Tests on the cause of the mass die-back of toheroa on Orepuki Beach, in Southland, last month have all returned negative.
Environment Southland coastal scientist Greg Larkin said tests on shellfish samples for 30 kinds of toxins by the Cawthron Institute in Nelson had all returned negative results.
It was unlikely the toheroa had died from malnutrition or starvation, and there was no sign that they were suffering from any kind of disease or infection.
Environment Southland had sampled creeks at both ends of the beach as well as sea water in the middle of the toheroa beds, which had slightly elevated levels of nutrients, sediments and faecal coliforms, but nothing that would have killed the toheroa.
