Geology and tectono‐metamorphic evolution of the Himalayan metamorphic core: insights from the Mugu Karnali transect,Western Nepal (Central Himalaya)

New structural and tectono‐metamorphic data are presented from a geological transect along the Mugu Karnali valley, in Western Nepal (Central Himalaya), where an almost continuous cross‐section from the Lesser Himalaya Sequence to the Everest Series through the medium‐high‐grade Greater Himalayan Sequence (GHS) is exposed. Detailed meso‐ and micro‐structural analyses were carried out along the transect. Pressure (P)–temperature (T) conditions and P–T–deformation paths for samples from different structural units were derived by calculating pseudosections in the MnNKCFMASHT system. Systematic increase of P–T conditions, from ~0.75 GPa to 560 °C up to ≥1.0 GPa–750 °C, has been detected starting from the garnet zone up to the K‐feldspar + aluminosilicate zone. Our investigation reveals how these units are characterized by different P–T evolutions and well‐developed tectonic boundaries. Integrating our meso‐ and micro‐structural data with those of metamorphism and geochronology, a diachronism in deformation and metamorphism can be highlighted along the transect, where different crustal slices were underthrust, metamorphosed and exhumed at different times. The GHS is not a single tectonic unit, but it is composed of (at least) three different crustal slices, in agreement with a model of in‐sequence shearing by accretion of material from the Indian plate, where coeval activity of basal thrusting at the bottom with normal shearing at the top of the GHS is not strictly required for its exhumation.     

Managing coastal zone fisheries: A Mediterranean case study

Coastal fisheries are complex ecological and social systems, evolving in time with a shift from commercial towards recreational effort. We describe the coastal fisheries of Mallorca (W Mediterranean) and the management policies implemented to show the challenges faced at regional level to handle the different management tools used to conserve biodiversity and the social fabric in the coastal zone. Our example provides evidence of the complexity of fishing rights and how they can be adapted into practical fisheries management by combining fishing rights, open access recreational fishery, community-based management and biodiversity conservation.     

Sustainability implications of honouring the Code of Conduct for Responsible Fisheries

The Code of Conduct for Responsible Fisheries developed in 1995 by the Food and Agriculture Organization (FAO) of the United Nations includes a set of recommendations for reducing the negative impacts of fishing activities on marine ecosystems. The Code is widely believed to be an important tool for fisheries management and, although the Code is voluntary, all stakeholders concerned with the management and development of fisheries, and conservation of fishery resources, are actively encouraged to implement it. Previous analysis at global scale showed widespread low compliance with the Code of Conduct that may be partly due to a lack of empirical support for the overall ecological benefits of adhering to the Code. Here we evaluated these ecological effects by comparing compliance with the Code to changes in five ecological indicators that quantify the ecosystem effects of fishing. We used the loss in production index and the related probability of sustainable fishing index, the mean trophic level of the catch, total catches, and the primary production required to sustain the catch. We also tested if regional differences and development status of countries influenced the results of ecological indicators. Results indicate that countries with higher levels of compliance with the FAO Code of Conduct in 2008 experienced a decrease in the Loss in Production index and an increase in fisheries sustainability from the 1990s to 2000s. We conclude that better implementation of the Code of Conduct may have had overall positive ecological effects with time. A significant decrease in total catch and primary production required with higher compliance was also observed. While a significant increase in ecosystem sustainability was observed after a decade of adoption of the Code at high levels of compliance, further ecosystem degradation had taken place where compliance with the Code was below a given threshold (4, from a ranking of 0–10). Therefore, since compliance with the Code is still low or very low worldwide, these results may encourage individual countries to adopt well-established fishery management measures in order to increase the ecological sustainability of marine resources.     

A Laboratory Experimental Study of the Hydromechanical Behavior of Boom Clay

This paper reports some results of a large experimental program on Boom Clay conducted in Grenoble in the framework of the European project SELFRAC. The program included isotropic compression up to relatively high stress, drained triaxial compression tests at different cell pressures, as well as permeability measurements under isotropic and deviatoric stress. Local measurement of axial and radial displacements allowed the detection of strain localization during deviatoric loading. The permeability of Boom Clay is found to depend on the mean effective stress. The response of Boom Clay during deviatoric loading appears to be strongly affected by the swelling experienced during the isotropic stage preceding triaxial compression. The rate of swelling decreases with isotropic stress. The longer the swelling before shear, more the response under shear becomes ductile and the lower the initial stiffness. Permeability depends on the mean effective stress and it is found to decrease of about two orders of magnitude when the mean stress increases from 1 to 32 MPa. Permeability during shear loading is essentially constant and does not seem to be affected by strain localization. These results are complemented by a few observations obtained using X-ray microtomography in the framework of the more recent European project TIMODAZ. These findings illustrate the impact of pre-existing inclusions and fissures on specimen deformation upon deviatoric loading in the laboratory.     

Estimate of the debris-flow entrainment using field and topographical data

The entrainment of material is a common process in debris-flow behaviour and can strongly increase its total volume. However, due to the complex nature of the process, the exact mechanisms of entrainment have not yet been solved. We analysed geomorphological and topographical data collected in 110 reaches of 17 granular debris flows occurred in the Pyrenees and the European Alps. Four governing factors (sediment availability, channel-bed slope, channel cross section shape and upstream-contributing area) were selected and defined for all the 110 reaches. One dataset of the resulting database was used to develop two models to estimate the erosion rates based on the governing factors: a formula derived from multiple linear regression (MLR) analysis and a decision tree (DT) obtained from J48 algorithm. The models obtained using these learning techniques were validated in another independent dataset. In this validation set, the DT model revealed better results. The models were also implemented in a torrent (test set), where the total debris-flow volume was known and two empirical methods (available in literature) were applied. This test revealed that both MLR and DT predict more accurately the final volume of the event than the empirical equations for volume prediction. Finally, a general DT was proposed, which includes three governing factors: sediment availability, channel-bed slope and channel cross section shape. This DT may be applied to other regions after adapting it regarding site-specific characteristics.     

Geological characterization of the Prestige sinking area

The tanker Prestige sank off NW Iberia on the 19th November 2002. The stern and bow of the Prestige wreck are located on the southwestern edge of the Galicia Bank, at 3565 m and 3830 m water depths, respectively. This bank is a structural high controlled by major faults with predominant N-S, NNE-SSW, and NNW-SEE trends. It is characterized by moderate to low seismic activity. The faults have controlled the local depositional architecture, deforming, fracturing, relocating and distributing sediments since the Valangian (early Cretaceous). The Prestige sinking area corresponds to an asymmetric half-graben structure with a N-S trend, which conditions the present-day morphology. The faulted flank outcrops and its activity and erosion have favoured the occurrence of mass-movements (slumps, slump debris, mass-flows and turbidity currents), building valleys and depositional lobes. Nearsurface sediments comprise mostly terrigenous and biogenous turbiditic muds and sands with a minor presence of hemipelagic muds, except on the fault scarp where pelagites predominate. Potential geological hazards resulting from tectonic and sedimentary processes affect almost the entire Prestige sinking area.     

Distribution and Pathogenicity of the Protist <Emphasis Type="Italic">Labyrinthula</Emphasis> sp. in western Mediterranean Seagrass Meadows

The presence of the pathogenic protist Labyrinthula sp., the causative agent of seagrass wasting disease and mass mortality events, was assessed in 18 seagrass meadows in the Balearic region (western Mediterranean). This protist was found in 70% of seagrass meadows investigated and in all seagrass species present in the region (i.e., Posidonia oceanica, Cymodocea nodosa, and Zostera noltii). Labyrinthula spp. cultures isolated from seven P. oceanica and one Thalassia testudinum meadows were used as inocula to perform cross-infection experiments in order to test seagrass vulnerability to Labyrinthula spp. infection. These isolates produced lesions on P. oceanica and other seagrass species (Zostera marina, Z. noltii, and C. nodosa). P. oceanica and Z. noltii, both species autochthonous to the Mediterranean Sea, were the seagrasses most vulnerable to infection by the tested isolates. One of the P. oceanica isolates of Labyrinthula sp. also infected the Atlantic seagrass Z. marina, and all of the Mediterranean seagrasses were infected by Labyrinthula sp. isolated from the T. testudinum, native to the Caribbean and Gulf of Mexico. This work confirms that Labyrinthula sp. is commonly found on seagrasses of the Mediterranean Sea and demonstrates that Labyrinthula sp. can infect seagrasses in different genera, in contrast to previous studies where Labyrinthula sp. was considered to be genus-specific. This finding points out the broadly pathogenic nature of some Labyrinthula sp. isolates. Finally, this work identifies Labyrinthula sp. as a possible detrimental agent for P. oceanica.