Influence of Environmental Variables and Fishing Pressure on Bivalve Fisheries in an Inshore Lagoon and Adjacent Nearshore Coastal Area

Climate changes affect marine ecosystems and the survival, growth, reproduction and distribution of species, including those targeted by commercial fisheries. The impact of climate change has been reported for many fish species, but studies focusing on the effects of climate on bivalve resources are lacking. In Portugal, the harvesting of bivalves is an old and artisanal activity, of special importance along the Algarve coast (South of Portugal). This study aims to evaluate the influence of climatic, environmental and fisheries factors on the landings of intertidal coastal lagoon and coastal bivalve species (subtidal nearshore species). The environmental and fisheries parameters considered to affect the landings of bivalves in the eastern Algarve were: fishing effort (number of fishing events), sea surface temperature, North Atlantic Oscillation (NAO) index, upwelling index, wind magnitude and direction and river discharges. Analysis of time series data using min/max autocorrelation factor analysis and dynamic factor analysis showed that, for most species, fishing effort was positively related with landings per unit effort trends in the following year. Lagoon bivalve species (Cerastoderma edule and Ruditapes decussatus) responded to different environmental variables than the coastal bivalve species (Chamelea gallina, Pharus legumen, Donax spp. and Spisula solida). Upwelling index had a significant effect on the lagoon bivalves while the NAO index, wind magnitude and direction, and river discharges only affected the coastal species. This study highlighted the need to adapt fishing effort regimes, while considering the background effects of environmental variability, in order to improve fisheries management.     

Petrology,phase equilibria modelling,noble gas chronology and thermal constraints of the El Pozo L5 meteorite

We present the results of physical properties, petrography, bulk chemistry, mineral compositions, phase relations modelling and Noble gases study of the meteorite El Pozo. The petrography and mineral compositions indicate that the meteorite is an L5 chondrite with a low shock stage of S2-S3. Heterogenous weathering was preferentially along shock structures. Thermobarometric calculations indicate thermal equilibrium conditions between 768?°C and 925?°C at ～4 to 6?kb, which are substantially consistent with the petrological metamorphism type 5. A pseudosection phase diagram is relatively consistent with the mineral assemblage observed and PT conditions calculated. Temperature vs. fO₂ diagram shows that plagioclase compositional stability is very sensitive to Tschermack substitution in orthopyroxene, clinopyroxene and X_An plagioclase during the high temperature metamorphic process. Based on noble gases He, Ne, Ar and K contents a cosmogenic exposure age CRE of 1.9?Myr was calculated. The ²¹Ne would be totally cosmogenic, with no primordial Ne. The ²¹Ne/²²Ne value (0.97) is higher than solar value. According to the cosmogenic Ne content, we argue that El Pozo chondrite originally had a pre-atmospheric mass of 9–10?kg, which would have been produced by a later collision after the recognized collision of the L-chondrite parent body ～470?Ma ago.     

Radiological and geochemical characteristics of an ultramafic massif (NE Portugal) regarding the site aptness to host a near surface repository for low and intermediate level radwaste

The search for suitable sites to install near-surface repositories for low to intermediate level radioactive wastes has increased in the recent years, reflecting both the continuous rise in radioactive materials applications by the society and the increasing awareness of public perception regarding radwaste management. International recommendations towards the application of higher safety standards to low and intermediate level waste disposal sites being developed by the International Atomic Energy Agency (IAEA), and the European Commission decision that each Member State must safely dispose its own radwaste in its territory, according to national radwaste management plans, has leading to new soundly scientific studies. In Portugal, possible locations for that purpose are under study since 2006, following the pre-requisites indicated by IAEA. One of these sites overlaps a significant portion of an ultramafic massif, corresponding to an allochthonous and metamorphosed ophiolite complex. In the surveyed area of this massif, the prevailing rock type consists of (serpentinised) peridotites, occasionally containing irregular bodies of (amphibolitised) gabbros, over which an irregular/ill-developed regolith exists. The activities of ⁴⁰K, ¹³⁷Cs, ²¹⁰Pb, ²²⁶Ra and ²³²Th measured in samples representing three consecutive levels of the regolith upper portion in 13 stations confirm the heterogeneity put in evidence through in situ γ-ray surveys previously performed. The available dataset also demonstrates that radionuclide contents decrease prominently with depth, becoming closer to the bedrock values (up to ca. 41 Bq kg^?1 for ⁴⁰K in flaser-gabbros and near zero for all the remaining cases) but never reaching them. Therefore, the low/moderate radionuclide activity in the regolith upper portion reflect the contribution of sources that are independent of the lithological background; i.e. they indicate external and miscellaneous contributions to the “soil”-forming components, most of them coming from (dry or wet) atmospheric deposition. The chemical composition of the (serpentinised) peridotites and (amphibolitised) gabbros in the surveyed area, as well as their alteration products included in regolith, is homogeneous enough to be used as a faithful reference in monitoring studies of any kind. In addition, the significant ¹³⁷Cs activities measured in some top “soil” samples (up to 92 Bq kg^?1) strongly suggest that there are mineralogical specificities of the peridotite-derived regolith able to fix that radionuclide. This particular feature reinforces the existing criteria that favour the peridotites of Morais as a suitable host for a near surface repository of low to intermediate level radwaste.     

Hydrological and geomorphological criteria to evaluate the dispersion risk of waste sludge generated by the Aznalcollar mine spill (SW Spain)

Following the Aznalcóllar pyrite mine disaster (Seville, Spain) which caused the spilling of some 4.5?hm³ of acid water, the floodplains of the rivers Agrio and Guadiamar were rapidly cleaned of waste sludge. However, despite the efficiency of cleaning activities, there is still evidence of a fine superficial layer of sludge and some soil contamination, with the consequent risk of remobilisation of the pollutants by water erosion. There is much concern that these contaminated sediments may affect the precious ecosystems of the Doñana National Park and the Guadalquivir marshlands. This report describes the evaluation of the risk of mobilisation of the waste sludge through (1) detailed geomorphological analysis, indicating potential areas of erosion-sedimentation on the floodplains of the rivers Agrio and Guadiamar, and predicted dynamics of the waste sludge, and (2) evaluation of the potential dispersion of the waste sludge provoked by future flood events, including hydraulic calculations to model channel flow and the analysis of the texture of the sludge to obtain critical transport and sedimentation values. Findings suggest that the waste sludge is likely to be transported and deposited within the Doñana National Park during future flood events.     

Deadly oasis:Recurrent annihilation of Cretaceous desert bryophyte colonies;the role of solar,climate and lithospheric forcing

Many oases(wet interdunes)are sedimentary systems characterized by high-frequency water-level oscillations,marked changes in salinity and intense biological activity at their margins.They are considered to be one of the most challenging environments on Earth for ecosystem development.These dynamic,depositional settings are usually unfavourable for fossilization and subsequent preservation of vegetal remains.This paper describes bryophyte(liverwort)assemblages occurring in three successive horizons interpreted to represent(i)recurrent early successional phases of biological soil crust colonization of wet interdune margins or(ii)exceptional preservation of floating or riparian liverworts in oasis pond waters associated with a progressive fall of the interdune water level.The record of in situ colonization surfaces characterized by delicate(e.g.lignin-free)three-dimensional structures represents an exceptional type of preservation herein associated with a rapid variation in phreatic interdune water level and the subsequent establishment of anoxic and reducing conditions.The occurrence of exceptionally preserved liverwort colonies coincides with the sedimentary record of,at least,three seismite levels in the oasis.Data gathered from the site suggests that the water table of the oasis was controlled by a combination of(i)a positive creation of accommodation space due to subsidence associated with movement on syn-sedimentary extensional faults,and(ii)the rise and fall of the oasis water table controlled by the oscillations of the groundwater system due to orbital changes which appear to drive the variability of the climate system.Rising groundwater levels flooded the oasis soil crusts and lead to the exceptional recurrent preservation of liverwort colonies at the oasis margins.Alternatively,considering the hypothesis of floating or riparian liverworts in the oasis pond waters,the fall in the level of the oasis water table placed the floating liverworts in contact with the oasis bottom sediments.This fall in the level of the oasis water table could indicate a cessation of accommodation space by syn-sedimentary extensional faults and/or a regional lowering of the groundwater system level associated with drought periods.Preliminary results indicate that oasis lamination between liverwort colonies records decadal and sub-decadal cyclicity,related with 11-year Schwabe sunspot and sub-decadal NAO cyclicities,conferring for every sedimentary cycle between liverwort colonies a duration of approximately 200 years,that otherwise matches the expected recurrence period for the De Vries cycle of solar activity.     

Groundwater vulnerability assessment in coastal plain of Rio Grande do Sul State,Brazil, using drastic and adsorption capacity of soils

Groundwater vulnerability assessment to delineate areas that are more susceptible to contamination has become an important element for resource management and land use planning. The objective of this work was to integrate hydrogeologic data in a geographic information system (GIS) for phreatic groundwater vulnerability assessment of a pilot area from the Coastal Plain of the Rio Grande do Sul State, Brazil, using the DRASTIC method and adsorption capacity of soils. The studied ions were copper, lead, sulfate and phosphate. Using the original DRASTIC method, the vulnerability presented high values, mainly due to the texture of the sediments and the low depths of waters, which favor the accessibility of the contaminants to the groundwaters. DRASTIC with adsorption capacity of soils showed specifics results for each studied ion. Groundwater vulnerability to metals in relationship to anions was lower. These results show that the original DRASTIC method represents better contaminants with high mobility. An erratum to this article can be found at     

Mineral Weathering in a Semiarid Mountain River: Its assessment through PHREEQC inverse modeling

By means of PHREEQC inverse modeling, we have simulated the weathering reactions in Los Reartes River, a mountainous (2400–670 m a.s.l.) drainage basin from the Sierras Pampeanas of Córdoba, Argentina, analyzing the effect of lithology, relief, and climate. The steep upper half of the basin (slopes > 20) is occupied by exposed granite; the remaining area is mostly metamorphic, with cropping out gneisses and progressively decreasing slopes (< 6). Climate is semihumid to semiarid; rainfall mainly occurs in summer and decreases with decreasing height. PHREEQC inverse models developed using water chemical data showed that (a) oligoclase was the major supplier of solutes, while the main precipitated phase was kaolinite in the granite domain; (b) muscovite is the chief supplier of solutes and illite is the main precipitated phase in the gneissic realm; (c) the steeper portions of the metamorphic reach are less crucial in supplying solutes than the lower ones, thus highlighting the importance of the water residence time in the kinetics of dissolution; (d) in the driest time of the year (winter, 20 mm/month) we registered the highest production of dissolved and precipitated phases; fluxes (mmol/month), however, are higher at the end of the rainy season; (e) CO₂ consumption is important all along the Los Reartes drainage basin and, in terms of mmol/kg H₂O, the lowermost portion of the basin is the most significant supplier; (f) CO₂ accounts for over 50 of all the species involved in the weathering reactions occurring at the Los Reartes drainage basin.     

Changes in the Diffuse CO2 Emission and Relation to Seismic Activity in and around El Hierro, Canary Islands

Significant changes in the diffuse emission of carbon dioxide were recorded in a geochemical station located at El Hierro, Canary Islands, before the occurrence of several seismic events during 2004. Two precursory CO₂ efflux increases started thirteen and nine days before two seismic events of magnitude 2.3 and 1.7, which took place near El Hierro Island, Canary Islands, on March 23 and April 15, reaching a maximun value of 51.1 and 46.2 g m⁻² d⁻¹, respectively, five and eight days before the two seismic events. Other similar increases started thirteen and five days before the occurrence of two seismic events of magnitude 1.3 and 1.5 which took place on October 15 and 21 respectively, reaching the maximum values four and one day before the earthquakes. These changes were not related to variations in atmospheric or soil parameters. The Material Failure Forecast Method (FFM), which analyzes the rate of precursory phenomena, was successfully applied to forecast the first seismic event that took place in El Hierro Island in 2004.