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

SAAD, JUAN F.; SCHIAFFINO, MARÍA R; IZAGUIRRE, IRINA; SABIO Y GARCÍA, CARMEN A

Honolulu

Congreso; ASLO 2017 Aquatic science meeting; 2017

American Society of Limnology and 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 gallardol). We surveyed 12 shallow lakes of the region, including fishless (FL) and fish stocked (F) environments, in arder to analyze and compare their main limnological features and the structure of bacterioplankton communities. Our results showed that F shallow lakes presented significantly higher total and dominant bacterioplankton richness than FL shallow lakes (t-test = 2.3 and 3.8, both p < 0.05), whereas total abundances of bacterioplankton did not change (t-test = 0.7, p = 0.521). Both type of shallow lakes shared 45.4% of the OTUs, while F lakes showed 25.6% of exclusive OTUs and FL lakes 29.0%. The result of the non-metric MDS showed 2 groups, one integrated by F lakes and the other by FL, being the bacterioplankton composition significantly different between both (ANOSIM R = 0.46, p = 0.003). Redundancy Analysis showed that environmental variables explained 50% of the variance and FL shallow lakes ordinated together with higher values of pH, conductivity and nutrient, and separately from the F shallow lakes. The dominant taxa found were related to the freshwater groups Bacteroidetes, Betaproteobacteria,and Verrucomicrobia. Therefore, bacterioplankton richness and composition were affected by the presence of fish, probably related to a trophic cascade effect.