Invasion strategies and establishment of Ceratium dinoflagellate in subtropical watersheds of Southern Brazil and its interaction with Microcystis cyanobacteria: I. Hydrographic Region of Uruguay

Abstract

Ceratium furcoides is a dinoflagellate that exhibits invasive behavior in aquatic ecosystems of Southern Brazil. Because of this, the study had as objectives to determine the factors that drive dinoflagellate populations as well as identifying temporal and spatial patterns of these populations, relating to Microcystis and propose actions against the invasion and establishment of Ceratium. Data (physical and chemical water and phytoplankton density) came from the monitoring carried out by CORSAN (Riograndense Sanitation Company), in reservoirs in the Hydrographic Region (HR) of Uruguay, from 2013 to 2019 (weekly to monthly sampling); climatic data were obtained through INMET (National Meteorological Institute). Seasonally, maximum precipitation occurred in autumn and spring, temperatures followed a subtropical pattern. Regarding phytoplankton, maximum density occurred in autumn and summer, in 2018 and 2013 (except Ceratium, with maximum in 2014). The analysis indicated that the highest values of density of phytoplankton, cyanobacteria, and Microcystis occurred in U20 basin, in Erechim (autumn 2018) and Passo Fundo (summer 2013); Ceratium peaks were found at U70 in Dom Pedrito (summer 2014) and U80 in Aceguá (autumn 2015). Usually, the populations of dinoflagellate and Microcystis did tend to stabilization, however showed classic relations, such as competition and coexistence, and dominance of the dinoflagellate. The results suggest that local environmental characteristics (temperature, phosphorus, nitrate, organic matter, pH) are key for the development of C. furcoides in this HR, and as is in an environment susceptible to its invasion, studies like this are important in understanding and eventually combating species with this character.