Nutrition of Reef Corals: Effects of Morphology, Resource Availability, and Water Flow

珊瑚礁生态系统依赖于各级水的运动。水的运动为珊瑚提供了猎物，并加强了营养物质、氧气、二氧化碳、碳酸氢盐和其他离子的吸收和交换。它还影响珊瑚竞争、幼虫扩散、碎片化、捕食者的活动和沉积，因此对珊瑚分布有很大的潜在影响。珊瑚礁上的流动微生境差异很大，甚至超过几米或更少，导致珊瑚生长速度的明显差异。虫黄藻(光合作用)对珊瑚能量学的贡献最大程度地受到流动下端的扩散限制的影响，而辐射变化则对其进行了修正。最小尺度的水流影响珊瑚的呼吸、生产力和悬浮摄食过程，影响浮游动物遇到珊瑚的逃逸行为，以及特定的息肉、触角和群落形态的最终成功。在整个珊瑚礁上，存在着从浅礁区的高速振荡(波浪诱导)流到深礁和泻湖生境中的低速单向流的特征梯度。这种流动状态影响底栖-中上层通量以及珊瑚礁物种配子和幼虫的扩散。珊瑚的息肉大小、触须形状和群体结构各不相同；每个珊瑚礁区域的珊瑚生长形式反映了珊瑚在息肉和群体水平对当地水流和光照条件的适应。在这个项目中，Sebens博士、合作者和学生将研究水分运动对珊瑚礁的摄食生物学、能量和营养的影响。由于缺乏关于猎物捕获率的信息，对能源、碳和氮收支进行建模的尝试一直受挫，而且通常没有充分考虑流动效应。过去的研究以及关于沉积物摄取和无机养分吸收对能量、碳和氮需求的贡献的新数据将用于构建至少六种珊瑚的能量、碳和氮收支。水流对每个输入和输出过程的影响将纳入该模型预算。该项目将继续测量野外珊瑚周围的小规模水流。为此，研制了具有高空间分辨率的自给式水下流量计。收集的数据将用于描述总体流动状况，提供有关牙买加、佛罗里达、伯利兹和加勒比地区其他地点珊瑚礁流动环境的新信息。这一关于珊瑚流动觅食的新信息将扩展目前的概念模型，以涵盖不同的殖民地形式、触须形态和线囊组成。珊瑚礁线虫摄食浮游动物对于它们的生存是必要的，但大多数研究都集中在它们内共生的虫黄藻对浮游动物的自养贡献。这项研究将增加我们对珊瑚礁环境中能量和营养通量的理解，珊瑚礁环境是最具生产力和濒危的海洋栖息地之一。

9811577SebensCoral reef ecosystems depend on water movement at all levels. Water movement delivers prey to corals and enhances uptake and exchange of nutrients, oxygen, carbon dioxide, bicarbonate and other ions. It also affects coral competition, larval dispersal, fragmentation, activity of predators, and sedimentation, thus having a large potential impact on coral distribution. Flow micro-habitats on reefs differ substantially, even over a few meters or less, causing measurable differences in coral growth rates. The contribution of zooxanthellae (photosynthesis) to coral energetics is most strongly affected by diffusional limitations at the lower extremes of flow, modified by changes in irradiance. Flow at the smallest scale affects the processes of respiration, productivity and suspension feeding by corals, the escape behavior of zooplankton encountering corals, and the ultimate success of particular polyp, tentacle, and colony morphologies. Over an entire reef, there is a characteristic gradient from high velocity oscillatory (wave-induced) flow in shallow reef zones, to unidirectional flows of lower velocity in deep reef and lagoonal habitats. Such flow regimes affect benthic-pelagic fluxes and dispersal of gametes and larvae of reef dwelling species. Corals vary in polyp size, tentacle form and colony structure; coral growth forms in each reef zone reflect adaptations to local flow and light regimes at the polyp and colony levels.In this project Dr. Sebens, collaborators and students will investigate the effects of water movement on the feeding biology, energetics, and nutrition of reef corals. Attempts to model energy, carbon and nitrogen budgets have suffered from a lack of information on prey capture rates and have generally not considered flow effects adequately. Past studies along with new data on the contributions of sediment ingestion and inorganic nutrient uptake to energy, carbon, and nitrogen requirements will be used to construct energy, carbon, and nitrogen budgets for at least six coral species. Effects of water flow on each input and output process will be incorporated into this model budget. The project will continue to measure small scale water flow around corals in the field. Self-contained underwater flowmeters with fine spatial resolution have been constructed for this research. The data collected will be used to characterize the general flow regime, providing new information about the flow environment of coral reefs in Jamaica, Florida, Belize and other sites in the Caribbean. This new information on coral feeding with flow will extend the current conceptual model to encompass a diversity of colony forms, tentacle morphologies, and nematocyst compositions. Zooplankton feeding by coral reef cnidarians is necessary for their survival, yet most studies have focused on the autotrophic contribution from their endosymbiotic zooxanthellae. This research will increase our understanding of energy and nutrient fluxes in coral reef environments, which are among the most productive and endangered marine habitats.