Colluvial sedimentation in a hyperarid setting (Atacama Desert,northern Chile): Geomorphic controls and stratigraphic facies variability

Research on colluvial depositional systems has recently emphasized periglacial and high‐altitude settings, and the relations between Quaternary slope stratigraphy and climate change. This article examines the role of variable slope morphology, surface hydrology and microclimate in controlling colluvial sedimentation along a coastal tract of the hyperarid Atacama Desert in northern Chile. Direct accessibility of active surfaces is accompanied by uninterrupted stratigraphic exposures along the base of slopes, allowing direct comparisons between surface processes and the resulting sedimentary record. Four slope sectors are identified, based on differences in morphology and processes over active surfaces. Colluvial sedimentation is controlled by complex interactions of slope gradients and profiles, exposure to dominant winds, and potential runoff pathways, which vary considerably between different sectors. Major differences are evident between these hyperarid deposits and slope sedimentation in periglacial and temperate settings, including the complete absence of pedogenic activity and clay minerals; the volume of aeolian deposits and their role in controlling processes which redistribute sediment downslope, extending colluvial aprons; and the occurrence of runoff processes only where favoured by particular topographic configurations. Depositional surfaces range from steep talus cones, to debris‐flow‐dominated and aeolian‐dominated colluvial aprons, to an aeolian ramp subject to reworking by mass flows and flash floods. Consequently, facies associations and architectures at outcrop are highly variable and highlight the importance of spatial variations in slope morphology and processes in producing distinct, coeval colluvial stratigraphies within a single environmental context. Discrepancies between active processes and the corresponding stratigraphic signatures are also evident in some sectors; for example, preservation of alluvial and aeolian facies in stratigraphic sections does not always reflect the dominant processes over active slopes. Together with the spatial variability in processes and deposits along these slopes, this suggests that caution is required when extracting palaeoenvironmental information from analyses of colluvial successions.     

Empirical assessment of adaptation to climate change impacts of mountain households: development and application of an Adaptation Capability Index

The present study proposes an index to assess the potential for adaptation to climate change for households in the mountainous regions. The index provides a realistic approach to recognize social and natural factors which contribute to successful adaptation and addresses several household functions, such as social networking, livelihood strategy, adjustment strategies, resource availability and accessibility. The proposed Adaptation Capability Index (ACI) is analytically defined, mathematically formulated and field tested on mountainous households in urban and semi-urban regions of the Uttarakhand Himalaya in India. To gather data on the topic relevant to the ACI, a household scale questionnaire was developed and administered to 120 heads of households through face-to-face interviews. The results highlight higher adaptive capability of urban households and low adaptation capacity of rural households due to poor farm productivity, low accessibility and availability of resources and technological input. Future programs and policies must include and implement regulations to remedy attributive factors responsible for higher adaptation. This paper may be applicable to other mountainous regions and may provide insights for effective adaptation strategies to climate change.     

An Innovative Approach to Meteorite Analysis by Laser‐Induced Breakdown Spectroscopy

An innovative approach of double pulse laser‐induced breakdown spectroscopy (DP‐LIBS) coupled with optical microscopy was applied to the characterisation and quantitative analysis of the Agoudal iron meteorite in bulk sample and in petrographic thin section. Qualitative analysis identified the elements Ca, Co, Fe, Ga, Li and Ni in the thin section and the whole meteorite. Two different methods, calibration‐free LIBS and one‐point calibration LIBS, were used as complementary methodologies for quantitative LIBS analysis. The elemental composition data obtained by LIBS were in good agreement with the compositional analyses obtained by traditional methods generally applied for the analysis of meteorites, such as ICP‐MS and EDS‐SEM. Besides the recognised advantages of LIBS over traditional techniques, including versatility, minimal destructivity, lack of waste production, low operating costs, rapidity of analysis, availability of transportable or portable systems, etc., additional advantages of this technique in the analysis of meteorites are precision and accuracy, sensitivity to low atomic number elements such as Li and the capacity to detect and quantify Co contents that cannot be obtained by EDS‐SEM.     

Identification of the multidrug resistance-associated protein (mrp) related gene in red mullet (Mullus barbatus)

Multixenobiotic resistance mechanism (MXR) in aquatic organisms is mediated by the activity of the P-glycoprotein (Pgp) transporter that binds and actively effluxes different chemicals out of cell. In addition to the Pgp, several other, non-Pgp transport proteins have been recently identified in different human and animal tissues. Given their characteristics and tissue distribution we hypothesized that members of the so-called multidrug resistance-associated protein (MRP) family may be expressed in aquatic organisms. This study attempted to identify MRP related genes in different tissues of several marine and freshwater bivalves (Mytilus galloprovincialis, Dreissena polymorpha, Anodonta cygnea) and fish species (Mullus barbatus, Cyprinus carpio, Salmo trutta). Following an alignment of known MRP1 and MRP2 human sequences, as well as the GenBank available mrp2 sequences from different animals, we determined highly conserved regions and used them to design three pairs of consensus primers. Total RNA was isolated, reverse transcribed to cDNA and the obtained cDNAs were PCR amplified with the corresponding primers. The amplified PCR products were sequenced and their homology compared with Pgp and MRP protein sequences from different species. The expression of MRP related mRNA was clearly identified only in liver tissue isolated from red mullet, with homologies at the protein level ranging from 75% to 76%. Described results clearly pointed at the possibility that at least in the red mullet MXR as a general defense mechanism may be mediated by the activities of at least two different types of transport proteins.     

Foraminiferal distribution in one bed,Monterey Formation,California

All 146,039 foraminifera obtained from twenty-four 5-ml replicate samples taken 10-cm apart along one 8-cm thick bed in the Monterey Formation were identified and counted. Replicates 1 through 19 and 20 through 24 differ taxonomically and, very significantly, numerically. Differences probably reflect postmortem transport, small-scale ecological variations, and possibly other phenomena. Such foraminiferal distributions can assist both the determination of sampling adequacy and sedimentation processes themselves.     

Potential Use of Biomarkers in Zooplankton as Early Warning Signals of Ecotoxicological Risk in the Marine Food Chain

Abstract. Zooplankton is an essential component of the marine and brackish food chains. The ecotoxicological risk of zooplanktonic communities, estimated by the modern methodological approach of biomarkers, can be used as an early warning signal of ecosystem health. The aim of this project is to estimate the potential use of several biomarkers (esterases, mixed function oxidases, porphyrins) in zooplanktonic organisms. Studies were carried out with different zooplanktonic crustaceans: the copepods Acartia margalefi and Acartia latisetosa collected in Ganzirri Lake (Messina); the mysid Siriella clausi collected in Faro Lake (Messina); the mysids Diamysis bahirensis, Siriella armata and Mysidopsis gibbosa collected in Stagnone di Marsala (Palermo); the Antarctic euphausiids Euphausia crystallorophias and Euphausia superba; the am-phipod Streetsia challengeri and the euphausiid Meganycthiphanes norvegica collected after a shore-stranding along Messina's Ionian coast. Moreover, experiments were carried out with the benthic decapods Eriphia verrucosa and Pachygrapsus marmoratus from a rocky shore of Messina's Ionian coast. Acetylcholinesterase activity (AChE) was determined in homogenates of whole organisms. The key result of this project concerns the different AChE activity basal values of different crustacean species. Particular attention should be paid to the difference in basal activity found between the Antarctic and the Mediterranean species.     

Evidence for enhanced bioavailability of trace elements in the marine ecosystem of Deception Island, a volcano in Antarctica

This study assessed whether trace elements present at Deception Island, an active submarine volcano in the Antarctic Peninsula, show enhanced biological availability to the local marine community. Using a weak acid extraction method to dissolve organic material and leach associated but not constitutive trace elements of sediments, fifteen elements were measured from seafloor sediment, seawater particulates, and tissues of benthic (bivalves, brittlestars, sea urchins) and pelagic (demersal and pelagic fishes, krill) organisms collected in the flooded caldera. The highest element concentrations were associated with seafloor sediment, the lowest with seawater particulates and organism tissues. In the case of Ag and Se, concentrations were highest in organism tissue, indicating contamination through the food chain and biomagnification of those elements. The elements Al, Fe, Mn, Sr, Ti, and to a lesser extent Zn, were the most concentrated of the trace elements for all sample types. This indicates that the whole ecosystem of Deception Island is contaminated with trace elements from local geothermal activity, which is also reflected in the pattern of element contamination in organisms. Accordingly, element concentrations were higher in organisms collected at Deception Island compared to those from the neighboring non-active volcanic King George Island, suggesting that volcanic activity enhances bioavailability of trace elements to marine organisms. Trace element concentrations were highest in digestive tissue of organisms, suggesting that elements at Deception Island are incorporated into the marine food web mainly through a dietary route.     

An asperity model to simulate rupture along heterogeneous fault surfaces

A model has been developed to simulate the statistical and mechanical nature of rupture on a heterogeneous strike-slip fault. The model is based on the progressive failure of circular asperities of varying sizes and strengths along a fault plane subjected to a constant far-field shear displacement rate. The basis of the model is a deformation and stress intensity factory solution for a single circular asperity under a unidirectional shear stress. The individual asperities are unified through the fault stiffness and the far-field stress and displacement. During fault deformation asperities can fail and reheal, resulting in changes in the local stresses in the asperities, stress drops, and changes in the stiffness of the fault. Depending on how the stress is redistributed following asperity failure and on the strenghts of the neighboring asperities an earthquake event can be the failure of one or more asperities. Following an earthquake event seismic source parameters such as the stress drop, energy change, and moment magnitude are calculated. Results from the model show a very realistic pattern of earthquake rupture, with reasonable source parameters, the proper magnitude-frequency behavior, and the development of characteristic earthquakes. Also the progression ofb-values in the model gives some insight into the phenomenon of self-organized criticality.     

Chronology of the Lower–Middle Pleistocene succession of the south-western part of the Crotone Basin (Calabria,Southern Italy)

Biostratigraphy based on calcareous nannofossils, integrated by magnetostratigraphic, geochronological and isotopic data, allowed establishing a precise chronological framework for the Pleistocene succession within the south-western sector of the Crotone Basin (Calabria, Southern Italy), where the Pliocene–Pleistocene global stratotype section and point is defined, thus demonstrating that sedimentation was quasi-continuous during most of the Lower and Middle Pleistocene.At a large scale, the Pleistocene succession in this sector of the Crotone Basin is characterized by an evident shallowing-upwards trend, showing facies changes from bathyal to shelfal to littoral/continental. However, comparison between adjacent sectors within the investigated area demonstrates that stratigraphic architectures change vastly on very short distances. Our chronological constraints indicate that such changes in sedimentation styles probably occurred in response to differential subsidence rates, which originated tectonically-controlled synsedimentary structures where accommodation space and sediment yield were allotted unevenly. This articulated physiography led to striking differences in the overall thicknesses and organization of Pleistocene stratigraphies and, eventually, to a distinct diachroneity in the first appearance of shallow-marine deposits. In addition, superimposed are complex interplays between regional and local tectonics, eustasy and orbitally-forced climate changes. These interactions have been highlighted by the oxygen isotope stratigraphy established for a part of the studied succession, which is likely to document almost continuously the interval from Marine Isotope Stage (MIS) 26 to MIS 17. In its younger part (post-MIS 17), chronological ties are poor, as the succession is dominated by shallow-water to continental deposits showing a prominent organization into cyclothems. Nevertheless, based on the chronology of the underlying units, it is feasible that basin infill ended during MIS 15-MIS 14 times.     

ROBUST: The ROle of BUffering capacities in STabilising coastal lagoon ecosystems

“Buffer capacities” has been defined in ecology as a holistic concept (e.g., Integration of Ecosystem Theories: A Pattern, second ed. Kluwer, Dordrecht, 1997, 388pp), but we show that it can also be worked out in mechanistic studies. Our mechanistic approach highlights that “buffering capacities” can be depleted progressively, and, therefore, we make a distinction between current and potential “buffering capacities”. We have applied this concept to understand the limited “local stability” in seagrass ecosystems and their vulnerability towards structural changes into macro-algal dominated communities. We explored the following processes and studied how they confer buffering capacities to the seagrass ecosystem: (i) net autotrophy is persistent in Zostera noltii meadows where plant assimilation acts as a sink for nutrients, this contrasted with the Ulva system that shifted back and forth between net autotrophy and net heterotrophy; (ii) the Z. noltii ecosystem possesses a certain albeit rather limited capacity to modify the balance between nitrogen fixation and denitrification, i.e., it was found that in situ nitrogen fixation always exceeded denitrification; (iii) the nitrogen demand of organoheterotrophic bacteria in the sediment results in nitrogen retention of N in the sediment and hence a buffer against release of nitrogen compounds from sediments, (iv) habitat diversification in seagrass meadows provides shelter for meiofauna and hence buffering against adverse conditions, (v) sedimentary iron provides a buffer against noxious sulfide (note: bacterial sulfide production is enhanced in anoxic sediment niches by increased organic matter loading). On the other hand, in the coastal system we studied, sedimentary iron appears less important as a redox-coupled buffer system against phosphate loading. This is because most inorganic phosphate is bound to calcium rather than to iron. In addition, our studies have highlighted the importance of plant–microbe interactions in the seagrass meadows.