The utility of invertebrate secondary production in stream assessments

Invertebrate communities are commonly used in stream bioassessments.  Typically, invertebrate abundances from a single point in time are used to determine the biological integrity of the stream.  Secondary production, by incorporating several life history parameters and multiple samplings through time, could be a better approximation of biological integrity.  We determined community structure, biomass, and secondary production of invertebrates in an urban and a forested stream.  Species richness, diversity, biomass, and production were lower in the urban stream than the forested stream, with most taxa representing tolerant taxa.  Species abundance, biomass, and production values were then used to determine the Kentucky Macroinvertebrate Bioassessment Index (KMBI) score for each stream to determine the relative 'sensitivity' of these three parameters in assessing biotic integrity.  All three KMBI estimates showed higher biotic integrity in the forested stream, but the relative difference between the two streams was least when taxa abundance values were used, and greatest when taxa production estimates were used.  Secondary production estimates could provide more sensitive measures of invertebrate communities for comparisons between steams, but should only be used when extra sensitivity in the analysis is needed due to the increased time, labor, and monetary cost of completing the work.