Coral reefs are highly diverse ecosystems, valued globally at about $9.8 trillion each year. Since the 1980s, however, three mass coral “bleaching” events have been observed. Efforts to understand and prevent this damaging phenomenon are bringing new data to the surface.
Coral “bleaching” refers to the loss of symbiotic algae that give coral reefs their distinctive colors and energy. If a coral is severely bleached, it can become diseased and die.
There have been three “global coral bleaching events,” according to the National Oceanic and Atmospheric Administration (NOAA). The latest one, 2014-2017, started in the north Pacific in 2014, expanded to the south Pacific and Indian oceans in 2015, and spread to the Hawaiian Islands.
The first global bleaching event was observed in 1998 when a strong El Niño was followed by an equally strong La Nina. A second event occurred in 2010.
Corals can and do recover from mild bleaching episodes. However, severe or long-term bleaching can destroy the corals, leading to degradation of the reefs. This in turn affects shorelines and habitats for fish and other marine life.
Bleaching occurs when normal summer temperature limits are exceeded by more than a few weeks. Risk factors include global climate change, fishing practices, and pollution from land.
Real-time satellite and other monitoring of coral reefs can lead to early detection of oceanic heat stress, and actions can be taken, such as temporarily closing a reef to fishing and scuba diving, to protect these ecosystems.
– Source: National Oceanic and Atmospheric Administration, US Department of Commerce