Data_Sheet_1_The Effects of Suspended Particulate Matter, Nutrient, and Salinity on the Growth of Amphidinium carterae Under Estuary Environmental Conditions.XLSX

The environmental conditions in estuaries display distinct variability along the river-ocean mixing continuum from turbid, eutrophic freshwater to clear, oligotrophic offshore oceanic water. In order to understand the effects of suspended particulate matter (SPM), nutrient, and salinity on phytoplankton growth, this study investigated the response of a harmful dinoflagellate (Amphidinium carterae Hulburt) to the ecological gradients in estuary environments. Rapid nutrient uptake and growth of A. carterae were detected in the nutrient-rich clear water, while nutrient concentration had little impact on the cellular chlorophyll a (Chl-a) content at the stationary phase. Light attenuation caused by SPM not only inhibited the specific growth rate of A. carterae but also prolonged its adaption period in turbid water, resulting in a delayed and weakened growth response. The elevated cellular Chl-a content under high SPM conditions resulting from photo-acclimation led to the decoupling of cell density and Chl-a concentration, indicating that Chl-a is not a reliable indicator for phytoplankton abundance in turbid environments. The combined effect of SPM and nutrient on specific growth rate of A. carterae can be explained by the comparative effect model, while the multiplicative effect model better predicted their interactive effect on the growth inhibitory rate (GIR). There is a transit of dominant limiting factor for phytoplankton growth along the salinity gradient in estuary environments. Salinity (for marine phytoplankton cannot survive under low salinity condition) and SPM are the dominant limiting factors at low salinities in nearshore turbid environments, while nutrient depletion exerts the dominant inhibitory effect in high salinity offshore water. Depending on the balance between enhancing nutrient limitation and reducing light limitation with increasing salinity, blooms most likely occur in the “optimal growth region” at intermediate salinities where light and nutrient are both suitable for phytoplankton growth.

河口地区的环境条件沿河流与海洋混合连续体呈现出显著的变异性，从浑浊、富营养的淡水资源至清澈、寡营养的近海海洋水。为了探究悬浮颗粒物（SPM）、营养物质和盐度对浮游植物生长的影响，本研究调查了有害硅藻（Amphidinium carterae Hulburt）对河口环境生态梯度的响应。在富含营养的清澈水中，A. carterae 表现出快速的营养吸收和生长，而营养浓度的变化在稳态阶段对细胞叶绿素a（Chl-a）含量影响甚微。悬浮颗粒物引起的透光率降低不仅抑制了 A. carterae 的特定生长速率，还延长了其在浑浊水中的适应期，导致生长反应的延迟与减弱。在高 SPM 条件下，由于光适应导致的细胞 Chl-a 含量升高，导致细胞密度与 Chl-a 浓度之间的解耦，表明 Chl-a 并非浑浊环境中浮游植物丰度的可靠指标。悬浮颗粒物与营养素对 A. carterae 特定生长速率的联合效应可用比较效应模型解释，而乘法效应模型能更好地预测其对生长抑制率（GIR）的交互作用。在河口环境的盐度梯度中，浮游植物生长的主要限制因素发生了转变。在近岸浑浊环境中，盐度（海洋浮游植物在低盐度条件下无法生存）和 SPM 是低盐度下的主要限制因素，而在高盐度的近海水中，营养耗竭施加了主要的抑制效应。根据盐度增加时增强营养限制与减轻光限制之间的平衡，浮游植物的爆发最有可能发生在中间盐度的“最佳生长区域”，在此区域光和营养均适宜浮游植物的生长。