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Shank G.C.,University of Texas at Austin | Lee R.,U.S. Environmental Protection Agency | Vahatalo A.,U.S. Environmental Protection Agency | Zepp R.G.,U.S. Environmental Protection Agency | Bartels E.,Tropical Research Laboratory
Marine Chemistry | Year: 2010

Chromophoric dissolved organic matter (CDOM) strongly absorbs solar radiation in the blue-green and serves as the primary attenuator of water column ultraviolet radiation (UV-R). CDOM interferes with remote sensing of ocean chlorophyll and can control UV-R-induced damage to light-sensitive organisms including corals. We used laboratory incubations to evaluate CDOM production from senescing Rhizophora mangle (red mangrove) leaf litter (yellow, orange, and brown) and floating Sargassum colonies. Mangroves exist at the land-ocean interface near coral reefs in sub-tropical and tropical regions while floating Sargassum colonies tend to congregate in sub-tropical ocean gyres. CDOM production (∼ 48 h) from mangrove leaves collected during a dry period in June 2004 (0.17 ± 0.11 m- 1 g- 1 l h- 1) was lower than production from leaves collected during a wet period in September 2003 (0.57 ± 0.42 m- 1 g- 1 l h- 1) suggesting that CDOM production from leaf litter fluctuates in response to environmental factors. CDOM production was greatest for the mid-senescence orange leaves and lowest for the severely senesced brown leaves in both experiments. Along the sub-tropical Florida Keys coral reef ecosystem, the primary source of CDOM is discharge from the shallow seagrass-dominated Florida Bay as evidenced by a strong correlation between field CDOM measurements and previously reported Florida Bay discharge volumes. However, field observations provide evidence that large expanses of red mangroves throughout the Keys could be important CDOM sources to the region's coral reefs during periods of reduced Florida Bay discharge. Floating Sargassum colonies also readily produced CDOM in laboratory incubations, but at much more variable rates than mangrove leaves. However, our calculations indicate that large mats of floating Sargassum could provide important CDOM quantities to oligotrophic oceanic waters including the Gulf of Mexico and North Atlantic. © 2010 Elsevier B.V. Source


Shank G.C.,University of Texas at Austin | Zepp R.G.,U.S. Environmental Protection Agency | Vahatalo A.,U.S. Environmental Protection Agency | Lee R.,U.S. Environmental Protection Agency | Bartels E.,Tropical Research Laboratory
Marine Chemistry | Year: 2010

We examined the photoreactivity of chromophoric dissolved organic matter (CDOM) derived from Rhizophora mangle (red mangrove) leaf litter and floating Sargassum colonies as these marine plants can be important contributors to coastal and open ocean CDOM pools, respectively. Mangrove and Sargassum CDOM readily degraded when exposed to simulated solar irradiance (CPS SunTest solar simulator exposures). CDOM produced from brown mangrove leaves (representative of substantial senescence) exhibited shorter photobleaching half-lives (a305 t1/2 < 50 h) than CDOM produced from yellow and orange (early and mid senescence) leaves (a305 t1/2 ∼ 60-90 h). Mangrove CDOM photobleaching rates were higher in the mid-UVA (a350) than in the UVB (a305) spectral region. Photobleaching half-lives of Sargassum CDOM were mostly < 40 h and more consistent across UVB (a305) and UVA (a350) wavelengths. Sargassum CDOM photomineralized during simulated solar irradiation producing DIC at rates exceeding 2500 nmol m l- 1 h- 1, indicating that regions of the surface ocean with large concentrations of this plant may provide a strong CO2 source to the atmosphere. Sargassum CDOM photoreactions also produced CO more efficiently than terrestrial CDOM and much more efficiently than ambient CDOM in the open ocean. Thus, biological production of CDOM may be the rate-limiting step for photoproduction of DIC from Sargassum and other sources in the open ocean. An examination of CDOM photobleaching in Florida Keys coastal waters indicates that one month of summertime solar radiation may substantially increase UVB and UVA exposure to corals in shallow waters (< 4 m), especially along the offshore reef tract. But, our results also indicate that when ambient CDOM levels are high, the corals are well-buffered against increases in ultraviolet radiation (UV-R) exposure even after periods of extended CDOM photobleaching. © 2010 Elsevier B.V. Source


Barnes B.B.,University of South Florida | Hallock P.,University of South Florida | Hu C.,University of South Florida | Muller-Karger F.,University of South Florida | And 3 more authors.
Coral Reefs | Year: 2015

Shallow water tropical coral reefs may bleach due to extremes in a variety of environmental factors. Of particular concern have been temperature, ultraviolet radiation, and photosynthetically available radiation. Satellite observation systems allow synoptic-scale monitoring of coral environments that can be used to investigate the effects of such environmental parameters. Recent advancements in algorithm development for new satellite data products have made it possible to include light availability in such monitoring. Long-term satellite data (2000–2013), in combination with in situ bleaching surveys (N = 3,334; spanning 2003–2012), were used to identify the environmental factors contributing to bleaching of Florida reef tract corals. Stepwise multiple linear regression supports the conclusion that elevated sea surface temperature (SST; partial Radj 2 = 0.13; p < 0.001) and high visible light levels reaching the benthos (partial Radj 2 = 0.06; p < 0.001) each independently contributed to coral bleaching. The effect of SST was modulated by significant interactions with wind speed (partial Radj 2 = 0.03; p < 0.001) and ultraviolet benthic available light (partial Radj 2 = 0.01; p = 0.022). These relationships were combined via canonical analysis of principal coordinates to create a predictive model of coral reef bleaching for the region. This model predicted ‘severe bleaching’ and ‘no bleaching’ conditions with 69 and 57 % classification success, respectively. This was approximately 2.5 times greater than that predicted by chance and shows improvement over similar models created using only temperature data. The results enhance the understanding of the factors contributing to coral bleaching and allow for weekly assessment of historical and current bleaching stress. © 2015, Springer-Verlag Berlin Heidelberg. Source


Goodbody-Gringley G.,Harvard University | Goodbody-Gringley G.,Tropical Research Laboratory | Vollmer S.V.,Northeastern University | Woollacott R.M.,Harvard University | Giribet G.,Harvard University
Marine Biology | Year: 2010

Understanding population connectivity in corals is particularly important as these organisms are increasingly threatened by abiotic and biotic factors. This study examined the population genetic structure of the brooding coral Favia fragum across four locations in the Caribbean and Western Atlantic using mitochondrial and nuclear markers. Morphological features were also compared to test whether genetic diversity corresponds with skeletal morphology. When comparing across distantly related Caribbean and Bermudian locations, FST values were high and significant, indicating strong genetic structure. At a local scale, significant genetic structure was found among reefs in Panama, while no genetic structure was found among reefs within Barbados, Bermuda or Jamaica. Surprisingly, a single haplotype for each of the three markers examined was found in Bermuda, where samples varied significantly from all other locations in three out of four morphological features analyzed. These data indicate that gene flow of F. fragum may occur locally among reefs but is highly restricted at distant locations. Furthermore, isolated populations, such as that of Bermuda, must be self-seeding to maintain the observed genetic uniformity. © 2010 Springer-Verlag. Source

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