Ocean Acidity Moving to
Center Stage Science

by Mike Crowe

The effects of ocean acidification is something that will play out over the next 50 to 100 years, said Piero Calosi, a research scientist at the University of Quebec in Rimouski. Higher levels of ocean acidity will challenge lobster and other sea animals in many ways. At this time, early in the study of these effects, there are no known changes in lobster population stocks, said Calosi. However, predictions of an increase of 0.3 to 0.5 percent in ocean acidity are solid, he said.

For lobster, which has a complex life cycle with several developmental stages, all of which could be affected by higher acidity and thereby influence the transition to the next stage, there are many questions and concerns.

The Gulf of Maine’s cold water is more acidic than warmer surface water. Darling Marine Center marine biologist Bob Steneck made a comparison to a warm can of carbonated soda. When it is opened it foams out of the can. That is the carbon dioxide being released into the atmosphere. That same liquid at 40 degrees would not foam up upon opening.

Steneck said ice core samples indicate the earth’s temperature has been warm in the past, but never has there been CO2 levels as high as they are now. The result is that 90% of sea animals have to work harder to create shells. Lobsters harden their shell with limestone. Limestone is dissolved by CO2. Higher acidity increases energy demands on sea animals attempting to extract limestone to create shell material.

An environmental disaster like an oil spill strikes like a blunt instrument, said Steneck. But with ocean acidity there is no smoking gun. It is not visible and changes from year to year might not be noticed. But the problems are there. The pressure on the lobster’s metabolic process is far less apparent than a claw lost in a struggle with another lobster. But in the long run, it could be more fatal. And, Steneck said, larval lobsters may be the most at risk of being affected by ocean acidity. In general, he said, scientists agree that acidity in the ocean has reached unprecedented levels.

Still, he said, “As far as we know, there is no hard evidence of ocean acidity affecting lobster on the coast of Maine.”

Recent research on acidity remediation in Maine’s inshore waters was done by marine biologist Susie Arnold. Arnold has been studying the ability of seaweed to absorb carbon. She observed differences in the capacities of eelgrass and seaweeds like rockweed and kelp. Eelgrass absorbs more carbon and acts as a carbon sink by drawing the carbon out of the water and bringing it down through its root system, depositing it in the mud around its roots. Seaweed is not a rooted plant, although it is attached to the bottom by a holdfast. Still, seaweed draws nutrients and carbon out of the water column. It stores the carbon in its fiber. Although seaweed absorbs less carbon than eelgrass, there is much more seaweed than eelgrass.

Very early results of Arnold’s work has shown reduced acidity levels around mussel aquaculture facilities where seaweed was also grown experimentally. Arnold installed scientific instruments in a Casco Bay kelp farm and upstream of the farm to compare results. In only four weeks with seedling kelp at 14” height there was a slight decrease ion acidity in the water samples tested. Estuaries are more vulnerable said Arnold because the fresh water that runs into them is more acidic. That water can also contain excess nutrients that cause algae blooms that decay and increase acidity.

Much more funding of research on ocean acidity has been flowing from federal sources in recent years. An article for a general audience appeared in the New Yorker in 2008. Sixth Extinction author Elizabeth Kolbert’s “The Darkening Sea: What Carbon Emissions Are Doing To The Ocean” is a comprehensive look at the problem. Another article in the journal Science, Bob Steneck was one of the co-authors, is more technical. Both articles can be accessed at the following links.

Go to fishermensvoice.com to see general interest article on ocean changes by Sixth Extinction author Elizabeth Kolbert in the New Yorker, The Darkening Sea.