Protecting freshwater from algal blooms

David Hamilton


… algal blooms… can cause intense sickness in humans and severely affect water quality.”

Professor David Hamilton, BoP Regional Council Chair in Lakes Management and Restoration

Blue-green algal blooms are an increasing problem in lakes around the world. Known as planktonic cyanobacteria, the causes of blue-green algal blooms and why they produce high levels of toxins when they mass together, is unknown. Contact with the blooms through activities such as swimming can cause severe illness in humans but also affects a wide range of fish and aquatic life.

"It's when you get this type of algae clustered together, usually along the shoreline where currents or other activity has pushed them, that they start producing toxins at very high levels," says Professor David Hamilton from the University of Waikato's Environmental Research Institute.

"So while algal blooms in the middle of the lake might not cause too many problems, along the shore it can cause intense sickness in humans and severely affect water quality."

Two suspected causes of cyanobacteria blooms are nutrient run-off from intensive land use such as farming, and climate change. Professor Hamilton and his project team, including Dr Susie Wood from the Cawthron Institute in Nelson, hopes a new research project will identify both the causes of bluegreen algal blooms and the relationship between bloom density and toxin production. The project, with $920,000 funding from the Royal Society of New Zealand's Marsden Fund, is an international collaboration with scientists also studying freshwater lakes in China and Singapore.

"While the focus in New Zealand has been on the Rotorua lakes, there are many freshwater lakes around the world that have this problem and it seems to be getting worse," Professor Hamilton says. "If we can understand what causes these blooms and why they become so toxic, we should be able to not just manage them but to prevent toxin production."