3.3 Functional feeding groups
Of the 505 detected species, we were able to assign trait values to 477
(94%), with 323 assigned at the species-level, 106 at the genus-level,
and 48 assigned via gap-filling. The resulting trait data encompassed
ten total FFG of: active filter feeders (aff: 66 species), gatherers
(gat: 345), grazers (gra: 228), miners (min: 9), others (25), parasites
(par: 7), passive filter feeders (pff: 31), predators (pre: 149),
shredders (shr: 120) and xylophagous feeders (xyl: 8). Sampling day
affected the relative proportion of shredders (Chi-squared = 38.111,
p-value = <0.001, ndf = 3.78, ddf = 308.152) and parasites
(Chi-squared = 14.2, p-value = 0.007, ndf = 3.187, ddf = 308.152), with
no effects on the other FFGs. The relative proportion of shredder
species increased from summer 2017 to winter from 6 % to 15 % and
declined then again towards summer, reaching <5 % in summer
2018 (Figure 5A). Parasites showed a drop in relative proportion from 2
% in summer 2017 to <1 % in autumn and winter with many
timepoints having no parasites detected at all. After winter relative
proportion increased again to 3 % in summer 2018 (Figure 5B).