Researchers link crayfish decline in Algonquin Park lakes to lack of calcium

And currently CO2 is causing an increase in acidity in bodies of water.

http://www.eurekalert.org/pub_releases/2015-10/qu-qrl102815.php

Public Release: 28-Oct-2015
Queen's researchers link crayfish decline in Algonquin Park lakes to lack of calcium
Queen's University

Researchers from Queen's University, working with colleagues from the Ontario Ministry of the Environment and Climate Change, have linked the localized near-extinction of a native crayfish species in four lakes in Algonquin Park to declining calcium levels, a long-term legacy of acid rain on forest soils and aquatic ecosystems.

"Crayfish are an integral component of aquatic food webs, because they function at multiple trophic (relating to feeding and nutrition) levels and are a key element in the diets of popular recreational and economically important fish species," says Kris Hadley, the lead author of the study and a PhD student at Queen's University at the time the study was conducted.

Crayfish shed their protective carapace - the upper exoskeleton that is primarily composed of calcium carbonate - several times during their life cycle and, as a result, have high calcium requirements. The researchers found that lack of calcium in the lakes has contributed to a decline in crayfish populations.

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The research team found evidence that acid rain had impacted some of the lakes over time, but they also inferred marked declines in lake water calcium levels - a known legacy of acid rain. Dr. Hadley says the team's findings suggest calcium concentrations began declining in these lakes as early as the 1960s, and may now have fallen below the threshold required for the survival of some aquatic organisms.

"Although lake water pH has been recovering in many waterways with controls on acid emissions, there has been no such recovery in calcium levels, and thus aquatic organisms are beginning to show the negative effects of what we are colloquially calling 'aquatic osteoporosis,'" says John Smol (Biology), the Canada Research Chair in Environmental Change.

"Aquatic osteoporosis" has only recently been identified as an environmental stressor for many soft-water lakes in North America and elsewhere, with potentially serious ecological consequences, such as the "jellification" of lakes. This is the third major study published by Dr. Smol and his team on the effects of declining calcium levels on the ecosystems of soft-water lakes.