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

IZAGUIRRE, IRINA; SAAD, JUAN FRANCISCO; SCHIAFFINO, ROMINA; UNREIN, FERNANDO; LANCELOTTI, JULIO LUCIO

Granada

Congreso; ASLO (Association for the Sciences of Limnology and Oceanography) Aquatic Science Meeting; 2015

Association for the Sciences of Limnology and Oceanography

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