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of the factors responsible for degradation,
<br />and, (2) they have had a limited perspective
<br />on the components of biotic integrity.
<br />Five classes of variables are indicative of
<br />water resource degradation (Karr, 1993):
<br />(1) water quality (e.g., temperature,
<br />turbidity, dissolved oxygen, organic and
<br />inorganic chemicals, heavy metals, and
<br />toxic substances); *(2) habitat structure (e.g.,
<br />substrate type, water depth and current
<br />velocity, spatial and temporal complexity of
<br />physical habitat); (3) flow regime (e.g.,
<br />volume, temporal distribution of flows); (4)
<br />energy source (e.g., type, amount and
<br />particle size of organic material entering the
<br />stream, seasonal pattern of energy
<br />availability); and (5) biotic interactions
<br />(e.g., competition, predation, disease, and
<br />parasitism). Karr (1993) notes that any
<br />human activity that degrades one or more of
<br />these categories, degrades water resource
<br />quality.
<br />In Karr's system of IBI development (Karr,
<br />1981, 1993), two major components are
<br />included, i.e., elements and processes.
<br />Elements are factors such as species of
<br />plants and animals, genetic diversity within
<br />species, assemblages upon which species
<br />depend, and landscapes. Processes include
<br />factors like energy flow and nutrient
<br />dynamics, evolution and speciation,
<br />photosynthesis, water cycling, competition
<br />and predation, and mutualisms. Karr's
<br />approach to assessing biotic integrity
<br />integrates assessment of the extent to which
<br />elements or processes have been altered.
<br />Most efforts to develop an IBI include suites
<br />of metrics that represent three major classes
<br />of biotic ;attributes (Karr, 1993), i.e., (1)
<br />species richness and composition metrics,
<br />(2) trophic composition metrics, and (3)
<br />overall population sizes and the condition
<br />(health) of individuals. Each metric of an
<br />IBI should be an expression of known
<br />influence of human activities on the
<br />characteristics of the resident biota (Karr,
<br />1993). For example, as human disturbance
<br />increases, species richness, the number of
<br />trophic specialists, and the number of
<br />intolerant species decline, and, the number
<br />of trophie generalists increases. Winget and
<br />'Mangum "(1979), EMsenhoff (1982), and
<br />Lent (1993) have proposed methods for
<br />assignment of tolerance values for species.
<br />Karr and Kerans (1991) reported on
<br />development of an invertebrate IBI which
<br />may prove useful for development of
<br />invertebrate IBI's in New Mexico. In
<br />preliminary studies, these authors have
<br />found that the total number of invertebrate
<br />taxa declines with human influence and that
<br />the number of collector/filterer organisms
<br />tends to increase in degraded sites.
<br />Future analyses for upper Rio Grande sites
<br />and other similar sites in New Mexico
<br />should investigate more fully the utility of
<br />summary statistics for IBI development in
<br />New Mexico. These include: (1) number of
<br />chironomid species per site, (2) number of
<br />unique chironomid species per site, (3)
<br />species number-elevation relationship, (4)
<br />proportion of white suckers, or, proportion
<br />of Catostomidae, (5) proportion of trout,
<br />and (6) proportion of gravel spawners. In
<br />the development of an index of biotic
<br />integrity for New Mexico undoubtedly the
<br />Chama River station above Chama becomes
<br />the benchmark, or reference site, for sites in
<br />Aquatic Ecoregion 1. As analyses proceed,
<br />similar reference sites will be sought for
<br />western and southern mountain regions in
<br />New Mexico.
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