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

该项目将研究入侵斑马和斑驴贻贝对五大湖生物和化学的影响。这些贻贝对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。入侵影响湖泊化学的生态重要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。将收集关于沉积物和水之间化学交换变化的重要缺失数据，以量化水向沿海移动时控制五大湖营养循环的过程。从这项工作中改进的数值模型的发展将允许评估其他淡水和海洋系统受到类似的贻贝入侵和其他压力。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提供的在线多媒体内容以及在杜卢斯五大湖水族馆、芝加哥的谢德水族馆和密尔沃基的探索世界科学博物馆的外联活动来服务。底栖生物群落可以对底栖-中上层化学交换产生很大影响，但底栖生物对碳、氮和磷（C-N-P）耦合转化的生态系统规模影响很少得到解决，在淡水中几乎没有量化。最近，世界上最大的淡水生态系统劳伦五大湖被德雷塞尼德（斑马和斑驴）贻贝入侵，与生态和水化学的巨大变化相吻合。入侵的后果包括磷水平的大幅度和无法解释的下降，硝酸盐水平过去趋势的神秘逆转，以及本地生物扰动Diporeia端足类动物的几乎消失。模拟表明，沉积物中的营养盐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，从而阻碍了对未来生态系统轨迹的模型预测。来自明尼苏达杜卢斯大学大湖观测站的研究人员将通过在dreissenid入侵的密歇根湖和休伦湖以及dreissenid无苏必利尔湖进行详细研究，确定已建立的dreissenid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小组将（1）获得野外数据，以表征沉积物的C-N-P地球化学，评估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，以确定固着dreissenid与穴居Diporeia的功能特征如何影响沉积物特征和化学通量，（3）利用反应输运和质量平衡模型来了解德雷塞尼德入侵湖泊中碳和营养物的全湖地球化学。这项工作将促进对五大湖生态学的理解，并普遍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.