Combining Data from Multiple Agencies to Assess Benthic Macroinvertebrate Communities in a Large Gravel-Bed River

Government agencies frequently conduct benthic macroinvertebrate surveys for bioassessment at large spatial scales in a variety of aquatic habitats, including large rivers. However, these data are rarely used by investigators outside the specific regulatory agency. We used data from 150 benthic macroinvertebrate samples collected over a period of 20 y from 10 locations in a large, shallow river system (the Susquehanna River and 2 major tributaries) by personnel in 4 government agencies to explore broad spatial and temporal patterns in benthic assemblages. We standardized sample size and taxonomy to account for differences in sampling, processing, and identification methods among agencies. Invertebrate assemblages were dominated by mayflies and caddisflies (46-83%). Percent Ephemeroptera, Plecoptera, Trichoptera (EPT) and standard diversity measures were inversely correlated, indicating that traditional macroinvertebrate Index of Biotic Integrity (IBI) approaches might not be applicable to large rivers. These data showed differences in assemblage composition across sub-basins and revealed effects of the spread of invasive Asian clams and of black fly management on benthic assemblage structure in the river. Large-river invertebrates are understudied and, even with challenges of combining data sets from multiple agencies, we showed the potential utility of applying data from a large river system to reveal ecological patterns across space and time.