Spatio-temporal variability of surface phytoplankton community structure in relation to different water systems in the east China sea coast

The East China Sea coast (ECS) is characterised by a diverse range of landform types, which influence the physical characteristics of the local waters. The spatio-temporal phytoplankton community structure, and the salinity, transparency, and temperature gradients were examined across six different waters of the ECS coast during four seasons. In total, 118 taxa were identified, including 86 Bacillariophyta, 16 Pyrrhophyta, and 16 other taxa. Cluster and multidimensional scaling analyses classified the six study areas into inner the estuary, outer the estuary, and in a semi-enclosed bay. Notable variations were observed in the abundance and species distribution patterns of phytoplankton across the three water types during four seasons. Oscillatoria spp. was the dominant species inner the estuary during the spring, summer, and winter cruises. Coscinodiscus spp. and Skeletonema costatum were the dominant species in all study areas; however, as the main dominant species, there were no significant differences in Coscinodiscus spp. abundance at different dimensional scales. In addition, the biodiversity index values showed no statistically significant differences among the three types of water, except during the summer cruise. Spearman's rank correlation and redundancy analyses showed that the distribution of Chlorophyta was primarily influenced by salinity. In contrast, transparency was the primary driver of phytoplankton abundance for most seasons and temperature exerted the most significant effect on phytoplankton abundance during summer. These findings indicate that physical disturbances are significant for the regulation of the phytoplankton community structure along the ECS coast.