Abstract:

Culture health was assessed by chlorophyll concentration. In vivo fluorescence, measured twice weekly via Turner 10-AU fluorometer, was used as a proxy measurement of chlorophyll concentration. To account for fluorescence signal interference from oil components, control solutions containing sea water, chemical dispersant, and crude oil were prepared and measured along with the phytoplankton exposures. The fluorescence signal from the control group was subtracted from the exposure group. Triplicate samples of WAFs and CEWAFs were analyzed for target hydrocarbons. As there are thousands of compounds in crude oil, only the most abundant, most common, and most toxic were targeted for analysis. The samples were liquid-liquid extracted with methylene chloride, and the extracts were analyzed by Gas Chromatography - Mass Spectrometry (GC-MS). Analysis by GC-MS used an Agilent 7890A GC system configured with a 5% diphenyl/95% dimethyl polysiloxane high resolution capillary column (30-meter, 0.25 mm ID, 0.25 micron film) directly interfaced to an Agilent 5975 inert XL MS detector system. The MS was operated in the Selective Ion Monitoring (SIM) mode to maximize the detection of the target constituents unique to crude oil. The concentrations of target PAHs were determined by an internal standard method and response factors calculated from a 5-point calibration curve using commercially available standard containing the normal alkanes from n-C10 through n-C35 and the parent PAH analytes of interest.