18 August 2020
By Adrian Cookson, AgResearch in Palmerston North.
I’m a Microbiologist and am very interested in analysing the Escherichia coli bacteria as indicators of faecal contamination in waterways. My previous work in collaboration with Massey University, NIWA, ESR and Horizons Regional Council (https://ourlandandwater.nz/future-landscapes/faecal-source-tracking/) has compared the E. coli from native bush environments as our baseline sites, and compared them to E. coli identified from agricultural sites. Our strategy has been to obtain water, soil, sediment, and deposited faecal samples from birds and animals at the different sites, use special growth media to culture the E. coli, and then undertake genetic analysis of the E. coli we culture. Our work has demonstrated that there are ‘naturalised’ E. coli specialised for environmental persistence, that inhabit our waterways which likely make it difficult for Regional Councils to accurately assess the extent to which our waterways are contaminated with faecal material from farms or urban wastewater.
Our initial two-year study where we sampled waterways in the Manawatū River Catchment and an artificial wetland in Waikato, has finished, but we were fortunate to receive further funding to continue and broaden our work. Previously we targeted Pūkaha Mount Bruce (https://pukaha.org.nz/) as our baseline site visiting to obtain samples on 6 occasions over a year. Pūkaha is a mainland island just north of Masterton where intensive trapping of possums, rodents and mustelids occurs to improve the breeding success of the native birds and plants present in the 965-hectare bush remnant. For the up-coming work we hope to sample at other mainland island bush sites where pests are intensively managed to provide some clues on the distribution of the environmental E. coli and whether they are found throughout New Zealand. For each baseline site we will also work with the local Regional Council to identify a local matching agricultural site outside the reserve where we will also study the E. coli. Ultimately we hope to provide new methods to detect E. coli for more accurate assessments of water quality that can be used by Regional Councils, community groups and iwi.