Phytoplankton assemblages in lakes of the arid Patagonia with relevance for biodiversity conservation

PORCEL, SOL; O´FARRELL, INÉS; SAAD, JUAN; IZAGUIRRE, IRINA

Natal

Workshop; 18th Workshop of the International Association of Phytoplankton; 2017

Varias Instituciones Organizadoras, entre ellas CONICET

Phytoplankton assemblages in lakes of the arid Patagonia with relevance for biodiversity conservationSol Porcel, Inés O´Farrell, Juan F. Saad, Irina IzaguirreFifteen lakes located in the basaltic Buenos Aires plateau (Southern Patagonia) were sampled during the warm seasons since 2015. Some of the water bodies are located in a recent National Park (Patagonia), which was principally created to protect some threatened waterbird species, such as the hooded grebe (Podiceps gallardoi). The lakes of this plateau differ in their morphometry, trophic status and transparency; some of them are inorganic turbid with high amount of suspended material (Kd 6.25 - 28.11 m-1), but most are clear and profusely vegetated (Kd 0.48 - 1.51 m-1). Those lakes located at higher altitudes (> 1200 m.a.s.l.) are vegetated and more suitable for waterbird nesting, being particularly important for biodiversity conservation; in these lakes we found a high phytoplankton diversity, including some endemic desmid species new for the science. Total phytoplankton density was about 500 ind.ml-1 in the most oligotrophic lakes, and achieved around 50,000 ind.ml-1 in two vegetated lakes. The biggest lake of the National Park (El Sello), located at the highest altitude among the studied water bodies, is the most important in relation to waterbird conservation; in this lake phytoplankton never exceeded 28,000 ind.ml-1 and the dominant functional groups were Y, X2 and X1. The highest phytoplankton densities were registered in Chapu and Cevecero lakes, where the most important coda were X2, X1, F and J. The last years a drastic water level decrease was observed in most lakes of the region due to a decline in precipitation, which lead to the complete dry of some water bodies; this was accompanied by a change in phytoplankton assemblages, with an increase of cyanobacteria (S1, Sn), and diatoms belonging to MP. Our studies are showing that the reduction in the hydrometric level generates structural changes in the lakes, with declining of macrophytes and modifying their plankton communities.