September 8, 2013

What are these animals telling us?

Because they are sensitive to change, so-called ‘sentinel species’ can reveal a lot about the ripple effects of pollutants in our environment. And that, scientists say, serves as a warning about our own fragile future.

By North Cairn
Staff Writer

Working in Acadia National Park one recent morning, Sarah Nelson, a biological geochemist at the University of Maine, stood with her five assistants in boots and waders and jabbed at the sediment on the bottom of Hodgdon and Seal Cove ponds with long-handled nets.

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Green crabs, like these found off Freeport, are considered a “sentinel species,” which can tell us a lot about the ripple effects of mercury, lead and other pollutants.

Gabe Souza/Staff Photographer

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Sentinel species in Maine

Explore how ocean scientists, ecologists and biologists are studying a wide range of “sentinel species” in Maine with our interactive species guide.

Their target was dragonfly larvae, and the samples they took to a lab on campus would be identified, analyzed and finally incinerated.

In the ash they would measure concentrations of mercury, a toxic heavy metal that can wreak havoc on the environment and human health.

For researchers like Nelson, the dragonfly is not just an elegant insect with a voracious appetite for mosquito larvae. It’s also a “sentinel” species, a stand-in for humans that provides clues to potentially harmful environmental conditions we otherwise might not notice.

Fifty years have passed since Rachel Carson first coined the term, but as human impacts on the planet multiply, scientists say it’s still a critical concept for understanding changes in the environment.

“Long-term ecological research (on sentinel species) is absolutely required,” said H. Bruce Rinker, director of scientific advancement at the Biodiversity Research Institute in Gorham. “In order for us to understand us, we need to look at other species.”

The study of sentinel species goes back a long time, arguably to ancient times when the art of augury was practiced. By examining the entrails of certain animals, it was thought, the fate of emperors or the outcomes of battles could be predicted.

The classic sentinel species – at least in America – harks back to the mines of the 19th century. The expression “canary in the coal mine” – once employed to describe the process of releasing a small yellow bird into mine shafts to gauge air quality and the safety of miners – has become a linguistic fixture to illustrate how the fate of one species may portend the circumstances faced by others.

A miner who watched a canary flutter off and fall or head into a tunnel without returning knew not to enter the darkness himself. If the level of toxic gases – usually, carbon monoxide – could kill a bird, the theory held, they could hurt a man, too, or even kill.

“When the canary can no longer breathe, (it’s) a harbinger of human death,” said Patrick Keenan, outreach director at the Gorham institute.

Over time, as scientific investigation has evolved, the canary has been joined by many other species that are monitored for an increasing number and range of reasons, including to predict humans’ safety.

Scientists from state agencies, academic institutions and research laboratories in Maine are studying tiny copepods, certain fish species and larger crustaceans in the ocean, freshwater fish and migratory birds in ponds, loons on inland lakes, moose and bears in the North Woods.

Researchers say many of these studies start on a shoestring and run long-term, their modest funding bolstered by a robust commitment of time and energy from students and volunteer citizen scientists.

The years of monitoring, data collection and scientific inquiry in Maine have begun to pay off in hard facts and sobering realities:

Mercury has spread almost everywhere, sparking international debate and multinational treaties dealing with the pollution.

Lead – once the poster poison of children in older buildings in inner cities – is still the leading cause of death in adult loons, claiming more than one-third of North American loon populations.

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