Comparing Three Types of Passive Samplers for the Assessment of Macroinvertebrates in Non-Wadeable Rivers

Passive samplers provide an alternative method for assessing macroinvertebrate communities in large streams where traditional sampling techniques may not be feasible or effective. This study was conducted to determine the effectiveness and potential biases of three passive samplers using the GA multi-metric index (MMI) as a standardized tool to compare assemblages colonizing the different devices. Nine replicates each of mesh bags filled with leaves (leaf packs), and masonite boards (Hester-Dendy samplers), and eight replicates of mesh bags filled with woody debris (snag bags), were deployed during the fall of 2014 at three sites on the Savannah River (N=26) and three sites on the Ogeechee River (N=26). After 30 days, samplers were retrieved and macroinvertebrate assemblages were assessed for differences in: Richness (EPT Taxa, Diptera Taxa), Composition (%EPT, %Trichoptera), Tolerance (Hilsenhoff Biotic Index), Functional Feeding Group Structure (Predator Taxa), and Habit (Clinger Taxa). Differences in macroinvertebrate assemblages collected were minimal between the samplers, with each substrate-type scoring similarly in most metrics. However, there were slight differences in scores for one of the Richness metrics (Diptera taxa). Furthermore, the GA MMI had similarly high scores for all samplers at both river basins. Our study suggests that all three devices provide efficient means for sampling macroinvertebrates in large Coastal Plain rivers.