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Trematodes are the main macroparasites in coastal waters. The most abundant and widespread form of these parasites is metacercaria. Their impact on their host fitness is considered relatively low but metacercarial larvae of some species can have deleterious effects on individuals and/or populations. This review focused on the cockle Cerastoderma edule and four species of the genus Himasthla; a common host–parasite system in marine coastal environments. Our aims were (1) to review literature concerning Himasthla continua, Himasthla elongata, Himasthla interrupta and Himasthla quissetensis in cockles; (2) to provide molecular signatures of these parasites and (3) to analyse infection patterns using a 20-year monthly database of cockle monitoring from Banc d'Arguin (France). Due to identification uncertainties, the analysis of the database was restricted to H. interrupta and H. quissetensis, and it was revealed that these parasites infect cockles of the same size range. The intensity of parasites increased with cockle size/age. During the colder months, the mean parasite intensity of a cockle cohort decreased, while infection occurred in the warmest season. No inter-specific competition between trematode parasites was detected. Furthermore, even if the intensity of H. interrupta or H. quissetensis infection fluctuated in different years, this did not modify the trematode community structure in the cockles. The intensity of infection of both species was also positively correlated with trematode species richness and metacercarial abundance. This study highlighted the possible detrimental role of Himasthla spp. in cockle population dynamics. It also revealed the risks of misidentification, which should be resolved by further molecular approaches.

Despite the role of bioturbation in controlling biogeochemical processes taking place at the sediment-water interface, little is still known about how animal behaviours influence sedimentary biogeochemical processes. In the present work, we used the mud shrimp Upogebia pusilla as model organism to assess the effect of behaviour types/intensities on sediment reworking, bioirrigation and sediment oxygen dynamics based on three sets of seasonal experiments. We identified four main behaviours: “Resting”, “Walking”, “Ventilating” and “Burrowing”. Mud shrimp were much more active (i.e. , not “Resting”) during summer than during winter and to a lesser extent spring due to elevated temperature. There were three distinct components of sediment reworking. The first one consisted in the expulsion of sediment particles from the burrow to the sediment-water interface, the second one to the transfer of sediment downward within the burrow and the third one to the transport and compaction of sediment across burrow walls. Temporal changes in the intensities of all components correlated tightly since they all resulted from “Burrowing”. The temporal dynamics of porewater exchange and oxygen dynamics were clearly discontinuous and in direct relation with “Ventilating”. However, other behaviours, and especially “Burrowing” were also involved in the control of this dynamics through the modulation of oxygen availability within the burrow, which is cuing the onset of ventilation at a 12–25% saturation threshold. These results underline the importance of taking into account changes in animal behaviour types/intensities at the appropriate temporal scales when assessing the impact of bioturbation on biogeochemical processes taking place at the sediment-water interface.

Trematode parasites are distributed worldwide and can severely impact host populations. However, their influence on ecosystem functioning through the alteration of host engineering behaviours remains largely unexplored. This study focuses on a common host parasite system in marine coastal environments, i.e., the trematode Himasthla elongata, infecting the edible cockle Cerastoderma edule as second intermediate host. A laboratory experiment was conducted to investigate the indirect effects of metacercarial infection on sediment bioturbation and biogeochemical fluxes at the sediment water interface. Our results revealed that, despite high parasite intensity, the sediment reworking and bioirrigation rates, as well as nutrient fluxes, were not impacted. This finding was unexpected since previous studies showed that metacercarial infection impairs the physiological condition of cockles and induces a mechanical obstruction of their feet, thus altering their burrowing capacity. There are several explanations for such contrasting results. Firstly, the alteration of cockle behavior could arise over a longer time period following parasite infection. Secondly, the modulation of cockle bioturbation by parasites could be more pronounced in older specimens burying deeper. Thirdly, the intensity of the deleterious impacts of metacercariae could strongly vary across parasite species. Lastly, metacercarial infection alters cockle fitness through an interaction with other biotic and abiotic environmental stressors.

To the best of our knowledge, the understanding of benthic metabolism of coastal sedimentary areas is still limited due to the complexity of determining their true in situ dynamics over large spatial and temporal scales. Multidisciplinary methodological approaches are then necessary to increase our comprehension of factors controlling benthic processes and fluxes. An aquatic Eddy Covariance (EC) system and Benthic Chambers (BC) were simultaneously deployed during the winter of 2013 in the Bay of Brest within a Maerl bed and a bare mudflat to quantify and compare O2 exchange at the sediment–water interface. Environmental abiotic parameters (i.e., light, temperature, salinity, current velocity and water depth) were additionally monitored to better understand the mechanisms driving benthic O2 exchange. At both sites, EC measurements showed short-term variations (i.e. 15 min) in benthic O2 fluxes according to environmental conditions. At the Maerl station, EC fluxes ranged from-21.0 mmol m−2 d−1 to 71.3 mmol m−2 d −1 and averaged 22.0 ± 32.7 mmol m−2 d−1 (mean ± SD), whilst at the bare muddy station, EC fluxes ranged from -43.1mmol m−2 d−1 to 12.1 mmol m−2 d −1 and averaged -15.9 ± 14.0 mmol m−2 d−1 (mean ± SD) during the total deployment. Eddy Covariance and Benthic Chambers measurements showed similar patterns of temporal O2 flux changes at both sites. However, at the Maerl station, BC may have underestimated community respiration. This may be due to the relative large size of the EC footprint (compared to BC), which takes into account the mesoscale spatial heterogeneity (e.g. may have included contributions from bare sediment patches). Also, we hypothesize that the influence of bioturbation induced by large-sized mobile benthic fauna on sediment oxygen consumption was not fully captured by BC compared to EC. Overall, the results of the present study highlight the importance of taking into account specific methodology limitations with respect to sediment spatial macro-heterogeneity and short-term variations of environmental parameters to accurately assess benthic O2 exchange in the various benthic ecosystems of the coastal zone.

Coastal systems provide many cultural ecosystem services (CES) to humans. Fewer studies have focused solely on CES, while those comparing CES across countries are even rarer. In the case of shellfish, considerable ecosystem services focus has been placed on nutrient remediation, with relatively little on the cultural services provided, despite strong historical, cultural, social and economic links between shellfish and coastal communities. The ecosystem services provided by the common cockle, Cerastoderma edule, have recently been described, yet the cultural benefits from cockles remain mostly unknown. Here, we documented the CES provided by C. edule in five maritime countries along the Atlantic coast of western Europe, classifying evidenced examples of services into an a priori framework. The high‐level classes, adapted from the Millennium Assessment and the Common International Classification of Ecosystem Services, were: inspirational, sense of place, spiritual & religious, aesthetic, recreation & ecotourism, cultural heritage and educational. A further 19 sub‐classes were defined. We followed a narrative approach to draw out commonalities and differences among countries using a semi‐quantitative analysis. Examples of CES provided by cockles were found for all classes in most countries. Cockles supply important and diverse cultural benefits to humans across Atlantic Europe, making it an ideal model species to study CES in coastal areas. Most examples were in cultural heritage, highlighting the importance of this class in comparison with classes which typically receive more attention in the literature like recreation or aesthetics. We also found that the cultural associations with cockles differed among countries, including between neighbouring countries that share a strong maritime heritage. The extent to which cultural associations were linked with the present or past also differed among countries, with stronger association with the present in southern countries and with the past in the north. Understanding the wider benefits of cockles could deepen the recognition of this important coastal resource, and contribute to promoting sustainable management practices, through greater engagement with local communities. This study is an important step towards better integration of CES in coastal environments and could be used as a framework to study the CES of other species or ecosystems. A free Plain Language Summary can be found within the Supporting Information of this article.

International audience; Microphytobenthos is most often the primary source of carbon for coastal soft-sediment communities, especially in intertidal and shallow subtidal environments. The influence of benthic macrofaunal organisms on microphytobenthic biomass, spatial distribution and photosynthetic capacities is not only resulting from their feeding intensity but also indirectly from their bioturbation activity, which regulates nutrient fluxes and sediment mixing. This study compares the impact of two species (Hediste diversicolor and Scrobicularia plana) that dominate macrofaunal communities in estuarine intertidal mudflats on microphytobenthic biomass and photosynthetic activity. Imaging-PAM fluorescence was used to non-invasively map the development of microphytobenthic biomass and to assess its spatial extent. Our results showed that, due to intense deposit feeding, Scrobicularia plana quickly limited microphytobenthos growth and photosynthetic activity, even at low density (

Nitrogen availability often limits biological productivity in marine systems, where inorganic nitrogen, such as ammonium is assimilated into the food web by bacteria and photoautotrophic eukaryotes. Recently, ammonium assimilation was observed in kleptoplast-containing protists of the phylum foraminifera, possibly via the glutamine synthetase/glutamate synthase (GS/GOGAT) assimilation pathway imported with the kleptoplasts. However, it is not known if the ubiquitous and diverse heterotrophic protists have an innate ability for ammonium assimilation. Using stable isotope incubations (15N-ammonium and 13C-bicarbonate) and combining transmission electron microscopy (TEM) with quantitative nanoscale secondary ion mass spectrometry (NanoSIMS) imaging, we investigated the uptake and assimilation of dissolved inorganic ammonium by two heterotrophic foraminifera; a non-kleptoplastic benthic species, Ammonia sp., and a planktonic species, Globigerina bulloides. These species are heterotrophic and not capable of photosynthesis. Accordingly, they did not assimilate 13C-bicarbonate. However, both species assimilated dissolved 15N-ammonium and incorporated it into organelles of direct importance for ontogenetic growth and development of the cell. These observations demonstrate that at least some heterotrophic protists have an innate cellular mechanism for inorganic ammonium assimilation, highlighting a newly discovered pathway for dissolved inorganic nitrogen (DIN) assimilation within the marine microbial loop.

The invasive mussel Arcuatula senhousia has successfully colonized shallow soft sediments worldwide. This filter feeding mussel modifies sedimentary habitats while forming dense populations and efficiently contributes to nutrient cycling. In the present study, the density of A. senhousia was manipulated in intact sediment cores taken within an intertidal Zostera noltei seagrass meadow in Arcachon Bay (French Atlantic coast), where the species currently occurs at levels corresponding to an early invasion stage. It aimed at testing the effects of a future invasion on (1) bioturbation (bioirrigation and sediment mixing) as well as on (2) total benthic solute fluxes across the sediment&ndash, water interface. Results showed that increasing densities of A. senhousia clearly enhanced phosphate and ammonium effluxes, but conversely did not significantly affect community bioturbation rates, highlighting the ability of A. senhousia to control nutrient cycling through strong excretion rates with potential important consequences for nutrient cycling and benthic&ndash, pelagic coupling at a broader scale. However, it appears that the variability in the different measured solute fluxes were underpinned by different interactions between the manipulated density of A. senhousia and several faunal and/or environmental drivers, therefore underlining the complexity of anticipating the effects of an invasion process on ecosystem functioning within a realistic context.

Electro-Hydro-Dynamic (EHD) effects could exhibit interesting performances when a moving fluid is needed, as is the case with mono or diphasic thermal management systems [1] or for soft robotics actuators [2]. Indeed, EHD pumps are non-mechanical devices that allow inducing flow motion of dielectric fluids through a channel under the influence of a high electric field (typically 10V/µm). This phenomenon arises from the unbalance between dissociation and recombination of neutral species in the polarized media [3]. In conduction mode, the efficiency of such pumping system is highly depending on the fluid properties and especially the mobility of dissociated species [4].In this paper we present the theory and a methodology associated with a specific test bench that allows investigating in the mobility of dissociated species in various fluids. This makes possible to assess their respective effectiveness for the obtention of high performances EHD pumping microsystems.

International audience; Coastal habitats provide many important ecosystem services. The substantial role of shellfish in delivering ecosystem services is increasingly recognised, usually with a focus on cultured species, but wild-harvested bivalve species have largely been ignored. This study aimed to collate evidence and data to demonstrate the substantial role played by Europe's main wild-harvested bivalve species, the common cockle Cerastoderma edule, and to assess the ecosystem services that cockles provide. Data and information are synthesised from five countries along the Atlantic European coast with a long history of cockle fisheries. The cockle helps to modify habitat and support biodiversity, and plays a key role in the supporting services on which many of the other services depend. As well as providing food for people, cockles remove nitrogen, phosphorus and carbon from the marine environment, and have a strong cultural influence in these countries along the Atlantic coast. Preliminary economic valuation of some of these services in a European context is provided, and key knowledge gaps identified. It is concluded that the cockle has the potential to become (i) an important focus of conservation and improved sustainable management practices in coastal areas and communities, and (ii) a suitable model species to study the integration of cultural ecosystem services within the broader application of 'ecosystem services'.

The assimilation of inorganic compounds in foraminiferal metabolism compared to predation or organic matter assimilation is unknown. Here, we investigate possible inorganic-compound assimilation in Nonionellina labradorica, a common kleptoplastidic benthic foraminifer from Arctic and North Atlantic sublittoral regions. The objectives were to identify the source of the foraminiferal kleptoplasts, assess their photosynthetic functionality in light and darkness and investigate inorganic nitrogen and sulfate assimilation. We used DNA barcoding of a ~ 830 bp fragment from the SSU rDNA to identify the kleptoplasts and correlated transmission electron microscopy and nanometre-scale secondary ion mass spectrometry (TEM-NanoSIMS) isotopic imaging to study 13C-bicarbonate, 15N-ammonium and 34S-sulfate uptake. In addition, respiration rate measurements were determined to assess the response of N. labradorica to light. The DNA sequences established that over 80% of the kleptoplasts belonged to Thalassiosira (with 96%–99% identity), a cosmopolitan planktonic diatom. TEM-NanoSIMS imaging revealed degraded cytoplasm and an absence of 13C assimilation in foraminifera exposed to light. Oxygen measurements showed higher respiration rates under light than dark conditions, and no O2 production was detected. These results indicate that the photosynthetic pathways in N. labradorica are not functional. Furthermore, N. labradorica assimilated both 15N-ammonium and 34S-sulfate into its cytoplasm, which suggests that foraminifera might have several ammonium or sulfate assimilation pathways, involving either the kleptoplasts or bona fide foraminiferal pathway(s) not yet identified. (Less)

Marine sediments are an important source of contaminants since they are susceptible to be remobilized to the water column. By modifying the physical and biogeochemical characteristics of sediments, bioturbation can influence contaminants remobilization. Within bioturbators, mud shrimp are considered as among the most influential organisms in marine soft-bottom environments. The physiological state of mud shrimp can be impaired by bopyrid parasites. The present study aims to evaluate the influence of bopyrid-uninfested and bopyrid-infested mud shrimp on sediment contaminants resuspension. Through a 14-days ex-situ experiment we showed a moderate effect of mud shrimp on contaminant remobilization compared to molecular diffusion without the bioturbator. Conversely, parasite presence significantly impaired contaminant bioaccumulation in mud shrimp and interfered with genetic expression. The weak effect of mud shrimp on contaminant remobilization may be due to trace metal accumulation and thus we suggested to evaluate the influence of contaminants on activities of bioturbating species.

International audience; In coastal environments, bioturbators greatly influence the physical and biogeochemical properties of sediments with consequences for central ecological processes such as erosion dynamics. In addition to their direct impact on sediment stability, bioturbators can have an impact on sediment erosion processes by modulating the growth of microphytobenthic organisms that stabilise the surface layer of sediments. The direct and indirect influences of bioturbators on sediment dynamics depend on the magnitude of their activity and inherently on their physiological state. Bioturbators are infected by various parasites, which have a substantial impact on their physiology and behaviour. However, the knock-on effects of parasites on key ecosystem functions like sediment dynamics remain poorly studied. We conducted flume experiments to investigate the indirect influence of the trematode Bucephalus minimus parasitising the common cockle Cerastoderma edule on the dynamics of sandy sediments enriched or not with microphytobenthos (MPB). Cockles modified bed roughness, sediment surface erodibility and hence destabilised sandy sediments. In sediments not enriched with MPB, both unparasitised and parasitised organisms had a similar impact on the stability of sandy sediments. In contrast, parasitism slightly reduced the destabilisation effect of cockles in MPB-enriched sediments. In the latter, parasitised cockles did not interfere with MPB growth whereas unparasitised organisms constrained the microalgae development. However, the enrichment of the surface layers of sandy sediments with MPB did not modulate the erosion dynamics of these environments. Thus, the lower destabilisation effect of parasitised cockles was not here linked to a stabilisation effect of MPB. When standardised for length, parasitised cockles were lighter than unparasitised organisms. Weakened cockles may have had a lower bioturbation potential than unparasitised conspecifics. If so, the influence parasitised cockles had on sediment erodibility and sediment roughness may have been reduced. The absence of a parasitism effect on the dynamics of MPB-unenriched sediments remains nonetheless unclear.

Although parasites represent a substantial part of marine communities' biomass and diversity, their influence on ecosystem functioning, especially via the modification of host behaviour, remains largely unknown. Here, we explored the effects of the bopyrid ectoparasite Gyge branchialis on the engineering activities of the thalassinid crustacean Upogebia pusilla and the cascading effects on intertidal ecosystem processes (e.g. sediment bioturbation) and functions (e.g. nutrient regeneration). Laboratory experiments revealed that the overall activity level of parasitized mud shrimp is reduced by a factor 3.3 due to a decrease in time allocated to burrowing and ventilating activities (by factors 1.9 and 2.9, respectively). Decrease in activity level led to strong reductions of bioturbation rates and biogeochemical fluxes at the sediment-water interface. Given the world-wide distribution of mud shrimp and their key role in biogeochemical processes, parasite-mediated alteration of their engineering behaviour has undoubtedly broad ecological impacts on marine coastal systems functioning. Our results illustrate further the need to consider host-parasite interactions (including trait-mediated indirect effects) when assessing the contribution of species to ecosystem properties, functions and services.

International audience; The vertical distribution of benthic foraminifera in coastal sediments seems tightly controlled by bioturbation processes. However, it still remains unclear whether living specimens found at depth around biogenic structures actively migrated from the sediment surface to reach oxygenated food-rich micro-environments or have been passively transported by macrobenthic organisms. The present study experimentally demonstrates that the vertical distribution of Ammonia tepida, one of the dominant species of foraminiferal assemblages in temperate intertidal mudflats, is tightly dependent on macrofaunal bioturbation modes and rates. The high degree of similarity between vertical profiles of foraminifera and inert particle tracers revealed that this species is not able to (1) efficiently resist biologically induced downward transport and (2) initiate rapid upward migrations to the oxic zone. The strong decrease of locomotion activity recorded in anoxic conditions suggests that encystment and inactivity are the first strategic responses to sudden oxygen depletion.

Seasonal hypoxia refers to the oxygen depletion that occurs in summer in the bottom water of stratified systems, and is increasingly observed in coastal areas worldwide. The process induces a seasonal cycle on the biogeochemistry of the underlying sediments, which remains poorly quantified. Here, we investigated the sedimentary oxygen consumption within Lake Grevelingen (The Netherlands), a saline coastal reservoir that is impacted by yearly recurrent bottom water hypoxia. Monthly sampling campaigns were conducted throughout 2012 at three sites along a depth gradient. Macrofauna sampling and sediment profile imaging demonstrated how summer hypoxia strongly impacts the benthic communities below 15 m of water depth. Benthic fluxes of oxygen, dissolved inorganic carbon, total alkalinity, and ammonium were determined by closed core incubations, while oxygen depth profiles were recorded by microsensor profiling of sediment cores. Our results reveal a pronounced seasonality in the sedimentary oxygen consumption. Low uptake rates in summer were caused by oxygen limitation, and resulted in the build-up of an “oxygen debt” through the accumulation of reduced iron sulfides. Highest oxygen uptake rates were recorded in fall, linked to the reoxidation of the pool of iron sulfides in the top layer. However, uptake rates remained unexpectedly high during winter and early spring, likely associated with the oxidation of iron sulfides down to centimeters depth due to the electrogenic sulfur oxidation by cable bacteria. Overall, our results suggest that the sedimentary oxygen dynamic in seasonally hypoxic coastal systems is characterized by a strongly amplified “oxygen debt” dynamics induced by cable bacteria.

Our aim in the EU funded JERICO project was to develop a flexible and scalable imaging platform that could be used in thewidest possible set of ecological situations. Depending on research objectives, both image acquisition and analysis procedures may indeed differ. Up to now the attempts for automating image analysis procedures have consisted of the development of pieces of software specifically designed for a given objective. This led to the conception of a new software: AVIExplore. Its general architecture and its three constitutive modules: AVIExplore — Mobile, AVIExplore — Fixed and AVIExplore — ScriptEdit are presented. AVIExplore provides a unique environment for video analysis. Its main features include: (1) image selection tools allowing for the division of videos in homogeneous sections, (2) automatic extraction of targeted information, (3) solutions for long-term time-series as well as large spatial scale image acquisition, (4) real time acquisition and in some cases real time analysis, and (5) a large range of customized image-analysis possibilities through a script editor. The flexibility of use of AVIExplore is illustrated and validated by three case studies: (1) coral identification and mapping, (2) identification and quantification of different types of behaviors in a mud shrimp, and (3) quantification of filtering activity in a passive suspension-feeder. The accuracy of the software ismeasured comparingwith visual assessment. It is: 90.2%, 82.7%, and 98.3% for the three case studies, respectively. Some of the advantages and current limitations of the software as well as some of its foreseen advancements are then briefly discussed.

The aim of the present study was to investigate the influence of the mud shrimp Upogebia pusilla on porewater and solute exchanges in an intertidal Zostera noltei meadow of Arcachon Bay. Laboratory experiments carried out during three seasons showed that U. pusilla strongly enhanced sediment porewater exchange rates (averaging 26, 45 and 71 L m − 2 d − 1 in winter, spring and summer, respectively) in comparison to uninhabited sediments for which these rates were moderate (averaging 9, 9 and 16 L m − 2 d − 1 in winter, spring and summer, respectively). Total Oxygen Uptakes (TOUs) were increased by factors around 2.5 during the three studied seasons whilst oxygen consumption by the shrimp accounted for 64, 28 and 21% of TOU in winter, spring and summer, respectively. U. pusilla also significantly enhanced the uptake of nitrate (up to 13.8-fold in summer) and the release of ammonium (up to 3.0-fold in summer) and silicate (up to 3.8-fold in spring) by the sediment. Overall, our results highlight the key role of U. pusilla in controlling oxygen and nutrient fluxes in Arcachon Bay. Because U. pusilla populations are predominantly found in the sediments of Z. noltei meadows, the full assessment of the functional effects resulting from the decline of this meadow should include the effects associated to the disappearance of U. pusilla as well.

Benthic organisms, in particular bioturbators, can influence erosion processes either by affecting sediment roughness through their mere presence and/or activities, or by modulating sediment characteristics (e.g., silt content, granulometry) and thus altering its erodibility. To date, it was not possible to distinguish the influence of bioturbating species on sediment roughness from their impact on sediment erodibility. Consequently, uncertainties remain regarding the role played by benthic species on sediment dynamics. In this study, we used a canal flume which allows to record the bed shear stress at the surface of a non-cohesive sediment (4% of mud) during erosion experiments, thus allowing to disentangle the influence of bioturbators, here the common cockle Cerastoderma edule, on the two erosion mechanisms. In order to assess the influence of bioturbating species on sediment stability in different environmental situations, we additionally tested for the effects of three factors, i.e. bivalve density, availability of suspended food (i.e. phytoplankton presence) and microphytobenthos (MPB) occurrence, which may modulate the behavior of cockles. We observed that cockles promote the erosion of the surficial layer by increasing its roughness as a consequence of their sediment reworking activity and/or presence at the sediment surface (emerging shell). In contrast, we calculated similar critical bed shear stress for erosion with and without bivalves suggesting that cockles have a minor influence on the erodibility of non-cohesive substrates with a low silt content. The destabilizing effect of cockles increased with the bivalve density whereas it was attenuated by the presence of phytoplankton. We hypothesize that the magnitude of cockles' bioturbation activity was lower when a high proportion of suspended food is available. High concentrations of suspended food may also have enhanced the filtration and biodeposition rates of cockles, thus rapidly leading to the ‘muddification’ of the sediment bed and consequently counteracting with the own destabilizing effect of the bivalves. Finally, the sole presence of MPB did not significantly affect the resuspension dynamics of non-cohesive sediments with a low proportion of mud.

Mud shrimp are considered as among the most influential ecosystem engineers in marine soft bottom environments because of their significant bioturbation activity and their high density. These organisms play a key role on the physical structure of sediments through intense sediment reworking activity and also deeply influence geochemical properties of sediments via frequent bioirrigation events. The influence that mud shrimp have on the environment is related to the magnitude of bioturbation processes and subsequently depends on their physiological condition. In natural environments, several factors act together and influence the well-being of organisms. Among them, the deleterious role of parasites on the physiology and the behavior of their host is well established. Aquatic organisms are also subject to pollutants released by anthropogenic activities. However, the effect of both stressors on the fitness and bioturbation activity of mud shrimp has never been investigated yet. We conducted a 14-day ex-situ experiment to evaluate the influence of trace metal contamination (cadmium Cd) and parasitism infestation on the gene expression (molecular endpoint) and sediment reworking activity (behavioral endpoint) of the mud shrimp Upogebia cf. pusilla. At completion, mud shrimp exhibited substantial Cd bioaccumulation, with parasitized organisms showing a significantly lower contaminant burden than unparasitized specimens. Cadmium contamination induces modifications of gene expression in both unparasitized and parasitized organisms. We report an antagonistic effect of both stressors on gene expression, which cannot be fully explained by a lower Cd bioaccumulation. At the behaviour level, parasitism seems to reduce the sediment reworking activity of mud shrimp, while Cd contamination appears to stimulate this activity. This study highlights that the effects of multiple stressors may be quite different from the effects of each stressor considered individually. It should also motivate for more studies evaluating the influence of multiple stressors on different endpoints encompassing various levels of organization.

Using heat pipe solutions for the thermal management of embedded missiles is all the more complex than military electronic systems have to sustain very harsh environments (accelerations, vibrations and temperatures) for long-term applications. However, Electro-Hydro-Dynamic (EHD) pumps have demonstrated promising performances for draining of fluids. Their main advantage is that no mechanical part is involved during operation. Moreover, compatible with MEMS technologies, they could be miniaturized for very dense electronics. The main goal of this paper was to determine influent design parameters for EHD pumps (made with Cu planar footprints on epoxide FR4 substrates). Various fluids were also tested, showing the most efficient solutions compatible with heat transfer applications.

The assimilation of inorganic compounds in foraminiferal metabolism compared to predation or organic matter assimilation is unknown. Here, we investigate possible inorganic-compound assimilation in Nonionellina labradorica, a common kleptoplastidic benthic foraminifer from Arctic and North Atlantic sublittoral regions. The objectives were to identify the source of the foraminiferal kleptoplasts, assess their photosynthetic functionality in light and darkness and investigate inorganic nitrogen and sulfate assimilation. We used DNA barcoding of a ~ 830 bp fragment from the SSU rDNA to identify the kleptoplasts and correlated transmission electron microscopy and nanometre-scale secondary ion mass spectrometry (TEM-NanoSIMS) isotopic imaging to study

International audience; Several studies highlighted the occurrence of circular pools in intertidal flats of different coastal systems and their transient water chemistry over both tidal and diurnal cycles. However, little is known about (1) the response of benthic biogeochemical reactions and fluxes at the sediment-water interface over such short time scales, and (2) the role of these tidal pools in the biogeochemical functioning of coastal systems. Based on in situ microprofiles and water sampling, we investigated the dynamics of dissolved oxygen (O2), nutrients, sulfides and metals, and the associated fluxes at the sediment-water interface in tidal pools from the Arcachon Bay (Atlantic coast of France). Our integrative approach included several tidal and diurnal cycles over two different seasons in the presence and absence of Zostera noltei. The results show that water temperature and light irradiance were the main factors driving the biogeochemical functioning of the tidal pools, as they controlled the physiological activity of the microphytobenthos. Changes in light radiations induced diurnal fluctuations of O2 concentrations within surficial sediment, thus resulting in fluctuations of the O2 diffusive fluxes at the sediment-water interface and of the O2 penetration depth in sediment. At high tide, the increase in turbulence above the sediment induced the advection of oxygenated water within the first millimeters of sediment, resulting in a significant increase in porewater O2 concentrations and sediment O2 penetration depth. Porewater sulfide concentrations and apparition depth were concomitant with the O2 dynamic over both diurnal and tidal cycles, indicating that intermediate redox diagenetic processes were impacted by O2 dynamic over such short time-scale. The rapid changes in redox processes in the sediment column are confirmed by a significant flux of dissolved manganese toward the water column during nighttime. The consumption of nitrate and the release of ammonium and phosphate, associated to the mineralization of the organic matter in the surface sediment did not appeared related however to such short time cycles. The efflux of dissolved silica from the sediment was most likely associated with the enhanced dissolution of Si-bearing particles in surface sediment at higher temperatures, although silica uptake by Z. noltei was also noted. This study clearly shows that tidal pools function as natural incubators of transient biogeochemical processes. A rough assessment of the nutrient budget at the scale of the bay indicates the tidal pools may contribute significantly to the biogeochemical functioning of Arcachon Bay.

The mud shrimp Upogebia pusilla is a deep-burrowing bioturbator widespread along the Northeast Atlantic and Mediterranean coasts, where it is recognized as an ecosystem engineer. Parasitism is an important factor impacting such species’ activities, and thus ecosystem functioning. At least two parasite species occur in U. pusilla: the bopyrid isopod Gyge branchialis and an undescribed trematode. This study, carried out in Arcachon Bay, France (44°40′N, 1°10′W), over 2 years (2014–2015), had two goals: (1) to identify the trematode occurring in U. pusilla and (2) to assess the interactions between the two parasites within their host. Using molecular techniques, the trematode was identified as Maritrema sp. (Microphallidae). Monthly samples taken over 2 years at a single site, and a ten-site spatial survey in June 2014 showed that there was a negative association in the occurrence of the two parasites in their host over time and amongst sites: bopyrid-infested mud shrimp harbored lower trematode infections compared to bopyrid-free individuals. In addition, the abundance of trematodes was lower in the bopyrid-infested gill compared to the uninfested gill of bopyrid-infested individuals. It suggests that G. branchialis interferes with Maritrema sp. establishment in the mud shrimp. Conversely, the trematode appeared not to have a negative effect on bopyrid presence. The reduction of Maritrema sp. infection by G. branchialis is mainly due to the alteration of U. pusilla fitness (indirect interaction), and to a lesser extent, to overlap of parasites’ niches (direct interaction). Accordingly, interactions between these two parasites can be classified as amensalism.

Conformai coating has been traditionally used to protect Printed Circuit Board Assemblies (PCBA) in harsh environments. The benefit of conformal coating is usually enhanced resistance to mechanical and thermal stresses. Various coating techniques exist, including brushing, dipping and spraying. Today, automation makes selective coating possible. The biggest improvements include: no masking time before coating, chemicals confinement and delivery of a replicable and repeatable process. When using an automated platform, a balance between two major problems must be considered: minimum pattern size and specified thickness range. At the same time, current improvements in selective coating must deal with new schemes: heterogeneous integration and high-density integration. Among drop-on-demand solutions, inkjet is used extensively for printing applications while jetting based on mechanical collision is used in advanced packaging. Based on inkjet knowhow, a theoretical approach has been introduced and then compared with actual experimental results. Both areas are discussed and combined in this paper.

Seasonal changes in sediment particle mixing, surface sediment and seagrass charac teristics, and benthic infaunal composition were measured in Arcachon Bay (France), within both a well-developed Zostera noltei meadow and a bare sediment mudflat. Sediment par- ticle mixing intensities (measured by the normal biodiffusion coefficient Db N ) were obtained by fitting a continuous time random walk model to in situ measured vertical luminophore profiles. Db N values (mean ± SD) were between 2.99 ± 2.75 and 22.45 ± 43.73 cm 2 yr −1 within the bare mud- flat and between 0.39 ± 0.30 and 18.07 ± 18.14 cm 2 yr −1 within the Zostera meadow. Spatiotempo- ral changes in infauna and Db N were lower within the Zostera meadow, which supports the buffer- ing effects of seagrass meadows on biological sedimentary processes. Within the Zostera meadow, root biomass declined during the survey, in correlation with increases in (1) the mean value and the variability of Db N and (2) the spatial variability of infaunal composition with a decrease in the dominant polychaete Melinna palmata. At this station, similarity matrices of mean Db N and abun- dances of a set of 3 infaunal species (including M. palmata) correlated significantly, which further supports the key role of this species in controlling sediment particle mixing through sediment stabilization. When considering the whole data set, the similarity matrices of the coefficients of variation of Db N and of the abundances of a set of 5 species (Abra segmentum, Glycera convoluta, Tubificoides benedii, Heteromastus filiformis, Ruditapes phillipinarum) correlated significantly, which supports the suspected role of these species in controlling sediment particle mixing.

The influence of burrowing invertebrates on the functioning of soft-bottom ecosystems is tightly dependent on their physiological state, which may itself be strongly affected by parasite infestation. However, the dynamics, prevalence and physiological consequences of parasitism remain poorly known in many species, such as sediment-dwelling crustaceans. During the present study, we investigated the effects of the ectoparasite (bopyrid) isopod Gyge branchialis on the fitness of the gebiidean mud shrimp Upogebia pusilla. A spatial survey conducted in June 2013 at 10 stations scattered across intertidal seagrass meadows of Arcachon Bay (44°40′N, 1°10′W) showed that on average 16 % of mud shrimp were infested by G. branchialis. Moreover, a temporal survey carried out at one of these stations over the year 2014 revealed that prevalence remained relatively high throughout the year, ranging from 10 to 33 %. This interaction has various physiological consequences for U. pusilla. In particular, infested mud shrimp consistently exhibited a significant deficit in total length and individual dry weight as compared with non-infested specimens. Moreover, 89 % of infested males were feminized (i.e., developed female secondary sexual characters), whereas infested females were never ovigerous. Our results demonstrate that G. branchialis strongly impair U. pusilla fitness including its ability to reproduce. Accordingly, through their (1) potential impact on mud shrimp abundances and (2) alteration of their physiological state, high bopyrid infestation could profoundly alter the bioturbation activity of mud shrimp populations and overall their influence on the functioning of soft-bottom ecosystems in Arcachon Bay.

The effects of temperature and food addition on particle mixing in the deposit-feeding bivalve Abra alba were assessed using an experimental approach allowing for the tracking of individual fluorescent particle (luminophore) displacements. This allowed for the computations of vertical profiles of a set of parameters describing particle mixing. The frequency of luminophore displacements (jumps) was assessed through the measurement of both waiting times (i.e., the time lapses between two consecutive jumps of the same luminophore) and normalized numbers of jumps (i.e., the numbers of jumps detected in a given area divided by the number of luminophores in this area). Jump characteristics included the direction, duration and length of each jump. Particle tracking biodiffusion coefficients (Db) were also computed. Data originated from 32 experiments carried out under 4 combinations of 2 temperature (Te) and 2 food addition (Fo) levels. For each of these treatments, parameters were computed for 5 experimental durations (Ed). The effects of Se, Fo and Ed were assessed using PERmutational Multivariate ANalyses Of VAriance (PERMANOVAs) carried out on vertical depth profiles of each particle mixing parameter. Inversed waiting times significantly decreased with Ed whereas the normalized number of jumps did not, thereby suggesting that it constitutes a better proxy of jump frequency when assessing particle mixing based on the measure of individual particle displacements. Particle mixing was low during autumn temperature experiments and not affected by Fo, which was attributed to the dominant effect of low temperature. Conversely, particle mixing was high during summer temperature experiments and transitory inhibited by food addition. This last result is coherent with the functional responses (both in terms of activity and particle mixing) already measured for individual of the closely related clam A. ovata originating from temperate populations. It also partly resulted from a transitory switch between deposit- and suspension-feeding caused by the high concentration of suspended particulate organic matter immediately following food addition.

The pan-European MacroBen database was used to compare the AZTI Marine Biotic Index (AMBI) and the Benthic Quality Index (BQIES), 2 biotic indices which rely on 2 distinct assessments of species sensitivity/tolerance (i.e. AMBI EG and BQI E[S]0.05) and which up to now have only been compared on restricted data sets. A total of 12 409 stations were selected from the database. This subset (indicator database) was later divided into 4 marine and 1 estuarine subareas. We computed E(S50)0.0 in 643 taxa, which accounted for 91.8% of the total abundances in the whole marine indicator database. AMBI EG and E(S50)0.05 correlated poorly. Marked heterogeneities in E(S50)0.0 between the marine and estuarine North Sea and between the 4 marine subareas suggest that sensitivity/tolerance levels vary among geographical areas. High values of AMBI were always associated with low values of BQIES, which underlines the coherence of these 2 indices in identifying stations with a bad ecological status (ES). Conversely, low values of AMBI were sometimes associated with low values of BQIES resulting in the attribution of a good ES by AMBI and a bad ES by BQIES. This was caused by the dominance of species classified as sensitive by AMBI and tolerant by BQIES. Some of these species are known to be sensitive to natural disturbance, which highlights the tendency of BQIES to automatically classify dominant species as tolerant. Both indices thus present weaknesses in their way of assessing sensitivity/tolerance levels (i.e. existence of a single sensitivity/tolerance list for AMBI and the tight relationship between dominance and tolerance for BQIES). Futurestudies should focus on the (1) clarification of the sensitivity/tolerance levels of the species identifiedas problematic, and (2) assessment of the relationships between AMBI EG and E(S50)0.05 within and between combinations of geographical areas and habitats.

This review lists and discusses the different methods currently available to assess sediment reworking by benthic infauna. Direct methods are used to estimate the amount of sediment transported by infauna at the sediment-water interface during a given period of time. Particle-tracer methods are used to quantify the vertical distribution of particle tracers within the sediment column. Tracers are classified based on their mode of introduction at the sediment-water interface (i.e. whether they occur naturally or are deliberately introduced at the onset of the experiment). The main characteristics of each method, including modelling aspects, are presented, and their respective advantages and drawbacks are outlined with a particular emphasis on their accuracy, spatial (i.e. both horizontal and vertical) and temporal resolutions. Direct and particle-tracer methods assess different components of sediment reworking. Selection of the most appropriate approach depends on the specific question(s) to be answered, as well as other factors, including the behaviour of the organisms studied, the spatial and temporal scales considered, and whether the experiments are carried out in situ or under controlled laboratory conditions.

The ability of the two synthetic marine biotic indices, AMBI and M-AMBI, to account for changes in the ecological quality of coastal soft bottoms of Reunion Island according to disturbances was assessed from macrobenthic samples collected in five sectors between 1994 and 2004. Samples were collected under non-perturbed conditions and at two sites subjected to heavy organic enrichment. Both indices are based on a classification of macrofauna into ecological groups (EG), and their transfer to tropical waters required some adaptations. These indices proved efficient in detecting a degradation of habitat quality. Their use resulted in the classification of all sites sampled between 1996 and 1998 as "good" or "high". M-AMBI nevertheless tended to result in the attribution of a slightly worse ecological quality status than AMBI. Together with an update of the EG species list for the Indian Ocean area, our results support the extension of both indices for the assessment of tropical soft bottoms.

The mysid Heteromysis (Heteromysis) microps is reported for the first time in the Bay of Biscay. During surveys carried out between March and September 2015 in Arcachon Bay, mysid specimens were fortuitously collected from Upogebia pusilla burrows. Details on morphology, colour pattern and behaviour of H. microps are provided. Commensalism was frequently mentioned for Heteromysis species but never reported for H. microps. In this study, commensalism seems to be proved between the mysid and its host U. pusilla.

The quantitative relationship between activity (as detected by the comparison of grey levels in successive images using automated software) and sediment reworking in the deposit- feeding bivalve Abra ovata was investigated based on simultaneous and continuous measurements using laser telemetry, luminophore tracers, and image analysis. Total activity included both feeding (siphoning) and shell and/or foot activity. Sediment reworking was assessed through the measure- ments of surface sediment handling and vertical sediment mixing during 2 separate experiments. Surface sediment handling correlated positively with surface feeding activity. Shell and/or foot activ- ity induced oscillatory movements of the superficial sediment layer but did not account for true ver- tical sediment mixing. Conversely, feeding activity induced intense vertical sediment mixing. Quan- titative changes in feeding activity and vertical sediment mixing based on a biodiffusion model were positively correlated. These results underscore the importance of considering both the nature and intensity of infaunal activity when parameterizing models of sediment reworking.

The filtration activity of the Mediterranean mussel, Mytilus galloprovincialis, was assessed under different concentrations and compositions of seston by using a new automated image acquisition and analysis system. This approach allowed for frequent and simultaneous measurements of valve gape and exhalant siphon area. Filtration rates were measured through clearance measurements whereas pumping rates were measured using hot-film probes. The average filtration rate (17.5 l g h−1 DW−1 for a 0.36 g DW mussel) recorded during the present study was higher than those available for Mytilus edulis when standardized to flesh dry weight but almost equivalent (17.5 l h−1 g DW−1 for a 53 mm shell length mussel) to those rates when standardized to shell length. Immediately after the addition of algal cells (Isochrysis galbana; 4.5 μm in size), valve gape, exhalant siphon area and filtration rate increased quickly as mussels reached their maximum filtration activity. These three parameters then gradually decreased until complete closure of the shell. The algal cell concentration inducing this transition was close to 800 cells ml−1 and 0.5 μg Chl a l−1. When algal concentration was maintained above this threshold by successive algal additions, both valve gape and exhalant siphon area remained maximal. Temporal changes in the exhalant siphon area were continuous as opposed to those of valve gape. Therefore, despite the significant correlation between these two parameters, valves and siphon were sometimes dissociated due to a reduction of the area or even a closure of the exhalant siphon while the valves remained open. The velocity of exhaled water tended to be constant irrespective of exhalant siphon area and thus pumping rates were a linear function of exhalant siphon area. Consequently, reductions in exhalant siphon area and pumping rate were almost similar in M. galloprovincialis. Our results thus clearly support the hypothesis that exhalant siphon area constitutes a better proxy of pumping rate than valve gape as already suggested for Mytilus edulis. Finally, the high filtration rates measured during the present study together with the high concentrations of inorganic matter (> 40 mg DW l−1) requested to alter those rates suggest that the studied mussels were well adapted to oligotrophic waters featuring strong hydrodynamism and frequent sediment resuspension events.

The activity and surface sediment displacement by the terebellid polychaete Eupolymnia nebulosa were monitored, using new image acquisition and image analysis procedures. We used a video sensor mounted on a motorized table, to acquire adjacent images of the whole studied aquarium within about 2 s. These images were then grouped within a composite image acquired every 15 s. Consecutive composite images were compared to infer activity and surface sediment displacement. This procedure proved efficient for E. nebulosa as indicated by (1) the continuity of the tentacles within composite images, and (2) the direct comparison of images and detected activities. There were important temporal changes in the relative importance of the three main types of activity: feeding, tube-building and (both partial and total) emergence from the tube, accounting, respectively, for 75, 15 and 10% of the entire experiment duration. Activity intensity (cm2 min-1) was assessed through the surface of pixels with grey levels differing by more than 20 (on a 0–255 scale) between two consecutive images. Feeding was associated with low activity intensity, whereas tube-building and emergence from the tubes were associated with high activity intensities. Surface sediment displacement mostly resulted from tentacle activity both during feeding and tube-building and was almost zero when worms emerged from their tube. We used our experimental set up to assess spatial changes in activity intensity and particle displacements along the tentacles. Most of the activity occurred within the first 4–6 cm from the tube aperture. Particle loss during their transfer along the tentacles preferentially affected larger particles as postulated by the model of particle selection and transport in tentaculate deposit-feeders. Moreover, the speed of the particles along the tentacles correlated negatively with their size. This contributed to increase in the residence time of larger particles on the tentacles and thus, to further enhance their probability of being lost. The size distributions of particles during feeding and tube-building did not differ significantly although visual observations confirmed the preferential use of larger particles for tube-building. This suggests the existence of a sorting step occurring elsewhere than on the tentacles as already demonstrated for spionid polychaetes.