The Long-Term Dynamics and Morphology of the Diatom Thalassiosira nordenskioeldii Cleve, 1873 (Bacillariophyta) from the Coastal Waters of Peter the Great Bay, Sea of Japan

Abstract

Long-term study of the species composition and numbers of phytoplankton in the coastal waters of Peter the Great Bay, the Sea of Japan, revealed the seasonal and year-to-year dynamics in the abundance of the diatom Thalassiosira nordenskioeldii Cleve, 1873. The species dominated the phytoplankton in the winter and early spring, growing under the sea ice at a surface water temperature of –1.8 to 0°С and a salinity of 33.0–35.0‰. The observations of the long-term population dynamics of T. nordenskioeldii (2005–2015) showed a decline in its significance in the phytoplankton community compared to that in the 1970s, resulting in a complete loss of dominance in winter–spring plankton assemblages. The year-round occurrence of T. nordenskioeldii cells in the studied area, as well as data from the literature, indicate that the species has a tropical–arctic–boreal distribution. Positive correlations were found between the surface water salinity, the content of organic matter in seawater, and the abundance of T. nordenskioeldii. A negative relationship with nitrate concentration reflected a depletion of nitrates caused by the mass growth of T. nordenskioeldii.