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Comparison of three macroinvertebrate sampling methods for use in assessment of water quality changes in flashy urban streams.
Citation:
Yeardley, R., S. Jacobs, K. Fritz, AND W. Thoeny. Comparison of three macroinvertebrate sampling methods for use in assessment of water quality changes in flashy urban streams. Joint Aquatic Sciences Meeting 2022, Grand Rapids, MI, May 14 - 20, 2022.
Impact/Purpose:
The USEPA and other local and state organizations are involved in urban stream restoration and/or green infrastructure projects that affect stream water quality. Measuring success of such projects involves measuring water quality before and after restoration. A widely used, established means of assessing water quality through bioassessment of macroinvertebrate communities. However, many of the widely used sampling methods, such as nets and fixed-area grab samplers (Hess, Surber) require significant stream flow to be effective. Many urban streams have a flashy flow regime, with these streams existing as a series of pools for much of the year, interspersed with flooding events. We evaluated 3 sampling methods (modified Hester-Dendy, gravel tray, and bucket grab samplers) with respect to 3 criteria, to see which had the most promise to fill this methods gap for bioassessment of flashy urban streams. The bucket grab sampler clearly performed best with respect to all 3 criteria. The results of this work will be of interest to partners in local, state, and regional governments (including the Ohio EPA) as well as non-governmental organizations, which have a need to monitor stream water quality on an ongoing or project-related basis.
Description:
There are a number of macroinvertebrate sampling methods used to sample streams. Those most commonly used, such as nets, fixed-area grab samplers (Hess, Surber), and deployed samplers (Hester-Dendy, gravel tray), work well in perennial streams with a relatively constant flow. One of the multiple stressors that can affect urban streams is the flow regime. Flashy urban streams, which are ephemeral or intermittent, pose unique sampling challenges due to hydrological conditions that result in these streams existing as a series of isolated pools for much of the year, interspersed with spates that scour and deposit large amounts of sediment. We examined three sampling methods -a modified Hester-Dendy, a gravel tray, and a bucket method - for their potential use in bioassessment to measure changes in water quality associated with daylighting of a culvert on Congress Run, a flashy urban stream that is a tributary to the Mill Creek in Cincinnati, Ohio. Method efficacy was measured using three criteria: usability (level of effort and recoverability of samplers), variability, and retrieval of the stream macroinvertebrate community. The bucket method performed best with respect to all three criteria. The bucket method had the best usability; it required the lowest level of effort and had the highest sampler recovery. The bucket sampler had the lowest variability for most metrics, including the critical metric of taxa richness, with a coefficient of variation (CV) of 19.8%. The HD and tray samplers had taxa richness CVs of 39.2% and 53.9%, respectively. The bucket sampler performed best with respect to retrieval of the stream macroinvertebrate community. For example, the total number of taxa collected from all the replicate bucket samples (41) was greater than that collected by the HD and tray samplers combined (27). The bucket method also collected a higher average number per sample for total taxa than the other methods, and a higher number of chironomid taxa than the tray method. Multivariate analyses (Non-metric Multidimensional Scaling (NMS) and Multi-Response Permutation Procedure (MRPP)) showed significant differences in the assemblages between methods and locations (above and below the culvert).
