May 2015 – What the Hell is Didymo?

NZ Süd 1First time in New Zealand. Exploring the south island with all its wilderness, fjords and lush green rain-forests. It is late autumn – almost winter in and around Queenstown.

Driving is fun as there is only very little traffic once we’re out of urban areas. Roads are not bad – sometimes very narrow and winding. General speed limit is 100 kph – with our camper-van only 90 kph as it is considered a “heavy vehicle”.

Again and again we find information signs warning us of didymo. Who or what is that? Seems to be very dangerous. Soon we find out that many New Zealanders use the tasteful name “Rock Snot”. So is it growing/living on rocks?

NZ FähreQueuing up for the ferry from Picton to Wellington (South Island to North Island) we find out. A friendly gentleman dressed in a bright yellow overall approaches us, introduces himself as a representative from the ministry of environment. “Have you been into rivers and creeks within the last few days?” he wants to know. “Have you cleaned you shoes in running water?”

Our answer is “no” and it looks like a burden is taken from his shoulders. Than he explains, that didymosphenia geminata, commonly known as didymo or rock snot has first time been discovered on the South Island in 2005. Since then all items, such as boats, fishing gear, clothing, and vehicles, that have been in a stream, river or lake, must be cleaned before they enter another waterway. And of course before they ferry over to the North Island.

DidymoSo what’s wrong with didymo? Wikipedia says: Didymo can have a notable impact on the insects that are a food source for many species of fish. It can form massive algal blooms It makes riverbeds slippery posing a danger to waders and swimmers. Didymo blooms also pose a hazard for: hydroelectric power generation, irrigation and recreational water usage. And finally it is a tremendous thread to fish in rivers and creeks.

So far it the South Island is the only region in the Southern Hemisphere affected by rock snot.