Recently, researchers have successfully developed multimetric indices that combine the various effects of 

 natural and anthropogenic disturbances on benthic communities. Although initially developed for freshwater 

 systems (Lenat 1988, Lang et al. 1989, Plafkin et al. 1989, Kerans and Karr 1994, Lang and Reymond 

 1995), variations of the benthic index of biotic integrity (B-IBI) concept have been successfully applied to 

 estuaries (Engle etal. 1994, Ranasinghe etal. 1994, Weisberg etal. 1997, Engle and Summers 1999, Van 

 Dolah etal. 1999). There are some basic differences between the approach we have used and the traditional 

 IBI approach. The parameters that comprise our benthic index were chosen empirically as the parameters 

 that provided the best statistical discrimination between sites with known degraded or undegraded conditions 

 (where degraded is defined as having undesirable or unacceptable ecological condition). The weighting 

 factors applied to these parameters were also determined empirically based on the contribution of each 

 parameter to the fit of the model. The parameters included in a traditional IBI approach were chosen by the 

 researchers based on evaluations of cumulative ecological dose response curves. The rank scoring of each 

 parameter (e.g., as a 1 , 3, or 5) was based on a subjective weighting of the distribution of values from known 

 sites. The parameters in the IBI are equally weighted in the calculation of the overall rank score. Both 

 approaches to developing multimetric indices have advantages and criticisms; however, the ultimate goal is 

 the same - to combine complex community information into a meaningful index of condition. 



Multimetric benthic indices can help environmental managers who require a standardized means of tracking 

 the ecological condition of estuaries. However, environmental managers and policy makers also desire an 

 easy, manageable method of identifying the extent of potentially degraded areas and a means of associating 

 biotic responses with environmental stressors (Summers etal. 1 995). In order for an indicator to be appropriate 

 for the assessment of estuarine health, it should incorporate geographic variation and should recognize the 

 inherent multivariate nature of estuarine systems (Karr 1993, Wilson and Jeffrey 1994). While the statistical 

 methods used to develop indicators may often be complex, it is the end product, an index of condition, that 

 is of interest to resource managers. By applying a mathematical formula to multivariate benthic data, resource 

 managers can calculate a single, scaled index that can then be used to evaluate the benthic condition of 

 estuaries in their region. Although indices have been accused of oversimplifying orovergeneralizing biological 

 processes, they play an important role in resource management {i.e., to provide criteria with which to 

 characterize a resource as impaired or healthy) (Rakocinski et al. 1997). While ecological indicators were 

 developed to serve as tools for the preliminary assessment of ecological condition, they are not intended to 

 replace a complete analysis of the benthic biological dynamics nor were they intended to stand alone. They 

 also should be used in conjunction with other synoptic data on sediment toxicity and pollutant concentrations 

 to provide a weight-of-evidence basis for judging the incidence of anthropogenically induced disturbances 

 (Hylandefa/. 1998). 



Phase 1: Conceptual Relevance 



Guideline 1: Relevance To The Assessment 



Early in the evaluation process, it must be demonstrated in concept that the proposed indicator is 

 responsive to an identified assessment question and will provide information useful to a management 

 decision. For indicators requiring multiple measurements (indices or aggregates), the relevance of each 

 measurement to the management objective should be identified. In addition, the indicator should be 

 evaluated for its potential to contribute information as part of a suite of indicators designed to address 

 multiple assessment questions. The ability of the proposed indicator to complement indicators at other 

 scales and levels of biological organization should also be considered. Redundancy with existing 

 indicators may be permissible, particularly if improved performance or some unique and critical 

 information is anticipated from the proposed indicator 



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