Recent Diatom and Trace Metal Distributions in the Patuxent and Nanticoke Rivers

摘要

Paleoecological data from recent sediments of the Patuxent and Nanticoke Rivers, accompanied by historical data on land use and water quality, indicate that the response of diatom populations to sediment, metal, nutrient, and thermal loading is related to characteristics of the habitat as well as to the nature and history of loading. Species composition has changed with siltation since the 17th and 19th centuries and the application of chemical fertilizers to the watersheds since the 19th century. Nutrient loading from sewage discharge results in a dramatic shift to planktonic species, and in particular species such as Cyclotella meneghiniana that prefer water high in nutrients, such as sewage effluent. Metal profiles show an increase in the flux of metals into the estuary with land clearance during the historic period and a comparable increase with fire during prehistoric time. There is no evidence in either estuary of any effect on diatom populations from thermal loading, either in species abundance or composition, and no clear evidence of an effect specifically attributable to increase in metals.