Animals were the likely cause of E.coli contamination in the Waiotahe estuary according to testing by the Bay of Plenty Regional Council.
In January Toi Te Ora Public Health issued a health warning advising against eating shellfish collected from the Waiotahe pipi beds. This was as a result of routine monitoring by the Bay of Plenty Regional Council which showed high levels of faecal indicator bacteria in the water over a period of time.
Results of recent faecal source tracking carried out on water samples from the Waiotahe catchment pointed to ruminant animals as the likely cause contamination in the estuary.
The warning is specifically related to eating shellfish and there were no concerns around other recreational uses. Shellfish feed by filtering water and therefore tend to concentrate any bacteria or other toxins.
Looking into the potential sources of faecal contamination in the estuary the regional council established a number of new monitoring sites in drains and tributaries that flow into the Waiotahe River.
When tests indicated high counts of faecal indicator bacteria such as E.coli, the council undertook faecal source tracking to better establish the sources of contamination.
Six sites were analysed for the DNA markers that separated human, ruminant (cow), and avian (bird) faeces. Results in the estuary showed weak evidence of a ruminant source.
Two sites in the Waiotahe River showed weak to moderate ruminant sources.
Drain results had weak to moderate ruminant sources and one drain had a strong ruminant source. Avian sources were also found in most locations. There was no confirmed contamination detected from human sources.
Bay of Plenty Regional Council Land Management Officer for the Eastern Catchments, Tim Senior said while the results were not surprising they were a useful piece in the puzzle to work towards a long term solution.
"The DNA results are perhaps not surprising but they do help us form a better picture of catchment health and water and bacteria movement.
"We are working on a more detailed and comprehensive water monitoring programme in the Waiotahe and have engaged a number of scientists both within and from outside the organisation to help us identify the extra work needed."
Mr Senior said council was focussed on protecting water quality proactively with a range of industries and landowners to reduce run-off from the many land-use activities that can degrade water quality.
"Incentives to ensure streams and drains are fenced, stock river-crossing avoided, bush and wetlands protected and planting is done where possible. But it is likely that given the low-lying nature of much of this catchment and some of the issues we are seeing we will need a number of extra initiatives to work on with the farmers," he said.
"Farmers in this catchment have already shown a great willingness to engage with us around this work. In fact, the winners at the recent Bay of Plenty Ballance Farm Environment Awards, Waiotahi Valley dairy farmers Jared and Sue Watson, are proactive in working collaboratively to manage effluent run-off from dairy farms. They have been a clear voice for sustainable farming in the catchment."
He said they were also working with the local hapu, Te Upokorehe, and the wider community who were understandably concerned about the contamination.
"It is great to see a community response to this as there is no one simple solution and it is likely that a wide range of measures will need to be implemented. And this work will take time and collective effort," he said.