'Red tide' algal blooms appearing around B.C. coastal waters

A species commonly referred to as “red tide” has been spotted around B.C. coastal waters over the past month.

Blooms are blood red or dark orange in colour, and can be toxic to fish in extreme cases

Noctiluca scintillans has been spotted along coastal B.C. over the past month, including in the community of Saltair. (Murray Welte)

A species of algal bloom called Noctiluca scintillans — commonly referred to as "red tide" — has been spotted around B.C. coastal waters over the past month. 

The Department of Fisheries and Oceans (DFO) says sightings of the colourful microscopic marine algae have been made in North Vancouver, White Rock, Powell River, Sechelt, and the Gulf Islands. 

"It's been around probably the last two or three weeks I'd say," said North Vancouver resident Giovanna Boniface. 

"We stay away from it, we don't go in," said Jeff Boniface. "Our daughter was on the beach in Deep Cove last week and they really wanted to go in because it was hot, but it was pretty red all the way up to the beach so they didn't go in."

Two kinds of 'red tide'

Some people may confuse Noctiluca scintillans with red tide poisoning, which refers to a colourless algae that can be toxic to bivalve shellfish, including oysters, clams, scallops and mussels.

If these shellfish are eaten by humans, it can lead to serious and potentially fatal illnesses such as paralytic shellfish poisoning and amnesic shellfish poisoning. 

The colourful algae, on the other hand, isn't harmful to humans, says Elysha Gordon, Canadian shellfish sanitation program coordinator with the DFO.

"It's somewhat alarming to people because of its beautiful colour, but it's not necessarily what everybody refers to as red tide," Gordon said.

"This particular species can be toxic to fish in that it can clog the gills and cause them to suffocate, but again, not necessarily one that is toxic to bivalve shellfish."

A bloom of Noctiluca scintillans pictured from the air above the Powell River area. (Nell Dragovan)

Blooms caused by warmer temperatures

Gordon says algal blooms occur for a number of reasons, including warmer temperatures, salinity, upwelling and wind.

She says they usually occur from May to September, but climate change and higher extreme temperatures have made them more prevalent, popping up even during the winter months.

Gordon said that while this particular species of algae is not very harmful, there could be multiple species of algae blooming at the same time.

"We just always ask people to make sure that they check to see whether the [fishing] area is open, and that shellfish are safe to consumer before harvesting them, especially in the warmer weather."

The DFO posts general biotoxin safety information, and updates its coastwide list of closures throughout the week based on recommendations from Environment Canada and the Canadian Food Inspection Agency. 

Noctiluca scintillans, a species of algal bloom, off Saltair on Vancouver Island. (Murray Welte)

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Cory Correia

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Cory Correia is a reporter with CBC Vancouver. Send him an email at cory.correia@cbc.ca