Biologiya Morya

The active oil and gas development of on the continental shelf negatively affects marine organisms, degrading their habitat condition and reducing their viability. The effects of drilling fluids, cuttings, and their components on various marine organisms are analyzed. The feasibility of using marine organisms as indicators of the ecological status of coastal waters at sites of intensive oil and gas extraction is discussed. The prospects of using natural substitutes for toxic components in drilling fluids to mitigate environmental risks are assessed.

The effect of illumination (10, 30, 50, and 70 μmol/m²/s) on microalga Tisochrysis lutea (Haptophyta) in a 1.8 L panel bioreactor was studied using a 5 Lux–LED flat panel (Infors HT, Switzerland) for 14 days. It was found that the most intensive growth of microalga occurred at 30 and 50 μmol/m²/s. At 10 μmol/m²/s, population growth was completely suppressed. Regardless of the light intensity, cells larger than 4 μm predominated in the algae population after seven days. The carotenoid content at illuminations of 10 and 70 μmol/m²/s was highest on the seventh day. The chlorophyll a to carotenoid ratio decreased by the end of the experiment in all conditions. The highest amount of neutral lipids in cells was noted at 10 μmol/m²/s.

The frequency of occurrence of harbor porpoises, Phocoena phocoena (Linnaeus, 1758), off the northeastern coast of Sakhalin Island (Sea of Okhotsk) was studied from 2008 to 2021. As the results showed, the frequency of occurrence of individuals of this cetacean species in the study area was subject to significant seasonal and interannual variations. The median seasonal frequency of occurrence of harbor porpoises was the highest in October (0.16 individuals per observation hour, ind./h) and was significantly different from the frequencies observed in the other study months (0.09 ind./h). The high frequency of occurrence was presumably related to the seasonal southward migration of porpoises. In 2014, 2016, and 2017, the frequency of occurrence reached the statistically highest level (0.19 ind./h), while the lowest values were recorded in 2008, 2010, 2013, and 2019 (0.07 ind./h). In the remaining seven study years, the frequency of occurrence was stable at 0.12 ind./h.