Skeletal Structural Basis of Density Banding in the Reef Coral Montastrea Annularis

Density banding in coral skeletons can provide for reconstruction of the coral\u27s growth en- vironment over long periods. The physical differ- ences between low and high density portions of a skeletal band are not well understood. The skeletal architecture of M. annularis from Southeast Flor- ida, the Florida Keys, St. Croix, the Bahamas, and Mexico was compared in X-ray revealed high den- sity (HD), low density (LD), and stress HD bands. Density changes arose from differences in the size, but not spacing, of exothecal structural elements (horizontal dissepiments and vertical costae). En- dothecal architecture size (e.g., columella, dissepi- ments, septa) was relatively constant between den- sity band types. Results have implications for studies of coral growth, sclerochronology, and iso- topic/trace element composition

Density Banding in the Reef Coral Montastrea Annularis

Abstract. Density banding in coral skeletons can provide for reconstruction of the coral's growth en-. vironment over long periods. The physical differences between low and high density portions of a skeletal band are not well understood. The skeletal architecture of M. annularis from Southeast Florida, the Florida Keys, St. Croix, the Bahamas, and Mexico was compared in X-ray revealed high density (HD), low density (LD), and stress H D bands. Density changes arose from differences in the size, but not spacing, of exothecal structural elements (horizontal dissepiments and vertical costae). Endothecal architecture size (e.g., columella, dissepiments, septa) was relatively constant between density band types. Results have implications for studies of coral growth, sclerochronology, and isotopic/trace element composition

Circadian Clock Gene Expression in the Coral Favia fragum over Diel and Lunar Reproductive Cycles

Natural light cycles synchronize behavioral and physiological cycles over varying time periods in both plants and animals. Many scleractinian corals exhibit diel cycles of polyp expansion and contraction entrained by diel sunlight patterns, and monthly cycles of spawning or planulation that correspond to lunar moonlight cycles. The molecular mechanisms for regulating such cycles are poorly understood. In this study, we identified four molecular clock genes (cry1, cry2, clock and cycle) in the scleractinian coral, Favia fragum, and investigated patterns of gene expression hypothesized to be involved in the corals' diel polyp behavior and lunar reproductive cycles. Using quantitative PCR, we measured fluctuations in expression of these clock genes over both diel and monthly spawning timeframes. Additionally, we assayed gene expression and polyp expansion-contraction behavior in experimental corals in normal light:dark (control) or constant dark treatments. Well-defined and reproducible diel patterns in cry1, cry2, and clock expression were observed in both field-collected and the experimental colonies maintained under control light:dark conditions, but no pattern was observed for cycle. Colonies in the control light:dark treatment also displayed diel rhythms of tentacle expansion and contraction. Experimental colonies in the constant dark treatment lost diel patterns in cry1, cry2, and clock expression and displayed a diminished and less synchronous pattern of tentacle expansion and contraction. We observed no pattern in cry1, cry2, clock, or cycle expression correlated with monthly spawning events suggesting these genes are not involved in the entrainment of reproductive cycles to lunar light cycles in F. fragum. Our results suggest a molecular clock mechanism, potentially similar to that in described in fruit flies, exists within F. fragum

The effects of feeding frequency and symbiosis with zooxanthellae on the biochemical composition of Astrangia Danae Milne Edwards & Haime 1849

The coral Astrangia danae Milne Edwards & Haime 1849 occurs naturally with and without symbiotic algae and thus may have two sources of nourishment: (1) particles captured by the coral polyps, and (2) photosynthetic products translocated from their zooxanthellae. Symbiotic colonies may have both sources, and nonsymbiotic ones certainly have only the former. The relative importance of these two food sources was studied in the laboratory by examining the tissues of corals fed with frozen brine shrimp. Stock corals were fed once per week. Two to three weeks prior to each experiment, selected corals were placed on one of three feeding schedules: starved (S), fed once per week (1/wk), and fed three times per week (3/wk). The coral tissues were analyzed for protein, lipid, carbohydrate, and zooxanthellae content. Increased feeding frequency (1/wk → 3/wk) resulted in an increased tissue biomass and lipid to protein (L/P) ratio; starvation (1/wk → S) caused a decrease in these parameters. Symbiosis with zooxanthellae had an effect similar to increased feeding frequency in that the S and 1/wk symbiotic corals had a higher L/P ratio than comparable nonsymbiotic ones. There were no significant differences in L/P ratios between the 3/wk symbiotic and nonsymbiotic corals. Freshly collected colonies had a tissue composition most similar to the laboratory animals fed 3/wk. This result is consistent with the hypothesis that ingestion of solid food is the major nutritional source for A. danae in Narragansett Bay, Rhode Island, but our experiments suggest that the algae can have an important effect on tissue L/P ratios during times of food scarcity. © 1980

Effects of Drilling Fluids on Reef Corals: A Review

This chapter reviews research on the effects of drilling fluid on reef-building, or hermatypic, corals. Experiments have shown that the burial of corals in drilling fluid, or mud, caused mortality and that certain drilling fluids applied as slurries could not be removed by corals. Under field conditions, however, slurries were removed with the assistance of natural currents, but appeared to cause lowered growth rates in treated specimens. Certain species showed behaviorial stress symptoms after 96-h exposure to 0.100 ml liter-1 of drilling fluid (0.100 ml of fluid in 1 liter of seawater) and exposure to 1.000 ml liter-1 caused mortality in 65 h for three of seven species tested. A chronic 6-week exposure to 0.100 ml liter-1 of drilling fluid caused an 84% decrease in calcification, a 40% decrease in respiration, reductions in gross photosynthesis (26%), nitrate uptake (28%), ammonium uptake (49%), and feeding, as well as some death. Other studies showed that average linear skeletal growth also decreased. A field assessment of a reef, several years after drilling , indicated a 70-90% reduction in foliose, branching, and platelike corals within a 115 m x 85 m ellipse around the drilling site. Detrimental effects on corals, as extrapolated from the limited information on effects, seem probable within a minimum distance of 100m from the source.https://nsuworks.nova.edu/occ_facbooks/1006/thumbnail.jp