23 research outputs found
Dynamical Dark Energy simulations: high accuracy Power Spectra at high redshift
Accurate predictions on non--linear power spectra, at various redshift z,
will be a basic tool to interpret cosmological data from next generation mass
probes, so obtaining key information on Dark Energy nature. This calls for high
precision simulations, covering the whole functional space of w(z) state
equations and taking also into account the admitted ranges of other
cosmological parameters; surely a difficult task. A procedure was however
suggested, able to match the spectra at z=0, up to k~3, hMpc^{-1}, in
cosmologies with an (almost) arbitrary w(z), by making recourse to the results
of N-body simulations with w = const. In this paper we extend such procedure to
high redshift and test our approach through a series of N-body gravitational
simulations of various models, including a model closely fitting WMAP5 and
complementary data. Our approach detects w= const. models, whose spectra meet
the requirement within 1% at z=0 and perform even better at higher redshift,
where they are close to a permil precision. Available Halofit expressions,
extended to (constant) w \neq -1 are unfortunately unsuitable to fit the
spectra of the physical models considered here. Their extension to cover the
desired range should be however feasible, and this will enable us to match
spectra from any DE state equation.Comment: method definitely improved in semplicity and efficacy,accepted for
publication on JCA
An Integrated Approach for Evaluating the Restoration of the Salinity Gradient in Transitional Waters: Monitoring and Numerical Modeling in the Life Lagoon Refresh Case Study
Large lagoons usually show a salinity gradient due to fresh water tributaries with inner
areas characterized by lower mean values and higher fluctuation of salinity than seawaterdominated
areas. In the Venice Lagoon, this ecotonal environment, characterized in the past by
oligo‐mesohaline waters and large intertidal areas vegetated by reedbeds, was greatly reduced by
historical human environmental modifications, including the diversion of main rivers outside the
Venice Lagoon. The reduction of the fresh water inputs caused a marinization of the lagoon, with
an increase in salinity and the loss of the related habitats, biodiversity, and ecosystem services. To
counteract this issue, conservation actions, such as the construction of hydraulic infrastructures for
the introduction and the regulation of a fresh water flow, can be implemented. The effectiveness of
these actions can be preliminarily investigated and then verified through the combined
implementation of environmental monitoring and numerical modeling. Through the results of the
monitoring activity carried out in Venice Lagoon in the framework of the Life Lagoon Refresh
(LIFE16NAT/IT/000663) project, the study of salinity is shown to be a successful and robust
combination of different types of monitoring techniques. In particular, the characterization of
salinity is obtained by the acquisition of continuous data, field campaigns, and numerical modeling
Aquatic Angiosperm Transplantation: A Tool for Environmental Management and Restoring in Transitional Water Systems
Since the 1960s, the Venice Lagoon has suffered a sharp aquatic plant constriction due to eutrophication, pollution, and clam fishing. Those anthropogenic impacts began to decline during the 2010s, and since then the ecological status of the lagoon has improved, but in many choked areas no plant recolonization has been recorded due to the lack of seeds. The project funded by the European Union (LIFE12 NAT/IT/000331-SeResto) allowed to recolonize one of these areas, which is situated in the northern lagoon, by widespread transplantation of small sods and individual rhizomes. In-field activities were supported by fishermen, hunters, and sport associations; the interested surface measured approximately 36.6 km2. In the 35 stations of the chosen area, 24,261 rhizomes were transplanted during the first year, accounting for 693 rhizomes per station. About 37% of them took root in 31 stations forming several patches that joined together to form extensive meadows. Plant rooting was successful where the waters were clear and the trophic status low. But, near the outflows of freshwater rich in nutrients and suspended particulate matter, the action failed. Results demonstrate the effectiveness of small, widespread interventions and the importance of engaging
the population in the recovery of the environment, which makes the action economically cheap and replicable in other similar environments
Expected Shifts in Nekton Community Following Salinity Reduction: Insights into Restoration and Management of Transitional Water Habitats
Abstract: A restoration project is planned to take place in the northern Venice lagoon (northern
Adriatic Sea, Italy), aiming at introducing freshwater into a confined shallow water lagoon area and
recreating transitional water habitats. This work describes the shifts in the nekton (fish and decapods)
community structure to be expected following the future salinity decrease in the restoration area.
Nekton was sampled at a series of natural shallow water sites located along salinity gradients in
the Venice lagoon. A multivariate GLM approach was followed in order to predict species biomass
under the salinity and environmental conditions expected after restoration. Biomass of commercially
important species, as well as species of conservation interest, is predicted to increase following
salinity reduction and habitat changes. From a functional perspective, an increase in biomass of
hyperbenthivores-zooplanctivores, hyperbenthivores-piscivores and detritivores is also expected.
This study emphasises the ecacy of a predictive approach for both ecological restoration and
ecosystem management in transitional waters. By providing scenarios of community structure,
the outcomes of this work could be employed in future evaluations of restoration success in the
Venice lagoon, as well as to develop management tools to forecast the eects of alterations of salinity
regimes in coastal lagoons due to climate change