Light availability as a useful paradigm for understanding shallow lake functioning

M. E. LLAMES,L. LAGOMARSINO,N. DIOVISALVI,P. FERMANI,A. M. TORREMORELL,G. PEREZ,BUSTINGORRY,R. ESCARAY,M. FERRARO,H.E. ZAGARESE.

AGU Chapman Conference Lake Tahoe, Incline Village,Nevada, USA

Congreso; Lakes and Reservoirs as Sentinels, Integrators, and Regulators of Climate Change; 2008

AGU & ASLO

Lakes from the Pampa region of Argentina are typically large (> 100 ha) and shallow (~2m). Most of them are presently eutrophic or hypertrophic. The seasonal and interannual variability of these highly turbid lakes is strongly controlled by light availability. The region is presently experiencing increasing trends in precipitation, alteredhydroperiod and steadily increasing agriculture pressure. Thus, we anticipate that a major effect of climate change on Pampean lakes will be related to changes in light availability, mediated by changes in water depth and background turbidity. We performed a mesocosm (3000 L) experiment aimed at investigating the effects of light availability on shallow, turbid systems. Our results are consistent with light-limitationtheory: (i) light attenuation and (ii) primary production increased with light availability. Furthermore, the heterotrophic components provided additional evidence for the paradox of energy enrichment: (iii) herbivore density and (iv) the seston P and N content decreased, while (v) community respiration increased with light availability. Collectively, our results suggest that the anticipated climate changes will affect food web structure, energy fluxes and the carbon cycle of shallow lakes.