Size-based partitioning of phytoplankton biomass is a crucial determinant of the type of food web functioning in an aquatic ecosystem. Seasonal and spatial distribution of total as well as size-fractionated phytoplankton biomass (pico, nano and micro-phytoplankton) from the tropical creek (Thane creek, India), was assessed in response to ambient physicochemical parameters. Nanophytoplankton biomass contributed the significant fraction (69%–97%) of total phytoplankton biomass throughout the creek irrespective of the seasons. The ability of nanophytoplankton to proliferate under low solar insolation helped them in sustaining high biomass in nutrient-rich turbid water. Microphytoplankton, which was the second dominant class, contributed 3%–19% during pre-monsoon, 11%–19% during monsoon and 3%–7% during post-monsoon. High suspended sediment load and mesozooplankton grazing pressure have played an essential role in structuring the microphytoplankton biomass. Competitive disadvantage under high nutrient concentration resulted in low picophytoplankton biomass throughout the creek. The dominance of nanophytoplankton biomass deciphered the prevalence of herbivorous based food web in the Thane creek. The Pearson’s correlation and the canonical correspondence analysis interpreted nutrient enrichment, suspended sediments and temperature played a significant role in determining the size structure of phytoplankton biomass. The eutrophication status of the study area studied using Trophic state index (TRIX). Availability of surplus nutrient during all the seasons could be the main factor behind the eutrophic to hypereutrophic (6.7-8.8) condition of the Thane creek.

浮游植物生物量的基于大小的划分是决定水生生态系统中食物网功能类型的关键决定因素。根据环境理化参数，评估了热带小溪（印度塔那河）的浮游植物总生物量以及大小分级的浮游生物量（微微，纳米和微型浮游植物）的季节性和空间分布。不论季节如何，纳米级浮游植物的生物量在整个小河中占浮游植物总生物量的很大一部分（69％–97％）。纳米浮游植物在低日照下增殖的能力帮助他们在营养丰富的混浊水中维持高生物量。浮游植物是第二大优势类，在季风前贡献了3％–19％，在季风期间贡献了11％–19％，在季风后贡献了3％–7％。高悬浮泥沙负荷和中层浮游生物的放牧压力在构造浮游植物生物量方面起着至关重要的作用。在高营养物浓度下的竞争劣势导致整个小河的浮游浮游生物量较低。纳米浮游植物生物量的优势破译了以塔恩河为食的草食性食物网的流行。皮尔逊相关性和规范对应分析解释了养分富集，悬浮沉积物和温度在确定浮游植物生物量的大小结构方面起着重要作用。使用营养状态指数（TRIX）研究研究区的富营养化状况。在所有季节中，剩余养分的可用性可能是塔那河从富营养到富营养化（6.7-8.8）状况的主要因素。