Oceans’ rising acid levels have emerged as one of the biggest threats to coral reefs, acting as the “osteoporosis of the sea” and threatening everything from food security to tourism and livelihoods, the head of a US scientific agency said.

The US government’s incident commander for the Gulf of Mexico oil spill said today that BP’s blown-out well is expected to be permanently sealed and declared dead by Sunday, nearly five months after a rig explosion set off the disaster.

The US is reopening more federal waters in the Gulf of Mexico for commercial and recreational fishing that had been closed because of the massive oil spill, a government official said today.

Crews hurried to get back to work on plugging BP's leaky oil well after Tropical Storm Bonnie fizzled out and engineers hoped for a window of clear weather long enough to stop the gush for good.