Macroinvertebrate community responses to river impoundment at multiple spatial scales

Area of Science:

• Ecology
• Environmental Science
• Riverine Ecosystems

Background:

• River impoundment is a major global anthropogenic impact on lotic ecosystems.
• Research has focused on quantifying and managing the effects of individual large dams.

Purpose of the Study:

• To conduct a multi-scale comparison of macroinvertebrate communities downstream and upstream of water supply reservoirs.
• To identify consistent ecological responses to impoundment across spatial and temporal scales.

Main Methods:

• Analysis of macroinvertebrate community structure and indices at 80 paired downstream and control sites.
• Inclusion of spatial (regional, national) and temporal (seasonal) variables in the analysis.
• Utilized a spatially extensive, multi-year dataset.

Main Results:

• Significant differences in macroinvertebrate community structure and taxa richness were observed at larger spatial scales downstream of reservoirs.
• Regional scale showed the most significant effect, with biogeographical factors driving national-scale differences.
• Reservoirs dampened seasonal community patterns, generally increasing taxonomic richness and decreasing %EPT richness downstream.

Conclusions:

• Water supply reservoirs have spatially extensive, long-term effects on instream macroinvertebrate communities.
• Biomonitoring indices are sensitive to river regulation, aiding in management.
• Findings provide a basis for implementing mitigation measures for impounded rivers.