Oral Presentation Society for Freshwater Science 2025 Annual Meeting

Local and Downstream Macroinvertebrate Responses: Are Functional Metrics More Sensitive Than Structural Ones To Ecological Change Across Land Uses, Management Practices and Regions? (118379)

Sergio A Sabat-Bonilla 1 , Kelly O Maloney 2 , Greg Noe 3 , Sally E Entrekin 1
  1. Entomology Department, Virginia Tech, Blacksburg, VA, USA
  2. Leetown Science Center, U.S. Geological Survey's (USGS), Kearneysville, WV, USA
  3. Florence Bascom Geoscience Center, U.S. Geological Survey's (USGS), Reston, VA, USA

Reports of fluctuating aquatic macroinvertebrate populations point to climate, land‐use changes, and methodological factors—especially habitat conversion—as key drivers of global trends and stream health. Management practices (MPs) have been widely implemented to mitigate in‐stream habitat degradation. Yet, our previous synthesis of 212 macroinvertebrate metrics in agricultural and urban streams revealed inconsistent outcomes—43% of metrics were positive, 19% negative, and 38% neutral—linked to region, land use, MP type and the metrics measured (Sabat‐Bonilla et al., in prep.). For example, in the Valley and Ridge, macroinvertebrate functional metrics were the strongest indicator of positive MP effects, whereas structural metrics were less responsive, tolerance metrics showed negative associations and biotic indices were unresponsive. Conversely, in the Coastal Plain, only functional metrics responded to MPs, and they were negative. We compared macroinvertebrate density (a structural measure) and biomass (a functional indicator) in 60 streams with varying agricultural influence and MP implementation across two Chesapeake Bay Watershed regions (Valley and Ridge vs. Coastal Plain). Preliminary findings in the Valley and Ridge show that low‐pasture streams with extensive MP coverage support higher taxon richness (53) but relatively low total biomass (3,705 mg/m²) and density (20,557 indiv./m²). Conversely, sites with higher pasture intensity but only low‐to‐medium MP implementation harbor fewer sensitive taxa (43–46) yet exhibit substantially greater biomass (13,500 mg/m²) and density (128,073 indiv./m²). Indicator‐species analyses confirm that a greater number of sensitive taxa (e.g., Epeorus, Micrasema, Leuctridae) biomass correlate strongly with higher MP coverage, whereas tolerant taxa prevail in pasture‐heavy catchments in both biomass and density. Moving forward, we will expand our analysis to Coastal Plain streams, evaluating how region, land‐use intensity, and MP implementation interact to shape both structural and functional macroinvertebrate metrics. This broader comparison will determine whether functional metrics consistently provide a more sensitive gauge of ecological integrity across diverse physiographic settings and disturbance gradients.