"This is a real important part because it shows if there are any underlying effects still on going. For example, if the tuatua were affected, including their reproduction, in a couple of years the whole population could be wiped out."
The volunteers collected "cores" of sand and analysed what they found from them to determine Rena's impact. "We sift it down and ID all the little things in there like small crustacea."
Larger boxes were used to sift through sand to find shellfish and oil patties but it was still too early to find anything conclusive, Mr Culliford said.
Yesterday was the third day of the summer sampling.
The volunteers include some of the 15 students who received scholarships last month as part of the Rena Recovery programme.
Summer scholarship recipient Rex Fairweather said taking part in the monitoring programme was part and parcel of completing his polytech course. "We all have a love for the ocean and as an extension of that you want to work with that and help save the ocean and with restoration," he said.
"It's just that love, a drive of being involved.
"I think everyone found that with the Rena - where you had so many volunteers."