Exposure of the marine deposit feeder Hydrobia ulvae to sediment spiked with LAS congeners

10 páginas, 4 figuras, 5 tablas.The lethal and sub-lethal toxicity of LAS congeners to the mollusc gastropod Hydrobia ulvae were assessed in spiked sediment bioassays. This complements the little knowledge available to date on mixture effects in the sediment compartment. The LAS homologues joint effect was concentration additive (∑TUi = 0.8–1). As opposed to the 10-d LC10 based on the sediment associated LAS concentration (91–330 mg/kg) which was independent of the homologue chain length, the LC10 based on the dissolved LAS fraction (0.804–0.068 mg/L) decreased as the homologue chain length increased from 10 to 13 carbons. The quantitative structure-activity relationship (QSAR) derived from these data was log (1/LC10 (mol/L)) = 0.64 log Kow + 4.40 (n = 5; r2 = 0.76; s = 0.24). It showed an apparent higher toxicity compared to the typical QSAR for polar narcosis in water-only systems probably due to the simultaneous exposure of the snail to LAS through the dissolved and the sediment associated fractions. The egestion rate of the surviving snails recovered after few days' exposure (1-d NOEC: 40–107 mg/kg, 9-d NOEC: 65–190 mg/kg) which suggests that the organisms were able to acclimate to LAS during the exposure.This research was supported by the European Commission through the FP6 program (EST Marie Curie Fellowship) and it was performed in the framework of the RISICO project (MEST-CT-2004-505182). We also acknowledge the financial support of ERASM, ECOSOL and PETRESA.Peer reviewe

Influence of the reproductive cycle on cytochrome P450 levels in the sea star Coscinasterias muricata

[article extract] Located in the mitochondria and endoplasmic reticulum, enzymes of the cytochrome P450 superfamily are involved in critical physiological processes including biosynthesis and metabolism of steroids, fatty acids and prostaglandins. In addition to metabolism of endogenous compounds, cytochrome P450 (P450) enzymes are involved in the biotransformation/detoxification of some organic xenobiotic compounds, including polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). P450 reactions often lead to more water-soluble and generally less toxic metabolites that are further metabolised by phase II reactions, for example glutathione S-transferases, to form more readily excretable products. However, some P450 reactions involving exogenous compounds result in products that are more toxic than their parent compound, a process known as bioactivation. Changes in levels or activities of detoxification enzymes, such as total P450 and its isoforms, in response to organic contaminant exposure have been previously used in sea stars as specific biomarkers of this contaminant class. Therefore, thorough examination of the natural fluctuations of these enzymes must be undertaken to allow comparison with exposed organisms. The response of total P450 has been shown to be influenced by factors including season, temperature, organism gender, nutritional status and size in both marine vertebrates and invertebrates

Equilibrium partitioning theory to predict the sediment toxicity of the anionic surfactant C(12)-2-LAS to Corophium volutator.

The study of the effect of the sorption of linear alkylbenzene sulfonates (LAS) on the bioavailability to marine benthic organisms is essential to refine the environmental risk assessment of these compounds. According to the equilibrium partitioning theory (EqP), the effect concentration in water-only exposure will be similar to the effect concentration in the sediment pore water. In this work, sorption and desorption experiments with two marine sediments were carried out using the compound C(12)-2-LAS. The effect of the sediment sorption on the toxicity of benthic organisms was studied in water-only and in sediment bioassays with the marine mud shrimp Corophium volutator. In addition, three common spiking methods were tested for its application in the toxicity tests, as well as the stability of the surfactant during the water-only and sediment-water test duration. LC50 values obtained from water-only exposure showed a good correspondence with the pore water concentrations calculated from the sorption and desorption isotherms in the spiked sediments

Effect of sediment properties on the sorption of C12-2-LAS in marine and estuarine sediments

Linear alkylbenzene sulfonates (LAS) are anionic high production volume surfactants used in the manufacture of cleaning products. Here, we have studied the effect of the characteristics of marine and estuarine sediments on the sorption of LAS. Sorption experiments were performed with single sediment materials (pure clays and sea sand), with sediments treated to reduce their organic carbon content, and with field marine and estuarine sediments. C12-2-LAS was used as a model compound. Sorption to the clays montmorillonite and kaolinite resulted in non-linear isotherms very similar for both clays. When reducing the organic content, sorption coefficients decreased proportionally to the fraction removed in fine grain sediments but this was not the case for the sandy sediment. The correlation of the sediment characteristics with the sorption coefficients at different surfactant concentrations showed that at concentrations below 10 microg C12-2-LAS/L, the clay content correlated better with sorption, while the organic fraction became more significant at higher concentrations

Exposure of the marine deposit feeder Hydrobia ulvae to sediment associated LAS

Linear Alkylbenzene Sulfonates (LAS) effects (mortality, egestion rate, behaviour) on the marine deposit feeder Hydrobia ulvae were assessed in whole-sediment and water-only systems. The results were combined with a bioenergetic-based kinetic model of exposure pathways to account for the observed toxicity. The 10-d LC50 value based on the freely dissolved fraction was 9.3 times lower in spiked sediment (0.152 +/- 0.001 (95% CI) mg/L) than in water-only (1.390 +/- 0.020 (95% CI) mg/L). Consequently, the actual 10-d LC50 value (208 mg/kg) was overestimated by the Equilibrium Partitioning calculation (1629 mg/kg). This suggests that the sediment associated LAS fraction was bioavailable to the snails. It could also be due to modifications in physiological parameters in absence of sediment, the organism natural substrate

Marine risk assessment: Linear alkylbenzenesulponates (LAS) in the North Sea

The fate of linear alkylbenzenesulponates (LAS) in estuaries and coastal areas of the North Sea has been characterized with simple environmental models. The predicted, concentration range in the estuaries around the North Sea, (0.9-9 pg LAS l-1) was validated by monitoring data (1-9 µg LAS l-1). In offshore sites of the North Sea, it is estimated - and experimentally verified for a few sites that the LAS concentration is below analytical detection limit (i.e., 0.5 µg LAS l-1). The effects of LAS on marine organisms have been reviewed. For short-term acute tests, there was no significant difference (p = 0.83) between the mean LC50 values of freshwater and marine organisms (mainly pelagic species tested, 4.1 and 4.3 mg LAS l-1, respectively). For longer-term chronic tests, it appeared that the sensitivity (mean no-observed effect concentration (NOEC value) of marine and freshwater organisms (0.3 and 2.3 mg LAS l-1, respectively) was significantly different (pt-test = 0.007). The predicted no-effect-concentrations (PNEC) were 360 and 31 µg LAS l-1, for freshwater and marine pelagic communities, respectively. Given that the maximum expected estuarine and marine concentrations are 3 to > 30 times lower than the PNEC, the risk of LAS to pelagic organisms in these environments is judged to be low

Sorption-desorption kinetics and toxic cell concentration in marine phytoplankton microalgae exposed to Linear Alkylbenzene Sulfonate

Linear Alkylbenzene Sulfonates (LAS) are ubiquitous surfactants. Traces can be found in coastal environments. Sorption and toxicity of C12-LAS congeners were studied in controlled conditions (2-3500 µg C12LAs/L) in five marine phytoplanktonic species, using standardized methods. IC50 values ranged from 0.5 to 2 mg LAS/L. Sorption of 14C12-6 LAS isomer was measured at environmentally relevant trace levels (4 µg/L) using liquid scintillation counting. Steady-state sorption on algae was reached within 5 h in the order dinoflagellate > diatoms > green algae. The sorption data, fitted a L-type Freundlich isotherm, indicating saturation. Desorption was rapid but a low LAS fraction was still sorbed after 24 h. Toxic cell concentration was 0.38 +/- 0.09 mg/g for the studied species. LAS toxicity results from sorption on biological membranes leading to non-specific disturbance of algal growth. Results indicate that LAS concentrations in coastal environments do not represent a risk for these organisms

LAS degradability by marine biofilms derived from seawater in Spain and Sweden

Marine biofilms were established on glass beads with or without deliberate pre-exposure to LAS (20μg/L) in Spain (Cadiz) and Sweden (Kristineberg). The ability of each community to mineralize LAS (100μg/L) was then assessed in biometers at four experimental temperatures (between 6 and 21°C). Genetic diversity and biomass of the biofilms were assessed by genetic fingerprinting (DGGE) and direct bacterial counts. With biofilms from Sweden, where LAS was not detected in seawater (n=3), deliberate pre-exposure to LAS resulted in lower genetic diversity and higher mineralization rate constant; however, with biofilms from Spain, where 6.4±3.9μgLAS/L (n=3) was measured during the colonization, pre-exposure did not affect the bacterial community. Bacterial acclimation therefore appeared to have been induced at environmental concentrations <6μgLAS/L. Environmental pre-exposure was not a pre-requisite for featuring the full consortia of LAS degraders in the biometers. The mineralization rate was described using an Arrhenius equation at experimental temperatures within the typical annual range; however, they departed from this model below this range. © 2011 Elsevier Inc.This research was performed as part of the RISICO project, which was supported by the European Commission through the FP6 program (MEST-CT-2004-505182). We also acknowledge the financial support of ERASM and ECOSOL.Peer Reviewe