Environment Southland will use emergency powers to open the Waituna Lagoon to the ocean to avoid imminent ecological harm from a growing toxic algal bloom.
Monitoring has revealed levels of cyanobacteria in the lagoon have been growing in the past month, creating a risk to the health of the ecosystem if the nationally significant lagoon east of Invercargill remains closed.
The regional council said opening it will reduce the amount of nutrients that fuel the algae.
Environment Southland’s general manager of integrated catchment management, Paul Hulse, said the council has jurisdiction but no current consent to open the lagoon as it expired in 2022.
That is why emergency powers will be used, with work starting this week.
The lagoon could remain open for several weeks.
“While there is some uncertainty as to how effective this opening will be, our belief, which is supported by interagency science opinion, and which recognises mana whenua and local community concerns, is that it is appropriate for us to take this action to seek to mitigate adverse effects on this internationally significant area,” Hulse said.
The lagoon has been closed to the sea since March 2021 but was periodically opened under a previous consent before that.
The Waituna Lagoon and wetlands were among the first sites in the world to be classified wetlands of international significance under the Ramsar Convention on Wetlands, an intergovernmental treaty signed in 1971.
The Waituna Catchment Group, representing farmers, fishermen, duck hunters, bird watchers and environmentalists, is working to improve the health of the area, which is an important habitat for birds, fish and eels and plants.