Date of Award

Spring 2026

Document Type

Open Access Thesis

Department

Biological Sciences

First Advisor

James L. Pinckney

Abstract

Estuarine systems present complex light environments due to large amounts of colored dissolved organic matter (CDOM) and turbidity that absorb and scatter light, respectively. Optical properties influence phytoplankton communities because their photosynthetic efficiency depends greatly on light availability. This study examined the optical properties of the Winyah Bay estuary in South Carolina using mixing diagrams and related these factors to phytoplankton biomass and community composition across the salinity gradient. Results showed that the behavior of optical properties and their relationship to chlorophyll-a (chl-a) changed under various environmental conditions, particularly river discharge and flushing time. While chl-a was correlated with salinity on most sampling dates, June chl-a was correlated with CDOM and turbidity. Additionally, the phytoplankton community showed a gradient along the estuary with diatoms highly associated with marine, low-CDOM waters whereas cryptophytes and green algae were associated with fresher, high-CDOM waters. These results have implications for remote sensing of phytoplankton biomass as algorithms should not rely on fixed CDOM correction factors to estimate biomass across varying environmental conditions in estuarine waters. Overall, these findings improve understanding of how optical properties fluctuate in estuaries and how environmental changes influence phytoplankton, which are foundational species in the estuarine food web.

Rights

© 2026, Camille Jolicoeur Michaud

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