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...a rapid assessment procedure that was used to assess the environmental quality of large and great river ecosystems in the state. The reference condition was based on 275 sites that were representative of the Wabash River, but were not pristine or least-impacted. These sites were not randomly chosen, but met specific least-impacted criteria to develop the IBI. We used another 36 sites exposed to point-source discharges to test the index. Prior to sampling, sites were classified as "least-impacted" or as affected by point source pollution from industrial discharges. Of the 24 potential IBI metrics considered, 12 metrics were chosen based on statistical relevance for large and great rivers. For the test subset, the least-impacted sites had significantly higher mean scores and lower temporal variation than the point-source site classification, showing they possessed the best ecosystem quality. Point-source sites had the lowest means and most variable scores, signifying degraded ecosystem quality. Least-impacted sites had the highest IBI scores and the lowest variability, while representative sites typical of agricultural land uses had slightly but not significantly worse scores. Regional estimates of stream conditions showed that 42% of the stream reaches in the Interior River Lowland ecoregion had fish assemblages in poor or fair ecological condition, while large-river reaches in the Eastern Corn Belt Plain ecoregion had 36% fair and 23% good.
Keywords: Biological integrity, reference condition, IBI, Interior River Lowland, Eastern Corn Belt Plain
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The index of biological integrity (IBI) is a multimetric index that integrates structure, composition, trophic ecology, and reproductive attributes of fish assemblages at multiple levels of ecological organization (Karr 1981; Karr et al. 1986; Simon & Lyons 1995; Simon 1999). Indices of biological integrity can be viewed as a family of indices for rating the health of an aquatic ecosystem (Simon 2001). These indices provide a valuable framework for assessing the status and evaluating the restoration of aquatic communities (Fausch et al. 1990; Karr & Chu 1999; Simon et al. 2003). Standard procedures are used to compare existing biological conditions in order to assess the current status of the biota.
Indices of biotic integrity have been widely based on fish assemblages in "wadeable" streams, but applications to large and great warm water rivers are few (Simon & Lyons 1995; Hughes & Oberdorff 1999; Emery et al. 2003). Simon & Stahl (1998) calibrated an IBI for the Wabash River. This calibration was a preliminary index that was based on a limited number of sites and only a portion of the river from Lafayette (Tippecanoe County) to Wabash Island (Posey County). Gammon (2000) calibrated an index for the middle Wabash River, but this calibration was not based on an entire fish assemblage assessment; rather it focused on large, long-lived fish species. The State of Illinois does not have a large-river calibration for their water monitoring program.
In this paper, an IBI is presented that is designed to assess the quality of fish assemblages in the Wabash River. The index was developed using a large statewide database of standardized fish assemblage samples from numerous reaches of varying human impact. An objective procedure was followed to select and score the metrics that comprise the IBI, choosing metrics that represent a variety of the structural, compositional, and functional attributes of large and great rivers (Karr & Chu 1999). The index was then validated with independent data from 36 other river reaches that had anthropogenic disturbances, using as validity criteria the accurate and precise ranking of these other reaches in accordance with their degree of environmental degradation based on water quality, habitat, and use measures. Finally, this IBI was applied to the entire dataset to assess the relative effects of human impacts on river health.
METHODS
Survey design.--Between 1993 and 2001, teams of U.S. Environmental Protection Agency (USEPA), U.S. Fish and Wildlife Service, Indiana Department of Environmental Management, and Indiana Department of Natural Resources professionals sampled 275 large and great river (as defined by Simon & Emery 2000) sites as part of routine monitoring on the Wabash River. The Wabash River includes sites in wadeable stream (<2590 [km.sup.2]), large- and great fiver categories. Data used for this project were part of the USEPA's ecoregion project in Indiana (Simon & Stahl 1998), probabilistic assessment for water quality impairment, and monitoring of sport fishes in the Wabash River (Fig. 1). Sampling protocols followed boat electrofishing methods developed by USEPA (1988). In response to criticisms of the Simon & Stahl (1998) paper, large-river criteria development in the Wabash River (EA Engineering, Science, and Technology, Inc. 1999) were reassessed by external peer review, and comments were responded to by Simon & Stahl (2001). The arguments presented in EA Engineering, Science, and Technology, Inc. (1999) were not found to be credible by the external review panel. Protocols, data, and analysis of results were found to be consistent and reproduceble. The conclusion of the external peer review panel was fully supported by both the State of Indiana and the U.S. Environmental Protection Agency.
The Wabash River traverses two ecoregions in Indiana, including the Interior River Lowland and the Eastern Corn Belt Plain (Omernik & Gallant 1988). The Interior River Lowland (IRL) extends from central Indiana along the Wabash River floodplain to the Ohio River and includes the Mississippi River floodplain. The IRL has varied land use including forestry, diverse cropland agriculture, orchards, livestock production, and oil and gas production. The IRL consists of dissected glacial till plains, which are covered by thick mantle loess, rolling narrow ridgetops, and hilly to steep ridge and valley slopes. Woods et al. (1995) subdivided the ecoregion into two subregions that include the area along the Wabash River floodplain to the White River mouth. The Eastern Corn Belt Plain (ECBP) extends from Lafayette to the river's headwaters in Ohio. The ECBP consists of gently rolling glacial till plain, which is broken by moraines, kames, and outwash plains.
Large rivers are defined as drainage units with watersheds greater than 2590 [km.sup.2] (1000 [mi.sup.2]) but less than 5957 [km.sup.2] (2300 [mi.sup.2]) (Simon & Emery 2001), which are effectively sampled using a boat-mounted electrofishing unit. Great rivers include drainage areas greater than 5957 [km.sup.2]. Following the definition of Lyons et al. (1996) and Mundahl & Simon (1999), the thermal classification for all portions of the Wabash River is warmwater, which means that summer temperatures are too warm to allow the survival of salmonid fishes. Site selection was chosen to maximize different locations along the Wabash River so that various fiver reaches incorporating different sizes along the regional gradient were sampled. These sites are representative of the condition of the Wabash River; however, sites were picked to deliberately encompass the full range of natural habitat and flow conditions that exist among the Wabash River. The inclusion of the entire suite of sites enables the entire range of conditions to be used to develop both negative and positive metrics. Also, inclusion of sites were selected so that all geographic portions of the drainage were included. By including drainage areas ranging from 1139.6 to 85,231.7 [km.sup.2], we provide data from sites that are smaller than typical large-river sites. Site information does not suggest that this is a violation of the River Continuum Concept, since these sites do not reflect an accretion of data sufficient to warrant a drainage area metric calibration. By testing ecoregion and drainage area hypotheses, this enables the creation of a single IBI that does not warrant unnecessary separation of expectations based on ecoregion or size. Although the literature shows that small headwater ( 54-2590 [km.sup.2]) demonstrate a strong species area relationship with drainage area, the size of the main stem Wabash River data used in this study is clearly larger than these size categories; thus it is not surprising that a drainage area calibration correction was not warranted.
A five step process in IBI development was followed, including validation, and application that was modified by Lyons et al. (2001) after the recommendations in Hughes et al. (1998) and Karr & Chu (1999). First, an appropriate sampling methodology was identified and tested. Second, this methodology was used to collect fish assemblage data in a standardized manner...
NOTE: All illustrations and photos
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More articles from Proceedings of the Indiana Academy of Science
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