How Well Do Restored Intertidal Oyster Reefs Support Key Biogeochemical Properties in a Coastal Lagoon?

The restoration of dead/degraded oyster reefs is increasingly pursued worldwide to reestablish harvestable populations or renew ecosystem services. Evidence suggests that oysters can improve water quality, but less is known about the role of associated benthic sediments in promoting biogeochemical processes, such as nutrient cycling and burial. There is also limited understanding of if, or how long postrestoration, a site functions like a natural reef. This study investigated key biogeochemical properties (e.g., physiochemical properties, nutrient pools, microbial community size and activity) in the sediments of dead reefs; 1-, 4-, and 7-year-old restored reefs; and natural reference reefs of the eastern oyster, Crassostrea virginica, in Mosquito Lagoon (FL, USA). Results indicated that most of the measured biogeochemical properties (dissolved organic carbon (C), NH₄ ⁺, total C, total nitrogen (N), and the activity of major extracellular enzymes involved in C, N, and phosphorus (P) cycling) increased significantly by 1-year postrestoration, relative to dead reefs, and then remained fairly constant as the reefs continued to age. Few differences were observed in biogeochemical properties between restored reefs of any age (1 to 7 years) and natural reference reefs. Variability among reefs of the same treatment category was often correlated with differences in the number of live oysters, reef thickness, and/or the availability of C and N in the sediments. Overall, this study demonstrates the role of live intertidal oyster reefs as biogeochemical hot spots for nutrient cycling and burial and the rapidity (within 1 year) with which biogeochemical properties can be reestablished following successful restoration.     

Geochemistry of Santo Antônio da Barra Kamafugites, Goiás, Brazil

This work focuses on the kamafugites from Santo Antônio da Barra, Minas–Goiás Alkaline Province. These rocks contain olivine, clinopyroxene, titanomagnetite, perovskite, leucite (pseudomorphs), kalsilite, nepheline, and phlogopite.The rocks investigated are ultrabasic, with high contents of CaO, FeO, and TiO₂, high to moderate contents of Al₂O₃, alkalis, and P₂O₅, and low contents of MgO. The alkaline characteristic of the rocks is reflected in TiO₂, K₂O, and Na₂O contents and in the frequent presence of normative nepheline and leucite. K₂O contents are not primary since most of the leucite was replaced by analcime.The negative K anomaly verified in the extended incompatible element distribution diagram for kamafugites seems to be mainly related to alteration. Kamafugites are characterized by a marked enrichment in incompatible and large ion lithophile elements together with other typical compatible elements.The Santo Antônio da Barra kamafugites are less enriched in titanium, niobium, zirconium, and REE than the Mata da Corda and most of the Toro-Ankole ones. San Venanzo–Cupaello rocks have much lower titanium contents.     

Chromian spinels in metamorphosed ultramafic rocks from Mangabal I and II complexes, Goiás, Brazil

Summary Chromian spinel occurs in feldspathic metaperidotites and feldspathic metaharzburgites, respectively, at Mangabal I and II mafic-ultramafic layered complexes, Brazil. Both complexes were metamorphosed (700-750°C and 6-7 Kbars) under variable P_{H 2}O conditions. Wherever P_{H 2}O = P_tot an almost complete metamorphic recrystallization occurred, but where P_{H 2}O < P_tot relict igneous cumulate textures are well preserved. Chromian spinel occurs as opaque grains included in cumulus olivine and as brown translucent crystals enclosed by intercumulus orthopyroxene, clinopyroxene, and plagioclase. Subsolidus reactions resulted in exsolution of opaque spinel into two phases: a Fe⁺²Fe ₂ ⁺³ -rich and a MgAl₂-rich one. Fe₂TiO₄-rich lamellae and patches may also occur. Coronas developed between olivine and plagioclase including orthopyroxene, pargasite and MgAl₂-rich green spinel. Whenever complete metamorphic reequilibration occurred (P_{H 2}O = Ptot) the brown and green spinels reacted with silicate phase to form clinochlore, leaving the Fe+2Fe ₂ ⁺³ -rich spinel phase, magnetite.

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Chromspinelle in metamorphen, ultramafischen Gesteinen der Mangabal I und II Komplexe, Goiás, Brasilien

Zusammenfassung Chromspinell kommt in feldspatführenden Metaperidotiten und Metaharzburgiten in den geschichteten mafisch-ultramafischen Komplexen in Mangabal I and II, Brasilien, vor. Beide Komplexe wurden unter variablem P_{H 2}O metamorphisiert (700–750°C, 6–7 Kbar). Während unter fluidreichen Bedingungen (P_{H 2}(O = P_tot) eine beinahe vollständige metamorphe Rekristallisation erfolgte, bleiben unter P_{H 2}O < P_tot reliktische magmatische Kumulustexturen erhalten. Chromspinell tritt in opaken körnern in Kumulus-Olivin und als braune, durchscheinende Körner, eingeschlossen in den Interkumulusmineralen Orthopyroxen, Klinopyroxen und Plagioklas, auf. Subsolidusreaktionen resultierten in der Entmischung von opakem Spinell in eine Fe²⁺ Fe ₂ ³⁺ -und eine MgAl₂-reiche Phase. Fe₂TiO₄-reiche Lamellen und Nester treten außerdem auf. Koronas zwischen Olivin und Plagioklas bestehen aus Orthopyroxen, Pargasit und grünem MgAl₂-reichem Spinell. Dort wo ein vollständige metamorphe Reequilibration (P_{H 2}O = P_tot) erfolgte, reagierte brauner und grüner Spinell mit Silikaten und bildete clinochlor, unter Zurücklassung von Fe²⁺Fe ₂ ³⁺ -reichem Spinell, dem Magnetit.

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With 8 Figures     

U–Pb perovskite ages for brazilian kamafugitic rocks: further support for a temporal link to a mantle plume hotspot track

We present the results of a U–Pb perovskite age study of kamafugites from Mata da Corda (MC) and Santo Antônio da Barra (SAB), Minas-Goiás alkaline province, Brazil. Perovskite crystals were separated from MC mafurites, ugandites, and cognate pyroxenites, as well as from SAB melilite mafurite. The range of ages of Brazilian kamafugitic samples is 15 Ma. The ²⁰⁶Pb/²³⁸U perovskite ages generally cluster into three age groupings: 88–90, 80–81, and 75–76 Ma. The two younger periods of kamafugitic magmatism occur in the MC area, whereas the older samples are from the SAB area. These new age results provide the first robust evidence of a progressive eastward younging of mafic alkaline magmatism, most likely related to a mantle plume hotspot track.     

Environmental influences on soil CO2 degassing at Furnas and Fogo volcanoes (São Miguel Island,Azores archipelago)

Since October 2001, four soil CO₂ flux stations were installed in the island of São Miguel (Azores archipelago), at Fogo and Furnas quiescent central volcanoes. These stations perform measurements by the accumulation chamber method and, as the gas flux may be influenced by external variables, the stations are equipped with several meteorological sensors. Multivariate regression analysis applied to the large datasets obtained allowed observing that the meteorological variables may influence the soil CO₂ flux oscillations from 18% to 50.5% at the different monitoring sites. Additionally, it was observed that meteorological variables (mainly soil water content, barometric pressure, wind speed and rainfall) play a different role in the control of the gas flux, depending on the selected monitoring site and may cause significant short-term (spike-like) fluctuations. These divergences may be potentially explained by the porosity and hydraulic conductivity of the soils, topographic effects, drainage area and different exposure of the monitoring sites to the weather conditions. Seasonal effects are responsible for long-term oscillations on the gas flux.     

Analysis of Effective Efficiency in decision making for irrigation interventions

Multiple stresses are putting great pressure on water resources systems. Population growth, climate change, prosperity, energy production, food crisis, and water governance are among the factors straining water resources. Decision makers from rich to poor countries and from commercial to non-governmental organisations are struggling to devise schemes to adapt to these stressed water conditions. Better efficiency for water resources systems, and particularly irrigation systems, is recommended as one of the most important responses to climate change, unsustainable development, and water shortage. However, using certain efficiencies such as Classical Efficiency caused systems not to perform according to decision makers?? objectives. Effective Efficiency is a robust composite indicator that includes in its formulation both a flow weight, taking into account the leaching fraction, and reuse of return flows. Classical Efficiency is defined as the percentage of the diversion consumed beneficially, such as by crop evapotranspiration. Effective Efficiency, on the other hand, is defined as the ratio of beneficial consumptive use to total consumption, expressed as a percentage. In this paper, a normalised and non-dimensional form of Effective Efficiency is developed and necessary constraints for its successful application are explained. These constraints express water balance, flow weights and their thresholds, water reuse, and total consumptive use. Basic guidelines are proposed for better decision making in determining possible interventions for improving Effective Efficiency. This is done by analysing its domain through analytical and graphical methods. Three real cases are considered, namely, Imperial Irrigation District and Grand Valley irrigation systems in the United States and Nile Valley in upper Egypt. Three-dimensional sensitivity analysis is performed on Effective Efficiency and its variables using the three cases. This leads to an examination of the validity of the analysis and to suggestions for better intervention options. Meanwhile, it is also shown why Classical Efficiency should be used with care.     

Crustal seismic velocity structure near Faial and Pico Islands (AZORES), from local earthquake tomography

The Azores archipelago (Portugal) is located on an oceanic plateau, in a geodynamic environment prone to intense seismic and volcanic activity. In order to investigate the crustal structure in this region, we have conducted a local earthquake tomography study in the area of the islands of Faial, Pico and S. Jorge using data recorded in July 1998. The July 9th 1998 earthquake, near Faial Island, triggered an aftershock sequence of thousands of events that lasted for several months and were recorded by a total of 14 stations located on the three islands surrounding the epicentral area. In the upper crustal layers, consistency is seen between the tomographic results and the islands' surface volcanic units. Beneath the Faial central volcano a low Vp (< 6.0 km/s) anomaly roughly located at 3–7 km depth, suggests a connection to the plumbing system, possibly the presence of a magma chamber. In NE Faial, a high Vp (> 6.3 km/s) body was found located at mid-lower crust, most likely an intrusion of gabbroic composition, that is bordered by the registered seismic activity; its shape suggesting a tectonic controlled mechanism. The relocated hypocenters, together with the overall analysis of the Tomographic model, suggest a tectonic segmentation of Faial Island. The crustal thickness under the islands volcanic buildings of the Faial–Pico area was estimated at around 14 km.     

Impact of the new common agricultural policy of the EU on the runoff production and soil moisture content in a Mediterranean agricultural system

Soil moisture variability and the depth of water stored in the arable layer of the soil are important topics in agricultural research and rangeland management. In this study, we use the distributed rainfall-runoff (DR2) model to perform a detailed mapping of topsoil moisture status (SMS) in a mountain Mediterranean catchment. This model, previously tested in the same study area against the Palmer Z-index, is run at monthly scale for the current scenario of land uses and under three scenarios that combine the land abandonment and the application of the new common agricultural policy (CAP) of the European Union. Under the current conditions, runoff yield is scarce and presents a high spatial variability when monthly rainfall intensity and depth are low, and infiltration processes mainly lead to water storage in the soil. When rainfall intensity is high, runoff accumulation along the hillslopes controls the depth of available water in the soil, and SMS is more homogeneous. On average, scrublands and pasture have the wettest values, crops of winter cereal and abandoned fields have intermediate conditions, and areas of bare soil and forest have the driest conditions all the year around. The abandonment and no revegetation of the low productive fields located in steep areas and the collapse of their landscape linear elements (LLEs) produce not only an increase of 2.3 % of the overall SMS in the catchment in comparison with the current scenario but also an increment of the effective runoff that cross the cultivated areas of the lowlands and the runoff depth that reach the wetlands, increasing the soil erosion risk and compromising the conservation of the lakes. When the new green areas of the CAP are installed in the upper part of the fields of the lowlands and around the lakes, the runoff depth and thus siltation risk clearly decreases but also SMS decreases 1.7 and 1.1 % considering the current land uses and adding revegetation practices in the abandoned fields, respectively. Hence, a management scenario where: (1) abandoned fields are covered with a dense cover of shrubs, (2) the LLEs are preserved, (3) the green areas of the PAC are created, and (4) runoff harvesting practices are applied to partially compensate the water deficit, will help to preserve the humidity of the soil and will be of interest to keep the agricultural land use around the protected lakes of the study area.