Dataset: MarBio. 2016: calcification and biomass
Deployment: MCR_Edmunds

Calcifying cnidarians were collected from the back reef (~ 4 m depth) on the north shore of Moorea, French Polynesia, during January and April 2011. Fragments of Acropora pulchra, Pocillopora meandrina, massive Porites spp. (15% P. lobata and 85% P. lutea [Edmunds 2009]), and Millepora platyphylla were used to evaluate the effect of pCO2 and temperature on calcification. Massive Porites spp. and M. platyphylla were sampled using a pneumatic drill (McMaster-Carr, part #27755A17) fitted with a 4.1 cm diamond tip hole saw (McMaster-Carr, part #6930A43). The hole saw was used to remove cores ~ 4 cm diameter and ~ 3.8 cm long from adult colonies, and the holes were filled with non-toxic modeling clay (Van Aken Part #10117). To increase the likelihood that cores were genetically distinct, one core was taken from each colony, with sampled colonies distributed over 3 km of reef.

Freshly collected cores were placed in bags filled with seawater and transported to the Richard B. Gump South Pacific Research Station where they were immersed in tanks supplied with a constant flow of seawater from Cook’s Bay. Cores were prepared by removing excess skeleton extending > 1.5 cm below the living tissue, and attaching the cores to numbered polyvinyl chloride (PVC) pipes (4.4 cm diameter and 2.0 cm long) with epoxy (Z Spar, #A788). To eliminate the possibility of fouling organisms accessing freshly cut skeleton, bare skeleton was covered in epoxy. A plastic screw was epoxied to the bottom of each core that was later used to attach them upright in racks placed in the tanks used for incubations. Following preparation, cores were returned to ~ 4 m depth in the back reef, where they were left to recover for 6 weeks. Recovery was evaluated from the presence of healthy c 124 oral tissue covering the formerly damaged edge of the skeleton.

Single branches of A. pulchra and P. meandrina were cut from colonies using bone shears, with each colony sampled once. Sampled colonies were ~ 10 m apart to increase the likelihood that they were genetically distinct. Branches were transported to the Richard B. Gump South Pacific Research Station where they were immersed in flowing seawater. Similar to the methods used for coral cores, branches of A. pulchra and P. meandrina were attached using epoxy to pieces of PVC pipe to make nubbins (Birkeland 1976). Care was taken to cover freshly fractured skeleton with epoxy, and to avoid damaging coral tissue during preparation. A plastic screw was attached to the base of the nubbins and used to hold them upright in plastic racks. Prior to beginning the treatments, coral cores and nubbins were placed in 150 L tanks under ambient conditions of 28.0°C, 370 micro-atm pCO2 and where illuminated with 400 W metal halide lamps (True 10,000K Hamilton Technology, Gardena, CA to an irradiance of ~ 600 micro-mol quanta m2 s-1 (measured with a 4p LI-193 quantum sensor and a LiCor LI-1400 meter) for 5 d to recover from the preparation procedure. The sampling method limited tissue damage to A. pulchra and P. meandrina, and therefore a shorter acclimation period was needed in comparison to massive Porites spp. and M. platyphylla.

Experimental conditions and maintenance

Treatments were created in 8 tanks (Aqua Logic, San Diego), each holding 150 L of seawater and regulated independently for temperature, light, and pCO2. Tanks were operated as closed146 circuit systems with filtered seawater (50 micro-m) from Cook’s Bay, with circulation provided by a pump (Rio 8HF, 2,082 L h-1). Light was supplied 147 by 400 W metal halide lamps (True 10,000K Hamilton Technology, Gardena, CA) at ~ 560 micro-mol quanta m-2s-1 (measured with a 4p LI-193 quantum sensor and a LiCor LI-1400 meter) in the range of photosynthetically active radiation (PAR, 400-700 nm). Lights were operated on a 12hr light-12hr dark photoperiod, beginning at 06:00 hrs and ending at 18:00 hrs. Temperatures were maintained at 28.0°C, which corresponded to the ambient seawater temperature in the back reef when the study was conducted, and 30.1°C which is close to the maximum temperature in this habitat (Putnam and Edmunds 2011). pCO2 treatments contrasted ambient conditions (~ 408 micro-atm) and 913 micro-atm pCO2, with the elevated value expected to occur within 100 y under the "stabilization without overshoot" representative concentration pathway (RCP 6.0) (van Vuuren et al. 2011). pCO2 treatments were created by bubbling ambient air or a mixture of ambient air and pure CO2 that was blended continually and monitored using an infrared gas analyzer (IRGA model S151, Qubit Systems). A solenoid-controlled, gas regulation system (Model A352, Qubit Systems, Ontario, Canada) regulated the flow of CO2 and air, with pCO2 logged on a PC running LabPro software (Vemier Software and Technology). Ambient air and the elevated pCO2 mixture were supplied at ~ 10-15 L min-1 to treatment tanks using pumps (Gast pump DOA-P704-AA, see Edmunds 2011).

The temperatures and pCO2 levels created four treatments with two tanks treatment-1: ambient temperature-ambient pCO2 (AT-ACO2), ambient temperature-high pCO2 (AT-HCO2), high temperature-ambient pCO2 (HT-ACO2) and high temperature-high pCO2 (HT-HCO2). Treatment conditions were monitored daily, with temperature measured at 08:00, 12:00 and 18:00 hrs using a digital thermometer (Fisher Scientific model #150778, ± 0.05 °C), and light intensities at 12:00 hrs using a Li-Cor LI-193 sensor attached t 170 o a LI-1400 meter. Seawater within each tank was replaced at 200 ml/min with filtered seawater (50 micro-m) pumped from Cook’s Bay.