The beloved salmon — along with other commercially valuable fish such as herring and pollock— thrives on a diet of microscopic marine sea snails known as pteropods.
Last week, the National Oceanic and Atmospheric Administration announced that scientists have determined that human-caused carbon dioxide in the Pacific Ocean is dissolving the shells of these creatures, which could lead to further trouble down the road.
“They’re sort of the canary in the coal mine for ocean acidification,” said Richard Feely, a senior scientist for NOAA who led the research on the pteropods. “We’re worried what will happen with the fish next.”
A series of research cruises conducted between 2007 and 2013 at sites along the West Coast led researchers to record additional carbon dioxide brought in since the beginning of the Industrial Era.
Levels of man-made carbons typically came in between 55 to 65 micromoles per kilogram of seawater, Feely said. Half Moon Bay’s data came right around the middle, at 60 micromoles per kilogram of seawater.
A shell is formed when there is enough carbonate ions to build it, experts said. When there is a higher concentration of carbon dioxide in the water it lowers the carbonate ion concentration and reacts with the water to form a bicarbonate.
An estimated 10 to 35 percent of the pteropods taken from the waters during the studies showed dissolution of their shells. When a pteropod’s shell is dissolved it can affect its ability to swim and escape from predators. Feely also noted, however, that the predators that dine on these sea snails may be intentionally choosing not to eat the ones with the dissolved shells.
And while this research was focused on the pteropod, ocean acidification affects all animals with a shell made from calcium carbonate.
The carbon dioxide levels may even be affecting Dungeness crabs that grow to develop chitin to protect their calcium carbonate shells, but remain vulnerable when they’re young.
In 2007, Feely said oyster larvae were dying in hatcheries, and scientists were able to prove that human-produced carbon dioxide sources were causing a problem. It was fixed by adding calcium carbonate to the water. That kind of fix can be made in the close confines of a hatchery, but the ocean is another matter.
One factor that might help would be the building up of kelp beds, which is currently being studied in Puget Sound, Keely said.
The research is ongoing, Keely notes, but scientists are continuing to keep a close eye on the man-made carbon dioxide levels and their effects on the sea life.
“After we do those experiments over the next couple years, we will be able to answer those questions,” Keely said.
Carina Woudenberg, Half Moon Bay Review, 30 November 2016. Article.
