From PBS News Hour (Teresa Carey):
What the scientists did: With the ongoing combustion of fossil fuels adding carbon into the atmosphere, aquatic biologist Linda Weiss wanted to learn if freshwater ecosystems fall victim to the same acidification as the oceans. Ocean acidification happens when excess carbon dioxide mixes with seawater, increasing the water’s acidity through a chemical reaction.
So Weiss looked to an organization in Germany that monitors drinking water quality of four reservoirs.
Using their data, which spanned from 1981-2015, Weiss calculated pCO2, a measure that reflects the carbon dioxide exchange between the lake and its environment, and from that, she derived acidity. Reminder: Acidity is measured in pH levels, with lower numbers signifying an increase in acid.
What they found: Over a 35-year span, their data showed a continuous increase in pCO2 in the lakes that was associated with rising acidification — pH levels decreased by 0.3. This rate is three times what has been measured in oceans since the industrial revolution. Weiss’ team found lakes are absorbing some CO2 out of the atmosphere, like oceans, but even more of this carbon pollution comes from emissions settling in soil and washing into freshwater.
Why it matters: Weiss wasn’t surprised. Scientists have speculated if the oceans are becoming more acidic as they absorb excess carbon dioxide, then freshwater may do the same. But Weiss’ findings exceeded previous predictions for freshwater acidification. For example, the dramatic increase in acidity she found over 35 years is equal to the levels expected in the Great Lakes in 2100 — 82 years from now.
Will wildlife suffer? Daphnia, water fleas, are tiny abundant crustaceans in freshwater rivers and lakes. Because many larger animals, like tadpoles, newts and fish, regularly snack on the water flea, they are an important link in the food chain.
“If they are harmed by any stressor, then this may have cascading effects for the rest of the community,” Weiss said.