Opposition to Port Otago's plan to dredge the Otago Harbour channel and dump 7.2 million cu m of sand and silt 6.5km beyond Taiaroa Head is emerging, with a public meeting on Monday to increase public awareness of the issue.
Friends of the Otago Harbour organiser Dr Richard Reeve, who also opposed wind-farm development in Otago, said there was concern the dredging would "radically change" the underwater environment.
The sediment plume would stretch kilometres from where it was deposited, he said.
"The proposal is the largest and most intensive single dredging programme that the harbour has seen in its history, and the wider environmental effects are as yet not wholly understood."
Port Otago announced plans in February to deepen its shipping channel by 2m to 15m, future-proofing the port to allow it to remain viable for major shipping lines.
The project requires resource consent from the Otago Regional Council, with submissions closing on August 13.
The meeting, to be held at the Skeggs Gallery, in Dunedin Municipal Chambers at 6pm, will be chaired by Dunedin city councillor Fliss Butcher.
Panelists include Green Party co-leader Metiria Turei, marine biology researcher Dr Chris Hepburn, and Southern Clams director Roger Belton.
Dr Reeve said Port Otago had been invited to send a representative, but chief executive Geoff Plunket said last night attending would be "not appropriate". If people had questions about the issue they were welcome to approach Port Otago, he said.
Port Otago was not a panelist, so the invitation was "not official".
Dr Reeve said he was concerned the dredging could have effects on animals "all down the food chain".
"No-one really knows what the impact is going to be."
While Port Otago had consulted organisations on the issue, many members of the public were not aware of the project.
The public meeting would be non-partisan, he said.
