Cellular responses in the mussel Mytilus edulis following exposure to diesel oil emulsions: Reproductive and nutrient storage cells

The objectives of this study were to examine, and quantify with the aid of stereological techniques,^1,2 the effects of exposure to hydrocarbons on the reproductive and nutrient storage cell systems in the marine mussel, Mytilus edulis. In addition, the capacity for recovery of these cell systems was quantified following a period of hydrocarbon depuration. The second phase of these investigations examined the significance of nutritional reserves at the time of exposure to hydrocarbons and how this may influence the animal's ability to survive the insult. The results (Table 1) indicated that, first, hydrocarbons had a deleterious effect on the nutritional storage cells leading to reduced fecundity and oocyte atresia (degeneration). Given a period of depuration, however, there were indications of a recovery in both the reproductive and storage cell systems. Second, the ability of mussels to survive hydrocarbon exposure was dependent upon the nutrient reserves at the onset of exposure.     

Lysosomal reaction to xenobiotics in mussel hemocytes using BODIPY-FL-verapamil

Many cellular and sub-cellular biomarkers associated with mussel (Mytilus edulis) digestive gland and kidney have been characterised. The lysosomal compartment of these tissues have been recognised as being particularly sensitive, exhibiting pollutant induced responses which could be potentially used as a ‘biomarker’. However, relatively few studies have investigated the lysosomal response within molluscan hemocytes. This study was conducted to test whether lysosomal reactions, in live hemocytes isolated from mussels, can be used as a biomarker of pollutant exposure and deleterious effect. Lysosomal responses to a number of hydrocarbons, including anthracene and phenanthrene, and to the amphiphilic heterocylic chemical, chlorpromazine, were examined. The supravital dye neutral red (NR) was used to examine lysosomal membrane fragility, following xenobiotic exposure. NR was also used to verify the lysosomal compartment as the reported accumulation site of a new molecular probe, BODIPY-FL-verapamil (BFLV). The use of BFLV, with confocal laser microscopy and image analysis enabled visualisation and quantification of lysosomal distribution and perturbation. BFLV showed that exposure of molluscan hemocytes to xenobiotics (20 ppb–10 ppm) induced the formation of pathologically enlarged lysosomes. The internal trafficking of lysosomes was shown to be severely compromised after exposure to chlorpromazine. Exposed molluscan hemocytes exhibited significantly reduced lysosomal retention times, for neutral red. Preliminary data is presented demonstrating the opportunity for these non-destructive biomarker techniques to detect pollution gradients in situ.     

Textural trends in turbidites and slurry beds from the Oligocene flysch of the East Carpathians, Romania

Deep‐water sandstone beds of the Oligocene Fusaru Sandstone and Lower Dysodilic Shale, exposed in the Buz?u Valley area of the East Carpathian flysch belt, Romania, can be described in terms of the standard turbidite divisions. In addition, mud‐rich sand layers are common, both as parts of otherwise ‘normal’ sequences of turbidite divisions and as individual event beds. Eleven units, interpreted as the deposits of individual flows, were densely sampled, and 87 thin sections were point counted for grain size and mud content. S₃/T_a divisions, which form the bulk of most sedimentation units, have low internal textural variability but show subtle vertical trends in grain size. Most commonly, coarse‐tail normal grading is associated with fine‐tail inverse grading. The mean grain size can show inverse grading, normal grading or a lack of grading, but sorting tends to improve upward in most beds. Fine‐tail inverse grading is interpreted as resulting from a decreasing effectiveness of trapping of fines during rapid deposition from a turbidity current as the initially high suspended‐load fallout rate declines. If this effect is strong enough, the mean grain size can show subtle inverse grading as well. Thus, thick inversely graded intervals in deep‐water sands lacking traction structures do not necessarily imply waxing flow velocities. If the suspended‐load fallout rate drops to zero after the deposition of the coarse grain‐size populations, the remaining finer grained flow bypasses and may rework the top of the S₃ division, forming well‐sorted, coarser grained, current‐structured T_t units. Alternatively, the suspended‐load fallout rate may remain high enough to prevent segregation of fines, leading to the deposition of significant amounts of mud along with the sand. Mud content of the sandstones is bimodal: either 3–13% or more than 20%. Two types of mud‐rich sandstones were observed. Coarser grained mud‐rich sandstones occur towards the upper parts of S₃/T_a divisions. These units were deposited as a result of enhanced trapping of mud particles in the rapidly deposited sediment. Finer grained mud‐rich units are interbedded with ripple‐laminated very fine‐grained sandy T_c divisions. During deposition of these units, mud floccules were hydraulically equivalent to the very fine sand‐ and silt‐sized sediment. The mud‐rich sandstones were probably deposited by flows that became transitional between turbidity currents and debris flows during their late‐stage evolution.     

New age estimates and climatostratigraphic correlations for the Borrobol and Penifiler Tephras: evidence from Abernethy Forest,Scotland

The emerging tephrostratigraphy of NW Europe spanning the last termination (ca. 15–9 ka) provides the potential for synchronizing marine, ice‐core and terrestrial records, but is currently compromised by stratigraphic complications, geochemical ambiguity and imprecise age estimates for some layers. Here we present new tephrostratigraphic, radiocarbon and chironomid‐based palaeotemperature data from Abernethy Forest, Scotland, that refine the ages and stratigraphic positions of the Borrobol and Penifiler tephras. The Borrobol Tephra (14.14–13.95 cal ka BP) was deposited in a relatively warm period equated with Greenland Interstadial sub‐stage GI‐1e. The younger Penifiler Tephra (14.09–13.65 cal ka BP) is closely associated with a cold oscillation equated with GI‐1d. We also present evidence for a previously undescribed tephra layer that has a major‐element chemical signature identical to the Vedde Ash. It is associated with the warming trend at the end of the Younger Dryas, and dates between 11.79 and 11.20 cal ka BP. Copyright © 2011 John Wiley & Sons, Ltd.     

Combined hillslope diffusion and sediment transport simulation applied to landscape dynamics modelling

We present a new numerical approach for simulating geomorphic and stratigraphic processes that combines open‐channel flow with non‐uniform sediment transport law and semi‐empirical diffusive mass wasting. It is designed to facilitate modelling of surface processes across multiple space‐ and time‐scales, and under a variety of environmental and tectonic conditions. The physics of open‐channel flow is primarily based on an adapted Lagrangian formulation of shallow‐water equations. The interaction between flow and surface geology is performed by a non‐uniform total‐load sediment transport law. Additional hillslope processes are simulated using a semi‐empirical method based on a diffusion approach. In the implementation, the resolution of flow dynamics is made on a triangulated grid automatically mapped and adaptively remeshed over a regular orthogonal stratigraphic mesh. These new methods reduce computational time while preserving stability and accuracy of the physical solutions. In order to illustrate the potential of this method for landscape and sedimentary system modelling, we present a set of three generic experiments focusing on assessing the influence of contrasting erodibilities on the evolution of an active bedrock landscape. The modelled ridges morphometrics satisfy established relationships for drainage network geometry and slope distribution, and provide quantitative information on the relative impact of hillslope and channel processes, sediment discharge and alluviation. Our results suggest that contrasting erodibility can stimulate autogenic changes in erosion rate and influence the landscape morphology and preservation. This approach offers new opportunities to investigate joint landscape and sedimentary systems response to external perturbations. The possibility to define and track a large number of materials makes the implementation highly suited to model source‐to‐sink problems where material dispersion is the key question that needs to be addressed, such as natural resources exploration and basin analysis. Copyright © 2014 John Wiley & Sons, Ltd.     

The Final Stage of Silicic Island Arc Magmatism in the Northern Urals

Doklady Earth Sciences - The date of cessation of calc-alkaline volcanic complex accumulation within the Devonian (Frasnian) island arc in the Northern Urals was determined for the first time. It...     

Test of AMS 14C dating of pollen concentrates using tephrochronology

Previous attempts to radiocarbon date sediments >10 kyr from the high rainfall region of Westland, New Zealand, a critical location for investigation of interhemispheric patterns of climate change, have been problematic. This study, building on recent work by Vandergoes and Prior ( 2003 ), shows that AMS ¹⁴C dating of pollen concentrates has potential to provide more reliable ages than other sediment constituents, including plant macrofossils. The method was applied to sediments from three sites containing the 22.6k ¹⁴C yr Kawakawa Tephra, which provided an independent test of the ¹⁴C ages. Although some minor laboratory contamination was detected in tests on background standards, the modelled relationship between sample mass and measured ¹⁴C content permitted an appropriate correction to be determined. Improved pollen concentrations derived by density separation between 1.4 and 1.2 specific gravity and sieving in the range 10–50 μm provided either older ages than other fractions of the same sample or, where in situ contamination was not evident, equivalent ages. Differences in degree of in situ contamination between depositional environments indicated that, in Westland, lake sites may be less susceptible to contamination by younger carbon than peat sites, where this process may be facilitated by root penetration into underlying sediments. Copyright © 2006 John Wiley & Sons, Ltd.     

Argon auroral emissions

Argon is the third most abundant constituent of the atmosphere, but has not been previously detected by any ground-based optical remote sensing method. We report observation of argon emissions at λ840.82 and λ842.46 nm during intense aurora. These are most likely excited by direct electron impact. The maximum argon intensity observed is 270 R. Argon is the fifth elemental emission conclusively observed in geo-aurora, joining N, O, H and He.