An integrated approach for bioaccumulation assessment in mussels: towards the development of Environmental Quality Standards for biota

Bioecological Aspects and Heavy Metal Contamination of the Mollusk Donax denticulatus in the Colombian Caribbean Coastline

Donax denticulatus is a key mollusk for the ecology of sandy beaches, serving as a controller of organic matter, microorganisms, and as bioindicator of heavy metals pollution. The goal of this study was to characterize some ecological aspects of D. denticulatus and its relationship with the content of heavy metals in their tissue, in three beaches of the Caribbean coast of Colombia. The results showed the study populations were different in terms of morphological characteristics and density (Berrugas-Sucre < Cartagena-Bolívar < Riohacha-Guajira), but not in sexual proportion; although density was clearly related to beach occupancy by tourists. Analysis of metals revealed tissue concentrations varied depending on the location (Greater means: Hg = 0.018 ± 0.004 in Riohacha; Pb = 0.110 ± 0.060 in Berrugas and Cd = 0.040 ± 0.010 µg/g in Cartagena). No relationships were found between morphometric variables and heavy metals content. Principal components analysis highlighted Riohacha for presenting differences respecting to Bocagrande and Berrugas in terms of physicochemical water parameters such as pH, temperature, salinity, dissolved oxygen and conductivity. Results suggest tourism rather than environmental pollution could be a sensitive factor for biota survival in Caribbean beaches.

Blue mussels (Mytilus edulis spp.) as sentinel organisms in coastal pollution monitoring: A review

The blue mussel (Mytilus spp.) is widely used as a bioindicator for monitoring of coastal water pollution (mussel watch programs). Herein we provide a review of this study field with emphasis on: the suitability of Mytilus spp. as environmental sentinels; uptake and bioaccumulation patterns of key pollutant classes; the use of Mytilus spp. in mussel watch programs; recent trends in Norwegian mussel monitoring; environmental quality standards and background concentrations of key contaminants; pollutant effect biomarkers; confounding factors; particulate contaminants (microplastics, engineered nanomaterials); climate change; harmonization of monitoring procedures; and the use of deployed mussels (transplant caging) in pollution monitoring. Lastly, the overall state of the art of blue mussel pollution monitoring is discussed and some important issues for future research and development are highlighted.

Integrated wetlands for food production

The widespread use of compound pelleted feeds and chemical fertilizers in modern food production contribute to a vast amount of residual nutrients into the production system and adjacent ecosystem are major factors causing eutrophication. Furthermore, the extensive development and application of chemical compounds (such as chemical pesticides, disinfectants and hormones used in enhancing productivity) in food production process are hazardous to the ecosystems, as well as human health. These unsustainable food production patterns cannot sustain human living in the long run. Wetlands are perceived as self-decontamination ecosystems with high productivities. This review gives an overview about wetlands which are being integrated with food production processes, focusing on aquaculture.

Relationships between polychlorinated biphenyls in molluscs, hydrological characteristics and human pressures, within Basque estuaries (northern Spain)

Interannual variability of polychlorinated biphenyls (PCBs), measured in the soft tissues of Mytilus galloprovincialis mussels and Crassostrea gigas oysters, collected from estuarine waters within the Basque Country (Bay of Biscay), are investigated. Samples were collected in the autumn, between 2002 and 2011. Sites located within the ports of Bilbao and Pasaia showed the highest PCBs concentrations in molluscs; the lowest were observed in the mouth of the Oka estuary, an area of low population and industrial activity. Congener profiles of PCBs in the tissues of molluscs reveal the predominance of hexachlorobiphenyls (CB153 and CB138). In addition, redundancy analysis has shown that residence time, river flow and a 'pressure index' explain 57% of the variability in the PCB congener concentrations (the higher the values of these variables, the higher the concentration). Finally, Σ7PCB median concentrations in molluscs and sediments, collected from nearby sampling sites, were found to be moderately correlated (r(2)=0.513, p<0.01).

Screening of chemicals for human bioaccumulative potential with a physiologically based toxicokinetic model

Human bioaccumulative potential is an important element in the risk assessment of chemicals. Due to the high number of synthetic chemicals, there exists the need to develop prioritisation strategies. The purpose of this study was to develop a predictive tool for human bioaccumulation risk assessment that incorporates not only the chemical properties of the compounds, but also the processes that tend to decrease the concentration of the compound such as metabolisation. We used a generic physiologically based toxicokinetic model that based on in vitro human liver metabolism data, minimal renal excretion and a constant exposure was able to assess the bioaccumulative potential of a chemical. The approach has been analysed using literature data on well-known bioaccumulative compounds and liver metabolism data from the ECVAM database and a subset of the ToxCast phase I chemical library-in total 94 compounds covering pharmaceuticals, plant protection products and industrial chemicals. Our results provide further evidence that partitioning properties do not allow for a reliable screening criteria for human chemical hazard. Our model, based on a 100% intestinal absorption assumption, suggests that metabolic clearance, plasma protein-binding properties and renal excretion are the main factors in determining whether bioaccumulation will occur and its amount. It is essential that in vitro metabolic clearance tests with metabolic competent cell lines as well as plasma protein-binding assays be performed for suspected bioaccumulative compounds.

Sublethal toxic effects in a generic aquatic ecosystem

The dynamical behaviour of an aquatic ecosystem stressed by limiting nutrients and exposure to a conservative toxicant is investigated. The ecosystem downstream of a pollution source consists of: nutrients, biotic pelagic and benthic communities, and detritus pools in the water body and on the sediment. The long-term dynamic behaviour of this system is analysed using bifurcation theory. A reference state is defined and our aim is to quantify the effects of toxicological (toxic exposure), ecological (feeding, predation, competition) and environmental stressors (nutrient supply, dilution rate). To that end we calculate the ranges of stress levels where the long-term dynamics (equilibrium, oscillatory or chaotic behaviour) is qualitatively the same. In this way we obtain levels of toxicological loading where the abundances of all populations are the same as in the reference case, the no-effect region. We will also calculate toxic exposure levels that do not lead to a change in the composition of the ecosystem, and therefore its structure, with respect to the reference unexposed situation, but where population abundances and internal toxicant concentrations may have been changed quantitatively. The model predicts that due to indirect effects even low sublethal toxic exposure can lead to catastrophic changes in the ecosystem functioning and structure, and that the long-term sensitivities of oligotrophic and eutrophic systems to toxic stress are different.