Coral reefs next to a major conurbation: a study of temporal change (1985−2011) in coral cover and composition in the reefs of Jakarta, Indonesia

Coral reefs are diverse, ecologically important and globally threatened ecosystems. Numerous studies have reported on the threats to coral reefs, which include both local perturbations, such as pollution and overfishing, and widespread phenomena, such as bleaching. Here, we report on the history of the Jakarta Bay−Thousand Islands reef system from 1985 to 2011. Over this period, we recorded significant shifts in coral generic composition and an overall decline in coral cover with widely different trajectories between in-, mid- and offshore zones. In 1985, coral cover exhibited a clear on-to-offshore gradient with low coral cover inshore (10%), moderate cover midshore (49%) and high cover offshore (74%). The low coral cover inshore contrasts strongly with reports of high coral cover for inshore reefs in 1929. Inshore, coral cover declined from 10% in 1985 to <5% in 1995. The greatest change in coral cover and composition, however, occurred in offshore reefs, where mean cover declined from 74 to