New research from Dartmouth shows one type of seabird in the Gulf of Maine, the black guillemot, has concentrations of mercury in their feathers that are above levels known to have effects on reproduction in other species.
The study also looked at common terns and roseate terns, which had lower levels of mercury. That’s explained in part by the different diets of the birds; guillemots eat fish that are higher on the food chain, and may have accumulated more mercury.
Lenny Laird did the research as part of their undergraduate thesis, while working as a research technician in the lab of Dr. Celia Chen. They spent a summer on the Isles of Shoals, looking for birds’ nests, checking on newly hatched chicks, taking down feathers and the contour feathers they develop as they grow. Laird focused on measuring levels of mercury – a harmful neurotoxin.
“Even though mercury levels might be decreasing worldwide, it’s still a persistent problem in the Gulf of Maine,” they said. “It's still there in the food web. And it's still reaching levels in species like the guillemots, where it could potentially affect hatching and success of some of those populations.”
They said part of why the research is important is that it helps give a big picture of mercury in the ocean in general.
“If you're trying to test contaminants in the ocean, there's just a huge number of things that you could possibly look at,” Laird said. “You could test water levels, or you could test levels in different species of fish or mammals. There’s just a huge, overwhelming number of places you could be looking for contaminants.”
But seabirds travel long distances and feed on a variety of fish that are high on the food chain, they said, so studying their levels of mercury can give an overview of what’s happening on a larger scale, in this case, the Gulf of Maine.
Celia Chen, a research professor at Dartmouth who advised Laird on the research, said one of the important takeaways is that black guillemots may be at risk of negative health impacts. But the study also provides evidence that the birds could be a good candidate for further studies on the reach of mercury. Because they’re not threatened or endangered, black guillemots could be a species scientists use to monitor the health of the surrounding environment.
As international efforts to limit mercury emissions continue, Chen says monitoring species like these birds could help show if those efforts are working.
“If we, in terms of regulation management, control sources, we also need to know whether controlling those sources actually has any impact on these endpoints: human biota, the environment in general,” she said.
Scientists across the world are starting to gather data on the baseline levels of mercury in the environment. They’ll compare levels in five years and in ten years to determine how things are changing.
“What we need is good temporal data,” she said. “You have to start somewhere.”
Laird’s undergraduate research is one snapshot, Chen said. Other researchers could do more measurements in years to come, filling in more of the picture.
