Affiliation: College of Arts and Sciences, Environment, Ecology, and Energy Program - Environmental Science
Increasing inputs of anthropogenic CO2 have caused seawater pH to decline and ocean temperatures to rise. Calcifying organisms like corals are impacted by these global change stressors, which can often lead to reduced calcification rates. To better understand how duration of exposure to acidification and warming impacts coral calcification, we conducted a 95-day experiment investigating how pCO2 (280 - 2800 μatm pCO2) and temperature (28oC, 31oC) impact the skeletal morphology of individual colonies of the Caribbean coral Siderastrea siderea through time. Coral samples were collected from inshore and offshore reefs from the southern portion of the Belize Mesoamerican Barrier Reef System. Using stereomicroscopy, we quantified corallite height and infilling for individual corallites on experimental coral fragments. Corallite height measures the vertical distance from the basal plate to the septal ridge, and corallite infilling measures the ratio of skeletal structure to open space. Results suggest that corals from the offshore reef exhibit greater corallite height and greater corallite infilling than corals collected from inshore environments. Treatment temperature and pCO2 did not impact corallite height or percent skeletal infilling. Through exposure time to treatments, height and percent skeletal infilling did not change significantly; however, there was a pattern of decreasing infilling percentage through time for corals from offshore reefs. Results demonstrate that unique conditions found at the natal reef zones (i.e. wave energy, turbidity) play a larger impact than increasing temperatures and pCO2 values. Additionally, these results provide valuable insight into how global change stressors may alter the structural rugosity and durability of reef-building coral reefs.