Water temperatures led to fish kill — Langley City
Water tests carried out on Brydon Lagoon, following the recent discovery over the August long weekend of thousands of dead fish along its shoreline, indicate that water temperatures in the shallow Langley City reservoir were likely high enough to kill many of the species that occupy it.
“Temperature was really the key factor (in the fish kill),” City CAO Francis Cheung said on Monday, after a report was issued on the test results.
Measurements taken at both ends of the pond found the water to be quite warm — between 27.4 and 29.9 degrees Celsius.
Low oxygen levels were also cited at the time as a possible cause of the fish kill, with large amounts of decomposing algae singled out as a likely culprit.
However, the City’s water quality tests, carried out by “a senior biologist from an outside organization” found oxygen levels to be between 12.71 and 11.06 parts per million, the report indicated.
That is more than twice the level of four to five ppm that constitutes a healthy environment for most species of fish.
Long periods of hot weather can lead to dense colonies of algae blooms, which can cause significant and detrimental fluctuations in oxygen concentrations.
Cheung acknowledged that the City has had recurring problems with one of its two aeration pumps at Brydon Lagoon frequently shorting out.
Extensive repairs have been carried out on both pumps, but area residents have complained about the noise they generate and so the City is looking at replacing them with quieter models this winter, he said.
“We’ve done a lot (to improve the lagoon) and we will continue to do so,” Cheung said.
Around the same time as the pumps were purchased — about 10 years ago — the City installed a stormsceptor which captures sediment and prevents pollutants in storm water runoff from entering the lagoon.
“We did that at great cost,” said Cheung.
Plans are in also place to improve the outfall of the lagoon into the Nicomekl floodplain, he added.
Calls to dredge the lagoon, meanwhile, are being taken under advisement, said Cheung, but it will be up to council whether to commit to the “very expensive endeavour.”
“Based on the report, it’s not a high priority right now,” said Cheung.
Brydon Lagoon, which was constructed more than 50 years ago as a sewage settlement pond, before being decommissioned in the mid-1980s, has an average depth of 1.25 metres. It was never intended to support a fish habitat, said Cheung.
Fish came to be living in the lagoon because they were either released into the water illegally or were deposited by a flooding Nicomekl River, he added.
While the City has no plans to stock the lagoon, it will continue to maintain it as a viable habitat for the existing fish which draw large flocks of migrating waterfowl each year.
“We fully agree that the lagoon is a gem in the City, and we’re just as concerned (as residents) with the fish kill,” said Cheung.
While Langley Field Naturalist Bob Puls agrees that high water temperatures are to blame for the massive fish kill, he believes low oxygen concentrations also played a roll.
It was a situation that could have been avoided, he said, if the lagoon had been dredged as the LFN has repeatedly requested.
“We’ve been pushing them for years. They’ve tested it, and come up with excuse after excuse.”
A lagoon, like a septic tank, fills up with solid waste and must be cleaned out regularly, Puls said.
“The water level is less than half what it was when the Langley Field Naturalists became involved.”
Proper dredging would double the amount of water in the lagoon, which would in turn take twice as long to heat up, he noted.
He suggested the City could dip into its casino revenue to pay for the work.
Since Cascades Casino opened in 2005, the City has received around $53 million in gaming revenue. It has been used to retire debt and pay for capital projects.
The money has been used to retire the City’s debt, to pay for a new water reservoir and to fund numerous capital projects, including the City’s share of the Roberts Bank Rail Corridor overpass project and a new Timms Recreation Centre which is scheduled to open in December, 2015.Brydon Lagoon is equally deserving of a share of that cash, said Puls.
“They call Brydon Lagoon the jewel of the City. It’s not much of a jewel if you let it fill into a swamp.”
The money has been used to retire the City’s debt, to pay for a new water reservoir and to fund numerous capital projects, including the City’s share of the Roberts Bank Rail Corridor overpass project and a new Timms Recreation Centre which is scheduled to open in December, 2015.