Relating 27-Day Averages of Solar,Interplanetary Medium Parameters,and Geomagnetic Activity Proxies in Solar Cycle 24

Solar Physics - During solar minimum, the Sun is relatively inactive with few sunspots observed on the solar surface. Consequently, we observe a smaller number of highly energetic events such as...     

Assessing the factors driving the changes in the spatio-temporal distribution of Hepatus pudibundus (Decapoda,Brachyura) over a 20-year interval in a region under the influence of El Niño (ENSO)

This study aimed to compare the spatio-temporal distribution of demographic groups of Hepatus pudibundus in the Ubatuba Bay, São Paulo, Brazil, over a 20-year interval. Two 1-year samplings were conducted: the 1st period (P1) ran from September 1995 to August 1996 and the 2nd period (P2) ran from September 2016 to August 2017. Samples were taken from five stations that differed in depth (5, 10, and 15 m) and location (exposed area and sheltered area), aboard a shrimp fishing boat. Over the 20-year period, the percentage of fine sediment increased in all stations. In total, we captured 865 H. pudibundus individuals in the P1 and 4,222 in the P2. The higher abundance seen in the P2 may have been caused by the effects of an intense ENSO event in Ubatuba, as well as co-occurring protective actions against fisheries activities in the region. The spatial distribution also changed after 20 years: In the P1, H. pudibundus were more concentrated in the 15 m station and exposed area, but they shifted to the sheltered area in the P2. This change may be related to the increase of fine sediments in this area, and to the fact that it is naturally protected from fisheries. According to the correspondence analysis, the abundance of males and juveniles was correlated with spring and winter, respectively. In the P1, females were more abundant in spring, whereas in the P2 they were more abundant in summer, which may be explained by a higher nutrient availability to the larvae in the summer of the P2. Our comparisons over the 20-year interval revealed that the spatio-temporal distribution of H. pudibundus has changed and that the population is well established in Ubatuba Bay.     

Effects of pre-orogenic tectonic structures on the Cenozoic evolution of Andean deformed belts: Evidence from the Salar de Punta Negra Basin in the Central Andes of Northern Chile

We integrated new field observations, two-dimensional (2-D) seismic profiles and new and previously reported chronological data to understand the effects of pre-orogenic structures on the tectonic evolution of the Salar de Punta Negra in the Central Andes. For first time a series of restored geological cross-sections are presented, thus showing the pre-orogenic tectonic architecture of the region and new ideas about the tectonic evolution of the inner forearc of the Central Andes. Our results show a series of east-dipping normal faults as the main pre-orogenic structures in the region, which resulted from lithospheric stretching of the western continental margin during the Paleozoic to Mesozoic (Triassic–Jurassic). These were later incorporated into the Andean orogen by tectonic inversion, forming west-verging inversion anticlines. The beginning of the tectonic inversion is constrained by the first on-lap of the Upper Cretaceous-Palaeocene syn-kinematic deposits on the top of the Mesozoic syn-rift successions, highlighting that inversion occurred during this period. These syn-kinematic deposits display zircons with older age peaks between ca. 200 and 300 Ma, thus indicating that some Carboniferous to Triassic sources of sediments were eroded during the uplift of the orogen. Other basement reverse faults affect the footwalls of normal inverted faults and the shoulders of ancient half-graben structures. These truncate and decapitate previous inverted faults and completely cut the infill of the basin, leading to exhumation of the pre-rift basement rocks. We propose that the propagation of these structures was favoured by the modified thermal-tectonic state of the lithosphere from the eastward migration of the volcanic arc, and not by the previous pre-orogenic structures. The structural and stratigraphic relationships recognized both in the field and 2-D seismic profiles indicate that many reverse faults originated after the initial tectonic inversion and continued to be active from the Eocene until the Pleistocene period.     

Quality assessment of digital surface models extracted from WorldView-2 and WorldView-3 stereo pairs over different land covers

Digital surface models (DSMs) extracted from very high resolution (VHR) satellite stereo images are becoming more and more important in a wide range of geoscience applications. The number of software packages available for generating DSMs has been increasing rapidly. The main goal of this work is to explore the capabilities of VHR satellite stereo pairs for DSMs generation over different land-cover objects such as agricultural plastic greenhouses, bare soil and urban areas by using two software packages: (i) OrthoEngine (PCI), based on a hierarchical subpixel mean normalized cross correlation matching method, and (ii) RPC Stereo Processor (RSP), with a modified hierarchical semi-global matching method. Two VHR satellite stereo pairs from WorldView-2 (WV2) and WorldView-3 (WV3) were used to extract the DSMs. A quality assessment on these DSMs on both vertical accuracy and completeness was carried out by considering the following factors: (i) type of sensor (i.e., WV2 or WV3), (ii) software package (i.e., PCI or RSP) and (iii) type of land-cover objects (plastic greenhouses, bare soil and urban areas). A highly accurate light detection and ranging (LiDAR) derived DSM was used as the ground truth for validation. By comparing both software packages, we concluded that regarding DSM completeness, RSP produced significantly (p < 0.05) better scores than PCI for all the sensors and type of land-cover objects. The percentage improvement in completeness by using RSP instead of PCI was approximately 2%, 18% and 26% for bare soil, greenhouses and urban areas respectively. Concerning the vertical accuracy in root mean square error (RMSE), the only factor clearly significant (p < 0.05) was the land cover. Overall, WV3 DSM showed slightly better (not significant) vertical accuracy values than WV2. Finally, both software packages achieved similar vertical accuracy for the different land-cover objects and tested sensors.     

Response of Acartia populations to environmental variability and effects of invasive congenerics in the estuary of Bilbao, Bay of Biscay

The effect of environmental factors (river discharge, water temperature and dissolved oxygen saturation) on the abundance and distribution of Acartia populations and the interactions between their congenerics was evaluated by means of transfer function (TF) models in the estuary of Bilbao during the period 1998–2005. The recorded species were Acartia clausi, Acartia tonsa, Acartia margalefi and Acartia discaudata. Acartia clausi dominated in the entire euhaline region of this estuary until 2003 when it was displaced from the inner part by A. tonsa. This invasive species (A. tonsa) was found for the first time in 2001 and colonized successfully the inner (salinity 30) and intermediate (salinity 33) waters of this estuary since 2003. The TF models revealed an immediate and negative effect of A. tonsa on A. clausi in the intermediate salinity (33) waters, where these species showed the highest spatial overlap. The results indicate that environmental changes from 2003 influenced the abundance of Acartia species, being unfavourable for A. clausi. The decrease of A. clausi abundance in low salinity waters was related to a significant decrease of dissolved oxygen saturation levels, whereas the increase of temperature was linked to a significant increase of A. tonsa. Acartia margalefi and A. discaudata were scarce over the entire period, but they were found to be valuable indicators of hydrological changes, which were associated to climate factors. These two latter species increased in abundance and expanded their seasonal distribution, and in the case of A. margalefi also its spatial distribution, in 2002, coinciding with the period in the time-series when autumn–winter rainfall and summer temperatures were lowest, and dissolved oxygen saturation levels were highest.     

In situ experimental study of reed leaf decomposition along a full salinity gradient

An experimental study on Phragmites australis leaf litter decomposition was conducted in the estuarine environment, Ria de Aveiro, Western Portugal, using the leaf-bag technique, with fine- (1 mm) and coarse-mesh (5 mm) bags. The leaf bags were placed in the field sites at day 0, covering a complete salinity gradient, and replicates were collected over time, at days 3 (leaching), 7, 15, 30 and 60. The biomass loss through the leaching phase, about 20% of the initial leaf mass, was independent of both the salinity and the bag mesh size. The biomass decay pattern along the salinity gradient varied through time and presented strong similarities between the two mesh sizes, with the remaining biomass always lower in the 5 mm mesh-size bags. At days 7 and 15, the lowest remaining biomass was observed at the head of the estuary, the preferential distribution area of P. australis. At day 30, the remaining biomass was higher in the marine area and diminished under a direct relationship with salinity, reaching the lowest value in the freshwater environment, with values ranging from 66% to 44% of the initial weight in 5 mm bags, and from 79% to 51% in 1 mm bags. The largest heterogeneity in the remaining biomass among the study areas positioned along the salinity gradient was found close to days 30 (5 mm) and 40 (1 mm). The overall results indicate that the relationship between leaf decay rate and salinity depends on the decay time considered (k₁₅, k₃₀ or k₆₀) and, for the later stages (k₆₀), also on the leaf-bag mesh size. This implies that the use of leaf litter decay rates as a functional indicator in transitional waters will need to take into consideration the factor location in the salinity gradient and leaf litter stage at which the decay rate is determined. The differences between the decay rates with the mesh size acted mainly at the level of the absolute k value and not at the level of the pattern along the salinity gradient. Even so, the data obtained at the mouth of the estuary, in the area closest to a fully marine environment, indicated that after the initial biomass loss through leaching, P. australis decayed either very slowly, in the 5 mm, or not at all, in the 1 mm mesh bags.     

Defining parameters for Eckhardt's digital baseflow filter

Digital filters are useful tools for assessing the contribution of groundwater to total river flow. Several of those filters have been proposed in the last decades. One of the last contributions on this subject was given by Ekchardt (2005) who proposed a more general form of a digital baseflow filter and showed that some of the most used filters are special cases of this general form. This new filter has the inconvenience of having two parameters, one of them may be obtained directly from recession analysis, but the other (maximum baseflow index (BFImax)) is routinely estimated by a priori defined values according to the predominant geological characteristics of the drainage basin. In this short communication, we propose a method to estimate BFImax by a backwards filtering operation. The method was applied using data from 15 gauging stations in Brazil, with a varied range of groundwater contribution to streamflow. Results of the new estimation method for the BFImax parameter are coherent with the values which would be adopted by considering geological characteristics of the river basins. Copyright © 2012 John Wiley & Sons, Ltd.