9484

• UCREFRP Catalog Number: 9484
• Author: Osmundson, D. B., V. L. Ryel, V. L. Lamarra and J. Pitlick
• Title: Flow-Sediment-Biota Relations
• USFW Year: 2002
• USFW - Doc Type: Implications for River Regulation Effects on Native Fish Abundance
• Copyright Material: YES

1730 D. B. OSMUNDSON ET AL. Ecological Applications
Vol. 12, No. 6
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FIG. 4. Interrelationships among physical and biological parameters. Solid lines represent regression lines in (a) and (b)
and 1:1 line in (c) and (d). (a) Relationship between ln(chlorophyll a biomass) and principal component score based on
physical habitat parameters; (b) relationship between ln(invertebrate biomass) and principal component score based on physical
habitat parameters; (c) predicted and measured ln(chlorophyll a biomass), regression based on principle component score
and rk location; (d) predicted and measured ln(invertebrate biomass), regression based on principle component score and
ln(chlorophyll a biomass).
brate biomass and the physical variables that charac-
terize the riverbed (Table 2). Positive correlations were
found with variables reflecting less sedimentation
(DFS, D50, void volume) and higher detrital content
and water velocity, while inverse relationships were
found with variables reflecting higher sedimentation
(percentage of embeddedness and percentage of sub-
strate <2 mm).
The high degree of correlation among physical pa-
rameters (Table 2) made it difficult to determine which
parameters most related to standing crops of primary
producers and invertebrate consumers. Hence, PCA
factor scores were used to assess relationships between
physical habitat and measures of benthic biota. Factor
scores for the first principal component for each riffle
and run were calculated using the factor loadings in
Table 3 for each sample reach and regressed against
the corresponding values for chlorophyll a and biomass
of invertebrates. Biological parameters at each sample
reach were averaged over the three sample periods. The
analysis combined riffles and runs because physical
habitat differences were included in the factor score.
Highly significant relationships were found between
both chlorophyll a (F,,66 = 57.8, P < 0.0000001, r' =
0.47) and invertebrates (F,,66 = 50.3, P < 0.0000001,
rz = 0.43) and the principal component scores (Fig. 4a,
b). Regression,relationships were improved by adding
additional variables to the regressions containing the
factor scores. Because a highly significant (F,,66 =
130.2, P < 0.0000001, r2 = 0.66) relationship was also
found between chlorophyll a and invertebrate biomass
(Fig. 5a), and longitudinal relationships were found for
both chlorophyll a and invertebrates, addition of these
elements was evaluated. By including the distance up-
stream (rk) of the Colorado and Green River conflu-
ence, the regression relationship (Fig. 4c) for chloro-
phyll a improved (F2,59 = 104.6, P < 0.00001, rz =
0.78), and the multiple regression analysis indicated no
collinearity problems (condition number = 3.11; Bel-
sley et al. 1980). The relationship also improved for
invertebrates (Fig. 4d) when chlorophyll a was includ-
ed (F265 = 69.9, P < 0.00001, r2 = 0.68); however,
when rk location was added, the resulting condition
index of 17.4 suggested collinearity problems, proba-
bly reflecting the relationship between chlorophyll a
and rk location.
Algal invertebrate biomass-fish biomass relation-
ship.-Highly significant relationships were found be-
tween fish biomass (expressed as catch rates) and chlo-
rophyll a (Fig. 5b; F1,31 = 35.2, P < 0.00001, r' =
0.53), invertebrate biomass (F13, = 26.3, P = 0.00001,
r2 = 0.46), and combined chlorophyll a and inverte-