Multiple approaches to microbial source tracking in tropical northern Australia.
Bottom Line: To address this, we sampled sewage outfalls, other potential inputs, such as urban rivers and drains, and surrounding beaches, and used genetic fingerprints from E. coli and enterococci communities, fecal markers and 454 pyrosequencing to track contamination sources.Two other treated effluent discharges did not appear to influence sites other than those directly adjacent.Generally, connectivity between the sites was observed within distinct geographical locations and it appeared that most of the bacterial contamination on Darwin beaches was confined to local sources.
Affiliation: Research Institute for the Environment and Livelihoods, Charles Darwin University, Casuarina, Northern Territory, Australia.Show MeSH
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Mentions: Water samples for bacterial community analysis were collected in duplicate from 30 sites in Darwin Harbor (Fig. 1; Table 1). A schematic of the processing procedures is given in Figure 2. The sites were sampled at approximately the same time (3 h after a spring high tide) on June 20, 2011. At the outfalls samples were taken before mixing with the receiving waters. The samples were obtained by inverting a sterile, 1 L bottle ˜20 cm below the water surface. The samples were then placed on ice and taken to the laboratory for analysis. An additional 250 mL of water was collected at each site, kept on ice, and sent to the Australian Water Quality Centre (AWQC) in Adelaide, South Australia. At the AWQC, samples were tested for E. coli, enterococci and fecal coliforms using membrane filtration in accordance with Australian/New Zealand Standards (AS/NZS 4276.5). Briefly, 100 mL of water was filtered through a 0.45 μm membrane filter, which was then placed on membrane lauryl sulfate media at 36 ± 2°C. Colonies were enumerated and results were expressed as colony-forming units per 100 mL (CFU/100 mL). At each site, turbidity, total suspended solids (TSS), temperature, dissolved oxygen (DO) and electrical conductivity (EC) were measured using a Hydrolab Datasonde 4a (Austin, TX, USA) and a YSI 6-Series sonde (Yellow Springs, OH, USA). Total nitrogen (TN), total phosphorous (TP), nitrite (NO2), nitrate (NO3), and ammonia (NH3) were measured in filtered water samples using flow injection analysis (FIA) according to standard methods (APHA 1989).
Affiliation: Research Institute for the Environment and Livelihoods, Charles Darwin University, Casuarina, Northern Territory, Australia.