Phytoplankton Seasonal Dynamics under Conditions of Climate Change and Anthropogenic Pollution in the Western Coastal Waters of the Black Sea (Sevastopol Region)

Abstract

The studies of seasonal phytoplankton dynamics, its growth rate, and microzooplankton grazing were conducted on two stations in the western Black Sea coastal waters near Sevastopol from January 2021 to December 2022. The phytoplankton species composition has remained relatively the same during recent years compared to the end of the last century and the beginning of the 2000s. However, significant changes have occurred in the ratio between different species of diatoms, and the proportion of dinoflagellates was increased, especially in the autumn. Large diatoms and dinoflagellates play a crucial role in forming the phytoplankton biomass seasonal peaks. The first central maximum was observed in July, and the second smaller one was in September–November. Whereas two decades ago, the small diatoms generated three peaks annually: in February, May, and September–October. The maximum values of the phytoplankton growth rate and the rate of its consumption by microzooplankton decreased 2–3 times compared to the beginning of the 2000s. The relative share of primary production consumed by microzooplankton annually averages 35%, two times lower than before.

Influence of Some Environmental Factors on Summer Phytoplankton Community Structure in the Varna Bay, Black Sea (1992–2019)

“…Our results show that one of the factors that has a strong influence on phytoplankton productivity is SST. This result is similar to what Stelmakh et al (2023) [92] found in their study of a different Black Sea region.…”

“…In coastal waters near Sevastopol (the Quarantine Bay and Sevastopol Bay), Black Sea "during the last years, significant changes in the phytoplankton biomass annual dynamics and its dominant species composition have taken place. At the end of the last century and in the early 2000s, the authors observed an intensive development of small species of diatoms S. costatum, C. socialis, and C. curvisetus" [92] (p.11). They also comment that "this is mainly due to the influence of increased water temperature and growing anthropogenic pollution.…”

“…They also comment that "this is mainly due to the influence of increased water temperature and growing anthropogenic pollution. At the same time, interannual variability of phytoplankton parameters cannot be ruled out" [92] (p.11).…”

“…Reduced nutrition quality for microzooplankton and the suppressive effects of water pollutants on them caused a twofold decrease in the relative share of primary production consumed by microzooplankton. This suggests that the flow of matter and energy from phytoplankton through microzooplankton to the highest trophic levels has significantly decreased" [92] (p.12).…”

Qualitative Model of the Causal Interactions between Phytoplankton, Zooplankton, and Environmental Factors in the Romanian Black Sea

“…The current study found that, while the average temperature significantly increased during the study period, there were distinct correlations between temperature and the presence of phytoplankton and zooplankton, indicating that seawater warming has wideranging effects on marine plankton. It has been noted in the literature that the abundance of phytoplankton and zooplankton is influenced by various factors, including climatic, hydrological, biological, geological, and anthropogenic elements [56][57][58]. Additionally, both physical and chemical variables are significant contributors to the composition, diversity, and abundance of species [59][60][61], including marine organisms such as plankton [57,62].…”