Seasonal and Long-Term Phytoplankton Dynamics in the Middle Caspian According to Satellite Data and In Situ Observations in the First Decades of the 21st Century

Seasonal and long-term variability of phytoplankton in the Middle Caspian was studied based on remote sensing data sea by SeaWiFS MODIS-Aqua scanners 1998–2021 results field observations 2004–2021. The seasonal chlorophyll “a” (CHL) calculated from satellite using a regional algorithm indicated that autumn winter seasons were main production periods year. In summer, period stagnation observed growth surface layer. However, according to first months each year, blooms recurrently Sea, as confirmed biomass during vegetation reached 4.5–5.0 g/m3. decade century (2004–2006), almost entirely (as much 96%) formed through mass alien diatom Cerataulina pelagica. modern (2021), bloom both three endemic species Thalassionema nitzschioides, Cyclotella comta Dactyliosolen fragilissimus two Pseudo-nitzschia seriata spring, caspia dinoflagellate Prorocentrum micans, endemics, dominated. composed small flagellates dinoflagellates thermocline layer, which current methods cannot record. diatoms’ contribution community’s total summer did not exceed 3%. phytoplankton, role played component represented species, mainly Chaetoceros peruvianus.