OIL BIOREMEDIATION IN SALT-MARSH MESOCOSMS AS INFLUENCED BY N-FERTILIZATION AND P-FERTILIZATION, FLOODING, AND SEASON

Bioremediation of crude oil in salt marsh mesocosms growing Spartina a lterniflora was investigated during winter and summer to determine the influence of nitrogen (N) and phosphorus (P) fertilization, flooding, and season. Fertilization with urea and ammonium (NH4+) applied at 75 or 150 kg N ha(-1) with or without P did not significantly (p = 0.05) increase oil or hydrocarbon degradation in continuously flooded mesoc osms over an 82 day period during winter (temperature range of 17 to 3 0 degrees C). Phosphorus applied at 40 kg P ha(-1) significantly (p = 0.05) increased oil and hydrocarbon degradation. Nitrate (NO3-) added alone did not increase oil or hydrocarbon degradation, but when added with P, it significantly (p = 0.05) increased degradation above that f or P alone. Up to 70% of applied oil and 75% of applied hydrocarbons w ere degraded in P supplemented treatments. Inipol, an oleophilic ferti lizer containing N, P, and a dispersant, significantly increased oil a nd hydrocarbon degradation. During a 40 day summer experiment (tempera ture range of 27-42 degrees C), N and P fertilization did not increase oil or hydrocarbon degradation. For continuously flooded treatments, 72% of applied hydrocarbons were degraded while 51% were degraded in a lternately flooded treatments. Mesocosms provided conditions suitable for quantitative recovery of oil and results indicated that N and P fe rtilization, flooding, and season interacted to influence oil bioremed iation. Even under the most favorable conditions, more than 1 month wa s required for most of the oil to disappear.