VNIRO - The development of plankton in the Sea of Azov
17 July 2019

The development of plankton in the Sea of Azov

Hydrobiologists of the Azov-Black Sea branch of VNIRO received new data on the status of forage and gelatinous  plankton populations in the Sea of Azov.

The hydrobiologists of the Azov-Black Sea branch of VNIRO (AzNIIRH), as a result of processing the materials collected during the expedition conducted in June of this year, received new data on the development of forage zooplankton, ctenophores and jellyfish in the Sea of Azov.

Zooplankton was selected at 29 stations (12 - in the Taganrog Bay and 17 - in the Sea of Azov itself). At 56 stations samples of ctenophore Mnemiopsis were taken. Accounting for jellyfish aurelia and rhizostomy was carried out from lampar catches.

The highest biomass  of mnemiopsis is noticed in the eastern part of the Azov Sea. In the Taganrog Bay, the ctenophore range of Mnemiopsis occupied the western part of the reservoir. The occurrence of the rhinostomy jellyfish was 15 percent. The main concentrations were noted in the southeastern part of the sea and locally in the center of the reservoir. The occurrence of Aurelia jellyfish was higher and accounted for 38 percent. The bulk of the jellyfish was found in the south-eastern, south-western and central parts of the sea, locally isolated specimens were found in the western region of the Taganrog Bay.

The data obtained are important for assessing the state of the forage base of Azov plankton-eating fish - sprat and anchovy, and the population of gelatinous organisms. In recent years, intensive development of gelatinous organisms (ctenophores and scyphoid jellyfish) has been observed in the Sea of Azov. They are strong competitors of planktophagous fish. The development of ctenophora mnemiopsis, which feeds exclusively on zooplankton, leads to a decrease in the food base of commercial plankton-eating fish. The lack of plankton feed in the summer worsens the physiological state of the fish: the fat content and fatness of the species decrease, which affects the autumn migration of the anchovy and the formation of winter aggregations of sprat.

Press Service of the Azov-Black Sea Branch of VNIRO ("AzNIIRH")