Freshwater Biodiversity Research in Brazil: Trends from a Systematic Review and Topic Modeling

Brazil is a megadiverse country that hosts six major biomes and a vast freshwater network. Despite this richness, research on freshwater biodiversity has been heterogeneous across regions, communities, and time, leaving significant knowledge gaps. Previous syntheses have typically focused on individual taxa or specific biomes, providing important but fragmented perspectives that limit cross‐community comparisons. To assess these limitations, we reviewed literature on fungi, phytoplankton, macrophytes, zooplankton, macroinvertebrate, meiofauna, and fish, applying text mining and topic modeling. The earliest studies, dating back to the 1970s, focused on zooplankton. From 2005 onward, research expanded rapidly, with fish and macroinvertebrate emerging as the most studied groups, while fungi remained the least investigated. Topic mapping revealed community‐specific emphases. Fish research often addressed dam impacts; macroinvertebrate research focused on Ephemeroptera, Plecoptera, and Trichoptera (EPT) biotic indices in lotic ecosystems; zooplankton studies highlighted trophic ecology in reservoirs; phytoplankton research emphasized floodplains, cyanobacteria blooms, and abiotic variation; aquatic macrophyte studies explored metacommunities and shallow lakes; meiofauna research centered on Oligochaeta biodiversity; and studies on fungi addressed interactions with macroinvertebrate. The only cross‐community topic was plant‐associated dynamics. We found more rising (“hot”) than declining (“cold”) topics. Hot topics appeared in all groups except phytoplankton and zooplankton. Cold topics included the EPT index (macroinvertebrate) and spatial variation in reservoirs (zooplankton). While most studies addressed fundamental ecology, applied themes such as bioassessment, fisheries, and land‐use change were less common. Experimental approaches were rare. Overall, Brazilian freshwater research has advanced in scope but remains unbalanced. Future efforts should strengthen applied and experimental ecological studies (e.g., through long‐term and large‐scale field experiments and mesocosms), expand knowledge of fungi and meiofauna, and improve taxonomy and functional trait data across freshwater communities, especially in tropical regions.