Bioassays sediment testing

The A. marina bioassay is routinely used in the UK, but only in more saline conditions (Thain and Bifield, 2001). The survival of this polychaete in our study was hardly affected by the sediments tested during the study, but the number of casts produced varied considerably (Table 6). Significant effects with the above sediment in vivo bioassays used here have been demonstrated in other studies, not only in Dutch harbour sediments, but also marine and estuarine environments (Matthiessen et ah, 1998 Kater et al., 2001 Stronkhorst, et al., 2003b). 

Phase 2. In the seeond phase of the study, the partieipants were asked to analyze three extraeted and cleaned sediment samples using the DR CALUX bioassay. Sediments used for extraetion and cleanup were freshwater sediments from the Western Seheldt, The Netherlands. The sediment extracts were prepared by the Royal Institute for Fishery Research (RIVODLO), IJmuiden, The Netherlands, aeeording to the protoeol given here. Dilutions of the supplied sediment extracts were prepared by the partieipants in DMSO and tested for dioxin and/or dioxinlike content. On each 96-well mierotiter plate, a 2,3,7,8-TCDD standard ealibration curve was analyzed. Raw data as well as eonverted data were used for statistieal evaluation. 

The general objective, principle, and scope of application of the pT-method are succinctly described in Section 1 and also reported elsewhere in this book (see Chapter 3 of this volume, Section 5.1), where readers will appreciate that this hazard assessment scheme is adaptable to both liquid and solid media. Briefly recalled here in the context of solid-media samples such as dredged material, the pT-value, which relates to a single bioassay, and the pT-index, derived from the most sensitive organism in a test battery, permit a numerical classification of environmental samples on the basis of ecotoxicological principles. Sediment from any aquatic ecosystem (freshwater, brackish, marine) and from any of its phases (whole sediment, porewaters, elutriates or organic extracts) can be appraised provided that the proper standardized toxicity tests are available. There are whole-sediment test protocols standardized for many agencies (e.g., Environment Canada, ASTM). 

Hill, I.R., Matthiessen, R, and Heimbach, F. (Eds.) (1993). Guidance Document on Sediment Toxicity Tests and Bioassays for Ereshwater and Marine Environments. SETAC Europe Workshop on Sediment Toxicity Assessment. Renesse, the Netherlands, November 8-10, 1993. 

Since persistence in sediments is longer than that in the water column, the relevant toxicity studies are those that consider longer term, chronic exposures. A number of standard tests have been developed for assessing sediment toxicity and the bioassay of field collected sediments (e.g., [16-24]). The most commonly tested freshwater species are arthropods, including the amphipod shrimp // azteca and chironomid midge larvae, both Chironomus dilutus (formerly C. tentans) and C. riparius. Water-only studies have demonstrated that II. azteca are particularly sensitive to SPs (see Sect. 3) and in the published literature, this is the most commonly tested species for assessing the sediment toxicity of SPs. 

As part of this field study, relevant quality assurance/quality control (QA/QC) criteria and guidelines (SETAC, 1993 JAMP, 1998a,b) have to be set to insure the quality of data generated during the assessments. The development of QA/QC criteria for this study involved conducting a series of replicate bioassays with each of the methods. Samples tested included a control sediment, contaminated sediments and reference toxicants. Based on the results of the bioassay replicates, the variability associated with the tests was quantified and we were able to determine what we considered acceptable QA/QC criteria for these methods. 

The bacterial Microtox tests and the other in vitro bioassays clearly indicated differences in sediment toxicity between locations (Table 7). In the Microtox SP assay inhibitory effects were found in sediment extracts from the Port of Amsterdam transect (i.e. TU values greater than 20 at sites 7 and 11). The highest response in the Mutatox assay was found at Oranjesluis (site 11) in the Port of Amsterdam. The reference values from the Mutatox assay at this site were below... 

In the whole sediment toxieity bioassay mortality was tested in a 750 em2 aquarium with a 10 cm layer of sediment and eovered with 10 em of filtered seawater with a salinity 32 4 g 1 at a flow rate of 10 2 L per 24 hours, and a water temperature of 15 2°C. At the end of the 14 days exposure, organisms were reeorded dead when they did not burrow within 30 minutes. Potential confounding factors such as salinity, oxygen, concentration of NH, and pH of the water phase were monitored to ensure validity eriteria as defined by Postma et al. (2002). 

Previous application of bioassays in sediment toxicity testing... 

Table 2 Action levels (AL) applied in the Chemical Toxicity Test (CTT) system to judge whether dredged material from Dutch harbours can be disposed at sea. Underlined values exceeds the AL threshold. The three bioassays in the marked Box are evaluated in Table 3. Loswal Noord is the Reference station where harbour sediments are dumped. 

The in vitro bioassay for dioxins with cleaned sediment extracts (DR-CALUX) proved to comply with the QA/QC criteria needed to guarantee the reliability of data in an inter- and intralaboratory study (Besselink et al., 2004). The chemical stability of dioxins makes it possible to apply destructive clean-up procedures which remove all matrix factors. Sample extraction and cleanup for other in vitro bioassays for specific mechanisms of toxicity require further development to make sure that the chemicals of interest are not lost or unwanted chemicals included in the sediment extract to be tested. Table 4 summarizes possible bioassays that could be performed in addition to chemical analyses with the dredged sediment in a licensing system. 

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