Any discussion of recreational water quality in Muskoka must eventually lead to two topics that are never far from the minds of elected representatives, seasonal and permanent residents, tourism operators, business people and environmental groups — the impacts of acid rain and algae.

“Acid rain” is a broad term referring to a mixture of wet and dry deposition (deposited material) from the atmosphere, containing higher than normal amounts of nitric and sulphuric acids. It results from both natural sources, such as volcanoes and decaying vegetation, and man-made sources, such as vehicle and industrial emissions. Roughly two-thirds of all such emissions come from electric power generation that relies on burning fossil fuels, like coal.  

Acid rain occurs when these gases react in the atmosphere with water, oxygen and other chemicals to form various acidic compounds. When sulphur dioxide and nitrogen oxides are released from power plants and other sources, prevailing winds blow these compounds across state, provincial and national borders, sometimes over hundreds of miles.

Some significant strides were made in addressing the problem in the 1980s and 1990s, as governments around the world worked together to effectively reduce emissions from the worst of the polluting sources. The result was significant reductions of acid rain levels in eastern Canada, including in the Muskoka/Haliburton/Parry Sound region.

At the time, it was assumed that the problem would be resolved by the reduction strategies implemented. Recent studies indicate that an area of eastern Canada stretching from central Ontario through southern Quebec, which includes some 95,000 freshwater lakes, is expected to continue to receive in excess of 15 to 20 kilograms per hectare of acid deposits annually. That is roughly double the level that is considered essential to maintaining a pH of 6.0 (8.0 kg/ha/year) for the more sensitive lakes in our watersheds.

The resulting decline in fish species is predicted to be a net loss of nearly 162,000 fish populations alone. Clearly, acid rain will continue to impact on recreational water quality in Muskoka in the future.

The issue of algae in freshwater lakes is less clear (no pun intended). While the relationship between phosphorus concentrations and algae has been assumed for some time and confirmed in a recent study by Canadian Dr. David Schindler and his associates, there has been an increasing number of episodes of algae in low-alkaline, nutrient-poor lakes on the Canadian Shield.

A recent detailed study of lakes in the Muskoka/Haliburton area show a marked increase in the type of algae known as chrysophytes in more than 90 per cent of the lakes examined. They are a type of algae that result in taste and odour problems that were not traditionally experienced in these lakes.  

Most important is the threat they pose to recreational water quality. What is the cause?

Although it is too early to offer a full answer to that question, preliminary findings suggest the presence of one or more human-based stressors operating on a broad, regional scale. There is apparently no correlation between water acidity or increases in total phosphorus and increased chrysophytes. Data indicates that a regional stressor that may be introduced through climate change might be impacting on the changes that are being experienced.

So while recreational water quality in Muskoka’s lakes and rivers continues to be of high quality, there are some clouds on the horizon reinforcing the earlier position that this is not a time for complacency. Continuing vigilance in monitoring the potential impacts of the changes that are taking place is essential. So, too, are ongoing efforts to strengthen nature’s capacity to respond to both known and potentially harmful stressors impacting on the recreational water quality that is so important in this area.

Setting and implementing high standards for the management of both stormwater and sewage treatment, maintaining healthy wetlands and forests, and enhancing natural vegetation on shorelines and near water bodies, should continue to be high priorities in our watersheds.    

Visit the Muskoka Watershed Council website for your copy of the 2007 Muskoka Watersheds Report Card.