TRC duo make slimy chore a breeze

19:14, Sep 03 2012
Alex Connelly
SCRAPING THE SLIME: Taranaki Regional Council scientific officer Scott Cowperthwaite hard at work with his invention.

Faced with the job of manually scraping slime off more than 200 rocks, two Taranaki scientists invented a machine to make the task easier.

Studying the amount of periphyton, a slimy alga, on rocks is one way to check the health of a stream. Some periphyton is good, organisms feed off it, but too much is not a good sign.

So every year, Taranaki Regional Council scientific officers Alex Connelly and Scott Cowperthwaite visit 21 sites at 11 rivers around the region and scrape the slimy stuff off 10 rocks at each site.

It is a tiring, not to mention tedious, job.

They decided there had to be a better way. They thought somewhere, surely, there would be a machine that could do it for them. There wasn't, so they invented one. Using the machine - nicknamed PBS for periphyton biomass sampler - saves them an hour at each site. It also makes the testing more accurate.

The scientific protocol around slime scraping is to draw a circle on a rock and scrape inside the circle with a little brush. This is to ensure the same-size sample is taken on every rock. Once scraped, water is poured over the circle and the slime runs off the rock into a pottle. This can be inaccurate because the scientist can go over lines or the water can wash slime off the rock outside the circle.


Their new machine, which sits in a "common or garden" toolbox, solved this problem, Mr Cowperthwaite said.

A small airbed pump, with a 6-volt battery, sits in the bottom with a long tube. The rock goes in a clamp, which has a round seal, and is placed in the top of the box. The rock is scraped with a brush, water is poured over it and the pump turned on. The pump sucked the slime through the tube and into a bottle, which was later sent to the lab, he said.

"We are following the nationally adopted Niwa protocols, however, we have adopted a new sample method, which we believe is more efficient, accurate and reproducible for our monitoring purposes. This is also about people and the efficient use of resources as well as science. Our field staff are more physically comfortable and can achieve their task faster when using the PBS."

Mrs Connelly said they probably would not get a patent for their invention because there were only 10 regional councils in New Zealand that scraped slime off rocks. But she was going to get a poster printed, to put up at an upcoming freshwater conference to see if there was any interest.

Taranaki Daily News