SGER: The Impact of Extreme Flooding on Mussel and Microbial Nutrient Dynamics at the Water-Sediment Interface

简介：本提案是针对2008年5月至7月期间爱荷华州东部和几乎整个密西西比河上游（UMR）流域的毁灭性洪水而编制的。在爱荷华州马斯卡廷的16号船闸和大坝上方的UMR 16号池，沃茨从2008年5月至6月的高度管理阶段突然上升，从大约10英尺上升到20英尺，然后上升到近24英尺。这一历史性的洪水事件发生在上中西部地区，与密集的春季耕作和养分施用活动同时发生，导致农业污染物对UMR系统产生重大影响。这使得科学家们预测，16号蓄水池、范围更广的密西西比河和墨西哥湾将面临几乎前所未有的沉积物和营养物输送。这一事件提供了一个独特而短暂的机会，来检验与高度扰动的大型河流生态系统有关的科学假设。这种由辫状水道和天然回水组成的生态系统已经被认为不能充分处理营养物质，如硝酸盐，以保护海湾免受缺氧事件的影响。极端的，与洪水有关的沉积物沉积几乎肯定会影响营养素处理周期的短期和长期。我们还知道，贻贝和细菌在浮游植物、浮游动物、微型浮游动物、溶解颗粒有机物和底栖生物组成的广泛食物网的营养循环中起着重要作用。鉴于这些事件的汇合，以及理解营养循环的重要性，我们希望测试以下假设：极端洪水导致的颗粒有机物的强烈沉积通过物理和化学手段改变了淡水贻贝和微生物的食物网。主要研究者认为这一假设只能通过快速反应探索性研究小额赠款（SGER）来检验。由于高度扰动的系统正在积极地返回到更稳定的状态条件，因此，研究小组必须尽快部署，以研究扰动氮循环速率，以便将来与基线氮处理速率进行比较。更广泛的影响：洪水在世界各地定期发生，但由于全球气候变化的影响，这些事件的频率和极端程度将增加。这项研究将有助于发展一个？洪水理论？这是由爱荷华州大学的同事们提出的。这一理论将寻求统一有关水文学，生态学，社会经济，环境和人类的后果和影响洪水的研究。这种研究的影响可以用数十亿美元、数百万英亩的栖息地、数千个物种和数百年的人类享受来表示。智力上的优点：这项研究将扩大我们对极端洪水事件和基线时刻导致的大型河流营养物处理动态的了解。营养负荷的突然变化和藻类成分的极端变化会影响食物质量，这可能会对可取的和入侵的淡水贻贝产生不利影响。这项工作将进一步表征营养条件和食物质量之间的关系，贻贝和其他生物群在密西西比河上游的一个重要河段。水质、营养物及其生物过程的影响是密西西比河上游的关键管理问题。

Introduction: This proposal is prepared in response to the devastating floods in Eastern Iowa and nearlythe entire Upper Mississippi River (UMR) basin during May-July 2008. In UMR Pool 16, above Lock andDam 16 at Muscatine, Iowa, waters abruptly rose from a highly managed stage of approximately 10 feetto 20 feet and then to nearly 24 feet from May-June 2008. This historic flood event coincided withintense spring cultivation and nutrient application activities in the heavily farmed landscape of theUpper Midwest resulting in a significant pulse of agricultural contaminants to the UMR system. This hasled scientists to predict an almost unprecedented delivery of sediment and nutrients to Pool 16, thebroader Mississippi River and the Gulf of Mexico.This event presents a unique, and short-lived, opportunity to test scientific hypotheses related to ahighly perturbed, large river ecosystem. This ecosystem of braided channels and natural backwaters isalready known to inadequately process nutrients such as nitrate to the degree required to protect theGulf from hypoxic episodes. Extreme, flood-related sediment deposition almost certainly impacts thenutrient processing cycle in the short and long term. It is also known that mussels and bacteria play amajor role in nutrient cycling in the broad food web containing phytoplankton, zooplankton, microzooplankton,dissolved & particulate organic matter, and benthos. Given this confluence of events, andthe importance of understanding nutrient cycling, we wish to test the following hypothesis:Intense deposition of particulate organic matter from extreme flooding alters the freshwater mussel andmicrobial food webs through physical and chemical means.Immediate Need: The principal investigators feel this hypothesis can only be tested via the quickresponseSmall Grants for Exploratory Research (SGER) funding mechanism since the highly perturbedecosystem in question is actively returning to more steady-state conditions. The research team must bedeployed very soon to study the perturbed nitrogen cycling rates such that comparisons with baselinenitrogen processing rates can be made in the future.Broader Impacts: Floods occur around the world on a regular basis, but the frequency and extremity ofthese events will increase given the influence of global climate change. This research will contribute tothe development of a ?theory of floods? that is proposed by colleagues at the University of Iowa. Thistheory will seek to unify research related to hydrology, ecology, socio-economic, environmental andhuman consequences and influences on flooding. The impact of such research can be expressed inbillions of dollars, millions of acres of habitat, thousands of species, and centuries of human enjoyment.Intellectual Merit: This research will expand our knowledge of large river nutrient processing dynamicsresulting from extreme flooding events and during baseline moments. Abrupt changes in nutrientloading and extreme shifts in algal compositions can influence food quality which may adversely affectdesirable and invasive freshwater mussels. This work will further characterize the relation betweennutrient conditions and food quality for mussels and other biota in an important reach of the UpperMississippi River. Water quality, nutrients, and their effects of biological processes are key managementconcerns in the Upper Mississippi River.