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1.3 PHYSICAL SCIENCES
The quality of sediment in any aquatic ecosystem is vital to the health of that system. Sediments have been recognised as a major repository for persistent toxic substances. If sediments become sufficiently polluted they can lead to the disruption of surrounding natural biological communities. Therefore the monitoring of sediment quality is essential for successful ecosystem functioning in the marine environment. The aim of the present study was to employ an integrated approach of the toxicity evaluation of Irish marine sediments by correlating results of biotests with chemical analysis. Between 2004 and 2006 the Radiation and Environmental Science Centre (RESC) participate in three Biological Effects Quality Assurances in Monitoring Programme (BEQUALM) whole organism inter-calibration programmes. The aim of this study was to assess operator skill and ensure that the bioassay methods to be employed in this three and a half year project were fit for purpose and of a standard that was internationally acceptable. Chapters Three and Four describe the ecotoxicological evaluation of five organic contaminants frequently detected in marine sediments (Chapter three) and the effects of two metal contaminants (Chapter four) of concern (CdC12 and CuC12) on a battery of marine bioassays employed for sediment assessment. The sensitivity of each species varied for all compounds highlighting the importance of employing a battery of multitrophic bioassay for the ecotoxicological assessment of environmental samples. Suitability of the Microtox and T. battagliai tests for employment in TIE studies were further assess through spiking experiments with tributyltin. The potential toxicity of various exposure phases of sediment from around Ireland is assessed in Chapter five. In addition to the evaluation of multi-exposure phases the use of a battery of multi-trophic test species has been advocated by a number of researchers as testing of single or few organisms may not detect toxicants with a specific mode of action. Therefore the developed battery of bioassays was again employed in this study to assess porewater, elutriate, whole sediment and solvent extracts, however, it was not possible to correlate the observed ecotoxicological effects with a specific and/or class of contaminants based on sediment chemistry alone. Therefore porewaters found to elicit significant toxicity (Dunmore East and Alexandra Basin) with the test battery were selected for further Phase 1 Tie assessment. The results of which are described in Chapter Six. Furthermore, the effects of storage duration of marine sediment is discussed and recommendations for future studies outlined. Finally the last two chapters describe two further integrated methods for sediment toxicity evaluation. Chapter Seven outlines a Bioassay Directed Fractionation procedure for organic solvent extracts to identify the main causative “organic” agents of toxicity in Dunmore East sediment extracts. Chapter Eight outlines the methods employed in a study to investigate the effectiveness of using caged dogwhelks and oysters transplanted to monitor the induction of imposex in areas with previously determined high levels of organotins. The possible link between DNA damage pathways and developmental and reproductive abnormalities in dogwhelks and mussels are also discussed with the use of the Comet assay and correlated with imposex data.
Macken, A. (2007). Integrated approach to the toxicity evaluation of Irish marine sediments : exotoxicological assessment.Dublin Institute of Technology. doi:10.21427/D7888G