The First Record of Thalassiosira angulata (Bacillariophyceae) Bloom in the White Sea: Spatial Distribution and Associated Species

Species composition and biomass of phytoplankton (Bsum), concentration of chlorophyll “a” and nutrients, and hydrophysical conditions were studied on July 5–12, 2011, at 29 stations in the White Sea. The chlorophyll “a” concentration and Bsum in the surface water layer corresponded to the level of phytoplankton bloom (>1 mg/m3 and >30 mg C/m3, respectively), except for two stations. For the first time, the dominance of diatom Thalassiosira angulata by biomass was recorded for a vast area of the White Sea; in the surface layer, the abundance and biomass of this species reached up to 24 × 103 cells/L and 34.56 mg C/m3, respectively. Even higher values (179 × 103 cells/L and 258 mg C/m3) were noted at one of the coastal stations at a 3-m depth. The stability of the water column (positive relation) and salinity (negative relation) were the main factors affecting the spatial variability of the T. angulata biomass.