El Niño Modoki connection to extremely-low streamflow of the Paranaíba River in Brazil

Extremely-low discharge events of the Paranaíba River basin during the austral summer season (December–February, DJF), are found to be associated with the Pacific sea surface temperature anomalies resembling the recently identified El Niño Modoki phenomenon. Extreme discharge events are identified based on their persistent flow for 7 days and more after taking retention time into consideration. Ninety percent of the extremely low discharge events during peak streamflow seasons of DJF, are found to occur during the El Niño Modoki years. A diagnostics study of atmospheric anomalies has shown a clear connection between the modified Walker circulation, associated with the El Niño Modoki, and the precipitation anomalies over the Paranaíba River basin. The climate variations have direct relationship with the rainfall. Streamflow variations are considered as the surrogates to rainfalls. Thus, El Niño Modoki phase is important component to understand and predict the streamflow variations in the Paranaíba River basin.     

Climate influences on water and sediment properties of Genovesa Crater Lake,Galápagos

Genovesa Crater Lake is a remote, hypersaline lake in the northern Galápagos archipelago that contains a finely laminated sediment record. This sediment record has the potential to provide a high-resolution history of past climate variability in the eastern tropical Pacific. Here we present modern climate, lake, and sediment observations from 2009 to 2012 to explore how local climate variability influences Genovesa Crater Lake and its sediments. Surface lake temperature is strongly linked to air temperature and is highly seasonal. Temperature stratification is strongest during the warm season, whereas temperature becomes more uniform through the water column in the cool season. Deeper and earlier mixing occurred during the 2010 La Niña, which subsequently delayed 2011 cool season mixing and maximum warm season surface temperatures in 2011 and 2012. Lake salinity changes are influenced by precipitation, evaporation and persistent seawater influx. The largest declines in subsurface salinity follow months after the rainy season, when temperatures cool and fresher surface water from the previous warm/wet season mixes into the subsurface. Between 2009 and 2012, more calcium carbonate precipitated during a period of higher salinity. The period of highest calcium carbonate abundance measured in sediment records that span the late nineteenth to twentieth century coincides with the failure of two consecutive rainy seasons in 1988 and 1989 as well as the coldest monthly sea surface temperature measured at Puerto Ayora in 1989. More calcium carbonate-rich laminae from AD 1550 ± 70 to 1675 ± 90 may indicate a greater frequency of prolonged droughts or cooler temperatures, although enhanced productivity may also modulate carbonate precipitation. More Ca-rich laminae in Genovesa coincide with dry conditions inferred from other Galápagos sediment proxies, as well as prolonged dry and cool conditions inferred from reconstructions of the Southern Oscillation Index and NINO3 sea surface temperatures.     

Organic and inorganic matter in Louisiana coastal waters: Vermilion, Atchafalaya, Terrebonne, Barataria, and Mississippi regions

Chromophoric dissolved organic matter (CDOM) spectral absorption, dissolved organic carbon (DOC) concentration, and the particulate fraction of inorganic (PIM) and organic matter (POM) were measured in Louisiana coastal waters at Vermilion, Atchafalaya, Terrebonne, Barataria, and Mississippi River locations, in 2007-2008. The range of CDOM was 0.092 m⁻¹ at Barataria in June 2008 to 11.225 m⁻¹ at Mississippi in February 2008. An indicator of organic matter quality was predicted by the spectral slope of absorption coefficients from 350 to 412 nm which was between 0.0087 m⁻¹ at Mississippi in May 2008 and 0.0261 m⁻¹ at Barataria in June 2008. CDOM was the dominant component of light attenuation at Terrebonne and Barataria. Detritus and CDOM were the primary components of light attenuation at Vermilion, Atchafalaya, and Mississippi. DOC ranged between 65 and 1235 μM. PIM ranged between 1.1 and 426.3 mg L⁻¹ and POM was between 0.3 and 49.6 mg L⁻¹.     

A re-appraisal of the stratigraphy and volcanology of the Cerro Galán volcanic system,NW Argentina

From detailed fieldwork and biotite ⁴⁰Ar/³⁹Ar dating correlated with paleomagnetic analyses of lithic clasts, we present a revision of the stratigraphy, areal extent and volume estimates of ignimbrites in the Cerro Galán volcanic complex. We find evidence for nine distinct outflow ignimbrites, including two newly identified ignimbrites in the Toconquis Group (the Pitas and Vega Ignimbrites). Toconquis Group Ignimbrites (~5.60–4.51 Ma biotite ages) have been discovered to the southwest and north of the caldera, increasing their spatial extents from previous estimates. Previously thought to be contemporaneous, we distinguish the Real Grande Ignimbrite (4.68 ± 0.07 Ma biotite age) from the Cueva Negra Ignimbrite (3.77 ± 0.08 Ma biotite age). The form and collapse processes of the Cerro Galán caldera are also reassessed. Based on re-interpretation of the margins of the caldera, we find evidence for a fault-bounded trapdoor collapse hinged along a regional N-S fault on the eastern side of the caldera and accommodated on a N-S fault on the western caldera margin. The collapsed area defines a roughly isosceles trapezoid shape elongated E-W and with maximum dimensions 27 × 16 km. The Cerro Galán Ignimbrite (CGI; 2.08 ± 0.02 Ma sanidine age) outflow sheet extends to 40 km in all directions from the inferred structural margins, with a maximum runout distance of ~80 km to the north of the caldera. New deposit volume estimates confirm an increase in eruptive volume through time, wherein the Toconquis Group Ignimbrites increase in volume from the ~10 km³ Lower Merihuaca Ignimbrite to a maximum of ~390 km³ (Dense Rock Equivalent; DRE) with the Real Grande Ignimbrite. The climactic CGI has a revised volume of ~630 km³ (DRE), approximately two thirds of the commonly quoted value.     

Contribution of glacier meltwater to streamflow in the Wind River Range,Wyoming, inferred via a Bayesian mixing model applied to isotopic measurements

The Wind River Range (WRR) of Wyoming has the largest concentration of alpine glaciers in the American Rockies and contributes to several major river systems in the western United States. Declines in the areal extent and volume of these glaciers are well documented, and eventual loss of alpine glaciers will reduce the amount of water available for agricultural and domestic use. The contribution of glacial melt to streamflow remains largely unquantified in Wyoming. We used isotope measurements and Bayesian modeling to estimate the fractional contribution of glacier meltwater to Dinwoody Creek (DC) in the WRR on bi‐weekly and seasonal (spring, summer, and fall) time scales over 2 years. In 2007 and 2008, we made temporally intensive measurements of the stable isotope composition of water from the DC watershed. Samples of the primary sources of streamflow (snowmelt, glacier melt, rain, and baseflow) were collected during field campaigns, and automated collection of stream samples occurred over the melt season. Isotope data (D and ¹⁸O) were analyzed within a hierarchical Bayesian framework that incorporated temporal and spatial correlations. Glacial melt contributed a significant proportion (～53–59%) to streamflow in a low‐flow year (2007) or when streamflow was low during a high‐flow year (2008). In 2008, a large and persistent snowpack contributed significantly (～0·42–51%) to streamflow in mid‐summer. The large contribution of glacial melt to streamflow suggests that the loss of glaciers may impact riparian ecosystems and human water supplies in the late summer and in years with low snowpack. Copyright © 2011 John Wiley & Sons, Ltd.     

An Environmental Threshold of Soil Test P and Degree of P Saturation of Brazilian Oxisols

To develop P management guidelines for poultry litter application in Oxisols of Brazil, the relationship between water soluble P (WSP), soil test P (STP), and degree of P saturation (DPS) needs to be established. The study examined this relationship in Oxisols of Brazil receiving poultry litter. Soils were analyzed for Mehlich‐1 P (M1‐P), WSP, P fractions, P sorption index (PSI), and P saturation based on Mehlich‐1 extractable P, Al, Fe (DPS_M1), and PSI (DPS_PSI). Surface water bodies in the catchment area were examined for inorganic and total P. All the surface water bodies in the catchment area of the sampled plots were highly enriched in inorganic and organic P. Enrichment of soil P fractions following poultry litter application followed the order HCl‐bound > NaOH‐bound > NaHCO₃‐bound fraction. M1‐P was correlated to labile (NaHCO₃‐P_i), and stable P pools (NaOH‐P and HCl‐P) and reflected the cumulative P accumulation in these soils. P saturation indices increased with cumulative P addition and increasing M1‐P. WSP increased with increasing DPS and a change point was noticed at 23% DPS_PSI (equivalent to DPS_M1 of 16.5%) corresponding to M1‐P of 44.5 mg P kg^?1, which could be regarded as threshold for P loss in these soils.     

Identification of magnetic minerals related to hydrocarbon authigenesis in venezuelan oil fields using an alternative decomposition of isothermal remanence curves

In this work we try to better characterise the shallow magnetic signature of hydrocarbon microseepage in oil fields from eastern and western Venezuela. To get a better insight of the processes involved, we attempt to find out the main magnetic phases responsible for the observed oil-related shallow magnetic anomalies. In this way, a new and alternative numerical approach to decompose Isothermal Remagnetization (IRM) curves is introduced. The method is based on a Direct Signal Analysis (DSA) of the IRM curve in order to identify the number and type of magnetic components. Representative wells from western (La Victoria) and eastern (San Joaquín) Venezuelan fields are studied. The DSA approach, together with rock magnetic experimental results, indicates that in the well from western Venezuela the main magnetic mineralogy associated to hydrocarbon microseepage is magnetite. Conversely, in the well from eastern Venezuela, these MS anomalies are mainly caused by the presence of Fe-sulphides (i.e. greigite). These results support the hypothesis of two different authigenic processes. For the well at the western field, we propose that a net electron transfer from the organic matter, degraded by hydrocarbon gas leakage, should occur precipitating Fe(II) magnetic minerals (e.g. magnetite). On the other hand, in the well of the eastern field, high concentrations of H2S at shallow levels, might allow the formation of secondary Fe-sulphides.     

Transgressive dunefield landforms and vegetation associations,Doña Juana,Veracruz, Mexico

Transgressive dune fields often comprise a multiplicity of landforms where vegetation processes largely affect landform dynamics, which in turn, also affect vegetation processes. These associations have seldom been studied in detail. This paper examines four separate landform types in a complex coastal transgressive dunefield located in the central Gulf of Mexico, in order to assess the relationships between dunefield habitat, local environmental factors, vegetation associations and landform evolution. Topographic surveys using tape and clinometer were conducted in conjunction with vegetation survey transects at four locations across the Doña Juana dunefield. Vegetation surveys allowed the estimation of relative plant cover of each plant species found along the transects. A large variety of landforms were found at the Doña Juana Dunefield: deflation plains, gegenwalle (counter) ridges, transverse dune trailing ridges, blowouts and parabolic dunes, aklé (fish‐scale shaped) dunefields and precipitation ridges, with plant species associations developing on these different landforms equally variable. Flood tolerant species were located in the lower parts (deflation plain and gegenwalle ridges) whereas the older and dryer parts were covered by coastal matorral shrubs. Burial‐tolerant species were dominant in the most mobile areas (blowouts and aklé dunefield and margin). The dune trailing ridge, with relatively milder conditions, showed the highest richness, with no dominant species. A dual interaction was found such that colonizing species both create and affect topography, and in turn, topography determines vegetation association and succession patterns. In coastal dunes, the vegetation and abiotic environment (namely the different landforms and the inherent micronevironmental variability) interact tightly and generate a complex and highly dynamic biogeomorphic system where substrate mobility and colonization processes reinforce one another in positive feedback. Copyright © 2010 John Wiley & Sons, Ltd.     

Life strategies of Halobatrachus didactylus (Bloch and Schneider, 1801) in the Tagus estuary: Comparison among different morphotypes

The Lusitanian toadfish, Halobatrachus didactylus (Bloch and Schneider, 1801), is a subtropical sound-producing marine teleost that inhabits estuaries and other brackish water ecosystems in its northern distribution area. The relative isolation of populations within estuaries may cause important modifications in the bio-ecology of this species. The males of this species present two morphotypes which are more accurately distinguishable during the reproductive season. In the Tagus estuary population, the two types of reproductive males were present: type I, the “characteristic” morphotype, and type II, the alternative morphotype. The opportunistic males had more developed testis while type I males had more developed accessory glands. Type I males presented more developed swimbladders and larger body size and live longer than type II males. On the contrary, type II males grew faster and matured earlier. The feeding habits of the two male morphotypes were similar during the reproductive season but differences were found between reproductive specimens and non-reproductive specimens. The diet of reproductive specimens was mainly composed of benthic prey in contrast to predominance of nectobenthic prey in the diet of non-reproductive specimens. The females of H. didactylus generally had an intermediate pattern between the two male morphotypes. The percentage of type II males tended to be higher in denser areas of the estuary. In comparison with populations from different size ecosystems, smaller ecosystems revealed important modifications on the bio-ecology of the species due to the increased competition for nesting sites and mating partners, favouring alternative male tactics.