Phytoplankton play a fundamental role in marine food webs but are affected by both natural and anthropogenic fluctuations in environmental conditions. Here, to simulate a dynamic coastal environment, we used mesocosms to examine how different salinity levels and suspended solids concentrations (SSCs) impact a natural phytoplankton assemblage collected from a tropical estuary in Singapore. Significant differences in the phytoplankton composition between the baseline and treatments with medium and high SSC were found, but not among the three salinities tested. Differences can be attributed to nutrient limitation (particularly silicate) and the use of kaolinite for the suspended sediment. Silicate limitation is likely to have caused the observed switch in dominant genus from Skeletonema sp. to Chaetoceros sp. and the occurrence of weakly silicified genera such as Cylindrotheca. Kaolinite affected phytoplankton abundance through effects such as shading, flocculation, and nutrient adsorption. These results demonstrated how the combination of various physicochemical effects of suspended solids can influence tropical phytoplankton communities. Furthermore, as suspended solids such as kaolin can be found in the natural environment, this study showed that their potential effects should be evaluated beyond just their concentration.

中文翻译：

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盐度和悬浮物对热带浮游植物中世界群落的影响

浮游植物在海洋食物网中发挥着重要作用，但受到自然和人为环境条件波动的影响。在这里，为了模拟动态的沿海环境，我们使用中宇宙来检查不同的盐度水平和悬浮固体浓度 (SSC) 如何影响从新加坡热带河口收集的天然浮游植物组合。发现基线和具有中高 SSC 的处理之间的浮游植物组成存在显着差异，但在测试的三种盐度之间没有显着差异。差异可归因于养分限制（特别是硅酸盐）和高岭石用于悬浮沉积物。硅酸盐限制很可能导致观察到的骨骼虫属优势属的转换。角角藻 sp. 和弱硅化属如柱壳属的出现。高岭石通过遮荫、絮凝和养分吸附等作用影响浮游植物的丰度。这些结果证明了悬浮固体的各种物理化学效应的组合如何影响热带浮游植物群落。此外，由于在自然环境中可以找到高岭土等悬浮固体，因此本研究表明，除了它们的浓度外，还应评估它们的潜在影响。