Abstract
Diatoms were extracted from subsampled sections of four dated sediment cores collected in the mesohaline Chesapeake Bay, U.S.A. Over 400 species in 76 genera were identified. A complete list of the species identified from the cores is given, together with information on their relative abundance. Forty-six of the more abundant taxa are described and illustrated, with notes on their autecology and relative abundance through time. The diatom community exhibits changes through time, such as a decline in diversity and a shift to predominantly pelagic species, with land-use changes that have occurred since European settlement of the Chesapeake Bay watershed. Many species observed in older sediment samples have apparently not been reported previously for Chesapeake Bay.