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Comparative sensitivity of centroptilum triangulifer, ceriodaphnia dubia and daphnia magna to standard salt and copper reference toxicants
Citation:
LAZORCHAK, J. M., P. C. Weaver, K. A. Hammer, B. R. JOHNSON, C. T. NIETCH, D. Funk, AND D. Buckwalter. Comparative sensitivity of centroptilum triangulifer, ceriodaphnia dubia and daphnia magna to standard salt and copper reference toxicants. Presented at SETAC, Boston, MA, November 13 - 17, 2011.
Impact/Purpose:
A great deal of uncertainty exists regarding the extent to which humans and wildlife are exposed to chemical stressors in aquatic resources. Scientific literature is replete with studies of xenobiotics in surface waters, including a recent national USGS survey of endocrine disrupting chemicals; however, biological significance of these chemical data is in question since chemical bioavailability is largely unknown and biological events may be induced by undetected chemicals and varying ecological conditions (i.e., total nitrogen and phosphorus). Whole effluent toxicity data exist, but do not answer specific exposure questions that may support detailed ecological risk assessments. Interpretation of data arising from exposure to complex chemical mixtures is even more problematic. A solution to these problems is development of sensitive and specific cellular indicators of exposure in aquatic organisms. The potential for development is enhanced by emergent resources in molecular biology and associated technologies, most notably DNA microarrays consisting of transcriptionally relevant nucleic acid sequences that can be used to detect altered gene expression in cells, tissues and various life stages of organisms exposed to chemical and natural stressors. Ecological investigation in the present Task have been partitioned into three focal research areas: (1) Core Computational Toxicology research, (2) Ecological research and (3) Molecular Diagnostics and endocrine disrupting compounds. Three areas of core and applied research will be consequential on development of molecular indicators diagnostic for exposure to specific xenobiotic, natural stressors, and complex mixtures thereof, in freshwater fish and invertebrates. 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.
Description:
Development of methods for assessing exposure and effects of produced waters from energy and mineral resource extraction operations on stream invertebrate species is important in order to elucidate environmentally relevant information. Centroptilum triangulifer is a parthenogenetic mayfly occurring in depositional habitats of streams and rivers of the eastern U.S. and Canada. C. tranfulifer is a relevant insect for monitoring stream water quality under laboratory and field conditions because of its short life cycle and unique mode of reproduction. In this study a colony of C. triangulifer was reared using a standardized diet of three monoculture diatoms, Mayamaea atomus var. permitis, Nitzschia cf. pusilla, and Achnanthidium minutissimum. Percent survival, fecundity measurements and pre-egg laying weights were used as indicators of overall colony health and fitness over five generations. Comparative testing assessed the exposure sensitivity to several standard salt reference toxicants, KCl, and NaCl, and a metal reference toxicant CuSO4 cu5rrently used in EPA's acute and chronic Whole Effluent Toxicity manuals and NaHCO3 and a TDS recipe. Sensitivity tests were run simultaneously with Ceriodaphnia dubia and Daphnia magna and were conducted for both acute and chronic endpoints. C. triangulifer was less sensitive to KCl but about 2.8 fold m ore sensitive to NaCl and CuSO4. Acute NaHCL3 results indicate that C. triangulifer is slightly more sensitive than C. dubia and D. Magna. Chronic results suggest that C. triangulifer may be 8 fold more sensitive to NaCl than C. dubia and 16 fold more sensitive than D. magna. These and other toxicity results will be presented.