Even as bleaching continues, hope remains for coral reefs

The NOAA predicts coral bleaching and reef die-offs will worsen over the next year, but others are more confident in corals' resiliency. 

Oceans are already in the midst of the longest coral bleaching event on record. Now, the National Oceanic and Atmospheric Administration (NOAA) says there’s no end in sight.

The scientific agency forecast Monday that many of the world’s coral reefs will be exposed to abnormally high temperatures for the third year in a row, exposing them to further bleaching. The outlook coincides with the International Coral Reef Symposium in Honolulu, which brings 2,500 of the leading coral reef scientists, policymakers, and managers from 70 different nations together every four years.

"It’s time to shift this conversation to what can be done to conserve these amazing organisms in the face of this unprecedented global bleaching event,” said Jennifer Koss, the director of NOAA’s Coral Reef Conservation Program, in a statement. “Local conservation buys us time, but it isn’t enough. Globally, we need to better understand what actions we all can take to combat the effects of climate change."

Others are more hopeful, however, as efforts are underway to better understand coral and the algae that live with them, their relationship with humans, and humankind's ability to aid coral reefs in this fight.

Coral bleaching occurs when warmer and dirtier waters disrupt the symbiotic relationship between coral and the zooxanthellae algae that live inside them. In exchange for a home, the algae provide the coral with nutrients, as well as its bright colors.

As sea temperatures rise, the coral expels algae. Without their microscopic guests, the coral calcifies, and turns white. If the water temperature cools, algae often return to the coral. If the water doesn’t cool, the coral can die.  

With the world’s oceans experiencing higher-than-normal temperatures since mid-2014, coral reefs are experiencing a major bleaching event, and in some cases are dying off. It worsened this year, as the 2015-16 El Niño was one of the strongest ever. Warmer waters in the eastern Pacific brought on by El Niño contributed to major bleaching events across it, even along the Great Barrier Reef in Australia to scientists’ surprise there. And it’s expected to get even worse. A La Niña event, which typically follows El Niño, is expected to keep waters in the western Pacific warm.

This stretch of higher-than-normal temperatures are expected to further damage reefs in Hawaii, Guam, the Commonwealth of the Northern Mariana islands, the Caribbean, and the Gulf of Mexico, according to NOAA. There is a 90 percent chance of widespread coral bleaching in the Pacific island nations of Palau and the Federated States of Micronesia during La Niña, according to NOAA. Coral are, however, remarkably resilient organisms, especially if they’re healthy.

Considering this, there are efforts to keep coral healthy and to develop new ways to improve coral’s resistance to bleaching. Different localities have attempted to reduce sediment runoff and other human impacts on coral such as overfishing to boost coral’s ability to bounce back from bleaching events. Scientific agencies and policymakers have also sought to further protect and rehabilitate coral reefs.

NOAA took a step in that direction, listing 20 types of coral as threatened in 2014, although it originally considered listing 66. Increasing the threat status of these species forces other federal agencies to consult with NOAA before it funds or authorizes any action that could affect them. Australian scientists have pressured their government to take action too, both to protect reefs and combat climate change. Meanwhile, scientists have found certain coral are more resilient than they though, especially in places they didn’t expect.

Researchers found certain coral reefs closer to human populations and fished areas are doing surprisingly well, according to an article published June 15 in the scientific journal Nature.

“What we saw is that people who are dependent on [a reef] are more likely to be better stewards, perhaps because if they crash that resource they are really in trouble,” co-author Jack Kittinger of Conservation International told National Geographic. 

Dr. Kittinger and his co-authors argue for two-pronged approach: studying how these localities have learned to manage their reefs and mitigate stressors and learned to coexist with reefs, and pressuring nations to reduce their carbon emissions and other impacts that increase ocean temperatures and acidification.

Other researchers have set out to learn why some coral are more resilient than others. Researchers led by Andrea Grotolli, head of Ohio State University’s Division of Water, Climate, and the Environment, found coral with higher fat reserves are better able to survive bleaching events until they could acquire new algae. Conservation efforts could be concentrated on zones that favor these types of coral.

And Ruth Gates, a research professor at the University of Hawaii’s Institute of Marine Biology, and Madeleine van Oppen, a senior research scientist at the Australian Institute of Marine Sciences, are engineering coral that are highly resistant to climate stresses and use them to re-colonize several, reported the University of Minnesota’s Institute on the Environment.