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联系起来，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，从生产力高的地区(如岩质海岸、盐沼)到生产力极低的地区(如沙滩、泥滩)，各种生境与沿海洋流转移的被赶走的植物(如海藻、沼泽草)形成相互关联的马赛克。通常情况下，海浪，特别是那些发生在风暴中的海浪，是导致植物移位的干扰因素，但在更高的纬度，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，可能会对依赖这种资源的较高营养水平产生影响。 虽然这种补贴得到了很好的承认，并经常在沿海生态系统中观察到，但这种能量转移发生的时间和空间动态的变化在很大程度上仍然没有记录在案。此外，冰川冲刷造成的干扰的作用是完全未知的。然而，在圣劳伦斯海洋河口的初步工作表明，海岸上移位的海藻积累的时间发生了戏剧性的变化(称为“WRACK”)，主要脉动发生在春季。 这项建议的总体目标是确定这一生态补贴的时空动态，包括评估以下方面的具体目标：(1)源头地区的当地海藻产量和不同的干扰过程；(2)从这些源头地区移走的海藻的运输及其在汇区的积累；(3)对开发这一资源的动物群体(如无脊椎动物、鸟类)的影响。这项研究的第一个方面将使用绘制海藻床地图的时间序列，同时对海浪床内的波浪力和冰的冲刷进行高分辨率测量。第二个方面将首先利用现有环流模式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地验证该模型的预测。最后一个方面将通过描述性和实验工作进行调查，目的是记录海藻鱼的沉积模式并操纵其丰度，以确定海藻鱼的时空可用性如何影响依赖这一资源的有害食肉动物(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。总体而言，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.