Signage is being erected in Killarney due to the potential for an algal scum on one of the lakes.
Kerry County Council is placing the signs on the shore of Lough Leane today as the scum can be harmful to small animals.
It follows samples taken from the lakes in recent days by council staff; laboratory tests have confirmed the presence of a blue-green algae which could form a scum.
Dog owners are being advised to keep their pets on a leash and not allow them to enter the water.
The council is monitoring the situation on a daily basis.