He said hundreds of pieces of mussel rope had already washed up on the island's beaches this year from faraway mussel farms, and the problem would get worse if there was a farm right next to it.
"There is a fair portion of [the nets] which will be sinking and going into the seabed," he added.
The deputy chair of Ngāi Tai ki Tāmaki Tribal Trust, Laurie Beamish, rejected the suggestion the mussel farm would hurt the environment.
"Ngāi Tai ki Tāmaki are taking a long term view towards the improvement of the mauri of the Hauraki Gulf," he said, adding that mussel stocks in the Hauraki Gulf had been suffering, and the farm was an opportunity to bring sustainable kai to the table.
An Auckland Council report prepared ahead of the resource consent hearing on 4 and 5 August said the project would have minimal effects on coastal ecology and recommends resource consent be granted subject to conditions.
- RNZ