Seasgrass Productivity Elevates Ωar and Calcification Rates in Acropora Cervicornis

• Main Author: Strueben, Martine
• Other Authors: Chris Langdon, Daniel Suman, Maria Estevenez, Margaret Miller
• Format: Other/Unknown Material
• Language: unknown
• Published: Scholarly Repository 2014
• Subjects: Acropora Cervicornis; ocean acidification; seagrass productivity; aragonite saturation state; calcification rates; Ocean acidification
• Online Access: https://scholarlyrepository.miami.edu/oa_theses/531; https://scholarlyrepository.miami.edu/cgi/viewcontent.cgi?article=1538&context=oa_theses

Carbon fluxes associated with seagrass bed metabolism are known to cause an elevation in the aragonite saturation state (Ωar) of the overlying water. It has been hypothesized that corals located downstream could experience a boost in their ability to calcify. Given that seagrass biomass and productivity are known to be stimulated by ocean acidification (OA) conditions, the possibility exists that the rise in Ωar could increase as OA conditions become more severe. If true, corals on patch reefs ringed by extensive seagrass beds, as is common on the Florida Reef Tract, could potentially be buffered to some degree from the ill effects of OA. A patch reef fringed by seagrass beds located near Broad Key (25.334N, 80.199W) served as the in situ study site. The in situ growth rates of Acropora cervicornis corals located in the seagrass bed and on the patch reef were measured to gauge the response of the corals to the increase in Ωar. Several Lagrangian drifts were conducted to quantify the increase in Ωar as a parcel of water flowed over the seagrass bed to the patch reef. A lab study was set up to evaluate the calcification response of Acropora cervicornis to changes in pCO2 from ambient (390ppm) to projected (900ppm) pCO2 conditions. Using the results of the lab study it was found that the calcification response of A. cervicornis to a unit change in Ωar was 21.6%, which is a similar response to pCO2 as other coral species as observed by Chan and Connolly, 2011. A second model was created to calculate the benefit of seagrass productivity on the calcification rates of Acorpora cervicornis based on the results of the lab study and Lagrangian drifts. This model found that seagrass the benthic community, which was predominantly composed of Thalassia testudinum, was capable of enhancing calcification rates of Acorpora cervicornis by 7% on average ranging from 0% to 22%. It is unclear, however, how much of an impact seagrass beds will have in the future as various stressors threaten their existence.