Eocene succession on the East Shetland Platform, North Sea

A sand-prone Middle Eocene sequence is recognized in three cored boreholes on the East Shetland Platform. Three lithostratigraphic divisions are recognized: Lower Sand Unit, Main Sand Unit and Upper Claystone Unit. The Lower Sand Unit is of fluvio-deltaic origin, occurring on the southern part of the East Shetland Platform. The Main Sand Unit represents the subsequent transgression of the delta. The unit comprises a set of highstand shelf systems tracts separated by glauconitic bands and reflected by palynological assemblage breaks. The presence of reworked palynofloras in sediments of late Middle Eocene age implies derivation of sediment from the north-west part of the East Shetland Platform. Although it is tempting to ascribe sea level changes to the sediment pattern, a tentative correlation with the Hampshire Basin only highlights the difficulties involved.     

Microscopic physical biomarkers in carbonate hot springs: implications in the search for life on Mars.

Physical evidence of life (physical biomarkers) from the deposits of carbonate hot springs were documented at the scale of microorganisms--submillimeter to submicrometer. The four moderate-temperature (57 to 72 degrees C), neutral pH springs reported on in this study, support diverse communities of bacteria adapted to specific physical and chemical conditions. Some of the microbes coexist with travertine deposits in endolithic communities. In other cases, the microbes are rapidly coated and destroyed by precipitates but leave distinctive mineral fabrics. Some microbes adapted to carbonate hot springs produce an extracellular polymeric substance which forms a three-dimensional matrix with living cells and cell remains, known as a biofilm. Silicon and iron oxides often coat the biofilm, leading to long-term preservation. Submicrometer mineralized spheres composed of calcium fluoride or silica are common in carbonate hot spring deposits. Sphere formation is biologically mediated, but the spheres themselves are apparently not fossils or microbes. Additionally, some microbes selectively weather mineral surfaces in distinctive patterns. Hot spring deposits have been cited as prime locations for exobiological exploration of Mars. The presence of preserved microscopic physical biomarkers at all four sites supports a strategy of searching for evidence of life in hot spring deposits on Mars.     

Long-term change in eelgrass distribution at Bahía San Quintín,Baja California,Mexico, using satellite imagery

Seagrasses are critically important components of many marine coastal and estuarine ecosystems, but are declining worldwide. Spatial change in distribution of eelgrass,Zostera marina L., was assessed at Bahía San Quintín, Baja California, Mexico, using a map to map comparison of data interpreted from a 1987 Satellite Pour l'Observation de la Terre multispectral satellite image and a 2000 Landsat Enhanced Thematic Mapping image. Eelgrass comprised 49% and 43% of the areal extent of the bay in 1987 and 2000, respectively. Spatial extent of eelgrass was 13% less (−321 ha) in 2000 than in 1987 with most losses occurring in subtidal areas. Over the 13-yr study period, there was a 34% loss of submerged eelgrass (−457 ha) and a 13% (+136 ha) gain of intertidal eelgrass. Within the two types of intertidal eelgrass, the patchy cover class (<85% cover) expanded (+250 ha) and continuous cover class (≥85% cover) declined (−114 ha). Most eelgrass losses were likely the result of sediment loading and turbidity caused by a single flooding event in winter of 1992–1993. Recent large-scale agricultural development of adjacent uplands may have exacerbated the effects of the flood. Oyster farming was not associated with any detectable losses in eelgrass spatial extent, despite the increase in number of oyster racks from 57 to 484 over the study period.     

Network Topology and City Accessibility of the Commercial Internet

The rapid growth in this decade of World Wide Web access through the Internet is supported by a complex matrix of telecommunications infrastructure. This paper presents an overview of the history of the Internet and recent efforts to measure its structure and performance, and examines the spatial organization of the commercial Internet backbone. The research presented in this paper differs from previous Internet measurement work in that we apply network analysis methods to evaluate Internet connectivity. Transportation network analysis techniques are applied to measure 1) connectivity of individual service provider networks and 2) accessibility of cities to Internet service. The results reveal many different strategies implemented by service providers in network design as well as large differences in levels of accessibility of cities and regions in the United States. There is also an apparent disparity between population and city accessibility to the Internet.     

South China Sea

The South China Sea is poorly understood in terms of its marine biota, ecology and the human impacts upon it. What is known is most often contained in reports and workshop and conference documents that are not available to the wider scientific community. The South China Sea has an area of some 3.3 million km² and depths range from the shallowest coastal fringe to 5377 m in the Manila Trench. It is also studded with numerous islets, atolls and reefs many of which are just awash at low tide. It is largely confined within the Tropic of Cancer and, therefore, experiences a monsoonal climate being influenced by the Southwest Monsoon in summer and the Northeast Monsoon in winter. The South China Sea is a marginal sea and, therefore, largely surrounded by land. Countries that have a major influence on and claims to the sea include China, Malaysia, the Philippines and Vietnam, although Thailand, Indonesia and Taiwan have some too. The coastal fringes of the South China Sea are home to about 270 million people that have had some of the fastest developing and most vibrant economies on the globe. Consequently, anthropogenic impacts, such as over-exploitation of resources and pollution, are anticipated to be huge although, in reality, relatively little is known about them. The Indo-West Pacific biogeographic province, at the centre of which the South China Sea lies, is probably the world's most diverse shallow-water marine area. Of three major nearshore habitat types, i.e., coral reefs, mangroves and seagrasses, 45 mangrove species out of a global total of 51, most of the currently recognised 70 coral genera and 20 of 50 known seagrass species have been recorded from the South China Sea. The island groups of the South China Sea are all disputed and sovereignty is claimed over them by a number of countries. Conflicts have in recent decades arisen over them because of perceived national rights. It is perhaps because of this that so little research has been undertaken on the South China Sea. What data are available, however, and if Hong Kong is used, as it is herein, as an indicator of what the perturbations of other regional cities upon the South China Sea are like, then it is impacted grossly and an ecological disaster has probably already, but unknowingly, happened.     

Efficacy of Hollow‐Fiber Ultrafiltration for Microbial Sampling in Groundwater

The goal of this study was to test hollow‐fiber ultrafiltration as a method for concentrating in situ bacteria and viruses in groundwater samples. Water samples from nine wells tapping a shallow sandy aquifer in a densely populated village in Bangladesh were reduced in volume approximately 400‐fold using ultrafiltration. Culture‐based assays for total coliforms and Escherichia coli, as well as molecular‐based assays for E. coli, Bacteroides, and adenovirus, were used as microbial markers before and after ultrafiltration to evaluate performance. Ultrafiltration increased the concentration of the microbial markers in 99% of cases. However, concentration factors (CF = post‐filtration concentration/pre‐filtration concentration) for each marker calculated from geometric means ranged from 52 to 1018 compared to the expected value of 400. The efficiency was difficult to quantify because concentrations of some of the markers, especially E. coli and total coliforms, in the well water (WW) collected before ultrafiltration varied by several orders of magnitude during the period of sampling. The potential influence of colloidal iron oxide precipitates in the groundwater was tested by adding EDTA to the pre‐filtration water in half of the samples to prevent the formation of precipitates. The use of EDTA had no significant effect on the measurement of culturable or molecular markers across the 0.5 to 10 mg/L range of dissolved Fe²⁺ concentrations observed in the groundwater, indicating that colloidal iron did not hinder or enhance recovery or detection of the microbial markers. Ultrafiltration appears to be effective for concentrating microorganisms in environmental water samples, but additional research is needed to quantify losses during filtration.     

Stability of massive ground ice bodies in University Valley,McMurdo Dry Valleys of Antarctica: Using stable O–H isotope as tracers of sublimation in hyper-arid regions

To date, studies of the stability of subsurface ice in the McMurdo Dry Valleys of Antarctica have been mainly based on climate-based vapor diffusion models. In University Valley (1800 m), a small glacier is found at the base of the head of the valley, and adjacent to the glacier, a buried body of massive ice was uncovered beneath 20–40 cm of loose cryotic sediments and sandstone boulders. This study assesses the origin and stability of the buried body of massive ice by measuring the geochemistry and stable O–H isotope composition of the ice and applies a sublimation and molecular diffusion model that accounts for the observed trends. The results indicate that the buried massive ice body represents an extension of the adjacent glacier that was buried by a rock avalanche during a cold climate period. The contrasting δ¹⁸O profiles and regression slope values between the uppermost 6 cm of the buried massive ice (upward convex δ¹⁸O profile and S_D-18O = 5.1) and that below it (progressive increase in δ¹⁸O and S_D-18O = 6.4) suggest independent post-depositional processes affected the isotope composition of the ice. The upward convex δ¹⁸O profile in the uppermost 6 cm is consistent with the ice undergoing sublimation. Using a sublimation and molecular diffusion model, and assuming that diffusion occurred through solid ice, the sublimation rate needed to fit the measured δ¹⁸O profile is 0.2 ? 10^? 3 mm yr^? 1, a value that is more similar to net ice removal rates derived from ³He data from cobbles in Beacon Valley till (7.0 ? 10^? 3 mm yr^? 1) than sublimation rates computed based on current climate (0.1–0.2 mm yr^?1). We suggest that the climate-based sublimation rates are offset due to potential ice recharge mechanisms or to missing parameters, particularly the nature and thermo-physical properties of the overlying sediments (i.e., temperature, humidity, pore structure and ice content, grain size).