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2K - Sediment Assays (TUP/152) Microbial characterization of artificial sediment and comparisons with natural sediments. Goedkoop, Willem1, Widenfalk, Anneli1, Haglund, Ann-Louise2, 1 Department of Environmental Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden2 Department of Limnology, Uppsala University, Uppsala, Sweden ABSTRACT- Sediment toxicity tests are standardized by using an artificial sediment that is made up of sand, kaolin clay, pulverized peat, and calcium carbonate. Although standardization of the sediment efficiently reduces the among-laboratory variability of test results, it also simplifies toxicity tests. For example, natural and artificial sediments may differ largely with respect to their binding characteristics, micro- and meiofaunal populations, and microbial assemblages. We quantified a number of microbial variables for the artificial sediment and compared these values for natural sediments from the scientific literature. Bacterial abundance of artificial sediment was 9.6-15*108 cells/g and was 2 orders of magnitude lower than that of natural sediments. Similar results were observed for microbial biomass (ATP). Furthermore, bacterial activity (3H-thymidine incorporation) in artificial sediment ranged 2.6-4.9 microgC/g.d and was much lower than values commonly reported for freshwater sediments. Also overall sediment respiration (CO2-production) was very low, 17-50 microgC/g.d. The results show that the artificial sediment had a poorly development microbial component, suggesting that degradation rates of test compounds by microbial activity may be much slower in the artificial sediment than in natural sediments. Differences in microbial activities, but also in binding characteristics and test-organism feeding behavior may affect the outcome of toxicity tests. Key words: toxicity testing, artificial sediment, microbes, bacteria |
