Resource heterogeneity and the environmental basis of productivity in flowing waters

溪流食物网中使用的能量有很大一部分来自陆地植物材料和其他外部来源，即生态系统补贴。对于溪流社区内的消费者有机体来说，这些材料的食物质量、数量和可获得性有许多不同的来源。这项提案将处理这种资源异质性的原因和后果。差异的原因包括特定资源的可获得性(例如，落叶、鲑鱼身体等)。以及可获得性的物理驱动因素的变化，如水文、地貌、光输入和温度。其中许多物理驱动因素会影响对这些资源的保留，预计在气候变化情景下，驱动因素也会在时间和幅度上发生变化。资源本身是异质的，代表着有机碳和各种微生物(真菌、细菌和藻类)的复杂分类。这些不同的微生物如何相互作用，以及如何与碳源相互作用，将影响动物的食物质量和数量，但后果尚不清楚。这一系列实验将检验关于这些食物材料变异的性质的假设，这些食物材料是小溪食物网生产力的基础，以及对水生群落的影响。水生群落中的许多物种被认为是叶碎屑的义务消费者，但一些溪流中消费者的替代资源包括鲑鱼身体和生物膜，这些在时间和空间上都是高度零散的。因此，其他资源的贡献是短暂的、参差不齐的，或者两者兼而有之，但由于其高质量，可能具有潜在的重要性。我们的实验将操纵资源的质量和数量、光输入、物理结构，甚至水文(使用短距离改道)，以测试对消费者无脊椎动物及其群落的生长和生存的影响。由于气候变化、陆地植被变化以及空中运输的营养浓度增加，食物资源预计会发生变化，我们的工作将检验对预期影响的预测。

A very large proportion of the energy used within stream food webs is derived from terrestrial plant material and other external sources, i.e., ecosystem subsidies. There are many sources of variation in the food quality, quantity, and availability of these materials for consumer organisms within the stream community. This proposal will address the causes and consequences of such resource heterogeneity. The causes of variation include timing of availability of particular resources (e.g. leaf litter, salmon carcasses, etc.) and changes in the physical drivers of their availability, such as hydrology, geomorphology, light inputs and temperature. Many of these physical drivers affect retention of these resources, and drivers are also expected to change in timing and magnitude under climate change scenarios. The resources themselves are heterogeneous and represent a complex assortment of organic carbon and various micro-organisms (fungi, bacteria, and algae). How these various micro-organisms interact with each other and with carbon sources will influence food quality and quantity for animals but the consequences are not well known. This series of experiments will test hypotheses about the nature of the variation in these food materials as the basis of productivity of food webs of small streams and the consequences for the aquatic community. Many species within aquatic communities are considered to be obligate consumers of leaf detritus, but alternate resources for consumers in some streams include salmon carcasses and biofilms, and these are highly patchy in time and space. Hence, the contributions of other resources are short-lived, patchy, or both, but may be potentially important because of their high quality. Our experiments will manipulate the quality and quantity of resources, light inputs, physical structure, and even hydrology (using short-distance diversions) to test impacts on growth and survival of consumer invertebrates and their community. Shifts in food resources are expected as a consequence of variation in climate, changes in terrestrial vegetation, and enhanced nutrient concentrations from airborne transport, and our work will test predictions of expected impacts.