Titiko snails are set to be the focus of researchers investigating effects of the Te Maunga wastewater treatment plant on Tauranga's harbour ecosystem in the next two years.

Tauranga City Council's Wastewater Management Review committee is recommending council pay $156,710 to two iwi groups to further monitor titiko snails and assess the effects of seepage from the Te Maunga wastewater treatment ponds on their habitat.

New Zealand mud snail.

Council is already required as part of its environmental consent to monitor the snails, but the consent outline does not to further than monitoring.

The annual report on the consent, presented at this week's Wastewater Management Review committee meeting, shows the titiko are doing well, with a good proportion of mature snails at the sites that have to be monitored, though numbers and locations vary across the sites.

According to the report, seepage – from the Te Maunga treatment ponds – appears to limit abundance and biodiversity in the immediate vicinity, affecting about 63m2 of the inter-tidal area of Rangataua Bay. The seepage is not expected to have any significant effect on the estuary water quality, says city waters consents officer John Gibbons-Davies in the report.

The Manaaki Te Awanui Charitable Trust is receiving $130,000 for its titiko study, which its application states will be incorporated with a cultural evaluation of the study area, using a framework developed by Manaaki Taha Moana called the ‘Coastal Cultural Heath Index', to provide a more robust and holistic approach to wastewater monitoring.

Sampling will be undertaken over a distance gradient from the beach, to identify what cumulative effects are impacting on key species and what carry on effect there is at varying distances.

The second research effort is a $27,600 combination Nga Potiki/Tauranga City Council research and educational effort that will use isotope analysis to investigate the snails' environmental backgrounds.

Snails, water, sediment and sea lettuce samples will be collected across the estuary and the various nitrogen isotopes will be analysed at GNS Science in Wellington

Different isotope signatures will show if the snails are being polluted by seepage from the Te Maunga ponds, or from local drains, septic tanks etc.

The research into the estuary will also provide educational opportunities, by using the research data to inform the greater community of the state of the environment; and to educate the community on the impact wastewater has on the environment when incorporating cultural aspects.

The research funding comes from $250,000 fund the city council is required have set aside as a condition of its sewage discharge and seepage consents.

It has taken six years to access the funding from the Wastewater Management Review Committee, which was established in 2007 – also being a requirement of the resource consent, as is the committee's tangata whenua/city councillor make-up.