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Methods to Estimate Solar Radiation Dosimetry in Coral Reefs Using Remote Sensed, Modeled, and in Situ Data.
Citation:
BARRON, M. G., D. VIVIAN, S. H. YEE, AND D. L. SANTAVY. Methods to Estimate Solar Radiation Dosimetry in Coral Reefs Using Remote Sensed, Modeled, and in Situ Data. ENVIRONMENTAL MONITORING AND ASSESSMENT. Springer, New York, NY, 151(1-4):445-455, (2009).
Impact/Purpose:
Measuring solar radiation exposure within coral reefs using remote sensed, modeled, and in situ data to determine amount of coral bleaching.
Description:
Solar irradiance has been increasingly recognized as an important determinant of bleaching in coral reefs, but measurements of solar radiation exposure within coral reefs have been relatively limited. Solar irradiance and diffuse down welling attenuation coefficients (Kd, m-1) were determined in coral reef areas of South Florida during a minor bleaching event during August 2005. Solar radiation dosimetry within multiple coral reef areas was assessed using remote sensed, modeled, and measured values. Coral reefs in the Dry Tortugas and upper Keys had similar Kd values, whereas Kd values were significantly greater in the middle and lower Keys (ANOVA, Region, F=9.80, p<0.001). Mean one percent attenuation depths varied by reef region for ultraviolet B (UVB; 9.7 to 20 m), ultraviolet A (UVA; 22 to 40 m) and visible (27 to 43 m) solar radiation, with larger variation between specific reef locations for UVB (2.5 to 31 m), UVA (5.5 to 50 m) and visible light (8.5 to 98 m) attenuation. Solar irradiances determined from remote sensed data were significantly correlated (R2=0.32, p<0.001) with measured values, but were generally over estimated at the depth of corals. There was no evidence of a significant albedo effect on remote sensed solar irradiances based on comparison of measured and predicted values with coral depth (R2=0.07, p=0.275). Solar irradiances modeled using an atmospheric radiative transfer model parameterized with site specific approximations of cloud cover showed close agreement with measured values (R2>0.75, p<0.001). Estimated daily doses (W*hr/m2) of UVB (0.01-19), UVA (2-360) and visible (29-1653) solar radiation varied with coral depth (2 to 24 m) and meteorological conditions. These results indicate large variation in solar radiation dosimetry within coral reefs that may be estimated with reasonable accuracy using regional Kd measurements and radiative transfer modeling.