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  Stories from the Sediment

By Catherine Pierre
Photos by Dave Harp

Heaven & earth never agreed better to frame a place for man's habitation; were it fully manured and inhabited by industrious people. Here are mountaines, hil[l]s, plaines, valleyes, rivers, and brookes, all running most pleasantly into a faire Bay, compassed but for the mouth, with fruitfull and delightsome land.
— Captain John Smith,on the Chesapeake Bay, 1606
Opening photo: Grace Brush allows graduate students Brendan DeTemple and Joe Smith to do the heavy lifting — or pushing — as they take a core sample at the Blackwater National Wildlife Refuge. Maryland's Blackwater National Wildlife Refuge, a 26,000-acre wetlands just south of Cambridge, offers the quintessential Chesapeake Bay scene, with shallow waters, high marsh grasses, and scattered groves of loblolly pine. At the edge of the refuge, a modest information kiosk lists facts about the area's muskrat, nutria, and American bald eagle populations. A short nature drive allows visitors glimpses of wood ducks, snow geese, great blue heron, and, if they're lucky, the threatened eagle. To the untrained eye, the refuge looks pristine.

Paleoecologist Grace Brush knows better. A professor in the Whiting School of Engineering's Department of Geography and Environmental Engineering (DoGEE), she brings her students to Blackwater to "see ecology first hand." As an expert on the Chesapeake Bay and its watershed, she knows that below the water's surface are signs of devastation. The vast meadows of underwater grasses are gone, as are many of the bottom-dwelling species that made their homes there. The crab and oyster populations, so central to the Eastern Shore's character and, once, its economy, are some of the lowest in history. Centuries of human, or anthropogenic, influence — deforestation, agriculture, and urbanization — have polluted the water and starved it of oxygen. The estuary is suffocating.

At 73, Brush has devoted 25 years of research to uncovering the bay's past. By scrutinizing core samples of sediment taken from areas throughout the estuary, she has been able to show what was on the land and in the water decades, centuries, millennia ago. More important, by reading the history written in the sediment, she has been able to show that the recent changes wrought by human land use are not cyclical or temporary, but unprecedented in 14,000 years. "It turns out," says Brush, "that the anthropogenic is probably one of the most extensive and intensive global disturbances that there has been."

For decades, bay managers have sought to understand how to undo some of that damage. But to do so, they need to know what the bay was like before Europeans arrived. Brush's research has been invaluable to that task.

"[Brush] is one of the researchers on the bay who is always at the cutting edge of research on practical issues," says William C. Baker, president of the Chesapeake Bay Foundation (CBF), a non-profit conservation organization dedicated to saving the bay.

Adds Kim Coble, CBF Maryland executive director and senior scientist, "Her work has given us more insight into the impacts of our current actions than almost any other research. It is her work that has allowed us to go well beyond the obvious as we try to understand the problems in the bay and seek out solutions."

This spring, Grace Brush is receiving the Mathias Medal, an honor given by Maryland Sea Grant, Virginia Sea Grant, and the Chesapeake Research Consortium. The medal recognizes scientists whose lifetime contributions have not only furthered the public's understanding of the bay but have informed policy surrounding its management.

"Policymakers have used her work as the basis of saying what the bay was in the past and what the bay is going to be in the future," says Jonathan Kramer, director of Maryland Sea Grant. "It's really very pivotal stuff."

The award, Kramer explains, has been given to the "scientific giants" of Chesapeake Bay research. "If you look back to her career," he adds, "as a woman in science, she's done many things that are examples for women. She rose through some fair adversity to become really a giant, in this region certainly."

Brush understands the history of the Chesapeake through the pollen preserved in its sediment. Microscopic examination allows her to discern ragweed (top) from oak (bottom).
Photo courtesy Grace Brush
Grace Brush is a giant who stands 5-foot-3. She's soft-spoken and rather understated, with none of that authoritative bluster that often comes with being a top researcher in one's field. Though she is well-respected for her science, her pleasant nature and genuine regard for the people she works with seem to have created something of a fan club.

"The most distinctive thing about Grace is what a wonderful way she couples a fabulous personality and warm sense of engagement with superlative science," says David R. Foster, director of Harvard University's Harvard Forest, where Brush spent a sabbatical year from 1995 to 1996. "There are few scientists who have the humility and the warmth of personality and engagement Grace does. I can't imagine being a colleague of hers and not feeling that you were a friend of hers."

Brush's career as a superlative scientist has somewhat humble roots. She was turned on to paleontology as an undergraduate at St. Francis Xavier University, when her geology professor took the class on a field trip to look at now-extinct tree ferns preserved in 200-million-year-old rocks. "There were these incredible fossils," Brush says. "And they were just beautifully preserved."

When she was 18, she landed a job as a lab technician for the Geological Survey of Canada — her first job out of college — near her home in Nova Scotia. (She still lists the position on her CV.) It was 1949, and the lab was studying mineral content in coal samples to determine which underwater coal beds were potentially the most productive. It was Brush's job to cut thin slices of coal for study. When she saw tiny fossilized spores in the coal, she asked if she could study them. She discovered that coal beds deposited in specific geological time periods were characterized by different assemblages of spores. By identifying these spores, it was possible to determine which coal beds would be worth mining.

Based on this work, the Geological Survey decided to open a paleobotany lab and picked Brush, then 19, to be the one to set it up. She first needed to be trained, so she enrolled in the University of Illinois' prestigious coal research graduate program, on a teaching assistantship. (The Canadian government had been ready to underwrite Brush's studies, but her father didn't want his daughter to be beholden to the government.) After earning a master's degree in botany, she returned to Nova Scotia for a year to fulfill her commitment to set up the paleobotany lab. Then she received a research assistantship in Penn State University's renowned coal research program.

"I wouldn't have had it differently," says Brush about juggling motherhood and scientific research. "But it wasn't easy." That's when life stepped in.

At Penn State, she met Lucien Brush, a bright and fun-loving Princeton grad who was there doing graduate work in paleontology. A year later, the two were married. What followed were three sons — Lucien Jr., George, and John — and several years of career stops and starts. Grace and Lucien had agreed that he would take the best job he could find and that she would follow, finding part-time research opportunities wherever they went. Their route took them to Harvard, to U.S. Geological Survey positions in Washington, D.C., and Colorado, to the University of Iowa, Princeton, and finally, to Johns Hopkins. (Lucien, a professor of hydraulics and hydrology at Hopkins, died from lung cancer in 1994.)

There were highlights for Grace: At Harvard, for instance, where she earned a PhD in biology, she was able to work with Elso Barghoorn, the paleontologist credited with discovering the world's oldest fossilized organisms. He had heard her deliver a paper on the coal work she had done in Canada and was eager to welcome her as a student. "When I left there," remembers Brush, Barghoorn "knew my situation, that I was married and I was going to go wherever my husband was. He said — and I thought at the time, well, it's easy for you to say that — he said, 'Don't work just for someone as a technician. Do your own work, your own research.'"

She was able to do just that at Iowa, having obtained a half-time position as an assistant professor of botany. "I taught a course, got a research grant, and in a sense, that was really ideal," she says. As part of their agreement, Lucien would take care of the boys if she had fieldwork. "I don't know what went on at those times," Brush says with a laugh, "but at least he took over."

But there were also frustrations. At Princeton, though she was given lab space, she didn't come across any other female faculty members, students, or staff members. "I thought, This is very strange because this is one of the big universities in the country, one of the top universities, and women are excluded from it," says Brush.

Grace Brush in the lab at Harvard University, where she earned her PhD in biology in 1956.
Photo courtesy Grace Brush
She always had to be looking for the next funding opportunity, and throughout her early career as an untenured researcher, she says, it was hard to be taken seriously. It wasn't until she came to Hopkins in 1970 as a research scientist that she began to think about pursuing her work full time.

"I wouldn't have had it differently," she says of her double-shift life of mother and scientist. "But it wasn't easy."

It may not have been easy, but it may account for the fan club. Brush, who has a habit of recounting her research according to the graduate student working with her at the time ("We began looking at the diatoms — Sherri Cooper began doing that work"), understands her students as people with full lives of their own. And she embraces them as friends as much as colleagues. She's in touch with students she taught 20 and 30 years ago. She goes to their weddings. She knows their children.

"Grace and I have been close for many, many years. My oldest daughter is named Grace," says Cecilia Lenk '76, who worked with Brush as an undergraduate. "She's so good at listening and she's so good at understanding people. We were able to talk about a lot of issues" such as going to graduate school. "She was so involved in my decision making and my thinking about what I wanted to do in the future."

Says Harvard's David Foster, "She's lived life as a person, not purely a scientist. The thing that's so impressive to me is that being a woman and facing all the challenges women have faced making it in the sciences, especially in the physical sciences where she has succeeded — she did that while simultaneously living a full life, with a family and a husband and diverse interests. That's extraordinary."

Things got easier for Brush when she became a tenured professor in 1990. But she recognizes that juggling family, life, and work is still difficult.

"I don't think she would ever come out and say she's a role model for women, but she is — just in terms of her doggedness, and just sticking to it no matter what happens," says Ruth DeFries '80 (PhD), now an associate professor at the University of Maryland. "She came to my wedding and she stood up and gave a toast and said, 'I want you to know that you're not just marrying this woman, you're marrying a career.'"

"It isn't just the 20th century," says Frank Davis. "We've been affecting the estuary for many centuries." The Mathias Medal is named after Charles McC. Mathias, the former U.S. senator (D-Md.) who in 1973, troubled by the Chesapeake Bay's decline, set out to find the cause. The project, with $27 million in funding from the Environmental Protection Agency, would eventually become the Chesapeake Bay Program.

By the early '70s, it was clear that the bay was in trouble, suffering what Brush has called a "near crash of the system." A major indicator of that crash was the disappearance — in fact, the extinction in some areas — of underwater grasses known as submerged macrophytes. Scientists and policymakers began asking the same kinds of questions about the disappearance of the grasses as they do today about global warming: Is this the result of human activity, or simply part of a natural cycle? And if humans are to blame, what specifically are we doing wrong?

Brush had been attending the Chesapeake Bay Program meetings and, in 1978, made a proposal to study the submerged macrophytes using a technique she had employed previously in the bay. In that earlier study, she used core samples taken from Baltimore's Back River to show that when a sewage treatment plant went on line by the river, the underwater grasses died off.

"When the Chesapeake Bay Program began," says Brush, "they were asking these very large questions. That's when I thought, We can probably answer some of those questions."

The basis for Brush's bay research is the mud found at the bottom of the bay and at its edges. As silt and clay particles settle, they bury and preserve chemicals and organisms, creating a record of the climate, the plant and animal life, and the water quality at the time they were deposited. By analyzing core samples of the sediment, Brush can reconstruct that history. As a settling basin, Chesapeake Bay proved perfect for this kind of work — Brush would eventually find undisturbed cores that date back 14,000 years.

"Things that were happening on the land were being recorded very, very accurately," says Brush. "I didn't expect to find it as precisely recorded."

To collect cores, Brush uses a clear plastic tube fixed with a piston at the bottom and attached to a longer metal pole. The pole works as a handle to force the tube into the sediment; as the tube is submerged, the piston is pushed up inside the tube, creating a vacuum. When the tube is removed from the sediment, it brings with it a perfect cylinder of clay and detritus.

Brush then dates the cores using a combination of carbon-14 analysis and what she calls "pollen horizons." For example, since ragweed flourishes in recently tilled land, a jump in ragweed pollen in the sediment indicates European settlement, when the land was cleared for farming. A sudden disappearance of chestnut pollen indicates the 1920s and early '30s, when disease wiped out these trees in the region. Using these pollen horizons, Brush then can assign dates to smaller increments within the core sample. By looking at what lived and died along that timeline, she is able to compare pre- and post-European conditions.

Since the time of European settlement, major deforestation on the land has caused increased sedimentation in the water, explains Brush. That extra silt muddies the bay, preventing light from reaching the bottom and killing off the plants and animals that live there. The fertilizers used in farming (first guano and later chemicals), plus the treated sewage that comes with a growing population, have increased the amount of nutrients, especially nitrogen and phosphorous, flowing into the bay. Those nutrients cause algae blooms, which increase turbidity and, when the algae die and decay, deplete oxygen in the water, a condition called anoxia.

Brush, here with grad student Mason Thronburg, works at the edge of the Gwynns Falls, where it flows into Baltimore's Inner Harbor. When Brush examines a core, she can see when species appear and when they die out. By studying diatoms, which are tiny algae whose skeletons are well-preserved in sediment, she can see when the bottom-dwelling, or benthic, species were replaced by those that live in the upper part of the water, or planktonic species — an indication of extensive anoxia. And she has found that, though there were cycles of rise and decline before Europeans settled here, there has never been the kind of sustained loss of species that the bay has experienced since then.

"What she showed," says Frank W. Davis '82 (PhD), who as a graduate student worked on Brush's submerged macrophyte study, "was this strong coupling between what we're doing on the land and what's happening in the estuary. And that it isn't just the 20th century — we've been affecting the estuary for many centuries."

The loss of the grasses, Brush was able to show, was not natural; it was manmade. Says Davis, now a professor at the University of California, Santa Barbara, "We were able to look back through the sediment record and see that over 500 or 600 years, that disappearance of some species from the upper Chesapeake Bay was unprecedented."

Hurricane Agnes devastated the region in 1972. "There was a lot of controversy," says Brush. "People were arguing about what causes anoxia — is it the amount of sediment and nutrients coming into the bay, or is it the amount of rainfall? And it was pretty clear with this record that, sure the rainfall is going to affect things, but we had varying rainfalls before [European] settlement, and we didn't have this very extensive anoxic condition."

Though industrial plants were suspect, Brush showed that widespread deforestation and agriculture were as much, if not more, to blame. "Out of that first work," says Brush, "we were able to show the effect of agriculture — the very high sedimentation rates — and the effect of those sedimentation rates on the submerged grasses."

Says CBF's Will Baker, "It really put an end to all the talk at the time that this was nothing to worry about, just a natural cycle."

Brush and DeTemple make their way through the marsh. Over the past decades, Brush has collected hundreds of cores, answering specific questions that together tell an ever more complete story of the bay. She is co-editor, with the Krieger School of Arts and Sciences' Philip D. Curtin and George W. Fisher, of Discovering the Chesapeake: The History of an Ecosystem. And she has authored dozens of studies — often with her students — about the Chesapeake Bay that have appeared in journals including Science, Estuaries, and Environmental Reviews.

For instance, Sherri Cooper and Brush used diatoms to prove that agriculture increases anoxia. Bill Hilgartner, Humaira Khan, and Brush were able to determine when fresh water marshes originated and to show how vital they are in protecting the bay from nutrient loading. Another student, Angie Arnold, worked with Brush to determine that a certain species of worms, which were bottom-feeders, were once as abundant in the bay as filter-feeders like oysters, prompting new questions about what restoration should mean in the bay. And Emily Elliott is working with Brush on a study that uses isotopes to identify specific sources of nitrogen.

"Unfortunately we don't seem to be looking for anything good happening," says Brush. "We would be so utterly surprised if we found a core with benthic diatoms in the top sediments! That would be a sign that we've got clear water!"

That seems a long way off. Though there is some dispute about the progress the Chesapeake has made over the past 30 years, no one would claim that the bay is healthy. (In its most recent "State of the Bay" report, the Chesapeake Bay Foundation gave the bay 27 points out of 100 — 100 being the bay Captain John Smith found in the early 17th century.) Brush, like so many bay scientists, would like to see the bay restored to its former abundance. Though she doesn't actively participate in the policy and the politics surrounding the bay, she has made a life's work of providing vital information to the people who do. Says Brush, "I think the way we are most effective is by getting really indisputable evidence to the people whose job it is to argue for the right management and policy."

Her work is paying off, as evidenced by the Mathias Medal, as well as her considerable reputation among the Chesapeake Bay community.

"Dr. Brush and [the bay scientific community] give us the credibility as a society to determine what policies are needed to improve the environment," says Baker. "That's the importance. The scientists have really analyzed and determined what the problem is and how to fix it — and that's no small feat."

Brush says she is motivated by the possibility of making the bay's "very dramatic history" more and more complete. Though the Chesapeake itself seems to give her a certain inspiration.

"Every time I drive across the Chesapeake Bay Bridge, I just think how beautiful the bay is," says Brush. "Its beauty has remained, despite everything that's gone."

Catherine Pierre is associate editor of Johns Hopkins Magazine.

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