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<\/a>Stephen Durham (left) and his father, Michael Durham, gather shells from Fence Creek in Madison, Connecticut. Photo by Geoff Giller<\/p><\/div>\n
The creek must be empty before Durham can dig down into the carbon-rich, sulfur-smelling mud and collect his samples. But at the minute of dead low tide, water still streams around his ankles. Unfazed, Durham carries on with his other task: plucking living oysters from the creek bed surface for comparison purposes. He\u2019s got plenty of antique mussels waiting back at his lab, a five-hour drive away.<\/p>\n
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Durham, along with his PhD adviser Gregory Dietl, has excavated thousands of eastern oyster shells from sites in Louisiana, the Carolinas, and Connecticut over the past several years. At his office at the Cornell University-affiliated Paleontological Research Institution in Ithaca, New York, they\u2019re piled on shelves and in drawers, some still covered in marsh muck and wrapped in plastic collection bags, others cleaned, sorted, neatly labeled, and boxed. The smallest shells are just a few millimeters long; the biggest are longer than an iPhone. The shells vary in age; some are relatively young at a few decades to centuries old, like those from the creek in Connecticut, while his oldest shells date back hundreds of thousands of years to the Pleistocene. Those older shells aren\u2019t even from modern marshes: Durham and Dietl find them exposed along the walls of canals, in places where marshes once existed farther inland when ocean levels were higher. They often find these old shells intact, with both halves upright like they would have been when the oysters were alive, before marsh silt buried them millennia ago.<\/p>\n
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<\/a>One of the first steps in Durham\u2019s lab process is to spread samples onto wire mesh for cleaning. Photo by Geoff Giller<\/p><\/div>\n
In the lab down the hall from his office, a few days after he\u2019s returned from Connecticut, Durham hoses off 350,000-year-old samples from a site in South Carolina, the shells arrayed on wire mesh over a sink. After he has cleaned each bagged sample, he combs through the collection and matches single oyster shells into pairs, like an ancient jigsaw puzzle. \u201cTa-da,\u201d he says, holding up a set. With both halves, he can be sure that he\u2019s measuring an oyster\u2019s full size and that it lived near the collection site and wasn\u2019t just washed there by waves or tidal currents.<\/p>\n
From there, Durham sets about turning old calcium carbonate into hard data. He selects a few shells for analysis, saws them in half, and then zaps the cut surfaces with a laser to measure the ratios of elements such as magnesium, calcium, and barium. The ratio of magnesium to calcium changes with temperature, so he can deduce the lifespan of an oyster by seeing how many hot and cold seasons it lived through. And barium and calcium ratios in the shell material vary slightly with local salinity, indicating how salty the water was at the time the oyster lived.<\/p>\n
There\u2019s even information in the detritus that he washes off the shells. As he brushes aside shell bits piled on the wire mesh, they jingle like broken glass. He picks out an impossibly small snail shell, not much larger than a hangnail. \u201cBoonea impressa<\/em>,\u201d he declares: an oyster parasite. Its presence, and the presence of other non-oyster shells in the sample\u2014all from species still alive today\u2014reveals more about the environment the oysters came from. For example, Boonea<\/em> lives in a narrower range of salinities than the eastern oyster, so the ancient sample provides further evidence for how salty the water was all those years ago at the spot in South Carolina where this particular batch of shells is from.<\/p>\n Other species found among the old oyster shells, such as this Boonea impressa<\/em>, provide more details about the past: for example, the water salinity at the time the oysters lived. Photo by Geoff Giller<\/p><\/div>\n Conservation paleobiology can provide a remarkably complete picture of how oysters or other organisms lived well before humans arrived on the scene. \u201cWe can tell managers what oyster populations looked like in the past,\u201d says Durham. The question now is: \u201cWhat are the things they want to know?\u201d<\/p>\n Hot on the heels of that question comes the quandary of how to get the information into circulation. The field of conservation paleobiology was first named in 2002, though scientists have been employing its techniques for several decades; in 2009, Dietl helped organize presentations about it at a meeting of the Geological Society of America. The emerging field now boasts members across the Americas, Europe, and Australia. And the scope of work extends beyond oysters: conservation paleobiologists have used pollen and traces of seeds to determine whether some Galapagos plants were originally native or invasive, for example, and they have studied fossil corals to show shifts in distribution in response to large-scale climate changes. Yet many restoration managers are still unaware of the field\u2014or remain skeptical.<\/p>\n Many are \u201cintrigued, but slightly suspicious,\u201d about paleobiological data, says Rowan Lockwood, a geology professor and conservation paleobiologist at the College of William and Mary in Virginia. \u201cThis is a new source of data for them, and I don\u2019t think they\u2019re completely convinced.\u201d That sentiment was echoed in the results of a survey<\/a> completed by about 100 people working on oyster restoration in the United States and published by Durham and Dietl last year.<\/p>\n At his lab, Stephen Durham uses a diamond saw to slice through an oyster shell. Photo by Geoff Giller<\/p><\/div>\n Some think that the secrets of ancient shells have limited value for planning restoration efforts today. \u201cThere have been a heck of a lot of changes in oyster reefs in the last 200 years,\u201d says Philine zu Ermgassen, who studies marine ecosystem services at the University of Cambridge. \u201cTo ignore that fact would be exceedingly naive.\u201d It\u2019s more important, she says, to understand the current conditions.<\/p>\n Durham and Dietl argue that restoration scientists should simply factor paleobiological data into their equations\u2014along with current conditions. One of the strengths of their information is that it can help avoid the pitfall of \u201cshifting baselines.\u201d That\u2019s the idea that the world during our lifetime, or in the very recent past, is our model\u2014or baseline\u2014for how the world ought to look, even if that world is, or was, already severely degraded.<\/p>\n \u201cIf you\u2019re setting goals based on something that\u2019s already completely degraded, you may be undershooting a lot,\u201d Dietl says. Neither he nor even the most optimistic oyster restorers expect the coastline to ever look the way it did before industrial harvesting and coastal development decimated populations. Still, this type of historical data can help ensure that restoration goals are appropriately ambitious and well-suited to the environmental conditions. \u201cMaybe you could restore it to be better, but you have no idea because your measure of success is looking at a reef that\u2019s been degraded for a century.\u201d<\/p>\n![](\"\/wp-content\/uploads\/snail-shell-paleo-oyster.jpg\")
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