68 research outputs found
Les isotopes du carbone dans les coquilles de gastéropodes terrestres de la série Loessique de Eustis (Nebraska, USA) : un indicateur de changements rapides de l'environnement entre 20 et 12 KA BP.
No full textLand snails build their shells with carbon extracted pnncipally from their diet and are a good record of the vegetation and climate vanations through time. We have analyzed the carbon isotopic composition of shells of Vertigo modesta sampled in the Eustis Upper Pleistocene loess senes, Nebraska, which deposited between 18, 000 and 12, 000 years. A trend towards andity of the environment is observed from the base to the top of the sequence. Rhythmic and rapid oscillations, of about 1 000 years, of the carbon isotopic composition indicate more humid penods. These results are compared to other indépendant proxies from the same or nearby loess sequences. The validation of the land snails shells as new record of paleochmatic variations in loess sequences is thus demonstrated.Les gastéropodes terrestres tirent principalement le carbone nécessaire à la constitution de leur coquille de leur alimentation, et constituent donc un possible enregistreur des conditions environnementales au cours du temps. Nous avons analysé les compositions isotopiques du carbone de coquilles de Vertigo modesta provenant de la série loessique de Eustis (Nebraska, USA), déposée entre 18 000 et 12 000 ans. Une tendance à l'aridification du milieu, de la base vers le sommet de la série, et une cyclicité d'environ 1000 ans dans l'occurrence de pénodes humides sont observées. Ces résultats sont corroborés par d'autres analyses provenant de la même séquence ou d'autres séries loessiques des grandes plaines américaines. La validation des gastéropodes terrestres en tant que nouvel indicateur paléoclimatique et de la végétation est ainsi démontrée.Labonne Maylis, Rousseau Denis Didier, Metref Slimane. Les isotopes du carbone dans les coquilles de gastéropodes terrestres de la série Loessique de Eustis (Nebraska, USA) : un indicateur de changements rapides de l'environnement entre 20 et 12 KA BP.. In: Quaternaire, vol. 13, n°3-4, 2002. Événements rapides, instabilités, changements culturels au Quaternaire. pp. 193-197
Utilisation géochimique des carbonates biogènes marins : exemples des colonies coralliennes, des coquilles de moules et des otolithes de poissons
No full textCet article présente, à partir d'études et de résultats concrets, les principaux intérêts des analyses isotopiques qu'il est possible de mener sur des archives carbonatées marines. Les mesures des isotopes du plomb et de l'oxygène effectuées par exemple sur des colonies récifales, des coquilles de moules et des pièces calcifiées de l'oreille interne de poissons téléostéens, permettent ainsi d'accéder à une meilleure compréhension des perturbations environnementales
Utilisation géochimique des carbonates biogènes marins : exemples des colonies coralliennes, des coquilles de moules et des otolithes de poissons
No full textCet article présente, à partir d'études et de résultats concrets, les principaux intérêts des analyses isotopiques qu'il est possible de mener sur des archives carbonatées marines. Les mesures des isotopes du plomb et de l'oxygène effectuées par exemple sur des colonies récifales, des coquilles de moules et des pièces calcifiées de l'oreille interne de poissons téléostéens, permettent ainsi d'accéder à une meilleure compréhension des perturbations environnementales
Geochemical gradients within modern and fossil shells of Concholepas concholepas from northern Chile: an insight into U–Th systematics and diagenetic/authigenic isotopic imprints in mollusk shells
No full textExploring fidelity of Sardines (Sardina pilchardus) to feeding grounds in the Atlantic Moroccan waters using stable isotope analyses (C, N) and otolith microchemistry
No full textThe Atlantic Moroccan waters (21°-29°N) are part of the Canary Current Large Marine Ecosystem and are enriched by highly productive upwelling systems. Sardine (Sardina pilchardus) is both the most abundant forage fish in this area and the most heavely fish species [1]. It is described as a migratory small pelagic species that feeds on phyto and zooplankton. From population genetics studies (allozyme and micostellite DNA), it is assumed that our area of interest houses a single population [2] with at least two spawning areas [3].
In order to study trophic position and fidelity to feeding grounds, we investigated sardines from two distant sites: 23-24°N and 28-29°N, using stable isotope analysis (d15N and d13C) and otolith microchemistry. Isotopic analyses were performed on delipidated muscle subsamples, and plankton samples (150µm mesh net), using a continuous flow isotope-ratio mass spectrometry. The trophic position of sardine is compared to those of major forage fish of the same area. Otholith microelements concentrations (Li, B, Mg, Mn, Zn, Sr, Ba, Pb and U) were measured by ICP-MS laser on transects from nucleus to the edge of the otoliths of sardines. Chemical analyses were carried out on five individuals per site.
Sardine individuals from the different sites showed significantly different trophic position for both C and N isotopes. The northern individuals were depleted in d15N (1‰ difference), suggesting that phytoplankton is more important in their diet. The d13C values showed greater differences (~3‰) for both Sardines and zooplankton between the two sites, pointing high fidelity for sardine individuals towards the feeding grounds. While Anchovy and Horse Mackerel showed a similar pattern with sardine for δ13C, chub mackerel showed no significant differences between the two areas suggesting a higher seasonal migratory behavior for this species. Sardine Microelements profiles reinforced the sedentary behavior hypothesis for sardine. The Barium (Ba) profiles were the most discriminant: the concentration range was 7× higher for the southern area where upwelling intensity is higher [4]
Na szczycie wulkanu. O wyprawach na Heklę i Snæfellsjökull w XVIII i XIX wieku
No full textThe present paper gives an overview of the history of climbing on Hekla and Snæfellsjökull, Iceland’s most famous volcanoes, in the 18th and 19th centuries. In the Middle Ages and early modern period, Hekla was compared to the gates of hell due to its frequent and violent eruptions. Snæfellsjökull was considered a supernatural space and a domain of Bárður, the eponymous hero of Bárðar saga Snæfellsáss. The author analyses a wide range of sources: Reise igiennem Island by Bjarni Pálsson and Eggert Ólafsson (who reached the summits of Hekla and Snæfellsjökull in 1750 and 1754, respectively), British (from Banks to Burton) and French (from Gaimard to Labonne) travelogues, Ida Pfeiffer’s journals (who was the first foreign woman to climb Hekla).The present paper gives an overview of the history of climbing on Hekla and Snæfellsjökull, Iceland’s most famous volcanoes, in the 18th and 19th centuries. In the Middle Ages and early modern period, Hekla was compared to the gates of hell due to its frequent and violent eruptions. Snæfellsjökull was considered a supernatural space and a domain of Bárður, the eponymous hero of Bárðar saga Snæfellsáss. The author analyses a wide range of sources: Reise igiennem Island by Bjarni Pálsson and Eggert Ólafsson (who reached the summits of Hekla and Snæfellsjökull in 1750 and 1754, respectively), British (from Banks to Burton) and French (from Gaimard to Labonne) travelogues, Ida Pfeiffer’s journals (who was the first foreign woman to climb Hekla)
Otolith chemical signature and growth of Chaetodon speculum in coastal areas of New Caledonia
No full textCoral reefs are one of the most diverse ecosystems on Earth. They are currently exposed to increasing levels of anthropogenic perturbations. Several recent reviews point to the lack of good indicators for these perturbations especially to monitor their effects on fish populations or fish assemblages. The SW lagoon of New Caledonia is an ideal location to test indicator species in this context as contrasting sites are present within a small geographical range. This study analysed fish from four sites, one with heavy industrial pollution, another dominated by domestic waste, a third with historic mining activities, and the fourth as a control. The butterfly fish, Chaetodon speculum, was chosen to determine C. speculum's potential as an indicator species due to its link to coral, its sedentary behaviour and its wide geographical distribution. The size distribution, growth rate, age distribution and whole otolith composition were analysed at each site. Age and mean growth rate were analysed from daily increments of the otoliths. The concentrations of eight elements (Li, Mg, Co, Ni, Cu, Rb, Sr, and Ba) were measured by ICP-MS in the otoliths of a subset of individuals. The sites under anthropogenic impact were distinct from the control site by fish size frequencies, age distributions, and the chemical content of their otoliths. The chemical elements Mg, Co, Ni, Cu, and Rb showed differences amongst sites. Fish belonging to the sites furthest from Noumea could be discriminated in nearly 80% of samples or 60% of the cases when otolith weight or fish age respectively were taken into account. Ni concentrations of the otoliths were also higher in the bays where water concentrations of this element were known to be higher, but these differences were no longer significant once corrected for otolith weight. These results should be mitigated by the fact that: (1) despite significant differences between sites in age distribution and size frequencies there were no differences in growth rates or body condition; (2) differences in age or size were not correlated to perturbation levels; and (3) discrimination between sites based on chemical levels in the otoliths, even though significant, was not sufficient to identify the origin of the fish at a level useful for screening tests. The hypothesis that environmental differences between sites would be reflected in the otolith chemical composition is therefore not fully supported by our results
Major population’s separation area for sardine (Sardina pilchardus) and hake (Merluccius merluccius) revealed using otolith geochemistry on the Atlantic coast of Morocco
No full textInternational audienc
Pb isotopes in mussels as tracers of metal sources and water movements in a lagoon (Thau Basin, S. France)
No full textIdentification isotopique des apports métalliques dans un port par l'analyse de moules (Sète, Hérault)
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