Structure and Productivity of the Phytoplankton Community in the Southwestern Kara Sea in Early Summer

Knowledge of the features of the structure and productivity of the Arctic communities of marine planktonic algae is necessary to identify possible changes in the pelagic ecosystem functioning under the changing climate condition of the Kara Sea. This study shows that the species diversity, abundance of phytoplankton, and production activity of algae are at a maximum at the beginning of summer during a seasonal ice melting period. The studies were carried out in the southwestern Kara Sea and in the estuarine zone of the Ob and Yenisei rivers from 29 June to 15 July 2018. The concentrations of nutrients and dissolved organic carbon were determined. The optical properties of chromophoric dissolved organic matter, species composition, abundance and biomass of all size groups of phototrophic and heterotrophic phytoplankton, and parameters of primary production and potential photosynthetic capacity were considered. Statistical data analysis showed that the leading factors influencing changes in the abundance of phytoplankton and its productivity are the content of silicates and salinity. At the same time, the production potential of algae is realized as short-lived and small phytoplankton assemblages differed in number taxa and diversity, with an equally rapid decrease in photosynthetic activity. Such changes affect the Marine Zone to a greater extent and the Estuarine Zone to a lesser extent.

Automated summary

Knowledge of the structure and productivity of Arctic marine planktonic algae communities is crucial to understanding potential changes in the pelagic ecosystem in the Kara Sea under climate change. This study found that species diversity, phytoplankton abundance, and algal production were highest at the beginning of summer during ice melting. The study was conducted in the southwestern Kara Sea and estuarine zone of the Ob and Yenisei rivers from June 29 to July 15, 2018. Factors such as silicate content and salinity were found to influence phytoplankton abundance and productivity.