LTREB: Response of a Reservoir Ecosystem to Declining Subsidies of Nutrients and Detritus

智力优势。拟议的LTREB研究将使用长期数据来测试关于水库生态系统如何应对减少的营养物和碎屑（沉积物）补贴的假设。对研究地点阿克顿湖的营养物和沉积物补贴正在下降，因为该湖农业流域的农业实践发生了变化。这些措施包括保护性耕作的显著增加和磷肥的减少。根据8年的趋势，这些变化似乎导致阿克顿湖流入河流中磷和悬浮沉积物的浓度和负荷下降。在阿克顿湖，悬浮无机沉积物的浓度下降，浮游植物的生物量增加，在此期间。我们假设，减少碎屑输入将导致一个重要的食腐鱼类，砂眼鱼的人口密度下降，导致生态系统的进一步变化。此外，我们假设，浮游植物和浮游动物的物种组成将发生变化，这样的类群典型的高生产力（富营养化）的栖息地将下降，那些典型的中营养条件将增加。这项研究的独特之处在于，它将包括对多种生态系统补贴的相互影响的长期研究：1）来自流域的营养补贴，2）来自流域的碎屑补贴，以及3）通过食鱼的营养补贴。拟议的研究也是独一无二的，因为它整合了流域，溪流和水库生态系统。虽然有许多关于天然湖泊富营养化和恢复的研究，但我们对水库如何应对减少的营养补贴知之甚少。由于美国和全球许多农业流域的营养物和沉积物输出正在下降，因此这项研究将揭示这些研究不足的生态系统如何应对广泛而共同的影响。拟议的研究将产生若干教育、环境和社会影响。本科生将通过各种项目进行暑期研究，包括REU网站项目。小学教师也将与研究生和博士后沿着招聘。数据将被共享，并继续与州和联邦机构合作。这项研究将促进决策方面的流域管理，替代农业做法（因此对农民的社会经济影响），水质和渔业管理。

Intellectual Merit. The proposed LTREB research will use long-term data to test hypotheses about how reservoir ecosystems respond to reduced nutrient and detritus (sediment) subsidies. Nutrient and sediment subsidies to the study site, Acton Lake, are declining because of changes in agricultural practices in the lake's agricultural watershed. These include a marked increase in conservation tillage and a reduction in phosphorus fertilizers. These changes appear to bedriving decreases in concentrations and loads of phosphorus and suspended sediments in Acton Lake's inflow streams, based on an 8-year trend. In Acton Lake, concentrations of suspended inorganic sediment have declined, and biomass of phytoplankton has increased, over this period. We hypothesize that reductions in detritus input will induce a decline in the population density of an important detritivorous fish, the gizzard shad, leading to further changes in the ecosystem. In addition, we hypothesize that phytoplankton and zooplankton species composition will change such that taxa typical of high productivity (eutrophic) habitats will decline and those typical of mesotrophic conditions will increase. This research will be unique in that it will consist of a long-term study on interactive effects of multiple ecosystem subsidies: 1) nutrient subsidies from watersheds, 2) detritus subsidies from watersheds, and 3) nutrient subsidies via detritivorous fish. The proposed research is also unique because it integrates watersheds, streams, and a reservoir ecosystem. Although there are many studies of eutrophication and recovery in natural lakes, we know little about how reservoirs respond to reduced nutrient subsidies. Because nutrient and sediment exports are declining in many agricultural watersheds in the US and globally, this research will shed light on how these understudied ecosystems respond to a widespread and common influence.Broader Impacts. The proposed research will have several educational, environmental and societal impacts. Undergraduates will do summer research through a variety of programs including an REU Site Program. Primary school teachers will be recruited along with graduate students and postdocs, as well. Data will be shared and collaborations continued with state and federal agencies. This research will facilitate decision-making in regards to watershed management, alternative agricultural practices (hence socio-economic influences on farmers), water quality, and fisheries management.