CORRELATIONS BETWEEN SOLID-PHASE MICROBIAL SCREENING ASSAYS, WHOLE-SEDIMENT TOXICITY TESTS WITH MACROINVERTEBRATES AND IN-SITU BENTHIC COMMUNITY STRUCTURE

There have been few comparative assessments of the relative sensitivities of microorganisms in short-term (1 to 20 min.) screening bioassays and benthic invertebrates exposed for longer periods of time (10- to 28-d) to contaminated sediments. In this paper, the responses of four species of benthic invertebrates (Chironomus riparius, Hyalella azteca, Hexagenia spp., and Tubifex tubifex) and three microorganisms (Escherichia coli, Photobacterium phosphoreum, and Bacillus spp.) were compared using rank correlation (Spearman's r(s)), for sediments collected from 46 nearshore sites (<3 km) in the Laurentian Great Lakes. At a subset of sites (n = 27), data an the benthic invertebrate community structure were obtained and these sires were ranked and compared to the responses in each of the laboratory tests. The results indicate that two of the microbial screening tests, specifically, the Sediment-Chromotest(R), which measures inhibition of the inducible enzyme, beta-galactosidase, in E. coli, and the Microtox(R) Solid-phase Test (measures inhibition of bioluminescence), correlated with results from tests with invertebrates, particularly decreased survival of C. riparius (r(s) = 0.545 and 0.463, respectively), reduced growth of H. azteca (r(s), = 0.347 ann 0.467, respectively) ansi Hexagenia (r(s) = 0.307 and 0.385, respectively) and lower production of cocoons by T. tubifex (r(s) = 0.347 and 0.416, respectively). In addition, reduced growth of C. riparius was positively correlated with reduced growth of the mayfly, Hexagenia spp. (r(s) = 0.655), survival and growth of the amphipod, H. azteca (r(s) = 0.416 and 0.570) and decreased production of cocoons (r(s) = 0.703) or live young (r(s) = 0.658) by T. tubifex. When information on the structure of the benthic invertebrate community was included as a subset of the delta (n = 27), two microbial tests (Microtox(R) SPT and Sediment-Chromotest(R)) and several invertebrate tests (e.g., growth of C. riparius, H. azteca, and Hexagenia and reproduction by T. tubifex) were strongly correlated with a degradation of the benthic community composition.