Seagrasses Enable Nearby Corals to Withstand Ocean Acidification
Manzello, D.P., Enochs, I.C., Melo, N., Gledhill, D.K. and Johns, E.M. 2012. Ocean acidification refugia of the Florida Reef Tract. PLoS ONE 7: e41715.
During times of heightened oceanic vegetative productivity, the five U.S. researchers found "there is a net uptake of total CO2 which increases aragonite saturation state (Ωarag) values on inshore patch reefs of the upper Florida Reef Tract," and they say that "these waters can exhibit greater Ωarag than what has been modeled for the tropical surface ocean during preindustrial times, with mean Ωarag values in spring equaling 4.69 ± 0.10." At the same time, however, they report that Ωarag values on offshore reefs "generally represent oceanic carbonate chemistries consistent with present day tropical surface ocean conditions."
Manzello et al. hypothesize that the pattern described above "is caused by the photosynthetic uptake of total CO2 mainly by seagrasses and, to a lesser extent, macroalgae in the inshore waters of the Florida Reef Tract." And they therefore conclude that these inshore reef habitats are "potential acidification refugia that are defined not only in a spatial sense, but also in time, coinciding with seasonal productivity dynamics," which further implies that "coral reefs located within or immediately downstream of seagrass beds may find refuge from ocean acidification." And in further support of this conclusion, they cite the work of Palacios and Zimmerman (2007), which they describe as indicating that "seagrasses exposed to high-CO2 conditions for one year had increased reproduction, rhizome biomass, and vegetative growth of new shoots, which could represent a potential positive feedback to their ability to serve as ocean acidification refugia."
Palacios, S. and Zimmerman, R.C. 2007. Response of eelgrass (Zostera marina L.) to CO2 enrichment: Possible impacts of climate change and potential for remediation of coastal habitats. Marine Ecology Progress Series 344: 1-13.