Macroinvertebrate Monitoring in the National Capital Region Network: Summary Report 2019–2022

Hilderbrand, Robert

doi:10.36967/2318683

I synthesized and analyzed data from the National Park Service, National Capital Region Inventory and Monitoring Network (NCRN I&M) database for stream biota monitoring collected between 2019 and 2022. I assessed the ecological condition of streams and changes through time using the benthic macroinvertebrate data to calculate the Maryland Benthic Index of Biotic Integrity (BIBI) and its associated metrics. I also explored the BIBI and benthic macroinvertebrate community data for linkages to watershed attributes and human influences to better inform management. I analyzed water quality and steam physical habitat data such that each stream’s attributes were placed in the context of peer streams having similar land use, size, and geographic region. Ecological condition and community structure are strongly tied to levels of watershed protection and disturbance. As watershed impervious surface cover (ISC) or population density increased, ecological condition decreased. Conversely, ecological condition increased as either the percentage of NPS ownership or the percentage of the watershed that is protected increased. Patterns in benthic macroinvertebrate community structure were clearly evident when these same variables were analyzed using ordination plots. The results highlight the importance of watershed protection to limit stream degradation. Most streams in the National Capital Region Network rate as ecologically “poor or very poor” on the BIBI and are likely influenced by the human activities in most of the watersheds. While their overall condition is degraded, when compared against peer streams of similar size, urbanization levels, and geography that are not protected by NPS status, many NPS streams rank in the upper 25% for the BIBI, its component metrics, and stream physical habitat attributes. Thus, many NCRN I&M streams may be degraded by the surrounding human landscape, but they fare better than their peers under similar settings. The ecological condition of many streams has declined in the most recent round of sampling compared to previous rounds. Some of the degradation may be attributed to a methods change implemented to capture more aquatic biodiversity and the necessary estimation of condition to make the results more compatible with prior monitoring. A better understanding of trends will be more evident with the next round of monitoring. There is variation in the responses both within and across streams and parks and no discernable geographic trends. Brief synopses for streams in each park are provided for more detail.

Macroinvertebrate Monitoring in the National Capital Region Network: Summary Report 2019–2022

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