Ecosystem-scale responses of coupled carbon and nutrient cycles to dramatic shifts in benthic communities: The Upper Great Lakes

该项目将研究入侵的斑马和斑驴贻贝对五大湖生物和化学的影响。这些贻贝给湖泊生态系统造成了前所未有的变化，包括水质的巨大变化、渔业的改变和娱乐机会的减少。入侵影响湖泊化学重要生态方面的机制仍然不确定，因此很难预测未来的变化。该项目将量化贻贝如何影响密歇根湖和休伦湖的沉积物和水营养化学。将收集有关沉积物和水之间化学交换变化的重要缺失数据，以量化水向沿海海洋流动时控制五大湖营养循环的过程。从这项工作中开发的改进的数值模型将允许评估受类似贻贝入侵和其他压力源影响的其他淡水和海洋系统。该项目将培养一名博士后研究员和几名研究生和本科生进行高度跨学科的研究。教育工作者和广大公众将通过创建免费的在线多媒体内容，以及在德卢斯大湖水族馆、芝加哥谢德水族馆和密尔沃基发现世界科学博物馆举办的外展活动获得服务。底栖生物群落可以对底栖-远洋化学交换产生巨大影响，但在淡水中，底栖生物对碳、氮、磷（C-N-P）耦合转化的生态系统尺度效应很少得到解决，而且几乎没有量化。最近，世界上最大的淡水生态系统劳伦森大湖被斑马和斑驴贻贝入侵，与生态和水化学的巨大变化同时发生。入侵的后果包括磷水平的大幅和无法解释的下降，硝酸盐水平过去的趋势不可思议地逆转，以及原生生物扰动双poreia片脚类动物的几乎消失。模拟表明，沉积物中的养分通量可能受到底栖生物群落变化的强烈影响。然而，解释这些变化的机制仍然模糊不清，因此阻碍了对未来生态系统轨迹的模型预测。来自明尼苏达州德卢斯大学大湖天文台的研究人员将通过对德雷塞尼德入侵的密歇根湖、休伦湖和无德雷塞尼德的苏必利尔湖进行详细研究，确定已建立的德雷塞尼德种群对五大湖沉积物地球化学和营养动态的影响。一个由生物学家和地球化学家组成的团队将(1)获得现场数据，以表征沉积物中C-N-P的地球化学特征，评估生物地球化学过程的速率，以及dreissenid对沉积物化学和物理性质的影响；(2)进行实验室实验，以确定无根dreissenids与穴洞Diporeia的功能特征如何影响沉积物特征和化学通量。(3)利用反应输运模型和质量平衡模型，了解湖泊中碳和营养物质的全湖地球化学特征。这项工作将促进对五大湖生态学的理解，并从总体上改进水生生态系统中沉积物-水柱相互作用的模型。

This project will study the effects of invasive zebra and quagga mussels on the biology and chemistry of the Great Lakes. These mussels have caused unprecedented changes to lake ecosystems, including large shifts in water quality, altered fisheries and diminished recreational opportunities. The mechanisms by which the invasion has affected ecologically important aspects of lake chemistry remain uncertain, making it difficult to predict future changes. This project will quantify how mussels affect sediment and water nutrient chemistry in Lakes Michigan and Huron. Important missing data on altered chemical exchange between sediments and water will be collected to quantify the processes controlling nutrient cycles in the Great Lakes as water moves to the coastal ocean. Development of improved numerical models from this work will allow evaluation of other freshwater and marine systems affected by similar mussel invasions and other stressors. The project will train a post-doctoral researcher and several graduate and undergraduate students in highly interdisciplinary research. Educators and the public at large will be served through creation of freely available, online multimedia content, as well as outreach events at the Duluth Great Lakes Aquarium, the Shedd Aquarium in Chicago, and the Discovery World Science Museum in Milwaukee. Benthic communities can have large impacts on benthic-pelagic chemical exchanges, but the ecosystem-scale effects of benthos on coupled transformations of carbon, nitrogen, and phosphorus (C-N-P) are rarely addressed and virtually unquantified in freshwaters. The recent invasion of the Laurentian Great Lakes, the world's largest freshwater ecosystem, by dreissenid (zebra and quagga) mussels coincided with massive changes to ecology and water chemistry. Consequences of the invasion include a large and unexplained decline in phosphorus levels, enigmatic reversal of past trends in nitrate levels, and the near-disappearance of native bioturbating Diporeia amphipods. Modeling suggests that nutrient fluxes from sediments could have been strongly affected by shifts in benthic community. Mechanisms explaining these changes, however, remain obscure and thus hamper model predictions of future ecosystem trajectories. Researchers from the Large Lakes Observatory - University of Minnesota Duluth will determine the effects of established dreissenid populations on sediment geochemistry and nutrient dynamics in the Great Lakes by conducting detailed studies in dreissenid-invaded Lakes Michigan and Huron and dreissenid-free Lake Superior. A team of biologists and geochemists will (1) obtain field data to characterize sediment geochemistry of C-N-P, asses rates of biogeochemical processes, and dreissenid effects on chemical and physical properties of sediments, (2) conduct lab experiments to determine how functional traits of sessile dreissenids vs. burrowing Diporeia affect sediment characteristics and chemical fluxes, and (3) use reactive-transport and mass-balance models to understand the whole-lake geochemistry of carbon and nutrients in dreissenid-invaded lakes. This work will advance understanding of the ecology of the great lakes and generally improve models of sediment - water column interactions in aquatic ecosystems.