Over Easy: Coral bleaching threat increasing with warmer ocean temperatures

On Monday, the National Oceanic and Atmospheric Administration (NOAA) reported an increased threat of coral bleaching in the western Atlantic and Pacific oceans. NOAA predicts increased coral bleaching in Northern Hemisphere reefs through October. According to NOAA, when water is too warm, the coral expels its symbiotic algae (zooxanthellae) living in their tissues causing the coral to turn completely white.

The Guardian obtained additional figures and reported on Tuesday that according to NOAA scientists, 15,000 square kilometers of coral reef could be lost in the current mass bleaching.

But the devastation is only getting started. The event could continue well into 2016. NOAA announced on Monday that the western Atlantic is about to heat up, turning the corals of the Caribbean bone white. When this occurs, bleaching will have hit every tropical ocean basin on Earth since June last year.

In all, scientists forecast a total of 15,000 sq km of reef may not recover and losses to the world’s remaining coral reefs would be a devastating 6%.

Dr Mark Eakin, the co-ordinator of Noaa’s Coral Reef Watch programme, said that given uncertainties around how long the event will continue it was very difficult to predict exactly how much reef would be wiped out.

“It probably won’t be as big as 1998, so we’re probably talking hopefully no more than 10%. Even if we’re talking one to 10% of the coral reefs around the world that’s a huge amount of coral reef area,” he said.

In Australia’s Great Barrier Reef, a conservation group fitted a turtle with a GoPro camera, to show some spectacular footage of the health of the reef:

Contrasting futures for ocean and society from different anthropogenic CO2 emissions scenarios

Warming and acidification of surface ocean waters will increase proportionately with cumulative CO2 emissions (see figure). Warm-water corals have already been affected, as have mid-latitude seagrass, high-latitude pteropods and krill, mid-latitude bivalves, and fin fishes. Even under the stringent emissions scenario (RCP2.6), warm-water corals and mid-latitude bivalves will be at high risk by 2100. Under our current rate of emissions, most marine organisms evaluated will have very high risk of impacts by 2100 and many by 2050. These results—derived from experiments, field observations, and modeling—are consistent with evidence from high-CO2 periods in the paleorecord.