Westcountry scientists have warned of a looming "triple trouble" which "threatens the ocean and everything it provides".

Over the coming decades and centuries, the ocean will become increasingly hit by at least three interacting factors, they believe.

Rising seawater temperatures, ocean acidification and ocean deoxygenation will cause substantial changes in marine physics, chemistry and biology.

But experts, including those from Plymouth Marine Laboratory, said they were only just beginning to understand what the impact would be, although it would affect the whole planet.

Dr Carol Turley, from the laboratory, is among those taking the warning to the United Nations Framework Convention on Climate Change conference in Durban, South Africa, this week.

"Often forgotten in such discussions are the ocean and the enormous and diverse resources it provides, including food and other resources – even half the oxygen we breathe," she said.

"The health of the ocean is therefore relevant to every one of us on planet earth and we are concerned about how these three stressors – ocean warming, acidification and deoxygenation – produce a very worrying combination which threatens the ocean and everything it provides us.

"We have produced a short 'Ocean Stress Guide' that sums this up in clear language. We would urge everyone to read it."

While ocean acidification, which is directly caused by the increase of carbon dioxide levels in the atmosphere, has been recognised as a research priority, deoxygenation has not.

Climate change can influence the amount of dissolved oxygen in sea water with potentially devastating effects for fish, sea-mammals and other vital marine organisms. Low oxygen levels in the ocean may also increase the amount of greenhouse gases in the atmosphere.

With ocean warming, the pressures represent "triple trouble", scientists said, which could rapidly threaten ecosystems as well as food sources.

The partnership, of Plymouth Marine Laboratory, Scripps Institution of Oceanography at UC San Diego and a host of international research programmes, said the potential effects needed to be investigated.

Professor Bob Watson, chief scientist at the Department of Environment, Food and Rural Affairs, said: "The ocean is an incredible source of food and an amazing source of biodiversity.

"Now we see these irreplaceable resources facing not one but three stressors potentially acting together in ways that we are only just beginning to investigate and understand.

"Highlighting this unholy alliance is essential if stakeholders and governments are to make decisions that will affect everyone on this planet."