Benthic Primary Production on the South Atlantic Bight Continental Shelf -- Areal Efficiency of Light Utilization and Biogeochemical Significance

该研究计划的重点是底栖微藻对美国东南部南大西洋湾（SAB）的主要大陆架系统的总初级生产力的贡献。这项工作的重点是这样一个命题，即当真光层延伸到陆架的砂沉积物时，真光层下部的地球化学循环会加强。特别是，据推测，光合作用的光利用率的面积效率提高的结果，在沙子中的光学环境，高底栖微藻生物量，和内部循环的营养物质的表层内的渗透性的沙子。此外，据推测，大陆架上的区域底栖生物初级生产量可以在区域尺度上作为大陆架海底辐照度的函数来估计。这项研究是在先前一项研究的结果和经验的基础上进行的，这项研究表明，广阔的SAB大陆架的大部分海底往往在透光层内。而且，虽然到达陆架海底的光强度平均只有约4-7%的表面入射辐照度，微藻可以贡献约40%的总初级生产力（水柱加底栖生物）在SAB的中陆架区域。为了解决上述假设，本研究将：1）确定与区域环境和生物光学变化有关的年周期内底栖生物初级生产力：2）评估陆架光合作用的面积利用效率，重点是真光层沉积物部分; 3）调查底栖硅藻生理生态学的关键方面，特别是那些可能有助于维持陆架沉积物中高底栖微藻生物量（和高面积光合潜力）的生物。在这项研究中，将采用几种方法来获得对作为入射辐照度函数的海底初级生产力的可靠估计。拟议研究的生物地球化学和海洋学范围将通过与目前正在进行的其他区域实地项目的联合来扩大。

This research program focuses on the contribution of benthic microalgae to the total primaryproductivity of a major continental shelf system, the South Atlantic Bight (SAB) off the southeastern United States. The work will focus on the proposition that biogeochemical cycling is intensified in the lower portion of the euphotic zone when the euphotic zone extends to the sand sediments of the shelf. In particular, it is hypothesized that the areal efficiency of light utilization for photosynthesis is enhanced as a result of the optical environment in the sands, high benthic microalgal biomass, and the internal cycling of nutrients within the surface layer of the permeable sands. Further, it is hypothesized that areal benthic primary production on the shelf may be estimated on a regional scale as a function of irradiance levels at the shelf sea floor. The study builds upon the results and experience obtained in a prior study that suggested that most of the sea floor of the broad SAB shelf is often within the euphotic zone. And, although the light intensity reaching the shelf sea floor averaged only some 4-7% of surface incident irradiance, microalgae could contribute about 40% of the total primary production (water column plus benthic) over the mid-shelf region of the SAB. To address the hypotheses stated above, the study will: 1) determine benthic primary productionover the annual cycle in relation to regional environmental and bio-optical variability; 2) evaluate the areal efficiency of utilization for photosynthesis on the shelf, emphasizing on the sediment portion of the euphotic zone; 3) investigate key aspects of the physiological ecology of benthic diatoms, particularly those that could contribute to the maintenance of high benthic microalgal biomass (and high areal photosynthetic potential) in the shelf sediments. In the study, several approaches will be employed to obtain a robust estimate of benthic primary production as a function of incident irradiance. The biogeochemical and oceanographic scope of the proposed study will be expanded through association with other regional field programs currently in process.