Most rotifer species have positive responses in abundance caused by the increase in nitrogen, phosphorus and chlorophyll-a in reservoirs using TITAN analysis

Some zooplanktonic species change their abundances according to the primary productivity increases in freshwater lentic environments. Here, we aimed to i) evaluate the concentration threshold of variables related to eutrophication (nitrogen, phosphorus
and chlorophyll-a concentrations) that alter the frequency of occurrence and relative abundance of rotifer species, and ii) analyze which Rotifera species are related positively or negatively to the increase in these variables. The rotifer community
structure was studied in fifteen reservoirs in La Plata River Basin, the second largest in South America, relating its abundance with nitrogen, phosphorus and chlorophyll-a values using the Threshold Indicator Rate Analysis (TITAN). Seventy-one rotifer
species were registered in the reservoirs, and six species were considered as indicators of changes in their frequency of occurrence and relative abundance with points of change of 1.118 µg.L -1 , 22.44 µg.L -1 and 3.89 µg.L -1 of the nitrogen, phosphorus and
chlorophyll-a concentrations, respectively. Species with positive responses to the increase in nutrients were Keratella tropica, Plationus patulus, Filinia terminalis and Synchaeta oblonga, and negative responses Conochilus unicornis and Synchaeta stylata,
typical of oligotrophic reservoirs. The only species that presented the same response for all variable concentrations was Keratella tropica, which is a very common species in South America. Our results reinforce the assumption that some rotifer species are good
indicators to the variables related to the trophic level in reservoirs. The script and study data are attached to this database.