Balancing the Budget on Coral Reefs

Coral reefs are the only marine ecosystem that is strongly defined by a geological component. The calcium carbonate skeletons of corals, algae, and other reef organisms that grow in place on a reef eventually become part of it, and over time this surplus of rock and sediments accumulates into large rock structures. While reef structures were reviled by early navigators because of the danger they posed to ships, they are valued today because they support extremely high biodiversity and act as breakwaters along many coasts. Reef ecosystems are increasingly affected by global-scale environmental changes that will decrease their reef-building capacity. There will be less carbonate production because there will be fewer corals and algae, and those that remain will grow more slowly. There will also be higher rates of carbonate removal because reef erosion and dissolution rates will increase. After millions of years of reef-building, the 21st century budget for reef building is thus likely to shift into the red - to reef destruction. This talk introduces the various components of the reef-building budget, and sets the stage for the remaining talks in the session. It also forces us to consider how much we value coral reef structures. We have always known that reef communities are important to reef building, but now we must ask the reverse: How important is reef building to a coral reef community?