Assigning Experimental Groups
    For both events, oysters were randomly separated into five groups with 50 oysters in each. To prevent overcrowding of the organisms, each of these groups was then divided into a sub-group of 10 oysters. 3.0 mm square mesh sieves were used to hold each sub-group. Since the administered doses of atrazine were diluted in acetone, the Acetone 30 μg/L control group was used in order to ascertain acetone was not causing the observed effects within treatment groups. Each group of 50 oysters was assigned to one of six treatments: 0 μg/L Atrazine/Acetone, 3 μg/L Atrazine, 10 μg/L Atrazine, 20 μg/L Atrazine, 30 μg/L Atrazine, and 30 μg/L Acetone.
   Exposures
    All oyster groups were kept in separate tanks to avoid any potential cross contamination. In order to expose the oyster groups to atrazine and acetone, each group was removed from its holding tank and placed into a separate 4-liter glass tank containing 2 liters of newly made  seawater (salinty= 25 ppt).  Atrazine was added to each 4-liter glass tank according to the corresponding treatment concentration. In order to mimic the heavy rainfall pattern surrounding the Chesapeake Bay (USGS: Chesapeake Region Climate/Precipitation Data), treated groups spent a total of 3 hours submerged in the treated 2 liters of saltwater three times per week, every other day (Monday, Wednesday, Friday). Aeration was provided in both holding and treatment tanks. 
    Following  each stabilization period, the experimental groups were introduced to their first exposure. Four individual 4-liter glass tanks were used to hold different concentrations of a atrazine/acetone-saltwater mixture ( 25ppt): 3μg/L atrazine, 10 μg/L atrazine, 20 μg/L atrazine, 30 μg/L atrazine and, 30 μg/L acetone  respectively.  The treatment rounds were conducted for a total of 30-days. For one of the events, surviving oysters were allowed to continue to grow for an additional 30-day recovery period.
    In order to minimize any potential contamination of the each group's respective holding tanks after the 3-hour exposure period, each group was washed using a constant stream of pressure-filtered water for three one-minute rinses. Oyster groups were then relocated to their respective 40-liter glass bio-cube tanks. The bio-cube tanks were set to have the same parameters as the large holding tank.