Didymo is an invasive pest alga that arrived in New Zealand in the early 2000s. It can smother rivers beds with ‘rocksnot’ - a thick layer of weedy sludge. Nothing eats it, only flooding reduces it, and its already affecting over 200 rivers in the South Island of New Zealand.

Its not affecting the North Island…………yet.

There is currently no government or other research that we know of that is trying to clear our rivers of Didymo, so we are stepping up and trying to do something about it. Please read our Project page to find out how…….

This picture of the Upper Ohau River shows the didymo coating the river bed, which severely damages the river ecosystem and biodiversity, as well as looking awful - more like a brown sewer than a pristine high country stream.

This is didymo. Such a small alga to be causing so much damage.

The above pictures have been used with kind permission from Landcare Research Manaaki Whenua (top and bottom pictures) and NIWA (middle picture).