Proliferation of urban structures and mangrove forests in estuaries are altering the shading of intertidal sediments. Urbanization also tends to increase nutrient loads in estuaries, which can have numerous direct and indirect effects on estuarine flora and fauna. Mangrove canopy shades the sediment and provides nutrients to the ecosystem via leaf litter. Microphytobenthos, macrofauna, sediment erodibility, and various biogeochemical properties of sediments have been shown to differ significantly between unshaded intertidal sediment and nearby sediment under a mangrove canopy. This study tested the effects of experimental manipulation of shading and addition of nutrients on the microphytobenthos, macrofauna, sediment erodibility, and selected biogeochemical properties of exposed intertidal flat next to the seaward edge of a mangrove forest. In the first of two experiments, plots were shaded with roofs to give lightly shaded plots and heavily shaded plots, for comparison with unshaded control plots; nutrients were added in an orthogonal design. Sediment and benthos were sampled after 2 weeks. Nutrients were omitted in the second experiment, with plots sampled after 2 weeks or approximately 3 months. The only effect of nutrients was a small negative effect on chlorophyll a and colloidal carbohydrate. Light shading (clear roofs) generally increased measures of microphytobenthos biomass (e.g., Fo and chlorophyll a) and biogeochemical properties associated with microphytobenthos such as colloidal carbohydrate. Heavy shading (black roofs) generally decreased measures of microphytobenthos biomass and microphytobenthos-associated biogeochemical properties. Effects on the fauna were much smaller and inconsistent with previous studies, after 3 months, assemblages were different under heavy shading compared to light shading and unshaded control plots, with differences primarily driven by changes in the oligochaetes. Natural or anthropogenic changes in shading at larger spatial scales are likely therefore to directly and indirectly change microphytobenthos, sediment properties, macrofauna and hence ecosystem functions; but any flow-on effects to the fauna are difficult to predict without further experiments to understand the indirect and direct responses of fauna to changing microphytobenthos and properties of intertidal sediment.

中文翻译：

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遮荫和养分添加对底栖微植物、大型动物和潮间带平坦沉积物生物地球化学性质的影响

河口城市结构和红树林的增殖正在改变潮间带沉积物的阴影。城市化还倾向于增加河口的营养负荷，这会对河口动植物产生许多直接和间接的影响。红树林树冠遮蔽沉积物，并通过落叶为生态系统提供养分。底栖动物、大型动物、沉积物可蚀性和沉积物的各种生物地球化学特性已被证明在无阴影的潮间带沉积物和红树林冠层下附近的沉积物之间存在显着差异。本研究测试了遮荫和添加营养物的实验操作对红树林向海边缘附近裸露潮间带的微型底栖动物、大型动物、沉积物可蚀性和选定的生物地球化学特性的影响。在两个实验中的第一个中，地块用屋顶遮蔽以给出浅阴影地块和重度阴影地块，以便与未阴影的对照地块进行比较；以正交设计添加营养素。2 周后对沉积物和底栖生物进行取样。在第二个实验中省略了营养素，在 2 周或大约 3 个月后取样。营养素的唯一影响是对叶绿素 a 和胶体碳水化合物的负面影响很小。遮光（透明屋顶）通常会增加底栖微植物生物量（例如，Fo 和叶绿素 a）的测量以及与底栖微植物（如胶体碳水化合物）相关的生物地球化学特性。重度阴影（黑色屋顶）通常会降低底栖微植物生物量和底栖微植物相关生物地球化学特性的测量值。对动物群的影响要小得多，并且与之前的研究不一致，3 个月后，与浅色阴影和未阴影对照地块相比，重度阴影下的组合有所不同，差异主要是由寡毛纲动物的变化引起的。因此，较大空间尺度上自然或人为阴影的变化可能会直接或间接地改变微型底栖动物、沉积物特性、大型动物群，从而改变生态系统功能；但是，如果没有进一步的实验来了解动物群对变化中的微型底栖动物和潮间带沉积物特性的间接和直接反应，就很难预测对动物群的任何流动效应。差异主要是由寡毛纲的变化引起的。因此，较大空间尺度上自然或人为阴影的变化可能会直接或间接地改变微型底栖动物、沉积物特性、大型动物群，从而改变生态系统功能；但是，如果没有进一步的实验来了解动物群对变化中的微型底栖动物和潮间带沉积物特性的间接和直接反应，就很难预测对动物群的任何流动效应。差异主要是由寡毛纲的变化引起的。因此，较大空间尺度上自然或人为阴影的变化可能会直接或间接地改变微型底栖动物、沉积物特性、大型动物群，从而改变生态系统功能；但是，如果没有进一步的实验来了解动物群对变化中的微型底栖动物和潮间带沉积物特性的间接和直接反应，就很难预测对动物群的任何流动效应。