CDOM Effects on Spectral Quality and Phytoplankton Community Composition in North Inlet and Winyah Bay, SC

Chromophoric Dissolved Organic Matter (CDOM) is an optically-active constituent of natural waters that greatly influences the spectral quality of the estuarine light environment. Because CDOM absorbs blue wavelengths of light preferentially, we hypothesized that environments with high concentrations of CDOM will be rich in red light and will have a higher abundance of cryptophytes or other taxa whose pigmentation is complementary to the prevailing spectral regime. We used a 7-channel spectral radiometer to characterize light quality, and used HPLC-CHEMTAX to determine phytoplankton community composition. Results of the spectral quality in a high CDOM environment (Winyah Bay) showed that more overall light was absorbed (high attenuation), violet and blue wavelengths were strongly absorbed, and there was mainly a red underwater light field. In a low CDOM environment (North Inlet), less overall light was absorbed (lower attenuation), violet and blue wavelengths were weakly absorbed, and there was mainly a blue underwater light field. As for phytoplankton community composition, cryptophytes were abundant in the high CDOM environment, whereas the main taxon found in the low CDOM environment was diatoms. In conclusion, we saw our predicted relationship between color of the underwater light field and phytoplankton community composition.