A study on coral restoration in Hong Kong with reef building coral Acropora digitifera

Abstract

Corals are benthic marine animals. The reef ecosystem they create provides important habitat for different marine life, protects our shoreline and offers us a magnificent underwater world to explore. The economic value of goods and services it provides is estimated to be US $375 billion per year. However, due to a great variety of local and global stressors ranging from overfishing to climate change, there is a major decline and degradation of the global coral reef ecosystem. Conditions for corals are not better in Hong Kong. Corals here have been suffering chronically from a wide range of stressors such as destructive fishing, coral mining, sedimentation, pollution, cyclones, extreme temperatures among others. All these stressors work together and negatively impact the survivorship of corals. However, amidst all the detrimental factors, corals here have shown great resilience and more than 90 stony coral species can be found locally, which is more than reported for the Caribbean Sea. If great effort can be put in coral restoration, we might be able to revitalize the coral reef ecosystem here in the metropolis of Hong Kong. However, coral restoration is a relatively new topic that requires more attention not only from academia but also from the government and the public as the coral reef ecosystem is important to humanity. In this study, we identified two major gaps in local coral restoration. First, the optimal conditions for coral growth are largely unknown, and second, there is no management framework for a financially self-sustaining coral restoration program. A lab experiment and semi-structured interviews were conducted to address the two gaps, respectively. The experiment has shown that branching coral Acropora digitiferah as more volume and surface area growth in temper water temperature around 24°C and such growth is corelated to the initial coral fragment size. We integrated this finding with the interview results and proposed a management framework for coral restoration that can potentially be self-sustaining financially.