After a new study found that trees in the forests have been consuming more fresh water due to ongoing calcium deficiency, due to soil acidification, another study found that the calcium levels in freshwater lakes keep declining in Europe and eastern North America. The decline is alarming as it may prevent successful reproduction and survival of various aquatic animals.
The calcium is essential for species such as freshwater mussels and zooplankton which power the freshwater lake food web. The decline may ruin that food web because those essential species depend on it.
A group of scientists working on the study published in Scientific Reports aim to explain what anthropogenic effects the calcium decline leaves on different aquatic species. According to the new study, the global median calcium concentration was 4.0 mg L-1, with 20.7% of the water samples showing calcium concentrations that were less than 1.5 mg L-1, which left the team concerned.
The 1.5 mg L-1 concentration is a value scientists consider a lower threshold, which alarms many scientists. The threshold is considered critical for the survival of many organisms that depend on calcium concentration. The newly-measured values show that the calcium levels in freshwater lakes are reaching the values that may result in endangered organisms that depend on calcium.
The study attributes the calcium decline to the freshwater lakes’ ongoing recovery from the consequences of acid rain. A study earlier this year also focused on the consequences of fossil fuel burning, which causes acidification of soil, causing trees to consume more freshwater than usual due to calcium deficiency. This may have dire consequences for fresh and drinkable water sources because we may have less of the water that we can consume.
“Given governmental and industry action in the last few decades to reduce sulphate deposition associated with acid rain, lakes are now subject to less calcium leaching from surrounding terrestrial areas,” said Gesa Weyhenmeyer, professor at the Department of Ecology and Genetics/Limnology, at Uppsala University in Sweden and lead researcher on the study in a statement. “Paradoxically, therefore, successful actions taken to address the harmful impacts of acid rain may have led a decline towards critically low levels of calcium for many aquatic organisms.”
The researchers that worked on the study obtained 440,599 water samples from 43,184 inland water sources from 57 countries and compared decadal trends in over 200 water samples since the 1980s. The study is a joint project of researchers from Europe and North America. Most of the data was shared by the IISD Experimental Lakes Area which is the world’s best-known freshwater laboratory, located in northwestern Ontario, Canada. The organization shared data from a dataset that recorded the calcium levels in freshwater lakes for over 50 years.