Figure legends
Figure 1. Overview map of the three study sites. White dots show the
water releases of the hydropower plant (KUB) and of the retention basins
(KWO and KLL). HP and RF reaches are identified with white and yellow
rectangles, respectively. White arrows show the flow direction. Source
background Orthophotos: Swissimage © Swisstopo.
Figure 2. Experimental setup. (a) Schematic sampling design for HP (top
panel) and RF reaches (bottom panel). (b) Chronological sampling
illustrated as example of the three HP scenarios (SC1, SC2, SC3) at day
one in the HP reach of the Sitter. Drift samples were collected
separately at base flow (B) and during each HP phase: up-ramping (UR),
first and second peak (P1, P2), down-ramping (DR). (c) HP scenarios.
Water level (blue solid line) and water temperature (red solid line)
measured in the HP reaches as well as water temperature measured in the
RF reaches (red dotted line). Grey squares indicate sampling period at
day one and two. Please note different scales on y-axes.
Figure 3. Drift intensity (ind./m2min)
across all reaches (‘ALL’) and separated by reach. RF: residual flow
reach; B: base flow; HP: during hydropeaking (i.e., entire HP scenario:
UR, P1, P2 and DR phase). Boxplots show the 25th and
75th percentiles, median (solid line in the box), mean
(dashed line in the box), whiskers (10th and
90th percentiles) and outliers (white dots). Numbers
indicate the sample size, whereas letters show group affiliation
according to post hoc tests with Bonferroni correction.
Figure 4. Relationship between drift intensity
(ind./m2min) and stranding density
(ind./m2) based on linear regression models across all
three HP reaches (‘ALL’) and separated by reach (Sitter: black square;
Hasliaare: dark grey circle; Linth: light grey triangle). (a) Drift data
of an entire HP scenario: UR, P1, P2 and DR phase. (b) Only drift data
of the UR phase. Solid lines: linear regressions; dashed black lines in
the left plots: 95% confidence intervals. To better meet assumptions of
normality and homogeneity of variances, all data were log transformed
(X+1) prior to computing regressions. Although, in (b) the data for
‘ALL’ and Hasliaare are not normally distributed. R: coefficient
of multiple correlation.
Figure 5. Biplot of Canonical Correspondence Analysis (CCA) based
on (a) drift propensity and (b) stranding propensity ofthe most common taxa in the
three HP reaches. Left panels: confidence ellipses (95% confidence
limit, standard deviation) are fitted on the CCA plots to depict
differences between river reaches. Right panels: distribution of the
species scores of the most common taxa (the larger the circle the higher
the propensity). Asterisks indicate taxa with abundances >
1% in the drift/stranding but not in the benthic samples (Appendix C in
Data S1). Factor fitting shows the statistical differences in
drift/stranding propensity between HP reaches (Sitter vs Hasliaare vs
Linth), sampling day (day 1 vs day 2) and HP scenario (SC 1 vs SC2 vs
SC3). Significance levels: *0.05, **0.01, ***0.001.
Figure 6. Benthic density (ind./m2)
across all three RF respectively all three HP reaches(‘ALL_RF’, ‘ALL_HP’) and
separated by reach. Numbers
indicate the sample size, whereas letters show group affiliation
according to Mann-Whitney tests.
Figure 7. NMDS ordination of the three RF and three HP reaches based on
benthic densities (ind./m2) of the most common taxa
(relative abundance > 1%,
Appendix C in Data S1). 95%
confidence ellipses of the standard deviations of site scores of the
three rivers (Sitter, Hasliaare, Linth) within the two respective
reaches (RF: solid ellipses; HP: dashed ellipses) are depicted. Taxa
that most contributed to dissimilarity (p < 0.05) are fitted
on the NMDS plot and indicated with black dots and taxon
name.
Figure 8. Benthic density (ind./m2)
across all three RF respectively all three HP reaches separated by the
two traits ‘interstitial/surface’ and ‘lentic/lotic’. Numbers indicate
the sample size, whereas letters show group affiliation according to
Mann-Whitney tests.