Water Journal : Current May 2016
www.awa.asn.au executive summary water quality 117 EXAMINING THE ASSOCIATION BETWEEN BACTERIA COMMUNITY COMPOSITION AND ELEVATED NUTRIENTS IN ESTUARIES. Broadening the targets for microbial water quality K Gibb, M Kaestli, J Smith, K McGuinness DNA technologies afford an unprecedented opportunity to broaden microbial water quality targets for routine monitoring. It is now well understood that conventional indicators Escherichia coli and enterococci can survive and be detected in a range of non-faecal sources, making it difficult to monitor human faecal pollution in receiving environments. The call for broadening targets for water quality assessment has also been driven by applying next-generation sequencing (NGS) to environmental samples, allowing significant advances in our understanding of bacterial community dynamics. NGS has created an unprecedented inventory of microbial communities associated with faecal sources, allowing re-examination of which taxonomic groups are best suited as indicators. While these approaches have opened the door to ecological-scale microbial assessment, we still have much to learn about how microbial communities respond to disturbance. If their response to nutrient gradients, for example, is highly variable both temporally and spatially, then their value as a source of new indicators might be questionable. There are also many regions and ecosystems for which we have no community-level microbial data. Darwin Harbour is one such region, so our aim was to compare the bacterial community composition in sewage/effluent- impacted and control creeks with no sewage effluents. From this, we aimed to increase our understanding of what makes the bacterial communities different, and possible implications for monitoring. We found that the microbial community was more diverse at the site with the highest level of nutrients and diversity decreased with decreasing levels. Taxa such as Aeromonas, Azomonas (see figure) and cyanobacteria have potential as water quality indicators. The Enterobacteriales were interesting: this family contains taxa used in conventional water quality assessment. However, some members also include environmental bacteria and, indeed, our study detected two Enterobacteriales sequences at all sites. Our approach has provided more baseline microbial information for Darwin Harbour, and identified targets for broader public health and ecosystem health monitoring. Professor Karen Gibb is an Associate Professor and Dr Keith McGuinness a Marine Biologist at Charles Darwin University, Dr Mirjam Kaestli is Research Fellow at the Research Institute for the Environment and Livelihoods and Dr Jodie Smith is a Marine Geoscientist at Geoscience Australia. To read the full article, visit the Water e-Journal at bit.ly/e-Journal Bacteria that distinguish sewage-impact (orange boxes) from non-sewage impact sites The top 25 bacteria (sequences) that contributed most to the differences between bacterial communities from effluent-impacted sites (BC, MC and EP) and control sites (HC and WA) were visualised using Cytoscape. The line thickness is proportional to abundance of these taxa. BC had bacteria sequences that were unique or occurred at low levels at the other sites, including those belonging to the Enterobacteriales, Alcaligenaceae, Chlorobiales, Hylemonella and Enteric Bacteria. There were some bacteria common to MC and BC only: a Cyanobium, a Spartobacteria and a cyanobacteria. EP was dominated by an ammonia- utilising Azomonas and the potential human pathogen Aeromonas.
Current Feb 2016
Current August 2016