3.2 Mero- vs hololimnic
Sampling day affected the detection of overall merolimnic species
richness (F = 4.419, p-value = 0.005, ndf = 3.59, ddf = 27.41), but not
OTU richness, which was also true for the most species-rich merolimnic
taxon Diptera (species richness: F = 3.231, p-value = 0.021, ndf =
3.649, ddf = 27.351). For merolimnic, most species were detected in
spring (115),) and lowest richness was detected in summer (60) (Figure
S13), as well as for the most species-rich merolimnic subgroup Diptera
(spring: 95 species; summer: 50 species) (Figure S14). While the
detection of merolimnic subgroups Ephemeroptera, Plecoptera and
Trichoptera species richness was unaffected by sampling day, it had an
effect on the detection of OTU richness (E: Chi-squared = 39.11, p-value
= <0.001, ndf = 7.27, ddf = 23.73; P: Chi-squared = 21.01,
p-value = 0.005, ndf = 6.156, ddf = 24.844; T: Chi-squared = 20.11,
p-value = 0.002, ndf = 4.636, ddf = 26.364). For Ephemeroptera, most
OTUs were detected in autumn (15) and in late spring (20). In contrast,
the detected Plecoptera and Trichoptera OTU richness was highest from
December to March (10) and January to March (20) respectively (Figure
S15). Lowest numbers for all EPT were detected in summer (E: 6, P: 1, T:
6).
Sampling day had an effect on the detection of overall hololimnic
species richness (Chi-squared = 32.28, p-value = <0.001, ndf =
5.498, ddf = 25.502) but not OTU richness. Most hololimnic species were
detected between autumn and spring with relatively stable numbers
inbetween (30) (Figure S16). The detection of the most abundant
hololimnic taxon, Annelida, was influenced by sampling day for both
species (Chi-squared = 20.56, p-value = 0.004, ndf = 5.392, ddf =
25.608) and OTU richness (Chi-squared = 2.534, p-value = 0.043, ndf =
5.243, ddf = 25.757) with the highest richness detected in autumn
(species: 20/OTUs: 50) and a constant decline afterwards (summer: 5/10)
(Figure S17 and S18). The number of detected species and OTUs for the
second most abundant hololimnic taxon, Coleoptera, was not affected by
sampling day.
Temperature had no effect on the detection of species nor OTU richness
for any of the tested groups. Higher discharge negatively affected the
detection of Ephemeroptera and overall hololimnic and Annelida species
(E: Chi-squared = 4.213, p-value = 0.04, ndf = 1, ddf = 28.292;
hololimnic: Chi-squared = 6.639, p-value = 0.01, ndf = 1, ddf = 25.502;
Annelida: Chi-squared = 6.182, p-value = 0.013, ndf = 1, ddf = 25.608)
(see Figures S11, S10 and S12). Per 10 m³/s increase in discharge
Ephemeroptera lost 1 species, hololimnic taxa 5 species and Annelida 3
species.