Compressibility of titanosilicate melts

The effect of composition on the relaxed adiabatic bulk modulus (K₀) of a range of alkali- and alkaline earth-titanosilicate [X ₂ ^n/n+ TiSiO₅ (X=Li, Na, K, Rb, Cs, Ca, Sr, Ba)] melts has been investigated. The relaxed bulk moduli of these melts have been measured using ultrasonic interferometric methods at frequencies of 3, 5 and 7 MHz in the temperature range of 950 to 1600°C (0.02 Pa s < _s < 5 Pa s). The bulk moduli of these melts decrease with increasing cation size from Li to Cs and Ca to Ba, and with increasing temperature. The bulk moduli of the Li-, Na-, Ca- and Ba-bearing metasilicate melts decrease with the addition of both TiO₂ and SiO₂ whereas those of the K-, Rb- and Cs-bearing melts increase. Linear fits to the bulk modulus versus volume fraction of TiO₂ do not converge to a common compressibility of the TiO₂ component, indicating that the structural role of TiO₂ in these melts is dependent on the identity of the cation. This proposition is supported by a number of other property data for these and related melt compositions including heat capacity and density, as well as structural inferences from X-ray absorption spectroscopy (XANES). The compositional dependence of the compressibility of the TiO₂ component in these melts explains the difficulty incurred in previous attempts to incorporate TiO₂ in calculation schemes for melt compressibility. The empirical relationship KV^-4/3 for isostructural materials has been used to evaluate the compressibility-related structural changes occurring in these melts. The alkali metasilicate and disilicate melts are isostructural, independent of the cation. The addition of Ti to the metasilicate composition (i.e. X₂TiSiO₅), however, results in a series of melts which are not isostructural. The alkaline-earth metasilicate and disilicate compositions are not isostructural, but the addition of Ti to the metasilicate compositions (i.e. XTiSiO₅) would appear, on the basis of modulus-volume systematics, to result in the melts becoming isostructural with respect to compressibility.     

Peace Parks and jaguar trails: transboundary conservation in a globalizing world

An increasingly utilized strategy for expanding conservation in the developing world has been the promotion of protected areas that supersede national borders. Alternatively known as transfrontier biosphere reserves, transfrontier or transboundary conservation areas, or Peace Parks, these protected areas are aggressively advanced by conservation agencies for their purported ecological and economic benefits. This article provides a comparative assessment of two case studies to understand the various impacts of transboundary conservation. The Great Limpopo Transfrontier Park, which unites protected areas in South Africa, Mozambique and Zimbabwe, is contrasted with efforts to protect jaguars along the United States–Mexico border. We argue that while these cases are promising for the purposes of biodiversity protection, they demonstrate that transboundary conservation can minimize political context, contributes to the hegemony of international conservation agendas, and remains closely linked to economic neoliberalism and decentralization in the developing world.

Late Holocene climates of the Near East deduced from Dead Sea level variations and modern regional winter rainfall

The Dead Sea is a terminal lake of one of the largest hydrological systems in the Levant and may thus be viewed as a large rain gauge for the region. Variations of its level are indicative of the climate variations in the region. Here, we present the decadal- to centennial-resolution Holocene lake-level curve of the Dead Sea. Then we determine the regional hydroclimatology that affected level variations. To achieve this goal we compare modern natural lake-level variations and instrumental rainfall records and quantify the hydrology relative to lake-level rise, fall, or stability. To quantify that relationship under natural conditions, rainfall data pre-dating the artificial Dead Sea level drop since the 1960s are used. In this respect, Jerusalem station offers the longest uninterrupted pre-1960s rainfall record and Jerusalem rains serve as an adequate proxy for the Dead Sea headwaters rainfall. Principal component analysis indicates that temporal variations of annual precipitation in all stations in Israel north of the current 200 mm yr⁻¹ average isohyet during 1940–1990 are largely synchronous and in phase (70% of the total variance explained by PC1). This station also represents well northern Jordan and the area all the way to Beirut, Lebanon, especially during extreme drought and wet spells. We (a) determine the modern, and propose the past regional hydrology and Eastern Mediterranean (EM) climatology that affected the severity and length of droughts/wet spells associated with multiyear episodes of Dead Sea level falls/rises and (b) determine that EM cyclone tracks were different in average number and latitude in wet and dry years in Jerusalem. The mean composite sea level pressure and 500-mb height anomalies indicate that the potential causes for wet and dry episodes span the entire EM and are rooted in the larger-scale northern hemisphere atmospheric circulation. We also identified remarkably close association (within radiocarbon resolution) between climatic changes in the Levant, reflected by level changes, and culture shifts in this region.     

Community turnover provides insight into variable invertebrate recovery between restored streams with different integrated catchment management plans

ABSTRACT

Understanding temporal patterns in restored environments is important for identifying potential barriers to recovery and improved management of degraded habitats. In this paper, we use temporal beta diversity analyses to compare invertebrate community recovery trajectories in three restored agricultural stream sites under different integrated catchment plans, a native forest reference site, and two unmodified pasture control stream sites over 24 years. The restored sites diverged from their initial community composition over time and became more similar to the reference site community, which was relatively stable over time. Variation partitioning showed that prior to restoration beta diversity was primarily associated with environmental and spatial drivers, whereas post-restoration beta diversity was more influenced by temporal and environmental drivers, including changes in substrate size, fine sediments, water clarity, and nutrients, as well as temperature and flow regime. Species’ contributions to beta diversity varied between sites and years, with sensitive EPT taxa contributing more in reference and control sites. However, contributions of some EPT species, particularly mayflies, increased in restored sites post-ICM. In summary, after nearly two decades of ICM, restored stream sites show recovery towards reference conditions, yet differences persist, indicating that rehabilitation may take longer, depending on the restoration goals.     

Population structure of Haliotis rubra from South Australia inferred from nuclear and mtDNA analyses

1Introduction ThemajorityofAustralia’sabalonefisheryex ports(5.135kt,worth＄216millionin2002～2003,ABARE2004)consistofblacklipabalone(HaliotisrubraLeach,1814).AssuchH.rubrais consideredasanimportantmarineresourcewithin Australia.Likemanyabalonespecieswor…     

Biofouling confounds the uptake of trace organic contaminants by semi-permeable membrane devices (SPMDs)

The outer layers of layflat, low density polyethylene plastic tubing (the principal component of semi-permeable membrane devices, SPMDs) were biofouled at a clean site in Hong Kong coastal waters for periods of 1–4 weeks. Following pre-fouling, triolein was added to the SPMDs and, along with control (unfouled) devices, they were exposed to a range of organochlorine pesticides (-HCH, aldrin, p,p^′-DDT) and PAHs (anthracene, fluoranthene and benzo(a)pyrene) under laboratory conditions. Results showed that the uptake of contaminants by SPMDs was severely reduced by as much as 50% under fouling conditions in comparison to unfouled controls. The ultimate utility of SPMDs as passive monitors is thus reduced, although alternative measures, such as the use of permeability reference compounds may compensate, and allow for realistic evaluations of dissolved environmental concentrations in aquatic environments. However, due to the complexities involved in such procedures––especially as they need to be conducted on a case-by-case basis––the utility of SPMDs appears to be limited for estimates of bioavailability unless necessary calibrations are undertaken within each environment that the sampler is used.     

Historical and Modern Fluctuations of Lakes Tanganyika and Rukwa and Their Relationship to Rainfall Variability

This paper describes the fluctuations of Lakes Tanganyika and Rukwa over the last two centuries. Lake chronologies extending back to the late eighteenth century are derived from reports of European visitors, settlers and explorers and from oral accounts of the local peoples. The historical fluctuations are meshed with the modern record to provide a picture of the lakes' fluctuations until the late twentieth century. The historical fluctuations of the lakes are quite similar. The most important of these are low levels during the first half of the nineteenth century, very high stands in the last decades of the nineteenth century, and, around the turn of the century, a rapid fall to twentieth century levels. This pattern is ubiquitous throughout eastern Africa and is apparent in numerous other lakes, including Victoria, Naivasha, Stefanie, Turkana, Malawi and Chilwa. Driest periods were in the 1920s or earlier and in the 1950s. Lake Tanganyika returned to extremely high stands in the 1960s and has continued to maintain relatively high stands since that time. Lake Rukwa rose to high stands during the 1980s and maintained them for several years. An analysis of rainfall variability shows that these trends are generally explained by variations in catchment rainfall. However, the lakes' responses to rainfall variability are sometimes dissimilar because Lake Rukwa is a closed basin. Our results demonstrate the complexity of the rainfall/lake-level relationships and the need to use water balance relationships in order to interpret the lakes' historical or paleo-fluctuations in terms of rainfall.     

Scales of perception: public awareness of regional and neighborhood climates

Understanding public perceptions of climate is critical for developing an effective strategy to mitigate the effects of human activity on the natural environment and reduce human vulnerability to the impacts of climate change. While recent climate assessments document change among various physical systems (e.g., increased temperature, sea level rise, shrinking glaciers), environmental perceptions are relatively under-researched despite the fact that there is growing skepticism and disconnect between climate science and public opinion. This study utilizes a socio-ecological research framework to investigate how public perceptions compared with environmental conditions in one urban center. Specifically, air temperature during an extreme heat event was examined as one characteristic of environmental conditions by relating simulations from the Weather Research and Forecast (WRF) atmospheric model with self-reported perceptions of regional and neighborhood temperatures from a social survey of Phoenix, AZ (USA) metropolitan area residents. Results indicate that: 1) human exposure to high temperatures varies substantially throughout metropolitan Phoenix; 2) public perceptions of temperature are more strongly correlated with proximate environmental conditions than with distal conditions; and 3) perceptions of temperature are related to social characteristics and situational variables. The social constructionist paradigm explains public perceptions at the regional scale, while experience governs attitude formation at the neighborhood scale.     

A low-level jet along the Benguela coast, an integral part of the Benguela current ecosystem

The Benguela Current Ecosystem of Southern Africa is the strongest wind-driven coastal upwelling system known. This is one of the most productive ocean areas in the world, extremely rich in fishery resources with a total catch in excess of one million tons per annum. Marine life off the coast relies heavily on the nutrient-rich upwellings of the cold Benguela current. Warming events occur along this coast in association with many El Niños. These tremendously disrupt the coastal ecosystem, reducing productivity and devastating the anchovy and sardine fisheries. This article demonstrates for the first time the existence of a low-level atmospheric jet along the Benguela Coast of the southeastern Atlantic. Blowing parallel to the coast, this jet drives the coastal upwelling system and is part of a mechanism that links Pacific El Niño events to Southern Africa. The existence of such a jet has tremendous implications for the Benguela current and its response to climatic variability and change because a positive feedback exists between the intensity of this jet and the intensity of coastal upwelling. This may enhance the response of the Benguela Current Ecosystem to climatic variability, making it particularly susceptible to the impacts of global climate change.