The 50-cent reward advertised on a strange, yellow disc, found propped against a recycling bin after washing up on Long Beach, made Jacki Aubertin laugh.

"It just cracked me up," said Aubertin, a Parks Canada janitor at Pacific Rim National Park Reserve, who cleaned the disc so she could read the inscription.

"I thought: 'How cheap is that? It wouldn't even cover the postage.'"

But the real reward was a story spanning 40 years that started near the Golden Gate Bridge in San Francisco.

Aubertin took the plastic floater, which gave the return address of the U.S. Geological Survey in California, to Parks Canada colleagues, and ecosystem scientist John McIntosh wrote a letter to the USGS explaining where it was found. "We will happily forgo the 50-cent reward in the interests of science," he wrote.

After two months passed without a response, the mystery of the yellow disc became a joke among staff. Aubertin was even presented with a fake letter from President Barack Obama, with two U.S. quarters taped to it.

However, this week, letters from the USGS explained the disc was one of a series of "seabed drifters" dropped off in various locations near the bridge in March 1970 as part of a study on water circulation in San Francisco Bay and the adjacent Pacific Ocean. The Long Beach disc was one of the last stragglers from a group of 1,345 drifters.

Instead of 50 cents, Parks Canada staff were offered USGS T-shirts and baseball caps and, as a bonus, USGS contacted research oceanographer emeritus David Peterson, one of the researchers who released the discs.

It was a great surprise to have one of the discs turn up 40 years later, Peterson said. "One turned up in Hawaii about 15 years ago."

The research paper, which looked at how the currents could affect oil spills or drums of radioactive material in the ocean, said 19 per cent of discs recovered were found on beaches seaward of the Golden Gate and 81 per cent were found inside the Golden Gate.

Read more at the source:Vancuever Son