As the primary energy and carbon source in aquatic food webs, phytoplankton generally display spatial heterogeneity due to complicated biotic and abiotic controls; however our understanding of the causes of this spatial heterogeneity is challenging, as it involves multiple regulatory mechanisms. We applied a combination of field observation, numerical modeling, and remote sensing to display and interpret the spatial gradient of phytoplankton biomass in a Dutch tidal bay (the Eastern Scheldt) on the east coast of the North Sea. The 19 years (1995–2013) of monitoring data reveal a seaward increasing trend in chlorophyll-a (chl a) concentrations during the spring bloom. Using a calibrated and validated three-dimensional hydrodynamic–biogeochemical model, two idealized model scenarios were run: switching off the suspension feeders and halving the open-boundary nutrient and phytoplankton loading. Results reveal that bivalve grazing exerts a dominant control on phytoplankton in the bay and that the tidal import mainly influences algal biomass near the mouth. Satellite data captured a post-bloom snapshot that indicated the temporally variable phytoplankton distribution. Based on a literature review, we found five common spatial phytoplankton patterns in global estuarine–coastal ecosystems for comparison with the Eastern Scheldt case: seaward increasing, seaward decreasing, concave with a chlorophyll maximum, weak spatial gradients, and irregular patterns. We highlight the temporal variability of these spatial patterns and the importance of anthropogenic and environmental influences.

中文翻译：

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河口-沿海系统中空间浮游植物梯度的驱动因素：在荷兰潮汐湾中的案例研究的一般含义

作为水生食物网的主要能源和碳源，由于复杂的生物和非生物控制，浮游植物通常表现出空间异质性。但是，我们对这种空间异质性的原因的理解具有挑战性，因为它涉及多种调控机制。我们应用了野外观测，数值模拟和遥感相结合的方法，以显示和解释北海东海岸荷兰潮汐湾（东谢尔德）中浮游植物生物量的空间梯度。19年（1995年– 2013年）的监测数据显示叶绿素a（chl  a）在春季开花。使用经过校准和验证的三维流体动力学生物地球化学模型，运行了两个理想的模型方案：关闭悬浮喂食器并将开放边界养分和浮游植物的负荷减半。结果表明，双壳类放牧对海湾中的浮游植物起主要控制作用，潮汐输入主要影响口附近的藻类生物量。卫星数据捕获了一个开花后的快照，该快照指示了随时间变化的浮游植物分布。根据文献综述，我们在全球河口-沿海生态系统中发现了五个常见的空间浮游植物模式，以与东部Scheldt案例进行比较：向海增加，向海减少，凹面具有叶绿素最大值，空间梯度弱和不规则模式。