Development and Field Testing of a Spectral Radiometer for Measurements in Extremely Low-Light Marine Environments

海洋中的弱光条件对海洋动物的生活具有至关重要的意义，这是由于与动物视觉、通信、繁殖、捕食、反捕食策略和水柱内垂直迁移相关的各种光依赖性生理机制和行为模式。因此，弱光环境对海洋栖息地、水质和商业渔业生产具有多重影响。用现有的常规仪器无法测量极低光的海洋环境，包括海洋表层的黄昏（日落和日出）条件以及从大约200米到1 000米深度的较深层内非常昏暗的日光。因此，这种测量非常稀少，范围也非常有限。在这个项目中开发的仪器称为LARS（低光水生辐射计系统），将具有无与伦比的精确测量极低光的能力，这将为改善深海光和海洋中黄昏条件的表征铺平道路，而不仅仅是过于简化的历史描述。这一文书将有助于扩大对深海生境的研究，以保护这些地球上体积最大的生态系统的生物多样性和完整性，这是国际科学家和政策制定者共同认可的一个重要目标。拟议的LARS发展将基于最先进的高灵敏度光子计数技术，该技术将允许测量10 - 1000 nm的极低水平的水下光谱辐照度。在可见光谱范围内，20光子/（cm 2 s nm）。这将使海洋中层深度（~200-1000 m）的昏暗日光不仅能够测量蓝光，而且还首次测量非弹性辐射过程（例如水分子的拉曼散射）在深度局部产生的潜在生物学显着水平的绿色和红色光。此外，LARS将提供在弱光海洋环境中测量向下和向上辐照度的能力，这是以前从未做过的。将收集实地示范数据，以全面描述深海光场的特征，并为非弹性过程的作用提供第一个实验证据，并接近深度渐近光状态。还将演示对海洋表面层中特征不佳的曙暮光和月光条件的测量。LARS的更广泛的用途将通过数据分析来证明，以支持与弱光海洋栖息地有关的特定生物问题的研究。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Low-light conditions in the ocean have critical significance in the lives of marine animals due to various light-dependent physiological mechanisms and behavioral patterns associated with animal vision, communication, reproduction, predation, antipredator tactics, and vertical migration within the water column. Therefore, low-light environments have multiple implications for oceanic habitats, water quality, and commercial fisheries production. Measurements of extremely low-light marine environments including twilight (sunset and sunrise) conditions in the surface ocean layer as well as very dim solar daylight within deeper layers extending from about 200 to 1000 m depth are not possible with existing conventional instruments. As a result, such measurements have been very scarce and greatly limited in scope. The instrument to be developed in this project, called LARS (Low-light Aquatic Radiometer System), will have an unparalleled capability to accurately measure extremely low light, which will pave the way to improved characterization of deep-sea light and twilight conditions in the ocean beyond oversimplifying historical descriptions. This instrument will aid in expanding research of deep-sea habitats to protect the biodiversity and integrity of these largest ecosystems by volume on Earth, an important goal recognized by international community of scientists and policy-makers.The proposed development of LARS will be based on state-of-the-art highly sensitive photon counting technology which will allow measurements of extremely low levels of underwater spectral irradiance of 10 - 20 photons/(cm2 s nm) within the visible spectral range. This will enable measurements of dim daylight at ocean mesopelagic depths (~200-1000 m) not only of blue light but also, for the first time, potentially biologically significant levels of green and red light generated locally at depth by inelastic radiative processes such as Raman scattering by water molecules. In addition, LARS will provide the capability to measure both the downward and upward irradiances in low-light marine environments, which has never been done before. Field demonstrative data will be collected to comprehensively characterize the deep-sea light field and provide first experimental evidence for the role of inelastic processes and approach to the asymptotic light regime at depth. The measurements of poorly characterized twilight and moonlight conditions in the ocean surface layer will be also demonstrated. The broader utility of LARS will be demonstrated by data analysis in support of the study of specific biological questions related to low-light marine habitats.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.