Volume 45, Nº 3 (2019)

The population and reproductive characteristics of the hermit crab Pagurus brachiomastus (Thallwitz, 1892) have been examined in Vostok Bay (Peter the Great Bay, Sea of Japan). The average population density of P. brachiomastus was lowest in the spring (2.4 ± 0.6 ind./m²) and highest (3.1 ± 0.4 ind./m²) in the summer; the biomass was 18.24 ± 3.75 and 22.83 ± 2.80 g/m², respectively. Hermit crabs were found throughout the depth range from 0 to 12 m, but were most numerous at a depth of approximately 5–6 m, with an average population density of 8.3 ± 3.7 ind./m² and a biomass of 39.09 ± 8.51 g/m² in the summer. The shield length of males varied from 1.3 to 10.3 mm (on average, 5.3 ± 2.2 mm), that of females varied from 1.3 to 10.6 mm (on average, 4.3 ± 1.5 mm), and that of ovigerous females varied from 1.5 to 8.4 mm (on average, 4.4 ± 1.5 mm). The male to female ratio varied from 0.8 to 3.3 during the observation period, with an average of 1.7. Spawning continued from March through August. The proportion of ovigerous females increased from 8.5% in March to 82.8% in May; embryos in clutches remained in the early stage of development until the second 10-day period of May. Egg development was resumed when the water temperature reached 10°C. Breeding was asynchronous: in June–August, females with late-stage embryos and females with recently laid eggs were observed, indicating the possibility of repeated spawning. The data we obtained showed that the favorable coexistence of P. brachiomastus with other sympatric species in the study area is provided by the spatial dissociation of their clusters and differences in size characteristics, as well as the presence of an embryonic diapause in egg development in part of the females and the possibility of repeated spawning.

Research on the concentrations of the metals Cu, Cd, Fe, and Mn showed no significant relationships between metal concentrations in water and in brown algae of the Sea of Japan with background concentrations. A significant correlation between metal concentrations in the environment and in the algae was found for zinc; it was the only metal with a wide variation in concentrations exceeding background levels in the habitat of macrophytes. Correspondingly, the only significant correlation between the bioaccumulation factor (BAF) of seaweeds from the Sea of Japan and the content of this element in seawater was found for zinc. It was shown for all studied metals that the highest and most variable BAF values for algae were observed within the background range of metal concentrations in the aquatic environment, which allows us to express the background range (the range caused by natural conditions) graphically. Thus, the high variability of the BAF values of aquatic organisms in the background environmental conditions necessitates very cautious interpretation of biomonitoring data.

The contents of amino acids and glucose, the activity of alanin aminotransferase (ALT), aspartate aminotransferase (AST), and the AO enzymes superoxide dismutase (SOD), catalase, glutathione peroxidase (GP), and glutathione reductase (GR), as well as the level of reduced glutathione (GSH) and TBA-reactive products, were investigated in the hepatopancreas, gills, and the foot of Black Sea bivalve mollusks: the blood cockle Anadara kagoshimensis (Tokunaga, 1906) (Bivalvia: Arcidae) and the mussel Mytilus galloprovincialis (Lamarck, 1819) (Bivalvia: Mytilidae) with their different tolerances to oxidative stress. Higher contents of glucose in the hepatopancreas and the foot and amino acids in the foot and a higher activity of AST in the gills were found in the mussel, which is relatively tolerant to hypoxia. Compared to blood cockle, mussels showed a higher GP and GR activity in hepatopancreas, GP activity in gills, and SOD activity in hepatopancreas and foot against the background of a higher content of TBA-reactive products in all studied tissues. A high content of amino acids was determined in the hepatopancreas and the gills of the blood cockle, which had a high tolerance to low oxygen. The activity of the ALT and AST enzymes in the foot and the activity of the ALT enzyme in the gills were higher in the blood cockle tissues than in the mussel tissues. This can be connected with more intensive processes of deamination and re-amination of amino acids in the cockle than in the mussel. The blood cockle had higher GP activity and GSH content in the foot and higher activity of SOD, catalase, and GR, as well the GSH level in the gills with a lower content of TBA products. The revealed peculiarities of the AO complex reflect adaptations of the mollusks to the oxygen regime in their habitat on the basis of specific peculiarities of their carbohydrate–protein metabolism.

The vertical distribution of the concentration of chlorophyll a (Chl) and colored dissolved organic matter (CDOM), temperature (T), and salinity (S) were studied at two diel stations located at close coordinates and performed at a weekly interval and seven stations spaced 1 mi apart on hydrological section in the shelf zone of Possjet Bay (Sea of Japan) in the autumn of 2014. The Chl concentration was estimated from fluorescence intensity (FChl). In the surface layer of the diel stations, the Chl concentration varied within ± 10% of the mean value. In the water column, a negative correlation of FChl with T and a positive relationship of S with CDOM were established at both stations. At all stations, the maximum Chl concentration occurred under the seasonal pycnocline layer.

An investigation was carried out at eleven different transect points from 0 to 10 km in the coastal waters of Chandipur, Bay of Bengal (between 21°27′10.4″ N and 87°04′9.02″ E to 21°21′46.54″ N and 87°07′29.41″ E) during winter, summer and monsoon on hydrography and plankton diversity. Productivity in Chandipur coastal water was found to be higher during winter compared to summer and monsoon season. Chlorophyll concentration was 0.32 ± 0.35 mg/m³ in winter, 3.17 ± 0.12 mg/m³ in summer and 2.51 ± 0.16 mg/m³ in monsoon, respectively. Similarly, the average phytoplankton cell count for winter, summer and monsoon season was observed to be 26 618 ± 13 529 cell/L, 14 136 ± 8258 cell/L and 6909 ± 3769 cell/L. Nutrient ratio (N : Si : P) ranged between 5 : 0.1 : 1 to 30 : 0.2 : 1. Two-way ANOVA test (p ≤ 0.001) was tested and showed significant variation in the phytoplankton distribution. A total of 70 phytoplankton species belonging to 36 genera were identified, and Chandipur coastal water was found to be dominated by diatom species. Silicate concentration was comparatively low which could be attributed to the presence of diatoms in coastal water. Species diversity was observed to be maximum in winter (47 species) followed by summer (46 species) and monsoon (35 species) season.