Bacterial targets as potential indicators of diesel fuel toxicity in subantarctic soils.
Appropriate remediation targets or universal guidelines for polar regions do not currently exist, and a comprehensive understanding of the effects of diesel fuel on the natural microbial populations in polar and subpolar soils is lacking. Our aim was to investigate the response of the bacterial community to diesel fuel and to evaluate if these responses have the potential to be used as indicators of soil toxicity thresholds. We set up short- and long-exposure tests across a soil organic carbon gradient. Utilizing broad and targeted community indices, as well as functional genes involved in the nitrogen cycle, we investigated the bacterial community structure and its potential functioning in response to special Antarctic blend (SAB) diesel fuel. We found the primary effect of diesel fuel toxicity was a reduction in species richness, evenness, and phylogenetic diversity, with the resulting community heavily dominated by a few species, principally Pseudomonas. The decline in richness and phylogenetic diversity was linked to disruption of the nitrogen cycle, with species and functional genes involved in nitrification significantly reduced. Of the 11 targets we evaluated, we found the bacterial amoA gene indicative of potential ammonium oxidation, the most suitable indicator of toxicity. Dose-response modeling for this target generated an average effective concentration responsible for 20% change (EC20) of 155 mg kg(-1), which is consistent with previous Macquarie Island ecotoxicology assays. Unlike traditional single-species tolerance testing, bacterial targets allowed us to simultaneously evaluate more than 1,700 species from 39 phyla, inclusive of rare, sensitive, and functionally relevant portions of the community.
School of Biotechnology and Biomolecular Sciences, UNSW Australia, Randwick, New South Wales, Australia.
Josie
J
van Dorst
Department of Soil Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Steven D
SD
Siciliano
School of Biotechnology and Biomolecular Sciences, UNSW Australia, Randwick, New South Wales, Australia Department of Soil Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada Terrestrial and Nearshore Ecosystems Program, Australian Government Antarctic Division, Kingston, Tasmania, Australia.
Tristrom
T
Winsley
Terrestrial and Nearshore Ecosystems Program, Australian Government Antarctic Division, Kingston, Tasmania, Australia.
Ian
I
Snape
School of Biotechnology and Biomolecular Sciences, UNSW Australia, Randwick, New South Wales, Australia b.ferrari@unsw.edu.au.
Belinda C
BC
Ferrari
D000864:Antarctic Regions; D001419:Bacteria / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D058448:Biota / Q000187:drug effects*; D004787:Environmental Pollution; D005742:Gasoline / Q000633:toxicity*; D014644:Genetic Variation / Q000187:drug effects; D010088:Oxidoreductases / Q000235:genetics; D010802:Phylogeny; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000633:toxicity*
D005742:Gasoline; D012989:Soil Pollutants; D010088:Oxidoreductases; C045582:ammonia monooxygenase