The estuarine geochemical reactivity of Zn isotopes and its relevance for the biomonitoring of anthropogenic Zn and Cd contaminations from metallurgical activities: Example of the Gironde fluvial-estuarine system, France

Zinc stable isotopes measurements by MC-ICP-MS, validated by laboratory intercalibrations, were performed on wild oysters, suspended particles and filtered river/estuarine water samples to provide new constraints for the use of Zn isotopes as environmental tracers. The samples selected were representative of the long range (400 km) transport of metal (Zn, Cd, etc.) contamination from former Zn-refining activities at Decazeville (i.e. δ66Zn > 1 ‰) and its phasing out, recorded during 30 years in wild oysters from the Gironde Estuary mouth (RNO/ROCCH sample bank). The study also addresses additional anthropogenic sources (urban and viticulture) and focuses on geochemical reactivity of Zn in the turbidity gradient and the maximum turbidity zone (MTZ) of the fluvial Gironde Estuary. In this area, dissolved Zn showed a strong removal onto suspended particulate matter (SPM) and progressive enrichment in heavy isotopes with increasing SPM concentrations varying from δ66Zn = -0.02 ‰ at 2 mg/L to +0.90 ‰ at 1310 mg/L. These signatures were attributed to kinetically driven adsorption due to strongly increasing sorption sites in the turbidity gradient and MTZ of the estuary. Oysters from the estuary mouth, contaminated sediments from the Lot River and SPM entering the estuary showed parallel historical evolutions (1979-2010) for Zn/Cd ratios but not for δ66Zn values. Oysters had signatures varying from δ66Zn = 1.43 ‰ in 1983 to 1.18 ‰ in 2010 and were offset by δ66Zn = 0.6 - 0.7 ‰ compared to past (1988) and present SPM from the salinity gradient. Isotopic signatures in river-borne particles entering the Gironde Estuary under contrasting freshwater discharge regimes during 2003-2011 showed similar values (δ66Zn ≈ 0.35 ± 0.03 ‰; 1SD, n=15), i.e. they were neither related to former metal refining activities at least for the past decade nor clearly affected by other anthropogenic sources. Therefore, the Zn isotopic signatures in Gironde oysters reflect the geochemical reactivity of Zn in the estuary rather than signatures of past metallurgical contaminations in the watershed as recorded in contaminated river sediments. The study also shows that the isotopic composition of Zn is strongly fractionated by its geochemical reactivity in the Gironde Estuary, representative of meso-macrotidal estuarine systems.

Site n°5. The Pertuis Breton (Bay of Biscay) France

1.This report presents the results of a field study conducted in the ECASA test site nOS in the Pertuis Breton, France. The site is located on the Atlantic West coasts. It is open to the bay of Biscay, but is slightly protected against westerly winds. The bay has been exploited by intertidal mussels culture for centuries. 2. Within the bay, mussels (Mytilus edulis) are cultivated either by the traditional pole technique, around the bay or on longlines in the centre of the bay. The area occupied by these longline s represents 250 ha, and the resulting annual production is 1 000 tonnes of mussels. The average depth at mid tide is of 13.8 m. The sediment is sandy, with a small fraction of mud. 3. The site is subject to several regular monitoring through the local implementation of national networks aiming at protecting the environment and marine resources, on pollutants (RNO), microbiological quality of the waters (REMI), phytoplanktonic toxic species (REPHY) and growth and mortality of molluscs (REMORA). Benthic macrofauna was studied in 1976. 4. Five sampling sations were chosen along a line, starting under the longlines, and at distances of 50, 100, 200, and 400 metres from the area cultivated. A reference station was chosen in a different direction at 2300 metres of the cultivated area. Sampling methods are described in the text. _Sediments were sampled for different analyses: grain size, content in organic matter, total organic carbon and nitrogen, and phytic pigments (chlorophyll a and phaeopigments). Redox were measured in cores. The macrofauna living into the sediment was also sampled. The water column was sampled for physical (temperature, transparency) and chemical parametres, including oxygen content, salinity, organic matter, dissolved nitrogen forms, phosphates and silicates. Results from benthic macrofauna surveys indicate that there were no significant differences between the different stations and the reference station, all being classified as slightly disturbed. The bay is submitted to freshwater runoffs from two adjacent rivers. 7. The sediment is slightly modified by the culture of bivalves. Total organic carbon, total nitrogen, Eh values and pheopigments were significantly higher under the trestles than in any other stations. Other stations often did not differ from the reference station. 8. The effects of shellfish culture on the water column were. However, it was observed a small decrease of the food available to the molluscs near the rearing 9. The DEB model was able to describe and predict adequately the growth of oysters, both in the Baie des Veys and in the Loch Creran. The parametres for its use in other environment are given, but a tuning of one parametre should be performed with the help of authors. 10. Among the indicators and models for use in are as of intertidal bivalve culture, it is recommended to use the sediment quality index, TOC (Total Organic Carbon), redox and pheopigments, in surficial sediment, AMBI for the macrofauna, chlorophyll a contents and nitrogen forms in the water column, and models describing the carrying capacity, filtration rate of molluscs, and a DEB model to predict the growth of molluscs.

Impacts of high-nitrate freshwater inputs on macrotidal ecosystems. I. Seasonal evolution of nutrient limitation for the diatom-dominated phytoplankton of the Bay of Brest (France)

The chemical factors (inorganic nitrogen, phosphate, silicic acid) that potentially or actually control primary production were determined for the Bay of Brest, France, a macrotidal ecosystem submitted to high-nitrate-loaded freshwater inputs (winter nitrate freshwater concentrations >700 mu M, Si:N molar ratio as low as 0.2, i.e. among the lowest ever published). Intensive data collection and observations were carried out from February 1993 to March 1994 to determine the variations of physical [salinity, temperature, photosynthetically active radiation (PAR), freshwater discharges] and chemical (oxygen and nutrients) parameters and their impacts on the phytoplankton cycle (fluorescence, pigments, primary production). With insufficient PAR the winter stocks of nutrients were almost nonutilized and the nitrate excess was exported to the adjacent ocean, due to rapid tidal exchange. By early April, a diatom-dominated spring bloom developed (chlorophyll a maximum = 7.7 mu g l(-1); primary production maximum = 2.34 g C m(-2) d(-1)) under high initial nutrient concentrations. Silicic acid was rapidly exhausted over the whole water column; it is inferred to be the primary limiting factor responsible for the collapse of the spring bloom by mid-May. Successive phytoplankton developments characterized the period of secondary blooms during summer and fall (successive surface chlorophyll a maxima = 3.5, 1.6, 1.8 and 1.0 mu g l(-1); primary production = 1.24, 1.18 and 0.35 g C m(-2) d(-1)). Those secondary blooms developed under lower nutrient concentrations, mostly originating from nutrient recycling. Until August, Si and P most likely limited primary production, whereas the last stage of the productive period in September seemed to be N limited instead, this being a period of total nitrate depletion in almost the whole water column. Si limitation of spring blooms has become a common feature in coastal ecosystems that receive freshwater inputs with Si:N molar ratios <1. The peculiarity of Si Limitation in the Bay of Brest is its extension through the summer period.

Prevalence and characterization of Salmonella spp. in three shellfish-harvesting areas in France

Shellfish farming is an important economic activity in the Brittany and Normandy regions. However, a part of the production sites corresponds to relatively sensitive areas where the presence of faecal microorganisms is a major concern for shellfish and constitutes a possible health risk. Indeed, shellfish bioaccumulates in their tissues pathogenic contaminants present in water and can cause food-borne diseases such as salmonellosis. During a two-year study, we evaluated the presence of faecal indicators, measured the prevalence of Salmonella spp., isolated and characterized Salmonella spp. from three French shellfish-harvesting areas (shellfish and sediment) and their watersheds (from river water samples).

Changes in the annual harmful algal blooms of Alexandrium minutum : effects of environmental conditions and drainage basin inputs in the Rance estuary (Brittany, France)

Time series of physico-chemical data and concentrations (cell L-1) of the toxic dinoflagellate Alexandrium minutum collected in the Rance macrotidal estuary (Brittany, France) were analyzed to understand the physico-chemical processes of the estuary and their relation to changes in bloom development from 1996 to 2009. The construction of the tidal power plant in the north and the presence of a lock in the south have greatly altered hydrodynamics, blocking the zone of maximum turbidity upstream, in the narrowest part of the estuary. Alexandrium minutum occurs in the middle part of the estuary. Most physical and chemical parameters of the Rance estuary are similar to those observed elsewhere in Brittany with water temperatures between 15–18 °C, slightly lowered salinities (31.8–33.1 PSU), low river flow rates upstream and significant solar radiation (8 h day-1). A notable exception is phosphate input from the drainage basin which seems to limit bloom development: in recent years, bloom decline can be significantly correlated with the decrease in phosphate input. On the other hand, the chemical processes occurring in the freshwater-saltwater interface do not seem to have an influence on these occurrences. The other hypotheses for bloom declines are discussed, including the prevalence of parasitism, but remain to be verified in further studies.

Determination of thresholds in marine molluscs as an alternative to the Environmental Quality Standards in marine water defined in the Water Framework Directive

The Water Framework Directive (WFD) establishes Environmental Quality Standards (EQS) in marine water for 34 priority substances. Among these substances, 25 are hydrophobic and bioaccumulable (2 metals and 23 organic compounds). For these 25 substances, monitoring in water matrix is not appropriate and an alternative matrix should be developed. Bivalve mollusks, particularly mussels (Mytilus edulis, Mytilus galloprovincialis), are used by Ifremer as a quantitative biological indicator since 1979 in France, to assess the marine water quality. This study has been carried out in order to determine thresholds in mussels at least as protective as EQS in marine water laid down by the WFD. Three steps are defined: - Provide an overview of knowledges about the relations between the concentrations of contaminants in the marine water and mussels through bioaccumulation factor (BAF) and bioconcentration factor (BCF). This allows to examine how a BCF or a BAF can be determined: BCF can be determined experimentally (according to US EPA or ASTM standards), or by Quantitative Activity-Structure Relationship models (QSAR): four equations can be used for mussels. BAF can be determined by field experiment; but none standards exists. It could be determined by using QSAR but this method is considered as invalid for mussels, or by using existing model: Dynamic Budget Model, but this is complex to use. - Collect concentrations data in marine water (Cwater) in bibliography for those 25 substances; and compare them with concentration in mussels (Cmussels) obtained through French monitoring network of chemicals contaminants (ROCCH) and biological integrator network RINBIO. According to available data, this leads to determine the BAF or the BCF (Cmussels /Cwater) with field data. - Compare BAF and BCF values (when available) obtained with various methods for these substances: BCF (stemming from the bibliography, using experimental process), BCF calculated by QSAR and BAF determined using field data. This study points out that experimental BCF data are available for 3 substances (Chlorpyrifos, HCH, Pentachlorobenzene). BCF by QSAR can be calculated for 20 substances. The use of field data allows to evaluate 4 BAF for organic compounds and 2 BAF for metals. Using these BAF or BCF value, thresholds in shellfish can be determined as an alternative to EQS in marine water.