Date of Award

5-31-2018

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental Sciences/Environmental, Earth & Ocean Sciences

First Advisor

Zhongping Lee

Second Advisor

Robert F. Chen

Third Advisor

Juanita Urban-Rich

Abstract

This study is dedicated to developing a system to semi-analytically retrieve the absorption coefficients and concentrations of multiple pigments in inland, coastal, and oceanic waters from satellite or in situ ocean/water color measurements. The objectives of this study include: (1) a significant expansion of the estimation of phytoplankton pigments from ocean color remote sensing; (2) a better algorithm for the bloom detection and monitoring; and (3) first maps of spatial distribution of multiple pigments in global oceans.

Phytoplankton are the primary producers in the ocean and play key roles in the Earth’s carbon cycle. Pigments contained in phytoplankton including chlorophyll a, b, c, photoprotective and photosynthetic carotenoids absorb light for photosynthesis and modulate the appearance of water color. Some of the accessory pigments are bio-markers for phytoplankton groups or species discrimination. In the past decades limited by earlier knowledge and understandings, the concentration of chlorophyll a has been the focus of ocean color remote sensing, and the results have been widely used in estimation of phytoplankton biomass, primary production and phytoplankton functional types in the global ocean. However, more and more studies revealed that the concentration of chlorophyll a alone is not a good index for these works, but rather, the bio-optical information of other pigments can provide better estimation for phytoplankton biomass, primary production and phytoplankton functional types. Therefore, the need for the information of other pigments from ocean color data become stronger, but currently there is no model yet which can help reach this goal for phytoplankton study in the global ocean. We thus developed a new system in this work to obtain the absorption coefficients and concentrations of not only chlorophyll a but also other accessory pigments including chlorophyll b, c, phycoerythrin, phycocyanin, and photosynthetic and photo-protective carotenoids (PSC and PPC) from ocean color remote sensing. This new system was applied to hyper- and multi-spectral data from in situ and satellite platforms (HICO, MERIS, and MODIS-Aqua), where the results were validated using pigment absorption and concentration data from water sample measurements. Several analyses including the test of the robustness of the system to different water types and the model performance at different satellite sensors’ spectral configurations were carried out to obtain a thorough understanding of the advantages and limitations of the system, which then provide a guidance for its application to the global oceans. With this innovative ocean color inversion system, for the first time the information of multiple phytoplankton pigments can be obtained from satellite ocean color data. The results can greatly enhance and advance scientific studies of biology and biogeochemistry of the global oceans that were previously not possible when the only available information was the concentration of chlorophyll a.

Comments

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