Re: Algae in Quamichan Lake
I agree that benchmark testing and warning signs are good first steps in working with this problem.
Next comes the hard part. Longtime residents say there has been a problem with the water for many years. The lake is not self-flushing during the dry summer months, so there is lots of opportunity to grow algae. Recently the situation has become worse. So what has changed? Here is a postulation.
The lake is a catch basin for the runoff from farms, paved roads, and many hundreds of houses. Asphalt pavement and asphalt roof shingles both leach out toxic bitumens. Septic tanks provide nitrates and some detergent phosphates. Farms and gardens leach out nitrates and phosphates. None of this can be good for water quality.
A couple of years ago there was a self-imposed a ban on the use of zinc sulfate to control roof moss. Zinc sulfate kills moss, mold and algae. But you can’t find zinc sulfate for sale anywhere on the island any more. To add to the problem, many people have reverted to the use of cheap laundry detergents to control moss. It works, but the result is two-fold. The detergent may contain phosphates, which will encourage algae growth. The detergents are also strong enough to dissolve and prematurely remove the asphalt binder from roofing shingles. So now there is an extra volume of asphalt leaching into the lake, in addition to the detergent phosphates. I’m not a biology major but none of this can be good for the lake.
Bruce R. Matthews
Duncan
