Warm ocean temperatures may mean major coral bleaching

NOAA 17 Feb 15;

NOAA Coral Reef Watch’s newly-released four-month bleaching outlook indicates the greatest threat for coral bleaching through May 2015 is in the western Pacific and Indian Oceans in areas such American Samoa, Samoa, Western Australia, and Indonesia.

NOAA scientists are warning that warm ocean temperatures in the tropical Pacific and Indian Oceans could set the stage for major coral bleaching events across the globe in 2015.

Their warnings follow severe bleaching in 2014, and come with the release of the most recent outlook from NOAA’s Coral Reef Watch, a weekly product that forecasts the potential for coral bleaching up to four months in the future.

“The new outlook gives us greater confidence in what it shows for future coral bleaching and it comes at an important time,” said Mark Eakin, NOAA Coral Reef Watch coordinator. “The outlook shows a pattern over the next four months that is similar to what we saw during global coral bleaching events in 1998 and 2010. We’re really concerned that 2015 may bring the third global coral bleaching event.”

Coral bleaching infographic. (Credit: NOAA)

Coral bleaching takes place when corals are stressed by changes in conditions such as temperature, light or nutrients. They expel the symbiotic algae living in their tissues, causing them to turn white or pale. Without the algae, the coral loses its major source of food and is more susceptible to disease.

The outlook shows the greatest threat for coral bleaching through May 2015 is in the western South Pacific and Indian oceans. In the Pacific, thermal stress has already reached levels that cause bleaching in the nations of Nauru, Kiribati, and the Solomon Islands, and is expected to spread to Tuvalu, Samoa, and American Samoa in the next few months. In the Indian Ocean, thermal stress may reach levels that cause bleaching around Madagascar, Mauritius, Seychelles, and parts of Indonesia and western Australia.

NOAA scientists in American Samoa are already seeing the start of bleaching on their shallow reefs. “In the coming months, we will be watching to see if the model predicts conditions that can cause bleaching in Southeast Asia and the Coral Triangle region around mid-2015,” said Eakin.

The outlook, derived from NOAA’s operational climate forecast system models, shows regions that may be most affected by elevated ocean temperatures four months in advance. This latest generation of the outlook features greater global coverage, improved accuracy, and finer resolution.

In another significant advance, NOAA’s Coral Reef Watch program has refined its satellite observational capacity that provides near real-time information on coral reef environmental conditions. It now can focus on reef areas as small as five square kilometers, with an increase of as much as 50 times more data than before. This allows coral reef managers and scientists to accurately pinpoint bleaching thermal stress levels at coral reef scales and take actions to protect their coral reefs.

Initial tests of the outlook and daily five-kilometer bleaching thermal stress products proved useful for predicting, monitoring, and understanding major coral bleaching and mortality events in Guam, the Mariana Islands, the Northwestern and main Hawaiian Islands, the Marshall Islands, Kiribati, the Florida Keys, and elsewhere in 2014.

“Climate change and its impacts, which can include bleaching, are some of the most pressing global threats to coral reef ecosystems today,” said Jennifer Koss, acting program manager for NOAA’s Coral Reef Conservation Program. “This suite of products is vital to help scientists, coral reef managers, and decision makers in the U.S. and around the globe prepare for bleaching events.”

NOAA’s Climate Program Office, Coral Reef Conservation Program and National Centers for Environmental Prediction funded development of the outlook. NOAA Coral Reef Conservation Program and NASA’s Biodiversity and Ecological Forecasting program funded development of the five-kilometer coral bleaching thermal stress products.

For more information on coral bleaching and these products, visit: http://coralreefwatch.noaa.gov/satellite/index.php.

World's coral reefs face major bleaching event this year, US agency warns
Sophie Yeo for RTCC, part of the Guardian Environment Network The Guardian 19 Feb 15;

2015 could see coral bleaching on a global scale for the third time in history – and the first in the absence of an El Niño.

That is the latest prediction from the National Oceanic and Atmospheric Administration (Noaa), which has just launched a model to forecast threats facing the colourful reefs.

“It started in 2014 – we had severe bleaching from July to October in the northern Marianas, bad bleaching in Guam, really severe bleaching in the north western Hawaiian Islands, and the first ever mass bleaching in the main Hawaiian Islands,” said said Mark Eakin, Noaa’s Coral Reef Watch coordinator.

“It then moved south, with severe bleaching in the Marshall Islands and it has moved south into many of the areas in the western south Pacific.

“Bleaching just now is starting in American Samoa. In Fiji we’re starting to see some, the Solomon Islands have seen some. We’ve already seen a big event.”

Bleaching takes place when corals are stressed due to changes in light, nutrients or temperature – though only the latter can cause events of this magnitude. This causes them to release algae, lose their colour and in some cases die off.

It is a relatively rare occurrence. Large-scale bleaching was recorded in 1983, followed by the first global scale event in 1998. A second global wave came in 2010.

The latest global event appears to be following the path of the earlier two, with bleaching starting in the Pacific and expected to sweep through the Indian Ocean, south east Asia and the Caribbean.

The bleaching seen last year is expected to spread into 2015, added Eakin.

This week, Noaa launched an updated version of its Coral Reef Watch, which provides a four month forecast of how ocean ecosystems will be affected by high temperatures.

Normally, these are expected to show no bleaching. But high ocean temperatures throughout 2014 and into 2015 means that bleaching is predicted on a mass scale.

This is in spite of the fact that an El Niño – a natural phenomenon that raises ocean temperatures – did not develop as expected.

Instead, the ocean warming which is damaging the reefs has been caused by climate change.

Scientists at the UN’s Intergovernmental Panel on Climate Change say that 90% of the energy accumulated on the planet between 1971 and 2010 was stored in the ocean.

In 2014, oceans reached their highest temperature on record.

“The amount of heat that has been absorbed in the oceans and the warming that has gone on has resulted in the oceans being primed to reach levels that can cause coral bleaching even without big El Niño events,” said Eakin.

Maps released by Noaa of coral bleaching predictions between February and June show a 60% chance that almost all the coral reefs in the southern hemisphere – where it is summer – will experience at least some stress.

It is likely that this trend will move into the northern hemisphere as the seasons change, said Eakin, although the models do not forecast this far.

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It remains difficult to predict how severe the bleaching this year will be, he added, but some ecosystems are already under pressure.

“I doubt it’s going to be worse than 1998, and it may not even be worse than 2010 – we don’t know,” he said.

“But in some areas it has already been worse. What happened in the Marianas Islands, in the Marshall Islands, in the north western Hawaiian islands, those were the worst they’ve ever seen.”

In a large scale bleaching event, the damage caused could last for decades – and in some cases, the reefs never recover. Those that do become more susceptible to diseases.

But Noaa’s four month forecasts can help reef managers to prepare, and also to assess which reefs are more resilient, and which require more protection when a large scale bleaching is on the horizon.