Sea Surface Temperature and Phytoplankton Abundance as Crucial Proxies for Green Noctiluca Bloom Monitoring in the Northeastern Arabian Sea: A Case Study

Green Noctiluca scintillans ( NS G) is a mixotrophic dinoflagellate that frequently forms intense blooms in the north Indian Ocean, especially in the northeastern Arabian Sea during winter. This study investigates the conducive conditions and drivers associated with NS G blooms and proposes significant models for estimating NS G based on in situ (time-series) study during the bloom cycles. Two critical factors with regard to the blooms, i.e., phytoplankton abundance and sea surface temperature (SST), were examined. The first phase of heterotrophy dominance was when moderate blooms up to ~ 2.26 × 10 4 cells 1 –1 occurred and, when NS G cells per unit chlorophyll- a (chl- a ) increased, SST decreased up to ~ 24.5 ºC. The bloom intensity was proportional to the feed (diatoms/phytoplankton) availability and the degree of cooling (by the winter convection, i.e., nutrient enrichment). In the second phase of autotrophy dominance, intense blooms up to 1.9 × 10 5 cells l −1 occurred and NS G cells per unit chl- a fell, when the SST increased. During this period, bloom intensity was proportional to the degree of warming, i.e., nutrient and physiological stress. Phytoplankton are related to NS G by a single linear model through this SST cycle and is likely the NS G’s essential biotic precursor. Attention is then focused on developing a remote sensing reflectance ( R rs ) model for efficient synoptic monitoring of NS G using ocean color satellites. The R rs band product ratio, a new metric, in combination with SST, notably modelled NS G abundance, which may be of potential routine application.