Collaborative Research: Hydrodynamic Forcing of Metabolism of Coral Reef Algal Communities (RUI)

木匠9314470 目前解释珊瑚礁如何保持高生物量和极高的总初级生产力的模式是，营养物质和有机物在珊瑚礁内发生紧密循环，导致净自养区与净异养区交替出现。 上游自养群落被认为支持下游异养组合的整体平衡，导致生态系统P/R比接近统一。根据这一模式，珊瑚礁与周围贫营养海洋的耦合并不显著。 最近的研究表明，珊瑚礁可能比目前认为的更依赖于水动力过程。 虽然热带沃茨的营养物浓度很低，但大量的水通过平流穿过珊瑚礁，可能导致大量营养物流入底栖初级生产者。 主要的上游自养区是礁滩，藻类草皮组合是主要的初级生产力负责。以往的研究表明，水流速度对藻坪的初级生产力和固氮速率有显著影响。此外，流量测量的一个珊瑚礁表明，藻类冠层高度显着改变当地的水动力制度，因此，藻类草皮的代谢过程可能是扩散有限的一个显着的时间比例。 本项目将检验珊瑚礁藻类草皮的初级生产率和固氮率受扩散限制的假设。 流动环境的测量礁坪将被用来估计在何种程度上不同的冠层高度的藻类草皮扩散限制。然后，该项目将继续测试有关导致扩散限制的具体因素的假设。 该项目的结果将填补珊瑚礁环境中水流的经验测量以及水流如何影响藻类代谢的空白。 这项研究的结果可能会导致理解珊瑚礁功能的重大范式转变。 证明珊瑚礁是与周围海洋环境密切相关的开放生态系统，将对预测全球气候变化对这些独特生态系统的影响产生重要影响。 ***

Carpenter 9314470 The current paradigm explaining how coral reefs maintain high biomass of organisms and extremely high rates of gross primary productivity is that tight recycling of nutrients and organic matter occurs within the reef resulting in zones of net autotrophy alternating with zones of net heterotrophy. Autotrophic upstream communities are thought to support downstream heterotrophic assemblages with the overall balance resulting in ecosystem P/R ratios near unity. According to this paradigm, coral reefs are not coupled significantly to the surrounding oligotrophic ocean. Recent studies suggest that coral reefs may be much more dependent on hydrodynamic processes than currently believed. Although nutrient concentrations of tropical waters are very low, an enormous volume of water is advected across the reef and could result in a large flux of nutrients to benthic primary producers. The major upstream autotrophic zone is the reef flat where algal turf assemblages are responsible for the majority of primary productivity. Previous work has demonstrated that rates of primary productivity and nitrogen fixation of algal turf are affected significantly by water flow speed. Furthermore, flow measurements on one reef suggest that algal canopy height significantly alters the local hydrodynamic regime and as a result, metabolic processes of algal turfs may be diffusion-limited for a significant proportion of time. This project will test the hypothesis that rates of primary productivity and nitrogen fixation of coral reef algal turfs are diffusion-limited. Measurements of the flow environment on a reef flat will be made and used to estimate the degree to which algal turfs varying in canopy height are diffusion-limited. The project will then move on to test hypotheses about the specific factors that result in diffusion-limitation. The results of this project should fill a gap on empirical measurements of water flow in coral reef environments and how wate r flow affects algal metabolism. The results of this research may lead to a significant paradigm shift in understanding how coral reefs function. Demonstration that reefs are open ecosystems that are strongly coupled to the surrounding ocean environment would have important implications for predictions of the effects of global climate change on these unique ecosystems. ***