It’s well known that burning fossil fuels in the form of coal, oil, and natural gas releases carbon dioxide (CO2) into the air. Less understood is that a quarter of this carbon dioxide—about twenty trillion pounds, every year—is absorbed by oceans. Writing for the Seattle Times Craig Welch invited us to “imagine every person on earth tossing a hunk of CO2 as heavy as a bowling ball into the sea. That’s what we do to the oceans every day.” As Welch and others reported, this carbon dioxide is changing the ocean’s chemistry faster than at any time in human history, in ways that have potentially devastating consequences for both ocean life and for humans who depend on the world’s fisheries as vital sources of protein and livelihood.
When CO2 mixes with seawater, it lowers the pH levels of the water, making it more acidic and sour. In turn this erodes some animals’ shells and skeletons and robs the water of ingredients that those animals require for healthy development. Known as ocean acidification, this phenomenon, Welch wrote, “is helping push the seas toward a great unraveling that threatens to scramble marine life on a scale almost too big to fathom, and far faster than first expected.”
The impacts of ocean acidification have been most pronounced in the Arctic and Antarctic, because cold, deep seas absorb more carbon dioxide. Julia Whitty reported for Mother Jones that we’ve enjoyed a free ride so far: “The ocean has swallowed our atmospheric carbon dioxide emissions and slowed global warming during the past few critical decades while we dithered in disbelief.” Now, however, the average acidity of surface ocean waters worldwide is more than 30 percent greater than at the start of the Industrial Revolution. Whitty’s coverage draws on findings from the 2013 Arctic Ocean Acidification Assessment. The Arctic Ocean is especially vulnerable, she wrote, because short, simple food webs are characteristic of Arctic marine ecosystems. “Energy is channeled in just a few steps from small plants and animals to large predators like seabirds and seals.” As a result, the integrity of the entire system depends heavily on keystone species, including pteropods (also known as sea butterflies) and echinoderms (more commonly known as sea stars and urchins). Although larger creatures like birds and mammals may not be directly affected by ocean acidification, Whitty reported, they will be indirectly affected if their food sources “decline, expand, relocate, or otherwise change in response to ocean acidification.” As ocean acidification impacts the abundance, productivity, and distribution of Arctic marine species, these changes are likely to affect the culture, diet, and livelihoods of indigenous Arctic peoples and other Arctic residents.
The impacts of ocean acidification are not limited to the Arctic and Antarctic Oceans, however. As Eli Klintisch reported for Science magazine, researchers have documented impacts to tiny marine snails in the Pacific Ocean along the west coast of North America. Normally pteropods have smooth shells. As Klintisch described, a study led by Nina Bednaršek of the National Oceanic and Atmospheric Administration (NOAA) and her colleagues found that pteropods from thirteen coastal sites between Washington state and southern California had pitted shells. In an article published in the Proceedings of the Royal Society B, Bednaršek and her colleagues reported that more than half of the shells they collected showed signs of dissolving, which made the shells look like “cauliflower” or “sandpaper.” These findings were consistent with previous laboratory studies, which showed that, as seawater becomes more acidic, the change disrupts the shell formation process in young pteropods and dissolves already formed shells in mature ones. Previous studies, Klintisch reported, document that shell damage makes it harder for pteropods and other invertebrates to “fight infection, maintain metabolic chemistry, defend (themselves) against predators, and control buoyancy.”
The impacts of the pteropods’ fast dissolving shells are difficult to predict, but they could be profound. On one hand, pteropods are among the most abundant organisms on the earth; on the other hand, like other small creatures at the bottom of the ocean food chain that have not been closely studied, their role in the ecosystem is not completely understood. We do know that the pteropods examined in the Royal Society study are a key food source for pink salmon. Pink salmon, in turn, are crucial to the North Pacific fishery.
Scientists initially believed that fish would not be directly affected by ocean acidification, but recent research indicates otherwise. From clownfish off the coast of Papua New Guinea (remember Nemo?) to walleye pollock (got fish sticks?) scientists have found that exposure to high levels of carbon dioxide scramble fish’s sense of smell, hearing, and sight. Though fish are excellent at altering their blood chemistry to accommodate changing seas, elevated CO2 levels disrupt many fish’s brain signaling. Baby clownfish exposed to high levels of CO2 were five times more likely to die when placed back in the wild. At first scientists thought clownfish were unusually vulnerable to high levels of CO2, but subsequent research showed that many reef fish are similarly affected. Early results, Craig Welch reported, suggest that walleye pollock experience some of the same behavioral problems as reef fish when exposed to high levels of CO2. That, in turn, raises concerns about the North Pacific’s $1 billion-a-year pollock fishery, which accounts for half the nation’s catch of fish.
As Welch wrote in his “Sea Change” article for the Seattle Times, “The most-studied animals remain those we catch. Little is known about the things they eat.” This points to another problematic dimension of ocean acidification. Despite the potential magnitude of the problem—remember, ocean acidification is changing the chemistry of the world’s oceans faster than ever before, and faster than the world’s leading scientists had predicted—there is little funding for research on ocean acidification and its affects. As Welch reported, “Combined nationwide spending on acidification research for eight federal agencies, including grants to university scientists by the National Science Foundation, totals about $30 million a year—less than the annual budget for the coastal Washington city of Hoquiam, population 10,000.”
Julia Whitty, “10 Key Findings From a Rapidly Acidifying Arctic Ocean,” Mother Jones, May 7, 2013, http://www.motherjones.com/blue-marble/2013/05/arctic-ocean-rapidly-getting-more-acidic.
Craig Welch, “Sea Change, The Pacific’s Perilous Turn,” Seattle Times, September 12, 2013, http://apps.seattletimes.com/reports/sea-change/2013/sep/11/pacific-ocean-perilous-turn-overview.
Eli Kintisch, “Snails Are Dissolving in Pacific Ocean,” ScienceNOW, May 1, 2014, http://news.sciencemag.org/biology/2014/05/snails-are-dissolving-pacific-ocean.
Student Researcher: Amanda Baxter (Sonoma State University)
Faculty Evaluator: Elaine Wellin (Sonoma State University)