Dissolved organic matter (DOM) accumulates in the upper ocean for several days to years and supports both autotrophic and heterotrophic activities. To examine the source of DOM and its role in plankton metabolic processes, 18 stations were sampled in the Bay of Bengal (BoB) during June 2019. The concentration of DOC in the upper ocean exhibited a significant relationship with Chlorophyll-a (Chl-a), particulate organic carbon (POC) and DOC exudation rates, suggesting possible sources through in situ biological processes. The mean DOC: DON ratio (8.3 ± 2) and isotopic composition of carbon in DOC (δ¹³C_DOC of −21.2 ± 1‰) indicates a marine origin in the BoB during the study period. On the other hand, dissolved organic nitrogen (DON) exhibited a significant weak inverse relationship with salinity in the northern BoB indicating some contribution from the riverine source. Phytoplankton uptake rates of amino acids (glycine or aspartic acid) were 10 times lower than dissolved inorganic nitrogen (DIN). The accumulation time of semi-labile DOC, produced by phytoplankton, in the upper ocean varied between 2.5 and 7.5 months in the BoB with the longer rate in the anticyclonic (ACE; 5.6 ± 1 months) than cyclonic eddy (CE; 3.6 ± 0.5 months) regions. This study suggests that DOM is produced through in situ processes and supports phytoplankton biomass in the BoB than hitherto hypothesized as river-borne sources and refractory in nature.

溶解有机物 (DOM) 在上层海洋中积累数天至数年，支持自养和异养活动。为了研究 DOM 的来源及其在浮游生物代谢过程中的作用，2019 年 6 月在孟加拉湾 (BoB) 对 18 个站点进行了采样。上层海洋中 DOC 的浓度与叶绿素-a (Chl-a )、颗粒有机碳 (POC) 和 DOC 渗出率，表明可能的来源是通过原位生物过程。平均 DOC: DON比率 (8.3 ± 2) 和 DOC 中碳的同位素组成 (δ ¹³ C _DOC-21.2 ± 1‰) 表示研究期间 BoB 中的海洋起源。另一方面，溶解有机氮 (DON) 在 BoB 北部与盐度呈显着的弱反比关系，表明来自河流源的一些贡献。浮游植物对氨基酸（甘氨酸或天冬氨酸）的吸收率比溶解的无机氮 (DIN) 低 10 倍。浮游植物产生的半不稳定 DOC 在 BoB 中的上层海洋中的积累时间在 2.5 到 7.5 个月之间变化，其中反气旋（ACE；5.6±1 个月）的速率比气旋涡旋（CE；3.6±0.5月）地区。这项研究表明 DOM 是通过原位产生的 处理和支持 BoB 中的浮游植物生物量，而不是迄今为止假设为河源和自然界中难降解的生物量。