The relative yield of variable chlorophyll fluorescence (F _v/F _m), rate of photosynthetic carbon fixation (P), growth rate, and production of extracellular photosynthates (P _ec) was studied in diatom T. weissflogii in seawater with salinity decreasing from 35 to 15 and 5‰. After incubation at 5‰ for 1 day, the diatom abundance (N) decreased as a result of death of a fraction of cells, while viable cells demonstrated decreased F _v/F _m and P, P _ec was detectable, and cell division was likely inhibited. After incubation for 2 days, population started to grow, while exponential growth rate and the abundance by day 8 were lower compared to 35‰. After incubation at 15‰ for 1 day, P was higher and F _v/F _m was lower compared to 35‰. No cell death was observed and exponential growth rate insignificantly differed from that at 5‰. The value of N by day 8 was lower compared to 35‰ but higher compared to 5‰. The dependence of photosynthetic parameters and population dynamics of T. weissflogii on the relative salinity is discussed.

The species composition and biomass of phytoplankton, as well as hydrological characteristics, were estimated during four spatial surveys in the Subarctic tidal Kem’ River estuary and...

In a saline semi-isolated lagoon on Cape Zeleny (White Sea), the annual dynamics of the vertical hydrological structure and the seasonal dynamics of phytoplankton were traced. Species composition, vertical distribution, abundance, nutrition type, and biomass were analyzed. In total, 293 species and supraspecific taxa of algae and cyanobacteria were found. Most of the identified species are marine, and 38 species are freshwater. Taxonomic composition changed in the lagoon throughout the year. Dinoflagellates dominated in winter and early June; unidentified cocci and flagellates in July; diatoms, dinoflagellates, and unidentified cells in August; dinoflagellates in September; and unidentified cocci and flagellates in October–November. The abundance of algae also changed in the lagoon throughout the year. The integrated biomass in the water column varied from 0.01 g C/m² in January to 0.78 g C/m² in early September. According to the environmental parameters, the water column of the lagoon was subdivided into several zones with different environmental conditions and corresponding phytoplankton communities. The similarity between the communities of different horizons was 32–46% in summer and 7% in winter. The chemocline layer was the most populous. It contained a maximum of phytoplankton biomass, 1–2 orders of magnitude higher than that in the overlying horizons. Despite the connection to the sea, the phytoplankton structure in the surface water layer in the lagoon and in the sea differed significantly in composition, quantitative parameters, and seasonal dynamics. The similarity between the communities never exceeded 50%. In terms of biomass dynamics, the lagoon lagged behind the sea until mid-summer, but, starting from August, it outnumbered it, and the phytoplankton development in the lagoon lasted longer, until late autumn. According to sequential tests DistLM, the phytoplankton structure and dynamics in the lagoon and in the sea were related to the daylength, water salinity, oxygen content, and pH by 24.5%. At the same time, the PhP structure did not depend on water temperature, underwater illuminance, or depth. Oxygen content and pH were defined by PhP activity. Salinity serves as a vector of the vertical sequence of ecological niches. The day length seems to be the crucial factor of the seasonal PhP dynamics in the semi-isolated coastal stratified lakes and lagoons.

After a long break since 1994, the dynamics of the structure and abundance of phytoplankton was studied again at different depths in the White Sea in March

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...

Natural or artificial separation of a water body from its parent water area leads to stratification of its water column and the development of a vertical s