9457

• UCREFRP Catalog Number: 9457
• Author: Ptacek, J. A., D. E. Rees and W. J. Miller.
• Title: A Study of the Ecological Processes on the Fryingpan and Roaring Fork Rivers Related to Operation of Ruedi Reservoir.
• USFW Year: 2003.
• USFW - Doc Type: Fort Collins.
• Copyright Material: NO

Macroinvertebrates
Macroinvertebrate sampling and analysis were conducted at four sites in the spring of
2001 and five sites in the fall of 2001 and spring 2002. The results provided by the
applied metrics are presented in Table 5. Complete species lists are provided in
Appendix B. The results from the applied metrics provided a measure of longitudinal
changes in macroinvertebrate communities as well as a seasonal comparison. The
following section describes the range and results of the applied metrics. These results
will be further evaluated in the discussion section.
Diversity and evenness values were evaluated for each site on each sampling date. These
metrics are influenced by similar processes and often indicate similar trends. Diversity and
evenness values were used to detect changes in macroinvertebrate community structure. In
unpolluted waters diversity values typically range from near 3.0 to 4.0. In polluted waters
this value is generally less than 1.0. The evenness value ranges between 0.0 and 1.0.
Values lower than 0.3 are generally considered indicative of organic pollution (Ward et al.
2002). Diversity ranged from 2.03 to 3.80 during this study, while evenness ranged from
0.406 to 0.707. On each sampling occasion the lowest values for both metrics were
obtained at FPR-RES. Some decline in these values was also observed at RFR-C during the
spring sampling events. A comparison of diversity values between spring sampling events
indicated a similar spatial trend (Figure 36). This pattern was also observed for evenness
values (Figure 37).
Diversity and evenness values exhibited some fluctuation between sites and sampling
events, but remained within a range suggesting good or excellent water quality at most
locations. These metrics are designed to indicate different types of disturbance, and are
often used as indicators of pollution. Low values that were observed at the site below the
dam were likely a result of the restraints imposed by regulated releases from the dam.
The FBI is often used in macroinvertebrate studies as a means of detecting organic
enrichment. In this study it was useful for monitoring differences between the sites that may
Draft Final Report, Fryingpan and Roaring Fork Rivers February 12, 2003
Miller Ecological Consultants, Inc. Page 42