1,721,072 research outputs found
Tolerance landscapes can be used to predict species-specific responses to climate change beyond the marine heatwave concept: Using tolerance landscape models for an ecologically meaningful classification of extreme climate events
No full textTo predict the responses of organisms to changes in intensity and frequency of heatwaves, it is essential to gain a
thorough understanding of how organisms respond to temperature exposure. Species-specific curves are more
informative, yet more difficult to ascertain, than the generic heatwave definition (five days or more at a temperature
above the 90% percentile) when addressing mortality risk and should be included when predicting
thermal risks. The thermal tolerance of organisms is dictated by a combination of exposure intensity and
duration: the aim of this study was to build a ‘tolerance landscape’ model, based on exposure thresholds to a
potentially stressful temperature range, for the commercially important clam Ruditapes philippinarum using ten
years of summer temperature time series in four lagoons in the Northern Adriatic, where this species is being
commercially farmed. The model is based on a log-linear relationship between LT50 and exposure time. The two
model parameters, i.e. the lethal temperature at 1 min exposure (CTmax), and the temperature sensitivity
parameter (z) were estimated on the basis of a systematic literature search. Best-fitting values, i.e. CTmax = 54.5
(±2.3) and z = - 5.72 ◦C (±0.66) are within the ranges found for other bivalves. Results show that the mortality
threshold was exceeded for most lagoons in summertime in 2015, 2017 and 2018 suggesting that the risk of
exceeding the mortality threshold is increasing, due to an increase in frequency and duration of extreme temperature
events. Comparisons with the generic ‘marine heatwave’ definition showed that, while in some occasions
‘heatwaves’ occurred that were not risky for R. philippinarum, in one case the model identified a time period
of mortality risk that would not have been classified under the generic ‘heatwave’ definition. These mismatches
suggest that tolerance curves can be a good addition to productivity and site selection models, incorporating a
metric of species-specific risk that can be used to predict the consequences of climate change on fishery and
aquaculture, and can find their place in conservation and restoration toolkits for forecasting changes in habitat
suitability under future climate scenarios
Data assimilation as a key step towards the implementation of an efficient management of dissolved oxygen in land-based aquaculture
Full text linkA data assimilation (DA) methodology, e.g. the continuous-discrete Kalman filter (CD-KF), was applied to the assimilation of dissolved oxygen data, in order to obtain a dynamic estimation of the oxygen demand in a land-based aquafarm. The CD-KF was implemented on a dynamic model, which included as state variables the concentration of dissolved oxygen (DO) and fish respiration rate: the latter was considered as a non-observable stochastic variable. The model was applied to a 1-month long set of observations collected at a raceway rainbow trout farm, including (1) hourly time series of water temperature and dissolved oxygen concentration in the raceway influent and effluent and (2) a daily time series of fish number and fish weight distribution. The results show that the assimilation of DO data led to a dynamic estimate of DO demand which showed changes in the daily mean and the daily pattern: these were related to changes in the feeding regime. Furthermore, the methodology provided accurate short-term predictions of the DO concentration also in the presence of short-term fluctuations, which would be very difficult to relate to external forcings in a mechanistic model. These findings indicate that DA could be effectively used to design and implement efficient and robust control systems for optimizing the oxygen supply, thus contributing to the implementation of Precision Fish Farming in land-based aquafarms
Estimating oxygen consumption of rainbow trout (Oncorhynchus mykiss) in a raceway: a precision fish farming approach
Full text linkThe Precision Fish Farming (PFF) approach was applied to the estimation of fish oxygen consumption of rainbow trout in a raceway farm. A dynamic model, simulating the evolution of Dissolved Oxygen concentration, was identified: the daily oscillation of fish oxygen consumption rate was simulated by means of a sinusoidal function. The model was applied to the data set collected during a four-week field study, which was carried out in July 2019. Water temperature and Dissolved Oxygen concentration were measured with an hourly frequency in farm influent and effluent. Fish biomass was monitored on a daily basis by combining the data provided by a state-of-the art system for non-invasive estimation of fish weight distribution with mortality counting. The monitoring period was partitioned into two time-windows, as fish was not fed during the first two weeks. These windows were further partitioned into a calibration and validation set. Three model parameters, i.e. the average daily respiration rate, the amplitude of its daily oscillation, and its phase were estimated by fitting the model output to the time series of DO concentration in the effluent. The results of the calibration show that: 1) the daily average oxygen consumption rate is consistent with the literature; 2) the amplitude of the daily oscillation when fish is regularly fed is more than twice that estimated for fasting fish. The results of the validation suggest that the model could be used to implement a cost-effective automatic control of oxygen supply, based on the short-term prediction of oxygen deman
Determination by infrared spectroscopy of triacetin content in diesel: A tool for countering designer fuel frauds
Full text linkTaxation on fuels is an important share of fiscal revenues of most countries. Among the most abundant petrochemicals in the market, gas oil, or diesel, is particularly important, and it is commonly used as fuel for heating systems and for vehicles such as cars and trucks, but also for farm machinery and boats. Due to its wide range of applications and to the fact that most of the final price of diesel is made up of taxes, the phenomenon of designer fuels is increasingly common. Designer fuels are fuels in which some chemical and physical characteristics are fraudulently modified in order to classify them as other goods, e.g. lubricating oils or solvents, which are subject to lower or no taxes. Triacetin is a frequently employed additive for changing the classification of heavy distillates into lubricant oils, and it is therefore important, for a customs office, to be able to assess its presence as quickly and easily as possible, both inside or outside the laboratory. This paper proposes a method based on IR spectroscopy for the detection and quantification of triacetin in diesel, in an inexpensive but effective way. The analytical protocol presented allows a limit of quantification as low as 0.3% v/v, it is robust, precise and accurate enough to yield data useful for the customs agent to take decisions without further lengthy procedures
From feed to fork: life cycle assessment on an Italian rainbow trout (Oncorhynchus mykiss) supply chain
No full textThe body of knowledge in trout farming sustainability is still not exhaustive, mainly due to the variability in the production system and in the methodological approach and partly to data quality issues. As such, Life Cycle Assessment (LCA) was applied to a trout supply chain located in Northern Italy, basing the inventory dataset almost entirely on primary data gathered from producers and extending the system boundaries beyond the conventional farm-gate, in order to include: phase 1. feed production; phase 2. trout grow-out in freshwater flow-through systems; phase 3. trout processing into foodstuff; phase 4. fish by-products processing into pet-food ingredients.
The results highlight that, while resource sharing in phase 3 is a winning practice and leads to decrease in environmental impacts, the other three phases present crucial aspects which require either technological or methodological improvements. Firstly, the relative contribution of feed ingredients is very high, with respect to all the impact categories considered. Secondly, despite on-farm effluents account alone for 92% of downstream river eutrophication (phase 2), data from rivers environmental monitoring prove this result to be an overestimation, due to the fact that LCA does not adequately cover proximate ecological concerns as yet. Finally, the energy demand for the recovery and recycling of the fish by-products (phase 4) is high, causing a high impact on global warming, terrestrial ecotoxicity, freshwater ecotoxicity and cumulative energy demand.
In order to improve the overall sustainability of the supply chain, changes are required mainly in the feed production and by-product processing phases. As far as the former is concerned, a winning strategy would be the formulation of feeds with more sustainable feed ingredients and further improvements in the feed quality (palatability, digestibility, nutritional content). In regard to the latter, more attention should be paid towards the source and amount of energy consumed. For instance, the use of renewable energy sources might be coupled with an improved insulation of the facilities and the use of less energivorous machineries/processes
Modelling interactions between mussel farm biodeposition, sediment biogeochemistry and nitrogen recycling in the northern Adriatic sea (Italy)
No full textA bioenergetic model to address carbon sequestration potential of shellfish farming: example from Ruditapes philippinarum in the Venice lagoon
Full text linkShellfish are increasingly been looked at as sustainable food sources that provide additional ecosystem services. However, their role as CO2 sinks or sources is still debated. To quantify it, shell accretion dynamics should be accounted for. However, the shell component is usually calculated with allometric scaling, in most bivalve models. With this study, shell accretion was added to a bioenergetic model of the Manilla clam (Ruditapes philippinarum), and a parameter linking assimilated energy towards shell growth (KSH) was calibrated for four sites, where clams from the same cohort were monitored during a transplant experiment. The model was then used to calculate CO2 fluxes resulting from respiration and shell calcification, taking into account CaCO3 stocked in the shell and CO2 emission. The findings show that KSH varied slightly among sites and that clams played a role as a moderate sink of CO2 over a whole year. CO2 fluxes were characterized by a seasonal variability: clams were net sources in wintertime and sinks in summer time, suggesting the need of accounting for seasonality and growth should shellfish farming be included in carbon markets
A unified approach to the modelling of the Venice Lagoon–Adriatic Sea ecosystem
No full textIn this paper, a first attempt at analysing the macronutrients’ mass balance between the north Adriatic coastal sea and the
lagoon of Venice by means of a nested and coupled model is presented. The hydrodynamic part of the model simulates
the evolution of the sea-surface elevation and of the three-dimensional field of velocity, temperature, salinity and density.
Tides, winds, river discharges, thermal and evaporative fluxes are included as forcings. Two models are nested in order
to handle the correct spatial scales. The first one, with a resolution of about 10 km, is able to describe the basin and
sub-basin scale hydrodynamical features; the second one, with a resolution of 1·2 km, describes the interactions between
the open sea and the lagoon. This last circulation model has been coupled with a simple primary production submodel,
in order to investigate the short-term dynamic of the ecosystem during spring time. Results show that, in some instances,
the primary production can be sustained by macronutrients’ fluxes coming from the coastal area.Published483-4923.7. Dinamica del clima e dell'oceanoJCR Journalope
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
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