1,721,079 research outputs found
Effects of ocean acidification on benthic organisms in the Mediterranean Sea under realistic climatic scenarios: A meta-analysis
No full textOcean acidification is expected to cause significant changes in the marine environment over the coming century. The effects of acidificationonorganisms’ physiology have been studied over the pasttwodecades. However, the experimental findings are not always easily comparable because of differences in experi- mental design, and comparable experimentsdonot always produce similar results. To rigorously integrate the current knowledge, we performed a meta-analysis of published studies focused on benthic organisms in the Mediterranean Sea, both in controlled manipulative experiments and in situ experiments near vent areas. In each experiment, the effect of acidification was calculated as the log-transformed response ratio (LnRR) of experimental versus control conditions. The quantitative results obtained by the meta-analysis highlight: (a) an increase in fleshy algae cover, which may lead to a competitive advantage over calcify- ing macroalgae; (b) a reduction of calcification by both algae and corals; (c) an increase in seagrass shoot density under low pH; and (d) a general increase in the photosynthetic activity of macrophytes
Effects of solar irradiance noise on a complex marine trophic web
Full text linkThe analysis of experimental data of the solar irradiance, collected on the marine surface, clearly highlights the intrinsic stochasticity of such an environmental parameter. Given this result, effects of randomly fluctuating irradiance on the population dynamics of a marine ecosystem are studied on the basis of the stochastic 0-dimensional biogeochemical flux model. The noisy fluctuations of the irradiance are formally described as a multiplicative Ornstein-Uhlenbeck process, that is a self-correlated Gaussian noise. Nonmonotonic behaviours of the variance of the marine populations’ biomass are found with respect to the intensity and the autocorrelation time of the noise source, manifesting a noise-induced transition of the ecosystem to an out-of-equilibrium steady state. Moreover, evidence of noise-induced effects on the organic carbon cycling processes underlying the food web dynamics are highlighted. The reported results clearly show the profound impact the stochastic environmental variables can have on both the populations and the biogeochemistry at the basis of a marine trophic network
Cumulative Impact Index for the Adriatic Sea: Accounting for interactions among climate and anthropogenic pressures
Full text linkAssessing and managing cumulative impacts produced by interactive anthropogenic and natural drivers is a major challenge to achieve the sustainable use of marine spaces in line with the objectives of relevant EU acquis. However, the complexity of the marine environment and the uncertainty linked to future climate and socio-economic scenarios, represent major obstacles for understanding the multiplicity of impacts on the marine ecosystems and to identify appropriate management strategies to be implemented. Going beyond the traditional additive approach for cumulative impact appraisal, the Cumulative Impact Index (CI-Index) proposed in this paper applies advanced Multi-Criteria Decision Analysis techniques to spatially model relationships between interactive climate and anthropogenic pressures, the environmental exposure and vulnerability patterns and the potential cumulative impacts for the marine ecosystems at risk. The assessment was performed based on spatial data characterizing location and vulnerability of 5 relevant marine targets (e.g. seagrasses and coral beds), and the distribution of 17 human activities (e.g. trawling, maritime traffic) during a reference scenario 2000-2015. Moreover, projections for selected physical and biogeochemical parameters (temperature and chlorophyll 'a') for the 2035-2050 timeframe under RCP8.5 scenario, were integrated in the assessment to evaluate index variations due to changing climate conditions. The application of the CI-Index in the Adriatic Sea, showed higher cumulative impacts in the Northern part of the basin and along the Italian continental shelf, where the high concentration of human activities, the seawater temperature conditions and the presence of vulnerable benthic habitats, contribute to increase the overall impact estimate. Moreover, the CI-Index allowed understanding which are the phenomena contributing to synergic pressures creating potential pathways of environmental disturbance for marine ecosystems. Finally, the application in the Adriatic case showed how the output of the CI-Index can provide support to evaluate multi-risk scenarios and to drive sustainable maritime spatial planning and management.Assessing and managing cumulative impacts produced by interactive anthropogenic and natural drivers is a major challenge to achieve the sustainable use of marine spaces in line with the objectives of relevant EU acquis. However, the complexity of the marine environment and the uncertainty linked to future climate and socioeconomic scenarios, represent major obstacles for understanding the multiplicity of impacts on the marine ecosystems and to identify appropriate management strategies to be implemented. Going beyond the traditional additive approach for cumulative impact appraisal, the Cumulative Impact Index (CI-Index) proposed in this paper applies advanced Multi-Criteria Decision Analysis techniques to spatially model relationships between interactive climate and anthropogenic pressures, the environmental exposure and vulnerability patterns and the potential cumulative impacts for the marine ecosystems at risk. The assessment was performed based on spatial data characterizing location and vulnerability of 5 relevant marine targets (e.g. seagrasses and coral beds), and the distribution of 17 human activities (e.g. trawling, maritime traffic) during a reference scenario 2000-2015. Moreover, projections for selected physical and biogeochemical parameters (temperature and chlorophyll 'a') for the 2035-2050 timeframe under RCP8.5 scenario, were integrated in the assessment to evaluate index variations due to changing climate conditions. The application of the CI-Index in the Adriatic Sea, showed higher cumulative impacts in the Northern part of the basin and along the Italian continental shelf, where the high concentration of human activities, the seawater temperature conditions and the presence of vulnerable benthic habitats, contribute to increase the overall impact estimate. Moreover, the CI-Index allowed understanding which are the phenomena contributing to synergic pressures creating potential pathways of environmental disturbance for marine ecosystems. Finally, the application in the Adriatic case showed how the output of the CI-Index can provide support to evaluate multi-risk scenarios and to drive sustainable maritime spatial planning and management. (C) 2019 Elsevier B.V. All rights reserved
Hypoxia extreme events in a changing climate: Machine learning methods and deterministic simulations for future scenarios development in the Venice Lagoon
Full text linkClimate change pressures include the dissolved oxygen decline that in lagoon ecosystems can lead to hypoxia, i.e.
low dissolved oxygen concentrations, which have consequences to ecosystem functioning including biogeochemical
cycling from mild to severe disruption. The study investigates the potential of machine learning (ML)
and deterministic models to predict future hypoxia events. Employing ML models, e.g. Random Forest and
AdaBoost, past hypoxia events (2008–2019) in the Venice Lagoon were classified with an F1 score of around
0.83, based on water quality, meteorological, and spatio-temporal factors. Future scenarios (2050, 2100) were
estimated by integrating hydrodynamic-biogeochemical and climate projections. Results suggest hypoxia events
will increase from 3.5 % to 8.8 % by 2100, particularly in landward lagoon areas. Summer prediction foresee a
rise from 118 events to 265 by 2100, with a longer hypoxia-prone season. This model is a valuable tool for
developing hypoxia scenarios, aiding in identifying restoration hotspots for climate-threatened lagoons
Performance of different modeling techniques in testing the impact of environmental variables on eel landing in Ichkeul Lake, a RAMSAR Wetland and UNESCO biosphere reserve
No full textAdvanced modeling techniques, including Random Forest (RF) and Cubist model (CB), were used to assess the relationship between environmental factors and European eels (Anguilla anguilla) abundance and to provide insights into the lake's ecological status while considering climate change and anthropogenic influences. A comprehensive dataset, attained through extensive environmental and biological monitoring for the period 2010–2020, was employed. The performance of the models is carried out using key metrics including the root mean square error (RMSE), coefficient of determination (R2), and mean estimation error (MAE). In addition, a sensitivity analysis was conducted to ascertain the relative significance of the thirteen input variables in shaping the predictions of the models. The precision of the CB and RF models in predicting eel landings surpassed that of Multiple Regression. In the training dataset, the CB model achieved R2=0.55, RMSE=7.68 tons, and MSE=6.20 tons, and the RF model achieved R2=0.56, RMSE=7.20 tons, and MSE=5.56 tons. High accuracy was maintained on the testing dataset, with CB achieving R2=0.73, RMSE=5.13 tons, and MSE=5.89 tons, and RF achieving R2=0.73, RMSE=5.81 tons, and MSE=4.67 tons. The scatter plot between predicted and measured eel landings indicated that the RF model tends to overestimate lower values and underestimate higher values of eel landings, while the CB model gave better performance in this context. Further, the carried sensitivity analysis using the CB model unequivocally identified three pivotal factors – water level, salinity, and turbidity level – as the most influential determinants governing the landing of eels in this ecosystem. Thus, the CB model is considered to be more promising for interpreting the relationship between environmental parameters and eel landings, which could be used by managers for an effective lake management strategy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Analysis and modelling of biogeochemical and ecological characteristics in coastal waters of the Northern Adriatic sea
No full text2005/2006Il presente lavoro di dottorato ha avuto come obiettivo l'identificazione e l'interpretazione di
situazioni di riferimento e di relazioni tra caratteristiche abiotiche e caratteristiche biotiche in ambienti marini costieri, attraverso l'uso di metodi multivariati tradizionali e di metodi basati sulle reti neurali per la classificazione, l'analisi di gradiente e la modellazione di dati ambientali.
Il crescente interesse per gli ambienti marini e in particolare per le aree costiere nasce
dall'importanza che tali aree hanno per la vita dell'uomo, e dalla considerazione che esse sono
soggette a molteplici impatti antropici che interagiscono con le grandi eterogeneità e variabilità intrinseche degli agenti forzanti naturali degli ambienti costieri. In particolare le aree costiere sono interessate da elevata densità abitativa, sono sede di attività portuali ed industriali, di attività di
pesca ed acquacoltura e di attività turistiche. Le esigenze contrastanti di tali attività devono inoltre permettere una fruizione senza rischi delle aree marine costiere per attività di diporto e di tempo libero, e spesso tutto ciò è in contrasto con le esigenze di conservazione del loro valore naturalistico, paesaggistico, storico ed artistico.
Per una corretta implementazione di politiche di conservazione biologica, gestione e
recupero ambientale è dunque necessaria l'identificazione di situazioni di riferimento, e la descrizione della loro evoluzione nel tempo e nello spazio, contro di cui confrontare la situazione attuale o gli obiettivi di ripristino posti dalla legislazione. L'importanza di tale obiettivo è riconosciuta nell'ambito scientifico internazionale e recepita da recenti disposizioni legislative. In particolare la direttiva europea 2000/60/CE prevede che siano effettuate analisi delle caratteristiche dei diversi corpi d'acqua e che siano definite delle condizioni di riferimento tipiche specifiche per
ognuno di essi. Gli elementi da considerare per le acque costiere e le acque di transizione per
raggiungere tali obiettivi includono la composizione e le abbondanze delle popolazioni planctoniche e bentoniche, i parametri chimico-fisici e le condizioni morfologiche.
Nel presente lavoro di ricerca sono stati analizzati dataset riferiti ad ambienti costieri e di transizione dell'Adriatico settentrionale. Secondo la disponibilità di dati, tali dataset contenevano variabili chimico-fisiche (p.es. temperatura, salinità, nutrienti), morfologiche (p.es. profondità), idrodinamiche (p.es. tempi di residenza) e biologiche (p.es. abbondanze planctoniche, ricoprimenti
bentonici). L'obiettivo delle analisi sui dataset di parametri chimico-fisici è consistito
nell'identificazione di masse d'acqua omogenee, che consiste nell'individuazione del numero delle
masse d'acqua, nella descrizione delle loro caratteristiche in funzione delle variabili utilizzate, nella derivazione di una loro evoluzione spazio-temporale tipica, e nell'interpretazione della loro
dinamica in funzione di fenomeni e forzanti noti. A tal fine sono stati utilizzati soprattutto metodi multivariati di ordinamento e clusterizzazione, quali k-means, Self-Organizing Map, fuzzy k-means.
L'obiettivo dell'analisi su dati biologici era l'identificazione e la descrizione di biocenosi
caratteristiche di una certa area e momento. I dati biologici erano riferiti ad organismi appartenenti ad un unico comparto trofico (p.es. autotrofi), oppure ad organismi di comparti trofici diversi. In generale, si è cercato di caratterizzare ogni biocenosi attraverso l'individuazione delle specie
caratteristiche, cioè quelle che indicano il verificarsi di determinate condizioni ambientali, e delle specie dominanti, cioè quelle che maggiormente contribuiscono ai flussi di materia ed energia in ogni biocenosi. Un ulteriore obiettivo è stata la ricerca di relazioni tra biocenosi e variabili chimicofisiche
e spazio-temporali, e l'interpretazione di tali relazioni secondo plausibili modelli causali. Per
questi fini sono stati utilizzati metodi di analisi di gradiente indiretta (clusterizzazione e ricerca
relazioni con variabili), metodi di analisi di gradiente diretta (Redundancy Analysis, Canonical
Correspondence Analysis) e metodi di predizione (Backpropagation Neural Network).
Il lavoro si è quindi articolato in diverse fasi nel corso delle quali sono stati considerati aree
e metodologie diverse in funzione della disponibilità ed accessibilità di dati storici o attuali. Per analizzare dataset molto diversi tra loro è stato necessario l'utilizzo e la messa a punto di strumenti avanzati di analisi e modellamento dei dati e di presentazione dei risultati. I problemi più frequentemente incontrati erano legati alla tipologia dei dataset disponibili, quasi mai costruiti con
lo scopo di testare un'ipotesi precisa, ma risultanti piuttosto da fusioni a posteriori di insiemi di dati raccolti nel corso di progetti diversi, con finalità , metodologie e disegni sperimentali differenti.
Molte volte i dati sono stati raccolti con una copertura insufficiente nella dimensione spaziale o temporale, che ha reso quindi difficoltosa l'applicazione di metodi statistici rigorosi e la
generalizzazione dei risultati nel dominio del tempo e dello spazio. In fase di pretrattamento è stato sovente necessario ricorrere a procedure di trasformazione e di aggregazione dei dati, e di codifica di alcuni parametri in variabili qualitative. Le variabili biologiche hanno presentato ulteriori problemi data la stocasticità dei fenomeni biologici, l'incertezza nella determinazione di alcune
specie e la conseguente eterogeneità e complessità dei dataset. La scelta della metrica opportuna è stata quindi un passo necessario in tutte le analisi su dati biologici.
In particolare gli studi effettuati nel lavoro di dottorato ed esposti nella presente tesi sono i
seguenti: studio sulle masse d'acqua del golfo di Trieste e della laguna di Venezia in base ai
parametri chimico-fisici; studio su 10 anni di popolazioni fitoplanctoniche lungo la fascia costiera del Veneto e su 30 anni di campionamenti di popolazioni fito e zooplanctoniche nella laguna di Venezia; studio sulle comunità planctoniche multitrofiche nella laguna di Venezia; studio sulle comunità fito e zoobentoniche nella laguna di Venezia
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Emergent Properties Delineate Marine Ecosystem Perturbation and Recovery
No full textWhether there are common and emergent patterns from marine ecosystems remains an important question because marine ecosystems provide billions of dollars of ecosystem services to the global community, but face many perturbations with significant consequences. Here, we develop cumulative trophic patterns for marine ecosystems, featuring sigmoidal cumulative biomass (cumB)-trophic level (TL) and 'hockey-stick' production (cumP)-cumB curves. The patterns have a trophodynamic theoretical basis and capitalize on emergent, fundamental, and invariant features of marine ecosystems. These patterns have strong global support, being observed in over 120 marine ecosystems. Parameters from these curves elucidate the direction and magnitude of marine ecosystem perturbation or recovery; if biomass and productivity can be monitored effectively over time, such relations may prove to be broadly useful. Curve parameters are proposed as possible ecosystem thresholds, perhaps to better manage the marine ecosystems of the world
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