Seasonal Pine Pollen Appears as Yellow Scum on Lake Ontario

Cobourg, ON (June 30, 2026) – The Town of Cobourg’s Environmental Services department would like to inform residents that pine pollen will likely be present and visible on the surface and shores of Lake Ontario.

An accumulation of mustard yellow scum on inland lakes and along the shore and bays of Lake Ontario may be visible through the months of June and July. The yellow scum is pine pollen and should not be mistaken for algae, or spilled paint or petroleum. This is a regular occurrence caused by pollen from surrounding forests being blown into the water by high winds.

For additional information on this trend the Severn Sound Environmental Association provides insight into this yearly phenomenon on their website at severnsound.ca/pollen. Please note that the pollen is not harmful and is not a risk to health. The pollen will eventually decompose or become trapped in the sediment along the shore.

For questions, please contact the Town of Cobourg’s Environmental Services department at 905-372-7332.