86,648 research outputs found
Significance of replicates: Environmental and paleoenvironmental studies on benthic foraminifera and testate amoebae
No full textForaminifera (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
Methods relieving comparison of living and death assemblages
No full textLiving (LAs) and death assemblages (DAs) from the same samples (sites) can be compared based on total densities, species densities, species richness and heterogeneity (evenness). Preferably densities (standing crop), obtained by normalization of absolute frequencies to unit sample size, should be used to compare samples, especially for LAs. Combinations of the above four characteristics enable a better insight into the relations between LAs and DAs. The 'Incorporation Value' weighs the proportions of living individuals on total individual numbers with similarities in species composition between both assemblages, yielding the instantaneous integration grade of living individuals into the death assemblage. Diversity diagrams based on species richness (abscissa) and heterogeneities (ordinate), standardized over all investigated samples, simultaneously characterize differences in diversities. The standardized vector between LA and DA in the above-mentioned coordinate system characterizes differences in species richness and heterogeneity in a combined manner, where all coefficients of species richness and heterogeneities can be used
Thirty new records of marine benthic Foraminifera from Korean waters
No full textAs a part of a survey of indigenous biological resources of Korea, 30 marine benthic foraminiferal species
belonging to 24 genera and seven orders (Astrorhizida, Lagenida, Lituolida, Miliolida, Robertinida,
Rotaliida and Textulariida) were identified. Bottom sediment samples were collected from eight stations
on the west and east coast of South Korea, in April 2015 and May 2016, respectively. Ten species
belonging to nine genera and five orders (Lagenida, Lituolida, Robertinida, Rotaliida, Textulariida) were
identified in the Yellow Sea. Among these taxa, Rotaliida was the dominant order, represented by four
species: Evolvocassidulina tenuis (Phleger & Parker, 1951), Cibicides mabahethi Said, 1949, Cibicides
pseudolabatulus Perelis & Reiss, 1975 and Cibicidoides barnetti Bermudez, 1949. Twenty species
belonging to 15 genera and five orders (Astrorhizida, Lagenida, Lituolida, Miliolida, and Rotaliida) were
identified from the East Sea and the Lagenida was the dominant order, represented by 11 species: Lagena
strumosa Reuss, 1858, Lagena nebulosa (Cushman, 1923), Lagena striata var. semiornata Reuss, 1863,
Procerolagena cylindrocostata Albani & Yassini, 1989, Fissurina bispinata Ujiié, 1963, Oolina laevigata
d’Orbigny, 1839, Polymorphina amplissima McCulloch, 1977, Polymorphina subelliptica McCulloch,
1977, Guttulina succincta McCulloch, 1977, Guttulina neoproblema McCulloch, 1977 and Lagenosolenia
obtecta McCulloch, 1977. The findings described here increased the number of foraminiferal species
in Korea to approximately 1060, and contribute to our understanding of the diversity of foraminifera in
Korean waters
Benthic foraminifera as a bioindicator of the environmental quality: a case study from the lagoon of Santa Gilla (Cagliari, Italy)
No full textBenthic foraminifera are increasingly used as environmental bio-indicators of pollution in coastal and marginal marine settings. Their community structure provides useful information on the general characteristics of the environment quality and some species are sensitive to specific environmental parameters (e.g., ALVE, 1991, 1995; YANKO et alii, 1994, 2002; COCCIONI, 2000; SAMIR, 2000; DEBENAY et alii, 2001, 2005; GESLIN et alii, 2002; COCCIONI et alii, 2003, 2005; ARMYNOT DU CHÂTELET et alii, 2004; COCCIONI & MARSILI, 2005; FRONTALINI & COCCIONI, 2008).
The lagoon of Santa Gilla, on an area of about 13 km2, is located on the southern coast of Sardinia (Italy) and communicates with the Mediterranean through a narrow channel. On the northern shore, the lagoon has two major freshwater inflows from the Rii Mannu and Cixerri rivers. On the west, the on-shore industrial area and the urban area of Cagliari discharged untreated wastewater from the mid-1960s to mid-1980s (DEGETTO et alii, 1997).
Sediment samples were collected from 18 stations during October 2006. Physicochemical data of water, geochemical, sedimentological, and benthic foraminiferal data (biocenosis and trace element contents in foraminiferal tests) have been analyzed to investigate the relationship between these sensitive microrganisms and trace element pollution.
The analysis of sediments indicated that the lagoon is deeply affected by trace element pollution (Cd, Ni, Pb, Zn and Hg). The biocenosis of the lagoon are largely dominated by Ammonia tepida, Haynesina germanica and Cribroelphidium oceanensis and, subordinately, by bolivinids.
Foraminiferal species and trace element concentrations were investigated both with bivariate (correlation matrix) and multivariate techniques of principal component analysis (PCA) and cluster analysis. Statistical analysis shows a possible control of these pollutants both on the taxonomic composition of the benthic foraminiferal assemblages and the development of test malformations which is used as additional tool for the pollution monitoring.
This study confirms and supports the suitability of studying benthic foraminifera as a technique for the in situ continuous bio-monitoring of trace element pollution of coastal marine sediments. This study was carried out within the framework of the ForamLag Project aimed at studying the response of benthic foraminifera to contaminants in the main Italian lagoons
STUDIO DEL COMPORTAMENTO DI UN LAMINATO RINFORZATO IN CARBONIO AD ALTE VELOCITÀ DI DEFORMAZIONE
No full textNegli ultimi anni c’è stata una costante ricerca mirata ad ottenere materiali più leggeri da applicare in differenti settori dell’industria automobilistica e aeronautica con lo scopo di ridurre l’uso del solo alluminio. I laminati, comunemente chiamati FML (Fiber Metal Laminate), sembrerebbero rispondere bene a questo tipo di richiesta, tant’è che il loro uso è già presente nel mondo aeronautico. In generale essi sono strutture ibride con lamine sottili in materiale metallico rinforzare con strati di fibra di materiale polimerico; a seconda del tipo di rinforzo che si usa possono aversi differenti tipologie.
In questo lavoro è stato testato in condizioni sia statiche che dinamiche, mediante l’utilizzo della barra di Hopkinson, uno dei tre laminati più diffusi in commercio, il CARALL, dove gli strati di rinforzo sono in carbonio. Lo studio è supportato da una analisi DIC per la misura effettiva delle deformazioni e da un modello numerico opportunamente calibrato
Osmium Isotopic Evidence for Eccentricity‐Paced Increases in Continental Weathering During the Latest Hauterivian, Early Cretaceous
No full textAbstract The 405‐kyr eccentricity cycle is a consistent orbital parameter throughout the Phanerozoic that is associated with long‐term variations in global continental weathering. However, a lack of reliable geological evidence has hampered the understanding of the relation between the 405‐kyr eccentricity cycle and continental weathering during the Cretaceous. Os isotopic ratios (187Os/188Os) of the sedimentary record reflect the balance between radiogenic Os derived from continental weathering and Os derived from unradiogenic sources (e.g., hydrothermal activity, weathering of mafic rocks, and extraterrestrial sources). This ratio is therefore considered as a good proxy for the evaluation of short‐term changes in continental weathering patterns. To trace orbital‐paced continental weathering, this study reconstructs the marine Os isotopic records in upper Hauterivian to lower Barremian (Lower Cretaceous) carbonate rocks in central Italy, where previous studies have reported that variations in clay mineral composition are paced by the 405‐kyr cycle. Our new Os isotopic record documents periodic oscillations of 187Os/188Os between 0.7 and 0.9 that correspond to the 405‐kyr Earth's eccentricity cycle. Because the sedimentary interval with radiogenic 187Os/188Os values (∼0.9) corresponds to a time interval characterized by a humid climate in areas surrounding the Tethys, variations in the 187Os/188O values likely reflect cyclic changes in continental weathering caused by eccentricity‐paced intensification of monsoonal activity at low latitudes. This variation could have been further amplified by increased input of radiogenic Os from Paleozoic shale and Precambrian crust at higher latitudes that resulted from a latitudinal shift of the intertropical convergence zone
Sediment oxygen demand and benthic foraminiferal faunas in the Arabian Gulf: A test of the method on a siliciclastic substrate
No full text: In this study, we investigated the relationship between environmental parameters (water and sediment) and benthic foraminiferal assemblages found in nearshore siliciclastic sediment in the Arabian Gulf. Nearshore marine water and sediment samples were collected from a beach on the Gulf of Bahrain located south of Al Khobar, Saudi Arabia. The water samples were analyzed for biochemical oxygen demand (BOD5) and other chemical analyses. The sediment samples were tested for sediment oxygen demand (SOD) and heavy metal analysis. Results showed the BOD5 levels were below the detection limit (<1 ppm), while the mean SOD value was 0.97 ± 0.08 g/m2·day. The water and sediments were unpolluted and free of eutrophic enrichment, while the sediment was anoxic. The two most common genera in the benthic foraminiferal assemblage, Ammonia and Elphidium, are typical of shallow water sandy substrates. This is the first reported comparison between SOD and benthic foraminiferal assemblages
High-Resolution Biostratigraphic Analysis of the Cretaceous/Paleogene Boundary in the Kurdistan Region (NW Iraq)
No full textChanges in the water column structure and paleoproductivity in the western South Atlantic Ocean during the mid-late Pleistocene: evidence from benthic and planktonic foraminifera
No full textBenthic foraminifers and geochemistry of sediments from the central Adriatic coast, Italy: a multi-proxy environmental study
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