Biologiya Morya

The separate effects of acute hypoxia and hydrogen sulfide load on the marker enzyme succinate dehydrogenase (SDH) of the mitochondrial respiratory chain and the adenylate status of tissues in the bivalve mollusk Anadara kagoshimensis (Tokunaga, 1906), a species tolerant to these groups of factors, were studied under experimental conditions. The study was carried out on adult individuals with a shell height of 23–34 cm. The control group of bivalves was kept in the water with an oxygen concentration of 7.0–8.2 mgО₂/L. One experimental group was exposed to acute hypoxia (0.1 mgО₂/L) and another to hydrogen sulfide load (6 mgS^2–/L). The exposure period in both cases was 48 h. The water temperature was maintained at 17–20°C. The acute hypoxia led to an increase in the SDH activity in all the studied tissues (gills, foot, and hepatopancreas). This reaction was not observed under the hydrogen sulfide load. The energy state of the tissues decreased in both cases. This was expressed as a decrease in the ATP and ADP content accompanied by an increase in the AMP content, which allows implementation of the adenylate kinase reaction. These changes were more pronounced in the presence of hydrogen sulfide. However, the adenylate pool and adenylate energy charge (AEC) values remained at a relatively high level, which indicates the ability of ark clam to exist in the near-bottom water layers with a low level of oxygen and the presence of hydrogen sulfide. It is assumed that ark clam’s mitochondria have an alternative oxidase that is not sensitive to the presence of sulfides in water.

New outbreaks of alien species of shelled ciliates (Tintinnida) in the northeastern Black Sea are reported. Zooplankton samples were collected in the late biological summer and the fall of 2023 in the Black Sea, in the coastal zone of the port of Taman. In the study area, a total of 10 species of tintinnids were identified, among which seven were alien species. Outbreaks of the invasive tintinnids Rhizodomus tagatzi and Amphorellopsis acuta were recorded for the first time from the waters of the port of Taman. A well-defined peak of R. tagatzi abundance was recorded in September (518 × 10³ cells/m³) and A. acuta in November (310 × 10³ cells/m³). During these months, these species accounted for >99% of the total abundance of tintinnids, which indicated the formation of their populations. The abundance of R. tagatzi was the highest ever reported for the Black Sea. It is assumed that the intensive shipping traffic and increased cargo turnover characteristic of the Taman coast of the Black Sea and the Kerch Strait contribute to the spread of alien marine shelled ciliates with ship ballast water.