A horrible stench set off an investigation into a mysterious mass shellfish death at Ngunguru Sandspit in Northland.
Aaron Franklin, who was visiting his parents in the area, alerted authorities to the deaths on Thursday May 21. The engineer estimates there were well over a million dead cockles, tuatua and pipi on the seaward beach and near the mouth of the estuary, with more on the seabed.
Franklin returned to the area the next day where representatives from Northland Regional Council were gathering samples. He says the area "reeked of rotting shellfish".
Northland District Health Board is recommending people do not take or consume shellfish from the area until the cause of the deaths is known. Signs advising the public of the incident went up on May 27.
Franklin, a member of the grassroots Arctic Methane Emergency Group, says increased levels of carbon dioxide and decreased levels of oxygen in the ocean are one possible cause of the deaths.
He says incidences of hypoxia - where oxygen levels drop so low that sealife is killed on mass in a short period of time - have increased rapidly. Ocean currents can cause carbon-dioxide rich water to move to areas with high concentrations of shellfish, where they die as they cannot expel carbon dioxide from their shells, Franklin says.