Vol 44, No 1 (2018)

The spatial variability of the photochemical efficiency of phytoplankton photosystem II was analyzed in two contrasting regions of the Black Sea: the western part of the deepwater region and a region influenced by the Danube River discharge. The fluorescence values for open (F₀) and closed (F_m) photosystem II reaction centers in the investigated areas varied by an order of magnitude and correlated closely. The potential photochemical efficiency of phytoplankton photosystem II (F_m − F₀)/F_m varied from 0.16 to 0.70. Three types of the vertical distribution of this index were found. In the first type, the values increased from the surface to the top of the thermocline and then remained stable down to the bottom of the euphotic zone; in the second type, they increased from the surface to the bottom of the euphotic zone; in shallow areas, they were stable within the euphotic zone. With an increase in light intensity, the phytoplankton photochemical efficiency decreased. The light inhibition of the photosystem II efficiency was more intense in the deeper than in the upper layers of the euphotic zone.

The effect of temperature on sexual reproduction and the rate of vegetative division were investigated in laboratory experiments with Haslea ostrearia (Gaillon) Simonsen from the Atlantic and H. karadagensis Davidovich, Gastineau et Mouget from the Black Sea. In the range of 10–26°С, a temperature increase was favorable for vegetative growth; the maximum growth rate was recorded at the highest temperature of the range. In contrast to vegetative growth, sexual reproduction of both algal species was effective in the temperature range of 10–18°С, but did not occur at temperatures of 23°С. The optimal temperature for auxosporulation was in H. karadagensis somewhat lower than in H. ostrearia. The determined physiological optimums for sexual reproduction can explain the cell-size distribution that is characteristic of the natural population of H. karadagensis in different seasons of the year.

The state of the macrophyte community of Zostera marina + Stephanocystis crassipes in the cove off Cape Tokarevsky (Eastern Bosphorus Strait, Sea of Japan) was evaluated, using the method of sample plots, in June 2014. The taxonomical and morpho-functional composition, as well as the structure of the community, has been studied. A total of 39 species of marine macrophytes have been found in this area, including 6 species of Chlorophyta, 22 species of Rhodophyta, 10 species of Phaeophyceae, and 1 species of Tracheophyta (Zostera marina), which constitute 15, 56, 26, and 3% of the total number of species in the community, respectively. The studied phytocenosis is characterized by a poor taxonomic composition, a high biomass of opportunistic species (auxiliary species on the dominance scale), and the proportions of higher algal taxa typical of the clean waters of Peter the Great Bay. Thus, based on a combination of these characteristics, the Zostera marina + Stephanocystis crassipes phytocenosis can be regarded as being in an early stage of anthropogenic transformation and the waters are classified as moderately polluted.

Port landing specimens of torpedo scad, Megalaspis cordyla were collected at monthly intervals from August 2013 to June 2014 from the northern Arabian Sea coast of Pakistan. The life history characteristics revealed that torpedo scad has a prolonged breeding season which occurred with two peaks: from May to June and from November to February. The spawning seasonality was also validated with microscopic gonad examination.The highest GSI value was noted in May and January whereas the lowest in November was recorded for both sexes. The age at which individuals of both sexes become 50% mature (t₅₀) was estimated as 2.44 year. Life span (t_max) calculated as 3.96 years for male and females. The size of 270 and 265 mm at which 50% individuals attained sexual maturity (L₅₀) was determined for males and females respectively. The reproductive potential (fecundity)was made from ten ripe females ranged from 29–43.8 cm TL and weighing 220–540 g of IV–V developmental stage was enumerated as 32306–236677 eggs (CV = 2.135) with an average number of eggs 86544 counted per ripe female/season. This study contains fundamental data of an important fish species in the northern Arabian Sea coast of Pakistan. It provides vital information to the fisheries managers for implementation on sustainable use of the resource during spawning season.

Research on a southern herd of white (beluga) whales conducted during the summer seasons of 2003–2006 in the southeastern part of the Onega Bay revealed the specific behavioral features that allow white whales to sustain their habitation in the local hydrological conditions. It has been shown that once the white whales occur in some areas of habitation with complicated hydrological conditions, the animals develop an entire complex of behavioral adaptations that provide their comfort and their successful reproduction in the habitat.

The variability of Fe, Mn, Zn, Cu, Pb, Cd, and Ni concentrations was studied in soft tissues of the common mytilid mollusk Septifer bilocularis collected in May 2013 at the coral reefs along the entire Vietnamese coast from the Gulf of Siam to Ha Long Bay. The salinity, suspended solids, and nutrients were determined during the sampling; these hydrochemical characteristics of the surrounding waters were controlled by the river runoff and the content of chlorophyll a. The concentration of Mn in the mollusk S. bilocularis was elevated under the river runoff effect. However, concentrations of Cd and Zn in S. bilocularis were the lowest within the areas of river influence and increased in waters of central Vietnam and the Gulf of Siam, where upwellings are an important driving force. A comparison of our data with those obtained for Mytilidae from other regions showed that the mussel S. bilocularis can be recommended for biomonitoring of the concentrations of trace metals in the waters of coral ecosystems along the Vietnam coast.

Sexual dimorphism in the stone cockscomb Alectrias alectrolophus was studied for the first time. No pronounced differences were found in plastic characters between the females and males of this species; however, there were differences in the structure of the urogenital papilla that allow reliable sex determination.