Millions of white plastic pellets have washed ashore along Lake Huron in the latest installment of an ongoing environmental mystery that has baffled investigators and threatened local wildlife.
"They show up every few years and we don't know where they're from," said Gord Minielly, mayor of Lambton Shores, Ont., one of the municipalities affected. "People have speculated they come from the ballast of ships, but nobody knows for sure."
The lentil-sized flotsam began forming a patchy beard along the lake's southeastern shore in mid-September.
As of Tuesday, reports from locals and the Ontario Environment Ministry suggested the intermittent white ribbon extended 170 kilometres from beaches in the south to Kincardine in the north. While the pellets blend in along the fine-grained beaches that make the area a summer tourist destination, aquatic researchers and conservationists warn that they may also be disappearing into the gullets of local wildlife - a deadly trend that has killed scores of fish and birds in marine ecosystems.
"In ocean environments, these types of things have become a chronic hazard," said Geoff Peach, coastal resources manager with the Lake Huron Centre for Coastal Conservation. "Scientists have identified this as a major long-term problem."
Less is known about the effects of plastic pollution on freshwater environments. The province has received no reports of dead wildlife so far in the most recent outbreak.
This marks the fourth time that a mass tidewrack of pellets has appeared on Huron's shores in recent years. "I first heard about these in 2007," Mr. Peach said. "It keeps recurring and no one seems to be investigating."
The region around Sarnia is known as Chemical Valley, home to a number of industrial manufacturers. Researchers have stated that plastic plants in the valley could be the source, but two bodies of evidence suggest otherwise.
For one, currents in Lake Huron tend to flow south, according to Mr. Peach, not north toward the worst-hit beaches. And second, provincial investigators recently brought sample pellets to a number of valley manufacturers in search of similar bits among their plastic stocks. "Unfortunately no matches were found," said Environment Ministry spokeswoman Kate Jordan.
But a forthcoming study from the University of Western Ontario suggests that the concentration of pellets on Huron beaches increases with proximity to Chemical Valley. Matt Zbyszewski, a University of Western Ontario earth sciences masters' candidate, and his supervisor, associate professor Patricia Corcoran, found that 94 per cent of the plastic litter on one Sarnia beach was made up of the offending pellets. The concentration thinned out considerably as the researchers travelled north.
"It's very unlikely you'll find any pellets up north around Georgian Bay," Dr. Corcoran said. "There are no plastic plants up there. It would be sensible to at least suggest these plants are a possible source."