Trouble in Tatoosh

The ocean's acidity around a tiny island off the Washington coast has been changing 10 times faster than expected. The surprising finding might reflect an oceanic hot spot, rather than a broader trend.
Crosscut archive image.

Dead mussels as well as live mussels with open, eroded shells are possible symptoms of stress from declining ocean pH and increasing acidity.

The ocean's acidity around a tiny island off the Washington coast has been changing 10 times faster than expected. The surprising finding might reflect an oceanic hot spot, rather than a broader trend.

Tiny and remote, Tatoosh Island is delivering a reality check to current ideas about carbon dioxide's impact on the environment. Research conducted on this island just off the northwest tip of Washington finds that the ocean is becoming acidic faster than scientists had expected, and that this is reshaping the marine life on the island's rocky shores right before their eyes.

"There's maybe more urgency than we thought there was," says J. Timothy Wootton, a professor at the University of Chicago who led the study, published online last month. Although previous studies have charted similar changes in tropical regions, this is the first to focus on temperate waters, which contain the most productive fishing grounds.

As carbon dioxide levels rise in the atmosphere, not only do we get a warmer climate, we also get a corrosive ocean. That's because carbon dioxide combines with water to produce carbonic acid.

But the big surprise here is that the ocean's acidity, or pH, has been changing 10 times faster than expected. Wootton and his colleagues tracked this change in the waters off Tatoosh Island over an eight-year period, amassing a whopping 24,519 measurements of ocean pH.

This high-definition dataset was almost an afterthought, says Wootton, whose main research interest is to chronicle the life and times of communities of marine organisms. "Tatoosh is a really good place for doing studies on how ecosystems are put together and how species interact with each other," he says. "The organisms on the shoreline are not so small that we need some high-tech equipment to see them, and yet they're small enough and move slowly enough in general that we can actually do some experiments."

Wootton and his team wondered whether changing ocean conditions might transform the poky denizens of Tatoosh, which include mussels, barnacles, and algae. That's why he began to collect data on ocean pH, temperature, and salinity eight years ago. He found that while ocean acidity increased, a dramatic restructuring of the community occurred: acid-tolerant algae grew and mussel populations fell. Sea creatures with shells or skeletons made of calcium carbonate were particularly vulnerable because acidic waters can dissolve their shells, he says.

"We were a little bit surprised we were actually able to detect effects in terms of how species were replacing each other," he says.

This is consistent with research on underwater volcanic vents off the coast of Italy published earlier this year. The waters near these carbon dioxide-producing vents are more acidic and the ecosystem is skewed toward non-native algae species and largely devoid of shelled organisms like sea urchins.

Do the Tatoosh Island results apply to the rest of the ocean? "I don't think we know that," says Wootton emphatically. The acidic waters there may indicate a hotspot rather than an ocean-wide phenomenon. This region of the Pacific Ocean may be more sensitive to pH changes, he says, due to upwelling currents that bring acidic waters from the deep up to the surface. This extra acidity could make it harder for the ocean around Tatoosh to recover from the acid produced when the ocean absorbs carbon dioxide from the air.

Still, the steep rise in ocean acidity in this remote spot is a wake-up call. "I think it serves more as a warning and a prompt that we should be perhaps paying more attention, especially in these temperate areas where we have less information," says Wootton.

And it shakes up the small comfort we land dwellers might have had as carbon dioxide increases in the atmosphere: The ocean's ability to absorb carbon dioxide always seemed like nature's way of helping us with our global warming problem. Now we see that even this is not for free.


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