The Chinese owners of a floating dock which broke up in Cyclone Lusi, threatening marine life off Northland's east coast, have been ordered to clean up a chain of islands by midnight tonight.

The polystyrene-filled dock was swept away from Motukawaiti Island, part of the Cavalli group off Matauri Bay, in last month's cyclone and later smashed apart on nearby rocks.

The largest chunks have washed up on Kahangaro Island but countless polystyrene fragments have washed up on other islands, including Motukawanui, the largest of the spectacularly scenic Cavallis. Polystyrene can be fatal to seabirds, fish and marine mammals such as dolphins, which can mistake it for food.

Northland Regional Council harbourmaster Jim Lyle said the island resort's owners initially reported the dock had been blown away in the cyclone. With its whereabouts unknown it was a potential navigation hazard.


It was subsequently found broken into pieces concentrated on three to four beaches on nearby islands. Council staff travelled to the islands on April 15 and were now treating it as an environmental incident.

An abatement notice was issued last Thursday ordering the owners to clean up the islands within a week. The council was assisting them with finding contractors capable of doing the job.

Mr Lyle said the owners had been cooperative but "a bit tardy" in their efforts to remove the debris.

Former MP and now regional councillor Dover Samuels was one of the first to alert the authorities to the pollution. He was concerned that the island's Chinese owners did not seem to appreciate the Cavallis' significance to New Zealanders.

"These islands are pristine. They're not just pieces of land they've been able to acquire," he said.

Nor had the people of Matauri Bay been able to meet the owners face to face, instead having to deal with intermediaries.

Enquiries in Parliament had failed to ascertain exactly who owned the island, which is believed to have changed hands in 2010 for $11 million.

The sale is the subject of an Overseas Investment Office investigation.


Mr Samuels also had concerns about the safety of the remaining wharf at Motukawaiti Island.

Failing to comply with an abatement notice can result in fines or even legal action via the Environment Court.