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Despite their worldwide distribution and very high densities, the contribution of benthic meiofaunal species to sediment reworking has largely been neglected in bioturbation research. This is partly due to the challenge in obtaining reliable measurements of these minute size organisms. So far, only a handful of studies have investigated the influence of these microbioturbators on particle transport processes at the sediment surface. These studies most often used the surface image analysis (SIA) method, which indirectly estimates surface sediment reworking rate (SSRR) by tracking the position of individuals at the sediment surface over time. Here, focusing on benthic foraminifera, we demonstrate that successive assessments of sediment microtopography mapping using a three-dimensional (3D) sensor can provide direct and accurate quantifications of meiofaunal SSRR, with high spatial and temporal resolutions. This new method is thus particularly suitable to investigating the as-yet-unknown influence of the meiobenthic fauna, such as foraminifera, on particle transport at the sediment–water interface and more generally on the functioning of benthic soft-bottom ecosystems.

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.

Questions Invasiveness depends in part on the ability of exotic species to either exclude native dominants or to fill an empty niche. Comparisons of niches and effects of closely related native and invasive species enable the investigation of this topic. Does Spartina anglica invade European salt marshes through competitive exclusion of the native Spartina maritima or due to the occurrence of an empty ecological niche in highly anoxic conditions? Study Site The Arcachon Bay (France). Methods At three intertidal levels, we quantified competitive response and effect abilities of the two species through a cross‐transplantation removal experiment. We also compared the biomass, root/shoot ratio, productivity and environmental conditions (elevation, salinity, redox potential and soil moisture) of salt marsh communities dominated by the exotic Spartina anglica or the native Spartina maritima at three intertidal levels. Results Both established species showed similar biotic resistance to the invasion of the other species, but the exotic showed important intraspecific facilitation for growth. Species had similar niches and total biomass along a gradient of anoxic conditions, but the exotic had a much higher root/shoot ratio and productivity than the native. Owing to its rhizome density, the exotic showed high ability to increase sediment oxygenation, likely to explain its important intraspecific facilitation. Conclusions Our results showed that the invasion success of S. anglica cannot be explained by the competitive exclusion of the native or by its ability to fill an empty niche along a gradient of anoxia. Its behaviour as a self‐facilitator invasive engineer very likely explains its rapid spread in the Bay and biotic resistance to the colonization of other congeneric species when established in dense patches. Additionally, we suggest that physical disturbance in marsh communities dominated by the native S. maritima may disrupt its biotic resistance against the invasion of S. anglica. With a cross‐transplantation removal experiment, we have assessed the competitive effects and responses of two Spartina species in a European salt marsh. We showed that the native Spartina maritima had a strong biotic resistance to the invasion of Spartina anglica. However, once installed, the exotic Spartina anglica exhibited a self‐facilitating behaviour and strong competitive ability that favoured its spread.

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–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–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.

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 particle mixing intensities (measured by the normal biodiffusion coefficient D b N) were obtained by fitting a continuous time random walk model to in situ measured vertical luminophore profiles. D b N values (mean ± SD) were between 2.99 ± 2.75 and 22.45 ± 43.73 cm² yr−1 within the bare mudflat and between 0.39 ± 0.30 and 18.07 ± 18.14 cm² yr−1 within the Zostera meadow. Spatiotemporal changes in infauna and D b N were lower within the Zostera meadow, which supports the buffering 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 D b 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 D b N and abundances 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 D b 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.

We exposed marine clams (Ruditapes philippinarum) and aquatic worms (Hediste diversicolor) to environmentally relevant concentrations of two metal mixtures each containing three divalent metals [(C₁ in µg/L) cadmium (Cd) 1, mercury (Hg) 0.1, and lead (Pb) 4] and [C₂ in µg/L) Cd 17, Hg 1.1, and Pb 55]. Animals collected in the Arcachon Bay were exposed for 8 days in microcosms made up of a mixed biotope consisting of a water column and natural marine sediment both taken up from the Arcachon Bay. Bioaccumulation analysis showed a significant increase of Cd, Hg, and Pb in clams, particularly at C₂ concentration in the water column reaching, in soft body, 2.3 ± 0.3 µg Cd/g, 0.7 ± 0.2 µg Hg/g, and 45 µg Pb/g dry weight (dw). DNA alterations and upregulation of the cox1 mitochondrial gene were also observed in clam gill after exposure to the metal blend. For worms exposed to the C₂ metal blend, DNA alterations and significant increase of Cd and Hg concentrations were observed reaching 0.5 ± 0.1 µg Cd/g and 2 ± 0.6 µg Hg/g dw.

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. Résumé Les écosystèmes côtiers rendent de nombreux Services Ecosystémiques Culturels (SEC) aux hommes. Peu d’études se sont focalisées sur ces SEC, et encore moins sur les comparaisons des SEC entre pays. Dans le cas des coquillages, l'attention s'est surtout concentrée sur le service rendu concernant la remédiation des nutriments, alors que relativement peu d'études ont concerné les SEC malgré les forts liens historiques, culturels, sociaux et économiques entre les coquillages et les communautés humaines littorales. Les services écosystémiques assurés par la coque commune Cerastoderma edule ont récemment été décrits, les bénéfices de nature culturelle restant pour autant largement méconnus. Ici, nous avons inventorié les SEC rendus par C. edule dans cinq pays occidentaux européens ayant une façade maritime sur l’Atlantique, en classant les exemples avérés de services dans un cadre préalable. Les classes de niveau supérieur étaient inspirées de l’évaluation du Millenium Assessment et de la Classification Internationale des Services Ecosystémiques: inspiration, esprit des lieux, spiritualité et esthétique, loisir et écotourisme, héritage culturel, et éducation. Dix‐neuf autres sous‐classes ont été définies. Nous avons suivi une approche narrative pour mettre en évidence par une analyse semi‐quantitative les points communs et les différences entre pays. Des exemples des SEC rendus par les coques ont été trouvés dans toutes les classes et pour la plupart des pays. Les coques fournissent aux hommes des bénéfices culturels importants et variés à travers les pays européens de la façade atlantique, en faisant un modèle idéal pour l’étude des SEC dans les régions côtières. La plupart des exemples concernait les héritages culturels, mettant en exergue l'importance de cette classe en comparaison d'autres classes ayant reçu plus d'attention comme les loisirs ou l'esthétique. Nous avons également trouvé que les associations culturelles différaient d'un pays à l'autre, même entre pays voisins partageant un fort héritage maritime. L'intensité des liens entre les associations culturelles, le présent ou le passé était également différente entre les pays, avec une association plus forte avec le présent dans les pays du sud, et plus forte avec le passé dans les pays du nord. Comprendre les larges bénéfices rendus par les coques pourrait approfondir la reconnaissance de cette importante ressource littorale, et contribuer à promouvoir les pratiques de développement durable à travers un plus grand engagement des communautés humaines côtières. Cette étude est une étape importante vers une meilleure intégration des SEC dans les environnements côtiers et pourrait être utilisée comme un cadre pour l’étude des SEC rendus par d'autres espèces dans d'autres environnements. Resumen Los sistemas costeros proporcionan numerosos Servicios de Ecosistema Culturales (SEC) al ser humano. Son pocos los estudios que se han concentrado exclusivamente en los SEC y entre estos son aún más escasos los que han establecido comparaciones entre países. En el caso de los servicios del ecosistema derivados de los bivalvos, se ha prestado una atención considerable a la biorremediación de nutrientes y relativamente poca atención a los servicios de ecosistema culturales. Esto a pesar de los fuertes lazos históricos, culturales, sociales y económicos que existen entre los bivalvos y las comunidades costeras. Los servicios de ecosistema proporcionados por el berberecho común, Cerastoderma edule, han sido descritos recientemente, aunque los beneficios culturales de esta especie permanecen en gran medida desconocidos. Este trabajo documenta los SEC proporcionados por C. edule en cinco países a lo largo de la costa Atlántica del oeste de Europa, clasificando y proporcionando ejemplos que evidencian esos servicios en un marco apriorístico. El primer nivel de clasificación, adaptado de la Evaluación de Ecosistemas del Milenio y de la Clasificación Internacional de Servicios del Ecosistema comprende: inspiración; sentido de pertenencia; espirituales y religiosos; estéticos; ocio y eco‐turismo; patrimonio cultural y educativo. Se definieron 19 sub‐clases. Hemos utilizado un enfoque narrativo para señalar a continuación aspectos comunes y diferencias entre países mediante un análisis semi‐cuantitativo. Se proporcionaron ejemplos de los SEC que ofrecen los berberechos en todas las categorías de la clasificación en la mayoría de los países. Los berberechos proporcionan importantes y diversos servicios de ecosistema culturales al ser humano a lo largo del Atlántico en Europa, presentándose como un modelo ideal para estudiar los SEC en las áreas costeras. Muchos de los ejemplos se asocian al patrimonio cultural, destacando la importancia de esta categoría frente a otras que han podido concentrar más atención de la literatura anterior como es el caso del ocio o los estéticos. También hemos detectado que los servicios culturales asociados a los berberechos difieren entre países, incluso entre países vecinos que comparten un importante patrimonio marítimo. La medida en la que esas asociaciones con la cultura forman parte del presente o del pasado es también diferente entre países, mostrándose mucha más relación con el presente en los países del sur mientras se asocia al pasado en los países del norte. Entender de manera más amplia los beneficios que los berberechos proporcionan puede reforzar el reconocimiento de este importante recurso costero y contribuir a la promoción de prácticas de gestión más sostenibles, a través de una mayor implicación de las comunidades locales. Este estudio representa un paso importante para una mejor integración de los SEC en los estudios ambientales costeros y podría ser utilizado como marco de referencia para el estudio de los SEC de otras especies o ecosistemas. Resumo Os sistemas costeiros fornecem muitos Serviços de Ecossistemas Culturais (SEC) para o ser humano. Poucos estudos focaram exclusivamente os SEC comparativamente a outros serviços dos ecossistemas e aqueles que comparam SEC entre países são ainda mais raros. No caso dos moluscos, muitos serviços dos ecossistemas abordaram a bioremediação de nutrientes, com relativamente pouca atenção nos serviços culturais fornecidos, apesar dos fortes vínculos históricos, culturais, sociais e económicos que existem entre as comunidades costeiras e os moluscos. Os serviços dos ecossistemas fornecidos pelo berbigão‐comum, Cerastoderma edule, foram descritos recentemente, mas os benefícios culturais do berbigão ainda são desconhecidos. Este trabalho documenta os SEC fornecido por C. edule em cinco países localizados ao longo da Costa Atlântica da Europa Ocidental, através da classificação de exemplos que evidenciam esses serviços com base numa estrutura previamente definida. O primeiro nível de classificação, adaptado do Millennium Ecosystem Assessment e da Classificação Internacional Comum de Serviços dos Ecossistemas incluiu: inspiração, sentido de lugar, espiritual e religioso, estético, recreação e ecoturismo, valores patrimoniais e culturais e educacionais. Foram definidas 19 subclasses. Seguimos uma abordagem narrativa para extrair semelhanças e diferenças entre os países usando uma análise semi‐quantitativa. Foram fornecidos exemplos de SEC fornecidos pelo berbigão para todas as classes na maioria dos países. O berbigão fornece benefícios culturais importantes e diversos para o ser humano em toda a Europa Atlântica, torna

To investigate bioturbation effects on cadmium (Cd) fluxes from overlying water to sediments, indoor microcosms were developed. The bioturbating organisms were freshwater tubificid worms. Three experimental conditions were studied during 56 d. The three conditions were contaminated water column ([Cd]: 20 μg/L) with or without worms and uncontaminated water column with worms. Cadmium vertical profiles were determined in the pore water and in the sediments, based on six layers (0–0.5, 0.5–1, 1–2, 2–3, 3–5, 5–12 cm). Dissolved oxygen, manganese, sulfate, and particulate manganese were measured. Bioturbation was analyzed using conservative fluorescent particulate tracers. Bioturbation increased Cd flux into the sediments by close to a factor of two. Scavenging of Cd was more efficient in the bioturbated sediments because particles and adsorption sites for Cd were renewed at the sediment‐water interface. Tubificids also increased the thickness of the Cd‐enriched layer. Metals adsorbed on particles at the sediment surface were distributed by bioadvection, which predominated the mixing processes. Bioturbation also modified the vertical profiles of dissolved and particulate manganese and dissolved sulfate but not the profiles of dissolved oxygen. These results indicate that the advective transport of particles by bioturbation and their subsequent modification by redox reactions accelerates the trapping of metals in sediments.

Experiments were performed to investigate the impact of cockle population densityCerastoderma eduleon the resuspension of naturally contaminated sediments collected from the Tamar estuary (SW England). Annular flumes generated tidal-current cycles for 7 to 9 d. The suspended sediment concentration (SSC) at peak flow increased 5-fold with increasing cockle population density, although the 2 highest densities yielded similar resuspension. Polycyclic aromatic hydrocarbons (PAHs) in the sediment were analysed by gas chromatography/mass spectrometry (GC/MS) at the beginning of the experiment, and in the water column of each flume after 2 and 6 d at both the maximum and minimum current speeds. At the end of each experiment sediment erodability was measured as a function of a stepwise increase in current speed. Sediment erosion increased up to 10-fold with increasing cockle population density. However, at the highest density the SSC was lower than that observed for the medium density, probably due to binding resulting from higher mucus secretion and pseudofaeces production. Current-induced resuspension of contaminated sediment was dependent on the density of the cockles. The correlation between the suspended sediment concentrations and the concentrations of PAH was weak for low molecular weight PAHs (phenanthrene and anthracene) due to their higher water solubility. In contrast, higher molecular weight PAHs (fluoranthene, pyrene, benz(a)anthracene and chrysene) showed a strong correlation with suspended particulates as a result of their higher hydrophobicity.