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Human Influence on Diatom Productivity and Sedimentation in Chesapeake Bay
A paper entitled "Anthropogenically Induced Changes in Sediment and Biogenic Silica Fluxes in Chesapeake Bay," written by Steve Colman and John Bratton, has been published in the journal Geology (January 2003). The paper, which addresses fundamental science questions related to reconstructing past environmental conditions, has many applied-science, ecosystem-management implications. It provides continuous, well-dated records of total-sediment and biogenic-silica fluxes from well before the arrival of Europeans to the present. Previous attempts to address these questions have been hampered by poor dating, short records that do not extend to presettlement times, or measurements that allow only concentration, rather than flux, calculations. Owing to these problems, many studies of ecosystems and the geologic and biogeochemical processes that affect them fail to place their conclusions within a long-term context. The state of the system and its natural variability before its disturbance by human activity are critical for truly understanding the effects of humans on ecosystems. Here is the paper's abstract: "Sediment cores as long as 20 m, dated by 14C, 210Pb, and 137Cs methods and pollen stratigraphy, provide a history of diatom productivity and sediment accumulation rates in Chesapeake Bay. We calculated the flux of biogenic silica and total sediment for the past 1,500 years for two high-sedimentation-rate sites in the mesohaline section of the bay. The data show that biogenic silica flux to sediments, an index of diatom productivity in the bay, as well as its variability, was relatively low before European settlement of the Chesapeake Bay watershed. In the succeeding 300-400 years, the flux of biogenic silica has increased by a factor of 4 to 5. Biogenic silica fluxes still appear to be increasing, despite recent nutrient-reduction efforts. The increase in diatom-produced biogenic silica has been partly masked (in concentration terms) by a similar increase in total-sediment flux. This history suggests the magnitude of anthropogenic disturbance of the estuary and indicates that significant changes had occurred long before the 20th century."
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in this issue: Congressional Briefing on Gas Hydrates Volcanic Ash and Aviation Safety International Deep-Sea Corals Workshop Northeastern Coastal Ecosystems and Resources Workshop
Coastal and Marine Scientists Win 2002 Shoemaker Product Excellence Awards Behrendt and Poag Elected AAAS Fellows Marine Geophysics Pioneer Honored Celebrating Careers of Five Retirees Manheim Lectures on Trends in Scientific and Technological Innovation
Effectivenes of Marine Reserves in Central California Human Influence on Diatom Productivity and Sedimentation in Chesapeake Bay |
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U. S. Department of the Interior | U.S. Geological Survey
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