Ecological subsidies and ecosystem function: the role of dislodged seaweeds in the energy flow between coastal habitats

**生态系统可以通过它们之间的能量和物质流动连接起来，这是捐助国和受援国之间的一种生态补贴形式。在海洋沿海地带，从高产地区（如岩石海岸、盐沼）到生产力极低的地区（如沙滩、泥滩）的生境形成了一个相互关联的马赛克，其能量是由沿海洋流搬运的被移走的植物（如海藻、沼泽草）传递的。一般来说，波浪，尤其是在风暴期间发生的波浪，是造成植物移位的干扰因素，但在高纬度地区，海冰的冲刷可能同样重要，甚至更重要。这种增加的生态因素可以改变生态补贴过程的动态，可能对依赖这种资源的较高营养水平产生影响。*虽然这种补贴在沿海生态系统中已得到充分认识并经常观察到，但这种能量转移发生的时空动态变化在很大程度上仍未得到记录。此外，冰冲刷扰动的作用是完全未知的。然而，在圣劳伦斯海洋河口进行的初步工作显示，海岸上被移走的海藻（被称为“残骸”）聚集的时间发生了戏剧性的变化，主要发生在春天。*本提案的总体目标是确定这一生态补贴的时空动态，包括评估以下具体目标：(1)来源地区的当地海藻产量和去除海藻的对比干扰过程；(2)源区海草的迁移及其在汇区的积累；(3)对开发这一资源的动物群落（如无脊椎动物、鸟类）的影响。本研究的第一个方面将通过时间序列来解决，该时间序列将海藻床与床内波浪力和冰冲刷的高分辨率测量相结合。第二个方面将首先利用现有环流模型的粒子跟踪能力来预测源区和汇区之间可能的联系，然后通过释放和恢复漂移卡来经验验证模型的预测。最后一个方面将通过描述性和实验性工作进行调查，目的是记录海藻残骸的沉积模式，并操纵其丰度，以确定残骸的时空可用性如何影响依赖这种资源的食腐动物（即昆虫、蠕虫、甲壳类等无脊椎动物）和捕食者（例如蜘蛛和鸟类）的种群动态。总的来说，拟议的研究将提供一个从摇篮到坟墓的视角，使我们能够预测补贴将如何应对环境变化，特别是气候引起的海冰动态变化。* * *

** Ecosystems can be connected by the flow of energy and material between them a form of ecological subsidy between donor and recipient areas. In marine coastal zones, habitats ranging from highly productive areas (e.g., rocky shores, salt marshes) to ones with extremely low productivity (e.g., sandy beaches, mud flats) form an interconnected mosaic with energy transferred by the transport of dislodged plants (e.g., seaweeds, marsh grass) by coastal currents. Typically waves, especially those occurring during storms, are the disturbance agents responsible for dislodging plants, but at higher latitudes scouring by sea ice can be equally or even more important. This added ecological factor can alter the dynamics of the process of ecological subsidies with possible consequences for the higher trophic levels that depend on this resource.* Although such subsidies have been well recognized and frequently observed in coastal ecosystems, the variation in the temporal and spatial dynamics over which this energy transfer occurs remains largely undocumented. Moreover, the role of disturbance from ice scouring is entirely unknown. Preliminary work in the St. Lawrence maritime estuary has, however, shown a dramatic shift in the timing of the accumulation of dislodged seaweeds on the shore (known as “wrack”) with the dominant pulse occurring in the spring. * The general objective of this proposal is to determine the spatio-temporal dynamics of this ecological subsidy, including specific objectives that assess (1) the local seaweed production in source areas and the contrasting disturbance processes dislodging seaweeds; (2) the transport of dislodged seaweeds from these sources areas and their accumulation in sink areas; and (3) the impacts on animal assemblages (e.g., invertebrates, birds) exploiting this resource. The first aspect of this study will be addressed using time series that map seaweed beds in tandem with high-resolution measures of wave forces and ice scouring within the beds. The second aspect will be explored first using the particle-tracking capacities of existing circulation models to predict the likely connections between source and sink areas, and then by the release and recovery of drift cards to empirically validate the model's predictions. The final aspect will be investigated by descriptive and experimental work aimed at documenting the patterns of the deposition of seaweed wrack and manipulating its abundance to determine how the spatial and temporal availability of wrack influences the population dynamics of the detritivores (i.e., invertebrates such as insects, worms, crustaceans) and the predators (e.g., spiders and birds) that depend on this resource. Overall, the proposed research will provide a cradle-to-grave perspective that will allow us to predict how subsidies will respond to environmental change, especially climate-induced changes to sea ice dynamics. ***