A Pacific carbonate budgets approach reveals overall net positive production on O'ahu, Hawai'i.

Abstract

As changes in regional and global climates continue to exacerbate natural and anthropogenic stressors on coral reef ecosystems, quantifying a reef's ability to produce its calcium carbonate framework and identifying the taxa that drive calcification and bioerosion dynamics are essential for effective coral reef management. The net carbonate production rate, or carbonate budget, of a coral reef estimates the balance between calcium carbonate (CaCO3) production and erosion. Census-based methods estimate this budget as a single representative functional health metric, alongside additional reef health indicators such as coral cover, diversity, and structural complexity. Here, we report an assessment of census-based coral reef carbonate budgets for seven coral reef sites around O'ahu, Hawai'i. Coral CaCO3 production rates were calculated using a regionally-refined database of species- and genera-specific calcification rates for corals within the Pacific Islands region. Additionally, we tested metrics of percent coral cover, coral genera diversity, and structural complexity (rugosity) as predictors for reef framework growth and erosion. Net CaCO3 production for O'ahu ranged from -0.15 ± 0.34 to 6.34 ± 0.82 kg CaCO3 m-2 yr-1, with four sites demonstrating net positive production and three sites near zero net production. Coral cover and coral genera diversity were strong predictors of gross carbonate production, while reef rugosity was a poor predictor. The ratio of percent coral cover to carbonate production differed among coral taxa, suggesting that the use of species- and genus-specific growth rates may improve the representativeness of gross and net carbonate production calculations.