The future of coral communities in high temperature and rainfall scenarios: a casa study from Hong Kong

The metabolic function of shallow ecosystems is threatened by severe fluctuations in terms of temperature and nutrient availability under greenhouse gas emissions. Global warming and ocean acidification are the main global impacts on coral ecosystems and are related to the alteration of metabolic status, bleaching events and reduced calcification rates. Based on short-term adaptation, coral species were naturally selected at the community level and only heat-tolerant species survive to dominate. Seawater surface temperature and rainfall anomalies have been recently recorded as extreme events in Hong Kong waters. However, the extent of future scenarios for coral communities is still unknown.
Here, we report the climate projections for Hong Kong based on IPCC Fifth Assessment Report (AR5) and the physiological status of corals under increasing anomalies of temperature and rainfall relative to the average 1986 – 2005. We recorded several anomalies in seawater surface temperatures (+4.31°C in May 2018; +3.22°C in February 2019) and rainfall (-247 mm in May 2018; +183 mm in August 2018). The metabolic response of corals is expected to be significantly adverse in these scenarios, with reduced overall energetics and calcification.
Although corals living in this marginal area are supposed to be well adapted to survive under highly fluctuating environment, the extent of heatwaves and heavy rainfall will modify the pattern of local coral biodiversity. Future research will focus on the physiological adaptation of these corals under extreme scenarios.