The Long-Term Dynamics and Morphology of the Diatom Thalassiosira nordenskioeldii Cleve, 1873 (Bacillariophyta) from the
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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 O. G. Shevchenkoa, b, *, M. A. Shulginaa, V. M. Shulkinc, and K. O. Tevsd aZhirmunsky
National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia b Far Eastern State Technical Fisheries University, Vladivostok, 690087 Russia cPacific Geographical Institute, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia d Far Eastern Federal University, Vladivostok, Russky Isl., Ayaks, 690922 Russia *e-mail: [email protected] Received June 25, 2019; revised October 24, 2019; accepted November 28, 2019
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. Keywords: phytoplankton, diatoms, Bacillariophyta, Thalassiosira nordenskioeldii, morphology, long-term dynamics, ecology DOI: 10.1134/S1063074020040069
INTRODUCTION The genus Thalassiosira was described by Cleve [19] from the Davis Strait, with the identification of the species T. nordenskioeldii. The genus was created based on the type of connection of cells into flexible chains by a mucous thread. The genus comprises more than 300 species and intraspecific taxa, most of which are representatives of marine plankton [25]. Thirtyone taxa of Thalassiosira were identified in the Russian waters of the Sea of Japan. Among them, T. nordenskioeldii was recorded throughout the region; in the northwestern part of the sea, this diatom causes winter and early spring “blooms” in the coastal zone under ice or in open waters [3, 6, 7, 14]. From December to March, the species may form 70–90% of the total phytoplankton abundance. In the world oceans, T. nordenskioeldii is one of the most widespread species of planktonic diatoms in the temperate seas. It causes winter and winter–spring “blooms” in waters of the coastal zone
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