Yet another effect of global warming and changing ecosystems. Corals worldwide are at risk from a major episode of bleaching which turns reefs white.Although reefs represent less than 0,1% of the world’s ocean floor, they help support about a quarter of all marine species. The US National Oceanic and Atmospheric Administration (NOAA) says the livelihoods of 500 million people and income worth over $30bn (£19,6bn) are at stake.
The bleaching has hit reefs in the Pacific, Atlantic and Caribbean.The NOAA has warned it may affect over 38% of the world’s reefs, and kill over 12,000 sq km of reefs. The mass bleaching is caused by rising water temperatures resulting from two natural warm currents and exacerbated by man-made climate change.
Bleaching happens when corals under stress drive out the algae known as zooxanthellae that give them colour.If normal conditions return, the corals can recover. But the process can take decades, and if the stress continues, the corals can die.
Reefs are under multiple threats including pollution, over-fishing, sedimentation and damage from boats and tourism.The current worldwide bleaching episode is predicted to be the worst on record as the warming Pacific current, El Nino, increases in strength. Water temperatures are being driven further by a separate natural warm-water mass dubbed the Pacific Blob.Man-made climate change also contributes, as the oceans are absorbing about 93% of the increase in the earth’s heat.Additionally, corals face ocean acidification as CO2 emissions are absorbed into the oceans, changing the pH of seawater.
Read more here.