From the warm waters of Hawaii to the vast Indian Oceans, coral reefs worldwide are being hit with the worst mass bleaching event ever recorded.
Declared a global bleaching event on Oct. 8 by the U.S. National Oceanographic and Atmospheric Administration (NOAA), the calamity is the third event of this kind recorded in history. And environmental scientists predict it will get worse in the next few months.
“We’ve been hearing worrying reports of bleaching from various places, and now the bad news is officially here, with worse news likely yet to come with the strengthening El Niño,” said Nancy Knowleton, an expert on coral reefs with the Smithsonian Institution.
Warm ocean temperatures have been linked to climate change and increasingly strong El Niño events have caused reefs to expel algae from them, leaving them white.
Healthy corals are colourful due to the relationship they have with microscopic algae called zooxanthellae. The algae provide oxygen and other nutrients that coral needs to survive. In exchange, the coral gives the algae carbon dioxide and other substances released which it needs. This symbiotic relationship becomes compromised when the coral is stressed.
Coral stress can occur when there is a change in environmental conditions, such as an increase in ocean temperatures, light, or pollution. With stress, the relationship between the coral and algae changes as the coral is unable to supply the algae with nutrients it needs for photosynthesis. This leads to the expulsion of algae in the coral and a bleached white appearance. While not dead, this is a dangerous condition for the coral to be in. Without the algae, the coral has lost a major food source, leaving it more vulnerable to disease and death.
Supporting an estimated 25 per cent of marine species, the loss of coral reefs due to bleaching is not only effecting the algae, but also entire marine ecosystems.
“Coral reefs are the underwater equivalent to rainforests, and by removing the corals, you remove the trees of the underwater world,” said Richard Vevers, head of the XL Catlin Seaview Survey.
Current events began back in 2014 in parts of the Pacific, first observed in Guam and the Northern Mariana Islands. Reefs from the Pacific, Indian and Atlantic Ocean are now all experiencing this bleaching event. According to Nature news, NOAA estimates that the bleaching could by the end of the year affect more than a third of the world’s coral reefs—and kill more than 12,000 square kilometers of them. To top it all off, for the past several months a warm mass of water, dubbed ‘the blob,’ has been discovered moving back and forth across the northern Pacific, keeping water temperatures high.
“The temperatures we’re seeing are anomalies and have the potential to dramatically impact the integrity of reefs around the word,” said Ruth Gates, a marine biologist at the Hawaii Institute of Marine Biology in Kaneohe.
Currently, scientists are unsure whether the blob is linked to climate change or other large-scale atmospheric patterns. However, NOAA is using data on sea-surface temperature, gathered from their Polar-orbiting Operational Environmental Satellites, to help create global maps that show them where the waters are warm enough to cause bleaching.
In a privately funded project, the XL Catlin Seaview Survey has been working to map out reefs found in 26 countries since 2012. This effort should help scientists document the mass bleaching events and compare the present day bleaching to previous bleaching events.
Despite positive steps being made, the reality is that once corals die the effects are not easily reversible. According to the head of NOAA’s Coral Reef Watch Mark Eakin, the best recovery time that can be anticipated for coral is 10 to 20 years—and some corals are being repeatedly hit once every five years.
Should we wish to protect the future of coral reefs and all the biodiversity there needs to be protection for the reefs and a reduction of carbon emissions.