Lake size, macrophytes, and omnivory contribute to food web linkage in temperate shallow eutrophic lakes
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Physical, chemical and biological processes facilitate cross-habitat connections in lakes, prompting food webs to be supported by different subsidies. We tested the hypothesis that the pelagic food web is subsidized by littoral resources and fish foraging behaviour plays a major role in carbon flux and on food web structure in shallow hypereutrophic lakes. We performed a fish diet and carbon and nitrogen isotope analyses to predict the linkage between littoral and pelagic habitats in three shallow hypereutrophic lakes. Lakes differed in morphology, fetch, macrophyte composition and width of the littoral zone. δ13C signals of seston differed among lakes, but were similar to other producers. Macroinvertebrates and fish carbon signatures were more enriched in the lake co-dominated by emergent and submerged vegetation. Fish foraging behaviour indicates that more than the 80% of the carbon that sustain adult fish was channelled from the littoral. In conclusion, littoral carbon were relevant and sustain, in part, food web in these shallow lakes. Factors like the extension of the littoral zone, lake morphometry, and the dominance of multi-chain omnivorous fish facilitate the connection among lake compartments and the transference of littoral carbon to lake food web.
KeywordsCarbon stable isotope Nitrogen stable isotopes Fish Macroinvertebrates
We thank the two anonymous reviewers for their comments that have improved our manuscript, R. Inger (University of Exeter) for the valuable discussion and help with SIAR, M. Vanni (Miami University) for sharing his original data of fish carbon content, G. Bernava (IIMYC-CONICET/UNMDP) for technical assistance, and E. Ducos (INGEIS-CONICET/UBA) who performed the isotope analysis. We acknowledged the landowners and managers for their permission and assistance to enter to the private lands where the lakes are located, especially to P. Urrutia, H. Sanabria and González Aguilar family. This research was supported by the Agencia de Promoción Científica y Tecnológica (PICT 384), Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET) (PIP 1328, 465), and Universidad Nacional de Mar del Plata (EXA 418-08 y EXA 529-10). M.A.G.S.& H.P. are CONICET researchers.
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