Natural laboratory for ocean acidification

2008-06-08

in Science, The environment

One of the larger unknowns when it comes to the impact of human carbon dioxide emissions is the degree to which living things will be harmed by more acidic oceans. This is occurring because water with more CO2 dissolved in it is more acidic. There are concerns that overly acidic sea water might compromise the ability of organisms with shells made of calcium carbonate to build and maintain their bodies. Other affects on marine ecosystems are anticipated, though it is challenging to assess what their magnitude will be and when they will occur.

Scientists recently completed a study of a place where such effects are occurring naturally due to carbon dioxide venting from the sea floor:

Around the vents, [pH] fell as low as 7.4 in some places. But even at 7.8 to 7.9, the number of species present was 30% down compared with neighbouring areas.

Coral was absent, and species of algae that use calcium carbonate were displaced in favour of species that do not use it.

Snails were seen with their shells dissolving. There were no snails at all in zones with a pH of 7.4.

Meanwhile, seagrasses thrived, perhaps because they benefit from the extra carbon in the water.

The latest IPCC estimate is that global pH will fall from 8.1 today to about 7.8 by 2100. Greater than expected CO2 emissions would cause a larger change. Coral reefs are especially likely to suffer.

Oceanic acidification is the inevitable result of adding CO2 to the atmosphere, but it not otherwise causally connected to climate change. It does add a complication to any plan that seeks to reduce global temperature change through a means other than reducing CO2 emissions; even if more energy could somehow be reflected or dissipated into space, the marine consequences of acidic oceans would endure.

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{ 6 comments… read them below or add one }

. June 8, 2008 at 11:14 pm

A Sea Change will focus public attention on this urgent but little-known crisis. It follows retired educator and concerned grandfather Sven Huseby back to stunning ancestral sites (Norway, Alaska the Pacific Northwest) where he finds cutting-edge ocean research underway. His journey of self-discovery brings adventure, surprise and revelation to the hard science of acidification.

tristan June 9, 2008 at 5:22 am

“Oceanic acidification is the inevitable result of adding CO2 to the atmosphere, but it not otherwise causally connected to climate change.”

How can you know that it is “not otherwise connected”? How can you know what kind of connections it might have?

Milan June 9, 2008 at 8:43 am

Mostly, I meant that it is an independent physical and chemical process from the one that goes from higher GHG concentrations to increased temperatures.

It is quite likely that there will be situations in which the combination of higher temperatures (or other manifestations of climate change) and more acidic oceans will have important consequences.

. June 9, 2008 at 10:05 am

Scientists Surprised to Find Earth’s Biosphere Booming

“An article from the Financial Post says that recent studies of biosphere imaging from the NASA SEAWIFS satellite indicate that the Earth’s biomass is booming: ‘The results surprised Steven Running of the University of Montana and Ramakrishna Nemani of NASA, scientists involved in analyzing the NASA satellite data. They found that over a period of almost two decades, the Earth as a whole became more bountiful by a whopping 6.2%. About 25% of the Earth’s vegetated landmass — almost 110 million square kilometers — enjoyed significant increases and only 7% showed significant declines. When the satellite data zooms in, it finds that each square meter of land, on average, now produces almost 500 grams of greenery per year.’ Their 2004 study, and other more recent ones, point to the warming of the planet and the presence of CO2, fertilizing the biota and resulting in the increased green side effect.”

. June 9, 2008 at 11:03 am

The fraction of CO2 remaining in the air, after emission by fossil fuel burning, declines rapidly at first, but 1/3 remains in the air after a century and 1/5 after a millennium (Atmos. Chem. Phys. 7, 2287-2312, 2007).

. March 12, 2009 at 3:35 pm

‘Coral lab’ offers acidity insight

By Roger Harrabin
Environment analyst, BBC News

Far more alarming is the experiment on a humble calcareous algae, which looks like pink paint on a rock.

This algae plays a vital role in cementing reefs together. But it cannot survive the pH levels of 8.0 predicted before the end of the century, possibly as early as 2050.

That means the reefs are likely to begin to crumble.

“Corals will continue to exist,” Dr Fine says, “but the reefs will be greatly changed from what we know now and their biodiversity will be dramatically reduced.

“This will make them much more vulnerable to other catastrophic events, like bleaching.

“We are piling problems upon each other.”

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