Increasingly acidic ocean threatens fish

COMPASS: Other points of view

December 9, 2009 

Alaska's rich fisheries are the mainstay of our coastal communities, providing for livelihoods we love and a way of life most Americans cannot even imagine. In Alaska, we pride ourselves on science-based fisheries management. So when scientists go out of their way to alert us to the dangers of ocean acidification, we need to really listen. And our elected officials need to act.

Last year 150 scientists from 26 nations posted a consensus statement called the Monaco Declaration stating they are "deeply concerned by recent, rapid changes in ocean chemistry and their potential within decades to severely affect marine organisms, food webs, biodiversity and fisheries."

The scientific findings are clear enough. The chemical composition of seawater is changing as a result of carbon dioxide emissions from the burning of fossil fuels. This is because the ocean naturally absorbs carbon dioxide from the air. When CO2 mixes with sea water a chemical reaction occurs that lowers the pH.

This has been going on since the beginning of time but the significant increase in global CO2 emissions is overwhelming the ocean's chemical equilibrium. The Monaco Declaration states that this has made the world's oceans 30 percent more acidic than they were prior to the industrial revolution. Scientists report that half of that increase has occurred in the last 30 years.

Most of us aren't chemists, but it's not hard to understand that a more acidic ocean will change what can live there. The pH scale for measuring how acidic or alkaline the water is resembles the Richter scale for measuring earthquakes. Sea water is generally alkaline -- or at the middle of the scale. The more acidic the ocean becomes, the less calcium carbonate is available to marine life for building shells and skeletal structures. Think corals, crabs, clams, certain zooplankton.

One of the first casualties of increasing acidity in Alaska's waters is expected to be pteropods -- tiny marine snails that are eaten by salmon, halibut, pollock and herring. Pteropods cannot form their calcium carbonate shells under conditions which are too acidic.

High latitude waters like the North Pacific are especially likely to become corrosive because cold water absorbs more gases and therefore is a better sink for atmospheric CO2. Dr. Jeremy Mathis, oceanographer at University of Alaska Fairbanks, said to the press on Aug. 11, "The increasing acidification of Alaska waters could have a destructive effect on all of our commercial fisheries. This is a problem that we have to think about in terms of the next decade instead of the next century." Shellfish may be directly impaired by reductions in calcium carbonate. Fish will be affected indirectly as acidification harms their prey, like pteropods or other shell-forming zooplankton.

Whether you are a subsistence, sport or commercial fisherman, when it comes to the dangers of ocean acidification, we're all in the same boat. Life as we know it cannot adapt to an acid ocean. So we need our elected leaders to deal with the cause. The future of our fisheries depends on swift and decisive legislation to curtail CO2 emissions before it's too late to turn back the clock.

The cost of inaction will be born by our fisheries and our children's livelihoods. Surely if we can send a man to the moon and bring him home safely, we can figure out how to shift our economy away from a heavy dependence on fossil fuels and move toward a renewable energy future. There are jobs in clean energy. So let's get going. What choice do we really have?


Dave Kubiak is a retired Kodiak teacher and resident fisherman since 1964.

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