A swarm of lion’s mane jellyfish have invaded Tauranga Harbour, but Toi Ohomai marine expert Dave Guccione assures the public there is minimal risk.

“Their tentacles are not long thick enough to affect the skin,” he said.

“But they may make your lips feel like you are eating hot sauce.”

The danger level is not serious, and swimmers and boat owners should be able to move this species aside without any significant concerns, he said.

“They can give you a little tingle.”

It is a different type of jellyfish than bluebottles that can cause intense pain, redness, tingling, numbness, or a burning sensation.

Similar outbreaks of lion’s mane jellyfish existed until the 2009 and 2010 summer seasons, but they stopped appearing suddenly, Guccione said.

According to Guccione, the jellyfish’s return could be explained by the “autumn period” the harbour witnessed during the Covid-19 lockdown.

“No boat traffic, and also no building going on in the area, and so much, much less sediment going into the harbour,” he said

“The harbour was allowed to rest.”

There was a huge resurgence of eelgrass, which provides foraging and sheltering areas for younger fish and invertebrates, Guccione said.

“It’s been a lot of ecological domino effects that have gone on,” he said.

“This may be something that took this long to come back.”

Other species had been present in the Tauranga Harbour, including moon jellyfish, which are taking advantage of a plume of plankton, according to Guccione.

“It is a return to what was almost normal,” he said.

The jellyfish first arrived four weeks ago and can pose a serious risk to boat owners, Tauranga Bridge Marina manager Tony Arnold said.

“They can get the water intake and overheat engines,” he said.

They must have their engine temperature alarms working because if they enter the water intake, they can “fry the engine”.