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How troubling is ocean acidification?

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sightline | Jul 28, 2011 05:00 AM

By Jennifer Langston, Sightline.org

This post is part of the research project: Northwest Ocean Acidification

Not every commercial fisherman is convinced that curbing carbon emissions is necessary to stop global warming. But the evidence that fossil fuel pollution is making the oceans more corrosive—and removing building basic building blocks of the marine world—starts to get their attention.

In Alaska, commercial fishing supports one-sixth of the state’s economy and employs 70,000 people in high season, more than any other basic industry. Mark Vinsel, the executive director of United Fishermen of Alaska, the state’s largest commercial fishing organization, last year ranked his concerns about ocean acidification this way:

I’d say probably on a scale of 1 to 10, it would be 20 or 30.

If you sliced open the bellies of our most popular eating fish, at one point in their life cycle you would probably find krill, plankton, oceanic snails or other shelled creatures—the kinds of species likely to run into trouble as the oceans absorb more carbon dioxide from burning fossil fuels and other industrial processes.

As those carbon emissions rise, seawater becomes more acidic and sea life has more trouble finding calcium carbonate, a basic building block that many creatures need to build shells or skeletons, and, ultimately, to survive.

So if creatures at the bedrock layer of the marine food chain start to struggle in more corrosive seas, how might that affect an industry that provides nearly one-sixth of the world’s animal protein, not to mention $3.9 billion in personal income in Washington (roughly 2 percent of net earnings in the state) and more than $400 million in personal income in Oregon (one-half percent of net earnings)?

Here’s how Jeremy Brown, a Bellingham-based commercial fisherman who has spent nearly three decades fishing for salmon, halibut, black cod and albacore tuna, sees it:

I guess you could call it a second-order threat, but it’s still pretty immediate. I think this really is probably the most fundamental challenge we’ve got. There’s all this handwringing about the health of the oceans and people say ‘well, we’ve just got to manage fisheries better and maybe create some marine protected areas and everything will be fine in the garden.’ And that’s really not (the case). …We’ve really got to figure out how to burn a lot less fossil fuel and shift away from carbon-based policies.

Some might argue that oceans are resilient places, that nature abhors a vacuum, and that other kinds of algae or grasses that thrive in more acidic seas could replace losses at the bottom of the food web. In truth, we don’t yet know how complicated marine ecosystems will adapt to ocean acidification. The effects could range from minor to apocalyptic.

In that sense, you get to choose how scared you want to be, says Brad Warren, who directs the Sustainable Fisheries Partnership’s ocean acidification program. But the most knowledgeable scientists tend to eschew the more optimistic view, he said. And a smart businessperson pays attention to signs of trouble, tries not to get caught behind the curve, and needs to rethink old strategies when they’re no longer working. In other words, says Warren:

If you think of someone who has a fiduciary duty for the systems that feed us and provide jobs to half a billion people in the world—from subsistence hunting to those making a lot of money—one can view that with a gambler’s instinct or with a stewardship instinct. What would you rather be—a banker or a gambler—with this resource?

‘Different might be OK – Maybe

An ocean rich in calcium carbonate is like a nutritious miso soup, providing essential ingredients that everything from plankton, corals, mussels, oysters, crabs, scallops, lobsters, sea urchins and abalone need at some stage in their life cycle. As waters become more acidic, and calcium carbonate becomes less available, some of these species have trouble building shells, don’t grow as fast, or become stunted. As pH drops even lower, those protective coatings or internal structures can begin to dissolve.

“The thing that people really don’t appreciate is how many organisms have these calcium carbonate mineral phases,” said Burke Hales, an Oregon State University oceanographer.

The chart below shows that about half the annual catch in the US comes from mollusks and crustaceans, many of which use calcium carbonate. Another 24 percent are the animals that directly feed upon those “calcifiers.”

Acidification economics chart

Not all calcifying species will be affected by ocean acidification in the same way, and exposure to low pH waters varies by location, time of year, and even time of day. But because the Pacific Coast and Puget Sound are hot spots for corrosive waters, the threat to the Northwest economy is significant enough that researchers are working to see how local species will respond.

Laboratory studies conducted so far indicate that some of the direct and indirect effects of increasingly acidic oceans include:

Plankton: Some forms of plankton that other animals rely on for food struggle or die under low pH conditions. Pteropods—tiny winged sea snails comprise up to 60 percent of the diet of some juvenile salmon—have dissolved in low pH water. Embryos of Antarctic krill—which makes up a huge percentage of the diet of the southern oceans—have failed to hatch in highly acidic waters.

Structure: Species that provide key underwater habitat for other creatures are vulnerable to ocean acidification. Coral reefs, which support a huge amount of biodiversity, are among the least tolerant of low pH waters. If oyster populations crash, eventually oyster beds that help support everything from sea anemones to sportfish will suffer.

Other chemical and nutrient changes: Ocean acidification may affect the availability of other nutrients and trace metals, altering the composition of microscopic plant communities that other creatures eat.

Shellfish: Among commercially valuable species, mollusks appear to be at highest risk. Northwest oyster hatcheries have had massive die-offs in recent years. Mussels, clams and scallops exposed to carbon-dioxide-rich water have had trouble building shells or grew more slowly. Sea urchins become deformed and stopped reproducing. Abalone larvae have died. The picture, however, may be different for crustaceans, some of which have actually grown thicker shells in low pH waters.

Finfish: Direct effects on finfish are not clear (though clownfish have lost their sense of smell and ability to detect predators in acidic waters.) But if they may have to expend more energy or compete for food if they species they normally eat start to struggle.

Uncertainties about how these changes will play out across an entire ecosystem make it impossible to tally all the potential losses. One narrow case study found that if oysters and mussels decline in the wild at the same rate that’s been observed in the laboratory, we could expect $75 million to $187 million in annual losses in the US mollusk catch.

And, as the following chart shows, not all fisheries around the world will be affected equally. Below, the red colors include mollusks most likely to be affected by acidification, yellows indicate crustaceans, greens indicate predators that may be indirectly affected by food web effects, and blues indicate species whose responses to ocean acidification are unknown.

Catch Value Chart

Sarah Cooley, a Woods Hole Oceanographic Institution researcher working to put an economic value on ocean acidification’s potential consequences, explains in a very readable interview with Oceanus Magazine that Alaska’s fisheries (which produce 60 percent of the seafood in the US and where much of the Northwest fleet fishes) may be less vulnerable than New England fisheries that rely much more heavily on mollusks.

But the Alaskan catch could also decline, she said, because fish like haddock, halibut, herring, flounder, and cod eat mollusks themselves. And that could potentially affect top predators like swordfish, tuna, shark, and salmon.

Her research suggests that the fishing industry itself—along with our eating habits—may be in for a change. As oceans become more acidic, we may have to eat other species, shift aquaculture production to creatures that are less vulnerable, or move aquaculture operations to geographic areas that are less affected (all of which are likely to raise costs.)

In sum, Cooley says:

The [natural] communities are going to be very, very different. And different might be OK—maybe. There still is an ecosystem to be had. But a lot of the things that we really enjoy, that our communities depend on, are not going to be there. We may be able to find other awesome things about the new communities, but chances are, the options will be limited.

New Carbon Policies Required

While it’s prudent for people to be concerned about ocean acidification, it’s not sufficient, said Warren, of the Sustainable Fisheries Partnership. While it may take decades to moderate the effects of carbon dioxide that the oceans are absorbing today, there are things that can be done now to improve the situation: develop extensive monitoring networks, invest in ocean acidification research, get a handle on stormwater and other sources of pollution that flush nutrients into our waterways.

While the seafood industry is by no means monolithic, Warren said, it trends conservative politically. But the threats from ocean acidification are causing some in the industry to advocate for the only direct solution: reducing carbon dioxide emissions.

We work with people who cover the full range of opinions on that stuff. There are some people who think that Al Gore and the Tooth Fairy come from the same planet, but when they get their heads around this problem, some of those guys really go through a rethink.

As The Royal Society’s groundbreaking report on ocean acidification emphasizes, the only real way to prevent it from becoming more acute in the future is “decisive and significant action to cut carbon dioxide emissions.” Or, as Warren puts it:

You can use taxes, carbon markets, you can implement other controls, energy efficiency, increased use of cleaner power. There are many tools, but no one I think can credibly argue that you can do it without some kind of carbon policy. However you design it, or whatever axiom of change you bring to it, you’ve got to bring the actual flow of emissions under management.

In our next post, we’ll take a closer look at existing laws that could be used to address ocean acidification and what kinds of new policies will become necessary.

Essays in the Range blog are not written by High Country News. The authors are solely responsible for the content.

Originally posted at The Daily Score, a Sightline Institute blog.

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