The Awarua-Waituna Wetlands near Invercargill have incredible ecological and cultural value, but, as World Wetlands Day approaches, a concerning algal bloom illustrates wetland vulnerability.

World Wetlands Day is celebrated each year on February 2. This year’s theme – Wetlands and Human Wellbeing – highlights the enormous benefits of wetlands, which provide water and food, support biodiversity, protect against extreme weather events, and store carbon.

DOC Principal Scientist and Chair of the global science panel for the Ramsar Convention Hugh Robertson says the Awarua-Waituna Wetlands’ Waituna Lagoon, which was manually opened this week to flush out the algal bloom, is a prime example of the complex challenges facing New Zealand’s globally significant wetlands.

“For 15 years, Waituna Lagoon and its surrounding catchment have benefitted from large-scale restoration efforts thanks to collaboration between Te Rūnanga o Awarua, Te Rūnanga o Ngāi Tahu, DOC, Environment Southland, Southland District Council and Fonterra as part of Whakamana Te Waituna Trust.

“Through partnership efforts, a more natural water management regime has supported the lagoon’s recovery by reducing artificial drainage of freshwater. Monitoring in 2023 showed a dramatic recovery of Ruppia – a plant that signals a healthy lagoon,” Hugh says.

“However, warmer temperatures and high nutrient levels are a dangerous combination, and the lagoon remains in a vulnerable state.”

“Poor-quality water makes restoration efforts difficult. Looking forward, nutrients such as nitrogen and phosphorus, and climate change will continue to pose a significant threat to Waituna Lagoon and New Zealand’s wetlands more generally.

“Many of New Zealand’s coastal lakes and estuaries are affected by poor water quality. They are situated at the bottom end of catchments and accumulate contaminants.

“It’s clear ongoing effort is needed to protect Waituna Lagoon so it doesn’t deteriorate, as high nutrient loads make the lagoon vulnerable to a range of harmful algal blooms,” Hugh says.

Ruby Moynihan Magsig, DOC’s Ramsar Lead says on World Wetlands Day, countries around the world will put the spotlight on wetlands and reflect on what they can do to manage them more sustainably for the benefit of everyone.

“Collective efforts that include government, Māori, landowners and communities are crucial to ensure the internationally and locally important values of New Zealand’s Ramsar sites are safeguarded, and our remaining wetlands thrive.”

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