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

这项研究计划侧重于底栖微藻对美国东南部主要大陆架系统--南大西洋海湾(SAB)初级生产力的贡献。这项工作将侧重于这样一个命题，即当真光带延伸到陆架的砂质沉积物时，真光带下部的生物地球化学循环加剧。特别是，由于沙地的光学环境、高的底栖微藻生物量以及渗透性沙地表层营养物质的内部循环，人们假设光合作用的面积利用效率得到了提高。此外，还假设大陆架上的面积底栖初级生产量可以作为大陆架海底辐照度的函数在区域范围内进行估计。这项研究建立在先前一项研究的结果和经验的基础上，该研究表明，宽阔的珊瑚礁大陆架的大部分海底往往位于真光带内。而且，尽管到达陆架海底的光强平均只有表面入射照度的4%-7%，但微藻可以贡献SAB中陆架区域初级生产力(水柱和底栖生物)的40%左右。为了解决上述假设，该研究将：1)确定与区域环境和生物光学变异性有关的年度周期的底栖初级生产力；2)评估大陆架光合作用利用的面积效率，重点是真光层的沉积物部分；3)调查底栖硅藻生理生态的关键方面，特别是可有助于维持大陆架沉积物中高底栖微藻生物量(和高面积光合作用潜力)的那些方面。在这项研究中，将采用几种方法来获得作为入射辐照度函数的海底初级生产力的稳健估计。将通过与目前正在进行的其他区域实地方案相结合，扩大拟议研究的生物地球化学和海洋学范围。

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.