ABSTRACT
In October 1992 during low-flow conditions, we conducted an evaluation of spatial variation in macrobenthic assemblages from the lower Sulphur River system (Texas and Arkansas border) in relation to bleached kraft mill effluent (BKME). We adopted a multifaceted approach using detailed taxonomic data and various quantitative methods. A classification analysis based on assemblage similarity showed a close relationship between the effluent site and a neighboring site located 2.3 river miles (3.7 km) downstream of the effluent. Although the farthest upstream and downstream sites were separated by 14.0 river miles (22.5 km) as well as by intrinsic habitat differences, they were closely linked in the classification analysis. Complementary variation in relative abundances of three taxonomic core groups (tubificids, chironomids, and ceratopogonids) helped explain the classification analysis. Furthermore, the macrobenthic composition of the outfall canal resembled that of neighboring river sites. High total densities of macrobenthic organisms greater than 3400 m−2 occurred at both the effluent site and the neighboring downstream site. Parallel among-site variation in tubificid abundances implied that differences in this taxonomic group might be driving among-site variation in total densities. The predominant macrobenthic pattern suggested organic enrichment as a possible chronic effect of BKME on macrobenthic assemblages. Nonetheless, a relatively high species richness and typical taxonomic diversity occurred at the effluent site. This study illustrates the utility of taking a whole-community approach using detailed taxonomic data to identify chronic macrobenthic effects of pulp mill effluents.
