{"id":454,"date":"2010-04-21T16:02:50","date_gmt":"2010-04-21T16:02:50","guid":{"rendered":"http:\/\/hub-dev.bates.edu\/magazine\/?page_id=454"},"modified":"2017-09-06T11:38:40","modified_gmt":"2017-09-06T15:38:40","slug":"of-climate-clams-and-colleagues","status":"publish","type":"page","link":"https:\/\/www.bates.edu\/magazine\/back-issues\/y2008\/spring08\/features\/of-climate-clams-and-colleagues\/","title":{"rendered":"Of Climate, Clams, and Colleagues"},"content":{"rendered":"

Professor Will Ambrose, a bearded biologist specializing in Arctic sea-floor ecology, is a pioneer in the science of deciphering the past \u2014 including past climates \u2014 by studying the annual hard-tissue accretions of organisms such as mollusks.<\/p>\n

As an expert in sclerochronology, Ambrose has discovered a link between Arctic clam growth and regular shifts in the region\u2019s 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 \u201csentinel of climate change.\u201d<\/p>\n

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\nIn Kongsfjorden on the west side of Svalbard, Will Ambrose (facing) and Kelton McMahon \u201905 haul a dredge to collect Serripes groenlandicus<\/em> and other clam species for McMahon\u2019s thesis in 2004. Photograph by Glenn Lopez, SUNY\u2013Stony Brook.<\/strong><\/p>\n

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.<\/p>\n\n\n\n\n
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Seen here is the cross section of a small portion of aSerripes groenlandicus<\/em> shell, near the umbo, or hinge.\u00a0The lines indicate annual growth: dark lines\u00a0for slow winter growth; light areas indicate fast summer growth. For an image showing the complete shell, click here.<\/a><\/strong><\/span><\/p>\n

Will Ambrose has discovered\u00a0a correlation between growth and climate shifts. This image is a composite of 18 images produced by the College\u2019s new Imaging and Computing Center using a Nikon SMZ 1500 stereo microscope. Collected in 1926, the shell\u2019s actual length is 2.5 inches. <\/strong><\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

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).<\/p>\n

After encasing the shells in epoxy and slicing them apart, Ambrose and a team of scientists, including Kelton McMahon \u201905, 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.<\/p>\n

\u201cWhat makes the work exciting,\u201d says Ambrose, interviewed in his cluttered office on Carnegie\u2019s third floor, \u201cis that this is the first time in the Arctic that we\u2019ve been able to track a large-scale climatic oscillation and see that large-scale regional event reflected in animals living on the bottom.\u201d<\/p>\n

While scientists have for decades analyzed growth lines in shells (Ambrose and others call them \u201ctrees of the sea\u201d) in order to reconstruct past environments, the intensity around climate-change research has \u201creally made the field of sclerochronology take off,\u201d he says.<\/p>\n

In this hot field, Ambrose\u2019s research is distinctive for its location, on the Arctic continental shelf. \u201cA lot of the work has been done at lower latitudes, mostly because it\u2019s harder to get clams in the Arctic and there are simply fewer people available to help,\u201d he says. \u201cThat\u2019s why we\u2019re ahead of the ball.\u201d<\/p>\n

If it\u2019s true that Arctic clams grow faster in warmer weather (and grow faster when there\u2019s less of a seasonal ice pack, another signal that Ambrose saw hints of), a simplistic response might be, \u201cGreat \u2014 fatter clams for walruses to munch on.\u201d But, explains Ambrose, fat clams won\u2019t 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.<\/p>\n

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\nThese Serripes groenlandicus<\/em> clams were collected in Storfjord at a site last visited by 19th-century Russian explorers. Photograph by Greg Henkes ’08.<\/strong><\/p>\n

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. \u201cEcosystems operate at the interface of physics, chemistry, and biology, with both complementary and contradictory interactions,\u201d Ambrose writes in a forthcoming article predicting that \u201cregional, and perhaps global, biodiversity will suffer.\u201d<\/p>\n

Until recently, Ambrose researched other organisms of the benthic community, such as bloodworms along Maine\u2019s 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. \u201cVery expensive,\u201d Ambrose says.<\/p>\n

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.<\/p>\n

Geology professor Beverly Johnson, for example, has been invaluable in co-advising biology students so they can learn to use the College\u2019s 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.<\/p>\n

\u201cI work with Will to understand how modern systems work,\u201d says Johnson, \u201cand then go back to old shells, using the geochemistry of shells from 125,000 years ago to reconstruct the environment.\u201d<\/p>\n

Ambrose also depends on Matt Duvall, who directs Bates\u2019 new Imaging Center, to create elegant microscopic images of his clamshell sections that Ambrose calls \u201cjust incredible.\u201d<\/p>\n

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.<\/p>\n

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 \u00c1slaug \u00c1sgeirsd\u00f3ttir. What started informal \u2014 an interdisciplinary coffee klatsch \u2014 has given rise to \u201cNorth Atlantic Studies,\u201d a thematic grouping of Bates courses, known as a concentration, under the College\u2019s new general education requirements. \u201cWe represent an area of study, rather than just a bunch of us sitting around having coffee,\u201d Ambrose says.<\/p>\n

\u201cIt\u2019s a truly special group,\u201d Retelle adds. \u201cThe 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.\u201d<\/p>\n

Ambrose himself is quick to point out that \u201cstudents here are the ones driving the bus in terms of getting the work done.\u201d As he speaks, Greg Henkes \u201908 of Chapel Hill, N.C., is downstairs in the environmental geochemistry lab cutting shells and extracting organic material. Henkes\u2019 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.<\/p>\n

\"\"
\nGreg Henkes \u201908, one of Will Ambrose\u2019s thesis students, took this photograph\u00a0at\u00a03 a.m. on June 3, 2007, as the research shipLance <\/em>heads through sea ice in Storfjord in the Svalbard archipelago, about halfway between the North Pole and Norway.<\/strong><\/p>\n

\u201cIt\u2019s pretty incredible to be able to do this at Bates,\u201d says Henkes. \u201cIt\u2019s the way science is going,\u201d 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. \u201cPeople aren\u2019t doing their own little thing anymore.\u201d<\/p>\n

\u201cThat\u2019s the way science should be done,\u201d emphasizes Kelton McMahon, co-author of the Serripes groenlandicus paper. \u201cIn certain circles, it is. But a lot of people come from departments that don\u2019t share data because they feel funding is in direct competition. Bates takes a very progressive approach to interdisciplinary research.\u201d<\/p>\n

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 \u2014 a New Wave Research UP213 laser ablation system coupled to a Thermo Finnigan Element 2 single collector field inductively coupled plasma mass spectrometer \u2014 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. \u201cIf it wasn\u2019t for Kelton getting us access to those machines,\u201d says Ambrose, \u201cthe paper wouldn\u2019t have been anywhere near as good.\u201d<\/p>\n

As he sits in his Carnegie office discussing his work \u2014 Ambrose also hopes to extend his sclerochronology research to coral in part because \u201cthey live much longer than clams\u201d \u2014 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, \u201cgrowth didn\u2019t track ice cover the way it did before. Something happened, but we\u2019re not sure what,\u201d he says. \u201cAre the last four years unnatural? That\u2019s why I want those new clams. It\u2019s another four years of data that will help establish some baselines.\u201d And baselines will help provide more answers, which will probably just beget more questions. It\u2019s the way scientific inquiry works. \u201cPeople like simple answers,\u201d Ambrose says. \u201cNature doesn\u2019t.\u201d<\/p>\n

Freelance writer Edgar Allen Beem wrote about the College\u2019s sustainability initiatives in the Fall 2007 issue of<\/em> Bates Magazine.<\/p>\n","protected":false},"excerpt":{"rendered":"

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