Warm water events, how should we deal with them?

There is little doubt that we shall experience more warm water events in the next 50-100 years, and that some of them will be more severe than the 1998 event.

 

Unfortunately very little can be done to prevent these threats but, from experience, we know that some corals survive such events.

 

Corals may survive disturbances because they live on deeper reefs where water temperatures are less variable; in lagoons, where they may be used to large daily fluctuations in temperature; or protected by specific oceanographic phenomena, such as the upwelling of cool deep waters. These potential sources of larvae need to be identified, managed appropriately and protected from further damage in order to promote recovery and boost the resilience of individual coral colonies and the reef system as a whole.

 

Areas which may be less affected by anomalous SSTs such as channels, lagoon and areas of upwelling should be considered as important.

 

Corals that do survive warm water events will be of key importance for the supply of coral larvae to replenish degraded areas. Some surviving reefs will have the potential to supply larvae (source reefs), while others will receive larvae via ocean currents (sink reefs). Some reefs may be sinks at one time of year and sources at another time, where monsoonal currents reverse in different seasons.

 

Several factors determine whether a reef is a good source of coral larvae:


 

• The presence of large coral colonies that may produce large numbers of larvae.


• High coral diversity, which may increase the chance of rapid colonisation by opportunistic, fast growing species and later by slower growing species.


• Minimal presence of human impacts on the reef, such that the chance of coral reproduction and larval survival is maximised.


• Presence of upwelling water, which will assist with the transportation and survival of coral larvae.


• The presence of prevailing wind and oceanic currents that flow past the source reef and towards the degraded (sink) reef.