Sulphur stable isotopes can distinguish trophic dependence on sediments and plankton in boreal lakes (original) (raw)
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Canadian Journal of Fisheries and Aquatic Sciences
Estimating the trophic position of predators in food webs using stable isotopes requires establishing a “baseline”, typically served by bivalves or snails. However, the frequent absence of such organisms in lakes leaves researchers in a difficult situation. Here we test the hypothesis that trophic position (TP) of largemouth bass (LB; Micropterus salmoides) in lakes can be estimated from δ15N of benthic organic material (BOM) in littoral surficial sediment. δ15NLB as a function of δ15NBOM was significant across 51 lakes with an R2 of 0.84, supporting our hypothesis. In a subset of six lakes, the mean TPLB did not differ significantly when calculated using baselines of δ15N in BOM, unionid mussels (UN), gastropods (SN), or from a stable isotope mixing model. In a subset of 26 lakes, mean TPLB calculated from δ15NBOM and δ15NUN baselines were not significantly different, but TPLB calculated using δ15NBOM was not significantly correlated with TPLB calculated using δ15NUN. Although δ15N...
Benthic food web structure in a large shallow lake studied by stable isotope analysis
Freshwater Science, 2014
The benthic foodweb structure of Lake Võrtsjärv, a large (270 km2), shallow, and turbid Estonian lake, was evaluated based on C and N stable-isotope signatures (δ13C, δ15N). Variation in δ13C between sampling sites was not related to site proximity to the littoral zone or the more vegetated southern part of the lake, but rather appeared to be influenced by in-situ site peculiarities. δ13C was stable temporally and between functional feeding groups, a result implying that the whole benthic food web of the lake relies largely on the same C source admixture, essentially particulate organic matter (POM). Thus, the foodweb composition of Lake Võrtsjärv is remarkably homogeneous given the lake’s large surface area. Apparent trophic-level δ15N fractionation between total collectors and total predators (mean 1.7‰) was lower than the value of 3.4‰ generally adopted in foodweb studies, but the higher value was valid for specific prey–predator links. The low δ13C signature of some chironomid samples indicated probable assimilation of methane-oxidizing bacteria (MOB) by these sediment-dwelling invertebrates. However, the lack of similar 13C depletion in benthic filterers (mussels) indicated that the MOB layer is essentially confined to the sediments and does not reach the water column, which probably constrains transfer of methane-derived C through the food web to fish in this lake. Our study demonstrates that the benthic food web of shallow turbid lakes like Võrtsjärv is simplified and is mostly sustained by phytoplanktonic C sources.
Stable carbon isotope biogeochemistry of lakes along a trophic gradient 1 2
2014
Stable carbon isotope biogeochemistry of lakes along a trophic gradient 1 2 Anna de Kluijver 1* , Petra L. Schoon 2 , John A. Downing 3 , Stefan Schouten 2,4 , and Jack J. 3 Middelburg 1,4 4 5 1 Department of Ecosystems Studies, NIOZ Royal Netherlands Institute for Sea Research, 6 Yerseke, the Netherlands 7 2 Department of Marine Organic Biogeochemistry, NIOZ Royal Netherlands Institute for Sea 8 Research, Den Burg, the Netherlands 9 3 Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, 10 Iowa, USA 11 4 Utrecht University, Faculty of Geosciences, Utrecht, the Netherlands 12
Carbon stable isotopes reveal complex trophic interactions in lake plankton
Rapid communications in mass …, 1999
The lower trophic linkages in lake plankton food webs are generally described as relatively simple, even accounting for the additional complexity of potential ‘microbial looping’. Crustacean zooplankton are frequently amalgamated into one trophic functional group as grazers of autotrophic production. The carbon stable isotope ratios for separated zooplankton species, particulate organic matter (POM) and phytoplankton from a number of lakes in Finland and the UK were analysed. These revealed greater complexity in trophic interactions than would otherwise be observed if the zooplankton had been represented by a mixed sample. Grazing zooplankton were usually depleted in 13C relative to the bulk POM on which they might feed, with d13C deviating by up to 17% There were no consistent differences between d13C values for copepods and cladocerans. Predatory cladocerans were generally enriched by greater than 1% compared to their putative prey. We suggest that care in separating the zooplankton species for stable isotope analysis may expose otherwise undetected sources of carbon and facilitate unravelling trophic links further up the food web.
Multiple Stable Isotopes Used to Trace the Flow of Organic Matter in Estuarine Food Webs
Science, 1985
The use of a combination of the stable isotopes of sulfur, carbon, and nitrogen allows the flow of organic matter and trophic relations in salt marshes and estuaries to be traced while eliminating many ambiguities that accompany the use of a single isotopic tracer. Salt-marsh grasses take up the isotopically light sulfides formed during sulfate reduction, and the transfer of this light sulfur through the marsh food web is illustrated with data on the ribbed mussel (Geukensia demissa) from various locations in a New England marsh. The multiple isotope approach shows that this filter feeder consumes both marsh grass ( Spartina) detritus and plankton, with the relative proportions of each determined by the location of the mussels in the marsh.
Temporal variation in the baseline stable carbon isotope (d13C)value of a well-studied, productive lake was examined over a 26-yr period using archived samples of the herbivorous zooplankter Daphnia galeata as a proxy because of its phytoplankton diet. The baseline d13C value was strongly correlated with pH and the concentration of dissolved carbon dioxide in the lake as well as with the d13C value of a predatory zooplankter. An isotopic fractionation model incorporating algal physiology (the growth rate, surface area, and carbon content of the main phytoplankton species) and the dissolved carbon dioxide concentration in the lake was used to predict, successfully, the baseline d13C values of the lake over the study period. In aquatic ecosystems where the concentration of dissolved carbon dioxide is temporally variable, the baseline d13C value can be more clearly defined by taking the concentration of CO2 into account. This approach will allow food web relationships to be quantified more accurately.