Dataset: BW MBRSCorals - OA Experiments

In July 2011, eighteen colonies of the tropical coral S. siderea were collected at 3 to 5 m depth on the Mesoamerican Barrier Reef System in southern Belize. Colonies were collected from nearshore, backreef, and forereef reef zones. Siderastrea siderea corals were transported to the University of North Carolina at Chapel Hill and each coral colony was sectioned into 18 comparatively sized specimens (approximately 3 cm x 2 cm x 1 cm) using a rock saw and glued with cyanoacrylate on to plastic microscope slides.  The corals were allowed to recover for approximately 30 days under laboratory conditions in two 500 L recirculating artificial seawater systems until the start of the 15-day acclimation period, in which the corals were incrementally exposed to the experimental treatment conditions.

In the laboratory experiments, Siderastrea siderea coral specimens from each of the 18 colonies were reared for 95 days (5 August − 8 November 2011) in each of twelve 38 L glass aquaria (18 specimens per tank; 216 specimens in total) filled with artificial seawater formulated at a salinity of 35 with Instant Ocean Sea Salt and deionized water. Four pCO2 partial pressures [324, 477, 604, and 2553) ppm)], established by mixing pure CO2 with compressed air using Aalborg mass flow controllers, were bubbled with microporous ceramic airstones into the triplicate glass aquaria (12 tanks total).  Coral specimens from each of the 18 colonies were reared in each of the 12 replicate tanks.  The pCO2 experiments were maintained at an average temperature of 28 ºC.

Experimental growth conditions for the seawater temperature experiment were similar to those for the CO2-induced ocean acidification experiment described above.  Siderastrea siderea coral specimens from each of the 18 colonies were reared for 95 days (5 August − 8 November 2011) in each of nine 38 L glass aquaria (18 specimens per tank; 162 specimens in total) filled with artificial seawater formulated at a salinity of 35 with Instant Ocean Sea Salt and deionized water. Three experimental seawater temperatures [25, 28, and 32 ºC] were maintained in triplicate (9 tanks total) for this experiment. Coral specimens from each of the 18 colonies were reared in each of the 9 replicate tanks.  Compressed air with an average pCO2 of 488 ppm was bubbled with microporous ceramic airstones into the triplicate glass aquaria.

Coral calcification rates were estimated using a buoyant weight technique.  Siderastrea siderea specimens were weighed at the beginning of the experiment and a final measurement taken at approximately 95 days. Each coral specimen was suspended by aluminum wire at 10-cm depth from a Cole-Parmer bottom-loading scale (precision ± 0.001; accuracy ± 0.002) in an aquarium filled with artificial seawater maintained at a temperature of 25 ºC and salinity of 33. A standardized plastic-coated zinc mass was intermittently weighed to ensure consistency of the buoyant weight method throughout the duration of the experiment.