New toxin-producing algal species found in Christchurch lake
Recent research by a University of Canterbury PhD student has identified a toxic blue-green algal species in the freshwater lakes of the Groynes recreational reserve. The blue-green alga, called Scytonema, produces a type of neurotoxin associated with paralytic shellfish poisoning. This toxin is more commonly associated with harmful algal blooms in the marine environment.
However, Environment Canterbury water quality scientists note that the algal species has been present in the Groynes lakes for many years – possibly 30 years or more. Yet to date no cases of dogs or humans suffering as a result of water contact there have been brought to the attention of the regional council or local health authorities.
Neurotoxins can concentrate in fish but recent tests found no presence of the neurotoxin in the flesh of trout collected from the Groynes. However, people should discard the internal organs of any fish caught at the Groynes.
Unlike other blue-green algae such as Phormidium, which are problematic in summer and hot, dry weather, this native species is found year-round in the Groynes lakes. Permanent health warning signs are now in place at the edges of affected water bodies. Scytonema is dark olive-green in colour and forms thick mats amongst other aquatic plants.
Scytonema has not been observed in the streams around the Groynes or in the area designated for dog walking, Environment Canterbury water quality scientists say.
The toxins produced by these blue-green algae can be harmful to humans and animals if swallowed or through contact with skin. People and dogs should avoid contact with water or algal/plant debris at the Groynes lakes. The lakes are also home to many bird species so not normally a place where people swim. The E.coli (faecal contamination) levels can be high.
Exposure to blue-green algal toxins may cause symptoms such as skin rashes, nausea, tummy upset and tingling and numbness around the mouth or tips of fingers. If you experience any of these symptoms after contact with contaminated water, visit a doctor immediately and contact Environment Canterbury. Animals that consume blue-green algae should be taken to a vet immediately.
University of Canterbury Ph.D student Francine Smith is investigating blue-green algae of the Canterbury region to understand what promotes toxin production in these microorganisms. The toxins produced by these algae have been linked to dog poisonings and deaths in the Selwyn and Ashley/Rakahuri rivers over recent summers. The identification of toxins in the alga from the Groynes lakes was unexpected.
“This is the first time that this species has been identified as a toxin producer internationally and the first confirmation of a freshwater paralytic shellfish poison producer in New Zealand,” said Ms Smith. It is likely that the blue-green alga has been present in the Groynes lakes for many years.
The research being undertaken by Ms Smith was supported by the Brian Mason Trust and the Biomolecular Interaction Centre and scholarships from ESR and Environment Canterbury. Environment Canterbury will also be supporting further research into blue-green algae toxin production in coming years.
“Toxic blue-green algae and the health risks to humans and animals from the growth of these organisms in our rivers and lakes is an important issue for Canterbury,” says Environment Canterbury investigations and monitoring director Ken Taylor.
“It is critical that we support studies that will improve our understanding of how and why the toxins are produced and how to best manage them.”
For further information, visit http://ecan.govt.nz/services/online-services/monitoring/swimming-water-quality/pages/lake-warnings.aspx
Background on blue-green algal species:
http://ecan.govt.nz/news-and-notices/news/Pages/warning-dog-owners-phormidium-algae-rivers.aspx
http://ecan.govt.nz/news-and-notices/news/Pages/phormidium-inspections-220110.aspx
http://ecan.govt.nz/services/online-services/monitoring/swimming-water-quality/Pages/river-warnings.aspx