Michael Gilek

Issues and practices in the use of effects data from FREDERICA in the ERICA Integrated Approach

The ERICA Integrated Approach requires that a risk assessment screening dose rate is defined for the risk characterisation within Tiers 1 and 2. At Tier 3, no numerical screening dose rate is used, and the risk characterisation is driven by methods that can evaluate the possible effects of ionising radiation on reproduction, mortality and morbidity. Species sensitivity distribution has been used to derive the ERICA risk assessment predicted no-effect dose rate (PNEDR). The method used was based on the mathematical processing of data from FRED (FASSET radiation effects database merged with the EPIC database to form FREDERICA) and resulted in a PNEDR of 10 microGy/h. This rate was assumed to ascribe sufficient protection of all ecosystems from detrimental effects on structure and function under chronic exposure. The value was weighed against a number of points of comparison: (i) PNEDR values obtained by application of the safety factor method, (ii) background levels, (iii) dose rates triggering effects on radioactively contaminated sites and (iv) former guidelines from literature reviews. In Tier 3, the effects analysis must be driven by the problem formulation and is thus highly case specific. Instead of specific recommendations on numeric values, guidance on the sorts of methods that may be applied for refined effect analysis is provided and illustrated.

Bioaccumulation kinetics of PCB 31, 49 and 153 in the blue mussel, Mytilus edulis L. as a function of algal food concentration

Abstract Uptake and depuration kinetics of a tri, a tetra and a hexa chlorobiphenyl (IUPAC no. 31, 49 and 153) in Baltic Sea blue mussels ( Mytilus edulis L.) were determined at different algal food rations. Differences in food concentration markedly influenced the water pumping and filtration rates of the mussels. This indicates that physiologically-based (PB) rather than simple equilibrium partitioning bioaccumulation models are more appropriate to use when describing the influence of differences in food ration on PCB bioaccumulation in mussels. A PB bioaccumulation model was used to describe the gradual shift in PCB exposure with increasing food concentration from apparently dissolved to food-associated PCBs. This change in the route of PCB exposure was owing to the combined effect of PCB partitioning to algae and regulation of the rates of water pumping and algae filtration by the mussels. Differences in food ration significantly influenced the PCB uptake rate, whereas PCB depuration was mainly unaffected by differences in algal food concentration. The observed differences in PCB uptake were primarily caused by the influence of food ration on the physiological activity of the mussels and only to a lesser degree by changes in PCB bioavailability owing to PCB partitioning between water and algal food. Calculated bioaccumulation factors (BAFs) varied up to two orders of magnitude over the food ration interval studied. Maximum BAFs of 4.92 10 5 , 1.10 10 6 , and 6.91 10 6 ml g −1 DW were obtained for PCB 31, 49 and 153, respectively, at a food concentration of 0.076 mg particulate organic carbon per litre. Thus, differences in food ration affects both the route and the rate of contaminant exposure and uptake. This emphasises the importance of controlling particulate food concentrations when designing bioaccumulation and toxicity studies with suspension-feeding organisms. Long-term changes in food availability may also affect contaminant accumulation and cycling in field populations of suspension-feeding mussels.

Influence of body size on the uptake, depuration, and bioaccumulation of polychlorinated biphenyl congeners by Baltic Sea blue mussels, Mytilus edulis

The present study was designed to examine the influence of body size on the bioaccumulation of polychlorinated biphenyl (PCB) congeners by Baltic Sea blue mussels, Mytilus edulis L. This was done, firstly, by establishing the relationship (as a power function: PCB tissue conc = a tissue dry wtb) between tissue concentration and body weight for seven PCB congeners (International Union of Pure and Applied Chemistry No. 52, 101, 105, 118, 138, 153, and 180) in field sampled mussels; and, secondly, by assessing the influence of body weight on the uptake clearance coefficients, the depuration rate coefficients and the calculated bioaccumulation factors (BAFs) of three 14C-labelled PCB congeners (IUPAC No. 31, 49, 153) in mechanistic kinetic experiments. Both the background tissue concentrations of PCB 138, PCB 153 and PCB 180 and the predicted BAF values in the kinetic experiments correlated negatively with body weight (b=-0.17 and-0.31, respectively). Of the two kinetic rate coefficients examined, only the uptake clearance rate showed weight dependency (b=-0.32, i.e. negative correlation with body weight), whereas depuration rates were unaffectd by body weight. Uptake clearance rates and BAFs adjusted for body weight increased with the octanol/water partition coefficient (Kow) of the congener, whereas depuration rates dectreased with Kow. These observations suggest that size-dependent bioaccumulation of hydrophobic organic contaminants (HOCs) in suspension-feeding bivalves is driven by size-related differences in uptake rate, although several other mechanisms may also affect bioaccumulation in natural mussel beds (e.g. sizerelated differences in lipid content, production, and contaminant exposure). From an ecotoxicological perspective size-dependent bioaccumulation implies not only that variability due to body size differences has to be dealt with in experimental designs, but also that several ecological factors such as size-specific predation and shifts in population structure may affect HOC cycling by dense populations of bivalve suspensionfeeders.

Effects of eutrophication on contaminant cycling in marine benthic systems

Abstract Effects of inputs of organic matter were studied on bioavailability and cycling of hydrophobic organic contaminants (HOCs) in benthic ecosystems of the Baltic and Kattegat Seas. In laboratory experiments, effects of microalgae additions were studied on the bioaccumulation of HOCs (PCBs and PAHs) by the blue mussel Mytilus edulis, the brittle star Amphiura filiformis, and the polychaete Nereis diversicolor. Contrary to the equilibrium partitioning theory, bioaccumulation was proportional to the concentrations of algae and organic carbon. This was attributed to the high nutritional quality of the algal organic carbon and suggests that feeding rather than equilibrium partitioning governed bioaccumulation in these species. In the field, annual mass fluxes of PCBs in blue mussels and in brittle stars were estimated, as well as contaminant transfer to higher trophic levels. Our results suggest that: i) Eutrophication processes may contribute to increase HOC accumulation in benthic species. ii) Temporal variation in the quantity and quality of organic carbon needs to be considered when assessing contamination of benthic systems. iii) Macrofaunal feeding activities are important for the benthic-pelagic coupling of HOCs. iv) Bioturbation enhances the release of HOCs from sediment to overlying water.

Tissue differences, dose-response relationship and persistence of DNA adducts in blue mussels (Mytilus edulis L.) exposed to benzo[a]pyrene

Baltic Sea blue mussels (Mytilus edulis) were experimentally exposed to the genotoxic model substance benzo[a]pyrene (B[a]P) to study DNA adduct formation. The specific aims were (a). to examine where in the mussels the DNA adducts were formed, in gills or digestive gland; (b). to study the dose-response relationship between B[a]P exposure and DNA adduct formation; and (c). to examine the persistence of the formed adducts. A Scope for growth (SFG) study was also run to compare physiological responses of the mussels with the degree of DNA adduct formation. In an initial dose-response experiment, the mussels were exposed to 0, 5, 50, and 100 microg/l of tritium labelled B[a]P under semi-static conditions for 4 days, and thereafter the bioaccumulation of B[a]P and DNA adduct formation in different tissues was determined using liquid scintillation counting and 32P-postlabelling analysis, respectively. In a following exposure-depuration experiment, mussels were exposed to 17 microg/l of radiolabelled B[a]P under semi-static conditions for 6 days. B[a]P accumulation and DNA adduct formation were determined during the exposure, and B[a]P elimination and persistence of DNA adducts were studied during 28 days of depuration in uncontaminated water. The results revealed large tissue differences in DNA adduct formation. DNA adduct levels were not elevated in the digestive gland of the mussels at any exposure concentration (0-100 microg/l), even though the highest B[a]P tissue concentrations were found in the digestive gland (1.0+/-0.1 mg B[a]P/g tissue dry wt at 100 microg/l, mean+/-SE, n=12). DNA adducts were on the other hand formed in the gills, with the highest levels found in mussels exposed to 50 and 100 microg B[a]P/l, and a dose dependent increase in adduct levels (from 1.6 to 5.9 nmol adducts/mol nucleotides) from 0 to 50 microg B[a]P/l. In gills, DNA adduct levels increased with time during the 6-day exposure period in the exposure-depuration experiment, and then persisted for at least 2 weeks after exposure cessation while B[a]P tissue levels exhibited a rapid decrease (half-life of 8 days). No significant differences were observed in SFG between the control and exposed groups. Since DNA adducts exhibited a relatively high persistence in gills compared to B[a]P tissue concentrations, they seem to be a more integrated measure of genotoxic exposure than only chemical analysis of the contaminant bioaccumulation. The results also suggest that if using analysis of DNA adducts in M. edulis for monitoring purposes, analysis of gills in addition to the more commonly used digestive gland should be taken into consideration.

Addressing uncertainties in the ERICA Integrated Approach

Like any complex environmental problem, ecological risk assessment of the impacts of ionising radiation is confounded by uncertainty. At all stages, from problem formulation through to risk characterisation, the assessment is dependent on models, scenarios, assumptions and extrapolations. These include technical uncertainties related to the data used, conceptual uncertainties associated with models and scenarios, as well as social uncertainties such as economic impacts, the interpretation of legislation, and the acceptability of the assessment results to stakeholders. The ERICA Integrated Approach has been developed to allow an assessment of the risks of ionising radiation, and includes a number of methods that are intended to make the uncertainties and assumptions inherent in the assessment more transparent to users and stakeholders. Throughout its development, ERICA has recommended that assessors deal openly with the deeper dimensions of uncertainty and acknowledge that uncertainty is intrinsic to complex systems. Since the tool is based on a tiered approach, the approaches to dealing with uncertainty vary between the tiers, ranging from a simple, but highly conservative screening to a full probabilistic risk assessment including sensitivity analysis. This paper gives on overview of types of uncertainty that are manifest in ecological risk assessment and the ERICA Integrated Approach to dealing with some of these uncertainties.

An ecosystem model of the environmental transport and fate of carbon-14 in a bay of the Baltic Sea, Sweden

The environmental transport and fate of a hypothetical discharge of radioactive 14C from the Swedish final repository for radioactive operational waste (SFR) was investigated using an ecosystem m ...

Unravelling science-policy interactions in environmental risk governance of the Baltic Sea : Comparing fisheries and eutrophication

Interactions between scientific assessments and management decision-making are key determinants for the efficiency of environmental risk governance. This applies particularly to marine ecosystems like the Baltic Sea, where fisheries and eutrophication pose serious threats connected to environmental, social and economic aspects of sustainability. Using contemporary science-policy theory, this paper investigates structures, challenges and prospects of science-policy interfaces connected to fisheries and eutrophication governance in the Baltic Sea. We analyse and compare the two cases with respect to two aspects: first the design and organisational structures of the institutional frameworks and second the management of uncertainties and stakeholder disagreements in the two risk cases. The analyses reveal how conventional natural science-based policy-making is insufficient for the requirements of complex environmental governance arenas like fisheries and eutrophication. Both cases show a high, almost exclusive, dependence on science-based advice regarding the organisational and institutional structures of their science-policy interfaces. They also expose remarkable differences with respect to stakeholder disagreements about the interplay between science, other knowledge and policy decisions. In the eutrophication case, consensual science-based advice shaped policy decisions in a comparatively uncomplicated manner. In fisheries by contrast, stakeholder disagreements and different interpretations of scientific uncertainties created serious confusions about the basic role of science in policy. We identify and discuss factors contributing to the observed differences in the science-policy interplay of fisheries and eutrophication management. Our results highlight a misleading conceptual understanding of science-policy interfaces between the normative idea of objective, science-based policy-making and the political challenges of dealing with the social aspects of uncertainty and stakeholder disagreements in environmental risk governance.

Vertical patterns in biomass, size structure, growth and recruitment of Mytilus edulis in an archipelago area in the northern baltic sea proper

Although dwarfed by the low saline conditions, the blue mussel (Mytilus edulis L.) is a biomass dominant in coastal areas of the Baltic Sea proper, owing to the lack of invertebrate predators and c ...

Physiological performance and general histology of the blue mussel, Mytilus edulis L., from the Baltic and North seas

A physiological approach has been proposed for studying the ecological consequences of diseases and parasitism in bivalve molluscs. We investigated effects of some naturally occurring non-lethal pa ...