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

简介：本提案是为应对2008年5-7月发生在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准备的。在爱荷华州马斯卡廷16号船闸和16号大坝上方的UMR 16号泳池，从2008年5月至6月，水位突然从高度管理的10英尺上升到20英尺，然后又上升到近24英尺。这一历史性的洪灾事件恰逢上中西部高度耕种的地貌进行密集的春季耕作和养分应用活动，导致农业污染物大量涌入UMR系统。这促使科学家们预测，泥沙和营养物质将几乎史无前例地输送到第16池，更广阔的密西西比河和墨西哥湾。这一事件提供了一个独特的、短暂的机会，来检验与高度扰动的大型河流生态系统相关的科学假说。人们已经知道，这个由辫状水道和自然死水组成的生态系统不能充分处理硝酸盐等营养物质，达到保护墨西哥湾免受缺氧发作所需的程度。与洪水有关的极端泥沙淤积几乎肯定会在短期和长期影响营养物质的处理周期。众所周知，贻贝和细菌在包括浮游植物、浮游动物、微型浮游动物、溶解和微粒有机物和底栖动物的广泛食物网中，在营养循环中发挥着重要作用。鉴于这一系列事件的汇合，以及了解营养循环的重要性，我们希望测试以下假设：极端洪水造成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。迫在眉睫的需求：主要研究人员认为，这一假设只能通过快速反应小型探索性研究补助金(SGER)资助机制进行验证，因为有问题的高度摄动系统正在积极地恢复到更稳定的条件。研究小组必须尽快部署研究扰动的氮循环速率，以便将来可以与基线氮素处理速率进行比较。更广泛的影响：世界各地定期发生洪水，但考虑到全球气候变化的影响，这些事件的频率和极端情况将会增加。这项研究将有助于洪水理论的发展。这是爱荷华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、环境和人类后果以及对洪水的影响的研究。这类研究的影响可以表现为数十亿美元、数百万英亩的栖息地、数千个物种和数百年的人类享受。智力价值：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质处理动态的知识。营养负荷的突然变化和藻类成分的极端变化可能会影响食物质量，这可能会对理想的和入侵的淡水贻贝产生不利影响。这项工作将进一步描述密西西比河上游重要河段贻贝和其他生物群的营养状况与食物质量之间的关系。水质、营养物质及其对生物过程的影响是密西西比河上游的主要管理问题。

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.