A few months back an algal bloom turned the Hawke Bay sea red. Now another has turned one of the region's lakes bright green.
Lake Tutira, on State Highway 2 between Napier and Wairoa, is partly covered by an eye-catching bright green and pungent toxic scum.
Testing on the 174-hectare lake, usually popular with anglers and campers, had revealed high levels of toxic cyanobacteria, and signs warning people to avoid contact with the water had been put up.
Hawke's Bay Regional Council scientist Adam Uytendaal said the lake had historically suffered from algal blooms, partly because of sediment and nutrient runoff from surrounding hills, but there had not been one for several years.
"It's really quite a substantial bloom, with a significant amount of surface scum," Mr Uytendaal said.
"The challenge for us is to tease out exactly what has caused this. Climatic conditions and turbidity are likely to have played a part, including some recent rainfall events and possibly the rapid increase in the lake level," he said.
There were no "quick fix environmentally friendly solutions to deal with algal blooms like this", but he hoped that nutrients in the surface waters would reduce and the bloom dissipate during this month. People consuming fish or shellfish from the lake should avoid eating the gut and organs because these accumulated toxins.
During several days in mid-August a red algal bloom appeared along the coast between Cape Kidnappers and Wairoa.
It was identified as a non-toxic algal bloom named akashiwo sanguinea. Akashiwo is Japanese for red tide, and was thought to have been linked to nutrient runoff after heavy rain.
- © Fairfax NZ News
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