BACTERIOPLANKTON STRUCTURE OF FISHLESS AND FISH STOCKED LAKES FROM THE PATAGONIAN STROBEL PLATEAU (ARGENTINA)

SCHIAFFINO, ROMINA; SABIO GARCÍA, CARMEN; SAAD, JUAN FRANCISCO; IZAGUIRRE, IRINA

Honolulu-Hawaii

Congreso; Aquatic Science Meeting 2017; 2017

ASSOCIATION FOR THE SCIENCES OF LIMNOLOGY & OCEANOGRAPHY

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 has a high conservation value, because their lakes provide the primary habitat for the critically endangered Hooded Grebe (Podiceps gallardoi). We surveyed 12 shallow lakes of the region, including fishless (FL) and fish stocked (F) environments, in order to analyze and compare their main limnological features and the structure of bacterioplankton communities. Our results showed that F shallow lakes presented significantly higher dominant bacterioplankton richness than FL shallow lakes (t-test = 3.8, p = 0.004), whereas total abundances of bacterioplankton did not change (t-test = 0.7, p = 0.521). Both type of shallow lakes shared 50.9% of the OTUs, while F lakes showed 17.5% of exclusive OTUs and FL lakes 31.6%. The result of the non-metric MDS showed 2 groups, one integrated by F lakes and the other by FL lakes, being the bacterioplankton composition significantly different between both (ANOSIM R = 0.46, p = 0.0036). The Redundancy Analysis showed that environmental and geographical variables explained 45.4% of the variance and FL shallow lakes ordinated together with higher values of pH,temperature and latitude, and separately from the F shallow lakes. The dominant taxa found were related to the freshwater groups Alphaproteobacteria, Betaproteobacteria, Bacteroidetes and Actinobacteria. Particularly, some of the dominant taxa found were related to the Flavobacteriales and Cytophagales orders of Bacteroidetes. Therefore, bacterioplankton richness and composition is affected by the presence of fish, probably related to a trophic cascade effect.