Functional Performance of Three Invasive <Emphasis Type="Italic">Marenzelleria</Emphasis> Species Under Contrasting Ecological Conditions Within the Baltic Sea

A 4-week laboratory experiment investigated the behaviour (survival and bioirrigation) and impact of the invasive polychaetes Marenzelleria viridis, M. neglecta and M. arctia on sediment-water solutes exchange, porewater chemistry, and Fe and P interactions in high-salinity sandy sediment (HSS) and low-salinity muddy sediment (LSM) from the Baltic Sea. M. viridis showed deep burrowing with efficient bioirrigation (11 L m^?2 day^?1) and high survival (71%) in HSS, while M. arctia exhibited shallow burrowing with high bioirrigation (12 L m^?2 day^?1) and survival (88%) in LSM. M. neglecta behaved poorly in both ecological settings (bioirrigation, 5–6 L m^?2 day^?1; survival, 21–44%). The deep M. viridis bioirrigation enhanced total microbial CO₂ (TCO₂) production in HSS by 175% with a net efflux of NH₄⁺ and PO₄^3?, at rates 3- to 27-fold higher than for the other species. Although the shallow and intense bioirrigation of M. arctia in LSM stimulated microbial TCO₂ production to some extent (61% enhancement), the nutrient fluxes close to zero indicate that it effectively prevented the P release. Porewater Fe:PO₄^3? ratios revealed that the oxidizing effect of M. arctia bioirrigation increased the PO₄^3? adsorption capacity of LSM twofold relative to defaunated controls while no buffering of PO₄^3? was detected in M. viridis HSS treatment. Therefore, the different behaviour of the three species in various environments and the sharp contrast between M. viridis and M. arctia effects on C, N and P cycling must be considered carefully when the ecological role of Marenzelleria species in the Baltic Sea is evaluated.     

Gorkha earthquake (MW7.8) and aftershock sequence: A fractal approach

On April 25, 2015, Nepal was struck by the M_W7.8 Gorkha earthquake followed by an intense aftershock sequence. It was one of the most destructive earthquakes in the Himalayan arc, causing more than 8900 fatalities. In this study, we analyzed the dataset (429 events, magnitude of completeness (M_c) ≥ 4.2 local magnitude) of the first 45 days after the Gorkha earthquake to estimate the seismicity parameters b-value, D-value, and p-value. We used the maximum likelihood method to estimate the b-value and Omori-Utsu parameters, whereas the correlation integral method was applied to estimate the fractal dimension (D-value). The analysis was carried out using running and sliding window techniques. The lowest b-value (0.57 ± 0.04) and the highest D-value (1.65 ± 0.02) were computed at the time of the Gorkha earthquake, after which the b-value significantly increased to a maximum of 1.57. It again dropped to 0.93 at the time of the major aftershock on May 12, 2015. The D-value showed an initial quick drop and then decreased in a wavy pattern until the end of the study period, indicating the clustering and scattering of earthquakes in a fault region. The b-value contour map identified the eastern part of the study area as a high stress region (b = ～0.8), implying that the stress shifted to that region. The D-value contour map reveals that the seismogenic structure shifted from linear to planar in the region. The rate of aftershock decay (p = 0.86 ± 0.04) for a short period reflects that the level of stress decreased rapidly. This study helps to understand the level of stress and seismicity pattern of a region, which could be useful for aftershock studies.     

Aridity indices to assess desertification susceptibility: a methodological approach using gridded climate data and cartographic modeling

Natural Hazards - Desertification is a land degradation phenomenon with dire and irreversible consequences, affecting different regions of the world. Assessment of spatial climate susceptibility to...     

Mid‐ and Large‐Scale Geodiversity Calculation in Fuentes Carrionas (NW Spain) and Serra do Cadeado (Paraná, Brazil): Methodology and Application for Land Management

A state‐of‐the‐art geodiversity concept, its use and scientific development are presented. Methodologies for geodiversity calculation are assessed, as well as their aim and problems. Geodiversity calculation methodology based on biodiversity richness index is explained and applied to two different areas: Fuentes Carrionas, a high mountain mid‐latitude environment in northern Spain, and Serra do Cadeado, a tropical mid‐mountain environment in southern Brasil. A geodiversity map of Fuentes Carrionas proves that glacial cirques over 2000 m a.s.l. keep a high geodiversity related to a periglacial and glacial environment, whereas a geodiversity map of Serra do Cadeado shows that high geodiversity areas are situated at its main structural scarp. Geodiversity calculation needs to take scale and hierarchy issues into account, which makes comparison only possible if the same scale is used. Geodiversity calculation is a useful tool for land management as it defines areas subject to protection due to the richness of abiotic elements. It is also useful in terms of environmental impact assessment and geotourism evaluation at remote areas.     

Groundwater Quality assessment using Water Quality Index (WQI) in parts of Varanasi District,Uttar Pradesh,India

Either naturally occurring process or human activities may have a significant impact on the quality of sub-surface waters which further limit its use. Multivariate statistical techniques such as factor analysis (FA), cluster analysis (CA) were applied for the evaluation of spatial variations and the interpretation of ground water quality data around Bacheli and Kirandul area. The major anions, cations and heavy metals were determined for each of 20 samples collected in pre-monsoon seasons. Hydrochemical parameters like EC, pH, TDS, TH, TA, Na⁺, K⁺, Ca²⁺, Cl^-, F^-, SO₄^2-, As, Sb, Se, Pb, Cd, Zn, Cu were estimated in pre monsoon and post monsoon seasons. Different geochemical controls of the investigated parameters were also assessed. Factor 1 explains 33.47% of the total variance and indicates atmospheric controls and silicate mineral weathering process. Factor 2 explains 13.83% of total variance, indicating silicate mineral weathering process resulting in elevated pH. Generally, water types tend towards magnesium-bicarbonate-chloride.     

A hurricane surge risk assessment framework using the joint probability method and surge response functions

Hurricane surge events have caused devastating damage in active-hurricane areas all over the world. The ability to predict surge elevations and to use this information for damage estimation is fundamental for saving lives and protecting property. In this study, we developed a framework for evaluating hurricane flood risk and identifying areas that are more prone to them. The approach is based on the joint probability method with optimal sampling (JPM-OS) using surge response functions (SRFs) (JPM-OS-SRF). Derived from a discrete set of high-fidelity storm surge simulations, SRFs are non-dimensional, physics-based empirical equations with an algebraic form, used to rapidly estimate surge as a function of hurricane parameters (i.e., central pressure, radius, forward speed, approach angle and landfall location). The advantage of an SRF-based approach is that a continuum of storm scenarios can be efficiently evaluated and used to estimate continuous probability density functions for surge extremes, producing more statistically stable surge hazard assessments without adding measurably to epistemic uncertainty. SRFs were developed along the coastline and then used to estimate maximum surge elevations with respect to a set of hurricane parameters. Integrating information such as ground elevation, property value and population with the JPM-OS-SRF allows quantification of storm surge-induced hazard impacts over the continuum of storm possibilities, yielding a framework to create the following risk-based products, which can be used to assist in hurricane hazard management and decision making: (1) expected annual loss maps; (2) flood damage versus return period relationships; and (3) affected business (e.g., number of business, number of employees) versus return period relationships. By employing several simplifying assumptions, the framework is demonstrated at three northern Gulf of Mexico study sites exhibiting similar surge hazard exposure. The framework results reveal Gulfport, MS, USA is at relatively more risk of economic loss than Corpus Christi, TX, USA, and Panama City, FL, USA. Note that economic processes are complex and very interrelated to most other human activities. Our intention here is to present a methodology to quantify the flood damage (i.e., infrastructure economic loss, number of businesses affected, number of employees in these affected businesses and sales volume in these affected businesses) but not to discuss the complex interactions of these damages with other economic activities and recovery plans.     

Subdivision and fragmentation of land holdings and their implication in desertification in the Thar Desert, India

Analysis of data at the household level in Khabra Kalan village in the Thar desert of India revealed that the land holding size is halved every 20–30 years due to subdivision of land holdings. The subdivision is caused by the equal sharing among sons at the time of inheritance based on the succession laws, and attributed to the increase in the village population. The shrinking land holdings resulted in a shortfall of food on small farms; 12% in cereals and 42% in pulses, promoted continuous cultivation and the increase of monoculture, and deteriorated the land productivity through its effect on the soil fertility and land management.