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 sensitivit ies 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 (Esche richia coli, Photobacterium phosphoreum, and Bacillus spp.) were compa red using rank correlation (Spearman's r(s)), for sediments collected from 46 nearshore sites (<3 km) in the Laurentian Great Lakes. At a su bset of sites (n = 27), data an the benthic invertebrate community str ucture were obtained and these sires were ranked and compared to the r esponses in each of the laboratory tests. The results indicate that tw o of the microbial screening tests, specifically, the Sediment-Chromot est(R), which measures inhibition of the inducible enzyme, beta-galact osidase, in E. coli, and the Microtox(R) Solid-phase Test (measures in hibition 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. ripari us was positively correlated with reduced growth of the mayfly, Hexage nia spp. (r(s) = 0.655), survival and growth of the amphipod, H. aztec a (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 o n the structure of the benthic invertebrate community was included as a subset of the delta (n = 27), two microbial tests (Microtox(R) SPT a nd Sediment-Chromotest(R)) and several invertebrate tests (e.g., growt h of C. riparius, H. azteca, and Hexagenia and reproduction by T. tubi fex) were strongly correlated with a degradation of the benthic commun ity composition.