Mass mortality of the fan mussel,Pinna nobilis in Turkey (eastern Mediterranean)

This study reported the mass mortality events (MMEs) of Pinna nobilis based on diving surveys in Turkey. Data were collected across 12 sites in the Aegean Sea, and one site in the Sea of Marmara, within the period of June-September 2019. The results showed that a low mortality rate of 10% was found in the Sea of Marmara, and a MME was not detected for this area. In contrast, 97% mortality was recorded for the P. nobilis population distributed in the Turkish Aegean Sea. This discrepancy might be related to the seawater temperature and salinity values of these two seas. The waters of the Sea of Marmara were colder and less salty than the Aegean Sea. The findings highlighted the importance of protecting the healthy population of critically endangered fan mussels in the Sea of Marmara. It was recommended that sound management plans comprising of monitoring, enforcement and public awareness activities could be implemented in order to achieve this.     

Open-source approaches for location cover models: capabilities and efficiency

Journal of Geographical Systems - Location cover models are aimed at siting facilities so as to provide service to demand efficiently. These models are crucial in the management, planning and...     

TIN-based Tag Map Layout

With the widespread use of tag clouds, multiple map-based variations have been proposed. Like standard tag clouds (also called word clouds), these ‘tag maps’ all share the basic strategy of displaying words within a ‘geographic space’ and scaling the word size to depict frequency (or importance) of those words within some dataset. While some tag maps simply plot a standard tag cloud on top of a map, the subset of tag maps we focus on here are those in which the collection of words are displayed within bounded geographic regions (often of irregular shape) that the words are relevant for. For this form of tag map, map scale and polygon shape add constraints to word size and position that have not been considered in most prior approaches to tag map word layout. In this paper, we present a layout strategy for tag map generation that includes consideration of the shape and size of the geographical regions acting as containers for the tags. The method introduced here uses a triangulated irregular network (TIN) to subdivide the geographical region into many triangle subareas, with the centroid of each triangle being a potential location to centre a tag on. All the triangles are sorted by their area and all the tags are sorted by their weight value (e.g. frequency, importance or popularity). Positioning of tags is undertaken sequentially from most important (or frequent or popular) with potential locations being the TIN triangle centroids (tried from largest to smallest triangle). After each tag placement, the TIN is recalculated to integrate the tag centroid and bounding corners into the TIN creation. The limited whitespace in the geographical region, at any specific scale, is used fully by dynamically adjusting the font size along with the number and the direction of tags. The method can be applied to add tags within geographic polygons that are convex, concave and other more complex regions containing holes or islands.     

Challenges in applying capacitated covering models

Service system planning has long been supported by location‐covering models designed to address access and accessibility issues. An important aspect of many systems is limits on service, often conceptualized as facility capacities. Much research can be found that proposes modeling approaches and solution techniques to account for capacitated covering problems, and commercial GIS software exists that is capable of structuring and applying facility service limits. This article reviews issues and challenges associated with the application of capacitated covering models, including critical evaluation of allocation approaches and GIS capabilities. Case studies involving service provision in two cities in California—San Jose and Santa Barbara—are provided to highlight associated issues faced in practice. While user‐friendly commercial software makes it easy to access capacitated cover models, there remain challenges for addressing underlying considerations and assumptions in practice.     

Seasonal Shift in Community Structure of Periphytic Ciliates in Estuarine Waters in the Northern Bay of Bengal,Bangladesh

To investigate the seasonal heterogeneity of the periphytic ciliate communities, a 1-year baseline survey was conducted in the Karnaphuli River estuary, northern Bay of Bengal, Bangladesh. A total of 54 ciliate species were recorded, including seven common and 14 dominant species. Maximum species number was in autumn whereas maximum abundance was in winter; the minimum for both occurred in summer. Multivariate analyses, i.e., canonical analysis of principal coordinates (CAP) and principal co-ordinates analysis (PCoA), revealed a clear seasonal heterogeneity of community structure and environmental variables. Multivariate correlation analysis (RELATE) demonstrated that the community structure of the periphytic ciliate communities was significantly correlated with environmental variables, and best matching analysis (BIOENV) indicated that heterogeneity of community patterns was mainly driven by water temperature, pH, dissolved oxygen, total dissolved solids and nutrients. Species richness and diversity peaked in autumn whereas species evenness peaked in summer. These results suggest that environmental conditions shape periphytic ciliate community structure, which is a potentially useful bio-indicator of estuarine water quality.     

Thermochronological insights into the structural contact between the Tian Shan and Pamirs,Tajikistan

Multi‐method thermochronology along the Vakhsh‐Surkhob fault zone reveals the thermotectonic history of the South Tian Shan–Pamirs boundary. Apatite U/Pb analyses yield a consistent age of 251 ± 2 Ma, corresponding to cooling below ~550–350°C, related to the final closure of the Palaeo‐Asian Ocean and contemporaneous magmatism in the South Tian Shan. Zircon (U–Th–Sm)/He ages constrain cooling below ~180°C to the end of the Triassic (~200 Ma), likely related either to deformation induced by the Qiangtang collision or to the closure of the Rushan Ocean. Apatite fission track thermochronology reveals two low‐temperature (<120°C) thermal events at ~25 Ma and ~10 Ma, which may be correlated with tectonic activity at the distant southern Eurasian margin. The late Miocene cooling is confirmed by apatite (U–Th–Sm)/He data and marks the onset of mountain building within the South Tian Shan that is ongoing today.     

Field methods for amending marine sediment with activated carbon and assessing treatment effectiveness

Previous laboratory studies have shown reductions in PCB bioavailability for sediments amended with activated carbon (AC). Here we report results on a preliminary pilot-scale study to assess challenges in scaling-up for field deployment and monitoring. The goals of the preliminary pilot-scale study at Hunters Point Shipyard (San Francisco, USA) were to (1) test the capabilities of a large-scale mixing device for incorporating AC into sediment, (2) develop and evaluate our field assessment techniques, and (3) compare reductions in PCB bioavailability found in the laboratory with well-mixed systems to those observed in the field with one-time-mixed systems. In this study we successfully used a large-scale device to mix 500kg of AC into a 34.4m(2) plot to a depth of 1ft, a depth that includes the majority of the biologically active zone. Our results indicate that after 7 months of AC-sediment contact in the field, the 28-day PCB bioaccumulation for the bent-nosed clam, Macoma nasuta, field-deployed to this AC-amended sediment was approximately half of the bioaccumulation resulting from exposure to untreated sediment. Similar PCB bioaccumulation reductions were found in laboratory bioassays conducted on both the bivalve, M. nasuta and the estuarine amphipod, Leptocheirus plumulosus, using sediment collected from the treated and untreated field plots one year after the AC amendment occurred. To further understand the long-term effectiveness of AC as an in situ treatment strategy for PCB-contaminated sediments under field conditions, a 3-year comprehensive study is currently underway at Hunters Point that will compare the effectiveness of two large-scale mixing devices and include both unmixed and mixed-only control plots.     

Matrix and whole‐rock fractionations in the Acfer 094 type 3.0 ungrouped carbonaceous chondrite

Abstract– We used the electron microprobe to study matrix in the ungrouped type 3.0 carbonaceous chondrite Acfer 094 using 7 × 7‐point, focused‐beam arrays; data points attributable to mineral clasts were discarded. The grid areas show resolvable differences in composition, but differences are less pronounced than we observed in studies of CR2 LaPaz Icefield (LAP) 02342 (Wasson and Rubin [2009]) and CO3.0 Allan Hills A77307 (Brearley [1993]). A key question is why Acfer shows an anomalously uniform composition of matrix compared with these other carbonaceous chondrites. Both whole‐rock and matrix samples of Acfer 094 show enhancements of Ca and K; it appears that these reflect contamination during hot desert weathering. By contrast, the whole‐rock abundance of Na is low. Although weathering effects are responsible for some fractionations, it appears that nebular effects are also resolvable in matrix compositions in Acfer 094. As with LAP 02342, we infer that the observed differences among different areas were inherited from the solar nebula and may have been carried by porous chondrules that experienced low (about 20%) degrees of melting. Acfer 094 has been comminuted by one or more impact events that may also have caused volatile loss. Thus, despite preserving evidence (e.g., an exceptionally high content of presolar SiC) implying a high degree of pristinity, Acfer 094 is far from pristine in other respects. This evidence of comminution and an O‐isotopic composition similar to values measured in metamorphosed CM chondrites suggest that Acfer was hydrated before being outgassed by the inferred impact event. Convection within the plume associated with the impact event probably also contributed to the homogenization of the Acfer 094 matrix.     

Decade time-scale modulation of low-mass X-ray binaries

Regular observations by the All-Sky Monitor aboard the Rossi X-ray Timing Explorer satellite have yielded well-sampled light curves with a time baseline of over 10 years. We find that up to eight of the 16 brightest persistent low-mass X-ray binaries (LMXBs) show significant, possible sinusoidal, variations with periods of the order of 10 years. We speculate on its possible origin and prevalence in the population of LMXBs, and we find the presence of a third object in the system, or long-period variability intrinsic to the donor star, as being attractive origins for the X-ray flux modulation we detect. For some of the objects in which we do not detect a signal, there is substantial short-term variation which may hide modest modulation on long time-scales. Decade time-scale modulations may thus be even more common.     

Adaptive meshing in a mixed regime hydrologic simulation model

Problems in hydrology frequently have moving fronts and dynamic driving mechanisms such as wells. Since the location of important features changes during a simulation, accurate modeling requires uniformly fine resolution or the ability to change resolution during the simulation. We will describe an algorithm for refinement and unrefinement of tetrahedral/triangular meshes that has been implemented in the adaptive hydrology (ADH) code. The codes including the refinement/unrefinement algorithms are implemented in parallel to accommodate problems with large run time and memory requirements. In this paper, we describe the parallel, adaptive grid algorithm used in ADH and show the resulting grids from some example problems.