What’s killing the world’s scallops and oysters?

Vancouver, BC – Many scallops are not even growing to be fully-sized, as higher ocean acidity and other potential problems kill them when they are only seedlings.

Farmed scallops and oysters are dying at devastating rates worldwide and an interdisciplinary team of scientists has assembled to investigate why.

CIFAR senior fellow Curtis Suttle, also a professor with the Department of Earth and Ocean Sciences at the University of British Columbia, is an expert in ocean viruses and one of the biologists on the team of ecologists, geneticists, epidemiologists, shellfish growers and other experts set to study the problem. The group has applied for Genome Canada funding to research the mass die-offs of aquaculture scallops and oysters affecting Western Canada, Europe, China and elsewhere.

“It’s to the point that it’s almost catastrophic, at least in terms of the shellfish industry on the west coast,” says Suttle.

UBC professor Chris Harley recruited Suttle to the project after shell fish producers asked for help to save their dying populations. Harley estimates the BC aquaculture industry could collapse within the next few years if the problem isn’t solved. But what is the problem?

It’s complex, and scientists don’t know how many factors might be contributing to the shell fish demise. However, Suttle says one aspect is clear: a buildup of CO₂ in the atmosphere is making the ocean more acidic. Acid dissolves the calcium carbonate that makes up the shells of scallops, oysters and other fish in the group called bivalves. Higher levels of acidity in ocean water make it harder for seedling oysters and scallops to produce a strong shell, and many of them die before growing into baby shell fish. In addition, they seem to be more susceptible to parasites and diseases.

“You have a whole bunch of things going on,” says Suttle. “You have the shell fish being weakened by increased acidity and making it more difficult to produce hard shells. You’ve probably got an immune system that’s being compromised because the bivalve is not growing under ideal conditions, and on top of that you’ve got this issue of increased susceptibility to pathogens,” he adds.

Scientists don’t know how all of these factors play into the problem, and they know very little about how scallops and oysters are faring in the wild. They plan to study shell fish environments and genomics for answers to these questions, as well as try to discover new viruses and other pathogens.

Suttle and Kristi Miller at Fisheries and Oceans Canada will be screening populations to learn whether new and emerging pathogens could be major killers of these populations, as they were recently found to be in sea stars.

Suttle, who is part of the program in Integrated Microbial Biodiversity, says this project exemplifies the type of questions that CIFAR researchers take on.

“Why this is in some ways a CIFAR problem is the fact that in order to try and address this you need people from so many different backgrounds and expertise,” he says.

The team expects to learn in January if Genome Canada will invite them to submit a full proposal for funding consideration.

Reported by Lindsay Jolivet, CIFAR