Predicting future coral survival: The effect temperature and ocean acidification have on soft coral physiology.

Coral reefs are one of the most important ecosystems, however, due to global and regional threats, their future is uncertain. Increases in sea surface temperature, which decouple the animal host and photosynthesizing dinoflagellate symbiosis (coral bleaching), represent one of the greatest immediate threats to coral reefs. While decreases in ocean pH (ocean acidification) is a longer term threat to reef accretion. Much of the current research has focused on the single and combined effects of increased temperature and ocean acidification on hard skeleton producing corals. Yet, it remains unknown how these stressors affect soft coral physiology. Therefore, the single and combined effects of thermal stress and ocean acidification were tested on two species of soft coral, Capnella sp. and Sinularia Dura, over a treatment period of three months. Corals were treated under four conditions, including a control at ambient temperature and ambient pCO₂ (25.5°C, 390 ppm), thermal stress and ambient pCO₂ (31.0°C, 390 ppm), thermal stress and elevated pCO₂ (31.0°C, 750 ppm), and ambient temperature and elevated pCO₂ (25.5°C,750 ppm). Elevated pCO₂ concentrations were used to mimic current and projected atmospheric concentrations at the end of the century. To analyze coral physiology, we are currently measuring photosynthesis and respiration rates, total biomass, lipid, carbohydrate, and protein concentrations. These data will provide a greater understanding of how soft corals respond to temperature and pCO2 in the context of current climate change and provide insight on how reef diversity and structure will change in the coming decades.