Biocriteria

		Overview
		Discussion
		» Components of Biocriteria

Overview

"Regulatory activities under the Federal Water Pollution Control Act of 1972 and its 1977 and 1987 amendments require knowledge of the potential fish or biological community that can be supported in a stream or river (termed "aquatic life use designations"). The presence and abundance of stream fishes is strongly related to the physical and chemical characteristics of a stream (Gorman and Karr 1978; Schlosser 1982). The Qualitative Habitat Evaluation Index (QHEI) is designed to provide a measure of habitat that generally corresponds to those physical factors that affect fish communities and which are generally important to other aquatic life (e.g. invertebrates). This index is based on six interrelated metrics: substrate, instream cover, channel morphology, riparian and bank condition, pool and riffle quality, and gradient. These metrics have been shown to be correlated with stream fish communities." (The Qualitative Habitat Evaluation Index [QHEI] Rationale, Methods and Applications. Edward T. Rankin. November 6, 1989) Biological criteria (biocriteria = "aquatic life use designations) are narrative or numeric expressions of the health and well-being of aquatic life and are based on the numbers and kinds of aquatic organisms which inhabit a particular stream or river sampling site. Biocriteria are derived from a complex process using data which reflects the reference condition within a particular geographic region of the state (Ohio EPA 1987a,b; Ohio EPA 1989a,b). As such biocriteria represent a direct measure of the attainment or non-attainment of aquatic life use designations for Ohio's streams (aquatic life use attainment status.). Ohio EPA incorporated biocriteria into the Ohio Water Quality Standards (WQS; Ohio Administrative Code 3745-1) regulations in February 1990 (effective May 1990). These criteria consist of numeric values for the Index of Biotic Integrity (IBI) and the Modified Index of well-being (MIwb), both of which are based on information about stream fish assemblages, and the Invertebrate Community Index (ICI), which is based on information about stream macroinvertebrate assemblages. Criteria for each biological index are specified for each of Ohio's five ecoregions (as described by Omernik 1987)

_top

Discussion

Components of Biocriteria

QHEI - Qualitative Habitat Index The Qualitative Habitat Evaluation Index (QHEI) measures the physical integrity and habitat of the stream channel including the floodplain. This index ranks features necessary to support aquatic life such as: substrate type and quality instream cover type and quantity channel sinuosity, stability and channelization riparian width and erosion floodplain quality riffle substrate and embeddedness rille and run depths pool morphology riffle and pool depths ICI - The Invertebrate Community Index The invertebrate community index is a combination of 10 metrics collectively used to describe the health of the macroinvertebrate community in the a stream such as: production function tolerance reproduction IBI - The Index of Biological Integrity The Index of Biological Integrity is a combination of 12 metrics collectively used to describe the health of the fish community in a stream such as their: production function tolerance reproduction Ecoregions (from OPEA; 2000 Ohio Water Resource Inventory) Central to Ohio EPA's use of ambient biological, chemical, and physical information is the concept of "ecoregions" and the regional reference sites concept. Omernik's (1987) ecoregions (level III) are land-surface areas that are grouped based on similarities in the mosaic of land use, potential natural vegetation, land surface form, and soils that occur within each. These underlying factors determine the character of watersheds and have a profound influence on background water quality, the type and composition of the biological communities in a stream or river, and the manner in which human impacts are exhibited.

_top