Macroinvertebrate assemblages from a stream-wetland complex: a case study with implications for assessing restored...

Area of Science:

• Ecological restoration
• Stream ecology
• Environmental science

Background:

• Past land use has altered stream valleys into incised, single-threaded channels with impaired hydrologic functions.
• Restoration aims to re-establish floodplain and groundwater connections, potentially improving stream habitat and biological communities.
• Identifying biological indicators is crucial for assessing the success of stream restoration efforts.

Purpose of the Study:

• To identify macroinvertebrate assemblage attributes as biological indicators of improved hydrologic functions after stream-wetland restoration.
• To compare macroinvertebrate assemblages and hydrologic functions between restored and unrestored stream reaches.
• To evaluate the effectiveness of Stage 0 restoration in a headwater valley.

Main Methods:

• Monitored hydrologic functions and macroinvertebrate assemblages in restored and unrestored stream reaches over multiple years.
• Assessed metrics such as bed mobility, flow duration, macroinvertebrate density, and biomass.
• Analyzed EPT (Ephemeroptera, Plecoptera, Trichoptera) biomass and mayfly abundance.
• Identified macroinvertebrate taxa with life history attributes aligned with restored habitat conditions.

Main Results:

• The restored site exhibited reduced bed mobility and increased flow duration, indicating improved hydrologic functions.
• Aggregate macroinvertebrate metrics (density and biomass) were consistently higher in the restored site.
• EPT biomass was 3-4 times greater in restored pools, driven by higher mayfly abundance.
• Restored pools supported a distinct subassemblage of macroinvertebrate taxa adapted to improved hydrologic conditions.

Conclusions:

• Restoration of stream-wetland complexes can successfully improve hydrologic functions and support more robust macroinvertebrate assemblages.
• Macroinvertebrate assemblages, particularly mayfly abundance and overall biomass, can serve as effective biological indicators of restoration success.
• Habitat-specific sampling designs are essential for accurately assessing biological indicators in stream restoration.
• Findings can inform the development of rapid biological indicators for evaluating stream restoration outcomes.