Assessment of Effluent Impacts Through Evaluation of Periphyton Diatom Community Structure

Evaluation of changes in periphyton diatom community structure proved to be a useful means of assessing the impact of an electroplating waste discharge on the biota of the Muskingum River in Ohio. The copper waste discharge decreased species richness and species diversity (as indicated by the Shannon-Weaver and Brillouin indexes) of the diatom community collected from artifical substrates. Corresponding evenness and redundancy components also indicated stressed conditions.

Short-count intervals of detailed readings were compared to determine the ability and sensitivity of these shorter efforts of enumeration to respond to community changes. Counts of 500 diatom cells, while accurately responding to gross perturbations when applied in the form of biotic indexes, were somewhat inconsistent and apparently insensitive to minor shifts in diatom community structure. Counts of 1000 diatom cells more closely paralleled the trends developed by the 5000-cell long counts. Extension of the diatom counts beyond 2000 cells yielded less species information for the manhours required, and it was at this level that the species curve began to approach an asymptote.