ABSTRACT:In situ plankton sampling, combined with remotely sensed and ocean Seaglider observations, provided insight into the termination of the winter monsoon bloom and subsequent evolution into a subsurface fluorescence maximum in the northwestern Arabian Sea. This subsurface maximum gradually descended, presenting increased fluorescence between 25 and 55 m depth during the spring inter-monsoon season. Species diversity decreased by half within the deep fluorescence maximum relative to the bloom. The dinoflagellate Noctiluca scintillans dominated by biomass in all samples collected from the depth of the subsurface fluorescence maximum. We show that the subsurface algal bloom persists throughout inter-monsoon seasons, linking algal blooms initiated during the southwest and northeast monsoons. In situ samples showed a net decrease in Noctiluca cell size, illustrating a shift towards a deep chlorophyll maximum adapted community, but did not exhibit any increases in chlorophyll-containing endosymbionts. We propose that the plankton biomass and estimates of the northwestern Arabian Sea productivity are much greater than estimated previously through remote sensing observations, due to the persistence, intensity and vertical extent of the deep chlorophyll maximum whichusing remote means -can only be estimated, but not measured.

Data on the diversity of dinoflagellates of the Black Sea (BS) obtained from all BS countries (Russia, Georgia, Turkey, Bulgaria, Romania and Ukraine) from 1886 to 2018 are critically ummarized. The revised list of the BS Dinoflagellata includes 420 species (447 including infraspecific taxa) from 92 genera that belong to 47 families, 16 orders and 4 classes. This significantly exceeds the number of dinoflagellate taxa previously cited for the BS. This is mainly due to an increased interest in phytoplankton in recent decades and to international cooperation. Additionally, climate change and intensification of international shipping have contributed to the appearance of invasive species of dinoflagellates in various areas of the sea. The list also includes freshwater species recorded from the less saline areas of the sea. Recent progress in taxonomy has expanded our knowledge about diversity of the BS dinoflagellates; however, the leading orders remained unchanged. Peridiniales (124 species/129 including infraspecific taxa), Gymnodiniales (96/96), Gonyaulacales (73/91), Dinophysiales (40/41), Prorocentrales (23/25) and Amphidiniales (21/22) include 85% of the species found. Genera with the highest species richness are Protoperidinium (59/62),

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