Fall-winter sea surface temperature anomalies affect subsequent spring-summer phytoplankton succession and bioluminescence patterns in the Black Sea coastal waters near Crimea

Seasonal and interannual dynamics of bioluminescence intensity and succession of the major phytoplankton taxonomic groups were analyzed using the six-year monitoring of Crimean coastal waters (the northern Black Sea) in 2009-2014. Monitoring program included regular CTD and bioluminescence intensity casts in the upper 60 m layer by means of Salpa-M sonde accompanied with phytoplankton sampling from subsurface (similar to 0.2 m) and from the layer of maximal bioluminescence intensity. Years with anomalous warm and cold preceding fall-winter periods were defined on the basis of remotely sensed monthly sea surface temperature (SST) and long-term records on coastal SST measuring station. It was shown that succession of phytoplankton and net verti-cal bioluminescence patterns in subsequent spring-summer seasons depend upon the SST anomaly during pre-ceding fall-winter period. In cold years a minimal bioluminescence intensity associated with a diminished biomass and species abundance of luminous dinoflagellates as well as diatoms and dinoflagellates groups as a whole were observed. A number of luminous dinoflagellate species dropped out of spring phytoplankton com-munity (e.g., Scrippsiella cf. acuminata). As a result, a typical spring peak of bioluminescence in the upper mixed layer has not been observed during these years. In contrast maximal bioluminescence intensity and phyto-plankton abundance in spring-summer was observed in warm years; biomass and bioluminescence intensity peaks shift to earlier month (April) in comparison to moderate years; period of dinoflagellate dominance was more extended during the spring-summer succession phase. Overall, group of dinoflagellates including luminous species, seems to be the most sensitive group of algae to climatic SST anomalies in coastal waters of the northern Black Sea. Hence, the bioluminescence in the upper sea layer can act as an indicator of climate-induced phytoplankton community restructuring.

Automated summary

Seasonal and interannual dynamics of bioluminescence intensity and succession of major phytoplankton taxonomic groups in Crimean coastal waters were studied. The study found that the succession of phytoplankton and bioluminescence patterns in the following spring-summer seasons depended on the sea surface temperature anomaly during the preceding fall-winter period. Cold years showed minimal bioluminescence intensity and decreased biomass and species abundance of luminous dinoflagellates, diatoms, and overall dinoflagellates. Warm years exhibited maximal bioluminescence intensity and earlier peak in biomass and bioluminescence intensity, with a longer period of dinoflagellate dominance during the spring-summer succession phase.