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Rising Acidity Threatens Marine Ecosystems Off San Diego

Above: Ocean acidification causes ecosystems and marine biodiversity to change. It has the potential to affect food security and limit the capacity of the ocean to absorb CO2 from human emissions.

Aired 11/19/13 on KPBS News.

Acid levels in the ocean are expected to increase 170 percent by the end of the century, according to a new study. A San Diego researcher explains the consequences of climate change playing out off our coast.

Acidity levels in the world’s oceans are rising at an alarming rate, threatening ecosystems and causing biodiversity to change, scientists warn.

The primary cause of ocean acidification is human-made carbon dioxide emissions, according to a new report from the Third Symposium on the Ocean in a High-CO2World, compiled by 540 experts from 37 nations.

The report states oceans could become 170 percent more acidic by 2100 compared to levels before the Industrial Revolution.

Oceans help modify climate change by absorbing about a quarter of carbon dioxide emissions from the atmosphere, but rising carbon dioxide levels are causing the ocean to warm and acidify at a rapid pace.

Matthew Edwards, professor of biology at San Diego State University and the Coastal and Marine Institute Laboratory, has studied the impact of acidification on kelp forests for more than 20 years.

“Particularly, we focus on things that photosynthesize, very much like plants that take energy from the sun and fix carbon dioxide to make sugars and to make plant material,” explained Edwards. “We’re looking at that process in the ocean.”

Some species of marine algae thrive in elevated carbon dioxide because they photosynthesize better in high-carbon dioxide conditions, said Edwards.

“However, we’re also finding that the acidification side of things is also hurting them,” Edwards added. “So there’s this kind of dual thing going on and we’re trying to figure out the balance between these two.”

Edwards said the overall outcome is a potentially dangerous reduction in biodiversity. He said ocean species compete for light, nutrients and space similar to species in a tree forest.

“If you walked out to a terrestrial forest, you see a surface canopy and below that where it’s shaded, you have a whole suite of species,” he said.

But in an area where there isn’t that canopy to block the sun, there's a different set of species, Edwards added.

Edwards said if kelp forests begin to change and thin out, there will be far-reaching consequences.

"This is going to change how much habitat is out there, how much food is out there, are there things to eat, and just the whole hunting, nursery grounds for lots of things — all the way up to seals and birds and otters," Edwards said.

Edwards and his graduate students go on weekly dives to collect kelp samples to study in a manipulated ocean chemistry in their lab. He said It's an attempt to predict the future -- one that's looking increasingly ominous.

"This is the most pressing issue facing the coastal environment," he said. "As the oceans continue to become more acidic the problem is going to get worse and worse."

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