Effects of the Ixtoc I blowout on heterotrophic bacteria

Heterotrophic and hydrocarbonoclastic bacteria were enumerated at the water surface and in sediment at 14 stations located in the Ixtoc I area. The distribution of heterotrophic bacteria in water and in sediment seems to be influenced by the river waters and the characteristics of sediments. The concentrations of hydrocarbonoclastic bacteria in sediments are low, and their relative percentage in regard to the heterotrophic bacteria, which are in general less than 1%, lead us to believe that the area studied was not affected by the Ixtoc I blowout.     

Inversion of magnetic anomalies and sea-floor spreading in the Cayman Trough

For some time, sea-floor spreading has been hypothesized for the Mid-Cayman Rise based on inferences from seismicity, heat flow, topography and plate geometry. Here we present magnetic anomaly inversions from which a reasonable record of sea-floor spreading emerges. We obtain total opening rates of 20 ± 2 mm/yr for 0–2.4 m.y. B.P. and 40 ± 2 mm/yr for 2.4–6.0 m.y. B.P. Data on the west flank extend the half-opening rate of 20 mm/yr back to 8.3 m.y. B.P. Spreading has been very nearly symmetric. These new observations place important constraints on plate tectonic reconstructions by defining the relative motion between the North American and Caribbean plates. They also shed some light on sea-floor spreading processes in which the spreading center is a secondary feature in the sense that it is over an order of magnitude shorter than the adjoining transform faults.     

Seasonal variability of primary production in a fjord ecosystem of the Chilean Patagonia: Implications for the transfer of carbon within pelagic food webs

We characterized the seasonal cycle of productivity in Reloncaví Fjord (41°30′S), Chilean Patagonia. Seasonal surveys that included measurements of gross primary production, community respiration, bacterioplankton secondary production, and sedimentation rates along the fjord were combined with continuous records of water-column temperature variability and wind forcing, as well as satellite-derived data on regional patterns of wind stress, sea surface temperatures, and surface chlorophyll concentrations. The hydrography and perhaps fjord productivity respond to the timing and intensity of wind forcing over a larger region. Seasonal changes in the direction and intensity of winds, along with a late-winter improvement in light conditions, may determine the timing of phytoplankton blooms and potentially modulate productivity cycles in the region.Depth-integrated gross primary production estimates were higher (0.4–3.8 g C m^?2 d^?1) in the productive season (October, February, and May), and lower (0.1–0.2 g C m^?2 d^?1) in the non-productive season (August). These seasonal changes were also reflected in community respiration and bacterioplankton production rates, which ranged, respectively, from 0.3 to 4.8 g C m^?2 d^?1 and 0.05 to 0.4 g C m^?2 d^?1 during the productive and non-productive seasons and from 0.05 to 0.6 g C m^?2 d^?1 and 0.05 to 0.2 g C m^?2 d^?1 during the same two periods. We found a strong, significant correlation between gross primary production and community respiration (Spearman, r=0.95; p<0.001; n=12), which suggests a high degree of coupling between the synthesis of organic matter and its usage by the planktonic community. Similarly, strong correlations were found between bacterioplankton secondary production and both gross primary production (Spearman, r=0.7, p<0.05, n=9) and community respiration (Spearman, r=0.8, p<0.05, n=9), indicating that bacterioplankton may be processing an important fraction (8–59%) of the organic matter produced by phytoplankton in Reloncaví Fjord. In winter, bacterial carbon utilization as a percentage of gross primary production was >100%, suggesting the use of allochthonous carbon sources by bacterioplankton when the levels of gross primary production are low. Low primary production rates were associated with a greater contribution of small cells to autotrophic biomass, highlighting the importance of small-sized plankton and bacteria for carbon cycling and fluxes during the less productive winter months. Fecal pellet sedimentation was minimal during this period, also suggesting that most of the locally produced organic carbon is recycled within the microbial loop. During the productive season, on the other hand, the area exhibited a great potential to export organic matter, be it to higher trophic levels or vertically towards the bottom.     

Desert networks: A conceptual model for the impact of scarce, variable and patchy resources

Social actors in arid regions must develop strategies to respond to available resources, which are scarce, variable, patchy and unpredictable relative to other regions. We explore our observations of relationships amongst people and organisations in Australian deserts using a stylised network model of the structure of social networks in arid systems. Results suggest that temporal resource variability drives increased network density, but with fewer strong ties; sparse populations drive a relatively higher proportion of strong ties, and that networks develop a hub configuration as resource endowments become more patchy spatially. These ideas highlight some issues that warrant improved understanding by actors seeking to enhance livelihoods and local resilience in these extreme environments.     

Reaching beyond famine relief: Planning a strategy for rehabilitation and development in Dar Fur Region,Western Sudan

This paper gives the actual scenario of the national and international activities during the famine disaster in Dar Fur Region, Sudan. The author gives the example of the Dar Fur Workshop to illustrate how international cooperation functions in such cases. He deals with the conflicting objectives of relief measures on the one hand and medium-term and long-term development objectives on the other. The author presents an insight into the work of foreign aid in the Sudan and the constraints with which it is confronted. He intentionally leaves judgement for the reader to make. The author was the Resident Representative of the United Nations Development Programme in the Sudan at the time the Dar Fur Strategy for Rehabilitation and Development was being prepared. The views expressed are his own except where otherwise indicated.     

Integration of a limit-equilibrium model into a landslide early warning system

Landslides are a significant hazard in many parts of the world and exhibit a high, and often underestimated, damage potential. Deploying landslide early warning systems is one risk management strategy that, amongst others, can be used to protect local communities. In geotechnical applications, slope stability models play an important role in predicting slope behaviour as a result of external influences; however, they are only rarely incorporated into landslide early warning systems. In this study, the physically based slope stability model CHASM (Combined Hydrology and Stability Model) was initially applied to a reactivated landslide in the Swabian Alb to assess stability conditions and was subsequently integrated into a prototype of a semi-automated landslide early warning system. The results of the CHASM application demonstrate that for several potential shear surfaces the Factor of Safety is relatively low, and subsequent rainfall events could cause instability. To integrate and automate CHASM within an early warning system, international geospatial standards were employed to ensure the interoperability of system components and the transferability of the implemented system as a whole. The CHASM algorithm is automatically run as a web processing service, utilising fixed, predetermined input data, and variable input data including hydrological monitoring data and quantitative rainfall forecasts. Once pre-defined modelling or monitoring thresholds are exceeded, a web notification service distributes SMS and email messages to relevant experts, who then determine whether to issue an early warning to local and regional stakeholders, as well as providing appropriate action advice. This study successfully demonstrated the potential of this new approach to landslide early warning. To move from demonstration to active issuance of early warnings demands the future acquisition of high-quality data on mechanical properties and distributed pore water pressure regimes.     

Petrological,geochemical and geochronological evidence for a Neoproterozoic ocean basin recorded in the Marlborough terrane of the northern New England Fold Belt

Petrological, geochemical and radiogenic isotopic data on ophiolitic‐type rocks from the Marlborough terrane, the largest (～700 km²) ultramafic‐mafic rock association in eastern Australia, argue strongly for a sea‐floor spreading centre origin. Chromium spinel from partially serpentinised mantle harzburgite record average Cr/(Cr + Al) = 0.4 with associated mafic rocks displaying depleted MORB‐like trace‐element characteristics. A Sm/Nd isochron defined by whole‐rock mafic samples yields a crystallisation age of 562 ± 22 Ma (2σ). These rocks are thus amongst the oldest rocks so far identified in the New England Fold Belt and suggest the presence of a late Neoproterozoic ocean basin to the east of the Tasman Line. The next oldest ultramafic rock association dated from the New England Fold Belt is ca530 Ma and is interpreted as backarc in origin. These data suggest that the New England Fold Belt may have developed on oceanic crust, following an oceanward migration of the subduction zone at ca540 Ma as recorded by deformation and metamorphism in the Anakie Inlier. Fragments of late Neoproterozoic oceanic lithosphere were accreted during progressive cratonisation of the east Australian margin.     

Stages on Journeys: Some Remarks about Human Geography andPsychotherapeutic Practice

This paper attempts to open up discussion about interconnectionsbetween psychotherapeutic practice and human geography. I offer brief “here and now” observations to introduce the importance of personal experience and interpersonal relationships. I then construct an autobiographical narrative to elaborate the themes of separation and connection. This frames my preliminary explorations of tensions and convergences between ideas flowing from psychotherapeutic practice and human geography. I conclude by stressing limits to knowledge.