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Category — Ocean changes

Acid oceans already harming more species

Tim Radford

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A water melon sea urchin in Sardinian waters: Acid seas do not help larval digestion. Image: Marco Busdraghi via Wikimedia Commons

As climate change warms the world’s oceans, they are becoming more acidic. Researchers in Europe and the US have found the rising acidity is bad news for several species.

The chemistry of the oceans is changing. And it isn’t just the corals and the baby oysters that are unhappy. It makes juvenile rockfish really anxious, and it upsets the digestion of sea urchins.

The pH (a measure of acidity – the lower the pH, the more acid the water) of the planet’s oceans is dropping rapidly, largely because the carbon dioxide levels in the atmosphere are increasing. Since carbon dioxide dissolves in water to form carbonic acid, the seas are responding to global change.

The first and clearest victims are likely to be the corals, which are adapted to a specific value of pH in the oceans, but there have also been problems reported by oyster farmers.

Now Martin Tresguerres of the University of California, San Diego reports in the Proceedings of the Royal Society B that at least one species of juvenile fish responds badly to the changes in ocean chemistry.

There is a natural aspect to ocean acidification – submarine volcanoes discharge carbon dioxide and turn the deep seas around them to a kind of fizzing champagne, and upwelling ocean currents can occasionally deliver a stressful level of lower pH sea water to blight fishing waters. [Read more →]

December 4, 2013   No Comments

Deep ocean offers hints of warming

Tim Radford

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A deep sea squid swims past a submersible: Science needs to know more about the depths. Image: NOAA Picture Library via Wikimedia Commons

A long-term study of the deep ocean floor has revealed possible signs of global warming even down there. Understanding what happens at such depths should help scientists construct more accurate climate models.

US and British researchers may have identified the fingerprint of global warming in one of the darkest, coldest, most mysterious places on the planet. Four thousand metres below the sea surface, at the bottom of the north-east Pacific abyss, they have found changes in the food supply to some of the planet’s least known creatures. And these changes track changes to temperatures at the surface.

Kenneth Smith of the Monterey Bay Aquarium Research Institute and colleagues from the University of Southampton in the UK, and the Scripps Institution of Oceanography in San Diego, report in the Proceedings of the National Academy of Sciences on a 24-year exploration of one of life’s deepest puzzles.

The research is important because it provides yet another indicator of the carbon cycle at work; it is important because it provides another level of understanding of the climate system; and because it provides yet another way to check on global warming.

The last aspect is probably the least significant, if only because the period of observation is so brief, the study is confined to only one site, and the conditions for observation so difficult.  But it offers a neat demonstration of how science is done. [Read more →]

November 30, 2013   No Comments

UK waters grow cooler – and more acid

Alex Kirby

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Heading out… catches of Atlantic cod, and other cold water species, have halved. Image: Peter from Edinburgh, Scotland, UK via Wikimedia Commons

A comprehensive report on the state of the seas around the United Kingdom says ocean acidification is probably increasing faster than for the last 300 million years.

Dipping your toes in the waters around Britain has grown marginally less inviting: in the last few years the seas have grown slightly colder.

Against the background of a continued warming trend, this blip is explained by scientists as an example of the climate’s tendency sometimes to go “off trend”, and to show clear variations from the norm.

UK researchers say the average UK coastal sea surface temperature in the last decade was lower in 2008-2012 than in 2003-2007, an example of short-term variability which they say is at odds with temperature records which “continue to show an overall upward trend“.

The finding – perhaps not surprising, given the slower pace of atmospheric warming in recent years – is reported by the Marine Climate Change Impacts Partnership (MCCIP) and is published in its latest Report Card, which assesses how climate change is affecting UK waters.

MCCIP, launched in 2005, is a partnership between scientists, the UK Government and its agencies, non-governmental organisations and industry. [Read more →]

November 28, 2013   No Comments