Linking infaunal hydraulic activities, porewater flow and biogeochemical processes in marine sediments

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。大部分海洋海底遍布着动物的洞穴和管道。这些动物的活动，如挖洞、觅食和排便，对生物地球化学过程具有重要意义，因为这些活动与沉积物孔隙水的运动有关。这些生物平流过程增加了底-上层耦合和微生物活动，但对动物活动通过生物平流驱动生物地球化学循环的潜在机制知之甚少。最近的研究表明，生物平流是行为特异性的结果，水力产生的压力场从50厘米或更大的洞穴开始改变方向和径向范围。这些结果迫使人们重新评估沉积物作为生物活动深度主导的瞬态条件的栖息地。本项目探讨(a)哪些类型的动物对这些生物平流过程有重大贡献；(b)什么行为产生孔隙水通量，频率和条件如何；(c)对沉积物内氧气可用性的影响以及这种可用性的短暂性；(d)对生物地球化学速率和微生物群落结构的影响；以及(e)对生物过程的直接影响和反馈。比如初级生产力和招聘？总体目标是确定大型、数量上占优势的多毛类、双壳类和甲壳类动物对生物平流孔隙水流的影响及其对底栖生物群落的生物地球化学循环和反馈的影响。首先，利用野外和实验室测量相结合的方法，研究将分析重要大型动物的水力活动多样性，以确定哪些类型的动物对这些生物平流过程贡献最大，以及哪些行为对孔隙水通量最重要。其次，实验室实验将利用活体动物和仿生“机器人”将特定物种的水力活动与趋化动力学联系起来，以产生受控的孔隙水流。对于选定的水力行为，将分析对微生物活性和多样性的影响。最后，将使用大型实验室水族箱和现场部署的机器人来分析它们部分创建的栖息地中底栖生物群落的反馈机制。智力优势：这项研究挑战了传统观点，即大多数沉积物主要是稳态的、扩散主导的系统。这项研究将对底栖生态学、微生物生态学和生物地球化学领域产生革命性的影响，因为它清楚地表明了动物在驱动沉积物化学和物理性质变化方面所起的核心作用。更广泛的影响：两名博士后将参与该项目，并将接受研究、研究生和本科生指导、科学诚信和职业准备方面的培训。该项目还将吸引本科生参加每周的实验室会议，做部分由他们设计的研究，并每周与他们的导师PI一对一会面。所有国家都将被鼓励在国家会议上展示海报。在夏季，这些学生将参加生物学REU项目，该项目每周举行一次关于研究伦理、发表科学论文、申请研究生院以及在研究生院取得成功的策略的会议。为了让大学前的学生接触到跨学科研究的兴奋，并增加学生和教师对科学的亲身参与，研究团队将参加由科学教育中心主任Bert Ely博士管理的科学实验室项目，该项目部分由NIH资助。中学生将来南加州大学做一个符合国家科学标准的研究练习，可以在上午9:30到下午1:30之间完成。使用机器人的练习将演示生物体对沉积物的影响。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Most of the oceanic seafloor is pervaded by burrows and tubes of infauna. Activities of these animals, such as burrowing, feeding, and defecation, are of fundamental importance to biogeochemical processes as these activities are associated with movement of sediment porewater. These bio-advective processes increase benthic-pelagic coupling and microbial activity, but the underlying mechanisms by which infaunal activities drive biogeochemical cycling through bio-advection are very poorly understood. Recent work has demonstrated that bio-advection is the result of behavior specific, hydraulically generated pressure fields with changing directions and radial extent from the burrow of 50 cm or more. These results force a re-evaluation of sediments as habitats with transient conditions predominant to the depth of biotic activity. This project addresses (a) which types of infauna contribute significantly to these bio-advective processes, (b) what behaviors generate porewater fluxes, how frequently and under what conditions, (c) what is the impact on oxygen availability within the sediment and how transient is this availability, (d) what is the impact on biogeochemical rates and microbial community structure, and (e) what are the direct effects and feedbacks on biological processes, such as primary productivity and recruitment? The general goals are to determine the influence of large, numerically dominant polychaetes, bivalves, and crustaceans on bio-advective porewater flow and its consequences for biogeochemical cycling and feedbacks on the benthic community. First, using a combination of field and laboratory measurements, the research will analyze the diversity of hydraulic activities by important large infauna to determine which types of infauna contribute most significantly to these bio-advective processes and what behaviors are the most important to porewater flux. Second, laboratory experiments will link species-specific hydraulic activities to chemocline dynamics using live animals and biomimetic 'robolugs' to produce controlled porewater flows. For selected hydraulic behaviors the impact on microbial activity and diversity will be analyzed. Finally, feedback mechanisms on benthic communities in habitats that they partly create will be analyzed using a combination of large laboratory aquaria and field deployed robolugs. Intellectual Merit: This research challenges the traditional view that most sediments are primarily steady-state, diffusion-dominated systems. The research will be transformative to the fields of benthic ecology, microbial ecology, and biogeochemistry as it makes obvious the central role played by infaunal animals in driving changes in the chemical and physical properties of sediments. Broader Impacts: Two postdoctoral fellows will take part in this project and will receive training in research, mentoring of graduate and undergraduate students, scientific integrity, and career preparation. This project will also engage undergraduate students who will participate in weekly lab meetings, do research designed in part by them and meet weekly one-on-one with their mentor PI. All will be encouraged to present posters at national meetings. During the summer these students will participate in the Biology REU program, which has weekly meetings about research ethics, publishing scientific papers, applying to grad school, and strategies for success in grad school. To expose pre-college students to the excitement of interdisciplinary research and increase hands-on participation in science by students and teachers, the research team will participate in the SCience Lab program run by Dr. Bert Ely, Director of the Center for Science Education and funded in part by NIH. Middle school students will come to USC to do a research exercise that meets the state science standards and that can be completed between 9:30 am and 1:30 pm. An exercise using the robolugs will demonstrate the impact of organisms on sediments.