Reefs of Future Present: Hong Kong Corals from the Qing Dynasty to the Information Age

Abstract

My geologist friends tell me that Hong Kong has no 'proper' coral reefs. This is because there is no evidence of carbonate formations upon which living corals are still found. Instead, corals grow on exposed bedrock in a patchy distribution and any exposed carbonates are quickly eroded away. Were there proper coral reefs in the past? Consider that during the Qing Dynasty the industrial production of slaked lime was extensive throughout Hong Kong, yielding 40 tons per year from mining living bivalve and coral communities. Indeed, historical records and archaeological evidence describe a very different environment in the past; where apex predators, megafauna, and diverse reef invertebrates were common. Through archeological digs, we show that the diversity and abundance of corals and other invertebrates declined markedly over the last century, including the extirpation of several coral species. We analyzed subtidal push cores to show that coral abundance has decreased by 50%, and coral fragment identification from sediments to delineate a 40% contraction in the range of important staghorn corals. Today, coral decline is closely linked to coastal development and pollution, which limits the recovery of coral communities. However, thanks to government efforts at improving water quality, we demonstrate that active restoration of coral communities is possible. Through targeted propagation and transplantation we show that staghorn corals have high rates of growth and survivorship in areas where they were previously eliminated giving hope to the future of these marginal reefs.