Temporal estimates of genetic diversity in some Mytilus galloprovincialis populations impacted by the Prestige oil-spill

The sinking of the tanker Prestige in November 2002 off the coast of Galicia resulted in the release of about 60,000 tons of heavy oil. The oil-spill provoked a serious environmental impact in Spanish and French coasts, which biological consequences are still being assessed. In this study we address the temporal dynamics of genetic diversity in some mussel populations impacted by the oil-spill. Changes in genetic diversity can be measured in natural populations provided that serial samples are available from before (year 2000) and after (years 2003, 2005) the oil-spill. Analyses of seven microsatellites indicate a weak but significant increase of genetic variation after the spill. This phenomenon is interpreted herein in terms of a balance between a enhanced genome mutability on microsatellite variation and a low genetic drift due to toxicants and asphyxia although other stochastic phenomena cannot be ruled out. Per locus annotation showed that in spite of the allelic changes observed in the period 2000-2005, the final size of most allelic series remained quite alike to those of year 2000. Present genetic data suggest that the genotoxic impact of the Prestige spill did not compromise the genetic diversity of studied mussel populations, at least regarding the genetic markers analysed.     

Holocene sea-surface temperature variability in the Chilean fjord region

Here we provide three new Holocene (11–0 cal ka BP) alkenone-derived sea surface temperature (SST) records from the southernmost Chilean fjord region (50–53°S). SST estimates may be biased towards summer temperature in this region, as revealed by a large set of surface sediments. The Holocene records show consistently warmer than present-day SSTs except for the past ~ 0.6 cal ka BP. However, they do not exhibit an early Holocene temperature optimum as registered further north off Chile and in Antarctica. This may have resulted from a combination of factors including decreased inflow of warmer open marine waters due to lower sea-level stands, enhanced advection of colder and fresher inner fjord waters, and stronger westerly winds. During the mid-Holocene, pronounced short-term variations of up to 2.5°C and a cooling centered at ~ 5 cal ka BP, which coincides with the first Neoglacial glacier advance in the Southern Andes, are recorded. The latest Holocene is characterized by two pronounced cold events centered at ~ 0.6 and 0.25 cal ka BP, i.e., during the Little Ice Age. These cold events have lower amplitudes in the offshore records, suggesting an amplification of the SST signal in the inner fjords.     

Fractured bedrock and saprolite hydrogeologic controls on groundwater/surface-water interaction: a conceptual model (Australia)

Hydrologic conceptual models of groundwater/surface-water interaction in a saprolite-fractured bedrock geological setting often assume that the saprolite zone is hydraulically more active than the deeper bedrock system and ignore the contribution of deeper groundwater from the fractured bedrock aquifer. A hydraulic, hydrochemical, and tracer-based study was conducted at Scott Creek, Mount Lofty Ranges, South Australia, to explore the importance of both the deeper fractured bedrock aquifer system and the shallow saprolite layer on groundwater/surface-water interaction. The results of this study suggest that groundwater flow in the deeper fractured bedrock zone is highly dynamic and is an important groundwater flow pathway along the hillslope. Deep groundwater is therefore a contributing component in streamflow generation at Scott Creek. The findings of this study suggest that hydrologic conceptual models, which treat the saprolite-fractured bedrock interface as a no-flow boundary and do not consider the deeper fractured bedrock in hydrologic analyses, may be overly simplistic and inherently misleading in some groundwater/surface-water interaction analyses. The results emphasise the need to understand the relative importance of subsurface flow activity in both of these shallow saprolite and deeper bedrock compartments as a basis for developing reliable conceptual hydrologic models of these systems.     

Diurnal variation of atmospheric CO<Subscript>2</Subscript> concentration and δ<Superscript>13</Superscript>C in an urban atmosphere during winter—role of the Nocturnal Boundary Layer

The paper presents the importance of the Nocturnal Boundary Layer in driving the diurnal variability of the atmospheric CO₂ mixing ratio and the carbon isotope ratio at ground level from an urban station in India. Our observations are the first of their kind from this region. The atmospheric CO₂ mixing ratio and the carbon isotopic ratio were measured for both the morning (05:30–07:30 IST) and afternoon time (16:00–18:00 IST) air samples at 5 m above ground level in Bangalore city, Karnataka State (12° 58′ N, 77° 38′ E, masl = 920 m) for a 10 day period during the winter of 2008. We observed a change of ~7% the in CO₂ mixing ratio between the morning and afternoon time air samples. A stable isotope analysis of CO₂ from morning samples showed a depletion in the carbon isotope ratio by ~2‰ compared to the afternoon samples. Along with the ground-based measurement of air samples, data of radiosonde measurements were also obtained from the Indian Meteorological Department to identify the vertical atmospheric structure at different time in a day. We proposed the presence or absence of the NBL as a controlling factor for the observed variability in the mixing ratio as well as its isotopic composition. Here we used the Keeling model approach to find out the carbon isotope ratio for the local sources. The local sources have further been characterized as anthropogenic and biological respiration (in %) using a two-component mixing model. We also used a vertical mixing model based on the concept of the mixing of isotopically depleted (carbon isotope) “polluted air” (PA) with isotopically enriched “free atmospheric air” (FA) above. Using this modeling approach, the contribution of FA at ground level is being estimated for both the morning and afternoon time air samples.     

Sismique très haute résolution 3D : une nouvelle méthode d'imagerie des sols superficielsVery High Resolution 3D seismic: a new imaging tool for sub-bottom profiling

This note presents the first results of the development of a 3D Very High Resolution seismic method. Particular attention was paid to the design of an operational system to be in agreement with the expected goals in term of acquisition and processing. A set of three examples, collected in various geological environments, is presented. To cite this article: T. Marsset et al., C. R. Geoscience 334 (2002) 403–408.     

Detection of underground cavities by combining gravity,magnetic and ground penetrating radar surveys: a case study from the Zaragoza area,NE Spain

A geophysical survey routine is proposed to detect underground cavities and dolines; it is based on the sequential application of magnetic, low-frequency ground penetrating radar (GPR) and microgravity techniques. A case study near Zaragoza (Ebro valley, Spain) demonstrates the applicability of these methods. The strong contrast of magnetic and electromagnetic properties (and to a lesser scale, of density) between the doline filling and the surrounding stratified Tertiary and Quaternary rocks allows the shape of filled cavities to be clearly outlined by these methods.     

Late Holocene sea-surface temperature and precipitation variability in northern Patagonia, Chile (Jacaf Fjord, 44°S)

A high-resolution multi-proxy study including the elemental and isotopic composition of bulk organic matter, land plant-derived biomarkers, and alkenone-based sea-surface temperature (SST) from a marine sedimentary record obtained from the Jacaf Fjord in northern Chilean Patagonia (44°20′S) provided a detailed reconstruction of continental runoff, precipitation, and summer SST spanning the last 1750 yr. We observed two different regimes of climate variability in our record: a relatively dry/warm period before 900 cal yr BP (lower runoff and average SST 1°C warmer than present day) and a wet/cold period after 750 cal yr BP (higher runoff and average SST 1°C colder than present day). Relatively colder SSTs were found during 750–600 and 450–250 cal yr BP, where the latter period roughly corresponds to the interval defined for the Little Ice Age (LIA). Similar climatic swings have been observed previously in continental and marine archives of the last two millennia from central and southern Chile, suggesting a strong latitudinal sensitivity to changes in the Southern Westerly Winds, the main source of precipitation in southern Chile, and validating the regional nature of the LIA. Our results reveal the importance of the Chilean fjord system for recording climate changes of regional and global significance.     

Plankton community diversity from bacteria to copepods in bloom and non-bloom conditions in the Celtic Sea in spring

The plankton community composition comprising heterotrophic bacteria, pro-/eukaryotes, heterotrophic nanoflagellates, microzooplankton and mesozooplankton was assessed during the spring bloom and at non-bloom stations in the English Channel and Celtic Sea between 6 and 12 April 2002. Non-bloom sites were characterised by a dominance of pro-/eukaryotic phytoplankton <20 μm, higher abundance of heterotrophic nanoflagellates, microzooplankton standing stocks ranging between 60 and 380 mg C m⁻², lower mesozooplankton diversity and copepod abundance of between 760 and 2600 ind m⁻³. Within the bloom, the phytoplankton community was typically dominated by larger cells with low abundance of pro-/eukaryotes. Heterotrophic nanoflagellate cell bio-volume decreased leading to a reduction in biomass whereas microzooplankton biomass increased (360–1500 mg C m⁻²) due to an increase in cell bio-volume and copepod abundance ranged between 1400 and 3800 ind m⁻³. Mesozooplankton diversity increased with an increase in productivity. Relationships between the plankton community and environmental data were examined using multivariate statistics and these highlighted significant differences in the abiotic variables, the pro-/eukaryotic phytoplankton communities, heterotrophic nanoflagellate, microzooplankton and total zooplankton communities between the bloom and non-bloom sites. The variables which best described variation in the microzooplankton community were temperature and silicate. The spatial variation in zooplankton diversity was best explained by temperature. This study provides an insight into the changes that occur between trophic levels within the plankton in response to the spring bloom in this area.     

A story of “communities”: boundaries,geographical composition and social coherence in a forest conservation project,Northern Cambodia

Explicit notions of “communities”, as key actors in conservation and development projects across the Global South, are common. Narratives about “indigenous people” or “forest-dependent communities” in forest conservation programmes prevail, portraying a picture of “communities” as homogeneous and harmonious entities. In this study, we unfold “communities” as a construct with an empirical example of a community-based forest protection project, Northern Cambodia. Based on qualitative interviews, field observations and document analysis, we examine the “community” construct in terms of establishment of boundaries, geographical composition and social coherence. We not only find that the establishment of forest “community” boundaries are dominated by powerful external actors rather than the “community members” themselves, but that the spatial composition of “communities” is complex, and affects the ability of local people to benefit from the project. We also find that the studied “communities” show low levels of social coherence and mainly consist of migrant farmers, as opposed to common policy narratives. Taking these inconsistencies into account, we discuss implications of constructing “communities” for the success of forest conservation projects, and argue in favour of more discursive and political analyses to better understand, acknowledge and adapt to existing and changing conditions in present and prospective project locations.