Corals May Get Temporary Reprieve from Bleaching

Climate models show the absence of a global atmospheric circulation pattern which bolsters high ocean temperatures key to coral bleaching
Brittany Patterson, E&E News Scientific American 24 Feb 17;

The world's coral reefs, which have been hit hard by an unprecedented bleaching event that began in mid-2014, may see a bit of reprieve this year, according to an official at the National Oceanic and Atmospheric Administration.

Mark Eakin, head of NOAA's Coral Reef Watch program, said the "longest, most widespread bleaching event ever" has continued into 2017. However, climate models show the absence of a global atmospheric circulation pattern or ENSO — those include El Niños and La Niñas — which would bolster high ocean temperatures key to coral bleaching. Without an ENSO event, fewer corals are expected to die.

"The good news is as far as we can tell, the worst of this global event is over," he said. "The unfortunate part is we're not finished yet."

The world's corals may not be out of the woods yet. Eakin said it also appears ocean conditions may have entered what could be a "new regime" in which persistent coral bleaching — when corals expel the algae that are key to their survival from inside their tissue and turn white — is the new normal.
"The strange part is we finished with the El Niño; we even finished with the La Niña, but now we're continuing to see this bleaching going on even when we're back in neutral ENSO conditions," he said. "And it even looks like for the Pacific, for the coming months, we're going to be showing El Niño-like threats to coral reefs."

Eakin said the "unusual situation" seems to be driven by the fact that the oceans are still full of warm water, which has accumulated over the past years, the warmest on record. That warming is being driven primarily by human-caused climate change.

"We're really entered into a new regime where the waters are just warmer, and we may have hit this threshold for corals to bleach that's just the new baseline," he said. "We may be moving into a new period where bleaching is going to be very different than what we have seen in the past."

All of the coral reefs in the world were stressed by the warm ocean conditions of the last few years. More than 40 percent of reefs worldwide experienced bleaching or death.

In 2014, reefs in Guam, Hawaii and the Marshall Islands were hit. The next year, Hawaii was hit again, and the bleaching spread across the Red Sea, into the central Pacific Ocean and into Australia.

In 2016, Eakin said, the event came to full force. Scientists famously declared wide swaths of the Great Barrier Reef dead, while places like Kiribati saw 80 to 95 percent mortality of their corals.

In addition, 72 percent of coral reefs in the United States experienced bleaching or death.

"We were hoping 2016 would be the end of this event; unfortunately, that's not the case," he said.

Already, Australian officials have reported coral mortality across the central part of the Great Barrier Reef, and the South Pacific island of Niue has experienced a severe bleaching event.

Eakin, speaking yesterday to the U.S. Coral Reef Task Force, an interagency group that leads efforts to protect U.S. coral reef ecosystems, highlighted that NOAA, in addition to other partners, since 2013 has been developing climate adaptation tools for coral reef managers. In 2015, a nursery in Hawaii went out and collected corals to protect them before a bleaching event hit the region, for example. Other regions are experimenting with coral plantings, shading and other adaptation efforts, with more in the works.

One key to protecting coral reefs is reducing local stressors, such as boat traffic and pollution runoff. Strategies to do that and adapt in the face of climate change are both ongoing efforts, Eakin added. Climate change further complicates the process.

"The real challenge is we have to be dealing with those local stressors that make bleaching events worse and make it harder to recover, and then we have to be dealing with [the] main problem here [which] is [that the] rise of heat-trapping carbon dioxide gases is warming the world," he said.

Reprinted from Climatewire by E&E provides daily coverage of essential energy and environmental news at www.eenews.net.