Didymo in New Zealand facts for kids
Imagine a slimy, brown goo that can take over rivers! That's a good way to think about didymo, also called rock snot. Its real name is Didymosphenia geminata. Didymo is a tiny, single-celled plant called a diatom.
In 2004, didymo was found in New Zealand for the very first time. This was a big deal because it had never been seen in the Southern Hemisphere before. To stop it from spreading, the entire South Island of New Zealand was made a "controlled area" in December 2005. This meant that anything that had been in a river or lake, like boats, fishing gear, clothes, or even vehicles, had to be cleaned very carefully before going into another waterway.
Groups like Biosecurity New Zealand and Fish and Game New Zealand started a big campaign. They wanted everyone who used rivers to know about didymo and how to clean their gear. This campaign worked really well! By 2008, almost everyone (99%) in the South Island who used freshwater knew about didymo.
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What Problems Does Didymo Cause?
Didymo can cause several problems in rivers and lakes.
Harm to River Life
Didymo can grow into huge, thick mats. These mats cover the riverbed. This makes it hard for the small insects that live there to find food and sunlight. These insects are a very important food source for many types of fish. So, when didymo spreads, it can harm the fish population.
Danger for People
When didymo covers the riverbed, it makes the rocks super slippery. This can be dangerous for people who are wading or swimming in the river. It's like walking on ice!
Other Issues
Large amounts of didymo can also cause problems for things like making electricity from water (hydroelectric power). It can block pipes used for watering farms (irrigation). It also makes rivers less fun for people who want to swim, fish, or boat.
How Did Didymo Spread in New Zealand?
Didymo was first found in New Zealand in 2004.
First Discovery
In October 2004, a strange growth was seen in the lower Waiau River in Southland. Scientists from the National Institute of Water and Atmospheric Research identified it as Didymosphenia geminata. This was the first time it was officially found in New Zealand.
Spreading to More Rivers
By October 2005, didymo was found in several other rivers. These included the Hawea, Buller, Oreti, and Upper Clutha rivers. Experts started testing other rivers to see how far it had spread.
North Island Concerns
In October 2007, dead didymo cells were found in water samples from rivers in the central North Island. These included the Whanganui, Tongariro, and Whakapapa rivers. This made officials worry that didymo might be spreading there too.
Spreading in Canterbury
In October 2009, didymo was found in the Upper Rangitata River in Canterbury. This river is very important for rare birds like the black-fronted tern and the wrybill. It's also home to the endangered upland longjawed galaxias fish.
In February 2010, didymo was also found in the Waimakariri River.
Nelson-Tasman Region
By May 2010, didymo was detected in rivers in the Nelson-Tasman region. These included the Riwaka River, the Pearse River, and the Maruia River.
How to Stop Didymo from Spreading
Biosecurity New Zealand has a simple method to help stop didymo from spreading. It's called "Check, Clean, Dry."
Check Your Gear
Before you leave a river or lake, look very carefully at all your gear. Remove any clumps of algae you can see. Leave these clumps at the site where you found them. If you find more clumps later, don't wash them down a drain. Instead, treat them using the "Clean" methods below, then dry them completely, and put them in the rubbish bin.
Clean Your Gear
You need to clean everything that touched the water. Soak and scrub all items for at least one minute in one of these solutions:
- Hot water (60°C or 140°F)
- A solution of 2% household bleach (that's 2 parts bleach to 98 parts water)
- A solution of 5% salt, antiseptic hand cleaner, or dishwashing detergent
Dry Your Gear
If you can't clean something right away (like pets or livestock), you must dry it completely. After it's totally dry, wait an extra 48 hours before letting it touch any other waterway. This makes sure any didymo cells are dead.
