Editorial: Prevalence of toxic algae raises alarm

Dogs as the canaries-in-the-mine for New Zealand's environment? Well, perhaps not quite - owners are not deliberately sending their pets into rivers in order to test the toxicity of our waterways. However, at least 50 dogs around New Zealand are known to have died after ingesting cyanobacteria, an algae named for its blue-green appearance rather than cyanide-like toxicity. Several recent cases have involved dogs swimming in the Waimea and Maitai rivers in this region.

As tragic as those deaths will be for loving owners, the greater fear is that a child might be next to swallow a dangerous dose of the potentially deadly substance - rated as among the most lethal naturally occurring toxins that members of the public could encounter. Swallowing just a gram or two of the algae could be sufficient to kill a small dog within a few minutes, according to Susie Wood, one of the world's foremost experts on cyanobacteria.

Dr Wood, a scientist at Nelson's Cawthron Institute, says no cases of human poisonings involving the toxin have been recorded in this area. However, the risk is significant and growing. Clearly, it is one more environmental hazard that we must take seriously.

Some of this region's most popular waterways are known to have increasing levels of the algae. The Takaka, Lud and Motueka rivers are also on the list along with the Maitai and the Waimea.

River recreational use soars over summer, obviously, and the blooms seem to thrive in warm, settled weather. The longer the gap between rainfalls heavy enough to "flush" the algae out of our rivers, the greater its incidence. Its increasing presence will be one of the consequences of predicted changing weather patters - warmer temperatures and less summer rain.

Interestingly, Dr Wood says the algae does not thrive in New Zealand's most polluted rivers, as it does best in water that is low in phosphorus. However, it does seem to prefer otherwise "clean" rivers in which nitrogen levels are rising because of more intensive land use in their catchments.

New Zealand is already acknowledged as a world leader in researching cyanobacteria. This has led to exchange visits with top scientists from France, where cyanobacteria is a serious problem. Together they are developing new methods to monitor and understand its growth and toxin production. However, Dr Wood says the approach so far has been reactive. Far better to treat the growing problem in a more proactive manner. More could be done in order to predict where and when the problems will occur - but that would take funding.

Local authorities - either regional councils or unitary ones such as Nelson and Tasman - have clear responsibilities around monitoring and protecting the waterways within their boundaries. It is also obviously a growing national and international environmental issue. Given the fuss that has been made in recent years over the invasive algae didymo - which is not known to be toxic - it is staggering sufficient funding has not been thrown at seeking ways to get on top of its lethal blue-green relative.

The Nelson Mail