Bates environmental economist Lynne Lewis. Photograph by Phyllis Graber Jensen/Bates College.

“Desperate Alewives,” a Maine Public Broadcasting Network documentary featuring Bates environmental economist Lynne Lewis among others, has been nominated for a New England Emmy in the category of Outstanding Environmental Program. The program is part of the MPBN series Sustainable Maine.

The 35th Annual Boston/New England Emmy Awards, sponsored by the National Academy of Television Arts & Sciences Boston/New England chapter, will be presented June 2 in Boston.

A river herring called the alewife — aka sawbelly, mooneye, gaspereau and big-eyed or spring herring — is an essential component in the fresh- and saltwater food chain along much of the Eastern Seaboard. In Maine, alewife populations have plummeted, prompting research by a group whose members include scholars from Bates, Bowdoin College and the University of Southern Maine, many of whom are featured in the MPBN segment.

Watch Desperate Alewives.

“I think if we don’t care, it’ll be too late,” Lewis says. “Policymakers always want to know the costs and benefits — and the costs of these decisions always tend to be very localized, the politics very intense, about taking out a dam or putting in a fish ladder.

“But the benefits accrue to so many different people: to the anglers, to the property owners, to the codfishery, to the lobster fishery.”

Associate Professor of Geology Beverly Johnson.

Lewis and her Bates colleague Beverly Johnson, a geology professor depicted in the documentary, are collaborating with faculty from Bowdoin and USM on the project “Maine Rivers, Estuaries and Coastal Fisheries,” funded by the National Science Foundation’s Office of Experimental Programs to Stimulate Competitive Research (ESPCoR) through a grant to the University of Maine’s Sustainability Solutions Initiative.

That initiative is designed to connect research with concrete action that promotes the economy, vibrant communities and healthy ecosystems in and beyond Maine.

Funded by the National Science Foundation, the collaboration will weigh the costs and benefits of river rehabilitation in Maine and the effects of rehabilitation efforts on fisheries and economies.

Chair of Bates’ economics department, Lewis’ own research explores the potential benefits and costs of river rehabilitation and, specifically, dam removal.

Johnson’s research seeks to reconstruct the Gulf of Maine’s ancient nearshore ecosystem in order to help scientists predict current responses to natural and human influences. Funded by a $393,000 NSF grant, that interdisciplinary project also includes biologist Will Ambrose and archeologist Bruce Bourque of Bates and Robert Steneck of UMaine’s School of Marine Sciences.

In Kongsfjorden on the west side of Svalbard, Will Ambrose (facing) and Kelton McMahon ’05 haul a dredge to collect Serripes groenlandicus and other clam species for McMahon’s thesis in 2004. Photograph by Glenn Lopez, SUNY–Stony Brook.

Professor Will Ambrose, a bearded biologist specializing in Arctic sea-floor ecology, is a pioneer in the science of deciphering the past — including past climates — by studying the annual hard-tissue accretions of organisms such as mollusks.

As an expert in sclerochronology, Ambrose has discovered a link between Arctic clam growth and regular shifts in the region’s climate. In short, Arctic clams grow more rapidly during regimes of warm and wet weather and less during cold and dry regimes. This sensitivity to climate change, says Ambrose, makes the humble bivalve a “sentinel of climate change.”

While Ambrose is collaborating on no fewer than five clamshell research projects at the moment, the scientific paper that detailed the initial findings of a correlation between climate change and Arctic clamshells appeared in Global Change Biology in September 2006.

Seen here is the cross section of a small portion of aSerripes groenlandicus shell, near the umbo, or hinge. The lines indicate annual growth: dark lines for slow winter growth; light areas indicate fast summer growth. For an image showing the complete shell, click the image above. Will Ambrose has discovered a correlation between growth and climate shifts. This image is a composite of 18 images produced by the College’s new Imaging and Computing Center using a Nikon SMZ 1500 stereo microscope. Collected in 1926, the shell’s actual length is 2.5 inches.

The paper emerged from work done three years earlier, when Ambrose dispatched divers to the bottom of a high Arctic fjord in the Svalbard archipelago, a popular Arctic research site about halfway between the Norwegian mainland and the North Pole. From the ocean bottom, the divers returned with four Greenland cockles (Serripes groenlandicus).

After encasing the shells in epoxy and slicing them apart, Ambrose and a team of scientists, including Kelton McMahon ’05, analyzed the growth bands. First, the team found that growth bands were indeed deposited annually. Then the team was able to correlate annual differences in shell growth with a measurement of Arctic weather oscillations known as the Arctic Climate Regime Index.

“What makes the work exciting,” says Ambrose, interviewed in his cluttered office on Carnegie’s third floor, “is that this is the first time in the Arctic that we’ve been able to track a large-scale climatic oscillation and see that large-scale regional event reflected in animals living on the bottom.”

While scientists have for decades analyzed growth lines in shells (Ambrose and others call them “trees of the sea”) in order to reconstruct past environments, the intensity around climate-change research has “really made the field of sclerochronology take off,” he says.

In this hot field, Ambrose’s research is distinctive for its location, on the Arctic continental shelf. “A lot of the work has been done at lower latitudes, mostly because it’s harder to get clams in the Arctic and there are simply fewer people available to help,” he says. “That’s why we’re ahead of the ball.”

If it’s true that Arctic clams grow faster in warmer weather (and grow faster when there’s less of a seasonal ice pack, another signal that Ambrose saw hints of), a simplistic response might be, “Great — fatter clams for walruses to munch on.” But, explains Ambrose, fat clams won’t offset the problems walruses are having due to less pack ice to rest on. And less ice will also affect tiny creatures inside the ice that are the first link in a food chain for polar cod, seabirds, and seals. And so on, throughout the Arctic food web.

These Serripes groenlandicus clams were collected in Storfjord at a site last visited by 19th-century Russian explorers. Photograph by Greg Henkes '08.

In the end, changes in water temperature and salinity (due to runoff from melting glaciers) and increased sea levels, leading to erosion and turbidity, will all take their toll on the Arctic ecology. “Ecosystems operate at the interface of physics, chemistry, and biology, with both complementary and contradictory interactions,” Ambrose writes in a forthcoming article predicting that “regional, and perhaps global, biodiversity will suffer.”

Until recently, Ambrose researched other organisms of the benthic community, such as bloodworms along Maine’s coast. A simple matter of funding helped bring bivalves into focus, as a Bates grant (from the Philip J. Otis Endowment) and an external one (from the Howard Hughes Medical Institute) helped purchase a pricey Isomet low-speed saw for preparing shell cross-sections. “Very expensive,” Ambrose says.

In researching the biological response of Arctic bivalves to climate change, Ambrose has depended on the interests and expertise of colleagues and students at Bates and abroad.

Geology professor Beverly Johnson, for example, has been invaluable in co-advising biology students so they can learn to use the College’s stable isotope ratio mass spectrometer, a tool to help identify the age and origins of molecules in various materials. Johnson herself has used the instrument to look at amino acids in dinosaur eggs, and it can likewise be used to tease out the chemical components of clamshells.

“I work with Will to understand how modern systems work,” says Johnson, “and then go back to old shells, using the geochemistry of shells from 125,000 years ago to reconstruct the environment.”

Ambrose also depends on Matt Duvall, who directs Bates’ new Imaging Center, to create elegant microscopic images of his clamshell sections that Ambrose calls “just incredible.”

Geology professor Mike Retelle, another Svalbard regular who specializes in reconstructing climates from lake sediments, has collaborated with Ambrose on researching climate-change information from fossilized Ice Age clams.

Beyond the sciences, Ambrose, Johnson, and Retelle belong to an informal North Atlantic Study Group on campus that also includes archeologists Gerald Bigelow and Bruce Bourque, historian Michael Jones, and political scientist Áslaug Ásgeirsdóttir. What started informal — an interdisciplinary coffee klatsch — has given rise to “North Atlantic Studies,” a thematic grouping of Bates courses, known as a concentration, under the College’s new general education requirements. “We represent an area of study, rather than just a bunch of us sitting around having coffee,” Ambrose says.

“It’s a truly special group,” Retelle adds. “The richness of discussion is such that the boundaries between disciplines disappear. The walls of the box dissolve. Will is a big part of that. As a model for an undergraduate institution, Will has really raised the bar.”

Ambrose himself is quick to point out that “students here are the ones driving the bus in terms of getting the work done.” As he speaks, Greg Henkes ’08 of Chapel Hill, N.C., is downstairs in the environmental geochemistry lab cutting shells and extracting organic material. Henkes’ senior thesis involves a study of 130 years of climate change in the Barents Sea and Svalbard using a historic Russian collection of Serripes groenlandicus. He will present his findings to an American Geophysical Union conference in San Francisco.

Greg Henkes ’08, one of Will Ambrose’s thesis students, took this photograph at 3 a.m. on June 3, 2007, as the research shipLance heads through sea ice in Storfjord in the Svalbard archipelago, about halfway between the North Pole and Norway.

“It’s pretty incredible to be able to do this at Bates,” says Henkes. “It’s the way science is going,” says Ambrose of the collaborative nature of scientific enquiry, noting his international partnerships with colleagues at the Norwegian Polar Institute and the research firm Akvaplan-niva. “People aren’t doing their own little thing anymore.”

“That’s the way science should be done,” emphasizes Kelton McMahon, co-author of the Serripes groenlandicus paper. “In certain circles, it is. But a lot of people come from departments that don’t share data because they feel funding is in direct competition. Bates takes a very progressive approach to interdisciplinary research.”

McMahon is now working on his Ph.D. in a program co-sponsored by MIT and the Woods Hole Oceanographic Institution. His contribution to the clamshell research has been to use two gizmos — a New Wave Research UP213 laser ablation system coupled to a Thermo Finnigan Element 2 single collector field inductively coupled plasma mass spectrometer — to measure the chemical components of shell samples. Ambrose et al. used changes in the ratio of strontium to calcium to establish that the external lines of the Greenland cockleshells were, in fact, annual growth lines. “If it wasn’t for Kelton getting us access to those machines,” says Ambrose, “the paper wouldn’t have been anywhere near as good.”

As he sits in his Carnegie office discussing his work — Ambrose also hopes to extend his sclerochronology research to coral in part because “they live much longer than clams” — he is eagerly awaiting a new shipment of Svalbard shells that he hopes will solve a quirk in his findings. Until recent years, Ambrose found that annual clam growth was high in years when the extent of Arctic ice pack, as measured each March, was low. But over the last several years, “growth didn’t track ice cover the way it did before. Something happened, but we’re not sure what,” he says. “Are the last four years unnatural? That’s why I want those new clams. It’s another four years of data that will help establish some baselines.” And baselines will help provide more answers, which will probably just beget more questions. It’s the wayscientific inquiry works. “People like simple answers,” Ambrose says. “Nature doesn’t.”

By Edgar Allen Beem

Freelance writer Edgar Allen Beem wrote about the College’s sustainability initiatives in the Fall 2007 issue of Bates Magazine.

For many thousands of years, two species of large flightless birds shared the same habitats in Australia.

One was the emu, still thriving in Australia today.

The other was a bigger, heavier bird, known to scientists as Genyornis newtoni, that became extinct around 50,000 years ago — around the same time humans arrived on the island continent.

Why did one species disappear while the other survived? The simple answer is diet. Genyornis couldn’t adapt to radical changes in the available food supply, while the emu could, according to a geological study published in the July 8 issue of Science magazine and co-authored by Bates geochemist Beverly Johnson.

But the tale of Genyornis and the emu is the key to a much greater story, one that suggests the human capacity for affecting the environment. Today, much of interior Australia is arid, hosting only sparse, scrubby desert plants. Prior to the arrival of Australia’s first human inhabitants, though, that landscape supported trees, shrubs and nutritious grasses watered by summer rains.

It was that ecological change that doomed Genyornis and it was the human presence that caused the change, say the study’s authors. They theorize that those early inhabitants altered the ecosystem drastically enough, probably through large-scale burning, to cause the extinction not only of Genyornis, but of the continent’s large land mammals as well.

Moreover, the rapid transformation of prevailing flora apparently also affected the climate by reducing “biosphere-atmosphere interactions that promote penetration of monsoon moisture into the interior,” as an abstract of the study states.

This much-publicized research is based on the analysis of fossil eggshells from the two species, including shells collected in core samples and analyzed by Johnson. “You are what you eat, basically,” she explains: Different types of food leave discernible chemical traces in our tissues and, as in this case, in the eggs that birds lay.

Through the analysis of carbon isotopes in the eggshells, “you can determine the proportion of grasses consumed by the birds, relative to trees and shrubs. For an non-discriminating herbivore, such as the emu, the eggshell chemistry reflects the diversity of the ambient vegetation,” Johnson says.

In other words, the eggshell record indicates that “between 140,000 and 50,000 years ago, a wide variety of plants existed to support both the emu and the more picky eater, Genyornis,” she continues. “But shortly after humans arrived in Australia, beginning 50,000 years ago, the vegetation shifted to scrub. Emus could adapt, but Genyornis newtoni and most of the other large browse-dependent animals went extinct.”

So how do humans figure in the story? “Prior to 50,000 years ago, large climate shifts occurred, yet Genyornis was able to adapt to changing conditions,” Johnson says. “The critical part to all this is that the vegetation change and the extinctions occurred simultaneously at three different sites in Central Australia and at a time when climate was relatively stable.

“So there has to be another mechanism for the ecological changes that occurred at approximately 50,000 years ago,” she says. “The timing of these changes is nearly coincidental with human arrival into Australia, and therefore human activity is inferred.”

The researchers surmise that the repeated use of fire by those first human immigrants reduced certain types of vegetation critical to the diets of Genyornis and other plant-browsing fauna. More opportunistic feeders, such as emus, survived.

“We don’t present direct evidence for fire in this paper — it’s very difficult to get, though not impossible,” Johnson explains. “But we do show an ecosystem shift roughly coinciding with the arrival of humans.”

In addition, hunting and the introduction of diseases may have also contributed to the extinction of species, if not the change in plant life.

Led by Professor Gifford Miller, a geologist at the University of Colorado at Boulder, the research team that produced the study also included scientists from the Carnegie Institution in Washington, D.C., the Australian National University and Wollongong University, also in Australia.

Johnson, an assistant professor of geology, has been involved with this ongoing effort since the mid-1990s and, she says, “it’s going to be several more years, probably, before we get to the bottom of it.”

Using the same basic approach, the analysis of stable isotopes in organic matter, Johnson has shifted the current focus of her research to the study of vegetal matter found in sediment cores from northern Australia. She and Bates students also have ongoing paleoenvironmental research projects in northeast Siberia and in Maine salt marshes. Her overarching interest, as well as the techniques involved, is the same for all these studies: using geological evidence to try to understand changes in climate and the environment, especially changes influenced by humankind.

“If humans were capable of completely altering an ecosystem on a continental scale 50,000 years ago using fire, a relatively unsophisticated technology,” she says, “imagine the extent of our impact today.”

At first it may be, as Johnson puts it, “mind-numbing” to consider the human potential for impacting our surroundings. But the real value in this examination of prehistoric events lies in the lessons we can apply today. “If you can understand how the system responds to past human activity,” Johnson says, “you can potentially predict how it will respond to current human activity.”

Bates College has received a state grant of nearly $170,000 for analytical equipment that will significantly advance studies of climate change, the coastal environment and the ecological impact of Maine’s ancient inhabitants.The Maine Technology Institute grant of $168,860 was awarded in October to Assistant Professor of Geology Beverly Johnson, principal investigator for the project. The funds will help equip and staff a laboratory at Bates to assess the composition of stable isotopes of carbon, nitrogen and sulfur in core samples from the soil.The first project planned for the facility will provide important clues about carbon cycling and, notably, climate change in Maine during the last 8,000 years, clues that could help us anticipate the impact from future changes in the weather.

Subsequent projects will investigate other aspects of natural and human history in Maine. “This equipment is a tool for many fields of science — geology, archaeology, ecology, chemistry,” Johnson explains.

Isotopes are atoms of an element differentiated by the number of neutrons they have. Isotopes are designated by the total of neutrons, whose number varies, and protons, whose number doesn’t change. So carbon’s three isotopes, for example, are C-12, which constitutes about 99 percent of carbon in nature; C-13, which makes up the other percentage point; and C-14 (the unstable isotope used in radiocarbon dating), present only in trace amounts. Varying ratios of the stable isotopes in organic material testify to changes in conditions such as weather or plant growth.

As an example, Johnson describes an experiment she will do with introductory geology students next September. Using the new laboratory to measure the composition of carbon and nitrogen isotopes in students’ fingernail clippings, she will distinguish the students who spent the summer in this country eating meat, for example, from those who ate a vegetarian diet in Europe. The point is to illustrate how stable isotopes can be used to construct the diets of animals living in the past.

The stable isotope lab at Bates will measure the ratios of common and uncommon stable isotopes in carbon, nitrogen and sulfur, and will include three pieces of equipment: a gas chromatograph and an elemental analyzer, which in different ways create samples suitable for analysis; and the centerpiece of the system, a stable isotope ratio mass spectrometer (IRMS), which does the actual isotope assessment.

The laboratory will be one of the few such facilities in Maine. Currently, Maine researchers needing stable isotope analysis of bulk organic matter usually look to facilities in other states.

All but one of the researchers who developed the proposal with Johnson teach at Bates. They are Michael Retelle, professor of geology; Bruce Bourque, senior lecturer in anthropology at Bates, and chief archaeologist and curator of ethnology at the Maine State Museum; Curtis Bohlen, assistant professor of environmental studies; William Ambrose, associate professor of biology; and Rachel Austin, assistant professor of chemistry. Also involved is Michele Dionne, a biologist and the research director at the Wells National Estuarine Research Reserve.

Johnson, Bourque, Bohlen and Dionne proposed the specific projects for which the grant was awarded. Bourque will examine Native American middens — essentially, refuse heaps — along Maine’s coast, using evidence of what ancient Mainers ate to better understand how they affected coastal fisheries. Bohlen and Dionne will analyze the human impact on salt marshes in Maine.

The proposal’s lead project, Johnson’s study is connected with research she is conducting in Siberia and Australia. She aims to assess the cycling of carbon from land to marine ecosystems over some 8,000 years, based on samples from Maine coastal sites. Such an assessment can afford important information about a landscape that has seen about 130 meters’ variation in sea level over 10 millennia.

Moreover, Johnson says, the work could help us anticipate environmental impacts from global climate change. Maine’s location makes it a good place to study how land ecosystems respond to changes in the so-called “thermohaline conveyor,” the vast natural system of ocean currents that move warm and cold water from point to point around the globe and therefore play key roles in the climate.

The North Atlantic is a focal point of thermohaline activity, as the Gulf Stream carries warm water to Western Europe, where it is cooled again and sent past North America. Major change in thermohaline activity — such as a cessation of the Gulf Stream — is a potential result of global climate change of concern to scientists.

Past shifts in ocean circulation should be evident in the organic carbon cycle preserved in Maine coastal sediments. Understanding long-term fluctuations in terrestrial carbon cycling is essential, Johnson says, to understanding natural fluctuations of the biosphere, and it provides a baseline for evaluating human impact on global carbon cycling.

The grant was awarded to Bates from the Maine Technology Institute’s Marine Research Fund, funded by a bond issue approved by voters in 2001. It is one of six grants totaling $925,000 announced during the autumn.

Johnson expects the IRMS facility at Bates to be operating by July. The hope is that by 2004, with the facility broken in and funding assured for technical staff, the laboratory will be available to other Maine researchers, including scientists from Bates and Colby and from coastal research centers.