Elevated temperatures and nutrient levels are creating conditions associated with an increased risk of a toxic algal bloom on North Shore’s Lake Pupuke.
While no toxic algae have yet been seen, this could rapidly change as temperatures continue to increase.
To get the jump on a potential change, Auckland Council’s Healthy Waters team has applied for resource consent to be able to drop flocculants into the lake at short notice to disperse a bloom should one occur.
This is not the first year the lake has fallen foul to the bloom; the problem has reoccurred every year since 2014, impacting the use of the lake. Water is monitored regularly and is currently safe to swim in.
Algal blooms a natural process
Algal blooms are a natural process. They increase in warmer weather when nutrient levels increase, causing the lake to turn a murky brown and release an offensive smell.
While this is not unusual for an urban lake, Lake Pupuke’s impressive depth, combined with a lack of feeding or draining waterways, creates a ‘sink’ effect that adds to its complex nature.
Auckland Council scientists are nearing the end of a years-long investigation into the causes of these issues and will soon begin testing long-term solutions.
Councillor pleased by monitoring and evaluation
North Shore Councillor Richard Hills is pleased to see the increased effort by the council's Healthy Waters and RIMU (Research and Evaluation) teams to monitor the lake and investigate potential solutions.
“Lake Pupuke is a favourite recreational spot for North Shore residents so it’s devastating to see the effect the current climate is having on the condition of the lake," Cr Hills says.
"I want to thank the teams for their dedication to improving its health and working to restore it.
“Like many Shore residents I’ve enjoyed swimming at Lake Pupuke over past summers, especially when I was at school. I am committed to improving our water quality and ensuring the teams have the funding and resources they need to tackle the complex issues not only here but across our waterways on the North Shore.”
Targeted research underway
Auckland Council is conducting targeted research and monitoring to assess risk levels and investigae potential mitigation measures. The use of flocculants is currently the most promising short-term solution.