Seasonal and interannual variations of the abundance of the dinoflagellate Noctiluca scintillans in the northern Black Sea

ABSTRACT

Noctiluca scintillans (Macartney) Kofoid and Swezy, 1921 contributes ∼ 85% of the total biomass of heterotrophic plankton in Crimean coastal waters. Data for the retrospective analysis come from a 20-year sampling (in 2000s) across the Crimean shelf and in adjacent open sea waters. Samples were collected onboard research vessels, in the upper 150 m layer, by Juday nets (vertical hauls) fitted with 145 µm mesh. These data were compared to field surveys of the 1960s. Seasonal blooms of Noctiluca were pronounced during summer time, with the peak of abundance in June. The mesoscale spatial distribution of Noctiluca abundance was most heterogeneous in June as well. The annual concentration of cells in coastal waters exceeded that of the open sea by four times. The coefficient of Noctiluca seasonal abundance variation in coastal waters was 1.5 times higher than that of the open sea. The Principal Component Analysis implied that the seasonal variation of the Noctiluca abundance offshore was modulated by coupling of the atmospheric precipitation, sea surface temperature, photosynthetically active radiation, euphotic depth, chlorophyll-a concentration, Noctiluca abundance in coastal waters, mesoscale eddies and wind stress. A general decline of Noctiluca abundance and biomass was observed in coastal waters, from the 1960s to the present.

KEYWORDS:

• Algal blooms
• mesosale eddies
• Noctiluca scintillans
• Black Sea

Acknowledgements

We would like to thank E.V. Popova, K.A. Galagovets, O.A. Garbazey and A.S. Kudyakova for the taxonomic processing of plankton samples and V.V. Melnikov for the archived data on the Noctiluca sampling in 1960s.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was supported by the Sevastopol State University [grant No. 42-01-09/90/2020-3], Sultan Qaboos University [grant No. IG/DVC/CEMB/21/01], and A.O.Kovalevsky Institute of Biology of the Southern Seas, Russian Academy of Sciences [grant No.121030100028-0].