Science Centres: Aquatic Biodiversity and Biosecurity

A non-toxic dye is used to determine the best method for distributing Gemex^TM quickly and evenly in streams prior to Gemex^TM field trials.

New Zealand scientists continue to lead the world in didymo research. In recent months, we have continued delimitation surveys across the country for Biosecurity New Zealand, made good progress on developing a control biocide, and verified the conditions that will allow didymo to survive on recreational equipment.

North Island response strategy

Fears of didymo spreading to the highly valued Te Waikoropupū (’Pupū’) Springs and the North Island were heightened by its recent discovery in rivers at the top of the South Island. Biosecurity New Zealand and NIWA have together developed a strategy to respond to a North Island incursion, should this eventuate.

Trials of copper-based control aid

Trials in artificial streams showed that Gemex^TM, a chelated copper-based formulation, was very effective at killing didymo cells without harming juvenile rainbow trout. Preliminary results of these trials indicated only moderate effects on invertebrates. Field trials of Gemex^TM will get underway this month to further test its safety and effectiveness against didymo. The formulation has been deliberately designed to be effective against didymo but with low toxicity to other aquatic organisms.

Environment Southland, the Environmental Risk Management Authority, and local iwi have approved small stream trials in a tributary of the Mararoa River, Southland. Preliminary results should be available within a month, although further monitoring will take place for at least 3 to 4 months.

Felt-soled waders may harbour didymo

Laboratory tests showed that felt soles on wading boots retained more live didymo cells than leather boots, neoprene material, or rubber-soled boots because the felt soles stay moist for a long time. Also, the decontamination agents don’t penetrate very easily into the felt, so it’s recommended that felt-soled waders be avoided if possible. If used, they should be frozen or soaked in hot water (preferably with detergent) for long periods. For details, see www.biosecurity.govt.nz.