Nd and Sr isotope compositions in modern and fossil bones - Proxies for vertebrate provenance and taphonomy

Rare earth elements (REE), while not essential for the physiologic functions of animals, are ingested and incorporated in ppb concentrations in bones and teeth. Nd isotope compositions of modern bones of animals from isotopically distinct habitats demonstrate that the (143)Nd/(144)Nd of the apatite can be used as a fingerprint for bedrock geology or ambient water mass. This potentially allows the provenance and migration of extant vertebrates to be traced, similar to the use of Sr isotopes. Although REE may be enriched by up to 5 orders of magnitude during diagenesis and recrystallization of bone apatite, in vivo (143)Nd/(144)Nd may be preserved in the inner cortex of fossil bones or enamel. However, tracking the provenance of ancient or extinct vertebrates is possible only for well-preserved archeological and paleontological skeletal remains with in vivo-like Nd contents at the ppb-level. Intra-bone and -tooth REE analysis can be used to screen for appropriate areas. Large intra-bone Nd concentration gradients of 10(1)-10(3) are often measured. Nd concentrations in the inner bone cortex increase over timescales of millions of years, while bone rims may be enriched over millenial timescales. Nevertheless, epsilon(Nd) values are often similar within one epsilon(Nd) unit within a single bone. Larger intra-bone differences in specimens may either reflect a partial preservation of in vivo values or changing epsilon(Nd) values of the diagenetic fluid during fossilization. However, most fossil specimens and the outer rims of bones will record taphonomic (143)Nd/(144)Nd incorporated post mortem during diagenesis. Unlike REE patterns, (143)Nd/(144)Nd are not biased by fractionation processes during REE-uptake into the apatite crystal lattice, hence the epsilon(Nd) value is an important tracer for taphonomy and reworking. Bones and teeth from autochthonous fossil assemblages have small variations of +/- 1 epsilon(Nd) unit only. In contrast, fossil bones and teeth from over 20 different marine and terrestrial fossil sites have a total range of epsilon(Nd) values from -13.0 to 4.9 (n = 80), often matching the composition of the embedding sediment. This implies that the surrounding sediment is the source of Nd in the fossil bones and that the specimens of this study seem not to have been reworked. Differences in epsilon(Nd) values between skeletal remains and embedding sediment may either indicate reworking of fossils and/or a REE-uptake from a diagenetic fluid with non-sediment derived epsilon(Nd) values. The latter often applies to fossil shark teeth, which may preserve paleo-seawater values. Complementary to epsilon(Nd) values, (87)Sr/(86)Sr can help to further constrain the fossil provenance and reworking. (C) 2011 Elsevier Ltd. All rights reserved.

Multiple processes regulate long-term population dynamics of sea urchins on Mediterranean rocky reefs

We annually monitored the abundance and size structure of herbivorous sea urchin populations (Paracentrotus lividus and Arbacia lixula) inside and outside a marine reserve in the Northwestern Mediterranean on two distinct habitats (boulders and vertical walls) over a period of 20 years, with the aim of analyzing changes at different temporal scales in relation to biotic and abiotic drivers. P. lividus exhibited significant variability in density over time on boulder bottoms but not on vertical walls, and temporal trends were not significantly different between the protection levels. Differences in densities were caused primarily by variance in recruitment, which was less pronounced inside the MPA and was correlated with adult density, indicating density-dependent recruitment under high predation pressure, as well as some positive feedback mechanisms that may facilitate higher urchin abundances despite higher predator abundance. Populations within the reserve were less variable in abundance and did not exhibit the hyper-abundances observed outside the reserve, suggesting that predation effects maybe more subtle than simply lowering the numbers of urchins in reserves. A. lixula densities were an order of magnitude lower than P. lividus densities and varied within sites and over time on boulder bottoms but did not differ between protection levels. In December 2008, an exceptionally violent storm reduced sea urchin densities drastically (by 50% to 80%) on boulder substrates, resulting in the lowest values observed over the entire study period, which remained at that level for at least two years (up to the present). Our results also showed great variability in the biological and physical processes acting at different temporal scales. This study highlights the need for appropriate temporal scales for studies to fully understand ecosystem functioning, the concepts of which are fundamental to successful conservation and management.

Aberrant features of the Messinian coral reefs, Spain

Se describen someramente los principales arrecifes del Messiniense en España, haciendo hincapié en el conjunto de 'anomalias' presentan los arrecifes del Neógeno inferior en comparación con las asociaciones arrecifales actuales. Se discute la importancia y significado de Porites sp. como coral claramente dominante, y a menudo exclusivo, en la construcción de edificios arrecifales.

Multiple processes regulate long-term population dynamics of sea urchins on Mediterranean rocky reefs

We annually monitored the abundance and size structure of herbivorous sea urchin populations (Paracentrotus lividus and Arbacia lixula) inside and outside a marine reserve in the Northwestern Mediterranean on two distinct habitats (boulders and vertical walls) over a period of 20 years, with the aim of analyzing changes at different temporal scales in relation to biotic and abiotic drivers. P. lividus exhibited significant variability in density over time on boulder bottoms but not on vertical walls, and temporal trends were not significantly different between the protection levels. Differences in densities were caused primarily by variance in recruitment, which was less pronounced inside the MPA and was correlated with adult density, indicating density-dependent recruitment under high predation pressure, as well as some positive feedback mechanisms that may facilitate higher urchin abundances despite higher predator abundance. Populations within the reserve were less variable in abundance and did not exhibit the hyper-abundances observed outside the reserve, suggesting that predation effects maybe more subtle than simply lowering the numbers of urchins in reserves. A. lixula densities were an order of magnitude lower than P. lividus densities and varied within sites and over time on boulder bottoms but did not differ between protection levels. In December 2008, an exceptionally violent storm reduced sea urchin densities drastically (by 50% to 80%) on boulder substrates, resulting in the lowest values observed over the entire study period, which remained at that level for at least two years (up to the present). Our results also showed great variability in the biological and physical processes acting at different temporal scales. This study highlights the need for appropriate temporal scales for studies to fully understand ecosystem functioning, the concepts of which are fundamental to successful conservation and management.

The fossil crown wasp Electrostephanus petiolatus Brues in Baltic Amber (Hymenoptera, Stephanidae): designation of a neotype, revised classification,and a key to amber Stephanidae.

The fossil crown wasp Electrostephanus petiolatus Brues comb. rev.(Stephanidae, Electrostephaninae) is re-described from a single male preserved in middle Eocene Baltic Amber. The holotype was lost or destroyed around the time of World War II and subsequent interpretations of its identity have been based solely on the brief descriptive comments provided by Brues in his original account. The new specimen matches the original description and illustration provided by Brues in every detail and we hereby consider them to be conspecific, selecting the specimen as a neotype for the purpose of stabilizing the nomenclature for this fossil species. This neotype exhibits a free first metasomal tergum and sternum, contrary to the assertion of previous workers who indicated these to be fused. Accordingly, this species does indeed belong to the genus Electrostephanus Brues rather than to Denaeostephanus Engel & Grimaldi (Stephaninae). Electrostephanus petiolatus is transferred to a new subgenus, Electrostephanodes n. subgen. , based on its elongate pseudo- petiole and slender gaster, but may eventually warrant generic status as the phylogenetic placement of these fossil lineages continues to be clarifi ed. A revised key to the Baltic amber crown wasps is provided.

Accessory phases as a tool to investigate magmatic underplating in polymetamorphic metasediments : an example from a fossil lower crust : Ivrea Verbano zne, NW Italy

The Ivrea and the Strona-Ceneri zones, NW italy and S Switzerland, offer the possibility to study the continental crust of the Southern Alps. Because of its high metamorphic degree and the abundant Permo- Carboniferous mafic intrusions, the Ivrea Zone is classically interpreted an exposed section trough the Permian lower crust. The present work is focused here on metasedimentary slices (septa) intercalated within Permian gabbro (mafic complex). In particular I studied the evolution of accessory phases such as rutile and zircon and the chemistry of the metasediments. The septa build an irregular and discontinuous band that cut obliquely the mafic complex from its deepest part (N) to its roof (S). The chemistry of the metasediments evolves along the band and the chemical evolution can be compared with that observed in the country-rock surrounding the mafic intrusion to the NE and overprinted by a main regional metamorphic event. This suggests that the degree of chemical depletion of the septa was mainly established during the same regional metamorphic event. Moreover it suggests that incorporation of the septa within the gabbro did not modify their original stratigraphie distribution within the crust. It implies that the mafic complex has been emplaced following a dynamic substantially different from the classic model of « gabbro glacier » (Quick et al., 1992; Quick et al., 1994). It is more likely that it has been emplaced by repeated injections of sills at different depths during a protracted period of time. Zircon trace elements and U-Pb ages suggest that regional metamorphism occurred 330-320Ma, the first sills in the deepest part of the Mafic Complex are injected at ~300Ma, the mafic magmas reached higher levels in the crust at 285Ma and the magmatic activity continued locally until 275Ma. The ages of detrital cores in zircons fix the maximal sedimentation age at ~370Ma, this age corresponds therefore with the maximal age of the incorporation of the Ivrea zone within the lower crust. I propose that the Ivrea zone has been accreted to the lower crust during the Hercynian orogeny sensu lato. The analysis of detrital ages suggests that the source terrains for the Ivrea zone and those for the Strona-Ceneri zone have a completely different Palaeozoic history. The systematic analysis of rutile in partially molten metasediments of the Ivrea zone reveals the occurrence of two generations. The two generations are characterized by a different chemistry and textural distribution. A first generation is formed during pro-grade metamorphism in the restitic counterpart. The second generation is formed in the melts during cooling at the same time that part of the first generation re-equilibrate. Re-equilibration of the first generation seems to be spatially controlled by the presence of fluids. Locally the second generation forms overgrowths on the first generation. Considered the different diffusivity of U and Pb in rutile, U heterogeneities have important implication for U-Pb dating of rutile. ID-TIMS and LA-ICPMS dating coupled with a careful textural investigation (SEM) suggest that rutile grains are characterized by multiple path along which Pb diffusion can occur: volume diffusion is an important process, but intragrain and subgrain boundaries provide additional high diffusivity pathways for Pb escape and reduce drastically the effective diffusion length. -- La zone d'Ivrea et la zone de Strona-Ceneri, en Italie nord-occidentale et Suisse méridionale, offrent la possibilité d'étudier la croûte continentale des Alpes du Sud. En raison du haut degré métamorphique et l'abondance d'intrusions mafiques d'âge Permo-Carbonifère [complexe mafique), la zone d'Ivrea est interprétée classiquement comme de la croûte inférieure permienne. Ce travail ce concentre sur des bandes metasédimentaires (septa) incorporées dans les magmas mafiques lors de l'intrusion. Les septa forment une bande irrégulière qui coupe obliquement le complexe mafique du bas (N) vers le haut (S). La chimie des septa évolue du bas vers le haut et l'évolution chimique se rapproche de l'évolution observé dans la roche encaissante l'intrusion affecté par un événement métamorphique régionale. Cette relation suggère que le degré d'appauvrissement chimique des septa a été établit principalement lors de l'événement métamorphique régional. De plus l'incorporation dans les gabbros n'a pas perturbée la distribution stratigraphique originelle des septa. Ces deux observations impliquent que le métamorphisme dans la roche encaissante précède la mise en place du gabbro et que cette dernière ne se fait pas selon le modèle classique (« gabbro glacier » de Quick et al., 1992, 1994), mais se fait plutôt par injections répétées de sills a différentes profondeurs. Les âges U-Pb et les éléments traces des zircons suggèrent que le métamorphisme régionale a eu lieu 330-320Ma, alors que les premiers sills dans la partie profonde du Mafic Complex s'injectent à ~300Ma, le magmatisme mafique atteigne des niveaux supérieurs à 285Ma et continue localement jusqu'à 270Ma. Les âges des coeurs détritiques des zircons permettent de fixer l'âge maximale de sédimentation à ~370Ma ce qui correspond donc à l'âge maximale de l'incorporation de la zone d'Ivrea dans la croûte inférieur. L'analyse systématique des rutiles, nous a permit de montrer l'existence de plusieurs générations qui ont une répartition texturale et une chimie différente. Une génération se forme lors de l'événement UHT dans les restites, une autre génération se forme dans les liquides lors du refroidissement, au même temps qu'une partie de la première génération se rééquilibre au niveau du Zr. Localement la deuxième génération peut former des surcroissances autour de la première génération. Dans ces cas, des fortes différences en uranium entre les deux générations ont des importantes implications pour la datation U-Pb sur rutile. Classiquement les ratios Pb/U dans le rutile sont interprétés comme indiquant l'âges du refroidissement du minéral sous une température à la quelle la diffusion du Pb dans le minéral n'est plus détectable et la diffusion à plus hautes températures est assumée se faire par «volume diffusion» dans le grain (Mezger et al., 1989). Par des datations ID-TIMS (sur grain entier) et LA-ICPMS (in-situ) et une analyse texturale (MEB) approfondie nous montrons que cette supposition est trop simpliste et que le rutile est repartie en sous-domaines. Chacun de ces domaines a ça propre longueur ou chemin de diffusion spécifique. Nous proposons donc une nouvelle approche plus cohérente pour l'interprétation des âges U-Pb sur rutile.

Fish colonization of artificial reefs in a large Neotropical reservoir: material type and successional changes

Artificial reefs have barely been used in Neotropical reservoirs (about five studies in three reservoirs), despite their potential as a fishery management tool to create new habitats and also to understand fish ecology. We experimentally assessed how reef material (ceramic, concrete, and PVC) and time modulated fish colonization of artificial reefs deployed in Itaipu Reservoir, a large reservoir of the mainstem Parana´ River, Brazil. Fish richness, abundance, and biomass were significantly greater in the reef treatments than at control sites. Among the experimental reefs, ceramic followed by the concrete treatments were the materials most effectively colonized, harboring the majority of the 13 fish species recorded. Although dependent on material type, many of the regularities of ecological successions were also observed in the artificial reefs, including decelerating increases in species richness, abundance, mean individual size, and species loss rates with time and decelerating decreases of species gain and turnover rates. Species composition also varied with material type and time, together with suites of life history traits: more equilibrium species (i.e., fishes of intermediate size that often exhibit parental care and produce fewer but larger offspring) of the Winemiller-Rose model of fish life histories prevailed in later successional stages. Overall, our study suggests that experimental reefs are a promising tool to understand ecological succession of fish assemblages, particularly in tropical ecosystems given their high species richness and low seasonality

The Genus Herposiphonia (Ceramiales, Rhodophyta) in the Coral Reefs Environmental Protection Area, Northeastern Brazil, with new records for Brazil and the Atlantic Ocean

This paper presents a taxonomic study of taxa of the red algae genus Herposiphonia (Ceramiales) occurring on Maracajaú Reef in the Coral Reefs Environmental Protection Area (CREPA - Área de Proteção Ambiental dos Recifes de Corais) in Rio Grande do Norte State, along the northeastern coast of Brazil. The CREPA comprises coastline and continental shelf areas of the municipalities of Touros, Rio do Fogo, and Maxaranguape and includes sand dunes, coastal lagoons, and the adjacent shoreline and offshore reefs. Detailed morphological studies were made, considering recent taxonomic criteria for species delimitation of Herposiphonia, and five species were identified: H. delicatula, H. nuda, H. parca, H. secunda, and H. tenella, thus increasing the number of species in the genus from three to six. Herposiphonia delicatula and H. parca represent new occurrences for Brazil, and H. nuda is reported for the first time for the Atlantic Ocean.

Temporal variation in the coral reefs of the east coast of the inner gulf of Thailand

A series of permanent line transects established on fourteen reefs on the eastern seaboard of the Gulf of Thailand were monitored through a three-year period (1995- 1998) using a video transect method. Hierarchical cluster analysis shows three distinctive reef community types dominated by 1) Porites, 2) Acropora and 3) zoantharians. The reefs are developed under naturally turbid conditions and relatively low salinity due to the proximity of four major river outlets located in the uppermost area of the gulf. The number of Acroporid species on the reefs is positively correlated with distance from the major flver outlets. Eighty-seven species of scleractinian coral were found on the transects. Over the three-year period, the comparison of 1995-97-98 matched stations using Repeated Measures ANOV A reveals no significant time-dependent change in percent area cover of reef components except for an overall significant reduction in the faviid coral component. In the 1997-98 matched station comparison, statistical tests reveal significant increases in both Acropora and Porites components that translated into an overall increase in total living coral cover. These findings indicate that the overall environmental conditions have been favorable for coral growth. Outcompetition of massive corals by faster growing corals on several reefs also indicates conditions favorable for reef expansion. Growth of newlyformed Porites colonies over primary rock substrate and dead coral skeleton was presumably responsible for its rapid increase. Although these reefs are in an area of rapid industrialization and population growth, resultant anthropogenic effects have not yet stopped active coral accretion.

Geological and fossil evidence.

La historia de la Tierra y de las diferentes formas de vida sobre ella se pueden conocer mediante el estudio de las rocas, los estratos, los fósiles y los restos animales y humanos conservados. Al final del libro hay una pequeña bibliografía y direcciones de páginas web.