Dynamics of phytoplankton in the coastal waters at Vladivostok in 2019–2021

Structure and abundance of phytoplankton community in the Sportivnaya Harbour and Paris Bay in Vladivostok (western coast of the Japan Sea) was monitored from October 2019 to December 2021. In total, 130 and 144 phytoplankton taxa were identified in these two areas, respectively. The overall cell abundance ranged from 1.3 · 103 to 19 · 106 cells/L (on average 21 · 104 and 84.5 · 104 cells/L); the total phytoplankton biomass — from 3.0 mg/m 3 to 38.5 g/m 3 (on average 0.8 and 2.6 g/m 3 , respectively, by areas). The long-term observations were made for the first time in the Sportivnaya Harbour. The community composition was typical of eutrophic waters, with usual seasonal succession in the Paris Bay but frequent blooms in the Sportivnaya Harbour, when diatoms were replaced by flagellates and filamentous cyanobacteria. Such dynamics is presumably caused by anthropogenic eutrophication due to uncontrolled wastewater discharge.