Influence of Corexit 9500A and Alaska North Slope Crude oil toxicity to the ammonia-oxidizing bacteria, Nitrosomonas europaea, and the ammonia-oxidizing archaea, Nitrosopumilus maritimus

• Main Author: Schneider, Margaret C.
• Other Authors: Semprini, Lewis, Oregon State University. Honors College
• Format: Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Alaska North Slope; north slope; Alaska
• Online Access: https://ir.library.oregonstate.edu/concern/honors_college_theses/2801pj32s

The inhibitory effects of Corexit 9500A, Alaska North Slope Crude oil (ANSC), and mixtures of the two on the ammonia-oxidizing bacteria, Nitrosomonas europaea, and the ammonia-oxidizing archaea, Nitrosopumilus maritimus, were investigated. Corexit 9500A was found to be minimally toxic to both microorganisms with concentrations of 2000 and 3000 ppm yielding a 50% reduction in nitrification activity. The water-associated fraction (WAF) of ANSC was found to be reasonably toxic to N. europaea and N. maritimus with concentrations of 6 and 7 mL per 50 mL media resulting in 50% inhibition. Corexit 9500A:ANSC dispersant enhanced water-associated fraction (DEWAF) mixtures were found to be more toxic to each species as the ratio increased and as larger volumes were added per 50 mL media. ANSC WAF was found to be the most toxic, compared to the DEWAF mixtures, to both N. europaea and N. maritimus when compared on a per COD basis as most of the COD without dispersant present is attributed to low molecular weight aromatic hydrocarbons. These hydrocarbons are, most likely, the cause of the majority of inhibition caused by crude oil. Using dispersants, such as Corexit 9500A, may have a significant effect on microorganism activity and population due to the toxicity of hydrocarbons present in crude oil. In general, similar responses were observed in the different exposures of both microorganisms.