Magnetotactic bacteria from the human gut microbiome associated with orientation and navigation regions of the brain

Journal of Oceanology and Limnology - Magnetotactic bacteria (MTB), ubiquitous in soil and fresh and saltwater sources have been identified in the microbiome of humans and many animals. MTB...     

Desert margins near the Chinese Loess Plateau during the mid-Holocene and at the Last Glacial Maximum: a model–data intercomparison

Expansion and contraction of desert margins around the globe have been inferred from a variety of proxy data and have since been linked, particularly in northern China and in the sub-Sahel, to changes in freshwater flux, vegetation cover, sea surface temperatures and, perhaps most importantly, monsoon circulations. We present a direct comparison of results from numerical general circulation model experiments for the mid-Holocene and for the Last Glacial Maximum (LGM) with the climatic conditions that have been inferred from loess–paleosol sequences taken from the Chinese Loess Plateau.During the mid-Holocene in northern China, the northwestward migration of the southeast desert margin that has been suggested by grain size analysis is also expressed in the model results. There is a statistically significant wetting of the Plateau region, and increased soil moisture is a consequence of an enhanced summer monsoon whose latent heat release deepens the cyclonic Tibetan low and brings increased low-level convergence and precipitation to the area. North of the desert region, this circulation dries the soil through enhanced atmospheric subsidence, although the northern margin of the desert does not migrate significantly.Expansion of the desert margin toward the southeast at the LGM is small, but there is a statistically significant drying of the Plateau. The local hydrological cycle is reduced, and there is an increase in large-scale atmospheric subsidence over the region that is caused by the presence of the Fennoscandian ice sheet upwind. Model results therefore suggest that, in addition to local micro- and mesoclimatic conditions, regional effects, such as monsoon circulations and distal orography, are also important factors in determining the location of desert margins.     

Restructuring socialist housing estates and its impact on residents’ perceptions: “Renovatsiia” of khrushchevki in St. Petersburg,Russia

This paper explores the issue of restructuring socialist housing estates in St. Petersburg, Russia, with an emphasis on residents’ perceptions of the wide range of economic, social, and environmental impacts of that restructuring. A new housing renewal program, “renovatsiia” (renovation) of khrushchevki, has been controversial from the very beginning and involves the demolition of existing khrushchevki and the construction of new housing on the same sites. By examining the issue within the framework of housing regeneration in the post-socialist context, the paper aims to provide insights into some of the challenges of urban renewal in the housing sector in the second largest Russian city. The paper at the same time investigates the viability of the collaborative planning model in the context of the post-socialist city.     

Fusion of Radar and Optical Data for Land Cover Mapping

Abstract

This study examined the complementarity of radar and optical data for feature identification. Spaceborne radar and Landsat Thematic Mapper (TM ) multispectral data sets were assessed independently and in combination to classify a site near Wad Medani, Sudan. Radar processing procedures included speckle reduction, texture extraction and post‐processing smoothing. Relative accuracy of the resultant classifications was established by comparison to ground truth information derived from field visitation. Neither speckle filtering nor post‐classification smoothing were improvements over the poor results obtained with the unfiltered, original radar data. Texture measures were significant improvements over the original data (20 percent overall accuracy increase) and several, but not all, individual classes had excellent results. Landsat TM had good overall results (80 percent correct) but considerable spectral confusion between urban and bare soil. Combination of radar with Landsat TM greatly improved results, achieving near perfect classification of all individual classes. The systematic strategy of this study, determination of the best individual method before introducing the next procedure, was effective in managing a complex set of analysis possibilities.     

Comparison and Integration of Radar and Optical Data for Land Use/Cover Mapping

Abstract

This study examined the complementarity of spaceborne radar and optical data for surface feature identification. RADARSAT data sets were assessed independently and in combination with Landsat Thematic Mapper (TM) multispectral data. The primary methodology was spectral signature extraction and the application of a statistical decision rule to classify the surface features for a site near Kericho, Kenya. Relative accuracy of the resultant classifications was established by digital integration and comparison to reference information derived from field visitation. Speckle filtering was a great improvement over the poor results achieved with the unfiltered, original radar data but still not adequate for accurate land cover classification. The extraction and use of Variance texture measures was found to be very advantageous. The overall results were not significant improvements over speckle removal (6% increase) but several individual classes, forest and urban, had excellent results with texture. Combinations of radar with Landsat TM greatly improved results, achieving near perfect classification of all individual classes. The highest overall accuracy was achieved with a merger that included the best individual texture image and six reflectance bands of the TM data. The systematic strategy of this study, determination of the best individual method before introducing the next procedure, was effective in managing a very complex, almost infinite set of analysis possibilities.     

Spatiotemporal environmental triggers of Ebola and Marburg virus transmission

Despite their fame, Ebola and Marburg viruses (family Filoviridae) remain mysterious. Filovirus outbreaks are restricted to tropical Africa, but their likely geographic extent has been outlined only recently, and their natural reservoir host(s) remains unidentified. If environmental conditions associated with outbreaks in space and time can be identified precisely, much could be learned about the ecology, evolution and transmission of these viruses. We examined five filovirus outbreaks for which time series of remotely sensed data (NDVI values) are available and for which the reservoir-to-human index case transmission timing and location are known. A wavelet analysis was used to detect anomalous behaviour in the NDVI signal across multiple time scales for each outbreak. Scale-wise anomalies were manifested at a 20-day scale, and were found in four of the five sites, one to three weeks preceding outbreaks, suggesting that filovirus-caused disease outbreaks may be associated with either behavioural shifts in a vertebrate host or changes in viral population dynamics. More generally, wavelet analysis offers a powerful tool for identifying temporal correlates of disease transmission events.     

Life Histories, Salinity Zones, and Sublethal Contributions of Contaminants to Pelagic Fish Declines Illustrated with a Case Study of San Francisco Estuary, California, USA

Human effects on estuaries are often associated with major decreases in abundance of aquatic species. However, remediation priorities are difficult to identify when declines result from multiple stressors with interacting sublethal effects. The San Francisco Estuary offers a useful case study of the potential role of contaminants in declines of organisms because the waters of its delta chronically violate legal water quality standards; however, direct effects of contaminants on fish species are rarely observed. Lack of direct lethality in the field has prevented consensus that contaminants may be one of the major drivers of coincident but unexplained declines of fishes with differing life histories and habitats (anadromous, brackish, and freshwater). Our review of available evidence indicates that examining the effects of contaminants and other stressors on specific life stages in different seasons and salinity zones of the estuary is critical to identifying how several interacting stressors could contribute to a general syndrome of declines. Moreover, warming water temperatures of the magnitude projected by climate models increase metabolic rates of ectotherms, and can hasten elimination of some contaminants. However, for other pollutants, concurrent increases in respiratory rate or food intake result in higher doses per unit time without changes in the contaminant concentrations in the water. Food limitation and energetic costs of osmoregulating under altered salinities further limit the amount of energy available to fish; this energy must be redirected from growth and reproduction toward pollutant avoidance, enzymatic detoxification, or elimination. Because all of these processes require energy, bioenergetics methods are promising for evaluating effects of sublethal contaminants in the presence of other stressors, and for informing remediation. Predictive models that evaluate the direct and indirect effects of contaminants will be possible when data become available on energetic costs of exposure to contaminants given simultaneous exposure to non-contaminant stressors.     

The Effects of Salinity on Nitrogen Losses from an Oligohaline Estuarine Sediment

Benthic respiration, sediment–water nutrient fluxes, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were measured in the upper section of the Parker River Estuary from 1993 to 2006. This site experiences large changes in salinity over both short and long time scales. Sediment respiration ranged from 6 to 52 mmol m⁻² day⁻¹ and was largely controlled by temperature. Nutrient fluxes were dominated by ammonium fluxes, which ranged from a small uptake of −0.3 to an efflux of over 8.2 mmol N m⁻² day⁻¹. Ammonium fluxes were most highly correlated with salinity and laboratory experiments demonstrated that ammonium fluxes increased when salinity increased. The seasonal pattern of DNRA closely followed salinity. DNRA rates were extremely low in March, less than 0.1 mmol m⁻² day⁻¹, but increased to 2.0 mmol m⁻² day⁻¹ in August. In contrast, denitrification rates were inversely related to salinity, ranging from 1 mmol m⁻² day⁻¹ during the spring and fall to less than 0.2 mmol m⁻² day⁻¹ in late summer. Salinity appears to exert a major control on the nitrogen cycle at this site, and partially decouples sediment ammonium fluxes from organic matter decomposition.