'Shocking' decline seen in oceans

20 June 2011 Last updated at 12:24 GMT By Richard Black Environment correspondent, BBC News Coral reefs are subject to "multiple stressors" that could destroy many within a human generation The oceans are in a worse state than previously suspected, according to an expert panel of scientists.

In a new report, they warn that ocean life is "at high risk of entering a phase of extinction of marine species unprecedented in human history".

They conclude that issues such as over-fishing, pollution and climate change are acting together in ways that have not previously been recognised.

The impacts, they say, are already affecting humanity.

The panel was convened by the International Programme on the State of the Ocean (IPSO), and brought together experts from different disciplines, including coral reef ecologists, toxicologists, and fisheries scientists.

Its report will be formally released later this week.

"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."

These "accelerated" changes include melting of the Greenland and Antarctic ice sheets, sea level rise, and release of methane trapped in the sea bed.

Fast changes

"The rate of change is vastly exceeding what we were expecting even a couple of years ago," said Ove Hoegh-Guldberg, a coral specialist from the University of Queensland in Australia.

Some species are already fished way beyond their limits - and may also be affected by other threats

"So if you look at almost everything, whether it's fisheries in temperate zones or coral reefs or Arctic sea ice, all of this is undergoing changes, but at a much faster rate than we had thought."

But more worrying than this, the team noted, are the ways in which different issues act synergistically to increase threats to marine life.

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.

Carbon deposits Life on Earth has gone through five "mass extinction events" caused by events such as asteroid impacts; and it is often said that humanity's combined impact is causing a sixth such event.

The IPSO report concludes that it is too early to say definitively.

But the trends are such that it is likely to happen, they say - and far faster than any of the previous five.

"What we're seeing at the moment is unprecedented in the fossil record - the environmental changes are much more rapid," Professor Rogers told BBC News.

"We've still got most of the world's biodiversity, but the actual rate of extinction is much higher [than in past events] - and what we face is certainly a globally significant extinction event."

The report also notes that previous mass extinction events have been associated with trends being observed now - disturbances of the carbon cycle, and acidification and hypoxia (depletion of oxygen) of seawater.

Levels of CO2 being absorbed by the oceans are already far greater than during the great extinction of marine species 55 million years ago (during the Paleocene-Eocene Thermal Maximum), it concludes.

Blue planet

The report's conclusions will be presented at UN headquarters in New York this week, when government delegates begin discussions on reforming governance of the oceans.

In the long run, greenhouse gas emissions must be cut to conserve ocean life, the report concludes

IPSO's immediate recommendations include:

stopping exploitative fishing now, with special emphasis on the high seas where currently there is little effective regulationmapping and then reducing the input of pollutants including plastics, agricultural fertilisers and human wastemaking sharp reductions in greenhouse gas emissions.

Carbon dioxide levels are now so high, it says, that ways of pulling the gas out of the atmosphere need to be researched urgently - but not using techniques, such as iron fertilisation, that lead to more CO2 entering the oceans.

"We have to bring down CO2 emissions to zero within about 20 years," Professor Hoegh-Guldberg told BBC News.

"If we don't do that, we're going to see steady acidification of the seas, heat events that are wiping out things like kelp forests and coral reefs, and we'll see a very different ocean."

Another of the report's authors, Dan Laffoley, marine chair of the World Commission on Protected Areas and an adviser to the International Union for the Conservation of Nature (IUCN), admitted the challenges were vast.

"But unlike previous generations, we know what now needs to happen," he said.

"The time to protect the blue heart of our planet is now."

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Acid oceans turn 'Nemo' fish deaf

31 May 2011 Last updated at 23:47 GMT By Richard Black Environment correspondent, BBC News Baby clownfish face a "wall of mouths" when they first arrive at the reef Clownfish, the spectacular tropical species featured in the movie Finding Nemo, appear to lose their hearing in water slightly more acidic than normal.

At levels of acidity that may be common by the end of the century, the fish did not respond to the sounds of predators.

The oceans are becoming more acidic because they absorb much of the CO2 that humanity puts into the atmosphere.

Scientists write in the journal Biology Letters that failing to move away from danger would hurt the fish's survival.

"Avoiding coral reefs during the day is very typical behaviour of fish in open water," said research leader Steve Simpson from the School of Biological Sciences at the UK's Bristol University.

"They do this by monitoring the sounds of animals on the reef, most of which are predators to something just a centimetre in length.

"But sounds are also important for mate detection, pack hunting, foraging - so if any or all of those capacities are gone, you'd have a very lost fish," he told BBC News.

Previous research has shown that fish also lose their capacity to scent danger in slightly more acidic seawater.

The fish were put in a "choice chamber" that allowed them to swim away, or not, on hearing the noise

The team raised baby clownfish in tanks containing water at different levels of acidity.

One resembled the seawater of today, with the atmosphere containing about 390 parts per million (ppm) of carbon dioxide.

The other tanks were set at levels that could be reached later this century - 600, 700 and 900 ppm.

The more CO2 there is in the atmosphere, the more the oceans absorb - and the more they absorb, the more acidic the water becomes.

In this experiment, the fish could decide whether to swim towards or away from an underwater loudspeaker replaying the sounds of predators recorded on a reef, with shrimps and fish that would take a small clownfish.

In water with today's levels of CO2, the fish spent three-quarters of the time at the opposite end of the tube from the loudspeaker.

But at higher concentrations, they showed no preference. This suggests they could not hear, could not decipher or did not act on the warning signals.

"The reef has been described as 'a wall of mouths' waiting to receive the clownfish," said Dr Simpson.

Continue reading the main story The oceans are thought to have absorbed about half of the extra CO2 put into the atmosphere in the industrial ageThis has lowered its pH by 0.1pH is the measure of acidity and alkalinityLiquids lie between pH 0 (very acidic) and pH 14 (very alkaline); 7 is neutralSeawater is mildly alkaline with a "natural" pH of about 8.2The IPCC forecasts that ocean pH will fall by "between 0.14 and 0.35 units over the 21st Century, adding to the present decrease of 0.1 units since pre-industrial times""What we have done here is put today's fish in tomorrow's environment, and the effects are potentially devastating."

If it takes several decades for the oceans to reach these more acidic levels, there is a chance, the team says, that fish could adapt.

Whether that can happen is one of the outstanding questions from this research. Another is whether other species are similarly affected.

A third question is why the fish are affected by these slight changes in acidity.

There appears to be no physical damage to their ears; the team suggests there could be some effect on nerves, or maybe they are stressed by the higher acidity and do not behave as they otherwise would.

Further experiments are in train that may answer those questions.

Concern about ocean acidification has arisen considerably more recently than alarm over global warming; but already there is ample evidence that it could bring significant changes to ocean life.

The organisms most directly affected appear to be corals and those that make shells, such as snails.

Just this weekend, another team of researchers published findings from a "natural laboratory" in the seas off Papua New Guinea, where carbon dioxide bubbles into the water from the slopes of a dormant volcano.

This local acidity is too much for most corals; instead, an alternative ecosystem based on seagrasses thrives.

With carbon emissions continuing to rise, researchers predicted most reefs around the world would be in serious trouble before the end of the century.

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