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Comparison of bulk sediment and sediment elutriate toxicity testing methods
Citation:
Haring, H. J., M. E. Smith, J. M. LAZORCHAK, P. CROCKER, A. EURESTI, M. C. Wratschko, AND M. Schaub. Comparison of bulk sediment and sediment elutriate toxicity testing methods. ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY. Springer, New York, NY, 58(3):676-683, (2011).
Impact/Purpose:
Research is focused on Agency’s long-established aquatic toxicological organism, the fathead minnow (Pimephales promelas). Although numerous molecular biological approaches are exploited, foremost methods leading to development of molecular indicators are assembly and manufacture of DNA microarrays containing transcriptionally relevant gene sequences of fathead minnow, and the detection of novel or differentially expressed proteins by means of 2-D polyacrylamide gel electrophoresis followed by mass spectrometry. An extensive effort in 'gene discovery' research with the fathead minnow has been the primary emphasis of respective research areas, since high-throughput genome sequencing efforts-such as those in human and mouse-have not been directed toward organisms used in aquatic toxicity testing such as fathead minnows. Gene discovery research is fundamental to identified research areas, and is expected to be augmented by high-throughput cDNA sequencing data arising through a collaborative effort with the Dept. of Energy, Joint Genome Institute. Also, proteins induced to differential expression by chemical exposure will be used in ‘reverse genetics’ approach wherein knowledge of protein sequence will make possible the investigation of gene function and associated mechanistic biology. Following development and validation, fathead minnow microarrays, along with critical indicators identified by expression proteomics, will enable extensive molecular profiling studies, the hypotheses of which are that unique patterns of gene expression will be detected in targeted tissues of fathead minnows exposed to individual chemical stressors. Identification of unique, differentially expressed genes will then provide the basis for stressor-specific, quantitative molecular indicators, theory and methods that can be readily transferred to investigators within USEPA Regions, Tribes and states. Ultimately, proposed research will provide environmental science and risk assessment communities with advanced molecular biological indicator methods, complete with validation studies and guidance for their application. Early success has been achieved in the transfer of molecular indicator technologies to USEPA Region 9 and State of California.
Description:
Elutriate bioassays are among numerous methods that exist for assessing the potential toxicity of sediments in aquatic systems. In this study, interlaboratory results were compared from 96-hour Ceriodaphnia dubia and Pimephales promelas static-renewal acute toxicity tests conducted independently by two laboratories using elutriate samples prepared from the same sediment. The goal of the study was to determine if the results from the elutriate tests were comparable between two U.S. Environmental Protection Agency (USEPA) laboratories when different elutriate preparation procedures were employed by each lab. Of the 25 samples analyzed, 10 were found to be toxic to at least one of the species tested by either laboratory. The C. dubia elutriate tests conducted by the National Exposure Research Laboratory in Cincinnati, Ohio (NERL-Cincinnati) indicated 7 of the 25 sediment samples were toxic, while 8 sediment samples were characterized as such in C. dubia testing conducted by USEPA Region 6. The P. promelas elutriate tests conducted by NERL-Cincinnati revealed 8 samples as toxic, while USEPA Region 6 P. promelas tests displayed toxicity in 5 of the samples. McNemar's test of symmetry for C. dubia (S = 0.33, p = 0.5637) and P. promelas (S = 3.0, p = 0.0833) tests indicated no significant differences in designating a site toxic between NERL-Cincinnati and USEPA Region 6 laboratories. Likewise, Cohen's kappa test revealed significant agreement between NERL-Cincinnati and USEPA Region 6 C. dubia (K = 0.7148, p <0.01) and P. promelas (K = 0.6939, p < 0.01) elutriate tests. The authors conclude that differences in interlaboratory elutriate preparation procedures have no bearing on the ability of either the C. dubia or P. promelas bioassay testing methods to detect toxicity, while yielding similar results.