Invasion of the dinoflagellate Ceratium furcoides (Levander) Langhans 1925 in South America: record of the pattern of expansion and persistence in tropical reservoirs in Northeastern Brazil

Ceratium furcoides is a phytoplankton dinoflagellate that has received attention due to its invasive behavior in freshwater environments in South America. In this study, we monitored 87 tropical reservoirs in Northeastern Brazil between 2014 and 2020, with the objective of detecting and recording the occurrence of this species in these reservoirs, as well as to check its pattern of expansion and persistence. In total, between 2016 and 2020, there were 30 new records of C. furcoides in four of the six basins studied. The highest number of reservoirs with the occurrence of the species were located in the semiarid region, which suggests that it is an area of high susceptibility to invasion. The invaded area gradually increased over the sampled years, reaching 17,750 km2 in 2020 and the highest expansion rate occurred in 2017 (68.86 km year−1) with the longest distance covered in the first year of invasion (between 2016 and 2017, with 96.98 km). However, the species persistence in most environments was relatively low. Among the factors that facilitated the expansion of C. furcoides, we identified the action of an interbasin water transfer project as well as the resumption of rainfall patterns providing greater connectivity between the reservoirs. Further studies are required to understand the population dynamics of this dinoflagellate associated with climatic and limnological conditions. This information is essential for the development of management policies that guarantee ecosystem integrity and the provision of ecosystem services in aquatic systems.