Mud matters The significance of effect-based sediment quality assessment

Despite the apparent threat to aquatic ecosystems, contaminated sediments are mainly overlooked in water quality assessments. This thesis argued that an integrated sediment quality assessment method is needed to consider the risks to benthic biota of the effects of all bioavailable sediment-associated contaminants. Effect-based sediment quality assessment may provide much-needed quantification of the impact of contaminated sediments on aquatic ecosystem health. This thesis aimed to quantify the contribution of sediment contamination to aquatic ecosystem deterioration by advancing effect-based sediment quality assessment, and to enlarge the arsenal of test species for effect-based sediment quality assessment.
The first advancement of effect-based sediment quality assessment was to maintain the natural layering of sediment samples, ensuring a realistic exposure of the test species to the contaminated sediments. The second advancement concerned bioavailability-based chemical analysis of contaminated sediments, which allows a much more relevant assessment of the exposure of benthic invertebrates to sediment-associated contaminants than generic contaminant analysis. A passive sampling – passive dosing test was explored, which allowed quantifying the contribution of the organic contaminants in the sediment pore water to the observed effects in the bioassays, omitting the potential confounding influence of other stressors unrelated to chemical pressure. Lastly, the arsenal of sediment test species was enlarged because species-specific sensitivities to the plethora of compounds in contaminated sediments vary greatly. The newly added species were an informative addition to the limited number of currently available benthic test organisms.
This thesis concludes that sediment contamination is a potential stressor driving benthic macroinvertebrate community composition. The advancement of the effect-based sediment quality assessment generated in this thesis provided better tools to quantify the adverse effects of contaminated sediment on benthic invertebrates.