Who's to blame for contaminated shellfish? Researchers follow the fecal matter to find out

For the shellfish industry, high fecal counts detected in areas where shellfish such as oysters are har‐ vested can mean long - and costly - closures.

The fecal matter is associ‐ ated with human-borne viruses, like norovirus, but the tests that are typically used to measure the fecal matter don't distinguish be‐ tween different types of ani‐ mals, including humans.

That's where a new twoyear program from Genome B.C. comes in. Researchers have begun using molecular testing to determine, broadly, what sort of animal poop is polluting water, with the goal of making it easier to man‐ age the problem, and hope‐ fully reduce long harvesting closures.

"These are methods testing for the DNA present in bacteria, to tell us what the potential source is," said Na‐ talie Prystajecky, the program co-lead, clinical associate professor at the University of British Columbia, and pro‐ gram head for environmental microbiology at the B.C. Cen‐ tre for Disease Control's pub‐ lic health laboratory.

According to Prystajecky, the tests aren't able to ab‐ solutely pinpoint the specific source, but it can point re‐ searchers in the right direc‐ tion.

"In general, the type of fe‐ cal pollution that we're most concerned about is human fecal material, because the bacteria and viruses found in human waste can make hu‐ mans ill," she said, adding that higher fecal counts could be permitted if it's known to not be from hu‐ mans.

Once the type of animal responsible for polluting an area's water is determined, it's easier deal with it.

"If we can put a finger on what the source is by saying, 'yeah, it's not human, it's of bird origin,' it would defi‐ nitely go a long way towards addressing how we manage that contamination," said Nico Prins, executive director of the B.C. Shellfish Growers Association (BCSGA).

Management in the case of animal feces from crea‐ tures like birds or sea lions could mean deterring them from congregating in certain areas like docks. If it's from cattle living upstream, there could be strategies to reduce the issue.

Managing human fecal contamination in the water

For human feces, it can get more complicated in ter‐ ms of who the regulator is, according to Prystajecky, but if it's a source like a leaky septic tank or composting outhouse close to the seashore, that could be ad‐ dressed with repairs or relo‐ cation.

"We can look at certain things like, are there a lot of marine vessels that are trav‐ elling in that transport route nearby?" she said.

According to a report by the environmental group Stand.earth in 2021, the pan‐ demic-era pause in the cruise industry in B.C. resulted in an estimated 220 million litres of sewage, 1.8 billion litres of greywater, and 31 billion litres of washwater being kept out of the Salish and Great Bear seas.

The new testing program will focus on a stretch of the east coast of Vancouver Is‐ land between Deep Bay and Comox. According to Prins, the area is responsible for as much as 70 per cent of the half-shell oysters produced in the B.C. shellfish industry, as well as nearly half of its revenue.

Shellfish are excellent product filters, explained Prins, with an adult able to filter 150-190 litres of seawa‐ ter per day. They're excep‐ tional at concentrating the particles, including potential toxins or contaminants that could make someone sick.

"It's not necessarily the shellfish that are sensitive to it, it is the consumers of the shellfish that are potentially sensitive to it," he said.

The Genome B.C. research project is being carried out in partnership with the BCSGA and Malahat Nation.