Microbial planktonic communities of lakes from the Patagonian Strobel Plateau (Argentina): influence of fish introduction

IZAGUIRRE, I.; SAAD, J.; SCHIAFFINO, M. R.; UNREIN, F.; LANCELOTTI, J.

Granada

Congreso; ASLO Meeting 2015; 2015

The ?Strobel Plateau?, located in the Patagonian steppe (Argentina), holds thousands of natural fishless shallow lakes with contrasting limnological conditions, some of which were stocked with trout. This region is recognized as very important from the point of view of the conservation biology, because their lakes constitute the primary habitat for the critically endangered Hooded Grebe (Podiceps gallardoi). We surveyed different lake types of the region, including fishless and fish stocked environments, analyzing the main limnological features and the structure of the microbial plankton communities. We found that the phytoplankton is affected by the presence of fish, probably due to a trophic cascade effect. Phytoplankton biomass was significantly higher in fish stocked lakes, and the phytoplankton composition showed important differences between lakes with and without fish. Multivariate analyses indicated that variables associated with trophic status were relevant in the differences among lakes. Small colonial cyanobacteria were only abundant in fish stocked lakes. Phytoplankton functional groups also differed among lakes, with higher proportion of nanoplankton and mixotrophic species in fishless ecosystems. Autotrophic picoplankton were also more abundant in lakes with trout.