Oceans: not as healthy as they should be

The oceans are in a worse state than previously suspected, according to scientists of the International Programme on the State of the Ocean (IPSO). Ocean life is "at high risk of entering a phase of extinction of marine species unprecedented in human history".

Over-fishing, pollution and climate change are acting together in ways that have not previously been recognised, experts can confirm. The impacts, they say, are already affecting humanity.

"The findings are shocking," said Alex Rogers, IPSO's scientific director and professor of conservation biology at Oxford University. "As we considered the cumulative effect of what humankind does to the oceans, the implications became far worse than we had individually realised.

"We've sat in one forum and spoken to each other about what we're seeing, and we've ended up with a picture showing that almost right across the board we're seeing changes that are happening faster than we'd thought, or in ways that we didn't expect to see for hundreds of years."

Some pollutants, for example, stick to the surfaces of tiny plastic particles that are now found in the ocean bed. This increases the amounts of these pollutants that are consumed by bottom-feeding fish.

Plastic particles also assist the transport of algae from place to place, increasing the occurrence of toxic algal blooms - which are also caused by the influx of nutrient-rich pollution from agricultural land.

In a wider sense, ocean acidification, warming, local pollution and overfishing are acting together to increase the threat to coral reefs - so much so that three-quarters of the world's reefs are at risk of severe decline.