The project was designed to assess the effects of agricultural herbicides on submerged aquatic vegetation in the Lower Chesapeake Bay. Atrazine was selected for testing because it is the most widely utilized herbicide in the Bay region. Zostera marina was the submerged vegetation studied. The project began with two surveys. The first survey, conducted in 1979, covered forty eight stations throughout the Virginia portion of the Chesapeake Bay. The survey was designed to indicate typical atrazine loading for the lower Bay. A second survey in 1980 was limited to the Severn River, and was intended to indicate the duration of peak atrazine loading. Field dosing experiments, utilizing large plexiglass enclosures, measured effects of short-term atrazine exposure on the net production of the Zostera community. Greenhouse experiments, utilizing a flow-through dosing system, measured effects of long-term (21 day) atrazine exposure on the morphology of mature Zostera plants.