Seasonal Variability of Bioluminescence and Abundance of the Dinoflagellate Noctiluca scintillans in the Arabian Sea.

Bioluminescence is a functional property used by many marine organisms for multilateral communications. In the Arabian Sea, the dinoflagellate Noctiluca scintillans (Macartney) Kofoid and Swezy, 1921, contributes gradually to the bioluminescent potential (BP) of the phytoplankton community. Experiments, field sampling, and remote sensing were employed, to estimate the seasonal variation of the BP and the abundance of cells in the northwestern Arabian Sea. An experimental setup for BP measurements integrated a "Chelsea Instruments" GlowTracka sensor, which required ~5 N. scintillans cells to obtain a statistically robust signal. Plankton were sampled with 200-μm mesh size nets, in the upper mixed layer. Also, N. scintillans cells were counted in Niskin bottle samples collected from the deep chlorophyll maximum. The remotely sensed chlorophyll-a concentration was analyzed, for the period from 2000 to 2022. A positive linear relationship between the abundance of N. scintillans cells in experiments and their BP was elucidated. Peaks of BP in experiments fit the Northeast and Southwest Monsoon periods and so did the N. scintillans abundance peaks in situ. These findings showed that BP may serve as an indicator of N. scintillans abundance and biomass in the northwestern Arabian Sea.