Science Centres: Aquatic Biodiversity and Biosecurity

NIWA student Phillip Jellyman examining fish in didymo biocide trials at Monowai Power Station. [Photo: Neil Blair, NIWA]

NIWA has identified a copper-based compound as a potentially effective and safe weapon against the invasive alga didymo, although further tests are needed to determine its effectiveness in rivers.

Recent laboratory trials for Biosecurity New Zealand have shown that the compound successfully killed didymo without harming juvenile rainbow trout. NIWA scientist and world didymo expert Dr Barry Biggs says that native fish and invertebrates are likely to be even less sensitive to the chemical than rainbow trout.

The compound will be further tested for its effects on didymo and other freshwater organisms in purpose-built mock streams at Monowai Power Station. These trials should get underway at the end of September.

Meanwhile, NIWA has surveyed a further 100 high-risk sites for the presence of didymo for Biosecurity New Zealand. Didymo was found at five new South Island sites, all of which are in, or very close to, known didymo-affected catchments. Didymo was not detected at any North Island sites.