Factors Affecting Ultraviolet Exposure in Coastal Waters of the Florida Keys: Effects on Nearshore and Offshore Coral Reef Tracts
Abstract
We have investigated how the loss of chromophoric dissolved organic matter (CDOM)
in the water column due to photobleaching allows for increased penetration of UV radiation
near coral reefs in the Florida Keys. Extended exposure to UV may contribute to coral
bleaching episodes. CDOM serves as the primary control on UV exposure of corals in
this region because it strongly absorbs UV radiation, especially damaging UVB wavelengths.
An important fraction of the CDOM pool in Florida Keys coastal waters is transported
from Florida Bay, but local CDOM sources including seagrasses, mangroves, and Sargassum
colonies may also be substantial. CDOM samples collected along transects near the
reefs and from mangrove leaf and Sargassum incubation experiments were exposed to
simulated solar radiation for up to 120 hours. Calculated photobleaching rates (k305)
of CDOM produced by mangrove leaf litter and Sargassum colonies (approx. 0.02 hr^-1)
were an order of magnitude greater than rates measured for the water column samples
(0.002 hr^-1). However, our experiments indicate that photobleaching of CDOM in natural
waters near the reefs can still be substantial during summer months and may allow
UVB levels at 4 m depth (typical depth of fringing reefs) to increase by as much as
20%. Corals located in shallower waters (2 m) along the reef line may experience up
to a 40% increase in UVB exposure due to loss of CDOM.
Type
Master's projectPermalink
https://hdl.handle.net/10161/372Citation
Rosenfeld, Carla (2007). Factors Affecting Ultraviolet Exposure in Coastal Waters of the Florida Keys: Effects
on Nearshore and Offshore Coral Reef Tracts. Master's project, Duke University. Retrieved from https://hdl.handle.net/10161/372.Collections
More Info
Show full item record
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.
Rights for Collection: Nicholas School of the Environment
Works are deposited here by their authors, and represent their research and opinions, not that of Duke University. Some materials and descriptions may include offensive content. More info