Grant will advance research into climate change, ancient Mainers

Bev Johnson

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.

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