Phase 2: Feasibility of Implementation 



Given that aspects of the benthic macroinvertebrate community can be used as indicators of degraded areas, 

 how does a benthic index represent degraded benthic communities? The development of the benthic index 

 is based on a simple question: if you have a set of known degraded and undegraded areas, what components 

 of the benthic community best discriminate between the two? The degraded and undegraded sites were 

 chosen from the EMAP-E database according to strict criteria involving environmental parameters that are 

 known to affect the benthic community (e.g., hypoxia, sediment contaminants, and sediment toxicity). This 

 was done without prior knowledge of the benthic communities at those sites. A suite of parameters that 

 represented aspects of benthic community structure and function were compiled for these sites (Engle et al. 

 1 994, Engle and Summers 1 999). The statistical techniques of discriminant analysis were applied in order to 

 choose a subset of parameters that best discriminated between the degraded and undegraded sites. 

 Appropriate coefficients (or weights) were computed by canonical discriminant analysis. The benthic index is 

 a linear function of the weighted parameters that represent the subset that best discriminates between degraded 

 and undegraded sites. The benthic index was scaled to range from to 10 and threshold values were 

 determined empirically from the data. The final result is an index that, when calculated to be below the 

 threshold value for a given site, indicates that the benthic community at that site is similar to benthic communities 

 found at known degraded sites. The summary of the development of EMAP-E's benthic index given here is 

 brief; more detail on the development, validation, and application of the benthic index may be found elsewhere 

 (Engle etal. 1994, Engle and Summers 1998, Engle and Summers 1999). 



Guideline 3: Data Collection Methods 



Methods for collecting all indicator measurements should be described. Standard, well-documented 

 methods are preferred. Novel methods should be defended with evidence of effective performance and, 

 if applicable, with comparisons to standard methods. If multiple methods are necessary to 

 accommodate diverse circumstances at different sites, the effects on data comparability across sites 

 must be addressed. Expected sources of error should be evaluated. 



Methods should be compatible with the monitoring design of the program for which the indicator is 

 intended. Plot design and measurements should be appropriate for the spatial scale of analysis. Needs 

 for specialized equipment and expertise should be identified. 



Sampling activities for indicator measurements should not significantly disturb a site. Evidence should 

 be provided to ensure that measurements made during a single visit do not affect the same 

 measurement at subsequent visits or, in the case of integrated sampling regimes, simultaneous 

 measurements at the site. Also, sampling should not create an adverse impact on protected species, 

 species of special concern, or protected habitats. 



Field and laboratory methods for collecting and processing benthic macroinvertebrate samples are thoroughly 

 documented in Heitmuller and Valente (1 991 ), Macauley (1 991 ), and U.S. EPA (1 995). 



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