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Back to the future Ph.D. student mines ancient coastal middens to inform fisheries challenged by warming Gulf of Maine waters by Beth Staples | Photography by Adam Kuykendall
Sky Heller

In Sky Heller’s lab on campus, there is more than a ton of soil containing 4,200-year-old fish remains and shells.

At age 7, Sky Heller was captivated digging through a trash heap protruding from an eroding bank near her family’s old farm in the foothills of rural Pennsylvania.

“When I found out I could do it for a career, I’ve never looked back,” says the Ph.D. student in anthropology and environmental policy at the University of Maine.

These days, the only looking back Heller does is to explore the past with the intent to inform the future.

It’s important to her that archaeology — or knowledge gained from studying past humans through material remains — is directly relevant for people today.

So for her Ph.D. project, Heller is analyzing 4,200-year-old small fish bones from middens — ancient trash heaps — along the coast with the goal of benefiting future fisheries in the continually warming Gulf of Maine.

As she told visiting middle-school students at the Hudson Museum’s Archaeology Day: “I look at people’s garbage and figure out what they ate.”

Zooarchaeology — analysis of animal remains from archaeological sites — reveals what people ate and what the environment was like during a time period.

In addition to answering an interesting archaeological question and filling a gap in New England history, Heller’s findings may prove useful to people who want to catch fish in the Gulf of Maine today…like people have for the past 10,000 years.

Scientists say the Gulf — sometimes called a sea within a sea — is warming faster than 99 percent of the planet’s oceans.

Since the early 1980s, the temperature in the Gulf of Maine, which extends from Cape Sable in Nova Scotia to Cape Cod in Massachusetts, has annually climbed about a half-degree.

Estimates indicate its temperature will climb another 4 degrees Fahrenheit by the end of this century.

To prepare for that future, Heller is investigating what the Gulf’s ecosystem was like 4,200 years ago. It was warm then too, although likely because of how it developed as a body of water rather than because of human-caused climate change.

To learn which small fish species thrived then in the Gulf of Maine, Heller excavated three rapidly eroding archaeological sites from the Archaic period (approximately 10,000 to 3,000 years ago) along the coast of Maine and New Hampshire.

Many days last summer, Heller and a research team dug at a site in Seabrook Marsh, in the shadow of Seabrook Station Nuclear Power Plant in New Hampshire.


During summer 2015, Sky Heller and a research team dug at an archaeological site in Seabrook Marsh in New Hampshire. Heller will examine tiny fish bones and shell remains found in the excavated soil to learn which small fish species thrived around 4,000 years ago in the Gulf of Maine.

To reach the midden, they timed the outgoing tide to have enough water to paddle canoes from the launch site through a canal to the bay, then toward the site in a saltmarsh in another canal.

When the midden was exposed during a four-hour window around low tide, the team dug, took photographs and did paperwork.

The results of their labor: more than a ton of soil containing 3,600- to 4,200-year-old tiny fish bones and shell remnants.

That soil now fills more than 100 plastic one-gallon bags in Heller’s lab in the basement of South Stevens Hall.

Last year, Heller also excavated a site in Blue Hill, Maine. And before that she collected fish remains and shells from a site in Sorrento, Maine.

She says it was critical to complete excavation at these valuable sites because sea-level rise and extreme weather are swiftly eroding them.

The team also collected soil for future archaeologists to have material to explore questions they want to answer about the same time period.

Heller says prior research, including that conducted by UMaine Professor Emeritus Dave Sanger, revealed that swordfish, a warm water species, lived in the Gulf of Maine until about 4,200 years ago.

Swordfish remains as well as tools made from the upper jaws of the predatory fish have been recovered in the area.

But around 4,200 years ago, Heller says swordfish — which move to warmer water in the winter and cooler water in the summer — suddenly disappeared from the Gulf of Maine.

And oysters and quahogs, which are no longer present in significant numbers in the Gulf, also existed then in large quantities.

The reason, she says, may involve currents.

Magnifying glass

Sky Heller examines soil for fish bone fragments.

Today, the cold water in the Labrador Current flowing south from the Arctic Ocean feeds the Gulf of Maine.

But when the Gulf formed around 15,000 years ago during the glacial retreat, the Labrador Current may have been weaker. In that scenario, the powerful Gulf Stream that originates in the Gulf of Mexico could have coursed into the Gulf of Maine.

And fish that follow the warm Gulf Stream, including swordfish and other smaller warm water species, would have come with it.

During prior digs at the sites, Heller says archaeologists didn’t screen for tiny bones of small fish.

So the small fish bones she identifies and analyzes may provide insight into what a healthy, warm Gulf of Maine ecosystem was like prior to massive fishing pressure.

It also could provide information about how the abrupt cooling affected the Gulf of Maine ecosystem and the marine resources that people relied on culturally and economically.

The record, says Heller, will reveal changes in marine species’ ranges in what’s called a temperature-driven alternate ecological state.

The Gulf, she adds, may be returning to such a state.

In 2012, NOAA reported the average sea surface temperature from the Gulf of Maine to Cape Hatteras, North Carolina was the warmest in 150 years (57.2 degrees F). The prior 30-year average was 54.3 degrees F.

The warming has resulted in consequences for those who fish the waters, says Heller. Ripple effects of the record-setting ocean heat wave of summer 2012 included an early glut of lobsters in Maine and the subsequent price crash.

Lobsters and cod are two traditional Gulf species that are on the move north into cooler waters, says Heller. And black sea bass also are moving north — farther into the Gulf.

According to a 2009 NOAA report, for 40 years, half of 36 fish stocks being studied in the Northwest Atlantic Ocean have been migrating north.

During her doctoral project, Heller is exploring a number of topics, including fish behavior, biology and fish morphology, tides and ocean circulation in the Gulf of Maine and North Atlantic region, fisheries policy, archaeological theory and anthropological theory.

“I was accused once of having academic schizophrenia,” she laughs. ”With archaeology, it’s all right to be interested in everything.”

Heller will share her findings with people who fish for a living and with marine stakeholders who craft conservation and sustainability policies aimed at helping fisheries adapt as the Gulf warms.

Heller earned her master’s in quaternary climate studies with a focus in prehistoric archaeology from the university’s Climate Change Institute and is a Chase Distinguished Research Assistant.

Tools that archaeologists dig: Notebook, camera, trowel, screen and marker.

Tools that archaeologists dig: Notebook, camera, trowel, screen and marker.

For two years, she was an Integrative Graduate Education and Research Traineeship (IGERT) Research Fellow. IGERT, sponsored by the National Science Foundation, is a joint program of CCI and the School of Policy and International Affairs. Its focus is adaptation to abrupt climate change.

Heller’s Seabrook Marsh excavation team included: Brian Robinson, her adviser and an associate professor in the Department of Anthropology and Climate Change Institute; undergraduate Emily Blackwood, an anthropology major from Auburn, Maine; and Peter Leach, a doctoral student at the University of Connecticut who earned his master’s and undergraduate degrees at UMaine.

Heller calls Robinson one of “more frighteningly intelligent people I’ve ever met.”

She appreciates that he keeps her on her toes, finds unique approaches to problems, hones in on weaknesses in arguments and deals with her inherent skepticism by giving her time to research an idea on her own.

The excavation team also included Heller’s husband, Andrew Heller, an archaeologist with a master’s degree from the University of Arkansas; and Richard Boisvert, state archaeologist for New Hampshire.

Nearly three decades after Heller uncovered treasures — including old bottles and an alarm clock — in a trash heap at her parents’ farm in the Keystone State, she’s recovered fish bones from 4,200-year-old debris piles on the coast of Maine and New Hampshire.

She credits her parents, Kelvin and Robin Flynn — who operated a maple business with 1,500 taps and a wood-fired evaporator — with fostering her tenacity, independence, interest in working with her hands and sense of humor.

“They taught me that you finish what you start, you always do your best and don’t worry about what others are doing, and the person you really have to answer to at the end of the day is yourself,” she says.

The future Gulf of Maine ecosystem may well benefit from her curiosity and doggedness to find answers.

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