“The geological record suggests that the current acidification is potentially unparalleled in at least the last 300 million years of Earth history and raises the possibility that we are entering an unknown territory of marine ecosystem change.”
— Jelle Bijma, research scientist, October 2013
As if there were not already enough to worry about … now we learn our oceans are acidifying. That poses a grave danger to the entire marine ecosystem, including many species humanity relies on as a source of protein. Most of the world’s saltwater shellfish industry, for example, may be wiped out this century.
The reason the pH level of the world’s oceans is declining at an unprecedented rate is the same reason the Earth is heating up: human activities. We burn ungodly amounts of coal, oil and gas, and that is polluting our atmosphere with carbon dioxide.
“Atmospheric CO2 has increased more than 100 (parts per million) since the beginning of the Industrial Revolution,” according to Jim Barry, a scientist at the Monterey Bay Aquarium Research Institute. Atmospheric CO2 today is roughly 398 ppm. It is increasing approximately 2 ppm per year. At that pace, it will reach 500 ppm in 2065.
Much of the global increase in CO2 in the atmosphere is absorbed by the oceans. That dissolution of carbon increases hydrogen ion concentration, acidifying seawater.
According to Scott Doney, a scientist at the Woods Hole Oceanographic Institution, “ocean pH has fallen by about 0.1 pH unit from preindustrial times to today.”
That does not sound like much over a period of hundreds of years, but keep in mind that pH is on a logarithmic scale. Doney explains that 0.1 pH is “equivalent to about a 26 percent increase in the ocean hydrogen ion concentration.”
“If we continue on the expected trajectory for fossil-fuel use and rising atmospheric CO2, pH is likely to drop by 0.3-0.4 units by the end of the 21st century and increase ocean hydrogen ion concentration (or acidity) by 100 to 150 percent above what it was in preindustrial times.”
One of the leading scientists studying the effects anthropogenic climate change has on marine life is professor Eric Sanford of the UC Davis Bodega Marine Laboratory.
In January, Sanford’s research on the Olympia oyster was featured in a story in The Economist magazine. According to the article, Sanford and his colleagues “looked in the laboratory at how CO2-enriched seawater affects the growth of Olympia oysters, and how that, in turn, affects the mollusks’ attractiveness to predators — specifically carnivorous snails called Atlantic oyster drills.”
What Sanford and his colleagues found was that oysters raised in water with a pH level equal to that expected at the end of this century were 30 to 40 percent smaller at maturity than those raised in water with the pH our oceans have today. Compounding the problem is that snails raised in the more acidic water ate almost 50 percent more oysters than snails raised in normal seawater.
In an email interview I asked Sanford if ocean acidification is a threat to our entire shellfish industry, here in California and elsewhere?
He told me that is a definite worry. “There is growing concern that ocean acidification poses a significant threat to the shellfish industry,” Sanford wrote. “Scientists and commercial shellfish growers are concerned and are looking closely at this problem.”
As our oceans acidify, I wondered if oysters and other threatened species would be able to adapt to their new environment.
Sanford told me, “Ocean acidification is expected to develop too rapidly during this century for new mutations to arise and help oysters adapt.”
The American seafood industry adds $50 billion to our gross domestic product. If by 2100 most commercial shellfish species are extinct, the U.S. economy, worth $1.57 trillion today, can survive. However, coastal communities that rely on fisheries may be wiped out. Mollusks (including oysters, clams and mussels) account for two-thirds of the value of America’s marine aquaculture, according to the National Oceanic and Atmospheric Administration.
Globally, marine seafood is worth about $300 billion per year. Fish and shellfish are a primary source of animal protein for many countries. A great risk, even to animals that can survive in more acidic water, is that the food they eat will no longer exist. Where they now feed could become an oceanic dead zone.
According to Debora Iglesias-Rodriguez of the National Oceanography Centre of the University of Southampton in the U.K., “The rate of human-driven ocean acidification is about 100 times faster in the surface ocean than that experienced by marine ecosystems globally for tens of millions of years.
“Different ecosystems will respond differently,” Iglesias-Rodriguez writes. “In some ecosystems, such as coral reefs, the calcifying organisms form the fundamental architecture of the ecosystem. So if they disappear, the ecosystem could disappear.”
As long as we emit carbon dioxide at the present rate, the health of our oceans will decline and the damage to marine life will be irreversible on a human time scale.
The only solution to the problem of atmospheric CO2 is a hefty global tax on carbon emissions. We need to incentivize polluters to burn less coal and oil and substitute with clean energy. In the longer term, a carbon tax will incentivize entrepreneurs to develop new technologies to capture CO2 before it devastates our atmosphere and oceans.
— Rich Rifkin is a Davis resident; his column is published every other week. Reach him at [email protected]