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Summer of science for Tauranga Harbour

Monday, 21 December 2015 10:00 a.m.

While many locals and visitors relax on the beach this summer, Bay of Plenty Regional Council’s science team will be out collecting information to check on Tauranga Harbour health.

With the help of summer student Amy Platt, Regional Council Coastal Scientist Rob Win has been deploying cages of Pacific oysters around the harbour that will be used to check on levels of oil and metal contamination in the water.

“We already have a good handle on sediment contamination, faecal contamination, nutrient, and clarity levels through our annual monitoring work. This oyster study will add to our data set along with a five year sediment accumulation study that we’re now three years into.

Oysters are filter feeders, so if there’s pollution in the water column it will be absorbed into the oyster tissues. We have some great data from an oyster study that was completed in 1991 so it’s timely to repeat the study and see what changes and trends can be seen,” said Mr Win.

The oysters have been brought in from Ōhiwa Harbour and deployed at ten sites throughout the Tauranga Harbour. They’ll be retrieved in February for tissue sample analysis and compared with tissue samples from the Ōhiwa source population, as well as wild oysters which will also be collected from Tauranga Harbour.

The 1991 study found that a range of metals and oil-based pollutants (hydrocarbons) were present throughout the harbour but not at levels of concern to human health. The highest concentrations were found in Waikareao Estuary and around the Port.

A sediment contamination study completed by Regional Council staff last year found that levels of metal and oil pollutants in the Tauranga Harbour bed were within safe limits. Some elevated levels were detected at one site in Waimapu Estuary, near Fraser Cove.

“That prompted pollution audits of 80 business premises in the Maleme Street and Fraser Cove industrial areas. One problem with a wash bay was found and fixed. Pollution Prevention staff are now helping 50 of the other audited businesses to make minor improvements that will reduce storm water pollution,” said Mr Win.

Mr Win said that oil and metal pollution could be entering the harbour from road run off, poorly maintained boats or illegal discharges. This year’s oyster study will help Council to identify any further pollution problem areas that need investigation.

In the meantime the scientists have plenty to do while they wait for the oysters. They have 60 sediment plates throughout the harbour that need to be measured and they’ll be collecting weekly bathing water samples from ten popular harbour and river swimming spots.

“We’re checking the sediment plates four times a year so we can measure seasonal changes and detect sediment accumulation hotspots. Our Land Management team are already working closely with landowners to reduce sediment run-off, but having a clearer picture of sediment dynamics in the harbour will help us to make sure we’re targeting locations and activities that will make the biggest difference,” Mr Win said.

Bathing water sample results can be viewed at www.boprc.govt.nz/taurangawaterqual. Further information about Regional Council’s work and the health of Tauranga Harbour can be viewed at www.boprc.govt.nz/taurangaharbour  

Click on images below to view high resolution versions.

Rob Win - Oyster cage Oyster cage

Rob Win - Oyster cage