Severe bioerosion of a living coral colony in
Panama. In this example, the living coral
(which is green) is infested by bioeroding
bivalves (the key-shaped holes in the
skeleton). Photo credit: Hannah Barkley
An important component of this removal is bioerosion, the biologically mediated breakdown and dissolution of calcium carbonate. Our lab published a new paper, released just this week, which shows that rates of bioerosion of coral skeleton - by worms, sponges, and bivalves - are accelerated by ocean acidification and nutrients. As CO2 levels increase in the atmosphere, some of the CO2 enters the ocean, and through a series of well-known chemical reactions, seawater pH decreases (hence "ocean acidification"). Using cores drilled from living coral colonies across natural gradients of CO2 and nutrients in the Pacific Ocean, we found that bioerosion rates are greatest where pH is low and nutrients are high. In Palau, where there is a strong natural gradient in pH under persistently low nutrients, bioerosion rates clearly tracked the pH variability around the archipelago.
Computerized tomography (CT) scans of
cores of coral skeleton. The light gray to white
colors indicate the coral skeleton. Boreholes
are visible within these skeletons. Photo
credit: Tom DeCarlo
Our experiments begin here shortly! The 4-story scaffolding tower is built out on the reef, and some of our instruments are in the water collecting data. Today and tomorrow, we are deploying the rest of our instruments in time for our experiments to begin this weekend.
- Tom DeCarlo