Our lakes get calcium (Ca) naturally from the air and from surrounding lands, and on occasion, from us. Ca enters lakes directly from the atmosphere, in the form of windblown dust and precipitation, but as measured by MECP  scientists, these inputs have actually fallen by about 50% in Muskoka over the last few decades as we have reduced air pollution levels.
Secondly, Ca enters our lakes in overland flow in streams in the watershed. The rate of this calcium supply is controlled by both rates of stream flow and the Ca concentrations in stream waters, the product of which is the total Ca supply. This overland supply has fallen because both stream flow and Ca concentrations have fallen, the former likely linked to climate change, and the latter, a legacy of acid rain. This leaves us. We add Ca to our watersheds and the lakes they support in many ways, mainly inadvertently. We bring soil and fertilizer to our gardens and lawns. We clear the land, potentially mobilizing stored Ca. We add calcium chloride as a dust suppressant to our gravel roads. One such dust-controlling trip a year for several years reversed the Ca decline trend in Dickie Lake, east of Baysville.
Finally, we can add ashes from our fireplaces to our forests. If the wood came from our property we are recycling Ca from our land. If we brought the fire wood in from elsewhere, then spreading the ashes on our property can start the process of reversing decades of Ca loss. This is one of the goals of our ASHMuskoka project.
 Ontario Ministry of the Environment, Conservation and Parks