What Is It
Eutrophication collage Researchers tell us that Cultus Lake is in the early stages of cultural eutrophication, or nutrient enrichment.

Cultural eutrophication occurs in a lake when the normal balance of nutrients such as nitrogen and phosphorus becomes skewed. Excessive levels of nutrients trigger a dense growth of plant life, most frequently algae. While this kind of lush growth is desirable in a garden, such an aquatic plant bloom will block out sunlight, absorb oxygen and begin a chain reaction of changes within the body of water. The process will degrade habitat and reduce the oxygen supply for fish and plants. If left unchecked, the lake could become uninhabitable to most aquatic life.

By looking at lake bottom sediment core samples, researchers found Cultus Lake historically had low levels of nutrients and algae. That, coupled with deep, cold water rich in oxygen, made Cultus Lake one of the most productive rearing grounds for its unique sockeye population.

Cultus Lake, British Columbia experiences significant anthropogenic nutrient loadings and eutrophication. If continued unabated, these stresses threaten the persistence of two resident species at risk (coastrange sculpin and Cultus Lake sockeye salmon) and the many ecosystem services provided by the lake.
However, the lake’s chemistry has changed unequivocally since the 1950’s, when human activity began to increase in and around Cultus Lake. In a recent study partially facilitated through CLASS, researchers traced the influx of nitrogen and phosphorus to local agriculture, Cultus Lake septic fields and air-borne deposits. Additionally, up to 12,000 gulls deposit their phosphorus-loaded waste into the water when they roost at the lake overnight in winter, after feeding in farm fields and the nearby Bailey Landfill.

The process of eutrophication is further propelled by climate change and the ensuing increase in lake water temperatures.

Today, the genetically distinct Cultus Lake sockeye salmon is on the Committee on the Status of Endangered Wildlife in Canada (COSEWIC 2003) endangered list. As well, the unique Cultus Pygmy Sculpin is a SARA-listed, threatened species.

But according to researchers such as Dr. Dan Selbie, a respected limnologist and lead scientist at the DFO Research Lab at Cultus Lake, the early symptoms of eutrophication can be reversed.

Dr. Daniel T. Selbie,
Adjunct Professor, Simon Fraser University School of Resource Environmental Management
Head of the Lakes Research Program, Fisheries and Oceans Canada :
January 22 2015
presentation on Eutrophication in Cultus Lake

press release: BC’s Cultus Lake at Risk from Nutrient Loading pdf document (Jan. 22, 2015 – CLASS)
news: Water quality threatened at Cultus Lake says Research (Chilliwack Progress, Jan.19)
press release: Cultus Lake water quality degradation can be reversed pdf document (Jan. 29, 2015 – CLASS)