Acidification threatens wide swath of sea life
No one knows how — or when — ocean acidification will impact Puget Sound's sea life. But scientists around the globe are finding corrosive water can alter marine systems in strange, subtle and sometimes worrisome ways.
Seattle Times environment reporter
Signs environmental upheaval may be under way:
Sea snails: Tiny sea snails called pteropods, which make up 60 percent of the diet for Alaska's juvenile pink salmon, essentially dissolve in corrosive waters. Some microscopic plankton also are important fish food, and some are highly susceptible to corrosive water.
Clownfish: Scientists in Australia found that larval clownfish and damselfish exposed to corrosive waters tended to follow the scent of predators and were five to nine times more likely to die.
Killer whales: The ocean will absorb less background noise — in effect, become noisier — when pH levels drop by even small amounts. Research hasn't been done to detail what impact, if any, that might have on marine mammals such as orcas that rely on biosonar.
Giant squid: Scientists say the giant squid, also known as the Humboldt squid, typically found at depths of 660 to 2,300 feet, grow lethargic when subjected to acidified waters.
Sea urchins: Purple sea-urchin larvae exposed to acidifying waters were smaller, "stumpier" in shape and had less skeletal mass.
Oysters: Wild Pacific oysters have not reproduced in Willapa Bay for six years. Scientists suspect acidifying water, rising from the deep in coastal "upwelling" events, is helping wipe out juvenile oysters before they can grow.
Seagrass: All five species of seagrass that have been studied were found to thrive in increasingly corrosive waters.
Several years after oyster larvae around the Northwest began dying by the billions, hatcheries like this one are again ramping up production.
But that's just because they've learned to avoid pumping in problem seawater.
Few know better than Northwest oyster growers that ecological upheaval is still rattling their industry — and that it may be a sign of greater marine-world shifts to come.
Pacific oysters in the wild on Washington's coast haven't reproduced in six seasons. Scientists suspect ocean-chemistry changes linked to the fossil-fuel emissions that cause global warming are helping kill these juvenile shellfish.
The oceans are becoming more acidic, and that corrosive water is finding its way into Puget Sound.
No one knows how it will impact the Sound's sea life. But scientists in laboratories around the globe increasingly find corrosive water can alter marine systems in strange, subtle and sometimes worrisome ways.
Waters with a mildly lower pH can change the metabolism of squid, making them more lethargic. The increase in acidity can dramatically alter the shape of sea-urchin larvae. Corrosive waters have been shown to foul up the way some young fish sniff out prey — convincing them it's safe to move directly toward predators. Some young brittle stars and barnacles start dying early in these waters, while larval tunicates, fist-size bloblike sea creatures, thrive and develop faster.
Acidification also can make marine waters noisier, which may have implications for killer whales and other animals that use sonar.
Push to learn more
Researchers are scrambling to expand lab facilities in the San Juan Islands and at NOAA Fisheries in Montlake. They hope to predict the reactions of Northwest creatures — from algae and plankton to fish, clams, crab and bacteria.
"What I'm most worried about is the bottom of the food chain," things such as plankton and other small sea creatures, said John Guinotte, a marine biogeographer with the Marine Conservation Biology Institute in Bellevue. "We've got some of the lowest pH levels found anywhere, but we don't have any idea what the biological impacts are."
The marine environment is complex and resilient. New impacts could appear in a few years — or decades. In the meantime, it's hard to re-create a world in constant flux, with its shifting currents and warm- and cold-water cycles and acidity levels that shift with photosynthesis and marine-life respiration.
"You can't really try to mimic evolution," said Victoria Fabry, a professor of biological sciences at California State University, San Marcos. "In a sense, the world is in the middle of that experiment right now."
But the oyster industry's misfortune has given science a leg up.
Oysters' fate up to wind?
In their early stages, young oysters look like mud.
In Dabob Bay, Taylor Shellfish hatchery technician Jason Brush pulled some 10 million microscopic larvae from a tank, strained the black goo and packaged them for sale.
The hatchery is having one of its best years, but people here attribute that to luck.
The facility grows oysters in seawater drawn off Dabob's surface. But this year, south breezes have kept corrosive waters down deep, far below where Taylor slurps up its water.
"We basically think we're being saved by the wind," said chief hatchery scientist Benoit Eudeline.
The pH of the world's oceans typically measures a slightly alkaline 8.1. But scientists long have predicted climate change would make waters more corrosive as carbon dioxide taken up by oceans dissolves.
But only in trying to understand why oyster-growing was falling apart did oceanographers figure out what made the West Coast unique: Waters down deep were acidifying more than anyone thought and were coming closer than anyone expected to shore, where most sea creatures live.
Deep, cold water typically carries more carbon dioxide than surface waters, but northwest winds regularly push those waters up along the coast in "upwelling" events. In some cases, that brings water to shore with a pH as low as 7.7, lower than anything scientists expected to see for decades.
"Nobody had thought about those upwelling events," said NOAA oceanographer Richard Feely. "They didn't predict any impacts along the coast until we observed them."
Scientists have linked oyster die-offs to this cold-water upwelling. They knew acidifying waters would attack creatures with shells. While clams and some other species grow protective coatings, the type of shell in juvenile oysters is exceptionally vulnerable to low pH.
But it's not clear if corrosive water is the sole culprit or an accomplice.
"We don't yet know, exactly, which characteristic of this water is affecting shellfish," said Oregon State University professor Chris Langdon.
Regardless, the discovery along the coast was just the beginning. During the past two years, Feely and other researchers found this corrosive water also was pushing through the Strait of Juan de Fuca and into Hood Canal and Puget Sound. There, natural processes compounded this corrosiveness beyond anything researchers had found in the open ocean.
So does the fact that Northwest waters already experience these fluctuations mean creatures here are more adaptable or more vulnerable? Are we better off — or worse?
"That's the hit-it-out-of-the-ballpark question we're all trying to answer," said Oregon State University professor George Waldbusser.
Native oysters surviving
For example, while upwelling has been devastating Pacific oysters — an introduced species native to Japan — the native Olympic oyster seems to have done just fine, he said. But it's not clear whether that's because the Olympic oyster has been here longer, because they rear larvae differently, or because of something else entirely.
"The whole story is just much easier to understand in the open ocean as a whole," he said.
Or consider the findings of Australian scientist Phil Munday, who discovered larval clownfish and some damselfish often get lost in corrosive waters and chase after the smell of rock cod — a fish that likes to eat them. Does that research translate to fish in Puget Sound?
"As yet, we do not know whether similar problems might occur in other systems," Munday said.
Scientists also aren't sure how to separate impacts of acidifying waters from other environmental factors.
"Low pH isn't occurring in isolation," said Fabry. "There's also low oxygen and warmer temperatures. It's just not so simple."
The five most-studied seagrass species tend to thrive in corrosive waters, but they may react differently when water temperatures also rise.
And then there are the cascading impacts across species. Fabry studies pteropods, tiny sea snails that make up more than 60 percent of the diet of Alaska's juvenile pink salmon, and a species vulnerable to corrosive waters. What happens to salmon and salmon-dependent fish and seabirds if pteropods get in trouble?
The chests and spines of urchins are made of calcium carbonate, and when biologist Anne Todgham and a colleague raised purple sea urchins in low-pH water, the larvae grew smaller, with less of a skeleton and in different proportions. Urchin larvae float through the water column, so those changes mean they probably move differently, too.
"Normally they look a bit like a rocket ship," she said. "These were stumpier."
It's too soon to say how these notoriously heavy kelp-grazers might fare in a potentially seagrass-rich environment.
Industry tries to cope
In the meantime, hatcheries in Dabob and Oregon's Netarts Bay have installed pH monitors and now seek out noncorrosive water, with great success. But the industry's travails still can be seen in Dabob Bay.
Workers last week trucked tens of thousands of bags of old oyster shells to the bay, where they planned to dump them in shallow water.
Oyster larvae like to swim around and settle on hard surfaces such as old shells, and normally these would get dumped in Willapa Bay for use by young oysters. But larvae oysters still are dying in the wild in Willapa, so Taylor Shellfish workers will try to grow them here.
And they'll be hoping the south winds don't switch direction.
Craig Welch: 206-464-2093 or firstname.lastname@example.org