Global warming grabs headlines, but CO2 emissions are also impacting our oceans... and the effects could be irreversible
June 18, 2009
Imagine the ocean stripped bare: no coral, no crabs, no mussels, no clams—and ultimately no fish. What would that be like? It's hard to say, says Rusty Brainard, chief of the Coral Reef Ecosystems Division at the National Oceanic and Atmospheric Administration's Pacific Islands Fisheries Center, though it could be an environment in which jellyfish and other, similar species predominate. But good luck catching a fish. You'd be hard-pressed to find bait, anyhow.
It's a nightmarish scenario, but, Brainard says, it could become reality in the next 35 to 100 years. That's the range of time in which experts estimate that atmospheric CO2 will double if we don't drastically change our ways. And most scientists believe high CO2 levels are altering the fundamental chemistry of our oceans.
It's kind of like that science fair project involving a baby tooth left overnight in a petri dish full of Coca-Cola, except that the effects are potentially catastrophic, especially in places like Hawaii, where, in addition to their environmental and cultural importance, coral reefs generate an estimated $360 million dollars a year. One environmental lawyer called ocean acidification "global warming's evil twin," but the phenomenon is still largely unknown outside scientific circles.
One man wants to change that. After reading Elizabeth Kolbert's November 2006 New Yorker piece titled "The Darkening Sea," retired teacher Sven Huseby set out to find the truth behind ocean acidification. His quest took him all over the planet and led to conversations with top researchers in the field. What he discovered was not pretty. Huseby's travels are documented in A Sea Change: Imagine a World Without Fish, a film screening Tuesday, June 23 as part of Maui Ocean Center's Sea Talk series.
"It's kind of shocking how little we know about this topic," says Brainard. The term itself was coined a mere six years ago, according to Kolbert, by climate scientists Ken Caldiera and Michael Wickett.
Yet there is an overwhelming consensus that the pH levels of our oceans are dropping, becoming more acidic at an alarming rate, and that carbon dioxide emissions—which result from the burning of fossil fuel—are the culprit.
"From [the existing body of research] what we see is very scary," says Brainard.
Billions of tons of CO2 are pumped into the atmosphere each year. The oceans absorb an estimated 25 to 33 percent of that. From a global warming standpoint, Brainard says, that's a good thing, as it means less CO2 gets trapped in the atmosphere, which means a slower rate of global warming.
However, for our oceans and the unfathomably diverse and vast life forms that call them home, the estimated 118 billion metric tons (the equivalent of 118 billion VW Beetles) of carbon dioxide that the oceans have absorbed since the start of the Industrial Revolution have taken their toll—and scientists say there's much, much more to come.
In a 2007 report, the United Nations' Intergovernmental Panel on Climate Change (IPCC), a consortium of the world's top climate change researchers, estimated that oceanic pH levels have dropped by 0.1 pH units. It doesn't seem like much, but Kolbert points out in "The Darkening Sea" that the pH scale is logarithmic, much like the Richter scale. So it's not an imperceptible change.
Lizzy McLeod, a Climate Adaptation Scientist with The Nature Conservancy's Asia-Pacific Division says that ocean acidification is bad news for marine life, namely corals and other life forms that rely on a biological process called calcification.
"This is huge," she says, citing a 2008 paper published in Science titled "Coral Reefs Under Rapid Reefs and Ocean Acidification."
The study found a 13 percent reduction in growth rate for coral in the Great Barrier Reef, the world's largest coral reef. Accurate measurements are possible because corals grow like trees—with rings to tell their story.
So how, exactly, does water with a lower pH spell disaster for calcifying marine life? As the oceans absorb carbon dioxide, CO2 molecules combine with seawater molecules to form carbonic acid molecules. Multiple studies show that this reduces the availability of aragonite, a substance that's vital in the calcification process.
Coral, clams, echinoderms, starfish and tiny zooplankton called pteropods are among tens of thousands of calcifiers.
Scientists from NOAA, the United States Geological Survey, the Hawaii Institute of Marine Biology and many other organizations have studied the impacts of acidification on a handful of calcifiers, including crustose coralline algae, a vital component to coral reefs. USGS scientist Ilsa Kuffner, UH Oceanographer Andreas Andersson and others released results of a study in 2007 that took place at Coconut Island, Kaneohe Bay. In open air mesocosms (tanks) they decreased the pH of some of the tank's water using diluted hydrochloric acid to induce the projected ocean pH.
"The recruitment rate and growth of crustose coralline algae were severely inhibited in the elevated carbonate mesocosms," the study read.
"Most of the organisms we look at suffer very badly," Brainard adds.
Pteropods are among the most studied organisms in terms of acidification's impacts. As a series of photographs over time dramatically demonstrates in A Sea Change, their shells begin to dissolve within 48 hours of the water reaching a certain level of acidity. It's a matter of days before they dissolve almost completely. This is bad for the marine food web and fisheries alike, as pteropods are an important part of the diets of fish like salmon.
McLeod says that the further you get from the Equator, the more difficult it is for calcifiers to make their shells and skeletons, because the oceans are less saturated with aragonite. Reefs strewn along coral's latitudinal limits—30 degrees north and south of the equator—are most vulnerable to acidification because of the scarcity of aragonite.
This paints a dire picture, but many scientists say it's not too late to reduce the impacts of acidification. "It's not all gloom and doom," McLeod says.
Last year, for example, The Nature Conservancy convened a workshop in Hawaii to discuss impact reduction strategies. The result was "The Honolulu Declaration on Acidification and Reef Management," a series of policy and management recommendations. It stressed not only the importance of a reduction in carbon emissions, but also increased protection of our reefs—things as simple as reducing reef damage from divers' fin kicks.
The federal government recently passed the FOARAM (Federal Ocean Acidification Research and Monitoring) Act, which grants NOAA and the National Science Foundation $96 million over the next 10 years for ocean acidification research.
The abundance of the sea makes it easy to forget how fragile the balance is. We may not know what we've got until it's gone—but we can't afford to wait that long. MTW
A Sea Change: Imagine a World Without Fish will screen Tuesday, June 23 at 5:30pm at the Maui Ocean Center in Maalaea. For more info and to reserve a space, call 270-7000 or visit www.mauioceancenter.com
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