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Coastal marine sediments can be either major scrubbers or eutrophication contributors to surface waters. Standard methods for direct measurement of nutrient fluxes at the sediment-water interface do not consider hydrodynamic forcing although several ex-situ studies suggest that sediment resuspension can dramatically increase dissolved fluxes. We provide a new model to quantify dissolved phosphate (PO 4 3−) resuspension flux (J R) based on physical representation of its identified components: diffusion stimulation by exposure of deeper sediment layer with higher PO 4 3− concentration in the porewater (J D), pore water mixing with overlying water (J M) and net adsorption/desorption from suspended sediments (J K). This approach was applied to field data from a Seine intertidal mudflat periodically submitted to millimetric erosion. On a tidal scale, the model output reveals a J R of 272.3 ± 360.0 μmol m−2 h−1 (± 52% from parameter uncertainty), well above flux calculated by application of Fick's first law (0.15 ± 0.85 μmol m−2 h−1) or by ex situ core incubation (40.8 μmol m−2 h−1). Iron bound phosphorus within suboxic layers buffers PO 4 3− concentrations in superficial sediments leading to negligible contributions of J D and J M to total fluxes. Conversely, J K appears to be the main exchange pathway, even though improvements in turbidity measurement would allow this term to be defined more precisely. Correction required to enhance and control model robustness are described. These results show the importance of considering the dissolved PO 4 3− resuspension flux in dynamic environments. • Original model for PO 4 3− resuspension flux calculation from in situ estuarine data. • Mean resuspension flux was 272.3 ± 360.0 μmol P m−2 h−1 on a tidal scale. • Desorption pathway is critical for its magnitude and model improvement perspectives. • Standard methods underestimate PO 4 3− benthic flux in dynamic environments. [ABSTRACT FROM AUTHOR]

This numerical modeling study (i) assesses the influence of the sediment erosion process on the sediment dynamics and subsequent morphological changes of a mixed-sediment environment, the macrotidal Seine estuary, when non-cohesive particles are dominant within bed mixtures (non-cohesive regime), and (ii) investigates respective contributions of bedload and suspended load in these dynamics. A three dimensional (3D) process-based morphodynamic model was set up and run under realistic forcings (including tide, waves, wind, and river discharge) during a 1-year period. Applying erosion homogeneously to bed sediment in the non-cohesive regime, i.e., average erosion parameters in the erosion law (especially the erodibility parameter, E 0), leads to higher resuspension of fine sediment due to the presence of coarser fractions within mixtures, compared to the case of an independent treatment of erosion for each sediment class. This results in more pronounced horizontal sediment flux (two-fold increase for sand, +30% for mud) and erosion/deposition patterns (up to a two-fold increase in erosion over shoals, generally associated with some coarsening of bed sediment). Compared to observed bathymetric changes, more relevant erosion/deposition patterns are derived from the model when independent resuspension fluxes are considered in the non-cohesive regime. These results suggest that this kind of approach may be more relevant when local grain-size distributions become heterogeneous and multimodal for non-cohesive particles. Bedload transport appears to be a non-dominant but significant contributor to the sediment dynamics of the Seine Estuary mouth. The residual bedload flux represents, on average, between 17 and 38% of the suspended sand flux, its contribution generally increasing when bed sediment becomes coarser (can become dominant at specific locations). The average orientation of residual fluxes and erosion/deposition patterns caused by bedload generally follow those resulting from suspended sediment dynamics. Sediment mass budgets cumulated over the simulated year reveal a relative contribution of bedload to total mass budgets around 25% over large erosion areas of shoals, which can even become higher in sedimentation zones. However, bedload-induced dynamics can locally differ from the dynamics related to suspended load, resulting in specific residual transport, erosion/deposition patterns, and changes in seabed nature. [ABSTRACT FROM AUTHOR]

Coastal and estuarine nurseries are composed of habitats with different biotic and abiotic features. Quantifying the contribution of different habitats within nurseries to juvenile fish feeding would help identify those that are essential in the completion of their life cycle, by providing food resources that maximise growth and survival. Essential habitats for four bentho-demersal fish species (whiting, sea bass, plaice and common sole) in an estuarine nursery were identified using gut contents and stable isotopes. Habitats differed in isotopic ratios and benthic communities. The estuarine gradient defined the macrofauna communities and sources of organic matter used by primary consumers. Trophic niche overlaps and trophic contribution of habitats highlighted that the species used both intertidal and subtidal habitats as feeding grounds. Flatfish were local feeders and fed on prey available mainly in the habitat in which they were caught, suggesting feeding behaviour that required little energy for movement. Sea bass were concentrated in upstream habitats, with intertidal mudflats contributing for nearly half of its diet. Whiting had an ubiquitous feeding strategy, suggesting that it may target prey with the most energetic gain in the habitats. Hence, habitats were used simultaneously during the same season or asynchronously throughout the year by the juvenile fish studied, suggesting no preference for a specific habitat at the community scale. Finally, both trophic tracers demonstrated the trophic importance of intertidal mudflats, especially for the sea bass and common sole, with contributions up to the half and two-third of their diet respectively. Graphical abstract [ABSTRACT FROM AUTHOR]

Productive and ecologically highly valuable ecosystems, macrotidal estuaries are also characterised by complex habitat and connectivity dynamics driven by tidal and freshwater influence. Organisms living in these constantly changing systems have to match their movement patterns to the shifting habitat mosaic using available windows of connectivity to access habitat patches of interest. This appears particularly important for the juvenile stages of many fish species colonising shallow and intertidal areas of the estuaries as summer nurseries. We apply tools from landscape ecology to investigate the estuarine habitat and connectivity dynamics on the example of juvenile seabass (Dicentrarchus labrax). We test under which conditions spatio-temporal bottlenecks to estuarine nursery colonisation may emerge for this species in a human-modified estuary. Combining a hydrodynamic model of the Seine estuary with remote sensing data allows us to capture structural changes in habitat availability and connectivity at the estuarine scale and at a fine spatio-temporal resolution. With chronological least-cost modelling of successive tidal steps, we assess patterns of nursery accessibility and estimate tidal colonisation fronts for different mobility scenarios. We show that, at certain hydrological conditions, tidal water level variation causes local disruptions of habitat availability and connectivity, creating temporary bottlenecks for seabass juveniles' movement. Fish mobility appears determinant for their vulnerability to these connectivity disruptions. Our approach allows for quantitative assessment and visualisation of riverscape complexity related to tidal dynamics. It is applicable to other highly dynamic ecosystems, where the mobile nature of connectivity and habitats needs to be integrated into conservation and management planning. [ABSTRACT FROM AUTHOR]

Phytoplankton primary production varies considerably with environmental parameters especially in dynamic ecosystems like estuaries. The aim of this study was to investigate short-term primary production along the salinity gradient of a temperate estuary over the course of 1 year. The combination of carbon incorporation and fluorescence methods enabled primary production estimation at short spatial and temporal scales. The electron requirement for carbon fixation was investigated in relation with physical-chemical parameters to accurately estimate primary production at high frequency. These results combined with the variability of the photic layer allowed the annual estimation of primary production along the estuary. Phytoplankton dynamics was closely related to salinity and turbidity gradients, which strongly influenced cells physiology and photoacclimatation. The number of electrons required to fix 1 mol of carbon (C) was ranged between 1.6 and 25 mol electron mol C−1 with a mean annual value of 8 ± 5 mol electron mol C−1. This optimum value suggests that in nutrient replete conditions like estuaries, alternative electron flows are low, while electrons transfer from photosystem II to carbon fixation is highly efficient. A statistical model was used to improve the estimation of primary production from electron transport rate as a function of significant environmental parameters. Based on this model, daily carbon production in the Seine estuary (France) was estimated by considering light and photic zone variability. A mean annual daily primary production of 0.12 ± 0.18 g C m−2 day−1 with a maximum of 1.18 g C m−2 day−1 in summer was estimated which lead to an annual mean of 64.75 g C m−2 year−1. This approach should be applied more frequently in dynamic ecosystems such as estuaries or coastal waters to accurately estimate primary production in those valuable ecosystems. [ABSTRACT FROM AUTHOR]

A Before/During/After Control-Impact approach is used to assess the effects of Port 2000 on the suprabenthos in the North Channel (NC) of the Seine estuary during the period from September 2001 to October 2015. Since the beginning of Port 2000 construction (2002–2005), the NC is affected by an increase of salinity (marine influence) and input of sand. The suprabenthos changes are mainly characterised by an increase in species richness in the upper part of the NC and a decrease in species density and biomass of the dominant mysid species over time. Multiple stressors (natural and anthropogenic) have been operating simultaneously (hydrological changes, construction of Port 2000, supplementary dredging) rendering the interpretation of the biological changes difficult. Thus, the present results evidenced a combination of changes in the Seine Estuary not only attributed to the impact of the Port 2000 construction. [ABSTRACT FROM AUTHOR]

During 2002–2005, a new container terminal in the commercial harbour of Le Havre, named “Port2000”, was built on the northern flank of the Seine estuary, northern France. This extension is already known to have modified the estuary current and sediment dynamics, as well as reducing biomass of the suprabenthos assemblage, for the whole downstream part of the system. However, studies on other biotic communities were largely inconclusive, and an ecosystem-wide analysis was still lacking. Here, we performed a before/after study of ecosystem dynamics of the different habitats of the Seine estuary, using a Linear Inverse Modelling technique (LIM-MCMC) to estimate all flows occurring in the food web. Ecological Network Analysis indices were calculated, summarising ecosystem functioning traits and giving indications about the habitat health status. Results showed that the southern flank (FS, Fosse Sud ) exhibits all characteristics to be considered as the least stressed habitat of the estuary: system activity and functional specialisation of flows were stable between periods, ecosystem recycling processes and detrital dynamics were also stable; an increase in trophic specialisation (decrease in system omnivory) was the only change confirming a general ecological succession. The northern flank (FN, Fosse Nord ), where the actual terminal was built, showed a food web with increased importance of lower trophic levels (increased detritivory and carbon recycling), increased stability and flow efficiency, but possibly regressed to a previous step in ecological succession. In the central navigation channel (CH), patterns of network indices were overall inconclusive and the general image is one of a constantly shifting food web, a condition possibly caused by the year-round dredging activities. The functioning of the Seine estuary – especially of FN and FS – seems to have been modified by the combination of harbour construction and the related mitigation measures. Network indices partially captured this combination of changes and, although not fully operational yet, they are promising tools to comply with the European Union mandate of defining ecosystem health status. [ABSTRACT FROM AUTHOR]

The objective of this study is to analyze the impact of hydrological variability influenced by climatic phenomena upon the sedimentary exchange between the turbidity maximum (TM) and a river mouth intertidal mudflat. This study, carried out over a period of 10 years (1997–2006) in the Seine Estuary (France), is specifically focused on two extreme periods: a wet one from 2001 to 2002 and a drier one from 2005 to 2006. This study is based on an original approach combining data gathered via low-altitude remote sensing with altimeter readings and ground-level measurements. During this 10 year period, we observed a link between climate change and the sedimentary processes on the mudflat surface. The modifications of sedimentary processes are mainly connected to the multiannual variability of hydrological flow rates that control the positioning of the turbidity maximum, the source of the sedimentary material deposited in this intertidal zone. The TM at the mouth of the Seine estuary is well developed; its maximum mass is estimated to be between 300,000 tons and 500,000 tons ( Avoine et al., 1981 ) with maximum concentrations in the surface waters ranging from 1 to 2 g ∙ l − 1 ( Le Hir et al., 2001 ). Most of the fine particles stored within the TM have been found to originate from within the catchment area ( Dupont et al., 1994 ). In the Seine estuary, the dynamics of the estuarine TM, in response to hydrodynamic forcings, have been previously described ( Avoine et al., 1981 ) and modeled (e.g. Brenon and Le Hir, 1999; Le Hir et al., 2001 ). The TM is upstream of the northern mudflat when the river flow is low (< 450 m ∙ s − 1 ) and nearby the study area when the river flow is higher. Thus during wet periods, the sedimentation rates increase by + 17 cm ∙ y − 1 , while during the drier one (when the turbidity maximum is located upstream of the estuary) we observed an erosion rate of 7.6 cm ∙ y − 1 . Sedimentation events in the mudflat resulting from spring tides are less frequent during dry periods, and they deposit a smaller quantity of sediment (− 23% of total deposition mass per event). Because of the lower flow rates coupled with the impacts of local development, the flood tides have become dominant. This contributes to the addition of sandy or silty sediments on the mudflat, of which the slope has increased 450% over 8 years caused by erosion. [ABSTRACT FROM AUTHOR]

Highlights: [•] We showed change of soil functioning and soil bacterial community after flooding. [•] The amplitude of responses was dependent on the soil type. [•] Results suggest that changes in flooding regime will alter the soil functioning. [•] Fluctuating regime increased N removal efficiency. [•] Fluctuating regime had the greatest impact on soil bacterial community. [ABSTRACT FROM AUTHOR]

In order to determine the role of resting eggs in the plankton dynamic of the main calanoid copepods species of the Seine estuary, 30 sediment cores of approx. 10 cm were sampled over one year in the subtidal area of the middle Seine estuary (France). The resting eggs of calanoid copepods were extracted from the 10 surficial cm of sediment, quantified (abundance), and then incubated, either immediately after extraction or after one month at low temperature, in order to determine the hatching success, the type of eggs (quiescent, diapause) and species. Viable resting eggs were found, with total abundances ranging from 0.06 ± 0.05 to 2.33 ± 1.40 × 107 eggs m−3 and higher values in early summer and mid autumn. This study indicated that the production of resting eggs may act in both short-term (continuous emergence, reinforcement of post winter production) and long-term survival (formation of an egg bank) for the key copepod species of the Seine estuary (Acartidae, Eurytemora affinis and Temora longicornis). With a hatching success of 3.5%, 11,644, 710,267 and 52,397 nauplii m−3 month−1 were estimated emerging from surficial sediments respectively for Acartia spp., T. longicornis and E. affinis; demonstrating the significant role of resting eggs in the population dynamic of the main calanoid copepods species in the Seine estuary. [ABSTRACT FROM AUTHOR]

Poses dam in the Seine River estuary acts as receptacle of water drain-offs from highly urbanized and industrialized catchment area; therefore, this water is highly contaminated by trace metals. Most trace elements are mainly bound to particulate matter and are incorporated rapidly into the sediments. Scavenging of these metals in the sediments can be reversible due to several perturbations so as sediments also act as a source of pollutants for the overlying water. For instance, natural events (tide, flood, storm) and anthropogenic processes (water management actions) can cause disturbance of sediments and subsequent remobilization of pollutants to the water column, thereby posing a potential threat for aquatic organisms. The purpose of this study was to evaluate the mobility of trace metals by different methods in the Seine estuary sediments. The surface sediment sampled at Poses dam was characterized by high pollution level of Cd, Cu, Zn, and Pb. The estimation of metal bioavailability through ratio ΣSEM/AVS (simultaneously extracted metals/acid volatile sulfides) indicates a potential bioavailability of trace metals. The chemical partitioning using the European Community of Bureau of Reference sequential extraction method revealed that over 85, 82, and 80 % of the total Cd, Zn, and Pb, respectively, were found to be associated with the exchangeable and reducible fractions of the sediment. Another approach used consists in the quantification of dissolved metals released by sediment resuspension experiments in laboratory under controlled conditions. The results indicated that metals are released rapidly from sediment with a sharp peak at the beginning of the experiment, followed by a fast coprecipitation and/or adsorption processes on the suspended particles. Also, the Cd, Pb, and Ni mobility is higher compared to that of the other metals. [ABSTRACT FROM AUTHOR]

The calanoid copepodEurytemora affinisPoppe, 1880 is the most abundant species of the mesozooplanktonic community of the Seine estuary (France) in the lower salinity zone. Diapausing eggs of this species have been found in the sediment of this estuary but they are few in comparison with those found for other calanoid species. We thus decided to test the effect of photoperiod on diapausing egg production inE. affinisfrom the Seine estuary. For this, an experimental device has been developed. A combination of five photoperiods and two temperatures was used and the production of eggs was studied for the first and the second clutch. The production of diapausing eggs was demonstrated under photoperiodic conditions less than or equal to 12 h of light either at 12 or 16°C with a maximum under constant darkness (6%). A significant increase in the number of non-viable eggs was also observed between the first and the second clutch for all tested conditions and this may be due to the non-fertilization of these eggs. We also verified that the late naupliar instars are sensitive to the photoperiodic signal. The experimental approach has revealed that the production of diapausing eggs in the key species to the downstream Seine estuary,E. affinis, could be induced by short days, but photoperiod was probably not the only factor responsible for the induction of diapausing egg production. The percentage of diapausing eggs obtained under the induction experiment is similar to that obtained from the eggs extracted from the sediment of the Seine estuary (7%). The strategy ofE. affinisin this estuary would be to constitute an egg bank, acting as long-term survival or in the case of adverse conditions. The role of geographical position (mainly latitude) and local conditions in the reproductive strategy ofE. affinisis discussed. [ABSTRACT FROM AUTHOR]

Abstract: The freshwater discharge into the Seine estuary decreased between 1996 and 2012 and no discharge>1200m3 s−1 has occurred after 2001. The suprabenthic community in the navigational channel of the Seine estuary was characterised in 1996 by high abundances and biomass of mysids and the decapod Palaemon longirostris, which were among the highest in the world for transitional waters during a period of high discharge of the Seine River. A recent sampling (2011–2012) of the suprabenthos in new hydrological conditions (i.e., low river discharge) showed subsequent changes of the quantitative composition of the community with both decreases of abundance and biomass. Such long-term changes were probably due to the combination of hydrological changes, and anthropogenic modifications of the entrance of the Estuary, the Port 2000 construction, and supplementary dredging in the navigational channel of the Rouen harbour. The changes of the suprabenthic community encompassed an important impact in the estuarine trophic chain, which was essential to fish juveniles, such as sea bass and flat fish. [Copyright &y& Elsevier]

The Seine Estuary is well known to be widely contaminated by organic pollutants and especially by polycyclic aromatic hydrocarbons (PAHs). Fish are known to metabolize PAHs, leading to different toxic effects at both cellular and sub-cellular levels. In this work, we studied the relationships between the 7-ethoxyresorufin- O-deethylase (EROD) activity in the liver, the level of DNA strand breaks in blood cells and the concentration of PAH metabolites in the bile of the sentinel flatfish species Limanda limanda. Muscle and liver samples were analysed for parent PAH levels. Female and male dabs of two size classes (juveniles and adults) were collected by trawling in two sites with different degrees of pollution during March and September 2005 and 2006. Significant effects of sex, age, site and season were demonstrated on EROD activity and the level of strand breaks. Parent PAH concentrations in dabs did not allow discriminating of the two sampling sites. However, for PAH metabolites, significant differences were observed with sites and seasons. Dabs collected at the mouth of the estuary appeared to be the most impacted when looking at the results obtained with the three selected markers. The significant correlations observed between the level of PAH metabolites and the level of DNA lesions showed the importance of a combined analysis of chemical and biochemical markers to correctly assess the contribution of chemical contamination to the toxic effects measured in situ in fish. [ABSTRACT FROM AUTHOR]

An epidemiological survey was conducted in the Seine estuary and in two smaller and relatively preserved estuaries on the French Atlantic coast in order to estimate the occurrence of liver lesions in European flounder, Platichthys flesus, and also to seek putative risk factors for the recorded pathologies. Four hundred and seventy-eight fish of both sexes and of different size ranges were sampled in the three studied areas, 338 of which in the Seine estuary. All fish were examined for histopathological liver lesions, while DNA adducts and otoliths were analyzed on a subsample. Five categories of hepatic lesions were recorded with the following prevalence for the Seine estuary: 36.7 % inflammations, 8 % parasites (mainly encysted nematodes), 6.5 % foci of cellular alteration (FCA), 5.3 % foci of necrosis or regeneration (FNR), and 1.5 % tumors. Inflammation occurrence increased according to age, contrary to parasitic infestations and FCA which were more prevalent in young fish, notably those of <1 year old (group 0). Tumors were only observed in females of more than two winters. Females exhibited a higher prevalence of tumors (3.0 %) and FCA (6.5 %) than males (0 and 2.6 %, respectively). Parasitic and infectious lesions and FNR were equally distributed in males and females. The prevalence of FNR was also shown to vary according to sampling season, with significantly more occurrences of liver necrosis in the fish collected in summer than in spring. Spatial differences were observed with a higher occurrence of encysted parasites in flounders from the upper Seine estuary, while inflammations predominated in flounders living downstream. Temporal trends were also noted, with an increased prevalence of parasitic infestations, inflammations, and FCA in the 2002-2003 period in comparison to the 1996-1997 one. The three flounder populations from the Seine estuary (Normandy), Ster estuary (Brittany), and Bay of Veys (Normandy) showed different spectra of hepatic lesions. Flounders from the Bay of Veys had relatively few liver lesions as compared to flounders from the two other estuaries. Flounders from the Ster estuary exhibited the highest prevalence of parasites (37.2 %) and inflammations (51.1 %). Finally, FCA and liver tumors occurred at very similar levels in both flounder populations from the Seine and the Ster estuaries. Group 0 flounders inhabiting the upper Seine estuary were more prone to parasitic and pre-neoplastic hepatic lesions and had higher levels of liver DNA adducts than the older ones living downstream. It was postulated that group 0 European flounders may serve as valuable bioindicators for assessing the quality of estuarine waters and the health status of euryhaline fish populations. [ABSTRACT FROM AUTHOR]

Abstract: Highly mutagenic compounds such as some PAHs have been identified in surface waters and sediments of the Seine river estuary. Suspended particulate matter (SPM) represents a dynamic medium that may contribute to the exposure of aquatic organisms to toxic compounds in the water column of the estuary. In order to investigate major sources of mutagenic contaminants along the estuary, water samples were taken at 25m downstream of the outlet of an industrial wastewater-treatment plant (WWTP). SPM samples were analyzed for their genotoxicity with two short-term tests, the Salmonella typhimurium mutagenicity assay (TA98+S9 mix) and the comet assay in the human HepG2 cell line. Sampling sites receiving effluents from a chemical dye industry and WWTP showed the highest mutagenic potencies, followed by petrochemical industries, petroleum refinery and pulp and paper mills. These data indicate that frame-shift mutagens are present in the Seine river estuary. Furthermore, the comet assay revealed the presence of compounds that were genotoxic for human hepatocytes (HepG2 cells). We also observed a high level of mutagenic potency in the sediment of the lower estuary (3×104 revertants/g). The source of mutagenic and genotoxic compounds seems to be associated with various types of effluents discharged in the Seine river estuary. Both test systems resulted in the same assessment of the genotoxicity of particulate matter, except for three of the 14 samples, underlying the complementarity of bioassays. [Copyright &y& Elsevier]

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Copyright of VertigO is the property of La Revue Electronique en Sciences de l'Environnement VertigO and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Benthic, viable resting eggs of calanoid copepods were found for the first time in the Seine estuary (France) during July 2008. Vertical distribution of the resting eggs in the sediment was determined up to 10 cm depth. Hatching success of the eggs extracted from different 1-cm thick sediment layers was experimentally tested immediately after extraction and after a long refractory phase (i.e. 11 months) of storage at low temperature (4–5 °C). The hatching success of resting eggs obtained immediately after sediment incubation was lower (0.72%) than the value observed after 11 months (4.50%) with an overall hatching success of 2.37%. The marine, calanoid copepod Temora longicornis was the primary species to hatch from the eggs; however, the estuarine calanoid copepod Eurytemora affinis also hatched from resting eggs. The mean abundance of eggs found in sediment (1.42 × 106 eggs m−2) was comparable to that reported for other marine and estuarine calanoid copepods. The Seine estuary sediment had a high variability of egg abundance (between 0.14 and 8.10 × 107 eggs m−3) suggesting that the hydrodynamics of this macrotidal estuary are likely responsible for this variability. Significant sediment resuspension occurs in the Seine estuary during flood periods and spring tides leading to resting eggs to contribute along the year to the nauplii recruitment of calanoid copepods. On average, around 400,000 nauplii m−3 month−1 of the main calanoid copepods can emerge from the surface layer sediment in the Seine estuary, suggesting that resting eggs could play an important role in the population dynamics of key calanoid copepods in the Seine estuary. [Copyright &y& Elsevier]

Abstract: Annual variability in abundance and population structure of the copepod Eurytemora affinis was studied in the maximum turbidity zone of the Seine Estuary in 2005. An Eulerian sampling strategy was applied monthly from March to July and from September to December. Chlorophyll a and suspended particulate matter (SPM) concentration, copepod abundance and stage distribution, and phytoplankton abundance were measured in sub-surface and near-bottom water during the ebb phase. Total E. affinis abundance was at a maximum in March and April (>200 × 103 ind. m−3), and decreased from May to September (<25 × 103 ind. m−3). This decrease corresponds to annual increases in temperature, salinity, chlorophyll a concentration and phytoplankton abundance, which was dominated by large diatoms, and decreases in SPM and river discharge. The phenology observed in 2005 was almost two months earlier compared to previous studies in the 1990s, when E. affinis reached maximum abundance in May and June. The low proportion of nauplii (<50%) in the population and high abundance of ovigerous females suggests that low recruitment is probably related to anomalously low temperatures in late winter (<5 °C). Whatever the horizontal position of the population in the estuary, adult and late copepodid stages are distributed in higher salinity than naupliar stages. Overall E. affinis population abundance was driven by parameters that characterize water masses at the tidal scale and by river discharge and chlorophyll a at the annual scale. By integrating the tidal effect, the high-frequency sampling protocol used appears to be optimal for investigating annual variability of planktonic communities in megatidal estuaries. [Copyright &y& Elsevier]

Abstract: Estuaries and coastal waters are essential nursery habitats for many marine species, and especially for flatfishes. Thus, investigating how anthropogenic disturbances affect the quality of these habitats is of major importance to understand their consequences on the population renewal of marine species. The aim of the present study was to analyse the effects of estuarine habitat degradation on the population of the common sole in the Eastern Channel, a key species in the fish community and fisheries in this area. We especially focused on the drastic drop in the surface area and on the low water quality of the Seine estuary, the main river of the Eastern Channel. A geographic Information System (GIS) was used to develop quantitative maps of sole nursery habitats in the Eastern Channel by using a habitat suitability model based on bathymetry and sediment structure. This approach indicated that juvenile densities are low in the Seine estuary with regards to other nursery sectors. Then, thanks to historical maps of the Seine estuary, habitat suitability maps were built for key dates in the modifications of this estuary since 1850. This backward predictive approach suggests that habitat loss in the Seine estuary has led to a 42% decrease of its nursery capacity. As the density of juvenile sole in the Seine estuary is low in comparison to other sectors, this represents only a 3% loss at the sole population scale, in the Eastern Channel. However, when we assumed that prior to anthropogenic disturbance the juvenile density in the Seine estuary might have been equivalent to the current density of adjacent sectors with higher quality, the loss in abundance could be nearly 23% (8–36%). Results suggest that the loss in habitat surface combined with habitat degradation has led to an important loss in the contribution of the Seine estuary nursery to the whole sole population in the Eastern Channel. [Copyright &y& Elsevier]

The implementation of the European Water Framework Directive has provoked enthusiastic debate between scientists and stakeholders, as they try to define the ecological quality status (EcoQS) of all water bodies, including estuaries (i.e., transitional waters). The issue is complex because estuarine environments are variable, due to fresh and marine water input and anthropogenic impacts. Benthic species and communities have adapted to tolerate temporal physico-chemical changes (e.g., salinity, substrata, depth, fine particles and a Maximum Turbidity Zone that is rich in organic matter). However, anthropogenization affects not only the water quality, but also estuarine surface size and navigation channel management. Though numerous bio-indicators and indices are used to define estuarine system EcoQS, very few of them were developed specifically for such variable anthropogenized systems comprising a variety of conditions. The critical question is: ‘Is it possible to define an EcoQS for such specific modified and naturally stressed ecosystems?’ Indicators must be chosen pragmatically so that they will be environmentally sustainable, economically viable, technologically feasible, socially desirable/tolerable, legally permissible and politically expedient. This contribution proposes an adaptation of the BOPA index, the Benthic Opportunistic Annelida Amphipod index (BO2A), for use in the freshwater zones of transitional waters (i.e., up to the upper limit of tidal range). Several possibilities are discussed in light of the diverse disturbances and the heterogeneity of such stressed zones. [Copyright &y& Elsevier]

Abstract: This article presents numerical simulations for the turbidity maximum (TM) in the Seine estuary using a 2-D vertical width-integrated two-phase flow model. The results are in rather good agreement with observations in a natural environment. The displacement of the TM is reproduced and a concentrated particles layer is observed on the numerical results. These results highlight the interest of this innovative approach for sediment transport simulations in estuary: no erosion or deposition laws are imposed. [Copyright &y& Elsevier]

The three main estuaries in the French Atlantic coast – the Seine, Loire and Gironde, all with high tidal regimes – are interfaces between the continental and the coastal ecosystems. The Seine and Gironde are highly contaminated, whereas the Loire remains in a more natural state. Both the Seine and Gironde have suffered from harbour construction, and as a result, their biological units are extremely compartmentalized. Benthic species and communities have adapted to tolerate temporal physical and chemical changes ( e.g. salinity, substrata, depth, and levels of fine particles and oxygen) and human activities ( e.g. dredging, shipping traffic, and habitat reduction). Although numerous bio-indicators and indices are used to define the ecological quality status (EcoQS) of coastal waters, very few of them were developed specifically for environments with a mosaic of conditions and salinity levels, including freshwater. The main problem appears to be that all the indices for determining anthropogenic stress examine the abundances of stress-tolerant species, which may also be able to tolerate natural stressors such as those occurring in estuaries. This paper takes a look at the development status of the benthic indicators and index approaches used in the three main estuaries along the French Atlantic coast. In addition, it examines the adaptation of the different benthic indicators to the taxonomic sufficiency principle, and the adaptation of the Benthic Opportunistic Polychaetes Amphipods index (BOPA) and the Benthic Opportunistic Annelida Amphipod index (BO2A) for use in the freshwater zones of transitional waters ( i.e. up to the upper limit of the tidal range). Several perspectives are discussed in light of the diverse disturbances and the heterogeneity of such stressed zones, such as the use of multimetric and scoring approaches. [ABSTRACT FROM AUTHOR]

Abstract: The brackish water copepod Eurytemora affinis is the most abundant copepod species in the low salinity zone (2-15) of the Seine estuary. Despite its ecological importance, little is known about its population dynamics in the Seine. We studied the effects of temperature (10 °C and 15 °C) and salinity (5, 15 and 25) on reproduction under non-limiting food conditions. We used experiments to determine multiple reproductive parameters for E. affinis. In all experiments, we fed E. affinis a mixture of Rhodomonas marina and Isochrysis galbana. Couples of pre-adult females (C5) and adult males were mated until the female extruded a clutch of eggs and then individual females were observed every 6-12 hours until death to determine (a) embryonic development time, (b) inter clutch time and (c) clutch size throughout their adult lifespan. All reproductive parameters were negatively affected by low temperature (10 °C) and by high salinity (25). At 10 °C and a salinity of 25, mortality during the post-embryonic period was extremely high (85%). Differences in all reproductive parameters between salinities 5 and 15 were minimal. From 15 °C to 10 °C mean latency time (time between hatching of eggs and extrusion of new ones) increased from 0.8 to 2.25 days, the mean embryonic development time from 2.2 to 3.2 days and the mean clutch size decreased from 38 to 22 eggs female-1. The mean clutch size decreased when females reached a critical age. The hatching success was high (near 95%) under all conditions except at high salinity. Egg production rates showed no significant differences between salinities 5 and 15 and were significantly higher at 15 °C (13 eggs female-1 day-1 at salinity 5 and 15) than at 10 °C (4 eggs female-1 day-1). These values at 15 °C were higher compared to those from other populations of E. affinis in estuaries or lakes. The high reproductive potential of E. affinis from the Seine estuary at 15 °C and low salinities explain its high densities in the low salinity zone during spring and early summer. [Copyright &y& Elsevier]

Concentrations of volatile hydrogen sulfide (H2S), carbonyl sulfide (OCS), methane thiol (MeSH), dimethyl sulfide (DMS), and dimethyl disulfide (DMDS) in the Seine estuary (France) were investigated in spring 2005 using samples collected from the first meter beneath the surface. Levels of dissolved metals (Ag, Cd, Cu, Zn, Ni, Co, Pb), suspended particulate matter, and particular organic carbon were also assessed. Maximum concentrations were 0.80 nM for H2S, 0.64 nM for OCS, 3.06 nM for MeSH, 11.06 nM for DMS, and 1.18 nM for DMDS, and different features were observed for the five volatile reduced sulfur compounds (VRSCs). Experiments were conducted to determine silver- VRSC conditional stability constants. Major interactions were observed between H2S and Ag, which may partially account for the absence of volatile H2S at the lowest salinities. OCS, MeSH, and DMS did not interact with Ag, as revealed by their insignificant K′ values. Variations in concentrations along the salinity gradient may be explained by the influence of phytoplanktonic compounds. [ABSTRACT FROM AUTHOR]

Abstract: This study presents an original work on measurements of stable and radioactive iodinated species in the Seine estuary (France), with estimates fluxes of volatile gaseous species from water to the atmosphere. Various iodinated compounds were identified in water and air in particular 131I in water, what is unusual. Concentrations and behaviour of iodinated elements in the Seine estuary seem similar to what has been observed in other European estuaries. MeI (Methyl Iodide) and Total Volatile Iodine (TVI) fluxes from water to air vary between 392 and 13949pmolm−2 d−1 and between 1279 and 16484pmolm−2 d−1, respectively. Water to air flux of TVI for the Seine river was estimated in the range 4–46kgy−1. Measurements of 131I in water varying between 0.4 and 11.9Bqm−3. Fluxes of 131I from water to atmosphere are in the range 2.4×105–1.3×107 Bqy−1, close to an annual discharge of 131I by a nuclear reactor. [Copyright &y& Elsevier]

The Seine estuary (France) is one of the world’s macrotidal systems that is most contaminated with heavy metals. To study the mercury-resistant bacterial community in such an environment, we have developed a molecular tool, based on competitive PCR, enabling the quantification of Gram-negative merA gene abundance. The occurrence of the Gram-negative merA gene in relation with the topology (erosion/deposit periods) and the mercury contamination of three contrasted mudflats was investigated through a multidisciplinary approach and compared with a non-anthropized site (Authie, France). The higher abundance of the Gram-negative merA gene in the Seine estuary mudflats indicates a relationship between the degree of anthropization and the abundance of the merA gene in the mudflat sediments. In the Seine mudflats, the maxima of abundance are always located in fresh sediment deposits. Therefore, the abundance is closely related with the hydrosedimentary processes, which thus seem to be determining factors in the occurrence of the Gram-negative merA gene in the surface sediments of the Seine’s mudflat. [Copyright &y& Elsevier]

The Marais Vernier is the largest freshwater wetland in the Seine Estuary in northern France. It is in a heavily urbanized and industrialized region and could be affected by atmospheric deposition and by fluvial input of contaminants in water diverted from the Seine River. To evaluate contaminant histories in the wetland and the region, sediment cores were collected from two open-water ponds in the Marais Vernier: the Grand-Mare, which was connected to the Seine by a canal from 1950 to 1996, and the Petite Mare, which has a small rural watershed. Diversions from the Seine to the Grand-Mare increased sedimentation rates but mostly resulted in low contaminant concentrations and loading rates, indicating that the sediment from the Seine was predominantly brought upstream by tidal currents from the estuary and was not from the watershed. Atmospheric sources of metals dominate inputs to the Petite Mare; however, runoff of metals from vehicle-related sources in the watershed might contribute to the upward trends in concentrations of Cr, Cu, and Zn. Estimates of atmospheric deposition using the Petite Mare core are consistent with measured deposition in the region and are mixed (similar for Hg and Pb; larger for Cd, Cu, and Zn) compared with deposition estimated from sediment cores in the northeastern United States. A local source of PAHs in the watershed of the Petite Mare is indicated by higher concentrations, higher accumulation rates, and a different, more petrogenic, PAH assemblage than in the Grand-Mare. The study illustrates how diverse sources and transport pathways can affect wetlands in industrial regions and can be evaluated using sediment cores from the wetland ponds. [ABSTRACT FROM AUTHOR]

Abstract: Organic matter was studied in the turbidity maximum zone (TMZ) of the Seine Estuary during 8 tidal cycles from April to October in 2001, 2002 and 2003, covering a salinity range from 0 to 27. The hydrological conditions were quite varied (extremely wet in 2001, unusually dry in 2003). A particularly striking feature is the high organic matter content in the suspended solids (SS) of the Seine estuary (4–5%). By determining micro-organism activity and organic carbon partitioning, either linked to particles or in dissolved forms, and estimating the TMZ water volumes, together with SS, we extrapolated these activities and stocks to the whole TMZ. Carbon metabolism in the TMZ and fluxes upstream of the TMZ were compared on the dates of field surveys, and the routes and fate of carbon in the TMZ were quantified in order to learn about the trophic status of this estuarine zone in terms of autotrophy vs. heterotrophy. The upstream total organic carbon (TOC) fluxes (48% of particulate organic carbon (POC), 52% of dissolved organic carbon (DOC) on average) varied fourfold between the surveys, reaching the highest value of 280TCd−1 during the wet summer of 2001; and the lowest value of about 70TCd−1 in August 2003. Whereas nearly all of the DOC flux entering the TMZ reaches the coastal marine zone, mostly (at least 85%) in a refractory form, the POC accumulates in the TMZ of the estuarine channel, particle exportation being negligible. In the TMZ, biodegradation of DOC was, on average, much less (only a 2% decrease in the BDOC/DOC ratio between the TMZ upstream and downstream fluxes) than biodegradation of POC (11%). A simplified model of the TMZ (LIFT- Lumped Idealisation of the ecological Functioning in estuarine Turbidity maximum) was constructed for investigating the dynamics of organic matter on a seasonal scale. The agreement between observation and calculation allowed us to run sensitivity tests using new constraints; reductions of the upstream fluxes of phytoplankton and organic carbon showed that the high content of organic matter, originating mostly from the domestic effluents of the Paris conurbation, can explain the high organic content of the Seine estuary TMZ. [Copyright &y& Elsevier]

Abstract: A survey within the French National Programme of Ecotoxicology was carried out in 2002, 2003 and 2004 to study the response of Nereis diversicolor populations (Polychaeta, Nereididae) to the impact of pollution in the Authie estuary (non-contaminated site) and in the Seine estuary (contaminated site). In the period studied, the density varied from 672ind.m−2 to 3584ind.m−2 in the Authie estuary and from 80ind.m−2 to 920ind.m−2 in the Seine estuary. Biomass varied from 3.94gm−2 (dry weight) in February 2004 to 38.0gm−2 in August 2003 in the Authie estuary and from 3.4gm−2 in February 2002 to 0.6gm−2 in February 2004 in the Seine estuary. Density and biomass of the populations of N. diversicolor were consistently lower in the Seine estuary than in the Authie estuary. Size frequency histograms permit the analysis of the cohorts as well as the elaboration of the growth curves. For the individuals from the Authie estuary, the relation between dry weight (DW) and length L3 (prostomium, peristomium and chaetiger 1) was DW=4.2205 L32.9832. For those from the Seine estuary, the relation between dry weight and L3 was DW=0.4697e1.7209L3. The individuals of N. diversicolor should belong to eight cohorts in Authie estuary (two cohorts each year) instead of six cohorts for those from the Seine estuary. These differences can be attributed to the effect of pollution on the population of N. diversicolor. [Copyright &y& Elsevier]

Abstract: Using recent indices developed, in part, for use under the European Water Framework Directive (AMBI, BENTIX, BOPA, BQI, I2EC and the trophic index ITI), the ecological quality status of two highly contaminated environments—the Bay of Seine and the Seine estuary (Eastern English Channel)—was determined on several spatial and temporal scales. Data from 604 observations gathered over a 14-year period (1988–2002) were analyzed, and the results used to show the relationship between biotic indices, environmental variables and classic descriptors (e.g., number of species, total abundance, dominance index, ES(50) and Shannon/Brillouin diversities). Though the specific ecological quality (EcoQ) values calculated with the various indices were different, the overall trend of the results was similar. Synthesizing the values produced by the six indices used in the study allowed attribution of a high to good EcoQ status to the Bay of Seine and a moderate EcoQ to the estuary. The mesh size used when processing samples was proved to have no effect in winter on the EcoQ values for either body of water. [Copyright &y& Elsevier]

Abstract: The European Water Framework Directive will have instituted the concept of Ecological Quality Status (EQS) as a way to assess the biological quality of water masses. The EQS will be based mainly upon the composition of the different biological compartments in the ecosystem specially the benthos as compared to certain reference sites. Such management tools are already well established for freshwater (i.e. biotic indices), but not for coastal and estuarine (i.e. transitional) waters. In the framework of the Seine-Aval programme a workshop on benthic indicators was organized at Wimereux (France) in June 2005. The aim of this workshop and this paper is (1) to present the experiences of the Seine Aval researchers, and the French scientific approaches to benthic indicators, with those international experiences and approaches that have been published or are under development; and (2) to examine the existing benthic tools and their possible use in the characterization of the state of estuarine ecosystems. The debate during the workshop and the numerous recently published on the WFD are discussed in term of the implementation of the WFD in transitional water bodies using benthic indicators and indices. Some proposals for the future underline the needs to re-examine and adapt the different index thresholds, to take into account physical disturbances, to inventory the existing conditions vs reference conditions and to be as pragmatic as possible in using the WFD in transitional waters. [Copyright &y& Elsevier]

Hydrophobic organic contaminants (HOC) (i.e. PAHs and PCBs) were measured in the water column and in Eurytemora affinis samples from the Seine Estuary collected from November 2002 to February 2005. Results showed seasonal variations of both total PCB and PAH levels in the suspended particulate matter (SPM) and in the copepods with maximum levels during winter times. PAH and PCB concentrations in the SPM ranged from 499 to 5819ngg−1 and from 58 to 463ngg−1, respectively. Phenanthrene, pyrene and benzo[b+j+k]fluoranthene (B[b+j+k]F) were the predominant PAH compounds in the water column, while CB 101, 118, 153 and 138 were the most abundant PCB congeners. PCBs and PAHs bioaccumulated by E. affinis (EA) varied between 383 and 1785ngg−1 and 165–3866ngg−1. CB101, 153, 138 and B[b+j+k] were, respectively, the major compounds of PCB and PAH fingerprints in EA. Thereby, the copepods could reach high accumulation factor (ACF) (91000 for PCBs and 17000 for PAHs). The principal component analyses of contaminant concentrations and environmental parameter datasets distinguished two groups of copepods. The winter time cluster, with high percentage of adult copepods, which bioaccumulated the highest PCB and PAH body-burdens, and the second cluster with juveniles showing the lowest HOC concentrations. Thus, PAH and PCB concentrations in EA exhibited significant correlations with the percentage of adults making up the samples. [Copyright &y& Elsevier]

The Seine estuary, one of the largest estuaries of the European northwest continental shelf, is subjected to numerous anthropogenic influences. Here we present an assessment of the microbial faecal contamination of the estuary water. The most vulnerable areas were defined on the basis of the fluxes of indicator organisms and the occurrence of Salmonella and Cryptosporidium sp. and Giardia sp. (oo)cysts. The microbial quality of the water changes from upstream to downstream: in the upstream area, contamination by faecal-indicator bacteria and Salmonella occurs during periods of high flow; in the urbanized area, mid-way between the uppermost areas of the estuary and its mouth, discharge from a wastewater treatment plant and a tributary degrade water quality; at the estuary mouth, the accumulation of microorganisms attached to particles in the maximum turbidity zone, particularly Clostridium perfringens spores and oocysts of Cryptosporidium, is accompanied by inputs of ThC and Escherichia coli from tributaries. In some areas, significant strong relations are observed between Salmonella, (oo)cysts of protozoan, and levels of faecal indicators. [Copyright &y& Elsevier]

The Seine estuary (France) is currently one of the world’s most contaminated estuaries, due in particular to its high cadmium and lead content. Proper understanding of contaminant transfer, transformation and retention mechanisms throughout the estuary and up to the adjacent marine zone require a range of studies involving data collections, experiments, and modeling tool. A multivariable transport model (SiAM-3D) was used to simulate dissolved and particulate transport and it is applied to several calculation grids; a speciation model (MOCO) was used to select key species and obtain a schematic system representation. The coupled model for Cd and Pb was compared with field measurements. The complementary character of various tools (model applied to annual time scale, in situ measurements and experiments) allowed to explore and quantify various hypotheses on the high dissolved cadmium concentrations observed during low river flow. The target is to achieve a compromise between acceptable computing times and adequate result accuracy. Although particle and contaminant behaviour is globally well-reproduced by the coarse grid, calculation errors relating to bayward fluxes and stocks deposited inside the estuary were highlighted after comparison with the fine grid. [ABSTRACT FROM AUTHOR]

Measurements of polycyclic aromatic hydrocarbons (PAHs) were carried out from 2001 to 2003 in various environmental compartments (ambient air, atmospheric deposition, soils, sediments, runoff, and surface waters) in the Seine Estuary. The goal of this study was to identify the importance of atmospheric fluxes to occurrence of PAHs in the estuary, and to estimate the major pathways of their transport and accumulation within this ecosystem. The annual atmospheric inputs in the estuary ranged from 2.5 to 16 kg for the first sampling year, which is high when compared to those calculated for other European locations. In parallel, PAH transport from the atmosphere to the watershed outlet was investigated for two rural and urban small experimental watersheds within the Seine Estuary. In rural areas, atmospheric inputs are higher than exported loads by surface water and PAHs are accumulating in soils. The inverse occurs in urban areas, where the contribution of atmospheric deposition is negligible compared with PAH exported loads by runoff. These results allowed us to establish a mass balance for PAHs on the scale of the Seine Estuary, and to determine the dynamics of PAH transport. This study highlights the role of the atmospheric compartment in the transfer of contaminants and the importance of the local PAH inputs within the Seine Estuary. [ABSTRACT FROM AUTHOR]

During the 2001–2002 hydrological cycle, 8,000 tons P year−1 (44% as particulate phosphorus) originating from the Seine basin entered the Seine estuary. P content in suspended sediments (SS) is 2.9 g P kg−1 (80% as inorganic form) at Poses (the upstream limit of the Seine estuary). During the transfer from Poses to Caudebec (the limit of saline water intrusion), Particulate Inorganic Phosphorus (PIP) in SS decreases by 40% whereas Particulate Organic Phosphorus (POP) remains stable. This decrease is explained as the result of (i) a dilution by SS poorer in P, originating from storage zones (mudflats) within the estuary, and (ii) a loss of P by sedimentation, especially in the Rouen harbour where 15% to 20% of SS are yearly trapped and extracted. Downstream, in the turbidity maximum of the estuary, P content in SS is twice as low as at Poses (1.5 g P kg−1, 70% as inorganic form). PIP content is fairly homogeneous both vertically and throughout an annual survey. On the other hand, POP varies by season. Higher POP content is observed during vernal period with phytoplankton accumulation. In a salinity gradient from 0 to 30 (PSS78), PIP content further decreases by 30%. POP does not vary much in this gradient, leading to the assumption that PIP is submitted to desorption in response to the dilution by marine waters (poor in orthophosphates). Using 32P isotopic method, we establish a mathematical formulation of P exchangeable between the suspended solid and water phases of the Seine estuary. Particulate P in the turbidity maximum zone is shown to represent a possible source of dissolved P, available for algal growth in the Seine Bight. Instead of playing a role of nutrient retention, the turbidity maximum zone of the Seine estuary could favour coastal eutrophication. [ABSTRACT FROM AUTHOR]

Industry represents about 31% of the upper Normandy region total value-added against 19.5% at national level. The same holds for the employment, since industry accounts for 21% of total local jobs, against 18% at national level. This article attempts to answer the following question: can we explain this specific concentration of economic activity by the natural advantages (water availability, easy access by water) provided by the Seine Estuary? We first characterize “strongly Seine Estuary-dependent” industrial sectors, using simple indicators such as water withdrawals and pollution emissions. Then, we evaluate the influence of these sectors on the forces (labor market pooling, input sharing and knowledge spillovers) that lead to concentration of the economic activity in the Seine estuary. We find strong evidence that this economic activity is still natural resource based. [ABSTRACT FROM AUTHOR]

Within the framework of the European Water Framework Directive, the Seine-Normandie Water Agency has defined prospective scenarios describing possible trends of evolution of the pressures on water resources. In order to evaluate the resulting water quality improvement or degradation of water bodies in the Seine river basin, an integrated modelling was proposed. The approach consisted in coupling three models, the seneque model for upstream sub-basins, the P roS e model for the Seine river and main tributaries and finally the s i am1d model for the downstream estuary. After consistency verification, the integrated model was applied to scenarios proposed by the Seine-Normandie Water Agency. As a result of improvement in the nitrogen treatment by waste water treatment plants, the annual load of ammonia at the basin scale will be reduced by 65%. The oxygen and ammonia criteria in the estuary will improve from “bad” to “good”. However the nitrate criteria will remain “poor”, given the strong influence of non-point sources. Despite a 70–75% drop of the point orthophosphate loads, the criteria for this variable will also remain “poor”. The nutrient levels will be high enough to maintain eutrophication in the system; a general trend to a shift from N-limitation to P-limitation will be accentuated. [ABSTRACT FROM AUTHOR]

The Bay of Seine is a potentially important nursery ground, especially for flatfish. This area, however, is also strongly anthropogenically influenced. A composite approach was chosen to compare the flatfish nursery function of the Seine estuary with other coastal and estuarine areas and to determine the impact of anthropogenic disturbances. It emerges that alteration of the nursery function in the Seine estuary is related to the loss of nursery habitat and to a lower quality of the residual surfaces. These observations stressed the importance of habitat destruction and decreased quality of remaining habitat for fish stocks renewal. [ABSTRACT FROM AUTHOR]

Abstract: In tide-dominated systems, fine-grained deposits occur in intertidal areas of inner estuaries as loci of convergence of fluvial and marine material. Even in the vicinity of estuaries, mud deposits are rare on open sandy beaches. This study focuses on temporary occurrences of muddy sediments on marine beaches along the Calvados coastline in Normandy, adjacent to the macrotidal Seine estuary (France). Clay mineralogy, major–minor–trace elements and radionuclides were used as particulate markers to determine the provenance of the mud deposits. The fine fraction, defined here as particles <50μm, was analysed, in surficial muddy sediments on seven beaches between the Seine estuary and the Orne river mouth, sampled between February 2002 and June 2003. The deposits were compared to earlier Holocene relict deposits, which crop out on some beaches and on the shoreface, and to Mesozoic marls and limestones, which have detached from the coastal cliffs. The use of the three types of particulate markers revealed no significant seasonal or geographical variations between the beaches. The muddy deposits were made up of the same sedimentary pool of particles. The clay mineralogical and geochemical characteristics of these mud deposits enabled modern (i.e. present-day and earlier Holocene fine silts and clays) to be distinguished from ancient (i.e. Mesozoic) sediments. The use of radionuclides (60Co and 137Cs) confirmed the marine influence in the modern deposits, with a decreasing gradient along the Calvados beaches towards the east. The presence of several specific major–minor–trace elements (e.g. Ti, P) revealed that some of the fine material originated in the Seine estuary. Despite the occurrence of easily erodable rocks (i.e. clays, marls and limestones) in the coastal cliffs, this source represented a limited supply, which is only of local significance. Small rivers, such as the Orne, Dives and Touques which discharge in the study area act as secondary suppliers of fine-grained material to this system. In spite of the exposed coastal setting where strong tidal currents and waves occur, the beaches have become a distal part of the Seine estuarine system and form a temporary sink for strongly mixed fine material mainly of riverine (Seine River) and open marine (Bay of the Seine and the Central English Channel) origins. This is consistent with the infilling of the estuary, the reduction in accommodation space in its inner part, and the offshore shifting of the depocentre of the mud. [Copyright &y& Elsevier]

Abstract: Semi-diurnal and fortnightly surveys were carried out to quantify the effects of wind- and navigation-induced high-energy events on bed sediments above intertidal mudflats. The mudflats are located in the upper fluvial part (Oissel mudflat) and at the mouth (Vasière Nord mudflat) of the macrotidal Seine estuary. Instantaneous flow velocities and mudflat bed elevation were measured at a high frequency and high resolution with an acoustic doppler velocimeter (ADV) and an ALTUS altimeter, respectively. Suspended particulate matter concentrations were estimated by calibrating the ADV acoustic backscattered intensity with bed sediments collected at the study sites. Turbulent bed shear stress values were estimated by the turbulent kinetic energy method, using velocity variances filtered from the wave contribution. Wave shear stress and maximum wave–current shear stress values were calculated with the wave–current interaction (WCI) model, which is based on the bed roughness length, wave orbital velocities and the wave period (T S). In the fluvial part of the estuary, boat passages occurred unevenly during the surveys and were characterized by long waves (T S>50s) induced by the drawdown effect and by short boat-waves (T S<10s). Boat waves generated large bottom shear stress values of 0.5Nm−2 for 2–5min periods and, in burst of several seconds, larger bottom shear stress values up to 1Nm−2. At the mouth of the estuary, west south-west wind events generated short waves (T S<10s) of H S values ranging from 0.1 to 0.3m. In shallow-water environment (water depth <1.5m), these waves produced bottom shear stress values between 1 and 2Nm−2. Wave–current shear stress values are one order of magnitude larger than the current-induced shear stress and indicate that navigation and wind are the dominant hydrodynamic forcing parameters above the two mudflats. Bed elevation and SPM concentration time series showed that these high energy events induced erosion processes of up to several centimetres. Critical erosion shear stress (τ ce) values were determined from the SPM concentration and bed elevation measurements. Rough τ ce values were found above 0.2Nm−2 for the Oissel mudflat and about 1Nm−2 for the Vasière Nord mudflat. These results demonstrate the advantages of combining the measurement of instantaneous velocity and bed elevation to determine in situ the erosion and deposition processes as a function of bottom shear stress variations. [Copyright &y& Elsevier]

Abstract: The Marais Vernier, located in the upper reaches of the Seine River Estuary (northern France), preserves a thick Holocene succession of laminated detrital deposits and peats. The spectral analysis of one laminated deposit suggests that tidal processes were largely responsible for supplying sediments to this system. Two periods (16 and 32 laminae per cycle) were identified. These cycles can be related to either both the synodic neap–spring cycle (the so-called “fortnightly cycle”) and the anomalistic monthly cycle or both the semiannual and annual tidal cycles. The recognition of tidal influence on these deposits provides insight into the likelihood of some relative sea-level fluctuations previously inferred from these sediments. The depositional rates calculated for the laminated deposits, based on the recognition of these tidal cycles, suggest that the time interval required to deposit the sediments was far shorter than is implied by considering rates based on regional sea-level rise alone. [Copyright &y& Elsevier]

Abstract: The aim of this study is to analyse and to quantify the fine particles transfer (i.e.<63 μm) in the marine part of the man-altered macrotidal Seine estuary (France) by (i) an analysis of a two year time-series of altimeter data, which reveals the bed elevation variations on an intertidal mudflatd located at the Seine mouth and (ii) measurements of the concentration of suspended particulate matter (SPM) contained within the turbidity maximum (TM). The results of this analysis reveal that sedimentation on the mudflat is mainly controlled by the dynamics of the TM such that during the largest spring tides (i.e. tidal ranges >7.1 m). Then, deposition of SPM from the turbidity maximum becomes important, allowing fine particles to settle on the mudflat, where the current velocities are low (<0.4 m s−1). On tides of lower range (<7.1 m) bed elevation levels suggest that erosion of the mudflat surface dominates, however dewatering processes also occur in the soft mud deposits resulting in compaction. During periods of wave activity and periods of increasing river discharge, the mudflat surface experiences rapid erosion. These periods of erosion (sudden or progressive) imply a transfer of fine-grained material from the mudflat surface back into the TM. The long term (∼22 months), high frequency (1 measurement every 10 min) and high resolution (0.6 mm) dataset obtained from the altimeter allows quantification of the volume of material exchanged between the intertidal area and the estuarine standing stock of SPM. The maximum of deposition on the studied mudflat during the study was of 27 cm, with highest deposition occurring after the periods of highest river flow and implying that between 25 and 40% of the maximum estimated mass of SPM held within the estuarine TM (300,000–500,000 T) had been temporarily deposited on the mudflat. Likewise following periods of resuspension by wave activity, bed elevations reduced by an order of ∼1 cm, suggesting a release of between 1–1.5% of the TM load from the mudflat back into suspension. The study shows that lateral exchanges of sediment between the intertidal reaches of the estuary and the water column are an important part of the sediment budget, and that the supply of sediment available for deposition (i.e. the TM) has a causal relationship with sedimentation rates experienced by intertidal mudflats. [Copyright &y& Elsevier]

Abstract: Using a Before/During/After sampling protocol, the effects of the Le Havre harbour extension, which was started at the end of 2001, on the macrobenthic and suprabenthic communities in the eastern Bay of Seine (English Channel) were examined. As the construction phase has not yet been completed, the results presented here reflect only the data collected before and during the operations (September 2000 and 2002 for benthos sampling and March 2001, September 2001, October 2002 and March 2003 for suprabenthos sampling). Although bio-sedimentary changes did occur at the mouth of the Seine river, an analysis of benthic assemblages reveals that the dredging and construction operations do not seem to have influenced assemblage structure or the spatial distribution of organisms. Comparisons of the suprabenthic assemblages at each sampling date indicate that seasonal dynamics was mainly responsible for determining species distribution. We conclude that, 1 year into the harbour management plan, the observed changes in benthic and suprabenthic assemblage abundance do not exceed the range of spatial variability that exists naturally in the Seine estuary. Despite this compensatory actions designed to protect the aquatic habitats and to preserve a sustainable and healthy ecosystem have been added to the infrastructure development plan. [Copyright &y& Elsevier]

Abstract: A two year survey of benthic primary production during periods of emersion was performed on two stations of an intertidal mudflat (a muddy-sand station and a muddy station) in the Seine Estuary (English Channel, France). The goals of this study were to investigate the seasonal variations of metabolism, to estimate daily potential primary production variation at the annual scale and to estimate the annual potential primary production of the mudflat. Primary production and respiration were estimated by in situ measurements of carbon dioxide fluxes. Chlorophyll a concentration exhibited a great variability on both locations. Gross community production ranged from ca. 0 to 77mgCm−2 h−1 at the muddy-sand location and from ca. 0 to 122mgCm−2 h−1 at the muddy location. Community respiration showed a seasonal trend following temperature variations (up to 28.51mgCm−2 h−1 in the muddy-sand and up to 23.40mgCm−2 h−1 in the mud). Daily potential primary production was calculated, according to seasonal variations of photosynthetic parameters calculated using three photosynthesis versus irradiance curves obtained for the muddy location. The annual gross community primary production was 135gCm−2 yr−1, leading to a low autotrophic annual budget, considering an annual community respiration of 110gCm−2 yr−1. [Copyright &y& Elsevier]

Abstract: In order to characterize the genotoxicity in the Seine estuary and Seine bay, chemical and toxicological analyses were performed on 17 sediments collected in June 2001 and June 2003. Many potent mutagenic and/or carcinogenic compounds – including polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB) and metals – were detected. Those compounds were found to be at relatively high concentrations in the upper part of the Seine estuary but were barely detectable at sites outside the plume from the Seine. The levels of pollution did not vary significantly between the two sampling periods, except that PAH concentrations in sediments collected at Oissel and Le Havre showed a marked increase in June 2003. The toxicity of organic extracts from sediments was evaluated by both embryotoxicity and in vitro genotoxicity (SOS Chromotest) assays. Organic extracts from sediments taken from the Seine estuary appeared significantly more embryotoxic than those from the Seine bay. In addition, the sediment extracts from the upper part of the Seine estuary exhibited higher genotoxicity than those from the lower part, and no genotoxicity was reported for sediments from the Seine bay. The genotoxic activity was detected only after adding an S9 microsomal fraction, suggesting the preponderant involvement of pro-genotoxic organic compounds. In addition, SOS Chromotest responses obtained with purified organic fractions revealed that PAH and, to a lesser extent, unknown polar organic compounds were probably responsible for this genotoxicity. Altogether, these results suggest that sediments from the upper Seine estuary are genotoxic and embryotoxic, and therefore, could be potentially hazardous for species living or feeding in the area. [Copyright &y& Elsevier]

Abstract: In order to understand the hydrodynamic parameters that control the fluvial sediment dynamics on an intertidal mudflat located in a sheltered zone in the upper part (fluvial part) of the macrotidal Seine estuary (France), a two-year field study of high-frequency field measurements was carried out. The bed-level evolution of the mudflat surface was measured from the semi-diurnal period to annual time scales using a high-resolution altimeter. The data showed that the sedimentary patterns on the mudflat were mainly controlled by river flows and tides. During high river flows in winter, sedimentation dominated; suspended particulate matter concentrations were higher, submersion was constant and at semi-diurnal scale, sedimentation duration was more important than erosion due to an asymmetrical tide. By contrast during low river flows in summer, erosion dominated mainly as a result of immersion/emersion of tidal flats during semi-diurnal cycle. From this annual sedimentation–erosion cycle we identify a temporary storage of 10–30% of the fine-grained (&#60;63μm) river-borne particles on mudflats in the upper section of the fluvial Seine estuary during high river flows. River-related sediment fluxes were estimated from the measurement of fine-grained sedimentation zones in the fluvial part of the estuary. The erosion/sedimentation processes were perennial, and the amounts of contributing sediments were directly related to the solid river load. Our results indicate that mudflats in the fluvial part of the Seine estuary play an important role in the downstream transfer of fine-grained suspended particulate matter (SPM) towards the turbidity maximum and the Rouen docks particularly during low river flows, when roughly 30–50% of the SPM originates from the eroded intertidal flats. [Copyright &y& Elsevier]

Concentrations of Cd, Cu, Ni, Pb and Zn were determined in bulk atmospheric deposition collected at five stations in the Seine River basin (France), to evaluate sources and fluxes of atmospheric trace metals. Bulk deposition (wet + dry) was sampled weekly from March 2001 to February 2002 for 4 sites and from March to December 2001 for the last one. The concentrations of the elements in bulk deposition (dissolved + particulate form) followed the order: Zn > Pb > Cu > Ni > Cd. Concentrations of Zn, Pb and Ni were highly correlated with one another, suggesting a common source, related to the combustion of coal and heavy fuel. Metal concentrations in bulk deposition did not exhibit a high degree of temporal variability over the annual cycle and were not obviously related to meteorological parameters (rainfall, wind). Estimates of the total annual direct atmospheric deposition of metals to the Seine Estuary ranged from 16 kg yr− 1 for Cd to 5600 kg yr− 1 for Zn. Loadings of Cd, Cu and Ni from direct atmospheric inputs were less than 1% of those contributed by the Seine River and loadings of Pb and Zn represented 1.27% and 1.56% of the Seine contribution. Direct atmospheric inputs are negligible compared to fluvial inputs, but the indirect atmospheric deposition to the estuary was not estimated. Based on these results, trace metal concentrations in Paris have decreased by a factor of 4.6 for Zn and by a factor of 50 for Ni from 1988 to 2001. Of particular interest is the continued decrease in bulk deposition of Pb during this period, underlining the impact of policy initiatives concerning the reduction of lead on emissions in France. [ABSTRACT FROM AUTHOR]