Effects of Ocean Acidification on Mesocosm Coral Calcification Rates

Ocean Acidification (OA) refers to the increasing uptake of anthropogenic pCO₂ by the ocean resulting in the decline of pH level. Elevated levels of pCO₂ are altering the carbonate chemistry of the ocean, lowering the amount of CaCO₃ available to corals for calcification. This greatly impacts hermatypic corals, which play a significant role in the structure and biodiversity of coral reefs. In this study, the effects of increased pCO₂ levels of 900 ppm on the calcification rates of coral reef species were determined. It was hypothesized that elevated pCO₂ levels would cause a decrease in coral calcification rates. The water flow, nutrient levels, temperature, and light were kept near-natural conditions. Water samples were collected twice a week and dissolved inorganic analyses and total alkalinity titrations were performed. In addition, calcification and photosynthesis rates were calculated to determine the aragonite saturation state (Ω_ar) of the tanks to assess if there was a significant change in Ω_ar. Preliminary results suggest that calcification rates decrease with increased pCO₂; further experiments are still underway to provide additional evidence in support of this conclusion.