Ocean Acidification Primer

Sunset at Hug Point, Oregon. Photo by R. Emanuel, OSU.

Sunset at Hug Point, Oregon. Photo by R. Emanuel, OSU.

The December 2009 (Volume 22, Number 4) issue of Oceanography has just published an excellent primer on ocean acidification. NOAA researchers from the Pacific Northwest are some of the authors.

To quote the authors (Doney et al.) of this introductory piece directly:

“The cumulative human CO2 emissions over the industrial era now amount to close to 560 billion tons. A little less than half of this anthropogenic CO2 remains in the atmosphere—certainly enough to be of grave concern as a greenhouse gas leading to climate change. The remainder is, at present, removed in roughly equal parts into the ocean and by land  vegetation. Revelle and Suess (1957) wrote a prophetic view of our perturbations to the global carbon cycle: Thus human beings are now carrying out a large scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future—a sentiment that may be especially true for ocean acidification.”

The entire edition covers this topic quite thoroughly: http://tos.org/oceanography/issues/current.html.

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Ocean pH spells more trouble for oysters and oystermen

Many months ago, I posted on the topic of Vibrio tubiashii infesting local waters and jeopardizing the viability of Whiskey Creek Shellfish Hatchery in Netarts, OR.  Whiskey Creek supplies larvae for hundreds of West Coast oyster producers.  V. tubiashii is a little understood bacteria that thrives in deep waters, and seems to tolerate a lower pH. After nearly a year of work with Oregon State University and others, the hatchery installed ultraviolet lights and other sterilization procedures for its Netarts Bay intake water that successfully lowered the pathogen counts in their tanks.

Whiskey Creek Shellfish Hatchery, Netarts, Oregon. Photo by R. Emanuel

Whiskey Creek Shellfish Hatchery, Netarts, Oregon. Photo by R. Emanuel

When I visited the owners late this spring, a new situation had arisen: lowered pH in the water was also killing off or weakening the microscopic larvae. With lowered pH levels–and thus higher acidity, the young creatures cannot construct shells and successfully move into another stage as “seed” attached to a hard substrate (or surface).  After this second, serious setback, hatchery owner Sue Cudd was openly pessimistic about the future of the hatchery or the shellfish business, at least her’s in Oregon.

According to a June 14th article in the Seattle Times, Washington State shellfish growers seem to be experiencing similar problems related to ocean water pH.  The evidence points to increased carbon dioxide levels in sea water off the entire Pacific Northwest Coast.

As Craig Welch reports:

Now, as the oyster industry heads into the fifth summer of its most unnerving crisis in decades, scientists are pondering a disturbing theory. They suspect water that rises from deep in the Pacific Ocean — icy seawater that surges into Willapa Bay and gets pumped into seaside hatcheries — may be corrosive enough to kill baby oysters.

If true, that could mean shifts in ocean chemistry associated with carbon-dioxide emissions from fossil fuels may be impairing sea life faster and more dramatically than expected.

Recent work by researchers such as Zeebe et al. 2008 and Orr et al. 2005 indicate that atmospheric CO2 emissions are driving carbonic acid levels in sea water to historic highs (in human, not geologic terms). Carbonic acid is produced when gasseous carbon dioxide is dissolved in water. Though only midlly corrosive, carbonic acid reduces the most common and accessable dissolved form of calcium carbonate: aragonite.  Aragonite is the basic building block of shellfish shells.  The lack of aragonite, in turn, reduces the ability for shellfish to grow and produce new layers of calcium carbonate shell. In larvae, which in most organisms start out shelless, the acidic environment and lack of aragonite prevents any shell production, dooming the young to a short existence or a weakened state where they may be more vulnerable to predators.

At present, we’re at the stage of seeing anecdotal evidence that backs up modeling and lab-based research.  This is an important trend, however–one that we should keep our eyes on as it develops in the next few years.

Vibrio tubiashii, hypoxia, and the oysters on your plate…

West Coast media outlets (minor and major) have honed in on the mysterious upsurge of Vibrio tubiashii in shellfish beds, larvae producers, and coastal waters. The bacterium preys on oyster and other shellfish larvae, with toxins weakening and eventually killing the organism.  One important clue may be that Vibrio is responding to climate-induced changes in coastal waters.  Below is the synopsis from the Monday, June 9th edition of the Oregonian (written by Michael Milstein).

Pacific oystersAn invisible microbe that thrives in warm ocean water has undermined the Northwest’s prized oyster supply, killing billions of young larvae that mature into the succulent shellfish known across the world.

The bacterium, Vibrio tubiashii, is related to another species that can sicken people who eat raw shellfish. This one doesn’t bother people — it kills shellfish in their larval stage, before they latch onto rocks to grow.

An explosion of the microbe late last summer shut down an Oregon shellfish hatchery that is one of the largest on the West Coast, supplying larvae to about 70 oyster growers the way seed companies provide crop seed to farmers.

The microbe also is the likely culprit in the disappearance of recent generations of wild oysters from usually prolific estuaries such as Willapa Bay on the southern Washington coast.

“We’re in a state of panic,” said Robin Downey, executive director of the Pacific Coast Shellfish Growers Association, based in Olympia. “There is no other word for it.”

The crisis has the attention of local and state leaders, including the governor. And scientists have rushed to devise filters that can strain the lethal bacterium out of water flowing through hatcheries.

Researchers say the rise of bacteria might be tied to the same unusual ocean conditions — possibly connected to global climate change — causing the suffocating “dead zones” that have appeared off the Oregon coast in recent summers.

The bacteria, long known in coastal waters at low levels, seem to have taken off in the same areas and about the same times as the dead zones. But it’s unclear what conditions have caused the bacteria to thrive.

“It’s safe to say it’s probably all of Oregon and parts of California and Washington,” said Ralph Elston, a veterinarian with Aquatechnics in Sequim, Wash., who works with shellfish hatcheries.

Oysters grow for a few years before they’re big enough to eat, so those showing up in restaurants now predate the recent bacterial boom that killed young oysters. Growers predict the loss of those generations of oysters will shrink supply and probably drive up prices later this year.

“It’s going to have some major effects on the industry in the next year or so,” said Bill Taylor of Taylor Shellfish Farms, which hatches and grows oysters on Washington’s Hood Canal and also has been hammered by the bacteria this spring. “There’s not going to be enough marketable oysters to sell.”

Besides oysters, geoducks grown farther north on the West Coast are at risk. Clams and mussels seem less vulnerable, though fisheries officials have noticed a lack of young razor clams along some areas of the coast.

Hatcheries sound alarm

State biologists don’t monitor wild shellfish as they do key fish species such as salmon. Shellfish hatcheries, which grow larvae in water pumped from the ocean, were the first to realize that young oysters were dying.

“The hatcheries are really the canary in the mine shaft,” said Chris Langdon, a professor at Oregon State University’s Hatfield Marine Science Center in Newport. “There hasn’t been monitoring of this bacteria on large scales.”

West Coast growers produce more than $100 million worth of commercial shellfish each year, with oysters by far the largest share. Cultivated oysters are mainly Pacific oysters, originally imported from Japan and different from native West Coast oysters.

But researchers said the bacteria probably also are affecting wild shellfish.

Oyster larvae suddenly disappeared from Willapa Bay last year, said Alan Trimble, a University of Washington researcher who works at the bay. He suspects the bacteria contributed to poor reproduction of native oysters and razor clams in bays and coastal beaches.

“When the larvae die in the water column, it isn’t just Pacific oysters; the others disappear also,” he said in an e-mail from Namibia, where he is on leave.

That could affect the rest of the marine food chain, because many other forms of marine life eat young shellfish.

Business shuts down

Late last summer, the bacteria multiplied to levels that shut down Whiskey Creek Hatchery on Netarts Bay. Tiny oyster larvae that usually swim busily under a microscope instead looked shrunken and feeble as a toxic enzyme secreted by the bacteria destroyed them, said Sue Cudd, who, with her husband, Mark Wiegardt, runs the hatchery.

The hatchery usually produces many billions of oyster larvae each year but couldn’t produce any once the bacteria invaded in August. Wiegardt and Cudd had nothing to send to growers that depend on them for their seed stock.

“We have the weight of a lot of people depending on us,” Wiegardt said. “If we don’t figure out this problem, people are going out of business.”

The hatchery burned through its reserve funds and was about to give up. “I had nowhere to go,” Cudd said.

Then the couple found help from the Hatfield Marine Science Center, which had similar trouble at its hatchery in 2005. Researchers there developed a filtration system that uses a combination of ultraviolet light and other methods to remove the bacteria from water entering the hatchery.

Other shellfish growers, many of them the hatchery’s customers, donated money to hire Alan Barton, a former Hatfield researcher, to design a similar system at the Whiskey Creek hatchery.

That’s now up and running at a cost of about $180,000, although it handles only enough water for the hatchery to produce about half its normal oyster crop of close to 50 million larvae a day. It will cost an additional $80,000 to expand the system to provide a full water supply.

“This affects a huge West Coast oyster industry that goes all the way to the oysters on your plate,” said Mark Labhart, a Tillamook County commissioner who is trying to help the hatchery find financial assistance to boost the filter system.

Finding out why

Concentrations of Vibrio have spiked as high as 1 million in 1 milliliter of water — at least 100 times usual levels — and remain higher than normal, Barton said. The bacterium also took off in 1998, when an El Nino pattern warmed coastal waters, though not nearly as severely as it has recently, Elston said.

He suspects some of the same factors Oregon State researchers have connected with dead zones along the coast: strong but intermittent upwelling of deep water that pushes rich nutrients toward the surface.

Langdon said the deep water also might be a source of the oyster-killing bacteria.

Though the deep water is cold, its nutrients could combine with warm surface waters to nourish the microbes, Elston said. “The conditions were just absolutely optimal for a bloom.”

The bacteria might now have collected in the sediments of inlets and bays, and Wiegardt can’t help but wonder what’s happening to wild shellfish in the oceans. “I don’t think it’s just about us anymore. It’s about what’s going on in the marine environment.”

Six Years of California Current Hypoxia Climate-Related and Possible New Trend

For the communities on the North Coast that are fishery or sea-life dependent, comes some disturbing news out of researchers at the Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO) which includes OSU. This particular posting is a reminder that climate change impacts cannot be easily predicted. The original OSU press-release reposted below can be found here.

Editor’s Note: Digital photographs to illustrate this story can be obtained at the PISCO web site at http://www.piscoweb.org/outreach/topics/hypoxia.

CORVALLIS, Ore. – A review of all available ocean data records concludes that the low-oxygen events that have plagued the Pacific Northwest coast since 2002 are unprecedented in the five decades prior to that, and may well be linked to the stronger, persistent winds that are expected to occur with global warming.

In a new study to be published Friday in the journal Science, researchers from Oregon State University outline a “potential for rapid reorganization” in basic marine ecosystems and the climatic forces that drive them – and suggest that these low-oxygen, or “hypoxic” events are now more likely to be the rule rather than the exception.

“In this part of the marine environment, we may have crossed a tipping point,” said Jane Lubchenco, the Wayne and Gladys Valley Professor of Marine Biology at OSU, and the lead scientist for PISCO, the Partnership for Interdisciplinary Studies of Coastal Oceans.

“Levels of oxygen in the summertime have suddenly become much lower than levels in the previous 50 years,” Lubchenco said. “And 2006 broke all records, with parts of the shallow shelf actually becoming anoxic, meaning that they lacked oxygen altogether. We’ve never seen that before.”

The rapid and disturbing shift of ocean conditions in what has traditionally been one of the world’s more productive marine areas – what’s called the California Current Large Marine Ecosystem – has garnered much attention in recent years, also raising questions about whether it has happened before, and what is causing it.

“People keep asking us, ‘Is this situation really all that different or not?’” Lubchenco said. “Now we have the answer to that question, and it’s an unequivocal ‘yes.’ The low oxygen levels we’ve measured in the last six years are abnormally low for our system. We haven’t seen conditions like this in many, many decades, and now with varying intensity we’ve seen them in each of the last six summers.”

In these events, water oxygen levels have repeatedly reached hypoxic levels, below which most marine animals suffocate or are severely stressed if they cannot escape the area. If oxygen levels drop to zero, most animals die. The massive 2006 event covered at least 3,000 square kilometers, lasted for four months, and occupied up to 80 percent of the water column in shallow shelf areas, the report said. Fish either died or fled these areas, thousands of crabs died, and marine seafloor life that could not move faced almost total mortality. Recovery has been slow.

It’s less certain why this is happening, but the events are completely consistent with global climate change, the OSU researchers say.

“There have always been unusual weather events, such as hurricanes, droughts, and changes in wind patterns,” said Jack Barth, an OSU professor of physical oceanography and a lead scientist with PISCO. “So it’s difficult to prove that any one event is caused by global warming. Having said that, we expect global warming to generally cause stronger and more persistent winds. These winds contribute to the hypoxic events by increasing plankton production and holding low-oxygen water on the continental shelf for longer periods.

“At this point,” Barth added, “I’d be surprised if this trend towards hypoxic events didn’t continue.”

Francis Chan, a marine ecologist with OSU and PISCO, conducted a survey of all known records of oxygen levels on the Oregon continental shelf over the last 60 years, with measurements taken by research cruises and ocean-going vessels from more than 3,000 stations.

“The data make it pretty clear that the recent conditions are unprecedented during any period that has been measured,” Chan said. “We’re now seeing very low-oxygen water, lasting for long periods, and closer to shore than at any time in more than 50 years.”

That long period of time included several El Nino and La Nina events, possible suspects in any change of Pacific Ocean conditions, and also shifts in the Pacific Decadal Oscillation, another player in near-term climate trends. None of those appeared to have any correlation to the hypoxic events.

Hypoxic conditions in ocean waters – often popularly called “dead zones” – are usually associated with serious nitrate loads or other nutrient pollution, such as in the Gulf of Mexico or Chesapeake Bay. Pollution-caused hypoxic zones are found with much less frequency in regions where significant upwelling occurs – a process that is usually beneficial to productive marine food webs.

“Coastal upwelling ecosystems occupy only about 1 percent of the ocean surface area, but they produce about 20 percent of global fishery production,” Lubchenco said. “These areas have historically been highly productive. The appearance or increase in severity of hypoxia in these ecosystems would be cause for concern.”

Some other areas of the world bear more similarity to the recent situation off the Pacific Northwest, such as the Benguela Current off South Africa and Humboldt Current off Chile. They historically have had hypoxic conditions before – which may be getting worse.

“The Namibian system in the past decade seems to be seeing lower oxygen levels and more frequent hypoxic events than it had previously,” Barth said. “Historically it has even more extreme upwelling than we have in the Pacific Northwest, and more frequent marine life die-offs.”

A concern, researchers say, is whether that system is a harbinger of the future for the Pacific Northwest.