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，因为海洋动物的视觉、交流、繁殖、捕食、反捕食策略和垂直迁移等各种依赖光的生理机制和行为模式都与海洋动物的视觉、交流、繁殖、捕食、反捕食和垂直迁移有关。因此，低光环境对海洋栖息地、水质和商业渔业生产具有多重影响。现有的常规仪器无法测量极弱光的海洋环境，包括海洋表层的黄昏（日落和日出）情况，以及从约200米至1000米深度的深层非常暗淡的日光。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，这将为改进深海光和海洋黄昏条件的表征铺平道路，而不是过于简化的历史描述。该仪器将有助于扩大对深海栖息地的研究，以保护地球上这些体积最大的生态系统的生物多样性和完整性，这是国际科学家和决策者认识到的一个重要目标。LARS的拟议发展将基于最先进的高灵敏度光子计数技术，该技术将允许在可见光谱范围内测量极低水平的水下光谱辐照度，即10 - 20光子/(cm2 s nm)。这将使测量海洋中远洋深度（~200-1000米）的昏暗日光成为可能，不仅可以测量蓝光，还可以首次测量由水分子拉曼散射等非弹性辐射过程在深度局部产生的具有潜在生物学意义的绿光和红光。此外，LARS将提供在低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。将收集现场演示数据，以全面表征深海光场，并为非弹性过程的作用和深度渐近光状态的方法提供第一个实验证据。还将演示对海洋表层的黄昏和月光条件的测量结果。数据分析将证明LARS的更广泛用途，以支持与低光海洋生境有关的具体生物学问题的研究。该奖项反映了美国国家科学基金会的法定使命，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.