UBC students wade in to Lost Lagoon’s water woes
After carp die-offs in Vancouver’s Lost Lagoon, UBC Science students are testing the human-made lake’s murky waters
By Geoff Gilliard
Lost Lagoon is a watery jewel gracing Vancouver’s Stanley Park. It’s one of the main attractions that draw over eight million visitors each year to the forested half of the city’s downtown peninsula. But while the 16-hectare lake is pretty to look at, its murky water is polluted, low in oxygen and thick with algal blooms. The conditions led to the die-off of dozens of carp in the summers of 2021 and 2022.
“Carp are considered a hardy species that can tolerate low-oxygen conditions,” says Dacyn Holinda, the Stanley Park Ecology Society’s (SPES) conservation projects manager. “While we are not particularly concerned that we’re losing carp, as they are an invasive species, we are concerned that the water quality is so poor it’s not suitable for most fish species.”
Part of the problem is that Lost Lagoon is a reclaimed salt marsh tidal flat cut off from the ocean in 1916 to create a freshwater lake stocked for recreational fishing.
“We’ve taken an area that was historically a saltwater ecosystem and we’re trying to make it a freshwater ecosystem,” Holinda says. “Whenever you do that, you always have to compete with natural processes that cause the revision of the ecosystem to it’s initial state. Factors such as groundwater seepage can lead to brackish conditions which can be difficult for fish, and in addition, there are very few natural sources of freshwater input.”
But salt water intrusion isn’t the only issue facing Lost Lagoon. Today, more than 60,000 vehicles travel on a nearby causeway every day — gas, oil, tire particles and metal residue wash into the lagoon every time it rains.
When the causeway was upgraded at the turn of the 21st century, a stormwater management plan was part of the project.
Three connected biofiltration ponds were built in a 3,563 square metre engineered wetland at the northeast corner of the lagoon. The causeway runoff enters a first pond, slowly moves to the second and then the third before flowing into Lost Lagoon. The ponds filter contaminants in two ways. Some contaminants settle into the ponds’ sediments, others are filtered out of the water by nearby plants, which absorb pollutants.
But 20 years after the ponds were put in place, nobody knew if they were working as intended.
Spurred by the carp die-offs, SPES, a volunteer-driven charity that advises the Vancouver Park Board on conservation issues, waded into the problem.
Holinda reached out to University of British Columbia’s Dr. Tara Ivanochko, professor with the Department of Earth, Ocean and Atmospheric Sciences (EOAS), and co-instructor of UBC’s Community Projects in Environmental Science. Together they recruited four EOAS students to assess Lost Lagoon’s water quality.
“We’re really trying to meet the needs of the community,” Dr. Ivanochko says. “This is a core course that all environmental science students are required to take as they transition from being students to practitioners. I run the course a little bit less like a class and more like a professional space.”
The students — Logan Hwang, Samantha Kortekaas, Yinzhi Li and Annabel Tse — provided the project scoping, fieldwork, research and analysis. Samples from the biofiltration ponds and the lagoon would be tested for metal and hydrocarbons based on B.C. Ministry of Environment Water Quality Guidelines.
“Stanley Park provides a novel research system for a lot of groups,” says Holinda, who’s also a UBC Science alumni. “Whenever we create these projects, we always want to make sure our research is practical and addresses a given issue. We’re not just doing science for the sake of doing science. This collaboration with UBC allows us to look into some of these conservation questions so we can learn more about the factors that influence the park’s ecology. From these projects and research, we can make recommendations to the Park Board. There are over 200 parks in Vancouver so there’s lots for them to do already.”
The students took water samples from the first pond closest to the causeway, from the third pond’s outlet into lagoon, and in the lagoon itself. The main substances of concern were aluminum, tin, copper, beryllium, chromium, phosphorus and nitrogen.
Tin was found at extremely high concentrations at all three sites — indicating the ponds may not be effectively filtering this metal. Tin can be very toxic to organisms that get their energy from sunlight, which has indirect impacts on species at higher ecosystem levels. Tin settles into sediments rather than being absorbed by plants. If sediments aren’t dredged from biofiltration ponds after five years, they may not be able to absorb additional tin.
Says Holinda: “When the ponds were built, the initial idea as outlined by the Vancouver Park Board was that sediments must be removed every 10 years to maintain efficiency of the system. Last time the ponds were dredged in 2013 there was 61 tons of sludge and sediment cleared out.”
High concentrations of aluminum were also uncovered in the samples. In high concentrations, aluminum has negative health impacts on fish. Birds and other animals that eat the contaminated fish may also be impacted — aluminum can cause eggshell thinning and low birth weights in chicks.
Chromium was also found at high levels, possibly a result of accumulated brake dust from the nearby causeway. It’s one of the heavy metals most toxic to humans and animals. Only a small amount of chromium can dissolve in water, so it generally accumulates over time.
As the ponds don’t appear to be filtering aluminum, tin and chromium effectively, it’s possible that the sediments are saturated with these metals due to lack of maintenance.
“When I did the literature review I found that copper, zinc and cadmium are taken up by plants and biofiltration systems together,” says Kortekaas, a member of the student team. “All three metals typically taken up by plants were a lot lower in concentrations than we expected. That shows the plants are working well to remove those contaminants from the water before it enters the lagoon.”
Concentrations of phosphorus — which causes eutrophication and phytoplankton blooms — exceeded the guidelines at all sites.
“Phosphorus is naturally occurring, but it shouldn’t be in such elevated levels naturally,” says Tse. “Often phosphorus in water comes from fertilizers but the runoff into Lost Lagoon comes from a wooded area or the causeway. We’re not sure what the source is.”
There was good news. In contrast to these three metals, the levels of copper, zinc and cadmium were within safe limits.
The water samples were also tested for hydrocarbons (gas and oil) and a chemical compound called 6PPD-quinone (from tire particles). Recent research indicates 6PPD-quinone can significantly increase the death rate of coho salmon in streams impacted by high levels ofstormwater runoff. In the case of Lost Lagoon, levels were found to be below those deemed to be harmful. Hydrocarbons were also below the regulatory guidelines.
“That means hydrocarbon contaminants from the road are mostly entering the biofiltration pond which shows it’s doing what it’s supposed to do,” Li says.
Dissolved oxygen levels were above the freshwater threshold, and temperatures across all three sites were within optimal range for carp, indicating anoxia was not a concern in Lost Lagoon when the samples were taken. However, that can change during the summer months when water input from rainfall runoff is reduced.
The students recommend taking measurements of pollutant concentrations in the sediments of the ponds, and that dredging sediments more frequently would decrease toxicity in Lost Lagoon. They also suggested that after dredging, more tests on metals and nutrients should be conducted in December 2023 and February 2024.
“Hopefully this gives the Vancouver Parks Board baseline data that will give them something to work with to improve Lost Lagoon’s water,” Hwang says. “The next logical step is to repeat the sampling next year to see if there’s any improvement in the level of contaminants captured in the sediment. That would give them a solid idea of to handle maintenance going forward.”
“The results from this project are a great start,” Holinda says. “From here, we can start to narrow in on the sources of contamination, with the ultimate goal of finding solutions which the Park Board can implement to improve the health of the lagoon and surrounding area.”
Read the full report Water Quality Analysis of Lost Lagoon and Associated Biofiltration Ponds at Stanley Park.
