2.3 | Sampling and sample processing
Benthic invertebrates were collected using a kick net with a 25x25 cm
frame and a mesh size of 0.25 mm. For each sample, an area of
approximately 0.5 m2 was covered with a sampling
duration of one minute. At each combination of sampling occasion and
sampling station, five replicate samples were taken. The samples were
preserved in 96% ethanol before subsequent subsampling of each sample
(1/10) in the laboratory. All invertebrates in the subsample were sorted
and identified to the lowest possible taxonomic unit using a stereo
microscope and following Engblom (1996) for Ephemeroptera, Lillehammer
(1988) for Plecoptera, Rinne & Wiberg-Larsen (2017) for Trichoptera,
Holmen (1987) and Nilsson & Holmen (1995) for Coleoptera and Glöer
(2002) for Gastropoda. The number of specimens from the sub sample were
then multiplied by 10. All specimens of the remaining sample that
differed morphologically from the specimens in the sub sample, were
picked out, identified to lowest possible taxon and counted.