Collaborative Research: Intermediate Regulations of Aquatic Ecosystems: Pursuing the Generality of the Trophic Cascade Hypothesis

这项建议旨在扩大正在进行的水库工程， 小水库，追求的一般性评价， 营养级联假说 这一假设目前 正在北温带开放水域和近岸、底栖 社区. 东南部水库，这项工作的重点， 与北方湖泊的显著不同在于， 杂食动物，砂囊鲱，大量出现。 不受控制 鱼类捕食者（由于令人印象深刻的繁殖力加上 对捕食者的脆弱性的狭窄窗口），也不是由他们的 浮游动物捕食（继仲夏浮游动物崩溃之后， 沙鱼转向碎屑和浮游植物），砂囊沙鱼调节 通过“中间出”过程组成社区，而不是 被自上而下或自下而上的力量所控制。 这些 研究人员设计了一系列实验， 评估的空间尺度范围（1立方米至100公顷） 砂囊鲱是否能控制浮游动物的数量， 因此，蓝鳃金龟（通过剥削性竞争， 浮游动物）和大口黑鲈（通过减少他们的蓝鳃 猎物）。 过去5年收集的初步证据 有力地支持了砂囊沙很可能 驱动器社区组成的俄亥俄州水库，从而作为一个 “关键”物种，可能很好地运作在一个“中间” 时尚. 本研究的实验方法将评估 级联假说的一般性，通过评估其 水库食物网中的概念力量， 生物联系

This proposal seeks to extend ongoing work in reservoirs and small impoundments, pursuing an evaluation of the generality of the trophic cascade hypothesis. This hypothesis is currently being tested in north temperate open-water and inshore, benthic communities. Southeastern reservoirs, the focus of this work, differ dramatically from northern lakes in that an open-water omnivore, gizzard shad, occurs in abundance. Neither controlled by fish predators (owing to impressive fecundity coupled with a narrow window of vulnerability to predators) nor by their zooplankton prey (following the mid-summer zooplankton crash, shad switch to detritus and phytoplankton), gizzard shad regulate community composition via "middle-out" processes, rather than being regulated by top-down or bottom-up forces. These investigators have designed a series of experiments across a range of spatial scales (1 m3 to 100 hectares) to evaluate whether gizzard shad can control zooplankton populations and hence recruitment of bluegill (via exploitative competition for zooplankton) and largemouth bass (by reducing their bluegill prey). Preliminary evidence gathered during the past 5 years strongly supports the perspective that gizzard shad may well drive community composition in Ohio reservoirs, thus serving as a "critical" species that may well operate in a "middle-out" fashion. The experimental approach of this study will evaluate the generality of the cascade hypothesis by assessing its conceptual strength in reservoir food webs comprised of weak biotic linkages.