In 2002–2008, seasonal (April–November) monitoring of the phytoplankton in the Russian part of the Curonian Lagoon at five fixed sites was performed. A total of 91 Cyanobacteria, 100 Bacillariophyta,...

The trophic relationships of the phytoplankton and zooplankton in the Vistula Lagoon in 2008–2010 were investigated. In the current period, the lagoon is an eutrophic water body with summer blooms of blue-green algae. The trophic level of the Vistula Lagoon influences both the composition and quantitative characteristics of the communities of phytoplankton and zooplankton and the trophic relationships between them. In the analyzed period, the consumption of phytoplankton by the zooplankton on the average in the growing season was 28%, which is 1.5 times higher than in the late 1970s. The high grazing pressure of the zooplankton on the phytoplankton reduces its biomass, production, and the intensity of the blooming by the blue-green algae in the Vistula Lagoon.

The seasonal dynamics of phyto- and zooplankton, as well as their trophic interactions, were studied for the shallow freshwater hypereutrophic Curonian Lagoon in the Baltic Sea in 2007–2009. The...

The seasonal dynamics of production processes in the Baltic Sea are poorly studied. The aim of our research was to study the seasonal features of primary productivity (including the balance with bacterial production) and its redistribution in plankton in the southeastern part of the Baltic Sea in different seasons. More than 70% of primary production is formed in the 0–10 m layer (74–97% of the PP in the euphotic layer). In the same layer, PP accounted for almost 100% of the sum of primary and bacterial production in April and October, and almost 60% in June. Photosynthetic efficiency (PP/rETR) increased in June and October, demonstrating an increase in phytoplankton utilization of absorbed light energy. The depth-integrated values of PP, Chl a, bacterial, and phytoplankton biomasses were maximal in October. The maximum values of zooplankton biomass were determined in June, and they were significantly (5–14 times) higher than in other seasons. The maximum values of bacterial production were also in June.

The results of studies of phytoplankton production, biomass, and species composition conducted in Kursiu Marius Lagoon in 2001, 2002 are presented. A significant effect of blue-green alga blooming on the trophic status and processes in the coastal part of Kursiu Marius Lagoon is revealed. It is shown that the mass development of algae in combination with setup phenomena can cause alga accumulation in the coastal zone, oxygen deficiency, and fish kills.

The structure and dynamics of plankton communities in the coastal zone of the Curonian Lagoon of the Baltic Sea from January to December 2017–2021 has been studied. It was found that, at the coastal shallow littoral station surrounded by macrophytes, the species diversity was higher and the quantitative characteristics of phytoplankton and zooplankton were lower in all seasons and years of the study than at the deeper coastal station located behind the macrophyte belt. The exception was the period when, as a result of surge events, the phytoplankton biomass in the coastal littoral in October–November 2018 increased to 326–627 g/m³. Every year, Cyanobacteria “blooms” with different intensities and durations were observed at the Lagoon. The abundance of cells of potentially toxic Сyanobacteria exceeded the World Health Organization standard, as a rule, in summer months at a deepwater coastal station, especially in 2017–2018. This had a negative impact on the state of the entire ecosystem, primarily on zooplankton organisms, in which communities the proportion of dead individuals increased. Water during the period of Cyanobacterial blooms in summer and autumn 2017–2018 also had an acute toxic effect on planktonic test organisms.