Ocean acidification: examples of potential impacts

Ocean acidification is caused by ocean uptake of anthropogenic CO2; it is a global issue and is happening now, it is measurable, and it will continue as more CO2 is emitted. Already ocean acidity has increased by 30% since the industrial revolution and by 2100, if we continue emitting CO2 at the same rate, ocean acidity would have increased by as much as 150%. Such a substantial alteration in basic ocean chemistry is likely to have wide implications for ocean life, especially for many organisms that require calcium carbonate to build shells or skeletons (Turley and Findlay, 2009 ).

Webinar: US public’s perceptions, knowledge, and attitudes toward ocean acidification

[Originally disseminated by OCB]

Dear Ocean Acidification Research Community,

As the study of ocean acidification (OA) continues to gain momentum, policymakers and journalists will be looking to you, the scientists, for answers. How are changes in ocean chemistry likely to affect ecosystems and the human communities that depend on them? When can we expect to see effects? Where have we seen effects already, and why?

Acidic seas spell bad news for sea butterflies (audio)

Thecosome pteropods, also known as sea butterflies, are an important group of ocean wanderers that may disappear from northern oceans by the end of century as the oceans become more acidic, removing a key food source for Arctic fish, birds and whales.

One of the major threats facing the oceans is acidification – with increasing levels of carbon dioxide in the atmosphere, more of the gas is dissolving the oceans, leading to a lowering of pH and a reduction in the concentration of carbonate ions. And that’s going to make life difficult for the many marine species that use these ions to build calcium carbonate shells, including sea butterflies.

They’re closely related to the sea angels that featured in our Christmas show last year – you might remember the shelless molluscs that produce bad-tasting chemicals to defend themselves from attack. The main difference for the sea butterflies is that they protect themselves with a shell made from a relatively unstable form of calcium carbonate called aragonite.

Ocean acidification and life on the sea floor

Ocean acidification (OA) sounds like the stuff of nightmares but it’s happening now – since the start of the Industrial Revolution, the hydrogen ion concentration of the surface ocean – the variable that determines how acidic it is – is estimated to have increased by nearly 30 per cent. How? The chemistry is straightforward. As human activities produce more CO2, more of the gas enters the ocean and reacts with sea water. This releases negatively-charged (acidic) hydrogen ions and reduces pH. It’s that simple.

What isn’t simple is demonstrating the consequences; just how OA may affect marine organisms and ecosystems, including not only seaweed, sea urchins and fish, but also bacteria and plankton. There is growing evidence that some organisms, such as coral reefs, are being affected in some parts of the world, but what of the life around our own shores?

What we do know is that if we keep emitting CO2 at today’s rates, by 2100 average surface ocean pH will have fallen from 8.1 to around 7.8 – average levels the Earth has probably not experiencedfor more than 20 million years. This would have wide implications for ocean life, especially, but not exclusively, for organisms that need calcium carbonate to build shells or skeletons. Not only do increased hydrogen ion concentrations inhibit calcium carbonate formation, but they can slowly dissolve calcium carbonate structures, even if pH is greater than the ‘neutral’ value of 7.0.

Rare undersea volcanic vents show oceans’ increasing acidity likely to hurt biodiversity, endanger ecosystem stability, say Stanford researchers

Some rare undersea volcanic vents that emit carbon dioxide – which makes the water around them more acidic – have given Stanford researchers a look at how marine ecosystems may be affected as global warming intensifies. Carbon dioxide is the principal greenhouse gas causing global warming, and as it accumulates in the atmosphere, it also moves into the ocean and increases its acidity.

Stanford researchers have gotten a glimpse into an uncertain future where increasing levels of carbon dioxide in the Earth’s atmosphere will lead to higher levels in the ocean as well, leaving the water more acidic and altering underwater ecosystems.

The glimpse comes from waters near Ischia, Italy, where unusual shallow-water volcanic vents in the floor of the Mediterranean Sea bubble carbon dioxide into the water, creating a local underwater neighborhood that may resemble the ocean of the future.