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NEAH BAY — Measurements of ocean acidification off the North Olympic Peninsula coast at Tatoosh Island show acidity is rising more than 10 times faster than climate models have predicted.
The researchers cannot say whether the trend is widespread.
The eight years of research also revealed that the corrosive effect of acidic ocean waters could trigger a dramatic shift in coastal species and jeopardize some shellfish stocks.
“The increase in acidity we saw during our study was about the same magnitude as we expect over the course of the next century,” said study co-author Timothy Wootton, a marine biologist from the University of Chicago.
While the waters off the Peninsula may be a unique environment, “this raises a warning flag that the oceans may be changing faster than people think,” he said.
Wootton warned that an acidity-driven shift in coastal ecosystems could spell disaster for shellfish industries that rely on mussels and other similar species.
His team’s findings were published last week in the Proceedings of the National Academy of Sciences.
Increased carbon dioxide emissions from human activities and the burning of fossil fuels have led to a 30 percent rise in ocean acidity in the past 200 years.
Oceans absorb about a third of the CO2 released into the atmosphere, and when the CO2 dissolves in water, it forms carbonic acid, which alters the ocean’s chemical balance.
The resulting acidification prevents marine life such as coral in coral reefs, as well as crabs, lobsters and oysters, from building calcium carbonate skeletons and shells, impairing their ability to survive and reproduce.
Wootton did not intend to measure the effects of ocean acidification when he installed his ocean monitors in the waters near Tatoosh Island in 2000.
Tatoosh Island lies about a half mile off Cape Flattery, on the Makah tribal reservation, just west of Neah Bay.
But as global concern over ocean acidification grew, “I realized we’d been sitting on all this data that we could use to determine whether it was happening,” Wootton said.
His instruments recorded changes in pH — a measure of acidity that lowers as acidity rises.
“The expectation was that the pH would change so slowly that it would be hard to see a change.
“We were sort of surprised to find in general just how much it was changing over time.”
From there, Wootton looked at his biological observations to try to assess how much these pH changes matter to the ecosystem of the area.
Tatoosh’s shifting balance
Wootton and colleagues built models of an ecosystem based on field data of how species interact along Tatoosh Island’s rocky shores.
Surprisingly, in a scenario of increasing acidity, not all species with calcium carbonate shells faired badly.
Instead, a shift took place.
Larger mussels and barnacles suffered, leaving smaller barnacles and some calcium-based seaweeds better off.
In nature, “species are competing for space, they are eating each other, it’s an incredibly dynamic system,” said James Forester, a Harvard University ecologist and a co-author of the study.
“When you change the playing field — in this case by altering acidity — you can get unexpected responses,” he said.
Said Wootton:
“Mussels usually dominate the ecosystem because they are good at overgrowing and crushing out other species that grow on the rocks.
“But when the mussels decline, it means other species — no matter whether or not they have a shell — can do better.”
And, Wootton added, “the changes we see in the dynamics of the ecosystem may magnify over time.”
Further studies needed’
The study contained the first data on ocean acidity from temperate — rather than tropical — waters.
No one knows whether similar rapid changes are taking place elsewhere.
“The rules might be quite different on Tatoosh Island,” Wootton suggested.
“There could be mechanisms going on in the waters around our island that are unique.
“We really need to get more data from other sites away from the equator to see what patterns are there.”
Agreeing with him was Richard Zeebe of the University of Hawaii at Manoa.
He pointed out that Wootton’s study was on a coastal site, not in the open ocean, so “one needs to be cautious about extrapolating the pH findings to other locations.”
The part of the ocean that Wootton studied also experiences a great deal of upwelling, so it’s not completely surprising to find changes in acidity, said Zeebe.
Alaska’s reefs damaged?
Earlier this month, Oceana, a Washington-based conservation group, said coral reefs in the cold deep seas off Alaska may now be among the first victims of global warming in a marine environment that is home to half of the U.S.’s commercial fishing.
The loss of Alaska’s cold-water reefs may be a precursor to the extinction of reefs worldwide because of acidification, according to an analysis by Ocean.
Cold water absorbs more carbon dioxide than tropical waters.
