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.

We present here the first mercury speciation study in the water column of the Southern Ocean, using a high-resolution south-to-north section (27 stations from 65.50 degrees S to 44.00 degrees S) with up to 15 depths (0-4440 m) between Antarctica and Tasmania (Australia) along the 140 degrees E meridian. In addition, in order to explore the role of sea ice in Hg cycling, a study of mercury speciation in the "snow-sea ice-seawater" continuum was conducted at a coastal site, near the Australian Casey station (66.40 degrees S; 101.14 degrees E). In the open ocean waters, total Hg (Hg-T) concentrations varied from 0.63 to 2.76 pmol L-1 with "transient-type" vertical profiles and a latitudinal distribution suggesting an atmospheric mercury source south of the Southern Polar Front (SPF) and a surface removal north of the Subantartic Front (SAF). Slightly higher mean Hg-T concentrations (1.35 +/- 0.39 pmol L-1) were measured in Antarctic Bottom Water (AABW) compared to Antarctic Intermediate water (AAIW) (1.15 +/- 0.22 pmol L-1). Labile Hg (Hg-R) concentrations varied from 0.01 to 2.28 pmol L-1, with a distribution showing that the Hg-T enrichment south of the SPF consisted mainly of Hg-R (67 +/- 23%), whereas, in contrast, the percentage was half that in surface waters north of PFZ (33 +/- 23%). Methylated mercury species (MeHgT) concentrations ranged from 0.02 to 0.86 pmol L-1. All vertical MeHgT profiles exhibited roughly the same pattern, with low concentrations observed in the surface layer and increasing concentrations with depth up to an intermediate depth maximum. As for Hg-T, low mean MeHgT concentrations were associated with AAIW, and higher ones with AABW. The maximum of MeHgT concentration at each station was systematically observed within the oxygen minimum zone, with a statistically significant MeHgT vs Apparent Oxygen Utilization (AOU) relationship (p < 0.001). The proportion of Hg-T as methylated species was lower than 5% in the surface waters, around 50% in deep waters below 1000 m, reaching a maximum of 78% south of the SPF. At Casey coastal station Hg-T and Hg-R concentrations found in the "snow-sea ice-seawater" continuum were one order of magnitude higher than those measured in open ocean waters. The distribution of Hg-T there suggests an atmospheric Hg deposition with snow and a fractionation process during sea ice formation, which excludes Hg from the ice with a parallel Hg enrichment of brine, probably concurring with the Hg enrichment of AABW observed in the open ocean waters. Contrastingly, MeHgT concentrations in the sea ice environment were in the same range as in the open ocean waters, remaining below 0.45 pmol L-1. The MeHgT vertical profile through the continuum suggests different sources, including atmosphere, seawater and methylation in basal ice. Whereas Hg-T concentrations in the water samples collected between the Antarctic continent and Tasmania are comparable to recent measurements made in the other parts of the World Ocean (e. g., Soerensen et al., 2010), the Hg species distribution suggests distinct features in the Southern Ocean Hg cycle: (i) a net atmospheric Hg deposition on surface water near the ice edge, (ii) the Hg enrichment in brine during sea ice formation, and (iii) a net methylation of Hg south of the SPF. (C) 2011 Elsevier Ltd.All rights resrved.

Recent findings on the distribution of methylated mercury (MeHgT) in waters have highlighted the importance of organic carbon remineralization on the production of these compounds in the open ocean. Here, we present the first time-series (20 monthly samplings between July 2007 and May 2009) of high-resolution vertical profiles (10–12 depths in a 2350m water column) of MeHgT distributions in an open ocean environment, the Ligurian Sea (North-western Mediterranean Sea). Concentrations varied within the sub-picomolar range (general mean: 0.30±0.17pmolL−1, n=214) with the lowest values at the surface, increasing with depth up to the oxygen minimum zone, and decreasing slowly at greater depth. Concentrations in the surface waters never exceeded 0.15pmolL−1, while the highest concentrations (up to 0.82pmolL−1) were associated to the hypoxycline during the autumn bloom. A detailed vertical MeHgT profile reveals a “double-peak” pattern, coincidental with the two microbial layers described by Tanaka and Rassoulzadegan (2002), the so-called “microbial food web” in the euphotic zone (<100m) and the “microbial loop” in the aphotic zone (>100m). Temporal variations in the MeHgT abundance and distribution in the water column were linked to seasonality. The highest MeHgT concentrations were found in the oxygen minimum zone during the period of stratification, and coincide with the greatest abundance of nano- and picophytoplankton (cyanobacteria, nanoflagellates, etc.) in the euphotic layer. None of our deep MeHgT measurements (∼100m above the sea bottom) revealed a significant sedimentary source of MeHgT. We explored the correlation between MeHgT concentrations and the apparent oxygen utilization, a proxy of organic matter remineralization, over the study period. Results of this study strengthen the hypothesis that net mercury methylation in the open ocean occurs in the water column, is linked to organic matter regeneration, and is promoted by the presence of small-sized nano- and picophytoplankton, that dominate under oligotrophic conditions.

Seasonal snow is an active media and an important climate factor that governs nutrient transfer in Arctic ecosystems. Since the snow stores and transforms nutrients and contaminants, it is of crucial importance to gain a better understanding of the dynamics of contaminant cycling within the snowpack and its subsequent release to catchments via meltwater. Over the course of a two-month field study in the spring of 2008, we collected snow and meltwater samples from a seasonal snowpack in Ny-Ålesund, Norway (78°56′N, 11°52′E), which were analyzed for major inorganic ions and some organic acids, as well as total, dissolved, bioavailable mercury (THg, DHg, BioHg, respectively) and monomethylmercury (MMHg) species. We observe a seasonal gradient for ion concentrations, with surface samples becoming less concentrated as the season progressed. A significant negative correlation between BioHg and MMHg was observed in the snowpack. MMHg was positively and significantly correlated to methanesulfonate concentrations. Based on these results, we propose a new model for aerobic methylation of mercury involving species in the dimethylsulfoniopropionate cycle.

Imposex and butyltin concentrations were assessed in Hexaplex trunculus, Conus mediterraneus, Cyclope neritea and Nassarius mutabilis from Menzel Jemil, and H. trunculus and Stramonita haemastoma from the Bizerta channel. All females of the five species exhibited the characteristic development of male sex organs (penis and/or vas deferens). In Menzel Jemil, H. trunculus and C. mediterraneus exhibit similar imposex levels and were most affected (VDS reading 3-4). The development of a bud penis or a vas deferens sequence behind the right ocular tentacle was reported in Cyclope neritea and N. mutabilis (VDS 1). The concentration of tributyltin (TBT) was similar for the four species. The monobutyltin (MBT) was only detected in C. mediterraneus while the dibutyltin (DBT) was found in all gastropods at similar proportions as TBT. In the Bizerta channel, imposex levels were similar in both H. trunculus and S. haemastoma but imposex degree was higher in H. trunculus. This finding was confirmed by higher TBT concentration recorded in female of H. trunculus. These results suggested that H. trunculus is the more suitable bioindicator for monitoring TBT pollution.

We present high‐resolution vertical profiles of methylated mercury (MeHgT = monomethylmercury + dimethylmercury) concentrations in the water column of the open and marginal areas of the Mediterranean Sea. MeHgT concentrations ranged from <0.015 pmol L−1 to 0.430 pmol L−1 (n = 130), with maximal concentrations occurring within the maxima of oxygen consumption. Within the most biologically active zone (0‐600 m), the MeHgT vertical profiles exhibited a nutrient‐like pattern. The MeHgT vs. phosphate relationships were highly significant (p < 0.001), whichever the station. We argue that most of the MeHgT in the water column originates from in situ methylation of inorganic HgII associated with the regeneration of the organic matter. The demethylation of MeHgT as water ages seems responsible for the MeHgT distribution in deep waters. The influences of the methylmercury inputs from the atmosphere, rivers, and coastal or abyssal sediments appear to be locally restricted.

We have assessed for the first time the current status of tributyltin (TBT) contamination in Hexaplex trunculus along Tunisian coastal waters. Two sampling campaigns have been performed in July 2004 and July 2007 at seven different sites. The snails were analyzed for imposex status, i.e. Imposex incidence, Relative Penis Length Index (RPLI) and Vas Deferens Sequence Index (VDSI), followed by the quantification of butyltins in their tissues. Imposex was detected in six populations from the 2004 samples and in five populations from the 2007 samples. The imposex incidence ranged from 0 (no imposex) to 100%, the RPLI from 0 to 56.7 and the VDSI from 0 to 4.4. TBT was also detected in six populations in 2004 and five populations in 2007. The concentrations ranged from 1.5 to 73.7 ng Sn g(-1) dw in 2004 samples and from 1.2 to 23.9 ng Sn g(-1) dw in 2007 samples. Temporal comparison of the data indicates some evidence of imposex recovery in most affected populations. Improvements in reduced body concentrations of TBT in both sexes were also seen in most stations. These TBT concentrations were only significantly correlated to imposex indices in samples from 2007 (r > 0.8, n = 7, p < 0.05). The present results will serve as a reference for long-term monitoring of butyltin contamination in the Tunisian coast, where TBT restrictions were not yet implemented.

A method based on hydride generation with cryogenic trapping and atomic fluorescence detection was developed that is capable of determining both inorganic Se species (SeIV and SeVI) while at sea. Evaluation of the system for optimal performance was made for each stage of the analysis and detection sequence, as well as for the SeVI reduction step. A detection limit of 0.4 ng L−1 Se in a 10 mL sample was achieved using this method. Precision was better than 3.5% for 25, 100, and 1000 ng L−1 SeIV standard solutions. Accuracy was determined by recovery studies using natural samples and a certified reference seawater (NASS-5).

Sixty samples were collected in June 1996 at regular intervals within the Seine estuary in France in order to study the arsenic (As) behavior in response to climatic and hydrologic conditions leading to major events in chlorophyll activity, anoxia, turbidity, and salinity. It was determined that arsenate (As5, 15–23 nM) is still the dominant chemical form of dissolved As in the upper, estuary. A concentration of up to 37 nM was observed in the high turbidity zone at the freshwater-seawater interface, presumably a result of pumping and remineralization of plankton particles that develop at salinities >10. The formation of arsenite (As3) was related to two processes: anoxia in the upper estuary and primary production in the superoxygenated, lower estuary. Dimethyl arsenic (DMA) concentrations (0 to 2.2 nM) were not directly correlated with chlorophyll content, but rather with oxygenation rates. Monomethyl arsenic (MMA) concentrations were low. Dissolved organoarsenic concentrations refractory to the formation of volatile hydrides showed high concentrations in the river estuary (1 to 6 nM), and their degradation was probably the cause of DMA and MMA and ultimately of the recycling of dissolved inorganic As. The remineralization of particulate arsenic (AsP) in the high turbidity zone at the freshwater-seawater interface, was apparent once AsP concentrations were normalized with respect to aluminium. This remineralization process, even though it does not exclude the possibility of intra-estuarine As inputs, could account for a major part of the high dissolved total As concentration observed in this specific zone, both in the Seine and other estuaries.

Despite optimistic forecasts by various scientists after regulatory measures were taken in the 1980s, coastal tributyltin (TBT) contamination is still a major problem. The present study concerning Corsica (Western Mediterranean) shows that contamination is not limited to harbour areas, but extends along the coast, involving protected nature reserves. The concentrations measured in harbours, which can reach 200 ng TBT l−1, tend to incriminate both pleasure craft and ferries providing regular service between the island and the continent. Contamination as high as 7 ng TBT l−1 has been measured in waters of the Scandola nature reserve, which is quite excessive given the no effect concentrations (NOEC) for marine fauna are around 1–2 ng TBT l−1. The inadequacy of current regulations and their application are a major factor in this situation.

Three sampling cruises were conducted in the Seine Estuary from 1993 to 1995 in varying hydrological and seasonal conditions. The site included all of the lower part of the river under the influence of tidal dynamics and the dilution plume in the Baie de Seine. Chemical speciation of arsenic showed high seasonal variations, especially in September when AsIII represented around 50% of dissolved arsenic. The inclusion of organoarsenic compounds not accessible to direct analysis by hydride generation required preliminary mineralisation of the samples. The ratio of dissolved to particulate arsenic distribution was controlled mainly by the iron content of particles. Biological activity had an influence on chemical speciation and thus on the partition coefficient (KD10−3=6±1 in September and 12±0.9 in February). The zone of conservative mixing used for Seine River flow calculations was limited to a salinity range of approximately 10–30. Dissolved arsenic concentrations extrapolated to null salinities were lower during the high-water period because of dilution (17.6±1.1nM), and maximal during the low-water period in summer (35.7±0.9nM). Mean arsenic export to the English Channel was estimated at 33.2±6Tyr−1 for dissolved arsenic. Observation of an arsenic output greater than the upstream input, as well as a simultaneous increase in dissolved and particulate arsenic concentrations during the mixing of freshwater with seawater, strongly suggested the existence of an important intra-estuarine source of arsenic, either of industrial origin or related to the transport and diagenesis of marine sediments.

Fifteen years ago, France took regulatory measures to limit the use of organotin compounds in antifouling paints for the protection of boat hulls. France was the first country to take these emergency steps, which were intended to defend the oyster-farming industry. Since then, the regulations have been confirmed on several occasions, most recently in October 1992.

Tributyltin (TBT) contamination of marine organisms collected in the open sea or in deep seawaters has been considered in several studies but not the contamination levels in these waters far from pollutant sources. This study conducted in June 1998 measured TBT concentrations in the open sea in the northwestern part of the Mediterranean. Samples were obtained in surface waters as well as along three vertical profiles between 25 and 2500 m. The analytical and sampling techniques used were calibrated to be significant far a concentration of 0.01 ng L-1 TBT ions. Contamination of surface waters was as high as 0.47 ng L-1 20 km from shore and never lower than 0.08 ng L-1 in the open sea. Contamination of abyssal deep waters reached a maximum of 0.04 ng L-1 at a depth of 1200 m and was always significant at 2500 m. A comparison of the vertical profiles of TBT and salinity allowed assumptions to be made about the source of contamination. The presence of TBT in deep waters was attributed to the circulation of water masses during winter, while the vertical transport of particulate matter was considered to be of little importance. Contrary to results for coastal experiments, the half-life of TBT in this oligotrophic environment was estimated to be several years. The ubiquity and persistence of TBT in these waters is a new source of concern for environmentalists.

Il y a quinze ans, la France prenait des mesures reglementaires pour restreindre l'usage des composes organostanniques dans les peintures antisalissures utilisees pour la protection des coques de bateaux. Il s'agissait alors d'une reaction d'urgence face au probleme vital pose a l'ostreiculture francaise. La France etait le premier pays a prendre de telles dispositions. Depuis, la reglementation a ete confirmee a plusieurs reprises, en dernier lieu par le decret n°92-1074 du 2 octobre 1992. Quinze ans plus tard, ou en sommes nous ? La campagne de mesure des composes organostanniques dans l'eau de mer, conduite par l'IFREMER de juillet a septembre 1997 a permis de faire le point de la situation. La contamination des cotes francaises reste preoccupante. Pour de nombreuses installations portuaires les mesures montrent des sources de contamination persistantes. Les concentrations mesurees en zone cotiere a l'exterieur des installations portuaires, excedent trop souvent les concentrations toxiques reconnues. Soixante quinze pour cent des mesures restent superieures au seuil de 1 ng.1-1 pour lequel des effets toxiques sur certaines especes marines sont prouves.

The arsenic (As) cycle in the marine environment is known to be sensitive to biological activity. Within the scope of the National Coastal Oceanography Program, we undertook a specific study of the behaviour of this element in a water column on the continental shelf of the Bay of Biscay off the Gironde estuary during two oceanographic cruises conducted in May 1994 and May 1995. Various chemical forms were measured: arsenite (As3), at-senate (As5), monomethylarsenic (MMA), dimethylarsenic (DMA) and dissolved total As after ultraviolet mineralization. The net flux of total As from the Gironde estuary was evaluated as well as its effect on the concentration in surface marine waters. The vertical profiles in the coastal zone during a period of active primary production confirmed a certain analogy between arsenates and phosphates as well as the formation of As3 and DMA. The importance of organoarsenic species not directly accessible to the formation of volatile hydrides is demonstrated. Their presence modifies assessments, reducing the deficit of dissolved total As in the euphotic layer to just 5 %. For particles, the As content in phytoplankton was estimated at 6 mu g.g(-1) compared to 20 to 30 mu g.g(-1) in iron- and aluminium-rich terrigenous particles. These results do not invalidate the role of phytoplankton in the speciation of dissolved As but indicate that their involvement in vertical transfers was apparently not predominant in the zone under study. (C) Elsevier, Paris.

The extent of tributyltin (TBT) contamination of the Bay of Brest, resulting from the use of TBT-containing antifouling paints, has been assessed from the results of analyses of more than 150 sediment and water samples taken during 1992-1994. As expected, TBT concentrations in sediments were highest (1-21 mu g . g(-1)) in areas close to the naval dockyards, the commercial port and ship repair facilities, but were also high at the marina despite the ban on TBT paint use on small boats. TBT was readily detectable in bottom sediments throughout the bay, even in the deeper regions. Concentrations of dissolved TBT showed the same pattern of distribution : high (5-50 ng . l(-1)) close to the ship facilities and marina and lower (1-5 ng . l(-1)) elsewhere. A simulation model of TBT transport demonstrates that the contamination of the bay results from three sources of TBT, the naval area, the commercial port and the marina. The factors likely to govern future levels of TBT pollution in the Brest area are discussed.