Nearly $70,000 was spent on cleaning up sea lettuce from Tauranga shores in the past year, almost double the amount spent the year prior and more than triple the year before that.
The figures were released to the Bay of Plenty Times after the lettuce returned to Tauranga Harbour this season, prompting a collection of 800 tonnes by the Bay of Plenty Regional Council last week.
In 2015/16 the council spent $69,721 on collecting 496 tonnes of sea lettuce. The year prior it spent $35,659 collecting 350 tonnes.
Regional council technical adviser Bruce Gardner said it worked with Tauranga City and Western Bay of Plenty district councils and accessible nuisance accumulations were often found at busy beaches such as Kulim and Ferguson Parks and Ongare Pt.
''Our focus is on large sea lettuce build-ups that would otherwise pose a significant public nuisance or health risk,'' he said.
Mr Gardner said sea lettuce was present all the time but became more obvious throughout summer when it bloomed and grew large fronds.
''Sea lettuce gets ripped off the seabed by strong onshore winds or heavy seas and then gets washed up on the beaches with onshore winds.''
Mr Gardner said the lettuce produced an offensive sulphur odour so it was best to avoid disturbing it, but people could help by collecting it and using it as fertiliser or a compost supplement in gardens. The lettuce collected by the council contractors was sent away for composting.
The regular inundation of sea lettuce is a familiar sight for Matua resident Mike Hymers and his son Daniel.
The two had returned from fishing in a sea kayak on Sunday to Fergusson Park, where a thick bed of sea lettuce blankets the shoreline.
''The weed is a problem,'' Mr Hymers said.
''When you're trying to fish and the weed just gathers around your line, it gathers down and covers your bait so it's really hard to fish. It's pretty annoying.''
Mr Hymers said they came down to Fergusson Park regularly to walk to the dog.
''The dog rolls in it and walks in it, it stinks. It gets very slippery. You have to be careful where you stand. It's not pleasant.''
At Kulim Park, Heath Torrie and Paula Dennison said the sea lettuce smelled bad.
''We live on Turret Rd and it's there as well. It just turned up in the past week,'' Mr Torrie said.
''It must be offputting for visitors.''
Ms Dennison said the sea lettuce stank but it was not as bad as it was about five years ago when the stench could be smelled throughout Tauranga city.