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。大多数大洋海底遍布着海底的洞穴和海底动物管道。这些动物的活动，如挖洞、觅食和排泄，对生物地球化学过程至关重要，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栖-远洋耦合和微生物活动，但关于底栖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还知之甚少。最近的工作表明，生物平流是特定行为的、水力产生的压力场的结果，这些压力场从洞穴50厘米或更远的地方改变方向和径向范围。这些结果迫使重新评估沉积物作为以生物活动深度为主的瞬变条件的栖息地。该项目涉及：(A)哪些类型的底栖动物对这些生物平流过程有重大贡献；(B)哪些行为会产生孔隙水通量，以何种频率和在何种条件下产生；(C)对沉积物中氧气的可获得性有何影响，这种可获得性是多么短暂；(D)对生物地球化学速率和微生物群落结构有何影响；(E)对生物过程，如初级生产力和补给，有何直接影响和反馈？总体目标是确定大型、数量占优势的多毛类、双壳类和甲壳类对生物平流孔隙水流动的影响及其对底栖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，这项研究将分析重要大型底栖动物水力活动的多样性，以确定哪些类型的底栖动物对这些生物平流过程做出了最重要的贡献，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的“机器人”来产生受控的孔隙水流，将物种特有的水力活动与趋化层动力学联系起来。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，将结合大型实验室水族箱和现场部署的机器人对它们部分创建的栖息地底栖群落的反馈机制进行分析。学术价值：这项研究挑战了传统观点，即大多数沉积物主要是稳定状态的、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底栖动物在推动沉积物化学和物理性质变化方面所发挥的核心作用。更广泛的影响：两名博士后研究员将参与该项目，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。这个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。将鼓励所有人在全国会议上展示海报。在暑假期间，这些学生将参加生物学REU计划，该计划每周举行一次会议，讨论研究伦理、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。为了让大学预科学生感受到跨学科研究的兴奋，并增加学生和教师对科学的亲身实践，研究团队将参与由科学教育中心主任Bert Ely博士运营的科学实验室项目，该项目的部分资金由NIH提供。中学生将到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之间完成一项使用机器人的练习将展示生物对沉积物的影响。

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.