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Story: Water quality

A handful of didymo

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A handful of didymo

Didymosphenia geminata – known as didymo or ‘rock snot’ – causes serious damage to waterways. Although it looks slimy, it feels like wet cotton wool. First detected in New Zealand in 2004, it is native to the cool waters of northern North America and Europe.

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Ministry for Primary Industries, Biosecurity New Zealand

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How to cite this page

Mike Scarsbrook and Kit Rutherford, Water quality – Problem plants and microbes, Te Ara – the Encyclopedia of New Zealand, https://teara.govt.nz/en/photograph/15526/a-handful-of-didymo (accessed 4 June 2026).

Story by Mike Scarsbrook and Kit Rutherford, published 1 March 2009, updated 18 July 2016.