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: Thirty in-shore sites were selected in Darwin Harbor (Fig. 1; Table 1) and included beaches subject to high bacterial concentrations at sites 4, 15, 16, 23, 24 and 29. Two beaches at sites 3 and 30 were considered reference beaches that had never previously had elevated bacterial counts. Three sewage outfalls (sites 1, 14, and 27) were included, each with different sewage treatment strategies. The Leanyer-Sanderson outfall (site 1) is treated using a pond (secondary) treatment process with surface aeration, the Ludmilla outfall (site 14) by an enhanced primary treatment consisting of screening, grit removal and precipitation of suspended and coagulated solids using chemicals (including chlorine), and Larrakeyah outfall (site 27) by maceration only. Other suspected inputs, such as urban rivers and drains, were included because of previous high bacteria counts, or because of their proximity to outfalls, to hobby farms or areas with high fertilizer use. There were multiple sites along the suburban “Rapid Creek” because there was a view it was involved in the closure of Rapid Creek Beach (site 4). Other sites included storm water drains at Chapman Rd (site 5), Botanic Garden (site 22), a golf pond (site 25) and a marine lake (Lake Alexander sites 17 and 18).
Affiliation: Research Institute for the Environment and Livelihoods, Charles Darwin University, Casuarina, Northern Territory, Australia.