Exploring aberrant bivalve shell ultrastructure and geochemistry as proxies for past sea water acidification

Throughout much of Earth's history, marine carbonates have represented one of the most important geological archives of environmental change. Several pivotal events during the Phanerozoic, such as mass extinctions or hyperthermal events have recently been associated with ocean acidification. Nevertheless, well‐defined geological proxies for past ocean acidification events are, at best, scarce. Here, experimental work explores the response of bivalve shell ultrastructure and isotope geochemistry (δ¹³C, δ¹⁸O and δ²⁶Mg) to stressful environments, in particular to sea water acidification. In this study, the common blue mussel, Mytilus edulis, was cultured (from early juvenile stages to one year of age) at four pH regimes (pH_NBS 7·2 to pH 8·0). Shell growth rate and ultrastructure of mainly the calcitic portion of the shells were compared between experimental treatments. Specimens exposed to low‐pH environments show patches of disordered calcitic fibre orientation in otherwise well‐structured shells. Furthermore, the electron backscattered diffraction analyses reveal that, under acidified conditions, the c‐axis of the calcite prisms exhibits a bimodal or multi‐modal distribution pattern. Similar shell disorder patterns have been reported from mytilids kept under naturally acidified sea water conditions. In contrast, this study found no evidence that different pH regimes affect shell carbon, oxygen or magnesium isotope ratios. Based on these observations, it is proposed that: (i) stressful environments, in this case low sea water pH, predictably affect bivalve biomineralization patterns; and (ii) these findings bear potential as a novel (petrographic) proxy for ancient sea water acidification. An assessment of the applicability of these data to well‐preserved fossil shell material from selected time intervals requires additional work.     

Climate change perception in Romania

Theoretical and Applied Climatology - In the last decades, anthropogenic drivers have significantly influenced the natural climate variability of Earth’s atmosphere. Climate change has become...     

The effects of surface weathering on the geochemical analysis of archaeological lithic samples using non‐destructive polarized energy dispersive XRF

The purpose of this paper is to show the effects of lithic artifact surface weathering on whole rock non‐destructive polarized energy dispersive X‐ray fluorescence (P‐ED‐XRF) major and trace element determinations. Chemical results for a weathered and subsequently mechanically ground subset of New Hampshire Ossipee archaeological flakes, cataloged as hornfels, show that both groups of elements are variably affected by weathering. A graphic approach is developed and proposed to highlight the role and importance of immobile elements. A case is made and an analytical method is proposed for the routine use of P‐ED‐XRF spectrometers to determine the chemical makeup of lithic artifacts and therefore provide a data set compatible with existing geochemical databases and literature. The use of specific variation diagrams is adopted to portray the weathering trend. Internationally approved geochemical rock type diagrams are used to correct the rock type previously assigned to Ossipee artifacts and in turn narrow down potential quarry sources. © 2011 Wiley Periodicals, Inc.     

A Mariner/MESSENGER global catalog of mercurian craters

Using MESSENGER and Mariner 10 flyby images, we have compiled a global catalog of impact structures with diameters D > 10 km. The distribution of impact structures shows a factor of 10 range in areal crater density. Most regions of low crater density are located within large impact basins, consistent with the idea that these were low-lying areas that have been filled by subsequent volcanism over an extended period.     

Cassini VIMS observations of latitudinal and hemispheric variations in Saturn’s infrared auroral intensity

The intensity of Saturn’s infrared aurora is investigated using Cassini VIMS images acquired during October 2006–February 2009. Polar and main oval auroral regions were defined in both hemispheres, which extend between 0–10° and 10–25° co-latitude, respectively. Average intensities were computed for these regions and compared. While the northern and southern main oval regions covered a similar range of intensities, the southern main oval was on average more intense by a factor of ∼1.3. The emission from the southern polar region was usually less intense than the main oval emissions, while this was only the case for approximately half of the northern hemisphere images. The northern hemisphere polar region displayed intensities more than twice as high as those in the south and the difference between the two hemispheres was most pronounced on the dayside. In general, more intense polar emissions were accompanied by more intense main oval emissions. Possible explanations for the hemispheric and latitudinal differences are discussed in terms of particle energies and fluxes, ionospheric conductivity, temperature and magnetic field strength.     

Delineation of compaction criteria for acceptable hydraulic conductivity of lateritic soil-bentonite mixtures designed as landfill liners

In current geoenvironmental practice, design engineers usually require that soil liners in waste landfills be compacted within a specified range of water content and dry unit weight. This specification is based primarily on the need to achieve a minimum dry unit weight for factors controlling the performance of compacted soil liners most especially the hydraulic conductivity, k. In this study, lateritic soil treated with up to 10% bentonite, prepared at various compaction states (dry of optimum, optimum and wet of optimum moisture content) was compacted with four compactive efforts (i.e., the reduced British Standard Light, British Standard Light, West African Standard, and British Standard Heavy) to simulate the range of compaction energies expected in the field. Prepared soil mixtures were permeated with water and specimens that yielded the permissible limit of k????1?×?10^?9?m/s were enclosed in an envelope (known as the acceptable zone) on the water content?Cdry unit weight curve. It was observed that compaction conditions resulting in moisture content slightly wet of optimum led to the lowest values of k and that the shapes and boundaries of the acceptable zones gradually increased in extent, shifting to wet side of optimum moisture content as the bentonite content increased to 10%. This approach provides good control over the quality of compacted soils and has great potential for field application.     

Key barriers to community cohesion: views from residents of 20 London deprived neighbourhoods

The notion of community has been central to the political project of renewal of New Labour in the UK. The paper explores how the discourses of community are framed within New Labour and discusses these in the light of the results from research which focuses on how people within urban deprived areas construct their community. It draws upon the results of one part of a larger research project (the ‘Well London’ programme) which aimed to capture the views of residents from 20 disadvantaged neighbourhoods throughout London using an innovative qualitative method known as the ‘World Café’. Our results show the centrality of young people to the development of cohesive communities, the importance of building informal relationships between residents alongside encouraging greater participation to policy making, and the need to see these places as fragile and temporary locations but with considerable social strengths. Government policies are only partially addressing these issues. They pay greater attention to formally encouraging citizens to become more involved in policy making, largely ignore the contribution young people could make to the community cohesion agenda, and weakly define the shared norms and values that are crucial in building cohesive communities. Thus, the conclusion is that whilst an emphasis of the government on ‘community’ is to be welcome, more needs to be done in terms of considering the ‘voices’ of the community as well as enabling communities to determine and act upon their priorities.     

First record of the puzosiine ammonite genus Pachydesmoceras from the Middle and Upper Turonian of Poland

Two gigantic individuals of the puzosiine ammonite genus Pachydesmoceras, from uppermost Middle and lower Upper Turonian strata in central and southwest Poland, are described and illustrated as the first examples of this genus to be recorded from Poland. Specific identification is problematic because of internal mould preservation and deformation to various extent; in addition, comparative material from other European localities is lacking. Representatives of Pachydesmoceras are typical of the Tethyan Realm; records from the European and Northwest Pacific provinces in the Boreal Realm are few. Both Polish specimens are referred to as P. cf. pachydiscoide Matsumoto.     

Vulnerability indicators of sea water intrusion

In this paper, simple indicators of the propensity for sea water intrusion (SWI) to occur (referred to as "SWI vulnerability indicators") are devised. The analysis is based on an existing analytical solution for the steady-state position of a sharp fresh water-salt water interface. Interface characteristics, that is, the wedge toe location and sea water volume, are used in quantifying SWI in both confined and unconfined aquifers. Rates-of-change (partial derivatives of the analytical solution) in the wedge toe or sea water volume are used to quantify the aquifer vulnerability to various stress situations, including (1) sea-level rise; (2) change in recharge (e.g., due to climate change); and (3) change in seaward discharge. A selection of coastal aquifer cases is used to apply the SWI vulnerability indicators, and the proposed methodology produces interpretations of SWI vulnerability that are broadly consistent with more comprehensive investigations. Several inferences regarding SWI vulnerability arise from the analysis, including: (1) sea-level rise impacts are more extensive in aquifers with head-controlled rather than flux-controlled inland boundaries, whereas the opposite is true for recharge change impacts; (2) sea-level rise does not induce SWI in constant-discharge confined aquifers; (3) SWI vulnerability varies depending on the causal factor, and therefore vulnerability composites are needed that differentiate vulnerability to such threats as sea-level rise, climate change, and changes in seaward groundwater discharge. We contend that the approach is an improvement over existing methods for characterizing SWI vulnerability, because the method has theoretical underpinnings and yet calculations are simple, although the coastal aquifer conceptualization is highly idealized.     

Colour variation in the southern rock lobster Jasus edwardsii and its economic impact on the commercial industry

Southern rock lobster Jasus edwardsii varies in shell coloration throughout southern Australia. Predominantly exported as a live product to Asian markets, price is influenced by colour with prices higher for dark red than paler coloured lobsters, which are discounted. This paper explores spatial and depth variation in shell colour for the Tasmanian, South Australian and Victorian fisheries using catch sampling data. The proportion of red lobsters decreased with depth and was prevalent at depths less than 30 m, whereas paler coloured lobsters dominated the deeper depth ranges. The depth of transition where 50% of lobsters were classified as red showed a weak trend of increase with latitude from southern Tasmania to northern South Australia. Under quota management, lobster colour was a significant driver of fleet dynamics as fishers target areas of high price per unit. Consequently, catches of pale lobsters from greater depths remain low despite the high catch rates in these areas. The colour price differential varies seasonally (higher in summer) so fishers increase supply of pale lobsters during winter. Discounting on colour equates to AUS$6.67 million/year for the Tasmanian Fishery alone, which indicates value from management or marketina research to reduce discountina.