Mycorrhizal Colonization Affects the Survival of Vetiveria zizanioides (L.) Nash Grown in Water Containing As(III)

The presence of arsenic (As) in water is of great public concern. Arsenic exists in three common valence states viz., As(0) metalloid arsenic, As(III) (arsenite) and As(V) (arsenate). Arsenite [As(III)] is the most toxic form among arsenicals which, predominates in anaerobic conditions, generally in flooded soils and in the water with high BOD. Experiments were conducted to investigate the effect of As(III) on the mycorrhization in vetiver (Vetiveria zizanioides (L.) Nash) grass in hydroponics. Studies showed significant alteration in the mycorrhizal colonization in the roots of vetiver exposed to higher concentrations of As(III) starting from 1.0, 2.0, 3.0, 4.0 to 5.0 mg/L prepared in 5% Hoagland nutrient solution without addition of phosphate ions. Considerable reduction in the mycorrhizal intensity (M) was observed in all the treatment sets as compared to the control suggesting a negative impact of the As(III) on the mycorrhizal association. Simultaneously, the study also showed that, As(III) is toxic to the vetiver plants having mycorrhizal association however plants with non‐mycorrhizal (cleansed) roots were found to be able to survive for a longer period exposed to As(III).     

Modeling regional landslide susceptibility using dynamic soil moisture profiles

A landslide susceptibility mapping study was performed using dynamic hillslope hydrology. The modified infinite slope stability model that directly includes vadose zone soil moisture (SM) was applied at Cleveland Corral, California, US and Krishnabhir, Dhading, Nepal. The variable infiltration capacity (VIC-3L) model simulated vadose zone soil moisture and the wetness index hydrologic model simulated groundwater (GW). The GW model predictions had a 75% NASH-Sutcliffe efficiency when compared to California’s in-situ GW measurements. The model performed best during the wet season. Using predicted GW and VIC-3L vadose zone SM, the developed landslide susceptibility maps showed very good agreement with mapped landslides at each study region. Previous quasi-dynamic model predictions of Nepal’s hazardous areas during extreme rainfall events were enhanced to improve the spatial characterization and provide the timing of hazardous conditions.     

Short‐ and long‐term evapotranspiration rates at ecological restoration sites along a large river receiving rare flow events

Many large rivers around the world no longer flow to their deltas, due to ever greater water withdrawals and diversions for human needs. However, the importance of riparian ecosystems is drawing increasing recognition, leading to the allocation of environmental flows to restore river processes. Accurate estimates of riparian plant evapotranspiration (ET) are needed to understand how the riverine system responds to these rare events and achieve the goals of environmental flows. In 2014, historic environmental flows were released into the Lower Colorado River at Morelos Dam (Mexico); this once perennial but now dry reach is the final stretch to the mighty Colorado River Delta. One of the primary goals was to supply native vegetation restoration sites along the reach with water to help seedlings establish and boost groundwater levels to foster the planted saplings. Patterns in ET before, during, and after the flows are useful for evaluating whether this goal was met and understanding the role that ET plays in this now ephemeral river system. Here, diurnal fluctuations in groundwater levels and Moderate Resolution Imaging Spectroradiometer (MODIS) data were used to compare estimates of ET specifically at 3 native vegetation restoration sites during 2014 planned flow events, and MODIS data were used to evaluate long‐term (2002–2016) ET responses to restoration efforts at these sites. Overall, ET was generally 0–10 mm d^?1 across sites, and although daily ET values from groundwater data were highly variable, weekly averaged estimates were highly correlated with MODIS‐derived estimates at most sites. The influence of the 2014 flow events was not immediately apparent in the results, although the process of clearing vegetation and planting native vegetation at the restoration sites was clearly visible in the results.     

Static deformation of two welded half-spaces due to very long strike-slip dislocations

Closed form analytic expressions for displacement and stresses at any point of either of the two homogeneous, isotropic, perfectly elastic half-spaces in welded contact due to very long strike-slip dislocations are obtained. Both cases of vertical and horizontal strike-slip dislocations are discussed in detail. Variation of the displacement with horizontal distance from the fault and with vertical distance from the interface for a vertical strike-slip fault is studied numerically.     

Geochemical processes regulating groundwater chemistry with special reference to nitrate and fluoride enrichment in Chhatarpur area, Madhya Pradesh, India

The present study focuses on the hydrogeochemical composition of groundwater in Chhatarpur area with special focus on nitrate and fluoride contamination, considering the fact that groundwater is the only major source of drinking water here. Carbonate and silicate mineral weathering followed by ground water–surface water interactions, ion exchange and anthropogenic activities are mainly responsible for high concentrations of cations and anions in the groundwater in the region. The average concentration of nitrate and fluoride found in 27 samples is 1.08 and 61.4 mg/L, respectively. Nitrate enrichment mainly occurs in areas occupied with intense fertilizer practice in agricultural fields. Since the area is not dominated by industrialization, the possibility of anthropogenic input of fluoride is almost negligible, thus the enrichment of fluoride in groundwater is only possible due to rock–water interaction. The highly alkaline conditions, which favor the fluorite dissolution, are the main process responsible for high concentration of fluoride.     

Concurrent Use of OSCAT and AltiKa to Characterize Antarctic Ice Surface Features

Radar altimetry provides an important geophysical parameter, backscatter coefficient (σ₀), which is useful in studying target surface characteristics. Ku-band (Oceansat-2 scatterometer- OSCAT) and Ka-band (SARAL-AltiKa altimeter) data are concurrently used to characterize polar surface features over the Antarctic region. Maximum-likelihood classification has been employed to classify combined data set (AltiKa and OSCAT) for discrimination among sea ice, open water, and ice sheet (interior and exterior). The sea ice region obtained using the current approach has been compared with sea ice boundary derived from passive microwave data.     

Coral communities and reefs from Guerrero,Southern Mexican Pacific

Corals in the Eastern Pacific extend south from the Gulf of California to Ecuador and oceanic Chile, and west from Colombia to Clipperton Atoll. Nevertheless, large stretches of the Mexican Pacific remain fundamentally unstudied. Therefore, to assess the current conditions of coral communities, a coastal fringe ～300 km long (17°40′ N, 101°39′ W to 16°46′ N, 99°49′ W) was surveyed within the Southern Mexican Pacific, between 2005 and 2009. Fifteen stony coral species were identified at 13 coral communities and six Pocillopora‐dominated fringing reefs, with Pocillopora verrucosa and Pocillopora damicornis the primary contributing taxa. Reef development was identified in embayments or behind rocks or islands that offered shelter from northern and northwestern winds. Observations of Pocillopora effusus, Pocillopora inflata, Porites lobata, Pavona clavus, and Pavona varians expanded the species known geographic ranges by several degrees of latitude, suggesting reef building fauna comprised a mixture of widespread and relatively rare Eastern Pacific corals. Results indicated greater live coral cover in the Ixtapa‐Zihuatanejo area (15–73%) than in the Acapulco localities, which had high algal dominance; the reefs in the latter region exhibited high erosion. Regional differences are likely the result of long‐standing anthropogenic pressures around Acapulco since 1950, when it became an important tourist destination. This paper is the first detailed report of ecologically stressed corals and coral reefs from the state of Guerrero on the Mexican Southern Pacific coast.     

Increasing imposex in populations of Bolinus brandaris (Gastropoda: Muricidae) in the northwestern Mediterranean.

The muricid gastropod Bolinus brandaris exhibited imposex, a phenomenon linked to the use of organotin biocides. Several stages of imposex development (1-5) could be distinguished and were documented with SEM-photographs for the first time in this species. Additional alterations of the genital tract in females (blocked vulva preventing copulation and deposition of egg capsules) and males (excrecences on the penis and vas deferens) were shown. Imposex intensity on the Catalan coast was very high. The frequency of imposex off Barcelona and Vilanova i la Geltrú was 100%, with all females showing stage 4. Imposex frequency off Sant Carles de la Ràpita was 99.7% and the VDS index scored 3.9. Despite regulations of TBT-containing antifouling paints in Spain since 1990, the present study revealed that frequency and intensity of imposex have increased on the Catalan coast, at least since 1997. However, at present, imposex does not apparently affect the population dynamics of B. brandaris in the studied area, since no serious consequences on female reproduction (only one case of female sterilization) were detected. Gonadal activity and oogenesis were not suppressed or supplanted by spermatogenesis. Sex ratios were not male-biased. Possible sources of organotin biocides are examined.