Effects of Fractions from Biodegraded Alaska North Slope Crude Oil on Embryonic Inland Silversides, Menidia beryllina

Abstract

Embryonic inland silversides, Meinida beryllina, were exposed to neutral, water-soluble fractions (WSFs) resulting from microbial degradation of artificially weathered Alaska North Slope (ANS) crude oil. Three individual microbes obtained from Prince William Sound, Alaska, and designated Phe#6 (enriched on phenanthrene), Hexaco#2 (enriched on the straight-chain alkane, hexacosane), and EI2V (grown by enrichment on Bushnell-Haas medium containing 0.2% pristane, a branched alkane) were used to individually biodegrade weathered ANS crude oil for 14 days in darkness in 20-L glass carboys containing nutrient enriched, sterilized 20‰ salinity sea water at 20 ± 1°C. Neutral WSFs resulting from biodegradation of ANS (lot 521) by each microbe were recovered and weighted. Neutral WSFs recovered were: 1.76 mg/L for Phe#6, 1.85 mg/L for Hexaco#2, and 13.02 mg/L for the EI2V microbe. Embryo toxicity and teratogenicity tests revealed that exposure of embryos to the WSFs from the EI2V incubation (with a total recovered neutral fraction approximately seven times greater than the Phe#6 and Hexaco#2 incubations) resulted in the most severe responses in craniofacial, cardiovascular, and skeletal organ systems. The total neutral WSFs recovered from the EI2V biodegradation of weathered ANS 521 were subfractionated into saturated (eluted with hexane), aromatic (eluted with CH₂Cl₂), polar (eluted with ethyl ether), and recombined (saturated + aromatic + polar) fractions. Developing fish embryos were then exposed to each subfraction and the recombined subfractions. The polar subfraction and recombined subfractions proved to be the most embryo toxic and teratogenic. They resulted in statistically significant (p ≤ 0.05) responses (compared to controls) for craniofacial, cardiovascular, skeletal, and total severity effects in one or both tests with these subfractions.