Validation of daily increment deposition in the otoliths of spot (Leiostomus xanthurus)

The otoliths of 200 postlarval spot (Leiostomus xanthurus) were marked by immersing the fish for 24 hr in a solution of 0.4 g tetracycline HCl l^?1 of salt water (15 ‰). The resulting time-mark could later be identified under ultraviolet (UV) light with an epifluorescence microscope. Spot were held in the laboratory or in the field for up to 30 d. Two validation methods were employed to document daily increment formation. The total number of increments per otolith, or the number of increments formed after the time-mark, were regressed against days held in an experiment. The hypothesis of one increment per day would result in a regression coefficient not significantly different from 1.0. In the field both the total count method (b=1.05) and the time-mark method (b=0.90) supported a one-increment-per-day hypothesis and were not significantly different from each other (p>0.05). In the laboratory the total count method (b=0.56) and the time-mark method (b=0.36) were significantly different from 1.0 (p<0.05), and thus did not support the one-increment-per-day hypothesis. Failure to resolve a one-increment-per-day deposition rate in the laboratory was primarily attributed to food limitation in the experiments.     

Experimental and texture-derived P-wave anisotropy of principal rocks from the TRANSALP traverse: An aid for the interpretation of seismic field data

A representative suite of deformed, metamorphic rocks from the TRANSALP reflection seismic traverse in the Eastern Alps was studied in the laboratory with respect to elastic properties and whole-rock texture. Compressional wave (P-wave) velocities and their anisotropies were measured at various experimental conditions (dry, wet, confining pressure), and compared to the texture-related component of anisotropy. Here ‘texture’ refers to crystallographic preferred orientations (CPOs), which were determined by neutron texture goniometry. In gneisses and schists P-wave anisotropies are mainly controlled by the microcrack fabric. In marbles and amphibolites CPO contributes very significantly to anisotropy. At 200 MPa confining pressure the degree of anisotropy is between 5% and 15%, depending on rock composition and/or CPO intensity. Special emphasis was also put on discussing possible effects of fluids on seismic velocity and anisotropy. Distributions of water-filled microcracks and pores are distinctly anisotropic, with maximum contribution to bulk rock velocity mostly parallel to the foliation pole. Decreasing P-wave velocity and increasing anisotropy of immersed samples may be explained by crack-induced changes of the elastic moduli of bulk rock. The main conclusion regarding interpretation of TRANSALP data is that strong reflections in the deep Alpine crust are probably due to marble–gneiss and metabasite–gneiss contacts, although P-wave anisotropy and boundaries between zones of ‘dry’ or ‘wet’ series may contribute to reflectivity to some extent.     

Late Paleozoic deformation and exhumation in the Sierras Pampeanas (Argentina): 40Ar/39Ar-feldspar dating constraints

International Journal of Earth Sciences - Systematic 40Ar/39Ar feldspar data obtained from the Sierras Pampeanas are presented, filling the gap between available high-...     

Unsuitability of TAC management within an ecosystem approach to fisheries: An ecological perspective

Fisheries management in European waters is gradually moving from a single-species perspective towards a more holistic ecosystem approach to management (EAM), acknowledging the need to take all ecosystem components into account. Prerequisite within an EAM is the need for management processes that directly influence the ecological effects of fishing, such as the mortality of target and non-target species. Up until recently, placing limits on the quantities of fish that can be landed, through the imposition of annual total allowable catches (TACs) for the target species, has been the principal management mechanism employed. However, pressure on non-target components of marine ecosystems is more closely linked to prevailing levels of fishing activity, so only if TACs are closely related to subsequent fishing effort will TAC management serve to control the broader ecosystem impacts of fishing. We show that in the mixed fisheries that characterise the North Sea, the linkage between variation in TAC and the resulting fishing effort is in fact generally weak. Reliance solely on TACs to regulate fishing activity is therefore unlikely to mitigate the impacts of fishing on non-target species. Consequently, we conclude that the relationship between TACs and effort is insufficient for TACs to be used as the principal management tool within an EAM. The implications, and some alternatives, for fisheries management are discussed.     

Damage phenomenon and petrophysical properties of sandstones at the Phnom Bakheng Temple (Angkor,Cambodia): first investigations and possible conservation measures

Sandstones, clay in the form of bricks and laterite are the building materials used by the Khmer to construct the imposing and magnificent temples in Southeast Asia. Many of these monuments suffer from fracturing, sanding, contour scaling, crust formation and salt weathering. The affinity to weathering is closely connected to the type of material. Two sandstone types classified as feldspathic arenite and quartz arenite of Angkor as well as two arkosic sandstones from Thailand are described and investigated in this study. Important petrophysical properties determined for the different sandstones consist of hydric expansion, thermal expansion, pore radii distribution and ultrasonic velocity. Different investigations such as capillary water uptake, surface hardness, hygroscopic water sorption, and salt resistance tests were undertaken in the laboratory to characterize the various rock types. Observations and quantified damage mapping were done onsite at the Phnom Bakheng Temple. Contour scaling in the form of weathering crusts is one of the main deterioration features observable at the Angkor monuments. Comparisons are made between the building stone, the crust material from the Phnom Bakheng Temple and fresh stone material used for restoration. Significant differences in hydric and especially in thermal expansion of the crust and sandstone have been determined. The results seem to indicate that extensional processes occur, which can be considered a force for detachment (i.e., contour scaling, flaking). In an experimental trial, the hydric and thermal expansion of the weathering crust and the building stone was significantly reduced by using a weak acid for the crust and a swelling inhibitor for the original building stone.     

An assessment of the ENSO forecast skill of GEOS-5 system

The seasonal forecast skill of the NASA Global Modeling and Assimilation Office atmosphere–ocean coupled global climate model (AOGCM) is evaluated based on an ensemble of 9-month lead forecasts for the period 1993 to 2010. The results from the current version (V2) of the AOGCM consisting of the GEOS-5 AGCM coupled to the MOM4 ocean model are compared with those from an earlier version (V1) in which the AGCM (the NSIPP model) was coupled to the Poseidon Ocean Model. It was found that the correlation skill of the Sea Surface Temperature (SST) forecasts is generally better in V2, especially over the sub-tropical and tropical central and eastern Pacific, Atlantic, and Indian Ocean. Furthermore, the improvement in skill in V2 mainly comes from better forecasts of the developing phase of ENSO from boreal spring to summer. The skill of ENSO forecasts initiated during the boreal winter season, however, shows no improvement in terms of correlation skill, and is in fact slightly worse in terms of root mean square error (RMSE). The degradation of skill is found to be due to an excessive ENSO amplitude. For V1, the ENSO amplitude is too strong in forecasts starting in boreal spring and summer, which causes large RMSE in the forecast. For V2, the ENSO amplitude is slightly stronger than that in observations and V1 for forecasts starting in boreal winter season. An analysis of the terms in the SST tendency equation, shows that this is mainly due to an excessive zonal advective feedback. In addition, V2 forecasts that are initiated during boreal winter season, exhibit a slower phase transition of El Nino, which is consistent with larger amplitude of ENSO after the ENSO peak season. It is found that this is due to weak discharge of equatorial Warm Water Volume (WWV). In both observations and V1, the discharge of equatorial WWV leads the equatorial geostrophic easterly current so as to damp the El Nino starting in January. This process is delayed by about 2 months in V2 due to the slower phase transition of the equatorial zonal current from westerly to easterly.     

Temporal variability of three different macrofauna communities in the northern North Sea

In 1999, 2003 and 2007 macrofauna communities were sampled in three different areas (“Boxes”) of 10 × 10 nautical miles in the northern North Sea in order to study the temporal changes in community structure in relation to changes in temperature or changes in hydrography.     

The R��o de la Plata Craton: a review of units, boundaries, ages and isotopic signature

A review of the lithostratigraphic units in the Río de la Plata Craton and of new and previously published geochronological, isotopic and geophysical data is presented. Sm?CNd T_DM model ages between 2.6 and 2.2?Ga characterize the Piedra Alta Terrane of this craton. Crystallization ages between 2.2 and 2.1?Ga for the metamorphic protoliths and 2.1?C2.0?Ga for the post-orogenic granitoids indicate juvenile crust, followed by a short period of crustal recycling. Cratonization of this terrane occurred during the late Paleoproterozoic. Younger overprinting is not observed, suggesting it had a thick and strong lithosphere in the Neoproterozoic. A similar scenario is indicated for the Tandilia Belt of Argentina. Sm?CNd T_DM model ages for the Nico Pérez Terrane show two main events of crustal growth (3.0?C2.6?and 2.3?C1.6?Ga). The crystallization ages on zircon ranges between 3.1 and 0.57?Ga, which is evidence for long-lived crustal reworking. The age for cratonization is still uncertain. In the Taquarembó Block, which is considered the prolongation of the Nico Pérez Terrane in southern Brazil, a similar scenario can be observed. These differences together with contrasting geophysical signatures support the redefinition of the Río de la Plata Craton comprising only the Piedra Alta Terrane and the Tandilia Belt. The Sarandí del Yí Shear Zone is regarded as the eastern margin of this Craton.     

Geodynamic evolution of the Eastern Sierras Pampeanas (Central Argentina) based on geochemical, Sm–Nd, Pb–Pb and SHRIMP data

Whole-rock geochemical analyses using major and trace elements in combination with the Sm–Nd and Pb–Pb isotope systems, together with SHRIMP age dating on metasedimentary rocks from the Sierras de Chepes, the Sierras de Córdoba, the Sierra Norte and the San Luis Formation in the Sierra de San Luis, have been carried out to unravel the provenance and the geodynamic history of the Eastern Sierras Pampeanas, Central Argentina. The geochemical and the Sm–Nd data point to a slightly stronger mafic and less-fractionated material in the provenance area of the Sierras de Córdoba when compared to the other units. The T_DM model ages from the Sierras de Chepes (~1.82 Ga) and the Sierra Norte (~1.79 Ga) are significantly older than the data from the Sierras de Córdoba (1.67 Ga). The Pb data are homogeneous for the different units. Only the ²⁰⁸Pb/²⁰⁴Pb ratios of some samples from the Sierras de Córdoba are higher. A late Pampean detrital zircon peak around 520 Ma from the Sierras de Chepes is in accordance with the new data from the San Luis Formation. This is similar to the literature data from the Famatina Belt located to the northwest of the Sierras de Chepes and also fits the detrital zircon peaks in the Mesón group. These maximum depositional ages were also reported from some locations in the Puncoviscana Formation but are absent in the Sierras de Córdoba. An improved model for the development of the Eastern Sierras Pampeanas in the area between the Sierras de Córdoba and the Puncoviscana Formation is provided. This gives new insights into the late Pampean development of the Sierra de San Luis and the complex development of the Eastern Sierras Pampeanas. This new model explains the younger detrital ages in the Puncoviscana Formation compared with the older ages of the Sierras de Córdoba. Another model of the Sierra de San Luis explains the younger depositional ages of the Pringles Metamorphic Complex and the San Luis Formation when compared to the Nogolí Metamorphic Complex and the Conlara Metamorphic Complex. Additionally, the rather fast change of the high-grade metamorphic conditions in the Pringles Metamorphic Complex and the low-grade metamorphic conditions in the San Luis Formation is explained by extension, the ascent of (ultra) mafic material and later folding and erosion.