Sparse PCA and investigation of multi-elements compositional repositories: theory and applications

The geochemistry of floodplain sediments is fundamental to monitor environmental changes and to quantify their contribution to natural and anthropic processes. A floodplain sediment composition is a vector of positive elements which sum to a fixed constant. The analysis of high-dimensional compositions requires methods that produce results involving only a small portion of the original variables. On the other hand, the analysis must take into account the additional constraints specific to compositions. With the purpose of studying these problems, a new procedure for sparse PCA is proposed on European floodplain sediment samples.     

Streamwise velocity profiles in coastal currents

The ability to model marine currents can be a powerful device for many planning activities, for which the knowledge of the velocity field is of pivotal importance, such as the evaluation of current-induced loading on maritime structures or the diffusion and dispersion of polluted flow discharges. Observations of time-averaged velocity profiles, taken with a vessel mounted acoustic Doppler current profiler during a monitoring survey program in the seas of Southern Italy, are analysed in this paper. The measurements were taken under non-breaking conditions, offshore the surf zone, with the aim of reproducing the vertical trends of the streamwise velocity by means of standard theoretical laws. To evaluate also the possible influence of stratification on the current velocity profile shape, together with velocity measurements water temperature and salinity were also measured at the same time and locations, by means of a CTD recorder. The examined surveys referred to different time periods and sites, to guarantee a general validity of deductions. On the basis of the experiments, we verified the actual existence of a log-layer and concluded that the upper limit of the region in which the log law is applicable extends well beyond the inner region. Moreover, the deviations of the measured velocity from the logarithmic profiles above the height of the log layer is consistent with the effects of stratification. The parameters of the log law were estimated, depending on both flow dynamics and stratification in the target area. As a second step, in the most superficial and stratified layer, the velocity profiles were modelled by means of a power law, which fitted the measured data well. According to previous studies, the power law parameters result Reynolds number dependent by means of a new proposed formulation. Finally, the bottom stress and the bottom drag coefficient were investigated.     

Thermal effects on swimming activity and habitat choice in juvenile Pacific cod (Gadus macrocephalus)

The behavioral responses of fishes to temperature variation have received less attention than physiological responses, despite their direct implications for predator–prey dynamics in aquatic ecosystems. In this paper, we describe the temperature dependence of swimming performance and behavioral characteristics of juvenile Pacific cod (Gadus macrocephalus; 75–125 mm total length). Maximum swimming speeds increased with temperature and body size. Routine swimming speeds of Pacific cod in small groups of similarly sized fish (N = 6) increased with body size and were 34 % faster at 9 °C than at 2 °C. The response to temperature was opposite that previously described for juvenile walleye pollock (Theragra chalcogramma), reflecting species-specific differences in behavioral responses. In a separate experiment, we demonstrated the effect of temperature on habitat selection of juvenile Pacific cod: Use of an artificial eelgrass patch in a 5-m-long laboratory tank was significantly greater at 9 °C than at 2 °C. These results illustrate that temperature affects a range of behavioral traits that play important roles in determining the frequency and outcomes of predator–prey interactions.     

Challenges of Urban and Regional Carbon Management and the Scientific Response

Abstract

How urbanization unfolds in the text few decades and which urban development path we choose are potentially critical to the efforts aimed at stabilizing greenhouse gas emissions. However, our understanding of urban, as a unit or system, and its cross-scale linkages in the context of carbon management is at infancy state. In this context, this article outlines, the key challenges and introduces a new scientific initiative - Urban and Regional Carbon Management Initiative of the Global Carbon Project, which has raised key scientific questions with the aim to find reasonable answers. This article mainly showcases key science questions, past activities and future outlook with the aim to reach out to the related scientific and policy communities.     

Mitigating Climate Change in US Cities: Opportunities and obstacles

This study examines opportunities for and obstacles to the mitigation of climate change in US cities using the example of the Cities for Climate Protection (CCP) campaign sponsored by the International Council for Local Environmental Initiatives. The CCP experience suggests a number of ways in which municipal governments can control greenhouse gas (GHG) emissions but also highlights several obstacles that make it difficult for local officials to do so. First, climate change is generally framed as a global issue. The CCP experience suggests that climate change is most likely to be reframed as a local issue when the preferred policy response (controlling GHG emissions) can be linked to issues (e.g. air quality) already on the local agenda. Secondly, even when local governments recognise that they should do something to control GHG emissions, institutional barriers make it difficult for municipalities to move from political rhetoric to policy action. Finally, it is questionable whether local initiatives can make meaningful contributions to climate change mitigation in the absence of policy changes at the state and national levels. Este estudio examina oportunidades y obstaculos para la mitigación del cambio climático en las ciudades de Los Estados Unidos usando el ejemplo de "Ciudades para la Protección del Clima" (CCP), campaña patrocinada por el Consejo Intenacional para Iniciativas Ambientales Locales (ICLEI). La experiencia del CCP sugiere un numero de formas en que los gobiernos municipales pueden controlar las emisiones de gas efecto invernadero (GEI) pero tambien resalta varios obstaculos que hacen esto difícil para los funcionarios locales. Primero, el cambio climático es generalmente enmarcado como un asunto global. La experiencia del CCP sugiere que el cambio climático es mas probable que sea renmarcado como un asunto local cuando la respuesta de politica preferida (controlar emisiones de GEI) puede ser relacionada con asuntos que ya estan en la agenda local (ej. calidad del aire). Segundo, aún cuando los gobiernos locales reconozcan que ellos deben hacer algo para controlar las emisiones de GEI, las barreras institucionales hacen difícil que las municipalidades se muevan de retórica politíca a una acción política. Finalmene, es cuestionable si las iniciativas locales puedan hacer contribuciones significativas a la mitigación del cambio climático en ausencia de cambios de política en el estado y a nivel nacional.     

A spatial model approach for assessing windbreak growth and carbon stocks

Agroforestry, the deliberate integration of trees into agricultural operations, sequesters carbon (C) while providing valuable services on agricultural lands. However, methods to quantify present and projected C stocks in these open-grown woody systems are limited. As an initial step to address C accounting in agroforestry systems, a spatial Markov random field model for predicting the natural logarithm (log) of the mean aboveground volume of green ash ( Marsh.) within a shelterbelt, referred to as the log of aboveground volume, was developed using data from an earlier study and web-available soil and climate information. Windbreak characteristics, site, and climate variables were used to model the large-scale trend of the log of aboveground volume. The residuals from this initial model were correlated among sites up to 24 km from a point of interest. Therefore, a spatial dependence parameter was used to incorporate information from sites within 24 km into the prediction of the log of the aboveground volume. Age is an important windbreak characteristic in the model. Thus, the log of aboveground volume can be predicted for a given windbreak age and for values of other explanatory variables associated with a site of interest. Such predictions can be exponentiated to obtain predictions of aboveground volume for windbreaks without repeated inventory. With the capability of quantifying uncertainty, the model has the potential for large regional planning efforts and C stock assessments for many deciduous tree species used in windbreaks and riparian buffers once it is calibrated.     

Spatial distribution of trace elements in surface sediments of Hooghly (Ganges) river estuary in West Bengal,India

The spatial distribution of trace elements in surface sediments of the Hooghly estuary was studied over the monsoons in 2014–2017. As, Cd, Ni, Pb and U were two- to sixteen-fold the crust means with increasing levels toward the estuary, with Ni peak during the post-monsoon. Pearson’s correlation matrix, cluster analysis, enrichment factors and pollution index revealed the anthropic source and association of trace elements with Fe, Mn and Al and of Pb with U. Geoaccumulation index revealed for Ni an extremely contaminated situation at the estuary water during monsoon and for Cd a heavily contaminated situation at freshwater location. The potential contamination index was >6; thus, sediments were very severely contaminated by As, Cd and Ni with worst situation for As and Cd at fresh and brackish water and during post-monsoon. The overall ecological risk was severe, 300≤RI<600 at all sites and seasons, especially after the monsoon, at fluvial and brackish locations.

     

Shelter preference in captive juveniles of European spiny lobster <Emphasis Type="Italic">Palinurus elephas</Emphasis> (Fabricius, 1787)

Physical shelter features (e.g. shape, size and substrate slope) were tested in the laboratory to evaluate the preferences of juveniles of European spiny lobster, Palinurus elephas. Tethering experiments to assess whether substrate slope affects the vulnerability of juveniles to predation were also performed. Our results showed that: (1) semi-circular dens were significantly preferred over square and circular shapes; (2) when not disturbed by a predator, lobsters sheltered in holes with a diameter closely related to their own size, while in the presence of a potential predator lobsters showed no significant preference for a particular shelter size; (3) lobsters significantly preferred dens excavated on sub-vertical (35°) substrates over those excavated on vertical ones (90°); (4) individual lobsters tethered on vertical substrates were subject to greater predation activity than those tethered on horizontal structures. In conclusion, the present study contributes to the understanding of how physical properties of shelters affect the choice of P. elephas juveniles, enhancing their protection and survival rate.