A new world study of how calcium concentrations are changing in freshwater lakes all over the world has revealed that in broad areas in Europe and eastern North America, calcium levels are declining towards ranges that can be critically low for the reproduction and survival of many aquatic organisms.
The decline of calcium may have significant impacts on freshwater organisms that rely upon calcium deposition, together with integral parts of the food net, such as freshwater mussels and zooplankton.
In Widespread diminishing anthropogenic effects on calcium in freshwaters, printed recently in Scientific Reports, researchers found that the worldwide median calcium concentration was 4.0 mg L-1, with 20.7% of the water samples showing calcium concentrations 1.5 mg L-1.
1.5 mg L-1 is a threshold considered critical for the survival of many organisms that require calcium for their survival. Therefore, some lakes are approaching levels of calcium that endanger organisms that depend on that calcium for construction and growth.
The study also attributes a few of its results to freshwater lakes’ ongoing recovery from the impacts of acid rain.
“Given governmental and industry motion in the last few decades to scale back sulfate deposition related to acid rain, lakes are now subject to much less calcium leaching from surrounding terrestrial areas,” stated Gesa Weyhenmeyer, Professor on the Department of Ecology and Genetics/Limnology, at Uppsala University in Sweden and lead researcher on the study.
The study drew on 440,599 water samples from 43,184 inland water websites from 57 countries and analyzed decadal developments in over 200 water our bodies since the Eighties. It was global research conducted by several researchers throughout Europe and North America. IISD Experimental Lakes Area—the world’s freshwater laboratory— in northwestern Ontario, Canada, contributed expertise and data from its unique long-term monitoring dataset of over 50 years.