Rates of carbonate dissolution in permeable sediments estimated from pore-water profiles: The role of sea grasses

In this study we estimate sediment carbonate dissolution rates for sandy sea grass sediments on the Bahamas Bank using an inverse pore-water advection/diffusion/reaction model constrained by field observations. This model accounts for sea grass O-2 input to these sediments, and also parameterizes pore-water advection through these permeable sediments as a nonlocal exchange process. The resulting rates of carbonate dissolution are positively correlated with sea grass density, and are comparable with previous rate estimates for Florida Bay sediments. In contrast, the advective uptake of O-2 by these sediments decreased with increasing sea grass density. This suggests that the competing interplay between bottom-water flow, near-seabed pressure gradients, and the presence of a sea grass canopy is important in controlling this type of sediment oxygen uptake. When the carbonate dissolution rates estimated here are examined in the context of carbonate budgets for shallow-water carbonate platforms systems, they suggest that carbonate dissolution may be a significant loss term in these budgets. Sea grass-mediated carbonate dissolution may also exert a negative feedback on rising atmospheric CO2, although the magnitude of this effect remains to be quantified.