Both lake regime and fish introduction shape autotrophic planktonic communities of lakes from the Patagonian Plateau (Argentina)

Abstract

Strobel Plateau hosts more than 1,500 shallow lakes displaying different water regimes, which constitute the habitat for many species. Although the region is naturally fishless, many of the lakes were stocked with trout, bearing uncertainty about the possible effects on the ecosystem. The main objective of this study was to analyze the characteristics of planktonic autotrophic communities of lakes differing in regime (phytoplankton turbid, clear vegetated, and clear unvegetated) and presence/absence of fish. During late spring and summer, 14 water bodies were sampled in 2011 and 2013 considering different regimes and presence/absence of fish. Besides limnological variables, the autotrophic communities, from pico to microplankton, were also analyzed. Differences in physical and chemical characteristics observed among the lakes corresponded to their current regime and the presence/absence of trouts. Autotrophic picoplankton and phytoplankton > 20 µm abundances differed among lake types being highest in fish-stocked lakes. Although the three type of lakes presented phycoerythrin-rich picocyanobacteria and picoeukaryotes, only fish-stocked lakes hosted phycocyanin-rich picocyanobacteria. Moreover, fish-stocked lakes were dominated by cyanobacteria, while chlorophytes abounded in fishless systems. Evidences that lake regime and fish occurrence influence planktonic autotrophic communities of Strobel plateau is here provided, highlighting the intra- and interannual dynamism of the aquatic systems.