Long-term effects on microbial communities after a subarctic oil spill

A combination of microbial assays was used to examine soil population struc ture and community-level metabolism at the site of a 1976 experimental crud e oil spill conducted in Alaska. Estimates of total bacterial numbers and s oil C mineralization potentials were not significantly different between pr istine and hydrocarbon-affected soils. In contrast, net N mineralization po tential was lower, metabolically active (FDA stain) bacteria were less abun dant and hydrocarbon degrading microbes were more abundant in the oiled soi ls. Additionally, the effects of dilution on the kinetics of community-leve l substrate use were examined in multiple substrate microplates. Microplate kinetic patterns varied less with dilution and by season in oiled soils. I n oiled soils, absence of seasonal variation in soil C mineralization poten tials, coupled with the microplate data, indicated that population diversit y (evenness, richness or both) was diminished compared to the pristine soil s. Further analysis of microplate data suggested that the communities survi ving in the oiled soils may be considered metabolic generalists. By using s everal independent microbial assays, differences in soil microbial communit y structure attributable to oiling could be seen decades after the spill ev ent. (C) 1999 Elsevier Science Ltd. All rights reserved.