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ISSUES AND RECCOMMENDATIONS FOR POREWATER TOXCITY TESTING: METHODOLOGICAL UNCERTAINTIES, CONFOUNDING FACTORS AND TOXCITY IDENTIFICATION EVALUATION PROCEDURES
Citation:
Nipper, M., G. A. Burton Jr, D. Chapman, K. Doe, M. Hamer, AND K T. Ho. ISSUES AND RECCOMMENDATIONS FOR POREWATER TOXCITY TESTING: METHODOLOGICAL UNCERTAINTIES, CONFOUNDING FACTORS AND TOXCITY IDENTIFICATION EVALUATION PROCEDURES. Chapter 7, RS Carr and M. Nipper (ed.), Porewater Toxicity Testing: Biological, Chemical, and Ecological Considerations with a Review of Methods and Applications, and Recommendations for Future Areas of Research - Summary of a SETAC Technical Workshop. SETAC Techincal Publication, SETAC PRESS, Pensacola, FL, , 143-162, (2003).
Description:
During the last decade porewater toxicity tests have gained popularity among researchers and managers as tools for the assessment of the presence and biological effects of bioavailable contaminants in aquatic sediments. However, there are a number of information gaps in our knowledge of the biogeochemical processes occurring in sediments and pore waters, and of artifacts introduced during removal of pore water from sediments on the accuracy and precision of the methods used for porewater sampling, toxicity testing, and toxicity identification evaluation (TIE) procedures.
Some of the methodological uncertainties associated with porewater testing include appropriate sediment sampling, porewater extraction and storage procedures. In addition to these uncertainties, several features inherent to sediments, such as salinity for marine and estuarine pore waters, hardness for freshwater samples, dissolved oxygen (DO), pH, and numerous others, can affect the results and act as confounding factors in porewater toxicity tests. Some chemicals, such as ammonia and sulfides, can be natural features in some sediments but anthropogenically induced in others. All these factors must be considered when pore water is sampled, toxicity tests are conducted, and results are interpreted.
Several species and endpoints are currently used in porewater toxicity tests throughout the world (see Carr et al. and Scroggins et al., Chapters 9 and 12 of this book, respectively; Carr 1998), but scientists and managers often still pursue the use of indigenous species. The adequacy of different available types of porewater toxicity tests, encompassing a variety of species from different habitats (e.g., planktonic vs. benthic), life stages, endpoints, in situ and laboratory tests, and the use of indigenous vs. non-indigenous species for both marine and freshwater environments are addressed in this chapter.
The use of porewater is also advantageous in performing TIE procedures because TIE methods are not fully developed for solid-phase sediment tests. Therefore, porewater tests present a major advantage when there is a need to identify the types and/or the sources of contaminants in a particular area.
The state of the scientific knowledge regarding the aspects above was discussed in the Technical Workshop on Porewater Toxicity Testing, and will be presented in this chapter, concluding with a series of recommendations, identified information gaps and research needs.