Environment Southland has highlighted a rise in potentially toxic cyanobacteria—blue-green algae— in several Southland rivers, the latest being the Mataura River at Gore.
Benthic cyanobacteria usually occur as dark brown/black mats which grow attached to rocks in the river or accumulate on the surface in shallow, slow-flowing areas. Environment Southland’s freshwater & marine science leader Nick Ward urged people to "stay vigilant", as warm weather and low river flows were "prime conditions" for cyanobacteria.
Cyanobacteria can produce toxins that are harmful to people and animals if swallowed or through contact with skin, and human symptoms can include skin rashes and nausea.
The Otago Regional Council has also recently warned about the reappearance of cyanobacteria in Lake Waihola, and of other algae in the lower Cardrona River. The council also urges dog owners to be attentive of their pets near water.
