The chemical composition of a new “mica sandwich” foraminiferal species from the East Coast of Korea: Capsammina crassa sp. nov.

We describe a new agglutinated monothalamous foraminiferal species, Capsammina crassa sp. nov., based on integrated observations of the test morphology and the chemical characteristics of materials composing the test. The new species was found at a depth of <60 m on the East coast of Korea. The test morphology is typical of the genus Capsammina, comprising two or more mica plates with a ring of finely agglutinated mineral grains sandwiched between them and surrounding the cell body. There is no distinct test aperture. Elemental analyses of the agglutinated grains revealed 15 different types of mineral grains of which quartz is the most abundant. The surface areas of grains exposed on fractured surfaces ranged from 1.6 to 7,700 μm2 and the large plate-like grains forming the upper and lower surfaces measured about 420–2,350 μm in maximum width. The new species is morphologically similar to C. patelliformis, however, the differences in size, distribution area and depth support that these two species are distinct. This discovery is the first record of the genus Capsammina from the North Pacific. Therefore, it extends the biodiversity and geographical distribution of the genus Capsammina, which has been reported only from the bathyal NE Atlantic. Our finding also suggests the possibility of additional discovery of monothalamous foraminifera from around Korea

Agglutination of benthic foraminifera in relation to mesoscale bathymetric features in the abyssal NE Atlantic (Porcupine Abyssal Plain)

Abyssal hills, small topographic features rising above the abyssal seafloor (< 1000 m altitude), have distinct environmental characteristics compared to abyssal plains, notably the presence of coarser-grained sediments. As a result, they are a major source of habitat heterogeneity in the deep sea. The aim of this study was to investigate whether there is a link between abyssal hills and the test characteristics of selected agglutinated benthic foraminiferal species. We analysed 1) the overall morphometry, and 2) the granulometric and chemical (elemental) characteristics of the agglutinated tests of ten common foraminiferal species (Adercotryma glomerata, Ammobaculites agglutinans, Cribrostomoides subglobosus, Lagenammina sp.1, Nodulina dentaliniformis, Portatrochammina murrayi, three Reophax sp. and Recurvoides sp. 9) at four sites (two on top of abyssal hills and two on the adjacent plain) in the area of the Porcupine Abyssal Plain Sustained Observatory, northeast Atlantic. The foraminiferal test data were compared with the particle size distribution and elemental composition of sediments from the study sites in order to explore possible grain size and mineral selectivity. We found differences in the visual appearance of the tests (i.e. the degree of irregularity in their shape), which was confirmed by morphometric analyses, related to seafloor topography. The agglutinated foraminifera selected different sized particles on hills and plains, reflecting the distinct granulometric characteristics of these settings. These characteristics (incorporation of coarse particles, test morphometry) could provide evidence for the recognition of ancient abyssal hill environments, as well as other palaeoceanographic settings that were characterised by enhanced current flow. Furthermore, analyses of sediment samples from the hill and plain sites using wavelength dispersive X-ray fluorescence (WD-XRF) yielded different elemental profiles from the plains, probably a result of winnowing on the hills, although all samples were carbonate-rich. In contrast, the majority of the agglutinated tests were rich in silica, suggesting a preferential selection for quartz

Holocene salt-marsh sedimentary infilling and relative sea-level changes in West Brittany (France) using foraminifera-based transfer functions

International audienceIn order to reconstruct the former sea-levels and to better characterize the history of Holocene salt-marsh sedimentary infillings in West Brittany (western France), local foraminifera-based transfer functions were developed using Weighted-Average-Partial-Least-Squares (WA-PLS) regression, based on a modern dataset of 26 and 51 surface samples obtained from salt-marshes in both the bay of Tressseny and the bay of Brest. Fifty cores were retrieved from Tresseny, Porzguen, Troaon and Arun salt-marshes, which were litho- and biostratigraphicaly analyzed in order to reconstruct palaeoenvironmental changes. A total of 26 AMS 14C age determinations were performed within the sediment successions. The Holocene evolution of salt-marsh environments can be subdivided into four stages: (1) a development of brackish to freshwater marshes (from c. 6400 to 4500 cal. a BP); (2) salt-marsh formation behind gravel barriers in the bay of Brest (from 4500 to 2900 cal. a BP); (3) salt-marsh erosion and rapid changes of infilling dynamics due to the destruction of coastal barriers by storm events (c. 2900-2700 cal. a BP); (4) renewed salt-marsh deposition and small environmental changes (from 2700 cal. a BP to present). From the application of transfer functions to fossil assemblages, 14 new sea-level index points were obtained indicating a mean relative sea-level rise around 0.90±0.12 mm a-1 since 6300 cal. a BP

Is the meiofauna a good indicator for climate change and anthropogenic impacts?

Our planet is changing, and one of the most pressing challenges facing the scientific community revolves around understanding how ecological communities respond to global changes. From coastal to deep-sea ecosystems, ecologists are exploring new areas of research to find model organisms that help predict the future of life on our planet. Among the different categories of organisms, meiofauna offer several advantages for the study of marine benthic ecosystems. This paper reviews the advances in the study of meiofauna with regard to climate change and anthropogenic impacts. Four taxonomic groups are valuable for predicting global changes: foraminifers (especially calcareous forms), nematodes, copepods and ostracods. Environmental variables are fundamental in the interpretation of meiofaunal patterns and multistressor experiments are more informative than single stressor ones, revealing complex ecological and biological interactions. Global change has a general negative effect on meiofauna, with important consequences on benthic food webs. However, some meiofaunal species can be favoured by the extreme conditions induced by global change, as they can exhibit remarkable physiological adaptations. This review highlights the need to incorporate studies on taxonomy, genetics and function of meiofaunal taxa into global change impact research

The effect of the sampling strategy on biomonitoring results

International audienceForaminifera (Rhizaria) are single-celled organisms with marine and brackish affinities. They are regarded as valuable bioindicators in transitional areas such as tidal flat and salt marshes. The biomonitoring is the analysis of the species content of samples in order to characterize the environmental status of a given place. The environmental characteristics in aquatic system (both organic and inorganic component) are however under pressure and highly variable. Even situated at short distance quantification/measurement could be different between two samples. As a consequence, the crucial question of the sampling strategy will rise. Most of the studies using foraminifera for biomonitoring were using a single sample. Taken into account the spatial variability, more than two samples in a single place are then mandatory. The objective of the talk is therefore to define the minimum required number of replicates for capturing the variability of the living fauna. Three questions could be asked. How many samples are needed? Which methods should be used to capture the spatial variability? Which could be the influence of the sampling strategy on the biomonitoring results? To answer these questions I propose a review on the scientific results on the topic and a presentation of recent experiment on the subject

Foraminifères benthiques et thécamœbiens, proxys de l’environnement ?

Foraminifera and testate amoebae are protists observed in all marine and continental aquatic environments, respectively. This thesis summarizes the knowledge about the relationships between these organisms and their environment. These parameters are classified into biological factors (food sources), physical (life position in the environment, depth, altitude, substrate nature) or chemical (mineralogical, nutrient resource characteristics). The effects of environmental parameters are studied at continental, regional and local level. After defining the characteristics of these faunal-environmental relationships, this thesis gives two illustrations of the reconstruction of ancient environments, one on the scale of the Holocene and the other on the scale of the Anthropocene

Foraminifères benthiques et thécamœbiens, proxys de l’environnement ?

Foraminifera and testate amoebae are protists observed in all marine and continental aquatic environments, respectively. This thesis summarizes the knowledge about the relationships between these organisms and their environment. These parameters are classified into biological factors (food sources), physical (life position in the environment, depth, altitude, substrate nature) or chemical (mineralogical, nutrient resource characteristics). The effects of environmental parameters are studied at continental, regional and local level. After defining the characteristics of these faunal-environmental relationships, this thesis gives two illustrations of the reconstruction of ancient environments, one on the scale of the Holocene and the other on the scale of the Anthropocene

Significance of replicates: Environmental and paleoenvironmental studies on benthic foraminifera and testate amoebae

Foraminifera (Rhizaria) and testate amoebae (Rhizaria and Amoebozoa) are single-celled organisms with marine and continental affinities. They are regarded as valuable bioindicators in transitional areas such as tidal and salt marshes and have been widely used for (paleo)-environmental characterization. Along-lasting debate regularly occurs on the use of living vs. dead fauna to accurately represent modern environments. Moreover, environmentally based benthic foraminiferal and testate amoebaean studies need a reliable sampling strategy to capture the spatial variability, particularly in transitional environments where patchiness complicates the data interpretations. The objective of the present study is therefore to define the minimum required number of replicates for capturing the variability of either living (environment) or dead (paleoenvironment) benthic foraminifera and testate amoebae. To address this question, 49 samples (i.e., replicates) were selected from a square meter zone in the tidal flat-salt marsh transitional zone along the Canche Estuary (Northern France). The range of faunal spatial variability was measured using geostatistical tools. The minimal number of samples for capturing the patchiness was determined using bootstrap resampling procedure. We provide evidence that for both living and dead fauna more than 26 samples (and even higher for some species) are needed to correctly evaluate the patchiness. Indeed, the living and dead fauna do not follow spatial homogenous trends, and this might bias paleoenvironmental interpretations. The commonly-suggested number of three replicates might not be enough to characterize the fauna in such heterogeneous environments

Distribution of recent foraminifera in high energy environment from the Strait of Bonifacio, Sardinia (Italy)

The ecology of benthic foraminifera is related to the physical and chemical conditions of the bottom environment. Since foraminifera have a short life cycle and big density, they react quickly to environmental changes and can be used as bio-indicators for ecological investigations. This is true for both short and long time-scales and for various marine ecosystems (impacted by pollution, for instance). The understanding of the impact of natural parameters on benthic foraminifera distribution is a obliged prerequisite, before describing anthropogenic impact. More concrete knowledge about the various environmental parameters and their connected benthic foraminiferal community response is presently needed. A better understanding of the mechanisms that determine the distribution of associations in natural environments will allow promoting the use of foraminifera in environmental monitoring to decision-makers and governmental bodies. In this study, we investigate the relationships between the benthic foraminifera (species composition, population density and diversity, assemblage structure and spatial distribution pattern) and environmental parameters (depth, grain size, organic matter). These investigations are based on 31 samples collected in the Strait of Bonifacio. On the basis of a preliminary results, the spatial distribution of the foraminiferal assemblages appears to be strongly correlated to high hydrodynamic energy, sediments grain-size, organic matter content and bathymetry. These natural parameters appear to drive natural benthic changes that should be taken in account before studying polluted coastal environments