Short-term variability in plankton abundance on the inner shelf off Ubatuba, Brazil

Abstract The interaction between biological and short-term physical processes affects plankton distribution and composition variability, with consequences for the entire ecosystem. Aspects of the plankton distribution at smaller scales have been understudied, mainly in coastal regions where highly variable conditions promote variations in the biophysical environment. This work aimed to investigate the short-term variations in the distribution of plankton along the inner shelf off Ubatuba, Brazil. We quantified the abundance and diversity of the main planktonic taxa (>100 μm) and their spatiotemporal distribution in winter 2018 and summer 2019 using high-resolution sensors and a shadowgraphic imaging system at cross-shore and fixed stations (12 and 24 h). Summer–winter environmental contrast was evident in the water column stability and plankton abundance. In the summer, higher values of plankton abundance and diversity were obtained. Our results suggested that spatiotemporal variations related to wind-induced mixing and water mass intrusions lead to variabilities in plankton populations on a time scale of a few hours, vertically between depth layers and at spatial scales ˂2 km. This study contributes to the knowledge of the mechanisms of biophysical interactions and their spatiotemporal variation, which is crucial for assessing the effects of climate variability on plankton-mediated ecosystem services.