When the holidays end, all that gingerbread, pumpkin pie, and eggnog will leave behind a few souvenir pounds to remind us of the merrymaking. But we're not the only ones who will show evidence of our seasonal feasts. So, in all likelihood, will the Boston waterways.
During the holiday season, research shows, some coastal waters indicate noticeable spikes in their levels of cinnamon, vanilla, and other baking spices. These studies - along with similar research that has revealed significant levels of caffeine in Boston seawater - provide a dramatic illustration of how even the most trivial-seeming human behaviors can influence the marine environment.
"We see these indications of human activity everywhere we go in the coastal ocean," said Rick Keil, a geochemist at the University of Washington. "Anywhere people are living near the coasts, you'll see some sort of remnants from their kitchens getting out into the water. It's very apparent that our fingerprint is everywhere."
Neither caffeine nor spices are thought to pose any serious hazards to humans or sea life when they're present in the marine environment. But the fact that they turn up at all in the water suggests that other, potentially less benign, human waste and contaminants may also be present.
Keil's research on the presence of baking spices in seawater started in the fall of 2006 as a project to convince his dubious undergraduates that there were connections between their everyday lives and his oceanography class.
Any spices that humans put into their mouths also show up in human sewage. Small amounts of these spices persist even after wastewater is treated, and when the treated water gets discharged into the marine environment, so do the spices.
After a brief investigation, Keil found that cinnamon and vanilla were indeed present in nearby Puget Sound and that their concentrations varied over time. The data he collected last year clearly showed a spike in vanilla and cinnamon levels just after Thanksgiving, with levels remaining high until New Year's. This rise, he concluded, was likely a result of all the holiday goodies Seattle residents were eating at that time of year.
This year, Keil has continued to monitor baking spices in Puget Sound and has also expanded his testing to include parsley, sage, rosemary, caffeine, theobromine (a compound in chocolate), and more. This year, he found a marked increase in theobromine just after Valentine's Day, and an even more pronounced spike than last year in baking spices after Thanksgiving.
"There's a real rhythm to how the city seems to behave and then there's a reaction to that in the environment," Keil said.
Bob Chen, a geochemist at the University of Massachusetts, Boston, believes Keil's findings likely apply far beyond Puget Sound. He doesn't know of any researchers who have specifically measured spices in Boston-area water, but if someone went looking for them, he said, "I'm sure they'd be there."
Chen is known for research documenting measurable levels of caffeine in Boston Harbor, Massachusetts Bay, and the Charles River. Studies of caffeine and spices, Chen said, provide a useful way for scientists to assess human influence on local waterways and for the public to understand this relationship.
"Finding common everyday chemicals in the water is a good connection between what we do and how it effects the environment," said Chen, who has also studied the seasonal presence of sunscreen in waterways in the Boston area. "A lot of people don't think about contaminants in that way. . . . Whatever we do is going to impact the waterways."
The Massachusetts Water Resources Authority does not test for spices in the water, said Ria Convery, communications director for the agency.
"I don't even know how you would do that. It's hard enough to figure out how to test for normal contaminants," she said. But she said she was intrigued by the idea that spices could be in the water, joking, "We could sprinkle a little cinnamon out there and see if the whales like it."
