Understanding weathering processes plays a critical role in oil spill forensics, which is based on the comparison of the distributions of selected compounds assumed to be recalcitrant and/or have consistent weathering transformations. Yet, these assumptions are based on limited laboratory and oil-spill studies. With access to additional sites that have been oiled by different types of oils and exposures, there is a great opportunity to expand on our knowledge about these transformations. Here, we demonstrate the effects of photooxidation on the overall composition of spilled oils caused by natural and simulated sunlight, and particularly on the often used polycyclic aromatic hydrocarbons (PAHs) and the biomarker triaromatic steranes (TAS). Both laboratory and field data from oil released from the Macondo well oil following the Deepwater Horizon disaster (2010), and heavy fuel-oil from the Prestige tanker spill (2002) have been obtained to improve the data interpretation of the typical fingerprinting methodology.

Using a calibrated bio-optical model we determined that the optical water quality conditions in several nitrogen-impaired embayments and in one unimpaired system were within the range of values known to support eelgrass growth. We also used the model to identify a range of light requirements for eelgrass (Zostera marina). Higher eelgrass light requirements, expressed as a percentage of surface-incident irradiance, corresponded with higher sediment organic matter content. These results corroborated findings by previous studies which indicate a generalized relationship: seagrasses growing in turbid conditions with poorer water and sediment quality have higher light requirements than those growing in less degraded conditions. The mechanistic reason for the variation in light requirements is still not completely explained and cannot be attributed to a single independent variable. Varying light requirement have important implications for eelgrass protection and should be considered when setting restoration targets for eelgrass in water quality and nitrogen remediation programs.

Spills of heavy oil (HO) have an adverse effect on marine life. We have demonstrated previously that exposure to HO by fertilized eggs of the pufferfish (Takifugu rubripes) induces neural disruption and behavioral abnormality in early-hatched larvae. Here, two kinds of polycyclic aromatic hydrocarbons, pyrene and phenanthrene, were selected to examine their toxic effects on larval behavior of another pufferfish species (T. niphobles). Larvae exposed to pyrene or phenanthrene exhibited no abnormalities in morphology. However, those exposed to pyrene but not phenanthrene swam in an uncoordinated manner, although their swimming distance and speed were normal. The optic tectum, a part of the midbrain, of pyrene-exposed larvae did not grow to full size. Thus, these findings are indicated that pyrene might be a contributor to the behavioral and neuro-developmental toxicity, although there is no indication that it is the only compound participating in the toxicity of the heavy oil mixture.

Oil–shoreline interaction (or “beaching” as commonly referred to in literature) is an issue of major concern in oil spill modeling, due to the significant environmental, social and economic importance of coastal areas. The present work studies the improvement of the representation of beaching brought by the introduction of the Oil Holding Capacity approach to estimate oil concentration on coast, along with new approaches for coast type assignment to shoreline segments and the calculation of permanent oil attachment to the coast. The above were tested for the Lebanon oil spill of 2006, using a modified version of the open-source oil spill model MEDSLIK-II. The modified model results were found to be in good agreement with field observations for the specific case study, and their comparison with the original model results denote the significant improvement in the fate of beached oil brought by the proposed changes.

Pesticides are frequently detected in estuaries among the pollutants found in estuarine and coastal areas and may have major ecological consequences. They could endanger organism growth, reproduction or survival. In the context of high mortality outbreaks affecting Pacific oysters, Crassostrea gigas, in France since 2008, it appears of importance to determine the putative effects of pesticides on oyster susceptibility to infectious agents. Massive mortality outbreaks reported in this species, mainly in spring and summer, may suggest an important role played by the seasonal use of pesticides and freshwater input in estuarine areas where oyster farms are frequently located. To understand the impact of some pesticides detected in French waters, their effects on Pacific oyster hemocytes were studied through short-term in vitro experiments. Bivalve immunity is mainly supported by hemocytes eliminating pathogens by phagocytosis and producing compounds including lysosomal enzymes and antimicrobial molecules. In this study, oyster hemocytes were incubated with a mixture of 14 pesticides and metaldehyde alone, a molecule used to eliminate land mollusks. Hemocyte parameters including dead/alive cells, nonspecific esterase activities, intracytoplasmic calcium, lysosome number and activity and phagocytosis were monitored by flow cytometry. No significant effect of pesticides tested at different concentrations was reported on oyster hemocytes maintained in vitro for short-term periods in the present study. It could be assumed that these oyster cells were resistant to pesticide exposure in tested conditions and developing in vivo assays appears as necessary to better understand the effects of polluants on immune system in mollucks.

This study examined the influence of increasing temperatures in spring and summer on biochemical biomarkers in Mytilus galloprovincialis mussels sampled from Bizerte lagoon (northern Tunisia). Spatial and seasonal variations in a battery of seven biomarkers were analyzed in relation to environmental parameters (temperature, salinity and pH), physiological status (condition and gonad indexes), stress on stress (SoS) and chemical contaminant levels (heavy metals, PAHs and PCBs) in digestive glands. Integrated Biological Response (IBR) was calculated using seven biomarkers (AChE, BPH, MXR, GST, CAT, MDA and MT). Seasonal variations in biological response were determined during a critical period between spring and summer at two sites, where chemical contamination varies by a factor of 2 for heavy metals and a factor 2.5 for PAHs. The analysis of a battery of biomarkers was combined with the measurement of physiological parameters at both sites, in order to quantify a maximum range of metabolic regulation with a temperature increase of 11°C between May and August. According to our results, the MT, MDA, CAT and AChE biomarkers showed the highest amplitude during the 11°C rise, while the BPH, GST, and MXR biomarkers showed the lowest amplitude. Metabolic amplitude measured with the IBR at Menzel Abdelrahmen - the most severely contaminated station - revealed the highest metabolic stress in Bizerte lagoon in August, when temperatures were highest 29.1°C. This high metabolic rate was quantified for each biomarker in the North African lagoon area and confirmed in August, when the highest IBR index values were obtained at the least-contaminated Site 2 (IBR= 9,6) and the most-contaminated site 1 (IBR=19,6). The combined effects of chemical contamination and increased and salinity temperatures in summer appear to induce a highest metabolic adaptation response and can therefore be used to determine thresholds of effectiveness and facilitate the interpretation of monitoring biomarkers. This approach, applied during substantial temperature increases at two sites with differing chemical contamination, is a first step toward determining an EAC (Environmental Assessment Criteria) threshold in a North African lagoon.

The release of polycyclic aromatic hydrocarbons (PAHs) into the environment has increased very substantially over the last decades leading to high concentrations in sediments of contaminated areas. To evaluate the consequences of long-term chronic exposure to PAHs, zebrafish were exposed, from their first meal at 5 days post fertilisation until they became reproducing adults, to diets spiked with three PAH fractions at three environmentally relevant concentrations with the medium concentration being in the range of 4.6–6.7 μg g−1 for total quantified PAHs including the 16 US-EPA indicator PAHs and alkylated derivatives. The fractions used were representative of PAHs of pyrolytic (PY) origin or of two different oils of differing compositions, a heavy fuel (HO) and a light crude oil (LO). Fish growth was inhibited by all PAH fractions and the effects were sex specific: as determined with 9-month-old adults, exposure to the highest PY inhibited growth of females; exposure to the highest HO and LO inhibited growth of males; also, the highest HO dramatically reduced survival. Morphological analysis indicated a disruption of jaw growth in larvae and malformations in adults. Intestinal and pancreatic enzyme activities were abnormal in 2-month-old exposed fish. These effects may contribute to poor growth. Finally, our results indicate that PAH mixtures of different compositions, representative of situations encountered in the wild, can promote lethal and sublethal effects which are likely to be detrimental for fish recruitment.

A natural sediment spiked with three individual polycyclic aromatic hydrocarbons (PAHs; pyrene, phenanthrene and benzo[a]pyrene) was used to expose zebrafish embryos and larvae during 4 days. The total PAH concentration was 4.4 μg g−1 which is in the range found in sediment from contaminated areas. Quantification of metabolites in the larvae after exposure confirmed the actual contamination of the larvae and indicated an active metabolism especially for pyrene and benzo[a]pyrene. After a transfer in a clean medium, the larvae were reared to adulthood and evaluated for survival, growth, reproduction, and behavior. Measured endpoints revealed a late disruption of growth (appearing at 5 months) and a trend toward a lower reproductive ability. Adults of embryos exposed to sediment spiked with PAHs displayed lethargic and/or anxiety-like behaviors. This latter behavior was also identified in offspring at larval stage. All together, these effects could have detrimental consequences on fish performances and contribution to recruitment.

A multibiomarker approach was developed to evaluate the juvenile European flounder responses to a complex mixture of 9 polycyclic aromatic hydrocarbons (PAHs) and 12 polychlorinated biphenyls (PCBs). Exposure was performed through contaminated food pellets displaying: (1) PAH and PCB levels similar to those detected in the heavily polluted Seine estuary, respectively in sediments and in flatfish and (2) ten times these concentrations. Several biomarkers of the immune system (e.g., lysozyme concentration and gene expression of complement component C3 and TNF-receptor), DNA damage (e.g., Comet assay), energetic metabolism (e.g., activity of cytochrome C oxidase), detoxification process (e.g., cytochrome P450 1A1 expression level: CYP1A1; betaine homocysteine methyl transferase expression level: BHMT) were investigated after 14 and 29 days of contamination, followed by a 14-days recovery period. After 29 days of contamination, the detoxification activity (CYP1A1 expression level) was positively correlated with DNA damages; the increase of the BHMT expression level could also be related to the detoxification process. Furthermore, after the recovery period, some biomarkers were still upregulated (i.e., CYP1A1 and BHMT expression levels). The immune system was significantly modulated by the chemical stress at the two concentration levels, and the lysozyme appeared to be the most sensitive marker of the mixture impact.

Context and objectives Microorganisms are ubiquitous in soil, air, and water ecosystems, where they are key players of ecosystem services. Microbial ecotoxicology is an emerging interdisciplinary area of research which aims at investigating the impact of human activities on the diversity, abundance, and activity of microorganisms. In return, the results of such investigations hold the promise to provide novel ways of assessing in a sensitive way the impacts of diverse environmental disturbances and subsequent ecosystem responses. Thus and although the term itself is yet rarely encountered in the scientific literature, microbial ecotoxicology already addresses an increasing political and societal demand. In the French scientific landscape, which often mimics the famous (but sometimes indigestible) “mille-feuilles” pastry, microbial ecotoxicologists are scattered across many different research centers belonging to different research organizations and universities. This research field has thus lacked any visibility and remained unorganized until now. Formal organization of scientific activities may be considered a typical “froggies” concern (or ailment). Nevertheless, it is rather surprising that scientific journals and significant international conferences specifically devoted to microbial ecotoxicology have been missing so far, especially considering the plethoric range of journals and congresses devoted to microbial ecology and ecotoxicology. With these considerations in mind, the idea of organizing the French research community of microbial ecologists around concepts of ecotoxicology made its way, with the aim of sharing the necessity to overcome artificial boundaries that prevent progress in this promising field.