The paper describes the community composition of phytoplankton in the eastern Arabian Sea (EAS) during winter monsoon (WM, January–February 2018), encompassing the entire eastern part of the Arabian Sea basin (~6–22°N and 77–67°E) with high-resolution sampling (7 transects, 56 sites), from coastal to offshore regions. The phytoplankton pigment concentrations estimated by high-performance liquid chromatography were interpreted using ‘CHEMTAX’ (Mackey et al., 1996) to determine relative abundance and contribution of phytoplankton functional groups at the class level. A distinct spatial heterogeneity was observed in the distribution of phytoplankton groups in the coastal and offshore regions of the northern as well as southern part of the EAS. The basin-scale column integrated chlorophyll a (Chl a) concentration in the upper 100 m was higher (16–118 mg m⁻²) in the northeastern Arabian Sea (NEAS) as against 9–79 mg m⁻² in the southeastern Arabian Sea (SEAS). The chromatographic analysis revealed the dominance of diatoms in the coastal waters of the EAS basin. A closer evaluation of the hydrodynamics and nutrient chemistry of the offshore regions revealed that entrainment of sub-halocline nutrients into the sunlit water column through convective mixing supported the dominant cyanobacterial population in the NEAS. In the warm oligotrophic waters of the SEAS, the substantially high NH₄⁺ concentration indicates that the dominant prochlorophytes were sustained by the regenerated production. The dominance of large phytoplankton like diatoms indicates a herbivorous control in the food chain in coastal waters of the EAS. Offshore waters are characterised by large proportions of pico-nano plankton along with considerable micro phytoplankton, which suggests a mixotrophic ecosystem. The statistical analysis showed that the silicate (Si/N ratio) concentration played a major role in controlling the diatom abundance in the coastal areas of the north (south) EAS while temperature and salinity together with nutrients structured the phytoplankton assemblage in the offshore waters during WM.

该论文描述了冬季风（2018年1月至2月，WM）期间阿拉伯海东部（EAS）浮游植物的群落组成，涵盖了阿拉伯海盆地的整个东部（约6-22°N和77-67° E）从沿海到近海地区进行高分辨率采样（7个样线，56个站点）。使用“ CHEMTAX”（Mackey等人，1996）解释通过高效液相色谱法估算的浮游植物色素浓度，以确定类别水平上浮游植物官能团的相对丰度和贡献。在东亚和北非北部和南部沿海和近海地区，浮游植物群的分布具有明显的空间异质性。盆规模柱整合叶绿素a（Chl a）在阿拉伯阿拉伯海（NEAS）的上部100 m浓度较高（16–118 mg m ^-2），而在阿拉伯阿拉伯海（SEAS）的9–79 mg m ^-2。色谱分析表明，EAS盆地沿海水域的硅藻占主导地位。对近海区域的水动力和营养化学的更仔细的评估表明，通过对流混合将亚卤代盐养分夹带到阳光照射的水柱中，支持了NEAS中主要的蓝细菌种群。在SEAS的温暖贫营养水中，NH ₄ ⁺含量很高浓度表明，主要的原绿植物通过再生生产得以维持。大型浮游植物如硅藻的优势表明在EAS沿海水域食物链中存在草食性控制。沿海水域的特点是大量的皮纳纳米浮游生物以及大量的微浮游植物，这表明是混养型生态系统。统计分析表明，硅酸盐（Si / N比）的浓度在控制北（南）东亚沿海地区的硅藻丰度中起着重要作用，而温度和盐分以及营养物质共同构成了近海东岸海域浮游植物的组成。 WM。