One aspect of climate warming that most effects the oceans is the increased levels of acidity in seawater. This change in the chemistry of seawater effects the ability of shellfish like oysters to produce larvae or “oyster seed” that hatcheries sell to aquaculture farms that then raise the oysters to maturity. In the Pacific Northwest, famous for the quality of its shellfish, hatcheries have seen “oyster seed” production plummet, down nearly 80% in recent years. (photo – Taylor shellfish farms)
30% More Acidic
Researchers that have been tracking PH levels in seawater since the 1980’s have discovered that as the oceans absorb more carbon dioxide they become more acidic. They estimate that the ocean is already 30 percent more acidic than it was at the beginning of the Industrial Revolution, a trend projected to continue into the future.
“This would be a 100 to 150% increase of the acidity of the oceans by the end of the century. This is a very dramatic change that has not been seen in the world’s oceans for more than 50 million years,” says Richard Feely, a leading researcher on ocean acidification.
Bill Dewey a shellfish producer adds, “With oysters, the vulnerable stage that dissolves in these corrosive waters is in the first two or three days of their life, they’re using a form of calcium carbonate to build their shell and that dissolves really easily.”
“There’s never been any time in the history of the planet that we know of, that CO2 has increased as quickly as it is right now.” Says Paul McElhany of NOAA.
What’s the Future for Shellfish?
So is there hope for the shellfish industry, that in Washington State alone is worth $270 million in annual sales and employs 3200 people?
An article in Hakai, suggests that particular, coastal environments have more moderate levels of ocean acidity. The determining factor appears to be the amount of seagrass and seaweed growing in those areas. The research was carried out by scientists from the University of California in Irvine.
Cascade Sorte and Nyssa Silbiger, authors of the report, selected 57 tide pools scattered along 1,800 kilometers of Pacific coastline from Southern California, north to Oregon. A sampling area that represented a broad diversity in geography and biology. They recorded the components of each tide pool, counting the species present and measuring the chemical makeup of the water. (photo – Sean Crane, Hakai)
Can Seaweed Reduce Ocean Acidification?
They anticipated that geography would play a part in determining levels of acidity but were surprised to find other, more significant influences especially the amount of vegetation. It seems that the presence of seaweed, seagrass and algae absorbs acid and as the vegetation increased so did the “buffering” effects. The benefit was most apparent where there was lots of vegetation and less water movement, consequently it does not have an effect in open ocean.
Many areas however can benefit and the report’s finding were applauded by aquaculture farmers.
“If seaweed can lower the acidity of ocean water within a certain area, that’s potentially very useful to us,” said Matthew Moretti who grows Maine mussels. “Any help we can get to improve the conditions of our mussels and scallops is very encouraging and welcome.”
By Robert Frerck, Blue Ocean Network