Above-normal ocean water temperatures are harming coral reefs around the world and due to a strong El Niño, along with the effects of climate change, negative impacts will likely continue into next year, experts say.
Earlier this month, scientists declared the third global coral bleaching event on record after widespread coral bleaching was reported across Hawaii, with similar conditions spreading through the Caribbean. Bleaching from this event first began in mid-2014 in the North Pacific before spreading to the South Pacific and Indian oceans this year.
Coral bleaching occurs when corals expel the symbiotic algae that lives in their tissues due to changes in water temperature, light or nutrients, thus causing the corals to turn white, the National Oceanic and Atmospheric Administration (NOAA) states. Corals are still alive when they turn white, but without the algae, their major source of food, corals can become more prone to disease, according to NOAA.
This circumstance is not limited to above-normal temperatures; coral bleaching has also occurred in cooler waters, notably in the Florida Keys in 2010, NOAA said. The previous two global bleaching events occurred in 1998 and 2010.
So far, this event is not as severe as those in 1998 and 2010, Mark Eakin NOAA's Coral Reef Watch coordinator, told AccuWeather.
"However, this may change in 2016 as the continuing strong El Niño means that this bleaching event will continue well into 2016 - perhaps through the end of 2016," he said.
In Hawaii, the ongoing El Niño is playing a role, but so is climate change and a blob of warm water in the Pacific, Eakin said.
"It's the worst bleaching ever seen in the main Hawaiian islands but not as severe as the bleaching seen in parts of the northwestern Hawaiian Islands and the Commonwealth of the Northern Mariana Islands last year," Eakin said.
The current El Niño started to develop during March and April of 2015, and the peak is expected for November or December, which is typical of any El Niño, AccuWeather Senior Meteorologist Jack Boston said.
El Niño is strengthening, Boston said, but at a slower rate than it did this spring and summer.
According to the Hawaii Department of Land and Natural Resources (DLNR), this is the second year of extreme bleaching across the Hawaiian Archipelago. Darla White, special projects coordinator for the DLNR's Division of Aquatic Resources, recently led a special dive off the coast of Maui to examine the Molokini Crater. While on the dive, she discovered that at least half of the corals at Molokini are currently bleached.
"It looks like a winter scene under water, and the extent of bleaching here and elsewhere around the state, hopefully reminds us all, that our coral reefs are intrinsically linked to Hawaii's economic, our culture and our way of life," she said in a press release. "We really hope people will get involved and learn what they can do to help. Simple changes in everyday habits to reduce carbon dioxide and other greenhouse gases can make a big difference."
The state of Hawaii is encouraging people to report or document coral bleaching to Eyes of the Reef Hawaii, a statewide reporting network that enables community members to assist with the protection of the reefs.
Extensive coral bleaching has a variety of impacts on marine life and particularly when it's a severe or long-term event, which can be lethal for corals. According to NOAA, thousands of species rely on reefs for survival and when corals die, reefs can quickly degrade and the structures built by corals' collapse. Subsequently, this means less shoreline protection from storms and fewer habitats for fish.
"Some reefs may recover from this event if they aren't hit by this thermal stress again. However, that's becoming increasingly unlikely," Eakin said. "You can't expect to regrow centuries-old coral in years or decades."
NOAA has been working with Hawaii state officials to help prepare for this bleaching since back in July when the organization warned that the threat was increasing in the western Atlantic and Pacific oceans.
Jennifer Koss, acting program manager for NOAA's Coral Reef Conservation Program, said people need to act locally and think globally about how pollution from the land and unsustainable fishing practices decrease the likelihood that corals can recover from bleaching events.
"To solve the long-term, global problem, however, we need to better understand how to reduce the unnatural carbon dioxide levels that are the major driver of the warming," she said in a news release.
Eakin added that it is critical that a strong climate treaty comes out of the United Nations Climate Change Summit this December in Paris.
"Bleaching in 2016 may be worse than 2015," he said.