Temporal and spatial patterns in optical properties of CDOM on Florida&rsquos Gulf Coast: Shelf to Stream to Aquifer

Robyn Nicole Conmy, University of South Florida, rconmy@marine.usf.edu (Presenting)
Paula G Coble, University of South Florida, pcoble@marine.usf.edu

On river-dominated margins, such as the West Florida Shelf on Florida&rsquos Gulf Coast, CDOM distributions are, to the first-order, controlled by mixing of fresh and marine waters. In this region, the underwater light field is also affected by hurricanes and resuspension events, which is linked closely with a number of factors prior to a storm&rsquos passing such as the presence of persistant blooms, rainfall and discharge. Additionally, storm track and wind direction play a significant role in resultant CDOM signatures.

Gulf Coast riversheds (Mississippi River to Everglades System) that supply the shelf exhibit strong seasonality and affects CDOM. A regional dependency also exists, where highest aromaticity and concentration of organic material is found for the southernmost watersheds. Basin characteristics, land use and climatic patterns are implicated in the cause for regional differences. In addition to surface flow, groundwater discharge can introduce organic material to surface waters. For the Tampa Bay region, strong hydrologic links exist between shallow aquifers and the overlying surface waters, resulting in similar CDOM quantity and quality in both reservoirs. Deep aquifers, however are less concentrated and have CDOM signatures more similar to marine waters, suggesting like biogeochemical pathways of the material, including the influence of the aquatic microbial community.

Investigating CDOM distribution and signatures is vital to carbon budget and cycling questions. The amount and quality of organic material has significant implications for ecosystems, thereby affecting organisms that use CDOM as a food source, light availability for photosynthesis, UV shading provided to biota, satellite estimates of chlorophyll, metal binding, materials transport and overall water quality.