Durant, Daisy

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    Biological responses of two Caribbean reef-building corals to a pier-generated irradiance gradient
    (2006) Durant, Daisy; Weil, Ernesto F.; College of Arts and Sciences - Sciences; Williams, Lucy B.; Armstrong, Roy A.; Vicente, Vance P.; Yoshioka, Paul M.; Aponte, Nilda; Department of Marine Sciences; Bird-Picó, Fernando J.
    Irradiance, sedimentation, and water temperature were studied in a gradient of increased shading when moving towards a pier to determine if changes in these parameters might influence biological characteristics of Siderastrea siderea, and Diploria clivosa. Forty-six colonies of S. siderea were transplanted to four treatment zones: 0 m-under the pier (N=12), 3 m (N=12), 10 m (N=10), and 50 mcontrol zone (N=12). Eleven controls were randomly selected in the 50 m zone. Nine colonies of D. clivosa were studied in the 0 m (N=5) and 50 m (N=4) zone. Irradiance, sedimentation, and hours of shading were measured in all zones; water temperature was monitored in the 0 and 50 m zones. To determine skeletal extension, density, and calcification, S. siderea was stained once with alizarin red and sampled after 16 months. The difference in tissue surface area at the beginning and end of the study was used to determine tissue growth rates of S. siderea. Zooxanthellae densities, mesenterial fecundity, and oocyte diameter were determined for both species using histological techniques. Recruit (2-40 mm) density of S. siderea was assessed by counting recruits along a 50 m transect parallel to the pier at each zone, and monitored for survival from 2000-2002. Irradiance in the 0 and 3 m was significantly lower than the other zones (p<0.001-ANOVA). Hours of shading was significantly higher in the 0 and 3 m (p=<0.001-ANOVA), but similar in the 10 and 50 m zones (p>0.05-Tukey). For S. siderea, tissue growth and calcification in the 0 m zone were significantly lower (p<0.001-ANOVA) than other zones. In the 0 and 3 m zones, skeletal extension and mesenterial fecundity were significantly lower (p<0.001-ANOVA), but oocyte diameter was significantly larger (p<0.001-ANOVA) than the other zones. Significant (p<0.001) positive correlation were found between irradiance and tissue growth (r=0.50), calcification (r=0.50), skeletal extension (r=0.60), and mesenterial fecundity (r=0.70), oocyte diameter correlated negatively (r=-0.44/p=0.0001). Juvenile density was significantly lower in the 0 and 3 m zones than the other zones, decreasing gradually during the study (p<0.0001-ANOVA). For D. clivosa, zooxanthellae densities significantly increased while mesenterial fecundity significantly decreased in the 0 m zone (p<0.05-ANOVA).