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

本研究项目的重点是底栖微藻对主要大陆架系统——美国东南部的南大西洋湾（SAB）的总初级生产力的贡献。本文将重点研究当泛光带延伸到陆架的沙质沉积物时，生物地球化学循环在泛光带下部加强的命题。特别是，我们假设，由于砂中的光学环境、高底栖微藻生物量和透水砂表层营养物质的内部循环，光合作用光利用的面效率得到了提高。此外，假设陆架上的底栖生物初级产量可以作为陆架海底辐照水平的函数在区域尺度上进行估计。这项研究建立在先前的一项研究的结果和经验的基础上，该研究表明，广阔的南大陆架的大部分海底经常在光带内。虽然到达陆架海底的光强平均只有表面入射辐照度的4-7%，但微藻可以贡献南大陆架中部陆架地区总初级产量（水柱加底栖生物）的40%左右。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相关的年周期底栖生物初级生产；2)评估陆架光合作用利用的面积效率，重点评估光带的沉积物部分；3)研究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（和高面光合势）的方面。在这项研究中，将采用几种方法来获得底栖生物初级产量作为入射辐照度函数的可靠估计。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方案的联系而扩大。

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.