This study delineates the role of small and medium river inputs, Low Saline Plume Advection (LSPA) and eddies in hydrography alteration and Chlorophyll a (Chl. a) in the Western Bay of Bengal. Samples were collected across five transects viz: Hooghly (HO), Mahanadi (MN), Rushikulya (RK), Visakhapatnam (VSKP) and Godavari (GD) during Fall Intermonsoon. Each transect consists of 7 or 8 locations from inshore to offshore. LSPA propagates southward concordance with the East India Coastal Current (EICC) and its southward flow strengthened by a cold-core eddy. LSPA results in the intermittent low salinity in the cross-shore section of HO, MN and RK. Upper layer Chl. a is 2–3 folds higher in inshore and in LSP-influenced locations than in its adjacent stations. The present study identified Double Chlorophyll a Maxima (DoCM) in LSPA-influenced slope regions of MN and RK. DoCM is less known in the BoB. DoCM has both the Surface Chl. a Maxima (SCM) and Subsurface Chl. a Maxima (SSCM). SSCM layer is relatively shallow and intense in slope and offshore regions of MN and RK due to their closeness with cold-core eddy. The present study highlights that freshwater discharge from small and medium rivers impacts hydrobiology around 10–50 km from the shore depends on the magnitude of river influx. LSPA is away from the local inputs and impacts hydrobiology (>500 km) along the path. EICC and eddies together regulated the direction of LSPA. Existing eddies nature alters vertical hydrobiology in slope and offshore regions.

本研究描绘了中小河流输入、低盐度羽状平流 (LSPA) 和涡流在水文改变中的作用以及西孟加拉湾的叶绿素a (Chl. a )。在秋季 Intermonsoon 期间，在五个横断面收集样品，即：Hooghly (HO)、Mahanadi (MN)、Rushikulya (RK)、Visakhapatnam (VSKP) 和 Godavari (GD)。每个样带由从近海到近海的 7 或 8 个位置组成。LSPA 向南传播与东印度海岸流 (EICC) 的一致性，其向南流动被冷核涡流加强。LSPA 导致 HO、MN 和 RK 的跨岸段出现间歇性低盐度。上层 Chl。一种近海和受 LSP 影响的位置比相邻站点高 2-3 倍。本研究在 MN 和 RK 的受 LSPA 影响的斜坡区域中确定了双叶绿素a最大值 (DoCM)。DoCM 在 BoB 中鲜为人知。DoCM 具有 Surface Chl。一个最大值（SCM）和地下叶绿素。一种千里马 (SSCM)。MN 和 RK 的斜坡和近海区域 SSCM 层由于靠近冷核涡流而相对浅而强烈。本研究强调，中小河流的淡水排放会影响距离海岸约 10-50 公里的水生生物，这取决于河流流入的大小。LSPA 远离当地输入并影响沿途的水生生物（> 500 公里）。EICC 和 eddies 共同规范了 LSPA 的方向。现有的涡流性质改变了斜坡和近海地区的垂直水生生物。