Microbial food-web components in two hypertrophic human-impacted Pampean shallow lakes: interactive effects of environmental, hydrological, and temporal drivers

Few studies have intensively assessed the dynamic of all planktonic components and their microbial communities in hypertrophic shallow lakes. The aim of this work was to study the potential drivers shaping the microbial food-web components (heterotrophic bacteria and strictly phototrophic microplankton). Thus, we studied the monthly abundances and functional groups of the different planktonic food-web components (heterotrophic bacteria, picocyanobacteria, picoeukaryotes, heterotrophic flagellates, ciliates, phytoplankton, zooplankton) in two interconnected and hypertrophic Pampean shallow lakes (Gomez and Carpincho) during dry-wet periods (27-month study). We hypothesized that temporal (intra and inter-annual) factors exert a major role in shaping the microbial food-web components in both lakes. Both shallow lakes showed similar dynamic in the environmental variables, that followed inter-annual and seasonal variations. In Gomez, the variation of microbial components was mainly explained by a combination of environmental, predation, and temporal factors (38.2%), whereas in Carpincho by pure temporal drivers (31.8%). Microbial and predator components were significantly different between dry and wet periods. The connection and closeness between both lakes seem not to play a major role in the factors driving the microbial component abundances. These lakes are strongly influenced by temporal factors, which regulate not only the microbial components, but also the physical, chemical, and biological variables.