One fifth of the world’s liquid surface fresh water is contained in the Great Lakes. In some ways, these inland ‘seas’ behave like the real oceans—soaking up surplus anthropogenic CO2 from the atmosphere, for one thing. But the distinctive effects of the acidifying compound in fresh water and on its aquatic ecosystems are much less understood. And as Brian Bienkowski observes in The Daily Climate, science lags.

‘Acid’ lakes in eastern North America used to mean fallout from upwind coal-burning power plant. That problem has been largely solved by a successful cap-and-trade program for emissions of sulphur and nitrous oxides, on which contemporary carbon trading programs are based. But as carbon emission continue to rise, the region’s lakes are taking in more CO2, with the same effect.

The Great Lakes are already less alkaline than the ocean—Lake Superior’s alkalinity is barely a third of surface sea water. Perhaps in consequence, they also have fewer shell-bearing aquatic life—clams and crayfish but also invasive zebra mussels. All may suffer as lake water becomes even more corrosive to their calcium based shells.

A critical unknown is how rising acidity and the presence of additional CO2 will affect phyto- and zooplankton in the Lakes sunlit surface zones, the microscopic plants and animals that form the foundation of the aquatic food chain.

“States like Washington have a whole panel, with detailed plans on how to deal with acidification,” said Galen McKinley, of the University of Wisconsin-Madison’s Department of Atmospheric and Oceanic Sciences. “We should really be making it more of a priority here.”