Effects of sample storage and mechanical blending on the quantitative analysis of river perighyton

SUMMARY1. Laboratory experiments to test the effects of storage of periphyton samples, at 4°C in the dark, on levels of chlorophyllaand alkaline phosphatase activity (APA) are described. It is concluded that either raw or ethanol extracted samples may be stored for 2–3 days for chlorophyll analyses, but APA should be estimated as soon as possible. 2. Experiments are also described on the efficiency of mechanical blending of periphyton samples in breaking up clumps of periphyton cells to improve subsampling reproducibility. It is concluded that blending is a useful procedure to improve the accuracy of periphyton analyses because the subsampling coefficients of variation decreased for most determinands after blending.