Meeting Abstract
Projected increases in ocean pCO2 levels are likely to affect calcifying organisms more rapidly and to a greater extent than any other marine organisms. The effects of ocean acidification (OA) has been documented in numerous species of corals in both laboratory and field studies. However, the majority of laboratory studies have utilized flow-through exposure systems. Challenges of a recirculating system include effectively off-gassing carbon dioxide from waste water and accounting for the compounding effects of CO2 from acidifying treatment water and organismal respiration. We developed a recirculating coral exposure system that allows precise pCO2 control using a combination of off-gassing measures including: aeration, water retention devices, venturi injectors, and algal scrubbing. The system is being utilized in a comparative study to identify changes in skeletal weight and tissue growth in three major reef-building corals of the Caribbean: Pseudodiploria clivosa, Montastrea cavernosa, and Orbicella faveolata exposed to either present-day pCO2 levels or 1000 µatm (IPCC A1F1 scenario). Preliminary results indicate that OA-induced reductions in scleractinian coral growth is species specific. Combining photogrammetric analysis (tissue growth) and advances in the buoyant weight technique provide an area density that can be used to infer the rate of calcification and erosion. The recirculating exposure system can provide laboratories without access to flow-through systems to contribute to the growing field of coral OA discovery.
