Elevated levels of phosphorous in the Bedford West watershed have triggered an investigation to find out the cause.

The watershed area includes the popular recreation spots of Paper Mill and Kearney Lakes.

"Phosphorous can cause algae growth. That tends to form a green scum on the surface." said Jocelyn Rankin, a freshwater expert with the Ecology Action Centre.

"If the phosphorous inputs continue, that can consume all of the oxygen in the lake and essentially choke out all the living creatures in the lake."

Municipal officials have been taking water samples from 11 locations in the Bedford West watershed since 2009.

The results from the summer of 2013 and the fall of 2014 show levels of phosphorous that exceeded the recommended levels at most of the stations, most of the time, and in some cases, by substantial amounts.

Due to a planning policy for water quality, those results require a more in-depth study.

Officials expect to hire a consultant this fall.

'I'm very concerned'

"Phosphorous can come from organic matter, run-off from fertilizer or agricultural production." Rankin said.

"Also, urban development can increase hard surfaces and then you can have more stormwater run-off."

Regional Council has designated around 800 hectares in the Bedford West area as a priority for development. Thousands of new homes are expected to be built over the next 20 years.

"I'm very concerned," said Tim Outhit, who represents District 16 Bedford-Wentworth.

"That's why I've asked for a presentation in September on the water quality results at the North West Community Council."

Outhit also wants to know what impact a three-year-long project to repair the Paper Mill Lake Dam had on water quality.

The lake was drained to allow the repairs to take place.