Didymo in New Zealand
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__NOTOC__ In 2004 '' Didymosphenia geminata'', a diatom commonly known as didymo or rock snot, was discovered in
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
, the first time it was found in the Southern Hemisphere. To restrict its spread, the whole of the South Island of New Zealand was declared a controlled area in December 2005. 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. Biosecurity New Zealand working with Environment Southland, AgriQuality and Fish and Game New Zealand launched an extensive public awareness campaign to encourage river users to clean their equipment after use in affected waterways. This campaign was highly successful, with 99% of freshwater users surveyed in 2008 in the South Island being aware of didymo.


Adverse effects

Didymo can have a notable impact on the insects that are a food source for many species of fish. It can form massive
algal bloom An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems. It is often recognized by the discoloration in the water from the algae's pigments. The term ''algae'' encompass ...
s. 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. Didymo clogs domestic drinking water filters.


Spread

In October 2004, an unusual algal growth was found in the lower Waiau River in
Southland Southland may refer to: Places Canada * Dunbar–Southlands, Vancouver, British Columbia New Zealand * Southland Region, a region of New Zealand * Southland County, a former New Zealand county * Southland District, part of the wider Southland Re ...
. The
National Institute of Water and Atmospheric Research The National Institute of Water and Atmospheric Research or NIWA ( mi, Taihoro Nukurangi), is a Crown Research Institute of New Zealand. Established in 1992, NIWA conducts research across a broad range of disciplines in the environmental scien ...
identified the algae as ''Didymosphenia geminata'' and confirmed that it is New Zealand's first documented detection. In October 2005, populations of didymo were discovered in the Hawea, Buller, Ōreti and Upper Clutha rivers. Delimiting testing is being undertaken in North Island waterways and other South Island river systems to find out how far didymo has spread in New Zealand. In October 2007, dead didymo cells were found in routine water samples from the
Whanganui Whanganui (; ), also spelled Wanganui, is a city in the Manawatū-Whanganui region of New Zealand. The city is located on the west coast of the North Island at the mouth of the Whanganui River, New Zealand's longest navigable waterway. Whang ...
,
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,
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rivers, and the Mangatepopo Stream in the central North Island, with MAF suspecting further contamination. In October 2009, didymo was detected in the Upper
Rangitata River The Rangitata River is one of the braided rivers that helped form the Canterbury Plains in southern New Zealand. It flows southeast for from the Southern Alps, entering the Pacific Ocean northeast of Timaru. The river has a catchment area of , ...
in Canterbury. The Upper Rangitata River is known as one of the most important braided river habitats for the endangered black-fronted tern, the
wrybill The wrybill or (in Māori) ngutuparore (''Anarhynchus frontalis'') is a species of plover endemic to New Zealand. It is the only species of bird in the world with a beak that is bent sideways in one direction, always to the right (in the crossbil ...
and the endangered upland longjawed galaxias. In February 2010, didymo was detected in the
Waimakariri River The Waimakariri River is one of the largest rivers in Canterbury, on the eastern coast of New Zealand's South Island. It flows for in a generally southeastward direction from the Southern Alps across the Canterbury Plains to the Pacific Ocean. ...
. In May 2010, didymo was detected in the Riuwaka River, the Pearse River and the Maruia River in the Nelson-Tasman region in the top of the South Island.


Preventing the spread

The following methods are recommended by MAF Biosecurity New Zealand to prevent the spread of didymo in New Zealand: Check: Before leaving the river, remove all obvious clumps of algae and look for hidden clumps. Leave them at the site. If you find clumps later don't wash them down the drain, treat them with the approved methods below, dry them and put them in a rubbish bin. Clean: Soak and scrub all items for at least one minute in either hot (60°C) water, a 2% solution of household bleach or a 5% solution of salt, antiseptic hand cleaner or dishwashing detergent. Dry: If cleaning is not practical (e.g. livestock, pets), after the item is completely dry wait an additional 48 hours before contact or use in any other waterway.


See also

*
Invasive species in New Zealand A number of introduced species, some of which have become invasive species, have been added to New Zealand's native flora and fauna. Both deliberate and accidental introductions have been made from the time of the first human settlement, with sev ...
*
Conservation in New Zealand Conservation in New Zealand has a history associated with both Māori and Europeans. Both groups of people caused a loss of species and both altered their behaviour to a degree after realising their effect on indigenous flora and fauna. Protected ...


References

{{Reflist, 2


External links



at Ministry for Primary Industries
Didymo page
at the Department of Conservation (New Zealand), Department of Conservation Nature conservation in New Zealand Invasive plant species in New Zealand