and [MeHg] in their main prey, chironomids, were positively related to their δ34S values across lakes, but inconsistent relationships were found across entire food webs among lakes. Across lakes, nitrogen isotopes were better predictors of biotic [THg] and [MeHg] than δ34S within this dataset. Our results suggest some linkages between Hg and S biogeochemistry in high Arctic lakes, which is an important consideration given anticipated climate-mediated changes in nutrient cycling.

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