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Ocean acidification on the rise, UN climate change study finds




The 200-island nation of the Maldives exists mostly within a meter of sea level. As seas rise, it's threatened, but changing temperature and ocean acidification are problems for seafood-eating residents, too.
The 200-island nation of the Maldives exists mostly within a meter of sea level. As seas rise, it's threatened, but changing temperature and ocean acidification are problems for seafood-eating residents, too.
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The ocean absorbs one-fourth of the world's carbon emissions, yet that capacity is diminishing fast. That's according to an annual UN study, known as the Greenhouse Gas Bulletin, out this week from the World Meteorological Organization.

That capacity is just 70 percent of what it was at the beginning of the industrial era, and it could go all the way down to 20 percent by the end of the century, the study finds.

All that matters because the dynamic affects seawater acidity.

Related: Increasingly acidic ocean dissolving key marine snails along West Coast

It's a phenomenon known as acidification and it's taking place in the world's oceans at a rate that the report calls "unprecedented." Scientists are still trying to understand exactly how it affects marine life, said Dr. Andrew Dickson, professor of marine chemistry at the SCRIPPS Institution of Oceanography at UC San Diego.

From the WMO Greenhouse Gas Bulletin report:

The current rate of ocean acidification appears unprecedented at least over the last 300 million years, based on proxy-data from paleo archives. In the future, acidification will continue to accelerate at least until mid-century, based on projections from Earth system models.

The potential consequences of ocean acidification on marine organisms are complex. A major concern is the response of calcifying organisms, such as corals, algae, mollusks and some plankton, because their ability to build shell or skeletal material (via calcification) depends on the abundance of carbonate ion. For many organisms, calcification declines with increased acidification. Other impacts of acidification include reduced survival, development, and growth rates as well as changes in physiological functions and reduced biodiversity.