Science Centres: Aquatic Biodiversity and Biosecurity

 

The Gemex^TM pumping rig (NIWA’s Neil Blair is on the left) at Princhester Creek. (Photo: Bill Jarvie, Fish & Game Southland)

NIWA’s role in the battle against didymo took a significant step when it conducted a carefully orchestrated field trial to test control possibilities in Southland in February.

NIWA has been researching the chelated copper product, Gemex^TM, which was released into Princhester Creek, a tributary of the Mararoa River, at a prescribed rate over an hour on a single afternoon. Since the release, the stream has been regularly monitored. Early results are promising, both in terms of didymo control and lack of impact on fish and invertebrate communities, according to NIWA team leader Dr Sue Clearwater.

Although complete didymo eradication was never expected, the hope is that Gemex will prove a suitable tool to control infestations to low levels. This research has been done as part of Biosecurity New Zealand’s didymo science programme, and a full report on the trial is due to be delivered to Biosecurity New Zealand shortly.

NIWA scientists have also updated their didymo distribution model and produced updated colour-coded maps predicting likely levels of didymo infestations in rivers throughout New Zealand. Predictions are informed by surveys of existing infestations in the South Island and by modelling environmental factors that favour the growth of didymo, such as river flow and river substrate characteristics.