Inside a cramped Seattle laboratory, the researchers look like fishermen who got sent to a construction job. Wearing orange waders and yellow boots, they thread their way between shelves of tubs filled with what look like giant mason jars.
Overhead, a rainbow of colored tubes bubble gases into tanks, changing the water chemistry to reflect different points in time—past, present and future—as increasing amounts of fossil fuel pollution make the oceans more acidic.
If it’s possible to predict how this process of ocean acidification will affect the Northwest’s marine life, this is where it will happen. Over the next months, the scientists will run experiments on some of the region’s most valuable marine species: geoducks, Pacific and Olympia oysters, pinto abalone, rockfish, crab and tiny shrimp like krill and copepods that are linchpins of the food chain.
They’ll immerse those creatures in baths of acidified seawater and assess their most basic biological functions: how big do they get, can they grow shells, are they developing normally, are they more stressed, do they succumb to disease. And most importantly, do they survive?
And then they’ll tackle the harder task – trying to predict how those changes ripple through an entire marine ecosystem. It’s safe to say that there will be tradeoffs, said Paul McElhany, lead ocean acidification researcher for NOAA’s Northwest Fisheries Science Center. And some mollusks, such as oysters, look like the early losers.
If this is the food web of Puget Sound, once you start looking at shrimp, geoducks, copepods, the indirect effects are really difficult to predict. You’re changing the predators and prey at the same time. You’re altering the abundance of competition. You’ve got physical and structural changes—eelgrass does better and corals do poorly. I feel confident saying it’s going to cause change. Predicting exactly what those changes are going to be—we can identify the most vulnerable species but the indirect effects are much harder.
Understanding how sea life will react to ocean acidification, and to devise systems to help seafood and fishing industries cope with those changes, gained new urgency with the recent discovery of surprisingly acidic waters along the Pacific Coast and in Puget Sound.
As oceans absorb increasing amounts of carbon dioxide from cars, factories and tree cutting, the pH of seawater decreases, making the water more acidic. That process also binds up calcium carbonate ions, which are so widely used to build shells and skeletons that some call them the “soil of the marine world.” And changes in pH may change the nutrients available to phytoplankton, altering the nutritional quality of that basic marine food and favoring some types of algae.
So how will different creatures fare in increasingly acidic seas?
- Clownfish larvae lost their sense of smell, their ability to find suitable reef habitat and to distinguish their parents from other fish. They also started following potentially dangerous scents they would otherwise avoid.
- Abalone and sea urchins from Australia’s Sydney Harbor either died or grew abnormally.
- Antarctic krill embryos, a cornerstone species in the marine food chain, failed to hatch.
- Brittle stars were able to increase their metabolism and rate at which they built skeletal structures, but that coping strategy was undone by muscle wastage in their arms.
- Jumbo squid became lethargic and sluggish as their ability to deliver oxygen to blood cells was affected.
- Pteropods—marine snails also known as “sea butterflies” that make up as much as 60 percent of the diet of some juvenile Alaskan salmon—dissolved as their tiny winged feet kept swimming.
But it’s not clear whether previous lab results will hold true for Pacific Northwest creatures. Some have already been exposed to pockets of unusually corrosive water, such as that found in Hood Canal. No one knows whether that means they’re better adapted or already so stressed that they’re likely to fare worse.
And even closely related species can respond differently to ocean acidification. In one experiment, the larvae of edible sea urchins died in greater numbers while green sea urchins thrived.
In another experiment that exposed 18 species of marine calcifiers to water rich in carbon dioxide, 10 had trouble building shells as efficiently. Some of those protective structures and skeletons started dissolving. Yet seven species—including a crab, shrimp, lobster, calcifying algae, temperate urchin, and a limpet—produced shells more rapidly. Perversely, it was these 7 cases that grabbed the headlines, which missed the larger point. As the study’s author later asked: “If someone removed 10 of every 18 bricks from your house, is that still a house in which you would want to live?”
In Seattle, McElhany used to spend his research time on salmon populations and recovery plans. He shifted to ocean acidification after realizing that all the habitat restoration projects in the world may become band-aid solutions if the fundamental chemistry of the ocean changes.
“It seemed like a big enough problem that could shuffle the entire ecosystem,” he said.
Among the marine creatures that the Seattle researchers plan to study at the NOAA lab are krill and copepods, two forms of crustaceous plankton that many kinds of commercially important fish—herring, juvenile salmon, pollock—eat at some stage of their lives. Inside the mason jars on a recent morning were the larvae of geoduck, which looked like floating specks of sand.
The scientists will rear the animals in three different batches of seawater that have absorbed different amounts of atmospheric carbon dioxide. Then they’ll compare the animals’ survival rates, growth and development as the water becomes increasingly acidic in the following tiers:
- Past (280 ppm of CO2): Preindustrial levels before fossil fuels were widely used.
- Present (390 ppm of CO2): Current conditions
- Future (1000 ppm of CO2): Emissions that could theoretically be possible by the end of the century if steps aren’t taken to reduce them.
Researchers intentionally picked a figure at the high end of possible scenarios for 2100, since emissions are still rising and Puget Sound already has high carbon dioxide levels. Plus, if exposure to a high carbon dioxide scenario harms a particular marine species, the scientists can then test lower levels to see where the threshold for damage lies.
Unlike other studies that have investigated how a single species reacts to a single change in ocean chemistry, the scientists here can adjust other variables like temperature, oxygen and food. In the actual ocean, all those things matter, McElhany said.
If you’re well fed, you might be able to suffer through the effects of ocean acidification. If you’re temperature stressed, maybe you can’t deal with the pH change as well. It’s the complex interplay between a lot of different factors.
The lab is growing so quickly, it’s encroaching on the parking lot one tent-like structure at a time. They’re borrowing geoduck larvae from local hatcheries, collecting oyster sperm and eggs from the wild, relying on other scientists to rear baby rockfish and waiting for pregnant krill and copepods to release eggs.
As they begin to collect baseline information about how different species fare in increasingly corrosive waters, they’ll also have the ability to mimic real-world fluctuations. For instance, the pH in any given part of the ocean can vary dramatically as plants suck up carbon dioxide to photosynthesize during the day and then release it at night as bacteria start to do their work.
“It’s the pattern, not the averages that are important,” McElhany said. “It’s how low does it go.”
They’re also collaborating with other university and government scientists interested to know how the animals respond to stress and disease under different climate scenarios or how acidification affects animals on a molecular level. In the San Juan Islands, University of Washington researchers are planning to wall off a chunk of ocean with plastic and run tests on an entire ecosystem pocket.
In our next post, we’ll talk to people who have become key players in ocean acidification research by necessity, not by choice: the Northwest shellfish growers who watched their baby oysters die by the millions.
Photos courtesy of the following flickr users under a Creative Commons license: Rockfish photo by NOAA photo library, geoduck photo by Dan Hershman, sea urchin photo by cwilso, copepod photo by Michael Bok.