Molecular screening of microbial communities for candidate indicators of multiple metal impacts in marine sediments from northern Australia

Alyssa Cornall, Alea Rose, Claire Streten, Keith McGuinness, David Parry, Karen Gibb

Coastal sediments accumulate metals from anthropogenic sources and as a consequence industry is required to monitor sediment health. The total concentration of a metal does not necessarily reflect its potential toxicity or biological impact, so biological assessment tools are useful for monitoring. Rapid Biological Assessment (RBA) tools sensitive enough to detect relatively small increases in metal concentrations would provide early warning of future ecosystem impact. We investigated in situ populations of Archaea and Bacteria as potential tools for RBA in sediment at 4 northern-Australian coastal locations over 2 years, in both wet and dry seasons. The 1 M HCl-extractable concentrations of metals in sediment were measured, and Archaeal and Bacterial community profiles obtained by next-generation sequencing of sediment DNA. Species response curves were used to identify several taxonomic groups with potential as biological indicators of metal impact. Spatial variation, sediment grain size, water depth and dissolved oxygen also correlated with microbial population shifts. Seasonal variation was less important than geographic location. Metal-challenge culture trials supported the identification of metal resistant and sensitive taxa. In situ Archaea and Bacteria are potentially sensitive indicators for changes in bioavailable concentrations of metals, however the complexity of the system suggests that we also need to identify metal-specific functional genes that may be informed by these sequencing surveys, and thus provide a useful addition to identity-based assays. This article is protected by copyright. All rights reserved.