FUNCTIONAL STATE OF THE MARINE MICROALGAE CULTURES AS AN INDICATOR OF THE WATER POLLUTION LEVEL OF THE SEVASTOPOL BAY

The possibility of using cultures of Black Sea planktonic microalgae of different taxonomic affiliation to assess the quality of the aquatic environment based on the assessment of their functional state is shown. The research was carried out on the diatom Phaeodactylum tricornutum, three dinoflagellates species Prorocentrum cordatum, Prorocentrum pusillum and Gyrodinium fissum, as well as the coccolithopho-ride Emiliania huxleyi. It was found that the waters of the Sevastopol Bay in the period from May to August 2021 in 50% of cases had a weak inhibitory effect on the growth of the tested species. In other cases, algae growth was either stimulated or the effect of pollution on cultures was not revealed. The need for using several types of algae in carrying out complex work on water biotesting of the coastal are-as of the Black Sea is highlighted.

Anthropogenic plutonium radioisotopes in the ecosystem components of Sevastopol Bay (the Black Sea)

Modern levels (2010-2020) of 239+240Pu activity concentration in Sevastopol Bay (Black Sea) surface waters, 0-5 cm layer of bottom sediments and hydrobionts were determined by multistage radiochemical technique. The 239+240Pu activity concentrations in Sevastopol Bay surface water were on relatively low level: 1.08±0.09 - 1.54±0.17 mBqnr3. The maximum value of 239+240Pu activity concentration in the bottom sediments surface layer was observed in Sevastopol Bay mouth (993±90 mBqkg1) and it decreased with distance from the bay entrance to its tail end down to the minimum value - 276±53 mBqkg1. Based on these results as well as on published data the 239+240Pu deposition density distribution in the bay boxes and their inventory in 0-5 cm layer of bottom sediments were estimated in every boxes. Total 239+240Pu inventory in the bottom sediments surface layer was estimated at 121 MBq, with the highest deposition density value determined in the mouth part of the bay. Among studied hydrobiont species the highest 239+240Pu content was determined for mollusks (for their shells) Mytilus galloprovincialis (Lamarck, 1819) while the lowest - for fish Scorpaena poreus (Linnaeus, 1758). Accumulation ability of studied ecosystem components of Sevastopol Bay against 239+240Pu was characterized by evaluating concentration factors (Cf). It was shown that the bottom sediments of the bay were the main depot for plutonium anthropogenic radionucludes (Cf (239+240Pu) = n-105). The Cf (239+240Pu) were from two to three orders of magnitude lower for the hydrobionts of the bay: n-103 for brown algae and mollusks and n-102 for green algae and fish.

Nanoparticles in marine antifouling coatings: a case study

The problem of fouling of hydraulic structures, marine structures, ships and vessels has been acute since the beginning of the era of navigation. The formation of a biofilm of fouling reduces the speed of the vessel, worsens its controllability, increases fuel consumption, shortens the service life of hydraulic structures and increases the load on them. Many methods have been proposed to control fouling. One of the most promising coatings is considered to be based on the use of nanoparticles of biologically active metals and their oxides. The paper discusses various strategies for using nanoparticles to combat biofouling. The paper also presents preliminary results of a study of the antifouling efficiency of coatings modified with nanoparticles of metal oxides Fe-ZnO, ZnO, CuO. The study was carried out by exposing plates with experimental compositions at the sea test site in the Sevastopol Bay for a year, starting from August 2020. The species composition of a separate group of microperiphyton - microalgae - on plates with experimental coatings in the first two months of exposure, as well as the result of photographic fixation of the state of the surface of the plates from the point of view of macro-fouling, was investigated.

Natural-climatic and anthropogenic factors determining the self-purification capacity of shallow-water marine ecosystems in relation to reduced nitrogen forms

The paper considers natural-climatic and anthropogenic factors that determine differences in the self-purification capacity of the Sevastopol Bay ecosystems (its western, central, eastern parts and the Yuzhnaya Bay) in relation to the reduced nitrogen forms (ammonium and nitrites) by calculating the assimilation capacity. The authors took into account the intensity of the input sources of the studied forms of nitrogen, the rate of excretion from the ecosystem, the dynamic situation in the studied water areas and in the entire bay as well as the location of recreational facilities. For the first time, the factors were assessed that provide additional input of reduced forms of nitrogen associated with hypoxia during summer water stratification in local deepened areas in the upper bottom sediment layer, taking into account their particle size distribution. Further, the authors considered accumulation of organic matter and its destruction due to oxidized nitrogen forms and formation of reduced forms thereof. The currents in the central and southern parts of the Sevastopol Bay were calculated using a hydrodynamic model. The calculation results correspond to the current system in the mentioned water areas of the bay according to in situ data at different wind situations in the region. According to the calculations, it is possible that under certain hydrometeorological situations additional amount of ammonium and nitrites would flow from the Yuzhnaya Bay into the central part of the Sevastopol Bay.

Growth and morphometric characteristics of the scallop Flexopecten glaber (Bivalvia: Pectinidae) reared in cages off the coast of Crimea (Black Sea)

The spat of the scallop Flexopecten glaber were collected in cages with the Pacific oyster Crassostrea gigas cultured on a mussel-and-oyster farm (outer roadstead of Sevastopol Bay). For two years they were reared in plastic cages at a depth of 2-3 m. The cages were periodically withdrawn to measure the size and weight parameters of the molluscs: the length (L, mm), height (H, mm), and width (D, mm) of shells and the total live weight (W, g). The correlations among the parameters under study are presented. The changes in the indices of the frontal (D/L) and sagittal (H/L) curvatures, convexity ((H+D)/L) and conditional volume (H×D×L/1000) of the shells in ontogenesis are shown. Upon reaching a shell length of 30-35 mm, the allometry of the volumetric and weight growth of molluscs changed from positive to negative. The largest values of the shell convexity index were registered in thesame length range. A conclusion about the interval-type growth of F. glaber in linear size and weight is made. It is suggested that the optimal strategy of shell formation in F. glaber in ontogenesis implies the ripening and the first reproduction of the molluscs occurring at the highest volumetric characteristics of the shell. The relationships for the linear size and weight growth ofF. glaber in the first two years of life are obtained. It is concluded that the scallop F. glaber should be considered as a possible element for the diversification of the existing aquaculture of molluscs (mussels and oysters) off the coast of Crimea.

Change in plutonium sedimentation fluxes into the bottom sediments of the Sevastopol Bay before and after the Chernobyl NPP accident

The Sevastopol Bay located in the northern Black Sea was exposed to radioactive contamination by anthropogenic radionuclides, inter alia 238,239+240Pu, and to other types of anthropogenic load. One of them was the construction of breakwaters at the bay mouth in 1975–1986, which resulted in a change in the hydrological regime. The aim of this work was to assess the change in 238Pu and 239+240Pu sedimentation fluxes into the bottom sediments of the Sevastopol Bay mouth in the period before and after the Chernobyl NPP accident (1962–1986 and 1986–2013, respectively). Plutonium in sediments was determined by the radiochemical method, followed by measurement of the activity of radioisotopes with an alpha spectrometer. The sedimentation rate was defined by geochronological dating of sediment layers, accessing the change in 238Pu/239+240Pu activity ratio in the bottom sediment core. Then, the mass accumulation rate in the bottom sediments was calculated. As established, in the period after 1986, the mean annual sedimentation rate and mass accumulation rate in the bay mouth increased by 63 and 70 %, respectively. Assessment of 238,239+240Pu sedimentation fluxes during two research periods showed as follows: after 1986, 238Pu and 239+240Pu fluxes into the bottom sediments increased by 150 and 49 %, respectively. The increased 238Pu percentage in plutonium sedimentation flux after 1986 indicates Chernobyl origin of plutonium in the bottom sediment layers above 11 cm. In the post-Chernobyl period, the cumulative effect of an increase in 238,239+240Pu sedimentation flux into the bay mouth results both from an increase in the radioactive fallout intensity after the Chernobyl NPP accident and an effect of breakwaters on the regime of sedimentation processes in the water area (an increase in the mass accumulation rate).

Peculiarities of Macro- and Microelement Accumulation in Bottom Sediments of the Crimean Coastal Water Areas (the Black Sea) with Different Water Exchange Intensity based on XRF Data

The paper analyzes content and spatial distribution peculiarities of macro- and microelements in the bottom sediments of Sevastopol bays, Feodosiya Gulf and Kerch Strait. Bottom sediment sampling was performed from 2005 to 2008 as well as in 2015, 2016, and 2018. Concentrations of macro- (Ti, Fe, Mn) and microelements (As, Pb, Zn, Cu, Ni, Co, Cr, V, Sr) were studied by X-ray fluorescence analysis using Spectroscan MAKS-G spectrometer. The maximal content of Cr, Co, Ni, Zn, Pb, Sr exceeding the geochemical background was found in the water areas with difficult water exchange, which include bays of the Sevastopol region under intense anthropogenic influence: the Yuzhnaya Bay, Gollandiya Bay and Kilen-Bay. In the Kazachya Bay, the least polluted in the Sevastopol bay system, the content of Cr, Co, Ni, Zn, Pb, As, Sr also exceeded their geochemical background. As illustrated by the Balaklava Bay, the paper shows the influence of local pollution sources (the Balaklavka River runoff and municipal waste water) on the microelement distribution. Sevastopol bays are characterized by high concentrations of the studied elements in the bottom sediments. In the water areas with active water exchange, i. e. Feodosiya Gulf and Kerch Strait, concentration of the studied elements, except for Ni, Zn and Cr, did not exceed on the average the geochemical background of the open Black Sea shelf areas.

Polycyclic Aromatic Hydrocarbons in the Bottom Sediments of the River – Sea Mixing Zone on the Example of the River Chernaya and the Sevastopol Bay (the Black Sea)

Purpose. The study is aimed at determining concentrations of the polycyclic aromatic hydrocarbons (PAHs) and at revealing their pattern distribution in the bottom sediments of the "river – sea" contact zone on the example of the Sevastopol Bay and the river Chernaya. Methods and Results. Granulometric composition of the bottom sediments was determined by the decantation and dispersion method. Identification and quantitative determination of PAHs were carried out by the high performance liquid chromatography method. The total PAHs content in the bottom sediments of the area under study varied from 12 to 670 ng/g of dry weight. The pollutant content was minimum in the river site beyond the geochemical barrier. In the area where the river Chernaya flows into the Sevastopol Bay, the PAHs content was 121 ng/g. The highest PAHs content was revealed in the Sevastopol Bay bottom sediments, more precisely, in 1.5 km southwest of the river Chernaya flowing into the bay. 14 PAHs were identified in the estuary zone of the river, 4 of them (naphthalene, 2-methylnaphthalene, fluorene, anthracene) were in the trace amounts. The maximum concentration (99%) of silty material was observed in the Sevastopol Bay water area. The silt fractions were distributed as follows: 20% – aleuritic-pelite fraction, 79% – pelitic-aleurite fraction. Directly in the area of the river inflow into the bay, accumulation of the sand fraction (7%) and the maximum portion of pelitic silts were noted. Conclusions. The recorded values of PAHs corresponded to the natural non-toxic levels. PAHs identified in the bottom sediments of the river estuary zone are of the mixed, predominantly petrogenic origin. The obtained data show that in the conditions of the "river – sea" contact zone, the PAHs accumulation in general and their individual fractions were governed mainly by presence of silt in the bottom sediments.