The sediment-contact test using the ostracod Heterocypris incongruens: Effect of fine sediments and determination of toxicity thresholds.

The toxicity test using freshwater ostracods of the species Heterocypris incongruens is a sub-chronic static test that exposes individuals to whole sediments over a period of 6 d, the endpoints being mortality and growth. We tested the hypothesis that endpoints of the sediment bioassay using Heterocypris incongruens are affected by the presence of fine sediment particles by testing control sediment supplied with the commercial test kit with increasing proportions of kaolin clay as a proxy for fines. While mortality was not affected, the results showed that increasing the presence of clay reduced ostracod growth. Based on the variability in growth, a sublethal toxicity threshold of 35% is proposed to distinguish effects due to sediment properties from those due to toxicity. The relevance of this threshold was verified using data from toxicity tests of ambient sediment samples with low levels of contamination.

Biodynamic modelling and the prediction of accumulated trace metal concentrations in the polychaete Arenicola marina.

The use of biodynamic models to understand metal uptake directly from sediments by deposit-feeding organisms still represents a special challenge. In this study, accumulated concentrations of Cd, Zn and Ag predicted by biodynamic modelling in the lugworm Arenicola marina have been compared to measured concentrations in field populations in several UK estuaries. The biodynamic model predicted accumulated field Cd concentrations remarkably accurately, and predicted bioaccumulated Ag concentrations were in the range of those measured in lugworms collected from the field. For Zn the model showed less but still good comparability, accurately predicting Zn bioaccumulation in A. marina at high sediment concentrations but underestimating accumulated Zn in the worms from sites with low and intermediate levels of Zn sediment contamination. Therefore, it appears that the physiological parameters experimentally derived for A. marina are applicable to the conditions encountered in these environments and that the assumptions made in the model are plausible.

Sediment quality assessment and dredged material management in Spain: Part I, application of sediment quality guidelines in the Bay of Santander.

Sediments are an essential component of aquatic ecosystems that must be assessed and managed properly. The use of quantitative environmental quality standards derived from consideration of sediment quality guidelines (SQGs) can be effective as part of a tiered risk assessment approach. In Part I of this 2-part paper addressing sediment quality assessment and dredged material management in Spain, different SQG methods are used to evaluate sediment quality in the Bay of Santander, located in the Cantabric Sea along the northern coast of Spain, and to guide development of empirically derived SQGs for marine sediments. The results of the study indicate a great heterogeneity of SQGs, both with regard to the numeric values for a particular chemical and the number of substances for which SQGs have been derived. The analysis highlights the scarce development of empirical SQGs for priority substances identified in current European Union water policy. Nonetheless, the application of SQGs makes it possible to classify different zones of sediment quality in the Bay of Santander. Part II of this 2-part paper considers the environmental impacts of dredged material disposal. Legislation and criteria used to regulate dredged material disposal at sea in different European countries are reviewed, and action levels derived by different countries were used to evaluate management of dredged sediments from Cádiz Bay, located on the South Atlantic coast of Spain.

Sediment quality assessment and dredged material management in Spain: Part II, analysis of action levels for dredged material management and application to the Bay of Cádiz.

When sediments are removed from aquatic bottoms, they turn into dredged material that must be managed, taking into account its environmental impact. In Part II of this 2-part paper addressing sediment quality assessment and dredged material management in Spain, legislation and criteria used to regulate dredged material disposal at sea in different European countries are reviewed, as are action levels (ALs) derived by different countries used to evaluate management of dredged sediments from Cádiz Bay located on the South Atlantic coast of Spain. Comparison of ALs established for dredged material disposal by different countries reveals orders of magnitude differences in the values established for the same chemical. In Part I of this 2-part paper, review of different sediment quality guideline (SQG) methods used to support sediment quality assessments indicated a great heterogeneity of SQGs, both with regard to the numeric values for a particular chemical and the number of substances for which SQGs have been derived. The analysis highlighted the absence of SQGs for priority substances identified in current European Union water policy. Here, in Part II, the ALs are applied to dredged sediments from Cádiz Bay (South Atlantic coast of Spain), evidencing that the heterogeneity of ALs implemented in the reviewed countries could determine different management strategies. The application of other measurements such as bioassays might offer information useful in identifying a cost-effective management option in a decision-making framework, especially for dredged material with intermediate chemical concentrations.