Structure and diversity of shallow soft-bottom benthic macrofauna in the Gulf of Lions (NW Mediterranean).

14 páginas, 10 figuras, 4 tablas.Samples of soft-sediment macrobenthos from 92 sites between 10 and 50 m depth were used to assess (1) the main soft-bottom macrofauna communities in the Gulf of Lions, (2) the different components of the diversity of benthic macrofauna in this area, and (3) the relevance of the use of major taxonomic groups as surrogates for the analysis of the structure and diversity of total macrofauna. Three main communities were identified by cluster analysis and associated procedures. These communities corresponded well to the assemblages recently identified on the basis of polychaete composition. The a-diversity indices were in accordance with those reported for similar communities in the Mediterranean. Conversely, the b-diversity value was higher than the few other data available in the literature for marine soft-bottom macrofauna. The total number of species in the studied area estimated by the ‘‘total species accumulation curve’’ (TS) method was 2,319, which was only 10% higher than the number obtained by extrapolation of the species–area curve. The similarity matrix based on polychaetes correlated best with the one based on total macrofauna. Polychaetes and crustaceans were also the best surrogates of total macrofauna when assessing a-diversity (except in the case of D*). Conversely, molluscs were the best surrogates of total macrofauna b-diversity. Our results show that the choice of an optimal surrogate for total benthic macrofauna depends on the characteristic of the benthic macrofauna to be studied. Moreover, this choice is also dependent on the environment to be studiedThis work is part of the PhD thesis of Ce´line Labrune. It was carried out within the EC Network of Excellence MARBEF. Ce´line Labrune was supported by the SYSCOLAG project run by the Re´gion Languedoc-Roussillon.Peer reviewe

An Invasive Mussel (Arcuatula senhousia, Benson 1842) Interacts with Resident Biota in Controlling Benthic Ecosystem Functioning

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

An Invasive Mussel (Arcuatula senhousia, Benson 1842) Interacts with Resident Biota in Controlling Benthic Ecosystem Functioning

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

Experimental assessment of particle mixing fingerprints in the deposit-feeding bivalve Abra alba (Wood)

Particle mixing induced by the deposit-feeding bivalve Abra alba was assessed using a new experimental approach allowing for the tracking of individual particle displacements. This approach combines the adaptation of existing image acquisition techniques with new image analysis software that tracks the position of individual particles. This led to measurements of particle mixing fingerprints, namely the frequency distributions of particle waiting times, and of the characteristics (i.e. direction and length) of their jumps. The validity of this new approach was assessed by comparing the so-measured frequency distributions of jump characteristics with the current qualitative knowledge regarding particle mixing in the genus Abra. Frequency distributions were complex due to the coexistence of several types of particle displacements and cannot be fitted with the most commonly used procedures when using the Continuous Time Random Walk (CTRW) model. Our approach allowed for the spatial analysis of particle mixing, which showed: 1) longer waiting times; 2) more frequent vertical jumps; and 3) shorter jump lengths deep in the sediment column than close to the sediment-water interface. This resulted in lower DbX and DbY (vertical and horizontal particle mixing bioffusion coefficients) deep in the sediment column. Our results underline the needs for: 1) preliminary checks of the adequacy of selected distributions to the species/communities studied; and 2) an assessment of vertical changes in particle mixing fingerprints when using CTRW

Spatiotemporal changes in surface sediment characteristics and benthic macrofauna composition off the Rhône River in relation to its hydrological regime

International audienceThe consequences of changes in the water flow of the Rhône River on surface sediment characteristics and benthic macrofauna composition were assessed within 3 distinct areas: (1) the delta front, (2) the prodelta, and (3) the distal zone. Five stations were sampled during or closely after: (1) an oceanic flood (April 2007), (2) a generalized flood (May 2008), (3) a Cevenol flood (December 2008), and (4) a dry period (July 2011). Measurements of sediment characteristics included granulometry (D0.5), bulk descriptors of sedimentary organics (OC, TN and THAA), descriptors of labile components of sedimentary organics (chloropigments, EHAA), and both descriptors of origin (Chl-b/Chl-a, C/N) and lability (Chl-a/(Chl-a+Phaeo-a), EHAA/THAA) of sedimentary organics. Sediment Profile Images were collected during April 2007, May 2008 and July 2011. Temporal changes in both sedimentary organics and benthic macrofauna were more important in the delta front and the prodelta than in the distal zone. Bulk characteristics of sedimentary organics presented decreasing inshore/offshore gradients during both April 2007 and July 2011 but not during May and December 2008. There were significant temporal changes in EHAA/THAA at all stations. Changes in benthic macrofauna composition differed between: (1) the delta front and the prodelta, and (2) the distal zone. In the former area, the dry period was associated with establishing a mature community characterized by high abundances and species richness. The best description of spatiotemporal changes in benthic macrofauna composition by surface sediment characteristics was obtained using D0.5, Chl-b/Chl-a, Chl-a/(Chl-a+Phaeo-a) and EHAA, which supports the role of the quality of sedimentary organics in controlling benthic macrofauna composition

Toward a European coastal observing network to provide better answers to science and to societal challenges : The JERICO research infrastructure

The coastal area is the most productive and dynamic environment of the world ocean, offering significant resources and services for mankind. As exemplified by the UN Sustainable Development Goals, it has a tremendous potential for innovation and growth in blue economy sectors. Due to the inherent complexity of the natural system, the answers to many scientific and societal questions are unknown, and the impacts of the cumulative stresses imposed by anthropogenic pressures (such as pollution) and climate change are difficult to assess and forecast. A major challenge for the scientific community making observations of the coastal marine environment is to integrate observations of Essential Ocean Variables for physical, biogeochemical, and biological processes on appropriate spatial and temporal scales, and in a sustained and scientifically based manner. Coastal observations are important for improving our understanding of the complex biotic and abiotic processes in many fields of research such as ecosystem science, habitat protection, and climate change impacts. They are also important for improving our understanding of the impacts of human activities such as fishing and aquaculture, and underpin risk monitoring and assessment. The observations enable us to better understand ecosystems and the societal consequences of overfishing, disease (particularly shellfish), loss of biodiversity, coastline withdrawal, and ocean acidification, amongst others. The European coastal observing infrastructure JERICO-RI, has gathered and organized key communities embracing new technologies and providing a future strategy, with recommendations on the way forward and on governance. Particularly, the JERICO community acknowledges that the main providers of coastal observations are: (1) research infrastructures, (2) national monitoring programs, and (3) monitoring activities performed by marine industries. The scope of this paper is to present some key elements of our coastal science strategy to build it on long term. It describes how the pan-European JERICO community is building an integrated and innovation-driven coastal research infrastructure for Europe. The RI embraces emerging technologies which will revolutionize the way the ocean is observed. Developments in biotechnology (molecular and optical sensors, omics-based biology) will soon provide direct and online access to chemical and biological variables including in situ quantification of harmful algae and contaminants. Using artificial intelligence (AI), Internet of Things will soon provide operational platforms and autonomous and remotely operated smart sensors. Embracing key technologies, high quality open access data, modeling and satellite observations, it will support sustainable blue growth, warning and forecasting coastal services and healthy marine ecosystem. JERICO-FP7 is the European 7th framework project named JERICO under Grant Agreement No. 262584. JERICO-NEXT is the European Horizon-2020 project under Grant Agreement No. 654410. JERICO-RI is the European coastal observing research infrastructure established and structured through JERICO-FP7 and JERICO-NEXT, and beyond

Long-term (1998–2010) large-scale comparison of the ecological quality status of gulf of lions (NW Mediterranean) benthic habitats

12 páginas, 4 tablas, 8 figuras.A comprehensive Mediterranean data set has been used to address 3 questions associated with the use of sensitivity/tolerance based biotic indices to infer the Ecological Quality status (EcoQs) of benthic habitats. Our results showed: (1) a significant effect of the reference database on derived sensitivity/tolerance measure (ES500.05) as well as associated Benthic Quality Index values and derived EcoQs; (2) a lack of correlation neither between BQI and AZTI Marine Biotic Index values nor between BQI and Multivariate-AZTI Marine Biotic Index values; (3) a lack of correlation between the values of the Benthic Habitat Quality Index (index derived from Sediment Profile Imagery) and those of either of the 3 tested biotic indices; and (4) a general agreement between the 3 tested biotic indices in describing the lack of global trend for the EcoQs of the Gulf of Lions despite the occurrence of significant changes in benthic macrofauna composition between 1998 and 2010.This study has been carried out with financial support from the French National Research Agency (ANR) in the frame of the Investments for the future Programme, within the Cluster of Excellence COTE (ANR-10-LABX-45).Peer reviewe

Deltaic and Coastal Sediments as Recorders of Mediterranean Regional Climate and Human Impact Over the Past Three Millennia

International audienc

Producción secundaria de Capitella sp. (Polychatea, Capitellidae) en habitats con niveles de enriquecimiento orgánico diferentes

11 páginas, 5 figuras, 2 tablas.[EN] Three populations of Capitella sp. submitted to three different environmental conditions were monitored during one year in Alfacs Bay (Ebro Delta, NW Mediterranean) to estimate their respective contributions to the secondary production. Yearly secondary production of Capitella sp. at the three sites under study were 0.83 gDW. m-2. y-1 for the disturbed sand site, 3.74 gDW. m-2. y-1 for the typical silt site, and 36.9 gDW. m-2. y-1 for the disturbed silt site. The corresponding P/B ratios were of 4.09 y-1, 3.66 y-1 and 5.71 y-1, respectively. At the two silty sites, Capitella sp. presents: (1) a marked seasonal variability, and (2) high production rates and P/B ratios, which are two characteristics of opportunists. At the disturbed sand site its seasonal pattern is much more stable, and its production much lower (although P/B ratios are still high). The "within site" seasonal differences found between the three populations probably did not result from temporal changes in food quantity nor quality. Nevertheless, differences in protein concentrations may contribute to explain differences in maximal densities and biomasses observed among sites. Our results confirm that Capitella sp. shows a great plasticity relative to environment.[ES] Tres poblaciones del poliqueto Capitella sp. (Capitellidae), sometidas a diferentes condiciones ambientales, se han monitorizado durante un año en la Bahía de Els Alfacs (Delta del Ebro, Mediterráneo noroccidental) con el fin de estimar sus resprectivas contribuciones a la producción secundaria del sistema. La producción secundaria anual de Capitella sp. en las tres localidades estudiadas fue: 0.83 g Peso Seco m-2 año-1 en la zona de arenas perturvadas, 3.74 g Peso Seco m-2 año-1 en la zona de fangos típicos, y 36.9 g Peso Seco m-2 año-1 en la zona de fangos perturbados. Los cocientes P/B correspondientes fueron: 4.09 año-1, 3.66 año-1, y 5.71 año-1 respectivamente. En las dos localidades fangosas, Capitella sp. presenta: (1) una marcada variabilidad estacional, y (2) elevadas tasas de producción y cocientes P/B, ambas características propias de especies oportunistas. En la localidad de arenas perturbadas, el patrón estacional es mucho más estable y la producción mucho menor, si bien el cociente P/B sigue siendo elevado. Los resultados obtenidos sugieren que, probablemente, las diferencias en el tiempo para cada localidad no son el resultado de cambios temporales ni en la cantidad ni en la calidad del alimento disponible. Sin embargo, diferencias en la concentración de proteínas contribuyen a explicar las diferencias, tanto en biomasa como en densidades máximas, observadas entre localidades. Dichos resultados confirman la gran plasticidad de Capitella sp. como respuesta a las condiciones ambientales.This work was partly supported by CICYT grants (AC 16/84, MAR91-0503, and AMB94-0746). D. Martin was supported by a fellowship from the MEC of Spain (ref. number fr93-46037786) and a research contract from the CSIC of Spain.Peer reviewe

The effects of strong winter storm on physical and biological variables at a shelf site in the Mediterranean

International audienc