Functional Diversity of Subsurface Deposit Feeders

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。在大型动物变化的极端阶段，“死亡区”的数量、频率和范围都在增加。在许多地方，生态灭绝正在发生，甚至在对消失物种的功能作用还没有得到粗略的了解之前。地下沉积物供给者主导着颗粒生物扰动并控制着有机质的埋藏，这是碳从全球范围内从与生物圈的接触中移除并被锁在地质时代的主要过程。然而，关于它们获取食物的机制、空间几何和选择性以及它们的粒子转换机制，人们知之甚少。这些信息的缺乏有效地阻碍了复杂的、基于代理人的或自动机模型的使用，这些模型将沉积-供给器效应投射到从生态时代到地质时代的底质上。两个主要障碍阻碍了理解。其一是通过MUD进行直接观察的难度。第二个问题是对这种媒介在动物洞穴和进食的空间和时间尺度上的机制缺乏了解。这两个问题同时得到了极大的缓解，使这项工作成为可能。介质的物理限制了可能的事情。它们还与其他特征(例如，介质的食物质量)一起确定哪些行为和处理速度是最佳的。调查人员有两个同步的目标。一个是测试关于地下沉积如何从它们破裂的介质中输送游离颗粒的假设，另一个是在颗粒生物扰动的背景下测量每个事件和每个人的沉积后果。他们将系统地在主要的地下沉积物供给者的多毛类群体中这样做，并在其他地下沉积物供给者中有机会地这样做。有待检验的明确假设(称为更有趣的替代假设而不是零假设)包括：裂纹扩展产生弹塑性变形，在裂纹尖端混合沉积物；裂纹扩展以重力方式取代颗粒，具有裂缝边界的动物表面的摩擦取代颗粒；以及与裂缝扩展有关的自由颗粒从基质中产生的压力脉冲在洞穴中产生的非定常流动并将其置换。更广泛的影响包括更好地理解和开发更新的教科书图表，展示海底无脊椎动物做什么以及它们是如何做的。此外，研究人员将与COSEE-OS合作，制作令人信服和准确的图形，说明生物扰动在复杂的地质记录解释中的作用，以及在碳循环中消除与当前生物圈接触的碳的步骤。这一推广活动旨在涵盖所有年龄段的专家和感兴趣的学生，他们希望了解海底的生态及其在全球碳循环中的作用。

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."Benthic community composition is changing at an alarming rate in many coastal regions. At the extreme of macrofaunal change, "dead zones" are growing in number, frequency and extent. Ecological extinction is occurring in many localities before the functional roles of the lost species are understood even crudely. Subsurface deposit feeders dominate particulate bioturbation and control the burial of organic matter, the primary process by which carbon is removed globally from contact with the biosphere and locked away for geological time. Very little is known, however, regarding the mechanics, spatial geometry and selectivity of their food acquisition and their mechanisms of particle translation. The absence of that information effectively blocks the use of sophisticated, agent-based or automaton models that project deposit-feeder effects on substrata from ecological to geological time. Two principal obstacles have blocked understanding. One is the difficulty of making direct observations through mud. The second is a lack of understanding of the mechanics of the medium on the space and time scales of animal burrowing and feeding. Both problems have been greatly alleviated simultaneously, making this work possible now.Physics of the medium constrain what is possible. They also determine in concert with other features (e.g., food quality of the medium) what behaviors and processing rates are optimal. The investigators have two simultaneous goals. One is to test hypotheses about how subsurface deposit feeders free particles from the medium that they crack, and the other is to measure the per-event and per-individual sedimentary consequences in the context of particulate bioturbation. They will systematically do so in the major polychaete groups of subsurface deposit feeders and opportunistically do so in other subsurface deposit feeders. Explicit hypotheses to be tested (phrased as the more interesting alternative hypothesis rather than the null) include: that crack propagation produces elastic-plastic deformation, mixing sediment at the crack tip; that crack propagation displaces particles gravitationally, that friction of animal surfaces with crack boundaries displaces particles; and, that unsteady flows in the burrow created by pressure pulses associated with crack propagation free particles from the matrix and displace them.The broader impacts include a better understanding and development of updated diagrams for textbooks showing what seabed invertebrates do and how they do it. In addition, the investigators will work with COSEE-OS to produce compelling and accurate graphics about the role of bioturbation in complicating interpretation of the geological record and in gating the step in the carbon cycle that removes carbon from contact with the current biosphere. This outreach is designed to cover the spectrum of specialists and interested students of all ages who want to be informed about the ecology of the seabed and its role in global carbon cycling.