A retrospective overview of zooplankton research in Uruguay

With 6 main basins, and being the second smallest country in South America, Uruguay has a high freshwater ecosystem diversity. The study of zooplankton communities dates back to 1949, but remained marginal until the end of the 20th century when the number of publications increased notably. Here, we revise the history and accumulated knowledge on the zooplankton community in Uruguayan continental ecosystems, highlighting the main approaches and milestones. So far, ca. 100 academic papers with 219 authors have been published in international, regional, and local journals, accumulating more than 2150 citations. Most of the published studies come from shallow lakes, followed by reservoirs and estuaries, and were concentrated in the southern part of Uruguay. Most taxonomic records correspond to the Rio de la Plata basin, followed by the Atlantic Ocean basin, and the Rio Uruguay basin. The number of records in the rest of the country is comparatively low, with minima occurring in the basins of the rivers Negro and Santa Lucia. A total of 170 species belonging to 117 genera have been recorded, mainly for Copepoda, Cladocera and Rotifera. Limnological studies in Uruguay have historically followed an ecosystemic approach, thus, most of the literature referring to zooplankton has such a perspective. The most relevant ecological aspects analyzed so far include trophic interactions, species survival and dispersion, biological invasions, the relationship with eutrophication and climatic variability, and have applied traditional as well as functional and trait-based approaches. Our analysis allowed us to detect important knowledge gaps, that warrant attention for future studies which can help elucidate local and regional processes in freshwater zooplankton in Uruguay.