Anna Knight, of Warrington, contacted the ministry about the "sea balls" after her initial excitement about finding them at the beach turned to fear they could harm the environment.
Ms Knight said she first saw one of the sea balls when her partner Matt Sanson took a photo of one on a walk with their dog Alfie.
Her curiosity was piqued and she asked her brother, a marine ecologist, for help in identifying the green, fibrous, fluffy spheres.
He was "vaguely curious" but could not identify the species, she said.
So she turned to Google and asked around in community forums on social media, and learned the balls had washed ashore at beaches other than Warrington recently.
They had been found at Aramoana and Doctors Point as well.
And it seemed they might be "marimo balls", which were commonly found in Japan.
Ms Knight began collecting them.
"I was trying to rescue them, because I heard they were rare, and they were going to die — from my initial research, the direct sunlight was going to really cook them, and they would shrivel up and die, so I was like, they’re living things, and they’re cute, and they’re ball-shaped ... "
Her plan evolved — they could be decorated and sold as some form of fundraiser just in time for Christmas.
Soon though Ms Knight found some old news that turned her excitement into anxiety.
In 2018, in Christchurch, a botanic artist was dragged in front of the courts for selling marimo bought through the Chinese online retail site AliExpress and then sold on through Trade Me and at local markets.
And the ministry, at the time, put out a call to the public for the return of three specimens the artist had sold that remained unaccounted for.
If the exotic algae got into local waterways they could spread and smother native wildlife.
Ms Knight said she "freaked out" and contacted the ministry, eager to do the right thing.
Yesterday, to assist the ministry’s investigation she was boxing up some specimens to send to Wellington for analysis by Niwa.
Biosecurity New Zealand aquatic health team manager Mike Taylor confirmed the ministry was investigating — but he said it was unlikely the balls were marimo, or exotic.
Mr Taylor said the ministry received a notification of balls of seaweed washed up along areas of the Dunedin coast on Wednesday.
"We are in the process of identifying the seaweed.
"However, being of marine origin, these are likely to be Aegagropila, also known as sea balls or Pillae marinae.
"‘Marimo balls’, on the other hand, are of freshwater origin."
Aegagropila, generally made up of of seaweeds and other organic matter, were a common phenomenon, caused by wave action, when the seaweeds and other organic matter were torn from the sea floor and formed balls which then washed ashore.
"Biosecurity New Zealand has investigated calls about Aegagropila in the past and it is unlikely that this occurrence is an invasive species or concern to wildlife," he said.
"The balls more likely consist of native or commonly present seaweeds that are currently blooming due to warmer temperatures," he said.
