A review of 121 years of studies on the freshwater zooplankton of Brazil

A review was carried out on the freshwater zooplankton in Brazil, between 1900 and 2021, based on 1014 studies, and the main trends were pointed. There was an increase of studies from the 1990 s onwards, especially between 2016 and 2020. Most of them addressed ecological research, followed by taxonomical research in the past (mid-1970 s). Field studies were also more numerous than experimental and review ones, but the latter type also increased between 2016 and 2020. Most studies were developed in limnetic regions and in artificial and natural lakes, in contrast to littoral regions, streams and wetlands. Studies on cladocerans were the most numerous in all environments, followed by Copepoda and Rotifera. Protozooplankton was the least studied group, with a predominance of testate amoebae, followed by ciliates, flagellates and naked amoeba studies. We also discuss some aspects of the ecological traits, such as life cycles and life history, population and community dynamics, interactions with the environment, influence of environmental and anthropogenic factors and interspecific interactions. Studies on populations biomass, secondary production, functional ecology, long term duration and molecular analyzes were the main gaps and the next challenges. Finally, it is also necessary to understand the diversity and related variables in different environments that have few or never been studied.