Tuesday, Aug. 16, 2011 – If you have visited the waterfront recently, you’ve likely noticed a foul odour coming from the shores of Lake Ontario — a perennial summer problem caused by Cladophora algae. The algae pose no health threat, but it can keep visitors and residents from enjoying this natural jewel.

As water temperatures rise in summer, strands of green Cladophora algae grow quickly on the bottom and shorelines of Lake Ontario, connecting to hard surfaces such as rocks, concrete and metal retaining walls. Cladophora algae soon die and wash up on the shore, producing a foul odour.

“Phosphorus is the key reason algae are out of control in Lake Ontario,” said Kate Hayes, Project Manager for Credit Valley Conservation (CVC), adding that some of the main sources of phosphorus are fertilizers, and sewage (both human and animal).

The Credit River runs downstream through urban and rural areas, picking up phosphorus and other pollutants such as ammonia, heavy metals and chlorides, which drain into Lake Ontario. Non-native zebra and quagga mussels in the lake also trap phosphorus near the shore. At the same time, urban growth along the shoreline has wiped out many wetlands and natural habitats that could circulate and help clean water.

To help protect water quality, here are a few ways to help:

  • Reduce using pesticides, fertilizers and road salt which make their way to the lake through groundwater and storm sewers.
  • Choose native species for your garden and reduce lawn space for more natural landscaping, which supports a healthier eco-system and requires less fertilizer and other chemicals.
  • Improve the ability of rainwater to soak into the ground by using permeable pavement, reducing paved spaces and routing downspouts into the garden.
  • Get involved. Make sure your local, provincial and federal elected officials know you care about protecting the shoreline. Visit http://www.creditvalleyca.ca/watershed-science/living-by-the-lake to learn more.

Lake Ontario’s shoreline suffers from the effects of urban living, but it can be improved. CVC is taking action through development of a Lake Ontario Integrated Shoreline Strategy (LOISS), which will look at water quality, quantity and wildlife habitat of this important natural resource.

More than eight million people rely on Lake Ontario for drinking water. The shoreline is home to more than 200 globally-rare plants and animals, including 40 species found nowhere else in the world. Lake Ontario’s shoreline is also a popular tourist destination for anglers and residents in the Region of Peel and visitors from around the world.

With municipal and agency partners, CVC will gather information through LOISS about how local residents and visitors view and use Lake Ontario’s shoreline, with particular emphasis on natural elements. Information will also assist in planning conservation and restoration projects to meet environmental and community needs.


Conservation Authorities are a provincial/municipal partnership. CVC was established by an act of the province in 1954 with a mandate to protect all natural resources other than minerals in the area drained by the Credit River. We have been working for over 50 years with our partner municipalities and stakeholders to protect and enhance the natural environment of the Credit River Watershed for present and future generations.


Kate Hayes

Project Leader – Restoration and Stewardship

Credit Valley Conservation

905-670-1615 ext. 428

[email protected]

Bethany Lee

Community Relations

Credit Valley Conservation

905-670-1615 ext. 385

[email protected]

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