While it has been observed that increasing atmospheric levels of CO2 are causing the world’s oceans to grow more acidic over time, new research offers first evidence that elevated atmospheric CO2 levels are causing increased acidity of freshwaters. The research also suggests that freshwaters may acidify faster than ocean water.

The study, conducted by researchers in Germany and published in Current Biology, found that some freshwater ecosystems have become more acidic with rising pCO2 (partial pressure of CO2). They demonstrated in lab studies that increases in freshwater pCO2 can have detrimental effects on at least one keystone species, a tiny freshwater crustacean, leaving them less able to sense and defend themselves against predators.

“Ocean acidification is often called climate change’s equally evil twin, and many current investigations describe tremendous effects of rising CO2 levels on marine ecosystems,” said Linda Weiss at Ruhr-University Bochum in Germany. “However, freshwater ecosystems have been largely overlooked. Our data indicate another pCO2 problem: pCO2-dependent freshwater acidification.”

Studies on ocean acidification have shown that there are consequences for marine food webs, nutrient cycles, overall productivity, and biodiversity. Yet, the researchers say, surprisingly little has been known about the impact of rising atmospheric CO2on freshwater systems. While scientists expected that there had been increased pCO2 in freshwater bodies, the data were lacking.

To investigate, Weiss and colleagues looked to four freshwater reservoirs in Germany. Their analysis of data over 35 years, from 1981 to 2015, confirmed a continuous pCO2 increase. In their work, they reported a change in pH of about 0.3 within 35 years, suggesting that freshwaters may acidify at a faster rate than the oceans.

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Weiss says they were fortunate to obtain such a long data series on four freshwater reservoirs. It will now be important to gather more data representing freshwater impoundments around the world.

“We now want to know the global degree of this phenomenon,” Weiss said. It remains to be seen if the effects will be similar across all freshwater bodies.

Story adapated from: Science Daily.

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