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Fontanier C.,University of Angers | Fontanier C.,Laboratory for the Study of Marine Bio Indicators LEBIM | Fontanier C.,University of Bordeaux 1 | Fabri M.-C.,French Research Institute for Exploitation of the Sea | And 8 more authors.
Marine Pollution Bulletin | Year: 2012

Benthic foraminiferal assemblages were investigated from two sites along the axis of the Cassidaigne Canyon (NW Mediterranean Sea). Both areas are contaminated by bauxite red mud enriched in iron, titanium, vanadium and chromium. These elemental enrichments are related to bauxite-derived minerals and various amorphous phases. At the shallowest station located very close to the pipe outlet, the benthic living foraminiferal community is characterised by a very low diversity and by an unusual dominance of Gyroidina umbonata and Bulimina marginata. The mechanical stress related to downslope transport of red mud is a likely source of hydro-sedimentary pollution precluding the settlement of diverse fauna. The living and dead foraminiferal faunas from the deepest site are typical of oligo-mesotrophic conditions prevailing in natural environments. There, bauxite residues have obviously no environmental impact on foraminiferal faunas. The bioavailability of trace metals is likely low as elemental enrichments were not observed in foraminiferal test chemistry. © 2012 Elsevier Ltd.

Nardelli M.P.,Marche Polytechnic University | Nardelli M.P.,University of Angers | Jorissen F.J.,University of Angers | Jorissen F.J.,Laboratory for the Study of Marine Bio Indicators LEBIM | And 6 more authors.
Micropaleontology | Year: 2010

The relationships between the quantity and biochemical composition of organic matter and the species diversity and community structure of living benthic foraminiferal assemblages have been investigated at four sites on the Portuguese margin (NEAtlantic). All of the sites are located at approximately 1000m depth. Two out of the four sites are located in the Nazaréand Cascais submarine canyons, while the other two are positioned on the adjacent open slope. The composition and vertical distribution in the sediment of the foraminiferal assemblages have been investigated in the topmost 10cm for the >150μm fraction and in the top cm for the 63-150μm size fraction. Foraminiferal abundance and species richness are related to the quantity and biochemical composition of the sedimentary organic matter, as well as to the stability of the sea floor. The open slope stations are characterised by a relatively low quantity and nutritional quality of organic matter. The faunas of the two open slope stations are much poorer than those found in Nazarécanyon. At both stations, there is a succession of shallow, intermediate and deep infaunal species, suggesting a fairly deep oxygen penetration into the sediment. At the northern open slope station, the faunal density is about two times lower than at the southern station, where the fauna is very largely concentrated in the uppermost half cm. This difference coincides with a lower nutritional quality of organic matter at the northern station. The faunas of the two canyons, where the quantity and nutritional quality of bio-available organic matter are higher, are very different. The rich fauna of Nazarécanyon is characterised by a strong dominance of intermediate and deep infaunal species (e.g. Melonis barleeanus andChilostomella oolina) in superficial sediment layers, suggesting a low bottom-water oxygen concentration and a minimal oxygen penetration into the sediment. InCascais canyon themuch poorer faunas of the superficial sediment layers are characterised by the co-occurrence of shallow, intermediate and deep infaunal taxa, again suggesting a rather limited oxygen penetration into the sediment.We suggest that the relatively low densities in the Cascais canyon could reflect an early stage of ecosystem colonisation after a recent turbidite deposition.

Duros P.,University of Angers | Duros P.,Laboratory for the Study of Marine Bio Indicators LEBIM | Fontanier C.,University of Angers | Fontanier C.,Laboratory for the Study of Marine Bio Indicators LEBIM | And 10 more authors.
Deep-Sea Research Part I: Oceanographic Research Papers | Year: 2011

Living (Rose Bengal stained) benthic foraminifera were investigated at 18 deep-sea stations sampled in the Whittard Canyon area (NE Atlantic). The stations were positioned along 4 bathymetric transects ranging from 300 to 3000 m depth: two along the main canyon axes (Western and Eastern branches) and two along adjacent open slopes (Western and Eastern slopes). The aim of this study was to assess changes of foraminiferal standing stock, composition and microhabitat in relation to the physico-chemical conditions prevailing at and below the sediment-water interface in various canyon and open-slope environments. Minimal oxygen penetration depths and maximal diffusive oxygen uptakes were recorded at upper canyon stations, suggesting a high mineralisation rate. This is confirmed by the high phytopigment concentrations measured in the sediment of the upper canyon axes. Foraminiferal abundance was positively correlated with diffusive oxygen uptake and phytopigment concentration in the sediment. This suggests a control of organic matter fluxes on the foraminiferal communities. Foraminiferal abundance was generally higher along the canyon axis compared to open-slope sites at comparable water depths. The species composition varied with water depth along all four transects, but was also different between canyon branches and adjacent slopes. The silty/sandy intercalations at many of the deeper canyon stations may have been rapidly deposited by fairly recent gravity flows. At station 51WB (3002 m), the faunal characteristics (strong dominance, shallow infaunal microhabitats) suggest that the foraminiferal community is in an early state of ecosystem colonisation after these recent sedimentation events, which would have supplied the important amounts of phytopigments. © 2010 Elsevier Ltd.

Goineau A.,University of Angers | Goineau A.,Laboratory for the Study of Marine Bio Indicators LEBIM | Fontanier C.,University of Angers | Fontanier C.,Laboratory for the Study of Marine Bio Indicators LEBIM | And 15 more authors.
Journal of Sea Research | Year: 2011

In this paper, we investigate the ecology of live (rose Bengal stained) benthic foraminifera collected at 20 stations ranging from 15 to 100 m depth in the Rhône prodelta (Gulf of Lions, NW Mediterranean). These sites were sampled in September 2006, five months after the Rhône River annual flood. Statistical analyses based on foraminiferal communities (> 150 μm) divide our study area into six main biofacies directly related to environmental conditions. Miliolid species are abundant in the relict prodeltaic lobe which is characterised by sand with low organic matter content. Close to the river mouth, the limited oxygen penetration in the sediment combined with important hydro-sedimentary processes constitute stressful conditions for foraminiferal faunas dominated by opportunistic species (e.g. Leptohalysis scottii). With increasing distance from the river mouth, foraminiferal faunas (e.g. Nonionella turgida, Eggerella scabra) adapted to thrive in sediments enriched in Rhône-derived organic matter under more stable hydro-sedimentary conditions appear. In the distal part of the Rhône River influence, benthic species (e.g. Valvulineria bradyana, Textularia agglutinans) living in fine sediment enriched in both continental and marine organic compounds emerge. At the deepest stations located in the south-eastern part of our study area, benthic foraminiferal faunas (e.g. Bulimina aculeata, Melonis barleeanus, Bigenerina nodosaria) are highly diverse, underlining stable environmental conditions characterised by marine-derived organic matter supplies and relatively deep oxygen penetration depth in the sediment. We also compare foraminiferal faunas sampled in September 2006 with communities sampled in June 2005, one month after the Rhône River annual flood (Mojtahid et al., 2009). This comparison suggests that opportunistic species (e.g. B. aculeata, Cassidulina carinata, V. bradyana) have responded to organic matter inputs related to marine primary production in June 2005. © 2010 Elsevier B.V.

Duros P.,University of Angers | Duros P.,Laboratory for the Study of Marine Bio Indicators LEBIM | Fontanier C.,University of Angers | Fontanier C.,Laboratory for the Study of Marine Bio Indicators LEBIM | And 8 more authors.
Marine Micropaleontology | Year: 2012

Dead benthic foraminiferal assemblages were studied in the >. 150. μm fraction of 4-5. cm deep sediment levels at 18 stations in the Whittard Canyon area in June 2007. This sediment layer is composed of fairly recent sediment (<. 312. years). The stations were located along 4 bathymetric transects ranging from 300 to 3000. m depth: two along the main canyon axes (Eastern and Western branches) and two along adjacent open slopes (Eastern and Western slopes). The comparison between the live (Rose-Bengal-stained) communities and the dead assemblages reveals more or less important differences in representation of species which can be attributed to various biological and taphonomic processes. Differences in species composition between live and dead faunas are much larger along both canyon branches than in the open slope environments.In both canyon branches, the population dynamics, such as seasonal response to phytodetritus deposition, certainly contribute to differences between live and dead faunas. For instance, Bulimina marginata, which is usually considered as an opportunistic species is over-represented in the dead assemblage. The fragility of the tests of some species can explain their total absence in the thanatocoenoses. This concerns many organic cemented arenaceous tests, miliolid tests sensitive to dissolution and perforate taxa with thin tests. Furthermore, transport (e.g. sediment gravity flows), active in both canyon branches, leads to an increasing relative contribution of allochthonous individuals, originating from outer shelf and upper canyon sites, towards the deeper canyon stations. Consequently the dead faunas do no reflect local environmental conditions. The high abundance of transported dead foraminifera in both canyon branches leads to important biases in the foraminiferal assemblage composition, but may also significantly bias the interpretation of δ 13C, δ 18O, trace-elements and 14C concentration in foraminiferal shells. It may therefore strongly complicate the reconstruction of environmental parameters such as bottom water temperature or exported paleoproductivity, and radiocarbon dating of the foraminiferal assemblages. Therefore, in both canyon axes, the use of dead foraminiferal faunas to reconstruct paleoenvironmental in situ conditions is precluded. However, the study of dead assemblages in the canyon branches, in particular the quantity of allochthonous foraminifera, can give important clues about the downslope sedimentary dynamics.On both open slopes, despite taphonomic (test destruction) and biological processes (population dynamics), the distribution and the composition of the live fauna resemble those of the dead assemblage. In these areas, dead foraminiferal faunas include much less material derived from downslope transport. Consequently, on the open slope, dead assemblages appear to better reflect local conditions. Therefore, the ecological information obtained from fossil open slope samples can be more reliably used to reconstruct paleoenvironmental conditions. © 2012 Elsevier B.V.

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