The Optical Properties of Florida Bay: Impacts for seagrass productivity

Meredith McPherson, Old Dominion University, mmcph005@gmial.com
Victoria Hill, Old Dominion University, vhill@odu.edu (Presenting)
Richard Zimmerman, Old Dominion University, rzimmerm@odu.edu
Heidi Dierssen, University of Connecticut, heidi.dierssen@uconn.edu

This project studied the relationship between seagrass productivity and water column optical properties in Florida Bay. The region adjacent to the Everglades National Park encompassed areas of high seagrass density close to the Keys, with little seagrass further north towards Cape Sable. The vertical attenuation coefficient KPAR was low in the south and increased towards Cape Sable. Approximately 86% of variance in KPAR was explained by absorption. Along the Keys, phytoplankton contributed 9% to total absorption compared to 84% by colored dissolved organic material. The average cosine of the submarine light field was 0.7 to 0.9 in the south. Towards Cape Sable values decreased to 0.6 due to higher suspended material, indicating a more diffuse light field. Seagrasses were excluded from high turbidity areas where incident irradiance reaching the plants was less than 10% of surface irradiance. Although eutrophication may have contributed to historic die-offs of seagrasses in Florida Bay, high suspended sediment loads currently prevent sufficient light from reaching the seabed. Therefore, nutrient load reductions may be necessary, but insufficient to promote seagrass growth in North Florida Bay.