The great melting pot. Common sole population connectivity assessed by otolith and water fingerprints

Quantifying the scale and importance of individual dispersion between populations and life stages is a key challenge in marine ecology. The common sole (Solea solea), an important commercial flatfish in the North Sea, Atlantic Ocean and the Mediterranean Sea, has a marine pelagic larval stage, a benthic juvenile stage in coastal nurseries (lagoons, estuaries or shallow marine areas) and a benthic adult stage in deeper marine waters on the continental shelf. To date, the ecological connectivity among these life stages has been little assessed in the Mediterranean. Here, such an assessment is provided for the first time for the Gulf of Lions, NW Mediterranean, based on a dataset on otolith microchemistry and stable isotopic composition as indicators of the water masses inhabited by individual fish. Specifically, otolith Ba/Ca and Sr/Ca profiles, and delta C-13 and delta O-18 values of adults collected in four areas of the Gulf of Lions were compared with those of young-of-the-year collected in different coastal nurseries. Results showed that a high proportion of adults (>46%) were influenced by river inputs during their larval stage. Furthermore Sr/Ca ratios and the otolith length at one year of age revealed that most adults (similar to 70%) spent their juvenile stage in nurseries with high salinity, whereas the remainder used brackish environments. In total, data were consistent with the use of six nursery types, three with high salinity (marine areas and two types of highly saline lagoons) and three brackish (coastal areas near river mouths, and two types of brackish environments), all of which contributed to the replenishment of adult populations. These finding implicated panmixia in sole population in the Gulf of Lions and claimed for a habitat integrated management of fisherie

Difference of mercury bioaccumulation in red mullets from the north-western Mediterranean and Black seas

International audienceThe relationships between total mercury (Hg) concentration and stable nitrogen isotope ratio (delta N-15) were evaluated in Mullus barbatus barbatus and M. surmuletus from the Mediterranean Sea and M. barbatus ponticus from the Black Sea. Mercury concentration in fish muscle was six times higher in the two Mediterranean species than in the Black Sea one for similar sized animals. A positive correlation between Hg concentration and delta N-15 occurred in all species. Increase in Hg concentration with delta N-15 was high and similar in the two Mediterranean fishes and much lower in the Black Sea species. Since this was neither related to trophic level difference between species nor to methylmercury (MeHg) concentration differences between the north-western Mediterranean and the Black Sea waters, we suggested that the higher primary production of the Black Sea induced a dilution of MeHg concentration at the base of the food webs. (c) 2009 Elsevier Ltd. All rights reserved

A dynamic and mechanistic model of PCB bioaccumulation in the European hake (Merluccius merluccius)

Bioaccumulation is difficult to document because responses differ among chemical compounds, with environmental conditions. and physiological processes characteristic of each species. We use a mechanistic model, based on the Dynamic Energy Budget (DEB) theory, to take into account this complexity and study factors impacting accumulation of organic pollutants in fish through ontogeny. The bioaccumulation model proposed is a comprehensive approach that relates evolution of hake PCB contamination to physiological information about the fish, such as diet, metabolism, reserve and reproduction status. The species studied is the European hake (Merluccius merluccius, L 1758). The model is applied to study the total concentration and the lipid normalised concentration of 4 PCB congeners in male and female hakes from the Gulf of Lions (NW Mediterranean sea) and the Bay of Biscay (NE Atlantic ocean). Outputs of the model compare consistently to measurements over the life span of fish. Simulation results clearly demonstrate the relative effects of food contamination, growth and reproduction on the PCB bioaccumulation in hake. The same species living in different habitats and exposed to different PCB prey concentrations exhibit marked difference in the body accumulation of PCBs. At the adult stage, female hakes have a lower PCB concentration compared to males for a given length. We successfully simulated these sex-specific PCB concentrations by considering two mechanisms: a higher energy allocation to growth for females and a transfer of PCBs from the female to its eggs when allocating lipids from reserve to eggs. Finally, by its mechanistic description of physiological processes, the model is relevant for other species and sets the stage for a mechanistic understanding of toxicity and ecological effects of organic contaminants in marine organisms

Differential biomagnification of PCB, PBDE, Hg and Radiocesium in the food web of the European hake from the NW Mediterranean

International audienceConsumption of marine organisms represents one of the main exposure sources of contaminants for human populations. To obtain a global view of the contamination in commercial fish in the NW Mediterranean Sea, we analysed four types of priority contaminants (PCBs, PBDEs, Hg and 137Cs) in the European hake, Merluccius merluccius, from the Gulf of Lions in relation with organism's trophic level (δ 15N). All contaminants presented a significant increase in concentration in hake muscle with trophic level. However, obvious differences between contaminants were evidenced. Biomagnification factors (BMF and FWMF) along the hake food web were higher for Hg and CB-153 than for BDE-47 and 137Cs, and increase in contaminant concentration with trophic level occurred at different rates depending on contaminants. Such differences of biomagnification patterns can be related to physico-chemical properties of the different contaminants. © 2012 Elsevier Ltd

Population pharmacokinetics and dosing simulations of amoxicillin in obese adults receiving co-amoxiclav

International audienceBackground Pneumonia, skin and soft tissue infections are more frequent in obese patients and are most often treated by co-amoxiclav, using similar dosing regimens to those used for non-obese subjects. No data are available on amoxicillin pharmacokinetics among obese subjects receiving co-amoxiclav. Materials and methods Prospective, single-centre, open-label, non-randomized, crossover pharmacokinetic trial having enrolled obese otherwise healthy adult subjects. A first dose of co-amoxiclav (amoxicillin/clavulanate 1000/200 mg) was infused IV over 30 min, followed by a second dose (1000/125 mg) administered orally, separated by a washout period of ≥24 h. We assayed concentrations of amoxicillin by a validated ultra HPLC–tandem MS technique. We estimated population pharmacokinetic parameters of amoxicillin by non-linear mixed-effect modelling using the SAEM algorithm developed by Monolix. Results Twenty-seven subjects were included in the IV study, with 24 included in the oral part of the study. Median body weight and BMI were 109.3 kg and 40.6 kg/m2, respectively. Amoxicillin pharmacokinetics were best described by a two-compartment model with first-order elimination. Mean values for clearance, central volume, intercompartmental clearance and peripheral volume were, respectively, 14.6 L/h, 9.0 L, 4.2 L/h and 6.4 L for amoxicillin. Oral bioavailability of amoxicillin was 79.7%. Amoxicillin Cmax after oral administration significantly reduced with weight (P = 0.013). Dosing simulations for amoxicillin predicted that most of the population will achieve the pharmacodynamic target of fT>MIC ≥40% with the regimen of co-amoxiclav 1000/200 mg (IV) or 1000/125 mg (oral) q8h for MICs titrated up to 0.5 mg/L (IV) and 1 mg/L (oral). Conclusions Pharmacokinetic/pharmacodynamic goals for amoxicillin can be obtained in obese subjects

Influences of Bioavailability, Trophic Position, and Growth on Methylmercury in Hakes (Merluccius merluccius) from Northwestern Mediterranean and Northeastern Atlantic

Methylmercury (MeHg) determinations in hake, its food-chain, and the surrounding waters and sediments allowed us to show that the higher length or age normalized mercury concentrations of Northwestern Mediterranean (Gulf of Lions: GoL) muscle hakes compared to its Northeastern Atlantic (Bay of Biscay: BoB) counterpart are due to both biotic and abiotic differences between their ecosystems. Bioenergetic modeling reveals that the slower growth rate of Mediterranean hake favors the MeHg bioaccumulation in the fish muscle and explains most of the difference between GOL and BoB hake populations. In addition, the waters of the Mediterranean hake habitat favor a higher MeHg exposition, due to the upper position of the thermohalocline, where MeHg is formed. Furthermore, we show that, within the Mediterranean hake population, a major increase in the biomagnification power (the slope of the relationships between logMeHg and δ15N), from 0.36 up to 1.12, occurs when individuals enter adulthood, resulting from the combined effects of lowering growth rate and change in feeding habits. Finally, δ15N normalized Hg concentrations indicate that the highest Hg concentrations are for hake from the shelf edge and the lowest are for hake from the Rhône prodelta area, suggesting a lower Hg bioavailability in inshore environments, consistent with MeHg distributions in water, sediment, and preys. © 2012 American Chemical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Trophic structure in the Gulf of Lions marine ecosystem (north-western Mediterranean Sea) and fishing impacts

International audienceThe Gulf of Lions ecosystemwas described using the Ecopath mass-balancemodel to characterise its structure and functioning and to examine the effects of themultispecific fisheries operating in this area. The model is composed of 40 compartments, including 1 group of seabirds, 2 groups of cetaceans, 18 groups of fish, 12 groups of invertebrates, 5 groups of primary producers, detritus and discards. Input datawere based on several recurrent scientific surveys, two alternative datasets for fishing data, stock assessment outputs, stomach content analyses and published information. Results showed that the functional groups were organised into five trophic levels with the highest one represented by dolphins, anglerfish, Atlantic bluefin tuna, European hake and European conger. European pilchard and European anchovy dominated in terms of fish biomass and catch. Other fish with high biomass such as Atlantic mackerel and blue whiting were highly important in the food web. Seabirds, dolphins and cuttlefish-squids represented keystone species. Important coupled pelagic-demersal-benthic interactions were described. The 7 different fisheries analysed were operating at mean trophic levels situated between 2.6 for small artisanal boats, and 4.1 for purse seines (>24 m) targeting large pelagic fish, indicating an intensively exploited ecosystem. Large trawlers (24-40 m) had the highest impact on most of the groups considered; while purse seines (12-24 m) targeting small pelagic fish had the lowest impact. Preliminary results highlighted the importance of data sources for further ecosystem and fisheries analyses and management scenarios