Ocean Blues Print
Written by Sandra Hines   
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Just how much harm might result is the big question. Scientists are still trying to sort out the possible detrimental effects on individual species of calcifying organisms.

Take, for instance, the single-cell plant-like organisms called coccolithophores. Along with others, they are a foundation of the ocean’s food web, especially in nutrient-poor waters where coccolithophores can thrive but phytoplankton do not.

Coccolithophores use carbonate and calcium to cover themselves with plates, sometimes more than 100 of them. The plates may offer the cells some sort of protection, according to Peter von Dassow, ’97, who did post-doctoral research in the lab of Oceanography Professor Virginia Armbrust and is now at France’s Station Biologique de Roscoff. Or they may concentrate carbon dioxide for photosynthesis. Or perhaps the plates act like light filters or collectors to modulate the light that gets into the cell.

“We don’t know exactly why having calcite plates is good for coccolithophore cells. They must provide some sort of advantage because these tiny plant-like cells have evolved a very complex machinery to produce such ornamentation—which they seem to regulate very carefully—and they are a very successful group of phytoplankton,” von Dassow says.

Affiliate UW Professors Chris Sabine (left) and Richard Feely inspect a marine buoy at the Pacific Marine Environmental Laboratory. The two NOAA researchers were among the first scientists to warn about rising carbon dioxide levels in the oceans. Photo by Mary Levin.
“We think that calcification by coccolithophores has played a key role in ocean biogeochemistry and, hence, carbon cycling, since they first appeared about 220 million years ago,” von Dassow adds. “So a change in calcification by coccolithophores, and a change in their ecology, might have a big impact on the ocean.”

Suppose higher levels of dissolved carbon dioxide cause protective coatings to degrade but the animals don’t die. Will they be eaten by new predators if their armor isn’t as strong? Can they still reproduce in the same abundance? Can they still compete as well with other organisms for food? If they disappear, what else might take their place in the food web?

With these questions looming, it is time to study ocean acidification across whole ecosystems and in the open ocean. Scientists think UW’s Friday Harbor Laboratories would be an ideal setting. They want to capture mini-ecosystems in specialized plastic bags that are about 7 feet by 17 feet in size, what are called “mesocosms.” Researchers scoop water into the bag along with all the diversity of plants and animals in that particular water sample so that the community can be subjected to various experiments.

The waters of the San Juan Islands are filled with the kind of pteropods that were the subject of those shipboard experiments in the 1980s, when their shells dissolved in waters containing concentrated carbon dioxide.

“The North Pacific is an area we think is particularly vulnerable,” says Chris Sabine, NOAA oceanographer and UW affiliate assistant professor. Not only is human-made carbon dioxide gas dissolving into the oceans at the surface in the North Pacific, but this area also receives carbon dioxide that has accumulated naturally in deep waters over in the Atlantic around Greenland and Iceland. Those deep waters travel slowly around the globe, ending up on our doorstep just as the forces driving global ocean circulation push the carbon-dioxide-rich waters back toward the surface.

“As man-made CO2 comes in from the top it meets the high natural CO2 that’s coming up from the bottom,” Sabine says. “Projections in model studies have suggested that by the end of this century these two can interact in a way that the North Pacific will actually become corrosive to the shells of these organisms, something that hasn’t happened in millions of years.” • Sandra Hines is a science writer and assistant director of the UW Office of News and Information.