Seasonal and spatial variations of saltmarsh benthic foraminiferal communities from North Norfolk, England

Time series foraminiferal data were obtained from samples collected from three sites at Brancaster Overy Staithe, Burnham Overy Staithe and Thornham on the North Norfolk coast over a 1-year period. At each collection point, six environmental variables—temperature, chlorophyll, sand, mud, pH and salinity—were also measured. The principle aim of this study was to examine the benthic foraminiferal fauna in regard to the temporal variability of foraminiferal abundance, seasonal trend, dominant species, species diversity and the impact of environmental variables on the foraminiferal communities in the top 1 cm of sediment over a 1-year time series. The foraminiferal assemblages at the three sites were dominated by three species: Haynesina germanica, Ammonia sp. and Elphidium williamsoni. Foraminiferal species showed considerable seasonal and temporal fluctuation throughout the year at the three investigated sites. The foraminiferal assemblage at the three low marsh zones showed a maximum abundance in autumn between September and November and a minimum abundance observed between July and August. There were two separate peaks in the abundance of Ammonia sp. and E. williamsoni, one in spring and another in autumn. In contrast, H. germanica showed a single peak in its abundance in autumn. A generalized additive modelling approach was used to explain the variation in the observed foraminiferal abundance and to estimate the significant impact of each of the environmental variables on living foraminiferal assemblages, with taxa abundance as the dependent variable. When included in the model as predictors, most of the environmental variables contributed little in explaining the observed variation in foraminiferal species abundance. However, the hypotheses for differences amongst sites, salinity and pH were significant and explained most of the variability in species relative abundance

Response of Benthic Foraminifera to organic matter quantity and quality and bioavailable concentrations of metals in Aveiro Lagoon (Portugal)

This work analyses the distribution of living benthic foraminiferal assemblages of surface sediments in different intertidal areas of Ria de Aveiro (Portugal), a polihaline and anthropized coastal lagoon. The relationships among foraminiferal assemblages in association with environmental parameters (temperature, salinity, Eh and pH), grain size, the quantity and quality of organic matter (enrichment in carbohydrates, proteins and lipids), pollution caused by metals, and mineralogical data are studied in an attempt to identify indicators of adaptability to environmental stress. In particular, concentrations of selected metals in the surficial sediment are investigated to assess environmental pollution levels that are further synthetically parameterised by the Pollution Load Index (PLI). The PLI variations allowed the identification of five main polluted areas. Concentrations of metals were also analysed in three extracted phases to evaluate their possible mobility, bioavailability and toxicity in the surficial sediment. Polluted sediment in the form of both organic matter and metals can be found in the most confined zones. Whereas enrichment in organic matter and related biopolymers causes an increase in foraminifera density, pollution by metals leads to a decline in foraminiferal abundance and diversity in those zones. The first situation may be justified by the existence of opportunistic species (with high reproduction rate) that can live in low oxic conditions. The second is explained by the sensitivity of some species to pressure caused by metals. The quality of the organic matter found in these places and the option of a different food source should also explain the tolerance of several species to pollution caused by metals, despite their low reproductive rate in the most polluted areas. In this study, species that are sensitive and tolerant to organic matter and metal enrichment are identified, as is the differential sensitivity/tolerance of some species to metals enrichment.CNPq [401803/2010-4]; [PEst-OE/CTE/UI4035/2014]info:eu-repo/semantics/publishedVersio

Répartition des foraminifères benthiques actuels sur le plateau continental sénégalais au sud de Dakar

Two hundred and twenty four benthic foraminiferal species were recognized in the total assemblages of fifty samples collected from the Senegalese continental shelf south of Dakar (down to a depth of 200 m). A factor analysis based on nineteen dominant species shows three main factors. The first two seem to be associated with temperature and its seasonal variations; they are depth-related and determine two main faunal changes. The third factor is substrate-related. The main depth-related species are: i) Cribrononion gerthi, Quinqueloculina akneriana, Quinqueloculina lamarckiana, Cribrolinoides curtus, Elphidium fichtellianum and Textularia sagittula in th coastal zone; ii) Discorbinella bertheloti, Cancris aff. C. sagrum, Textularia truncata, Nonion fabum, Bulimina elegans and Hanzawaia solei in the inner shelf; iii) Trifarina bradyana, Trifarina Fornasinii, Uvigerina peregrina and Cassidulina laevigata in the outer shelf. The species that are substrate-related are: i) N. fabum, B. elegans, C. gerthi and H. solei in the fine-grained sands and ii) Lobatula lobatula, C. curtus, T. sagittula and D. bertheloti in the coarse-grained sands. The reduction in planktonic percentage and diversity in the outer shelf are related to the upwelling seasonal influence.Deux cent vingt-quatre espèces de foraminifères benthiques ont été recensées dans les assemblages totaux de 50 échantillons prélevés sur le plateau continental sénégalais au sud de Dakar (jusqu'à 200 m de profondeur). Une analyse factorielle portant sur les 19 espèces dominantes met en évidence trois principaux facteurs de répartition pour les peuplements. Les deux premiers sont en relation avec la température des eaux et avec l'amplitude des variations thermiques saisonnières, elles-mêmes étroitement liées à la profondeur. Ils déterminent deux coupures fauniques vers 25 m et vers 85 m. Le troisième facteur est liéà la nature du sédiment. Les principales espèces dont la répartition est en relation avec la profondeur sont: 1) Cribrononion gerthi, Quinqueloculina akneriana, Quinqueloculina lamarckiana, Cribrolinoides curtus, Elphidium fichtellianum et Textularia sagittula en zone côtière; 2) Discorbinella bertheloti, Cancris aff. C. sagrum, Textularia truncata, Nonion fabum, Bulimina elegans et Hanzawaia solei sur le plateau interne; 3) Trifarina bradyana, Trifarina fornasinii, Uvigerina peregrina et Cassidulina laevigata sur le plateau externe. Celles dont la répartition dépend de la nature du sédiment sont: 1) N. fabum, B. elegans, C. gerthi et H. solei dans les sables fins; 2) Lobatula lobatula, C. curtus, T. Sagittula et D. bertheloti dans les sables grossiers. Sur le plateau externe, la diminution de la diversité et du pourcentage des foraminifères planctoniques semble liée à l'influence des upwellings hivernaux

Modern diatom distribution in mangrove swamps from the Kaw Estuary (French Guiana)

Symposium on the Guiana Coast and Other Mangrove-fringed Shorelines held at the 8th French Sedimentological Congress, Orleans, FRANCE, NOV, 2001International audienceModem diatom assemblages were analyzed in 85 surface sediment samples collected in the Kaw estuary and adjacent mangrove swamps. Samples were collected according to seasonal variations (wet versus dry) and mudbank stability phases, from fluid mudflat to mangrove swamps overgrown with vegetation. According to the diatom species habitat and salinity affinities, the modem distribution shows three main diatom assemblages more related to the sediment stability than the seasonal variations. The fluid mudflat was primarily dominated by marine planktonic species (Coscinodiscus centralis, Cyclotella stylorum, Thalassionema nitzschioides) carried by oceanic waters. These species also dominated the samples located in the estuarine channel of the Kaw River and in adjacent mangrove swamp areas in the upstream portion of the estuary. The occurrence of these marine planktonic species suggests a deep penetration of oceanic water into the estuary. The fluid mudflat was characterized by epipelic species, mostly dominated by species from the genera Gyrosigma, which are characterized by a high motility inside the sediments. This autochthonous epipelic assemblage could be considered as a biological indicator of the fluid mudflat stability. In the mangrove swamp stabilized by vegetation, the diatom assemblages are more diverse and dominated by species from the genera Nitzschia and Navicula. (C) 2004 Elsevier B.V. All rights reserved

Foraminiferal proxies for pollution monitoring in moderately polluted harbors

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Modern benthic diatom distribution in a hypersaline coastal lagoon: the Lagoa de Araruama (RJ), Brazil

International audienceDiatom assemblages identified in 75 surface sediment samples in a shallow hypersaline coastal lagoon (Lagoa de Araruama, R.J., Brazil) are mainly composed of holo-euryhaline and marine euryhaline benthic taxa. The lagoon is characterized by an assemblage dominated by Cocconeis placentula var. euglypta, associated with Catenula adhaerens and Cocconeis diminuta. However, different areas, characterized by specific assemblages, have been identified. Their distribution seems to be related to (1) fluctuations in bathymetry, influenced by water inputs from the ocean and from rivers adjacent to the lagoon; (2) fluctuations in salinity through the influence of marine water and the precipitation-evaporation rate. Moreover, the distribution of associations characterized by the presence of Nitzschia palea, N. pusilla and Fallacia cryptolyra suggests the influence of man-induced activities. Although these diatoms are not dominant, their wide distribution inside the lagoon, favored by local wind-hydrodynamics, suggest a large impact of anthropic activities (e.g. freshwater and organic sewages)

Spatio-temporal distribution of benthic foraminifera in relation to estuarine dynamics (Vie estuary, Vendee, W France)

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Foraminiferal assemblages in a hypersaline lagoon, Araruama (RJ) Brazil

International audienceForaminiferal assemblages were studied in 93 samples collected in the lagoon of Araruama and in the adjacent area. The lagoon of Araruama is one of the largest hypersaline lagoons in the world, with a salinity range of 52-65 %o, Historical reports show that the lagoon has been hypersaline since at least the 16th century. Foraminiferal assemblages are dominated by miliolids, mainly Triloculina oblonga, and rotaliids, with Ammonia tepida and the less abundant Cribroelphidium excavatum var. selseyense, Textulariids are almost absent. This assemblage is similar to those usually reported from hypersaline lagoons with sandy carbonate-rich sediments and from salt marshes. A high proportion of aberrant tests was observed. Anthropogenic stresses do not seem to be responsible for these morphological abnormalities, which are attributed to high salinity conditions and to changes of salinity. However, the higher proportion of Ammonia tepida in the more impacted northern part of the lagoon is probably due to human impact