level of sulfur in a sediment layer, she 

 knows that the estuary suffered from a lack 

 of oxygen at that time. 



I know it's a complicated lesson in 

 geochemistry, but I hope the point is clear: 

 Once again, nature remembers. In this case, 

 sulfur levels help to map the level of oxygen 

 available to estuarine life across the ages. 



Daniel Jones pushes out a sediment core 

 on the lab bench at the Duke Wetland Center. 

 The core, collected from the Neuse River estuary, will be 

 divided into 2-centimeter sections and analyzed. 



Cooper's study of fossilized diatoms is 

 another intriguing way to explore the history 

 of water quality. Diatoms are a distinctive 

 kind of microscopic algae and one of the 

 most common types of phytoplankton in our 

 estuaries. Diatoms and other phytoplankton 

 form the critical first rung in the estuarine 

 food chain. They are the basis of all our 

 commercial and recreational fisheries. Lose 

 the phytoplankton, and you lose the fried 

 shrimp and stuffed flounder. 



Diatoms are useful in paleoecological 

 research because they have a silica shell, 

 known as a frustule. The frustule has two 

 overlapping parts, like a pillbox and its lid. 

 Because it is almost pure silica, the frustule 

 is preserved in the estuary sediments after 

 the diatom dies. And because each species 

 of diatom has a unique frustule, they can be 

 identified under a microscope. 



Diatom species are numerous — 

 Cooper counted more than 240 in her North 

 Carolina sediment cores. And she expects 

 to find more based on her research in the 

 Chesapeake Bay, where she's counted more 

 than 400. Some thrive better in salt water, 

 others in brackish water, others fresh water. 

 In fact, the species of diatoms in an estuary 

 sample differ 

 depending on a 

 whole range of 

 environmental 

 conditions: not just 

 salinity, but also 

 light, pH, nutrient 

 levels, substrate, 

 temperature and 

 pollution. 



Thus Cooper 

 can identify the 

 diatoms in a 

 sediment sample 

 and tell a great 

 deal about what 

 kind of water 

 conditions they 

 lived in. It's like 

 seeing an alligator, 

 a cottonmouth 

 snake and a bald 

 cypress: You don't 

 need to get your 

 feet wet to know you're in a swamp. In this 

 case, the presence or absence of certain 

 species of diatoms helps Cooper recognize 

 the historic levels of eutrophication, salinity 

 and turbidity. 



Cooper has only begun to reconstruct 

 the history of water quality in the Neuse and 

 Pamlico, but some interesting findings 

 already stand out. Perhaps most importantly, 

 her core samples show relatively few 

 changes in water quality until the 20th 

 century. (Her preliminary results, however, 

 seem to indicate an intriguing rise in 

 ragweed pollen counts in the 14th century. 

 I can't wait to see how Cooper will explain 

 it. A sudden rise in Algonkian settlement? 

 A massive fire?) 



Truly dramatic changes in water quality 

 show up after World War II. Since 1950, 

 sedimentation rates, nutrient levels and trace 



metal flux have increased significantly, 

 sometimes by an order of magnitude. 



All of Cooper's sediment samples 

 show a striking decline in the number of 

 diatom species over the last five decades. 

 Diatom diversity has declined by nearly 50 

 percent in the Pamlico estuary. There have 

 also been telling changes in the kinds of 

 diatoms buried in the estuary sediments 

 since 1950. These changes chronicle growth 

 in eutrophication, turbidity, sedimentation, 

 freshwater flow and industrial pollution. 



Sunghea Kim, one of Cooper's 

 students, conducted another paleoecological 

 study of estuarine sediments as part of a 

 master's project. The study indicates that 

 trace metals in surface waters of the Neuse 

 and Pamlico have risen dramatically over 

 the last 50 years. Examples of trace metals 

 include cadmium, nickel, chromium and 

 arsenic. Many have reached quantities that 

 exceed the U.S. Environmental Protection 

 Agency's "threshold effect levels," that is, 

 the point at which the trace metals affect the 

 estuarine ecology. 



Cooper hopes to follow other paleoeco- 

 logical clues in the future. Fossilized 

 foraminifera, sort of microscopic conch 

 shells, are good indicators of salinity levels. 

 Charcoal tells of fire history. Seeds help 

 chronicle changes in submerged aquatic 

 vegetation. Algal pigments, also preserved 

 in estuarine sediments, reveal variations in 

 phytoplankton communities as a whole. 

 All of these natural clues hold tremendous 

 potential for understanding more about the 

 history of water quality in the Neuse and 

 Pamlico. 



Paleoecology also holds a more general 

 lesson. I've long taken for granted that each 

 of us makes a lasting impression on the 

 people whose lives we touch. A simple 

 kindness, a loving gesture, a cruel remark, an 

 unthinking slight — they all leave indelible 

 marks on a human soul. Now, because of 

 Cooper's work, I realize that we also make a 

 lasting impression on every place we touch. 



After all, nature remembers. □ 



David Cecelski is a historian at the 

 University of North Carolina at Chapel 

 Hill's Southern Oral History Program, 



COASTWATCH 27 



