3.1 Effect of sampling day, sampling position, and environment
There was a significant relationship between sampling day and both
species (F = 5.933, p-value = <0.001, ndf (numerator degrees
of freedom) = 4.055, ddf (denominator degrees of freedom) = 90.945,
R-sq. (adj.) = 0.336) and OTU (F = 2.765, p-value = 0.030, ndf = 3.32,
ddf = 91.68, R-sq. (adj.) = 0.103) richness. In contrast, neither
temperature, discharge, nor sampling position had an effect on the
number of species or OTUs detected. Highest species and OTU richness was
detected in spring with lowest richness in the summer months for all
three sampling positions (Figure 2 and Figure S3). The vast majority of
macroinvertebrate species was detected at all three sampling positions
(280), also with over 99% of the reads assigned to these (Figure 2).
Although some species were exclusively found at one of the three
sampling positions, relative occurrence of these species was low in
contrast to shared species (Figure S4). We found no significant
differences between surface, riverbed or riverbank samples based on OTU
richness (Kruskal-Wallis rank sum test: chi-squared = 0.085, p-value =
0.957, ndf = 2, ddf = 97).