Scientists' Health Check Of The World's Oceans

Sky News has been shown first-hand the devastating consequences of human activity on the world's oceans.

We were taken in a mini-submarine to the seabed 10 miles off Bermuda by scientists conducting the most comprehensive-ever ocean 'health check'.

We saw areas that should have been teeming with life. But while there was plenty of vegetation and small fish there were barely any larger species such as parrot fish or jacks.

A second, deeper, dive by the mission's principle scientist, Professor Alex Rogers of Oxford University, also found an alarming lack of bigger fish.

He told Sky News that the area had almost certainly been over-fished, top-slicing the delicate 'food web' that the ecosystem needs to thrive.

He said: "When you seriously over-exploit marine ecosystems it can take them decades to recover - and that is in shallow water.

"You can imagine what happens if you drag a net through a deep sea coral bed. That is going to take hundreds of years to recover, if it recovers at all."

The team - a collaboration between the Nekton Mission and Project Baseline - is spending three weeks surveying marine life off Bermuda, an island created by a long-extinct volcano that soars from the deep ocean floor.

But just days into the project the findings underline the threats to the world's oceans.

Although conservationists have pushed for a marine park to be established around the island to protect the Atlantic's most northerly coral reefs, the proposal has been strongly opposed by sport fishermen.

Triton submarine pilot Patrick Layhey has clocked up more than a thousand dives.

He said delicate corals are often being covered in what appears to be pollution.

"What I see more and more of is this almost smothering of the reef," he said.

"I think that's probably from sewage and run off from the land."

Human-induced climate change is also having a major impact on the oceans.

Sea temperature has increased by 1C in the last 30 years.

And the water has absorbed more than 500 billion tonnes of carbon dioxide from the atmosphere since the start of the industrial revolution, increasing the acidity of the oceans by 30% as the gas dissolves.

Oliver Steeds is leading the XL Catlin-sponsored mission to survey five oceans over five years.

He said: "We know the deep ocean is changing at its fastest rate for millions of years.

"What we don't really understand at the moment is its health and its resilience. We need far more missions like this.

"And that's the problem. Trillions are being spent going to outer space and hardly any money is being spent going into inner space, the deep ocean - despite how critical it is for humanity."

The research combines diving teams, mini-submarines and remotely controlled submersibles.

The scientists are taking high resolution video along a defined track of the seafloor to study the area's biodiversity.

They are also collecting samples to be studied more closely in labs on board the mission's mothership, Baseline Explorer.