In the summer, you may have to go 20 miles out to sea to find it, but close to the seafloor, near the edge of Oregon’s continental shelf, is a preview of the future: water as acidic as what the world’s oceans may be like in 50 to 100 years. “The future of ocean acidification is already here off the Ocean coast,” says Oregon State University oceanographer Francis Chan.
On a global basis, ocean acidity has increased about 30 percent since the start of the Industrial Revolution. So what, you might ask? The problem lies in basic chemistry: carbon dioxide (CO2) in the air mixes into seawater and, through a series of reactions, weakens calcium carbonate structures such as shells and coral reefs. In addition, recent studies suggest that increasing acidity (carbon dioxide forms carbonic acid in water) interferes with the ability of corals, sea urchins and other creatures to regulate functions from metabolism to reproduction.
Not all parts of the ocean are equally vulnerable, says Chan, an assistant professor of zoology. “Some places are going to be pretty resilient. They won’t feel the effects (of increasing acidity) for many decades or even a couple of hundred years. But there are other areas where people have said we really need to pay attention, that will be early warning systems, the canary in the coal mine.”
Two Sides of the Same Coin
The West Coast is one of those areas, and what makes it so vulnerable, says Chan, is the cold, deep water that swimmers in Oregon encounter during the summer. As north winds push warmer surface water away from the shoreline and out to sea, cold water comes up from offshore to replace it. This water tends to be more acidic and lower in oxygen than surface water, and as if adding insult to injury, it is loaded with nutrients that, under the right conditions, feed massive plankton blooms and set the stage for the so-called “dead zone” that has occurred regularly off Oregon since 2002.
Scientists define a dead zone as water with little oxygen, less than two parts per million to be precise (a condition known as “hypoxia”). As microbes chew away on dead plankton, they drop oxygen levels further still. “Hypoxia and acidification are opposite sides of the same coin,” says Chan. The microbes that feed on plankton blooms also release carbon-dioxide and make the water more acidic.
Since April 2009, Chan and colleagues in the Partnership for Interdisciplinary Studies of Coastal Oceans, or PISCO, have been measuring just how acidic this water gets. From a station just offshore of Strawberry Hill State Park, (“a long fly ball from the surf zone,” says Chan) to about 20 miles out, they have placed sensors that record CO2 (actually, pCO2, or the partial pressure of CO2 in the water, a measure of its concentration) and pH. They have found that upwelling water can contain from 150 to 1,450 microatmospheres, reaching levels nearly four times the global average. At the same time, pH levels can drop as low as 7.5. Such corrosive conditions can last for up to five months during the summer and fall.
Limits to Growth
Through PISCO, scientists are working to understand how sea urchins and mussels are responding to these variable conditions and how they might adapt in a warmer, more acidic future. “They already may be close to their acclimatization or adaptational capacity,” says Bruce Menge, OSU distinguished professor of zoology and lead scientist on the project, “and thus may have limited ability to respond to additional increases in CO2.”
Monitoring the West Coast’s pH “climate” is a high priority. To complement the Oregon data from Strawberry Point, scientists will establish stations off Southern and Northern California. In addition, researchers at UC Santa Barbara and the UC Davis Bodega Marine Lab will raise sea urchins and mussels in laboratory tanks, expose both larvae and adults to increasing CO2 and analyze differences in gene function. By using multiple sites, the project will evaluate the likely future for urchins and mussels across a wide range of ocean conditions.
“Here are organisms that we’ve studied for decades,” says Chan, “and we know the important roles they have in structuring the communities we see out there. We know they’re important players in the coastal ecosystem.”
“For the first time,” adds Menge, “we will be able to examine the genetics and ecology of these key organisms to see how populations that span over a thousand miles of coastline are coping with changes in ocean chemistry.”
Learn how PISCO is taking a collaborative approach to the science of ocean acidification.
In Shellfish on Acid, learn how OSU researchers are working with the Whiskey Creek Shellfish Hatchery to understand the effects of acidification on oysters, clams and mussels.
article courtesy of Terra Magazine
Photo by Pat Kight/Oregon Sea Grant