Poster Presentation NCGRT/IAH Australasian Groundwater Conference 2019

Evaluating the presence of chemotaxic microbes at a hydrocarbon contaminated site undergoing remediation (489)

Cameron Murphy 1 2 , Matthew Morgan 3 , Butler Adrian 2 , John Rayner 1 , Trevor Bastow 1 , Thomas Walsh 3 , Greg Davis 1 , Geoffrey Puzon 1
  1. Land & Water, CSIRO Floreat, Perth, WA, Australia
  2. Department of Civil and Environmental Engineering, Imperial College of Science, Technology and Medicine, London, United Kingdom
  3. Land & Water, CSIRO Black Mountain, Canberra, ACT, Australia

Groundwater is a vital source of drinking water for many communities worldwide, however the resource is vulnerable to contamination. In order to evaluate remediation practices, biologically driven processes such as natural attenuation (NA) need to be studied in detail. One aspect of this remediation technique which is not fully understood is microbial chemotaxis. This biological phenomenon allows certain microorganisms to direct their motion in accordance with a chemical gradient. In this study we investigated the various groupings of indigenous microbial genera present at a petroleum contaminated legacy site near Perth, Western Australia, based on their chemotactic and hydrocarbon degrading abilities. The site is around 60 years old and has been subjected to sporadic episodes of contamination, with the contamination been linked with leaking storage tanks and accidental spillages. The overall complex is comprised of multiple zones of contamination associated with differing ranges of petroleum hydrocarbon; crude, diesel and jet fuel. A total of 108 samples from 9 cores; including a representative background control core, were chosen for 16S rRNA Amplicon sequencing. The relationships between the detected microbes, core section, moisture content, contaminant type, and total petroleum hydrocarbon (TPH) concentration (g/kg); including concentrations for several non-aqueous phase liquids (NAPLs) (mg/kg) were investigated. The microbial genera detected were split into five groups; chemotactic (towards hydrocarbons) and hydrocarbon degrading (CD), chemotactic (towards other compounds) and non-hydrocarbon degrading (C), non-chemotactic (towards hydrocarbons) and hydrocarbon degrading (D) and non-chemotactic (towards all compounds) and non-hydrocarbon degrading (NCND); with unclassified taxa at a genus level also being represented (Genus N/A). Microbial community analysis undertaken utilising multiple ecological techniques, such as ordination and network analysis, revealed that the CD grouping is dissimilar in nature to the other groupings and it occupies a slightly different ecological niche. The keystone taxa within the CD grouping are Pseudomonas and Achromobacter, these genera are principally located in the bottom section of jet fuel zone, with their prevalence being governed by the NAPLs; such as naphthalene. These results are, to the best of our knowledge, the first to demonstrate the different distributions of genera based on their chemotactic and hydrocarbon degrading abilities at a legacy site, as well as providing vital knowledge of the genera within the CD group potentially capable of influencing the rate of NA.