Moving Window Averages and Ocean Acidification

There’s an interesting study on carbon dioxide effects on ecosystems. I’m trying to lay my hands on the full paper, which is behind a paywall. My comments here are based on the press information about the Scotland study.This is a bit different than most reports on ocean acidification. The point of the research was to determine effects, if any, of temporary increases in carbon dioxide saturation in seawater like those that are known to occur in various industrial processes and with certain pollution sources.

They did find an effect. Organisms with calcium carbonate scaffolding were losing bodily integrity when exposed to high carbon dioxide concentrations. Well, I should note that the chemistry isn’t just that there is a bunch of carbon dioxide in the seawater. Carbon dioxide interacts with seawater such that you get carbonic acid, and it is the carbonic acid that is troublesome.

“We found that there was a rapid, community-level shift to net dissolution, meaning that within that community, the skeletons of calcifying organisms like star fish and coralline algae were dissolving.

“If you think of pulses of carbon dioxide being carried on the tide to a particular site, it’s like a flash flood of CO2.

“Our continued monitoring of the site directly after the CO2 exposure found recovery was comparably slow, which raises concern about the ability of these systems to ‘bounce back’ after repeated acute CO2 events.”

In other words, it takes longer to heal from trauma than the timescale of the traumatic event, something anyone experiencing a broken bone should be able to relate to.

I wanted to relate this to the general threat of ocean acidification. Mostly I had been paying attention to maps showing declines in aragonite concentration, which is is the bio-available form of calcium carbonate that organisms like corals, starfish, and oysters rely upon to extract and build shelly parts from. At ocean scales, that appears as mostly smooth transitions from region to region, but some regions have already seen decreases in aragonite concentration to less than half of historic values. This is a stressor for various vulnerable species. And one can see this as a result of the ongoing global uptake of increasing atmospheric carbon dioxide by the world’s oceans, a steady and relentless general assault on environmental conditions taking place at long timescales. But long timescales are not the only timescales.

The global ocean acidification issue as I was looking at it is like a moving window average. Values that the system had long ago are discounted, and variations in values within the window are smoothed out so one sees that long-term signal, in this case a monotonic increase in global ocean acidification.

But those variations in value, both spatial and temporal, exist and have consequences. The moving window average is not complete information on what is happening. Take, for instance, this page on ocean acidification and seasonal differences in acidification.

Ocean acidification is already having an impact, especially in places where the seasonal upwelling of deep water has made seawater naturally more acidic. In a recent study by researchers at NOAA, more than half of the pteropods sampled off the coast of Washington, Oregon and California showed badly dissolved shells. Ocean acidification has been linked to fish losing their ability to sniff out predators, and the die-off of baby oysters in hatcheries off Washington and Oregon, where more acidic deep water comes to the surface each spring and summer.

By 2100, ocean acidification could cost the global economy $3 trillion a year in lost revenue from fishing, tourism and intangible ecosystem services, according to a recent United Nations report. The U.S. Government Accountability Office, the watchdog arm of Congress, has reached similar findings and recommended that President Obama create a research and monitoring program dedicated to ocean acidification.

So the Scotland study linked at the top is no surprise. We already knew that increased carbon dioxide concentration at slighter longer (seasonal) timescales does have an effect on vulnerable organisms. The Scotland study simply shows that even brief exposures to high concentrations of acid can have lasting effects. We don’t really have a problem understanding that a faceful of sulphuric acid leads to injury and usually permanent scarring and disfigurement for humans. The Scotland study shows that while the acid in question isn’t as concentrated, it will certainly mess up or kill vulnerable marine organisms. While the vast majority of humans would never consider throwing acid at another human or even a domestic animal, we as a species do not seem to have any qualms about applying an insidious acid attack on our oceans and every living thing in them.

Publisher info on the Scotland study:

Marine Ecology Progress Series

Volume 587, pages 73-80, doi:10.3354/meps12421

Burdett HL, Perna G, McKay L, Broomhead G, Kamenos NA
Community-level sensitivity of a calcifying ecosystem to acute in situ CO2 enrichment