Figure 3. Comparisons on a common time scale (100 days, about 14 weeks) of mean (±1 SD) of sediment chemical, microbial and toxicological conditions in replicate (n=5) plots treated with weathered Light Bonney Nigerian crude oil (Oil control, open square), oil plus continuous application of dissolved nutrients (Nutrient. closed diamond), oil treated with both dissolved nutrients and cultured bacteria consortia (Bacteria, darksquare), and unoiled and untreated (NO oil control, open diamond) on a sandy beach in Delaware, July-October, 1994. There were no significant differences among the 3 oiled treatments for loss rates of extractable organic material (EOM, a rough measure of TPH, total petroleum hydrocarbons) (A) or hopane, a recalcitrant (non-degradable) hydrocarbon (B). All measurements of EOM and hopane referenced to initial concentrations (C/Co; Co about 5,000 mg/kg dry wt for EOM and about 200 μg/kg dry wt for hopane; background EOM was bout 10 to 80 mg/kg dry wt and hopane about 0.007 μg/kg dry wt). However, relative to untreated oil controls, analyte-to-hopane ratios demonstrated that nutrient and nutrient+bacteria application equally and doubled the loss rates of C10-C35 alkanes (C) and increased by 20 to 50% the loss rates of the total of 27 2-5-ring polycyclic aromatic hydrocarbons (D). Concentrations of sediment alkane degrading bacteria (E) increased rapidly in response to both treatments and then slowly declined whereas concentrations of PAH degrading bacteria (F) increased more slowly in response to both treatments and then declined. Relative to unoiled controls, beach pore water samples taken at 42-day (six-week) intervals from oiled plots were initially slightly inhibited sea urchin egg fertilization (G) but significantly depressed light production of photoluminescent Microtox bacteria (H) and hatchability of grass shrimp embryos (I,n=2 per treatment per sampling event); toxicity was lost at different rates but with no significant difference among oil treatment types. Bulk sediment elutriate was initially highly toxic to Microtox organisms (J) but toxicity declined. Bulk sediment from oiled plots also highly depressed 10-day survival of benthic amphipods (K) throughout the entire monitoring period and there was some toxicity in the on oiled control plots themselves. Oil lost from the 1-km beach study zone was initially accumulated (as PAH's) in oysters placed in cages several meters seaward of the study blocks (Central), upstream of the study site (South) and downstream of the study site (North)(L); in all cases depuration was nearly complete in 28 days.
