The Nature of Detritral Absorption: Relationships Between Particle Types, Chromophore Composition, and Particulate Spectral Absorption

本研究将研究富营养化和贫营养化水域中“碎屑”颗粒对生物光学特性的光吸收变异性的来源。在许多生物光学研究中，已经观察到“碎屑”颗粒物质引起从蓝光到近紫外的吸收显著增加。本研究旨在更好地定义具有不同光学特性的水中主要吸收蓝光到紫外线的颗粒发色团的性质，并确定与这些发色团相关的颗粒（碎屑和生物体）的类型。这些目标将在实验室和实地调查中加以解决。该研究将利用分析方法，在几个层面上考虑碎屑吸收问题：单个颗粒类型的表征（通过与图像分析仪耦合的荧光显微镜）；生色团组成分析；颗粒光谱吸收的测量（总吸收和“分割”）；在现场，还有光学剖面。实验室研究将集中于生物体（特别是异养细菌和原生动物）对“碎屑”吸收的潜在贡献，浮游微动物产生的生物源碎屑的发色团组成，不同生物发色团类型的相对重要性，以及碎屑颗粒中发色团的稳定性。现场工作（在南大西洋湾内）将扩展实验室研究的结果，将浑浊的近岸水域与大陆架断裂以外的贫营养水域进行比较。将评估地聚合物与生物源发色团在碎屑吸收中的作用。这项研究的结果将涉及几个学科，包括生物光学海洋学和海洋光化学。

This study will examine the sources of variability of light absorption by "detrital" particles on bio-optical properties in both eutrophic and oligotrophic waters. In a number of bio-optical studies "detrital" particulate material has been observed to cause a pronounced increase in absorption from the blue into the near- ultraviolet. This study seeks to better define the nature of the dominant blue- to uv-absorbing particulate chromophores in waters with different optical characteristics, and to identify the types of particle (detrital and living organisms) with which such chromophores are associated. These objectives will be addressed in combined laboratory and field investigations. The study will utilize analytical approaches which consider the question of detrital absorption at several levels: characterization of individual particle types (by epifluorescence microscopy coupled to an image analyzer); analyses of chromophore composition; measurements of particulate spectral absorption (total and "partitioned"); and, in the field, optical profiling. Laboratory studies will focus on the potential contribution of living organisms (particularly heterotrophic bacteria and protozoans) to "detrital" absorption, the chromophore composition of biogenic detritus produced by microzooplankton, the relative importance of different biological chromophore types, and the stability of chromophores in detrital particles. Field work (within the South Atlantic Bight) will extend the results of the laboratory study to compare turbid inshore coastal waters with oligotrophic waters beyond the shelf break. The role of geopolymers versus biogenic chromophores in detrital absorption will be assessed. The results of this study will be relevant to several disciplines, including bio-optical oceanography and marine photochemistry.