DISSERTATION RESEARCH: Thermal heterogeneity in river mainstems prolong a subsidy to tributary salmonids by migratory mayflies

自然河流是由许多不同的环境组成的。这些环境差异造成水温的变化，特别是在夏季水位低的时候。温暖的温度使许多水生昆虫比寒冷的温度生长得更快，出现得更早。由于河流内的温度变化，昆虫出现的时间并不同步。昆虫首先从温暖的栖息地出现，然后是凉爽的栖息地。可变水生昆虫的出现延长了水生昆虫从河流中的整体出现期，并为捕食者提供食物的时间比所有昆虫同时出现的时间更长。该项目调查了自然栖息地的温度变化如何维持昆虫从河流中长时间出现，以及这对捕食者（如鱼类）生长的影响，这些捕食者吃从河流中出现的昆虫。自然界中环境变化的重要性已经在其对生物多样性和物种相互作用的影响方面进行了讨论，但空间和时间变化的相互作用研究较少。 该项目研究了空间变化如何通过空间分解关键猎物物种的生活史事件转化为时间变化，以及如何影响能量向捕食者的转移，包括加州的一种猎用鱼--虹鳟鱼。这种空间异质性与其时间和营养后果的联系是普遍的重要性，但需要更多的关注，从外地生态学家在光河恢复工作，以支持健康的鱼类population.The蜉蝣Ephemerella maculata出现在阳光照射的mainstem河流，飞到黑暗，非生产性的支流，产卵，死亡。 它们的大规模迁徙补贴了原本食物有限的支流掠食者。在本项目中，假设空间非生物异质性的主干加强E。将从三个方面测试斑鳟补贴对支流青少年虹鳟生长的影响。1]通过野外饲养试验，研究了由干流地貌和水文异质性引起的热量异质性是否在空间上改变了E. [2]同位素分析将解决的问题，如果异步出现和迁移的成年E。[3]通过田间实验观察了斑节对虾对支流的长期资源补贴是否能延长其对支流的营养补贴。maculata增加营养转移的效率，因此，在关键的夏季生长期，青少年虹鳟鱼的总增长。

Natural rivers are comprised of many different environments. These environmental differences create variation in water temperatures, particularly in summer, when the water levels are low. Warmer temperatures cause many aquatic insects to grow faster and emerge earlier than cooler temperatures. Given the temperature variability which occurs within a given river, timing of insect emergence is not synchronized. Insects emerge from warmer habitats first, then cooler habitats. Variable aquatic insect emergence extends the overall emergence period of aquatic insects from the river, and supply food to predators for a longer period of time than if all insects emerged at once. This project investigates how the temperature variation in natural habitats sustains prolonged insect emergence from rivers, and effects of this on the growth of predators, such as fish, that eat emerging insects from the river. The importance of environmental variation in nature has been discussed with regard to its effects on biodiversity and species interactions, however interactions of variation in space and time are less well-studied. This project investigates how spatial variation translates into temporal variation through spatially asynchronizing life history events of a key prey species, and how that affects the transfer of energy to predators, including the steelhead trout, a game fish in California. This linkage of spatial heterogeneity with its temporal and trophic consequences is of general importance, but needs more attention from field ecologists in light river restoration efforts to support healthy fish populations.The mayfly Ephemerella maculata emerges from sunlit mainstem rivers, flies into dark, unproductive tributaries, oviposits, and dies. Their mass migration subsidizes tributary predators that would otherwise be food-limited. In this project, the hypothesis that spatial abiotic heterogeneity in the mainstem strengthens the effect of the E. maculata subsidy on the growth of juvenile steelhead trout in the tributaries, will be tested in three ways. 1] A field rearing experiment to see if thermal heterogeneity created by the geomorphological and hydrological heterogeneity in the mainstem river spatially varies the emergence timing of E. maculata; [2] Isotope analysis will address the question if asynchronous emergence and migration of adult E. maculata into tributaries prolong a trophic subsidy that would otherwise be only a brief pulse; [3] A field manipulative experiment to see if the prolonged resource subsidy by E. maculata increases the efficiency of trophic transfer, and consequently the total growth of juvenile steelhead trout, during their critical summer growth period.