Final Report Summary - CHEEM (Improvement of SQGs through the incorporation of chronic exposure-effect model)
Project objectives
This summary presents research highlights and conclusions of the project entitled 'Improvement of Sediment Quality Guidelines (SQGs) through the incorporation of Chronic Exposure-Effect Model' (CHEEM).
The proposed objectives of this project were to:
a) implement SQGs quantifying the chronic toxicity of copper to benthic invertebrates applying varying exposure routes and for sediments with different characteristics (outgoing phase);
b) verify the level of protection of the derived SQGs for Spanish environment or if more site or regional-specific effects thresholds need to be redefined (return phase).
Research highlights
Most consistent outcomes were:
i) Normalisation of the sub-lethal effect and copper concentration in the overlying water to fine sediment fraction and particulate organic carbon highlighted that these components explain most of the variability and regulate copper concentration in the water phase. The EC50s calculated based on copper concentration in the overlying water were always lower than the effect thresholds measured for water-only exposures. These observations indicate that the particulate copper exposure pathway is the principal cause of toxicity (Campana et al., 2012).
ii) Comparison between measured and predicted sub-lethal effect concentrations calculated using logistic sigmoidal curves shows that the chronic exposure effect model based on the exposure to bio-available copper, calculated as a function of the dissolved and particulate copper concentration, the organism's feeding behaviour (ingestion rate) and physiology (uptake rate from water, assimilation efficiency of ingested particles), offers a good fit in predicting the copper toxic sub-lethal effect.
iii) In toxicity assessment, increasing importance is being placed on determining tissue metal residues-effect relationships that result from environmental exposure (dissolved and particulate sources). Following uptake, metals may partition within different subcellular tissues, be detoxified or excreted, depending on the accumulation pattern of a particular organism for a particular metal. Only the metabolically active fraction of metal contributes to toxicity. Our research also investigated the links between the subcellular metal partitioning and toxic effect to reproduction of the epibenthic amphipod Melita plumulosa and growth of the bivalve Tellina deltoidalis exposed to copper-contaminated sediments with varying properties. Stronger linear relationships were found for both organisms between the subcellular copper partitioning and organic carbon (OC)-normalised particulate copper concentrations, compared to copper concentrations in the water phase. This has important biological significance and highlights how most of the variability related to the reproduction of the amphipod and the growth rate of the bivalve can be explained by the increase of copper that is associated to the metabolically available fraction (MAF). These results provide further insight into the interaction between tissue residues and sub-lethal effects.
iv) Copper sub-lethal effect concentrations normalised to organic carbon content and particle size, obtained by amphipod, copepod and bivalve tests were compared to copper sediment quality guidelines derived from using species sensitivity distributions (SSDs) of copper effects data (Simpson et al., 2011). The derived SQGs vary in a predictable manner with changes in sediment particle size and organic carbon, and offer a significant improvement on the existing 'single value' SQG. Adequate protection for all benthic organisms is expected to be achieved for an OC-normalised copper concentration of 3.5 mg <63 µm Cu g-1 OC. Chronic EC10s calculated for Melita plumulosa and Nitocra spinipes were found 5.2 ± 2.2 and 4.8 ± 1.7 mg <63 µm Cu g-1 OC respectively (Campana et al., 2012) and highlighted the good agreement with the chronic guideline proposed. Results obtained from whole sediment toxicity tests applied to natural sediments using local organisms species (Tisbe battagliai and Scrobicularia plana), also confirm an adequate conservative level of protection for regulatory purpose offered by the proposed SQGs, also satisfactory for Spanish environment.
Conclusions
Compared to acute tests, sub-lethal and chronic tests offer a higher level of ecological realism due to the fact that exposure conditions are environmentally more representative and end points used, such as growth or reproduction, are regarded as more ecologically relevant. However, considerably more information is needed to predict sub-lethal and chronic effects of metals to benthic organisms, particularly on the chronic effects of dietary metals exposure (food and sediment ingestion pathway). The results obtained in this project made a more extensive sub-lethal effect data set available, which provides cause-effect information for copper in sediments with varying properties and underlines that dietary uptake to metals is a very significant exposure route for benthic organisms.
The provision of SQGs that better predict the effects of copper in sediment with varying properties and thus provide adequate protection against toxicity is very important for regulatory purpose and should be taken into consideration by environmental agencies and regulators.
SQGs tested for chronic exposures that vary in a predictable manner with changes in sediment physicochemical properties offer a significant improvement on the existing 'single value' SQGs.
Application of these SQGs to a local Spanish estuarine environment has confirmed a conservatory level of protection, satisfactory for the adequate protection of benthic organisms.
References
Campana, O., Simpson, S.L. Spadaro, D.A. Blasco, J., 2012. Sub-Lethal Effects of Copper to Benthic Invertebrates Explained by Sediment Properties and Dietary Exposure. Environ. Sci. Technol. 46, 6835-6842.
Simpson, S.L. Batley, G.E. Hamilton, I.L. Spadaro, D.A. 2011. Guidelines for copper in sediments with varying properties. Chemosphere 85, 1487-1495.
Contact details: Dr Olivia Campana, postdoctoral fellow.
Instituto de Ciencias Marinas de Andalucia CSIC - Spain
olivia.campana@icman.csic.es.
This summary presents research highlights and conclusions of the project entitled 'Improvement of Sediment Quality Guidelines (SQGs) through the incorporation of Chronic Exposure-Effect Model' (CHEEM).
The proposed objectives of this project were to:
a) implement SQGs quantifying the chronic toxicity of copper to benthic invertebrates applying varying exposure routes and for sediments with different characteristics (outgoing phase);
b) verify the level of protection of the derived SQGs for Spanish environment or if more site or regional-specific effects thresholds need to be redefined (return phase).
Research highlights
Most consistent outcomes were:
i) Normalisation of the sub-lethal effect and copper concentration in the overlying water to fine sediment fraction and particulate organic carbon highlighted that these components explain most of the variability and regulate copper concentration in the water phase. The EC50s calculated based on copper concentration in the overlying water were always lower than the effect thresholds measured for water-only exposures. These observations indicate that the particulate copper exposure pathway is the principal cause of toxicity (Campana et al., 2012).
ii) Comparison between measured and predicted sub-lethal effect concentrations calculated using logistic sigmoidal curves shows that the chronic exposure effect model based on the exposure to bio-available copper, calculated as a function of the dissolved and particulate copper concentration, the organism's feeding behaviour (ingestion rate) and physiology (uptake rate from water, assimilation efficiency of ingested particles), offers a good fit in predicting the copper toxic sub-lethal effect.
iii) In toxicity assessment, increasing importance is being placed on determining tissue metal residues-effect relationships that result from environmental exposure (dissolved and particulate sources). Following uptake, metals may partition within different subcellular tissues, be detoxified or excreted, depending on the accumulation pattern of a particular organism for a particular metal. Only the metabolically active fraction of metal contributes to toxicity. Our research also investigated the links between the subcellular metal partitioning and toxic effect to reproduction of the epibenthic amphipod Melita plumulosa and growth of the bivalve Tellina deltoidalis exposed to copper-contaminated sediments with varying properties. Stronger linear relationships were found for both organisms between the subcellular copper partitioning and organic carbon (OC)-normalised particulate copper concentrations, compared to copper concentrations in the water phase. This has important biological significance and highlights how most of the variability related to the reproduction of the amphipod and the growth rate of the bivalve can be explained by the increase of copper that is associated to the metabolically available fraction (MAF). These results provide further insight into the interaction between tissue residues and sub-lethal effects.
iv) Copper sub-lethal effect concentrations normalised to organic carbon content and particle size, obtained by amphipod, copepod and bivalve tests were compared to copper sediment quality guidelines derived from using species sensitivity distributions (SSDs) of copper effects data (Simpson et al., 2011). The derived SQGs vary in a predictable manner with changes in sediment particle size and organic carbon, and offer a significant improvement on the existing 'single value' SQG. Adequate protection for all benthic organisms is expected to be achieved for an OC-normalised copper concentration of 3.5 mg <63 µm Cu g-1 OC. Chronic EC10s calculated for Melita plumulosa and Nitocra spinipes were found 5.2 ± 2.2 and 4.8 ± 1.7 mg <63 µm Cu g-1 OC respectively (Campana et al., 2012) and highlighted the good agreement with the chronic guideline proposed. Results obtained from whole sediment toxicity tests applied to natural sediments using local organisms species (Tisbe battagliai and Scrobicularia plana), also confirm an adequate conservative level of protection for regulatory purpose offered by the proposed SQGs, also satisfactory for Spanish environment.
Conclusions
Compared to acute tests, sub-lethal and chronic tests offer a higher level of ecological realism due to the fact that exposure conditions are environmentally more representative and end points used, such as growth or reproduction, are regarded as more ecologically relevant. However, considerably more information is needed to predict sub-lethal and chronic effects of metals to benthic organisms, particularly on the chronic effects of dietary metals exposure (food and sediment ingestion pathway). The results obtained in this project made a more extensive sub-lethal effect data set available, which provides cause-effect information for copper in sediments with varying properties and underlines that dietary uptake to metals is a very significant exposure route for benthic organisms.
The provision of SQGs that better predict the effects of copper in sediment with varying properties and thus provide adequate protection against toxicity is very important for regulatory purpose and should be taken into consideration by environmental agencies and regulators.
SQGs tested for chronic exposures that vary in a predictable manner with changes in sediment physicochemical properties offer a significant improvement on the existing 'single value' SQGs.
Application of these SQGs to a local Spanish estuarine environment has confirmed a conservatory level of protection, satisfactory for the adequate protection of benthic organisms.
References
Campana, O., Simpson, S.L. Spadaro, D.A. Blasco, J., 2012. Sub-Lethal Effects of Copper to Benthic Invertebrates Explained by Sediment Properties and Dietary Exposure. Environ. Sci. Technol. 46, 6835-6842.
Simpson, S.L. Batley, G.E. Hamilton, I.L. Spadaro, D.A. 2011. Guidelines for copper in sediments with varying properties. Chemosphere 85, 1487-1495.
Contact details: Dr Olivia Campana, postdoctoral fellow.
Instituto de Ciencias Marinas de Andalucia CSIC - Spain
olivia.campana@icman.csic.es.