Development and validation of a macroinvertebrate index of biotic integrity (IBI) for assessing urban impacts to Northern California freshwater wetlands |
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Authors: | Kevin B Lunde Vincent H Resh |
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Institution: | (1) Environmental Science, Policy, and Management, University of California, Berkeley, 130 Mulford Hall #3114, Berkeley, CA 94720, USA |
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Abstract: | Despite California policies requiring assessment of ambient wetland condition and compensatory wetland mitigations, no intensive
monitoring tools have been developed to evaluate freshwater wetlands within the state. Therefore, we developed standardized,
wadeable field methods to sample macroinvertebrate communities and evaluated 40 wetlands across Northern California to develop
a macroinvertebrate index of biotic integrity (IBI). A priori reference sites were selected with minimal urban impacts, representing
a best-attainable condition. We screened 56 macroinvertebrate metrics for inclusion in the IBI based on responsiveness to
percent urbanization. Eight final metrics were selected for inclusion in the IBI: percent three dominant taxa; scraper richness;
percent Ephemeroptera, Odonata, and Trichoptera (EOT); EOT richness; percent Tanypodinae/Chironomidae; Oligochaeta richness;
percent Coleoptera; and predator richness. The IBI (potential range 0–100) demonstrated significant discriminatory power between
the reference (mean = 69) and impacted wetlands (mean = 28). It also declined with increasing percent urbanization (R
2 = 0.53, p < 0.005) among wetlands in an independent validation dataset (n = 14). The IBI was robust in showing no significant bias with environmental gradients. This IBI is a functional tool to determine
the ecological condition at urban (stormwater and flood control ponds), as well as rural freshwater wetlands (stockponds,
seasonal wetlands, and natural ponds). Biological differences between perennial and non-perennial wetlands suggest that developing
separate indicators for these wetland types may improve applicability, although the existing data set was not sufficient for
exploring this option. |
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Keywords: | |
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