• Attach the tape measure to the peg and lay it out taut for a distance of 10 metres (or 5 x the stream width, whichever is the smaller). Attach the upstream end of the tape to a second peg.
• Divide the distance along the tape into thirds and mark the tape (i.e., 3.3-m intervals for a 10 m site distance).
• Attach the 20-m tape measure to a third peg at the location of the reference peg and
unwind the tape across the stream at right angles to the main tape. Anchor the tape on the far bank with the fourth peg.
• Divide the width of the stream (water's edge to water's edge) into 5 equally spaced
points.
• Working from the downstream end of the site, move out to the first point across the
first transect to be sampled (this will be near the water's edge on one side of the
stream). Bend down to lightly touch the bed sediments without looking at what is
there. Ideally, pick up the first stone that you touch. Because the stones need to be a
reasonable size to provide useful information sometimes you will have to disregard the initial piece of sediment that you touch if it is very small (e.g., gravel or sand) and pick up a stone no more than 10 cm away which is bigger than about 4 cm across.
• If the stream bottom is gravel, sand or silt, take a scooped sample at the sampling point with the tea strainer.
• Examine each stone carefully and identify the categories of periphyton present according to their colour and thickness using the periphyton field identification chart in
Appendix 3. Estimate the percentage cover of the stone in each category (+ 5%) and
enter this on the field data sheet reproduced on the next page.
• Complete the transect then move the tape upstream for the second transect at one-third interval and repeat the recordings.
• When complete, calculate the mean percentage cover of sampling points for each
category of periphyton. You can also use the table shown below the sampling form to
calculate an overall score for the sampling
• Hold the glass bowl on the surface of the water to obtain a clear view of the stream bed