Benthic macroinvertebrate monitoring in Eastern Rivers and Mountains Network wadeable streams: 2014–2019 summary report

Tzilkowski, Caleb

doi:10.36967/nrr-2286761

Benthic macroinvertebrates (e.g., aquatic insects, mollusks) are one of 13 “vital signs” of ecological condition monitored by the Eastern Rivers and Mountains Network (ERMN). The network monitors these organisms in wadeable streams for two primary reasons: (1) they are essential to functioning stream ecosystems and (2) they are the most commonly used biological group for assessing and monitoring stream “health” (i.e., condition). Basic characteristics of water quality (water temperature, dissolved oxygen concentration, pH, specific conductance) and habitat are concurrently monitored because these physical attributes have substantial effects on aquatic ecosystems. This report summarizes benthic macroinvertebrate monitoring at 78 sites in wadeable streams throughout six national park units (hereafter, parks) from 2014–2019. At two parks (Delaware Water Gap National Recreation Area and New River Gorge National Park and Preserve) where wadeable streams are abundant, sites were randomly selected, which allowed for inference regarding “typical” condition of all wadeable streams within those relatively large parks. At four smaller parks (Allegheny Portage Railroad National Historic Site, Bluestone National Scenic River, Fort Necessity National Battlefield, Friendship Hill National Historic Site), non-randomly selected “index” sites were established near stream mouths or where streams flowed out of parks. The ERMN monitors benthic macroinvertebrates in three states (New Jersey, Pennsylvania, and West Virginia) and within jurisdiction of the Delaware River Basin Commission. The ERMN uses a single benthic macroinvertebrate monitoring approach, based on U.S. Geological Survey methods, for logistical advantages. To illustrate stream “health” (i.e., ecological integrity) in a regional context, I compared our monitoring results to condition benchmarks for benthic macroinvertebrate communities and water quality characteristics that were developed for use in Pennsylvania or West Virginia. Ninety-seven percent of planned benthic macroinvertebrate samples (227 of 234) were collected and identified; several samples were not collected due to safety concerns that resulted from storm damage (e.g., hazard trees) that occurred during 2018. The samples contained 72,687 benthic macroinvertebrate specimens among many taxonomic groups (167 genera and 79 families). In some instances, the composition of benthic macroinvertebrate communities confirmed existing knowledge regarding the condition of stream reaches (i.e., sections), and in many other cases, it provided the only known biological assessment of these ecologically, culturally, and recreationally valuable resources. Although the vast majority of sites were “healthy”, monitoring confirmed persistent issues at some locations, usually caused by human activities that typically originate beyond park boundaries (e.g., acidic atmospheric deposition, wastewater effluent). Continued benthic macroinvertebrate monitoring will help parks, ERMN staff, and partners maintain and improve the biological condition of an important, and currently “healthy” resource (i.e., wadeable streams) for future generations. Based on the completeness and consistency of results summarized in this report, few changes to the approach are necessary. I intend to work with network parks to discuss potential management implications and areas where additional targeted research would be beneficial. Primary findings are briefly summarized in the park-specific sections below.

Benthic macroinvertebrate monitoring in Eastern Rivers and Mountains Network wadeable streams: 2014–2019 summary report

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