Scientists have been studying the effects of carbon dioxide on climate for decades.
More recently, however, it was discovered that the oceans have absorbed about a third of the CO2 emitted into the atmosphere. Carbon dioxide alters ocean chemistry, making seawater more acidic. The scientific term for this phenomenon is “ocean acidification.”
Acidification threatens not only the ecological health of the oceans, but also the economic well-being of the communities and industries that depend on a productive marine environment.
It’s a powerful motivation for scientists, including Shallin Busch.
Dungeness crabs are her lab rats.
Shallin Busch is a Mukilteo-based ecologist whose research is linking ocean acidification to the deteriorating health of the Puget Sound ecosystem.
Busch, 40, has been a fisheries biologist and researcher for the National Oceanic & Atmospheric Administration’s Northwest Fisheries Science Center at Mukilteo for nearly 10 years. She is at the forefront of NOAA’s efforts to understand the effects of ocean acidification.
“I have just been driven by this question. How does our physiology change with our environment? I stumbled on that in college and I’ve been following it ever since,” she said. “Climate change and ocean acidification is really a huge threat to the Earth as we know it.”
After earning a doctorate in zoology at the University of Washington, Busch was hired to do fisheries research for NOAA.
Though she was stationed in Maryland for a year, the Mukilteo field station is her research home. Since 2014 she has worked for the Ocean Acidification Program, dedicating herself to understanding and predicting the threat acidification has on the West Coast’s food web and fishery management. She co-leads experiments at the research lab, which are carried out by a team of scientists.
“Ocean acidification is not part of climate change,” Busch said, but both problems are caused by carbon dioxide. “As we burn fossil fuels, more carbon dioxide is released into the atmosphere and dissolves into the ocean. It’s a chemical change that results in a drop in pH and an increase in acidity.”
The Mukilteo team has looked at or is looking at ocean acidification effects on krill, salmon, Dungeness crab, black cod and pteropod (marine snails). So far it has found that lower pH levels lead to lower survival and slower development rates, as well as changes in behavior. Now it’s back to studying Dungeness crab.
“I’m not aware of anyone else looking at potential effects to Dungeness crab,” said Paul McElhany, chief of the Mukilteo station. “It’s interesting, because it’s such a valuable species. It is one of Puget Sound’s top three fisheries. It’s economically very important, and it’s also ecologically very important.”
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Two experiments on ocean acidification and Dungeness crab are running at the station.
One experiment looks at the crab’s response to different pH levels throughout the life cycle. Dungeness crab have five life stages: egg, zoea, megalopae, juvenile and adult. Scientists are studying how acidity effects them between each stage.
A system nicknamed the Ocean Time Machine controls CO2, oxygen and temperature to mimic oceans of the past, present and future. The lab has 13 Mobile Ocean Acidification Treatment Systems, each with their own seawater treatment conditions. Each system maintains up to 28 jars. Each jar keeps a crab larva. Computers track pH, oxygen and temperature conditions because all three are linked to the effects of carbon dioxide.
“Oceans aren’t turning acidic. They are acidifying or they are becoming more acidic, but they will never be acidic,” Busch said. “The pH levels are decreasing, and we expect that maybe they’ll get to 7.8 or 7.6, but they’re never going to cross that threshold into the acidic realm.
“An analogy is the North Pole. It is fundamentally a cold place, but we still say it’s warming. But we don’t call it warm.”
A pH less than 7 is acidic and a pH greater than 7 is basic. Right now the mean pH of the ocean is 8.1 on a scale of 0 to 14.
A 0.3 drop in pH may not seem like a lot, but it’s actually huge. That’s because the pH scale is logarithmic: A difference of one pH unit is equivalent to a tenfold difference in hydrogen concentration. A three-tenths decrease in pH is about a 150 percent increase in acidity.
On a recent day, researchers were examining crab metabolism as they morphed from megalopae into juveniles.
“We’re looking at a broader range of response metrics this time, including respiration and molecular changes,” Busch said. “It’s a window into what’s going on with the physiology, meaning how hard is it for you to maintain your body’s functions like breathing and digesting under changing environments?”
It’s a tricky thing to do because it’s essentially an experiment on a gas.
“You need to build the system, have the system working properly, measure the system to make sure it’s working properly, get the animals, keep the animals alive and take the data on them,” she said. “It’s very much a team approach.”
In addition to raising crabs in the MOATS, the scientists also raise them in well plates stored in an incubator. That’s preparation for experiment No. 2.
The second experiment — still very new to the lab — takes a multi-generational look at acidification impacts. Researchers will expose a family of crabs to different pH levels throughout their life cycles. It will take three years to examine one generation.
“We’ll be working on those for a while,” said McElhany, 54, also a research ecologist. “It’s risky to do these long generational studies, but the species is so important that it seemed like a good idea.”
The team recently mated about 50 males and females. It will be a year before the eggs hatch. It will take another two years before the first generation of lab-raised crabs are able to reproduce themselves.
As they grow, the crabs will be incubated in refrigerators that are modified so that a computer can control the atmosphere inside. Stacks of well plates holding crab larvae will fill each fridge.
“Since this is a brand new project, we’re just trying to keep them alive,” Busch said. They’ll invest in the equipment needed to do the experiment when they work out their methods. “Imagine keeping thousands and thousands of pets under controlled environments with gases, temperature and water.”
Busch and McElhany also make computer models of ecosystems based on ocean acidification data from around the world.
Most recently, they built a model of the California Current based on the findings of 400 papers detailing carbon dioxide’s effects on more than 250 species.
“She’s good to work with,” McElhany said of Busch, with whom he’s worked for about 10 years. “She’s a thoughtful, creative and careful scientist. She’s good at seeing where the holes are in our understanding of these important environmental processes and how we might try to address them.”
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Interns are helping Mukilteo’s team of scientists study Dungeness crab.
One intern, Cindy Kekeh, 20, is majoring in biology at Norfolk State University in Virginia.
A fellow through NOAA’s Educational Partnership Program, she interned over the summer to train as a researcher while working for a government lab. She cared for the crabs, checked water samples and analyzed data.
“I’ve definitely learned more about what research actually is and what it takes to answer a question of interest,” Kekeh said. “Sometimes a research topic seems so simple; however, developing a method to research that topic is not so simple. That’s why teamwork is so important to share ideas and brainstorm together.”
Busch and McElhany have seen acidification effects in Dungeness crab in past experiments. While those kept pH levels constant, these current experiments expose crabs to varying CO2 conditions — just like you would find in the oceans.
With more refined data, they hope to improve their understanding.
“Ecosystems are really complex collections of thousands of species, and the species we interact with regularly, like Dungeness crab, can give us windows into change,” Busch said. “I hope understanding of the implications of carbon dioxide comes from this research. Through understanding, hopefully it will lead to protection.”
Busch has been interested in science and environmental issues since childhood. She grew up in Greenwich, Connecticut, near Long Island Sound, surrounded by 250 acres of forest and just a mile away from the Connecticut Audubon Birdcraft Museum and Sanctuary.
In 1998, she earned a bachelor’s degree in ecology and evolutionary biology from Princeton University. It was at Princeton that Busch settled on her line of scientific questioning: How do human changes to the environment effect the physiology of other species?
Then at UW in 2006 she earned her doctorate in zoology — the study of animals — so she would never be limited in her research.
While working on her undergraduate and doctoral theses, Busch studied the white crowned sparrow in Washington and California, the song wren in Panama and the rufous-collared sparrow in Costa Rica and Ecuador, and their response to environmental stressors, including climate change.
“I was always interested in this interplay between people and nature,” she said. “My line of work lets me study that in a variety of different ways. I made a deliberate decision to work on species that have clear conservation questions.”
In addition to her work as a research ecologist, Busch staffs an interagency working group on ocean acidification.
The group of 13 federal partners — including the Environmental Protection Agency, National Aeronautics and Space Administration, National Science Foundation, U.S. Fish and Wildlife Service, Bureau of Ocean Energy Management and the Smithsonian Institution — coordinate the national response to change in the ocean’s chemistry caused by carbon dioxide. NOAA chairs the group.
Don’t ask her if she has a favorite species to research. She says that’s like asking a mother which of her children is her favorite.
“The Dungeness crab is somewhat reminiscent of the wrens,” Busch said. “They’re fiesty, epecially when they’re really small. They’ve got a lot of spunk.”
Sara Bruestle: 425-339-3046; email@example.com. Twitter: @sarabruestle.