Littoral assemblage and lake morphology determines the δ13C signal of pelagic food web in shallow eutrophic lakes

GONZÁLEZ SAGRARIO M. A.; RODRÍGUEZ GOLPE, D.; LA SALA, L.; SÁNCHEZ VUICHARD, G.; PANARELLO, H.

Mar del Plata

Workshop; Workshop between Runbo Network and the Universities and Research Centers of the province of Quebec; 2014

Universidad Nacional de Mar del Plata

The relevance of the trophic linkage between the littoral and pelagic food webs mediated by the type of littoral vegetation in shallow eutrophic lakes was studied performing carbon and nitrogen isotopic analyses and conventional fish gut analyses.  Carbon and nitrogen stable isotopes were determined in fish, macroinvertebrates, zooplankton, seston, periphyton, macrophytes and in dissolved inorganic carbon in three shallow temperate lakes (Pampa plain, Argentina). The δ13C signals of seston differed among lakes, representing the planktonic or the phytoplankton plus littoral detritus signal. Macroinvertebrates exhibited a more enriched carbon signature in the lake codominated by emergent and submerged vegetation than in lakes dominated by emergent vegetation. Fish carbon signatures were intermediate between littoral- and pelagic-carbon signatures in all the lakes, and more than the 80% of the carbon that sustain adult fish is channelled from littoral resources. These results demonstrate that sources of littoral carbon (macrophytes and periphyton) sustain both, the littoral and the pelagic food webs in these shallow temperate lakes. In fact, the δ13C-seston was related to the type of macrophyte dominant in each system and also to lake size. In conclusion, littoral primary producer signal scaled up to fish, resulting in a coupling of the pelagic and littoral compartments.