The study assesses dynamics of phytoplankton biomass in the surface layer, the depth of the upper mixed layer, and the photic zone based on satellite data in the deep sea and coastal regions of the Black Sea for 1998–2015. The annual biomass dynamics had the same character in all regions and was described by a U-shaped curve with some deviation in the spring. Average seasonal values were at the maximum in winter and minimum in summer, differing by 2–2.5-fold. Phytoplankton blooms with an average duration 1–2.5 months were present in all seasons, but with different frequencies. The highest numbers were recorded in spring, minimal numbers in summer and fall; during the bloom, biomass was twice as much as the background values. Phytoplankton biomass grew with decrease in water temperature and increase in mixed layer depth during fall. There was no such dependence during the other seasons. The dynamics of the annual average biomass showed negative trend in the deep sea from 1998 to 2015, the latter was not observed in the coastal zone. The strongest decrease in biomass was recorded in spring and summer; it was not observed in winter and fall.

В отличие от контактных методов, использование спутниковых данных для изучения динамики хлорофилла a даёт возможность проводить исследования на больших масштабах с высокой частотой измерений. Такие наблюдения выполнены в глубоководной части и прибрежном районе Чёрного моря в период с 1998 по 2015 г. Они позволили определить годовую динамику концентрации хлорофилла a в поверхностном слое и выявить периодичность, интенсивность и продолжительность массового развития водорослей. Годовая динамика концентрации хлорофилла в западном и восточном циклонических круговоротах, а также в зоне шельфа у крымских и кавказских берегов имела одинаковый характер, повторяющийся из года в год. С августа-сентября по апрель-май следующего года изменение хлорофилла в большинстве случаев соответствовало нормальному распределению и имело вид колоколообразной кривой с максимумом в декабре-январе. В течение осеннего периода значения концентрации хлорофилла постепенно повышались по мере охлаждения воды, ослабления сезонного пикноклина и увеличения скорости потока биогенных веществ из нижних слоёв к поверхности. Зимой глубина перемешиваемого слоя достигала значений, в несколько раз больших, чем осенью, что могло приводить к уменьшению концентрации хлорофилла в единице объёма воды. Весеннее интенсивное развитие фитопланктона наблюдалось в конце марта ― начале апреля при ослаблении конвективного перемешивания и повышении устойчивости водного столба.

A strain of aeroterrestrial green microalgae Coelastrella rubescens IBSS-156, isolated from an epilithic lichen, has been previously shown to efficiently produce green biomass and accumulate significant amounts of secondary carotenoids. In this study, using a two-stage batch culture, we analyzed time-course changes in variable chlorophyll a (Chl a) fluorescence parameters. Additionally, regression models were developed to correlate autofluorescence signals with spectrophotometric measurements of Chl a and total carotenoid content. Maximum quantum efficiency of photosystemII (F_v/F_m) remained high throughout the vegetative stage. At the end of this stage, under nutrient-limited conditions, the relative electron transport rate (rETR) declined to half its peak value during exponential growth. Stress induced a strong response in the algal photosynthetic apparatus during the early red stage. Within the first three days, F_v/F_m and rETR remained extremely low, but both increased sharply by day 5. During secondary carotenoid accumulation, fluorescence parameters remained at 70–80% of the vegetative-stage maximum, followed by a sharp decline toward the end of the red stage. Therefore, changes in variable fluorescence parameters can serve as markers of C. rubescens cellular physiology during biotechnological cultivation, denoting the completion of specific stages. Flow cytometry and pigment assay regression enabled real-time monitoring of C. rubescens biomass and carotenoids.

The copper toxic effect was studied on two species of Black Sea diatoms Cerataulina pelagica and Phaeodactylum tricornutum, and two species of dinoflagellates Levanderina fissa and Prorocentrum nanum. A wide range of variability in the resistance of cultures to copper as a toxicant is demonstrated. The EC50 values for different species varied from 1.8 to 43.7 mg·L-1. An increase in the algae initial biomass within one species caused a corresponding decrease in the toxic effects of Cu2+. The two species of dinoflagellates with similar initial biomass and practically equal values of the specific growth rate, demonstrated significant difference in the EC50 parameter. In the small - celled species P. nanum it was equal to 43.7 mg·L-1, whereas, in the large species L. fissa, it decreased by almost 10 times. In the small-cell strain of the diatom C. pelagica, the semi-inhibition growth parameter was 13.5 mg·L-1, which is 2.4 times higher than in the large-cell strain with all other conditions being equal. The copper toxicological effect at low concentrations is determined, first of all, by a decrease in the electronic transport rate values (rETR) in cultures. The second parameter in terms of sensitivity to copper is Fv/Fm (maximum efficiency of photosystem II). The algae morphometric parameters are the most resistant to its impact: the volume and cell’s surface area, as well as the specific surface area. The significant changes on the third day of experiments were observed most often, at a copper concentration near EC50 or above.

In the surface layer of the Sevastopol and Quarantine bays, during 2000–2014 in summer and in autumn, the average values of the concentration of chlorophyll a and phytoplankton biomass are reduced by a factor of 2–5. This is due to a decrease in the content of nitrates and silicon compounds in water, as well as the relative proportion of diatoms in the total biomass of phytoplankton. Regression analysis showed that in the summer period the long-term negative trend in the change in the relative biomass of diatoms was determined mainly by the nitrate content in the water and its temperature, while in the autumn – by the content of nitrates and silicon. The share of dinoflagellates and coccolithophores increased over the entire observation period. In winter and spring in bays, and in the open coast during all seasons, unidirectional changes in the concentration of chlorophyll and the total biomass of phytoplankton were not detected.