Collaborative Research: Mass Transfer Due to Oscillatory Flow Over Coral Reefs

珊瑚礁系统的新产量、有机碳循环和营养吸收之间的关系还不是很清楚。实验珊瑚礁群落的营养吸收已被证明是质量转移受限的，或受限于营养物质可实际输送到珊瑚礁自养生物活跃表面的速率。一套简单的传质关系式已经被用来预测溶解的无机营养素的吸收。这些关系式是在10-20m长的水槽中，在恒定、无振荡的条件下进行的试验得出的。阿特金森和莫尼史密斯博士认为，这些质量传递方程不适合于理解浅水珊瑚礁群落在自然珊瑚礁环境中的营养吸收，在自然珊瑚礁环境中，波浪驱动的水运动主导着周围的流场。他们从理论和实验两方面论证了振荡流动对传质有一定的促进作用。他们强调，没有关于波浪和自然粗糙表面的传质研究，这是底栖生态系统研究所独有的问题。该项目有三个总体目标：1)了解海浪如何影响自然粗糙表面的质量传输率；2)确定海浪如何影响适应波浪驱动的流动环境的珊瑚礁群落的营养吸收；3)实际证明波浪提高了天然珊瑚礁群落就地吸收营养的速率。为了实现这些目标，这些科学家提出了一套由两项实验室研究和一项实地研究组成的连锁集合。首先，将在椰子岛的HIMB实验室进行一项关于珊瑚群落在稳定和振荡流动条件下吸收养分的实验室实验。第二，将在斯坦福大学的环境流体力学实验室对珊瑚的应力和质量传递的流体力学进行详细的研究。最后，为了检验实验室结果的应用，将进行一系列的现场实验，以确定在波浪驱动的流动条件下天然珊瑚礁群落的营养吸收速率是否与入射波能呈正相关，并确定这些速率是否与根据实验室实验得出的质量传递关联式估计的底部剪应力成比例。这些实验的结果将给我们提供定量的基础，以确定珊瑚礁群落养分吸收速率的空间变异性，并促进对珊瑚礁群落典型的动态物理环境如何定义其新陈代谢的理解。

The relationship between new production, organic carbon cycling, and nutrientuptake into coral reef systems is not well understood. Nutrient uptake into experimentalcoral reef communities has been shown to be mass-transfer limited, or limited by the rate at which nutrients can be physically delivered to the active surfaces of reef autotrophs. A set of simple, mass transfer relationships have been developed to predict uptake of dissolved inorganic nutrients. These relationships were derived from experiments which were conducted in 10-20 m long flumes and under steady, non-oscillatory flow conditions. Drs. Atkinson and Monismith reason that these mass transfer equations are inappropriate for understanding nutrient uptake by shallow-water reef communities in natural reef environments, where wave-drive water motion dominates the surrounding flow field. They have argued with both theoretical and empirical evidence that there should be some enhancement of mass transfer due to oscillatory flow. They emphasize that there are no mass transfer studies with both waves and naturally rough surfaces and that this is a problem unique to the study of benthic ecosystems. The project has three general goals: 1) To understand how waves influence rates of mass transfer to naturally roughsurfaces; 2) To determine how waves influence nutrient uptake into reef communitiesadapted to wave-driven flow environments; 3) To actually demonstrate that waves enhance in situ rates of nutrient uptakeby natural reef communities.To achieve these goals, these scientists propose an interlocking set of two lab studies and one field study. The first of these, a laboratory experiment on nutrient uptake by a coral community under both steady and oscillating flow conditions, will be conducted at the HIMB lab on Coconut Island. The second, a detailed study of the fluid mechanics ofstress and mass transfer over corals will be carried out at the Environmental FluidMechanics Laboratory at Stanford. Finally, to test the application of the lab results, aseries of field experiments will be carried out to determine whether rates of nutrientuptake by natural reef communities under wave-driven flow conditions are positivelycorrelated with incident wave energy, and, to determine whether these rates scale withestimates of bottom shear stress according to mass transfer correlations derived fromlaboratory experiments. Results of these experiments will give us the quantitative basis to determine thespatial variability in rates of nutrient uptake into reef communities, and to promote anunderstanding of how the dynamic physical environment typical of reef communitiesmay be defining their metabolism.