New test results indicate the Bay of Plenty has recovered well from oil spilled from the Rena.
Results from more than 30,000 samples have so far shown that levels of PAHs (Polycyclic Aromatic Hydrocarbons) from the grounded ship's oil appeared to have dissipated in most areas of the region, the Rena Recovery organisation said today.
But scientists said there was still a "significant" amount of work to be done before any final conclusions on long-term environmental impacts could be made - and this would include more sample information to be collected from the Astrolabe Reef.
Most of the Rena still lies wrecked on the reef, where it ran aground just over a year ago before spilling about 350 tonnes of oil into the sea.
Professor Chris Battershill, who has been overseeing the recovery monitoring programme, said there were still thousands of samples expected to be collected and tested over coming months.
Species tested included tuatua, pipi, paua, kina, crabs and cockles.
"We want to be able to get a full picture of how the environment has been affected to pinpoint exactly what impacts are from the Rena grounding," Professor Battershill said.
"Shellfish are a key focus because they are one of the biggest concerns for the community.
"They are also a good indicator of water quality because they sit on the sea floor and act as a filter.
"If there are contaminants in the water, it is likely you would trace these in common shellfish."
Professor Battershill said it was important to note the results were the "first pieces in the puzzle".
"It's important to understand that we need to process a large amount of data to make a complete analysis of the situation."