Site Selection Criteria for Off-Shore Mussel Cultivation Use: A Modelling Approach

In the last decade, the Mediterranean mussel production in Italy has been steadily increasing, reaching in 2002 the 7% of the worldwide production. This trend is mainly due to the increase in landings from aquaculture, which in 2002 accounted for about 70% of the country annual production. Despite this growth, the development of off-shore mussel culture activities still encounters a number of constraints concerned with sustainability and environmental impacts. This work presents the developement of a mathematical model which aims at describing the impact of farmed mussels on phytoplankton concentration. The model was applied to study the sustainability of mussel culture activities along the western Adriatic coast. Simulation results indicate that, during a critical period of the rearing cycle, phytoplankton concentration could be impacted by the grazing of farmed mussels. Model results were discussed on the basis of considerations on energy requirements to sustain mussel growth. The approach presented can give useful indications related to farms sizes and locations

LCA for territorial metabolism analysis: An application to organic waste management planning

The management of biodegradable waste in landfills is associated to a range environmental impacts and refers to a linear model regarded as unsustainable. At the same time, many agricultural and urban soils present low organic matter content. Composting is emerging as a good practice for converting organic waste into a new resource able to improve soil properties, thus providing regulation Ecosystem Services. Considering a territorial metabolism perspective, this work discusses the potential contribution to regional planning of a transferable methodology for quantifying environmental impacts and benefits associated to waste management, based on a combined use of Life Cycle Assessment and Geographic Information Systems, and considering Ecosystem Services deriving from the application of compost in agricultural soils. The approach was tested through a site-dependent analysis based on primary data, referring to year 2019 and focusing on the Veneto Region, Italy. Results indicate that direct benefits associated to the use of compost and the thermal energy to district heating are compensating from 29 % to 51 % of the impacts associated to compost production, while waste transports represent the largest share of the impacts, covering between 52 % and 78 % of the total flows considered. The proposed methodology is applied for comparing the reference condition to alternative scenarios, in the perspective of providing support in Strategic Environmental Assessment procedures. In this context, results shown markedly lower impacts associated to compost production, with respect to organic waste treatment, for 5 out of 6 of the considered categories (freshwater eutrophication 100:1, climate change 5:1), with the notable exception of water resource depletion. Scenarios produced are discussed with respect to the choice between centralized and non-centralized plants, and the characterization of potential benefits at the territorial scale associated to compost use for urban green infrastructures. With respect to this latter point, results showed an underdeveloped use of compost-related ES flow, compared to its capacity, suggesting an interest for further research aimed at estimating compost requirements by urban and peri-urban soils

Interactions of cage aquaculture in Nile Delta lakes: Insights from field data and models

In this paper, we present a cost-effective approach to the assessment of the impact of fish cage culture in transitional water bodies characterized by limited exchanges with the sea. The approach, previously applied to marine coastal areas, is based on two steps: (1) the application of a Lagrangian model, driven by purposely collected data concerning the local hydrodynamic, for an "a priori'' simulation of the dispersion of uneaten feed and fecal material from a cage; (2) the collection of a set of field data concerning both water column and sediment indicators, sensitive to the release of organic matter from a cage, along a transect: the latter is determined on the basis of the results provided by the dispersion model. The methodology was tested at a seabass/seabream farm located in a coastal lake on the Nile Delta, namely Lake Maryut. Model results indicated that the area impacted by the cage is relatively small, about 5 m from the edge of the cage: this finding was later corroborated by field observations. As far as the water column is concerned, Dissolved Inorganic Nitrogen was found to be higher near the farm. The most sensitive sediment indicators were found to be surface sediment TOC, and benthic macrofauna abundances, which were, respectively, higher and lower in the proximity of the farm. These findings suggest that a cost-effective monitoring programme of the environmental impact of intensive aquaculture could be implemented in Egyptian coastal Lakes, thus providing a science-based support to the implementation of the ecosystem approach to aquaculture in these important ecosystems. (C) 2016 Elsevier B.V. All rights reserved

Site Suitability for Finfish Marine Aquaculture in the Central Mediterranean Sea

Farm site selection plays a critical role in determining the productivity, environmental impact, and interactions of aquaculture activities with ecosystem services. Satellite Remote Sensing (SRS) provide spatially extensive datasets at high temporal and spatial resolution, which can be useful for aquaculture site selection. In this paper we mapped a finfish aquaculture Suitability Index (SI) applying the Spatial Multi-criteria Evaluation (SMCE) methodology. The robustness of the outcome of the SMCE was investigated using Uncertainty Analysis (UA), and in parallel we evaluate a set of alternative scenarios, aimed at minimizing the subjectivity associated with the decision process. The index is based on the outputs of eco-physiological models, which were forced using time series of sea surface temperature data, and on data concerning Significant Wave Height (SWH), distance to harbor, current sea uses, and cumulative impacts. The methodology was applied to map the suitability for farming of European seabass (Dicentrarchus labrax) and gilthead seabream (Sparus aurata) within the Italian Economic Exclusive Zone (EEZ), under three scenarios: Blue Growth, Economic and Environment. Tyrrhenian and Ionian coastal areas were found to be more suitable, compared to the Northern Adriatic and southern Sicilian ones. In the latter, and in the western Sardinia, the index is also affected by higher uncertainty. The application presented suggests that SRS data could play a significant role in designing the Allocated Zones for Aquaculture, assisting policy makers and regulators in including aquaculture within maritime spatial planning

Linking food web functioning and habitat diversity for an ecosystem based management: A Mediterranean lagoon case-study

We propose a modelling approach relating the functioning of a transitional ecosystem with the spatial extension of its habitats. A test case is presented for the lagoon of Venice, discussing the results in the context of the application of current EU directives. The effects on food web functioning due to changes related to manageable and unmanageable drivers were investigated. The modelling procedure involved the use of steady-state food web models and network analysis, respectively applied to estimate the fluxes of energy associated with trophic interactions, and to compute indices of food web functioning. On the long term (hundred years) temporal scale, the model indicated that the expected loss of salt marshes will produce further changes at the system level, with a lagoon showing a decrease in the energy processing efficiency. On the short term scale, simulation results indicated that fishery management accompanied by seagrass restoration measures would produce a slight transition towards a more healthy system, with higher energy cycling, and maintaining a good balance between processing efficiency and resilience. Scenarios presented suggest that the effectiveness of short term management strategies can be better evaluated when contextualized in the long term trends of evolution of a system. We also remark the need for further studying the relationship between habitat diversity and indicators of food web functioning

Early Diagenesis in Sediments of the Venice Lagoon (Italy) and Its Relationship to Hypoxia

This work focuses on sediments of a shallow water lagoon, located in a densely populated area undergoing multiple stressors, with the goal of increasing the understanding of the links between diagenetic processes occurring in sediments, the dynamics of dissolved oxygen (DO) in the water column, and potential consequences of hypoxia. Sediment data were collected over three consecutive years, from 2015 to 2017, during spring-summer, at five stations. Measured variables included: sediment porosity, grain size and organic carbon content, porewater microprofiles of O-2, pH and H2S, porewater profiles of dissolved inorganic carbon (DIC), total alkalinity (TA), NH4+, NO3-, dissolved Fe, and SO42-. In addition, long-term time series of oxygen saturations in the water column (years 2005-2017) were utilized in order to identify the occurrence and duration of hypoxic periods. The results show that the median DO saturation value in summer months was below 50% (around 110 mu mol L-1), and that saturation values below 25% (below the hypoxic threshold) can persist for more than 1 week. Sediment stations can be divided in two groups based on their diagenetic intensity: intense and moderate. At these two groups of stations, the average DIC net production rates, estimated trough a steady-state model (Profile) were, respectively, of 2.8 and 1.0 mmol m(-2) d(-1), SO42- consumption rates were respectively 1.6 and 0.4 mmol m(-2) d(-1), while diffusive oxygen uptake fluxes, calculated from the sediment microprofile data, were of 28.5 and 17.5 mmol m(-2) d(-1). At the stations characterized by intense diagenesis, total dissolved sulfide accumulated in porewaters close to the sediment-water interface, reaching values of 0.7 mM at 10 cm. Considering the typical physico-chemical summer conditions, the theoretical time required to consume oxygen down to the hypoxic level by sediment oxygen demand ranges between 5 and 18 days, in absence of mixing and re-oxygenation. This estimation highlights that sediment diagenesis may play a crucial role in triggering and maintaining hypoxia of lagoon waters during the summer season in specific high intensity diagenesis zones. This role of the sediment could be enhanced by changes in regional climate conditions, such as the increase in frequency of summer heat waves

Testing a Model of Pacific Oysters’ (Crassostrea gigas) Growth in the Adriatic Sea: Implications for Aquaculture Spatial Planning

Assessing the potential biomass yield is a key step in aquaculture site selection. This is challenging, especially for shellfish, as the growth rate depends on both trophic status and water temperature. Individual ecophysiological models can be used for mapping potential shellfish growth in coastal areas, using as input spatial time series of remotely sensed SST and chlorophyll-a. This approach was taken here to estimate the potential for developing oyster (Crassostrea gigas) farming in the western Adriatic Sea. Industry relevant indicators (i.e., shell length, total individual weight) and days required to reach marketable size were mapped using a dynamic energy budget model, finetuned on the basis of site-specific morphometric data collected monthly for a year. Spatially scaledup results showed that the faster and more uniform growth in the northern Adriatic coastal area, compared with the southern one, where chlorophyll-a levels are lower and summer temperatures exceed the critical temperature limit for longer periods. These results could be used in planning the identification of allocated zones for aquaculture, (AZA), taking into account also the potential for farming or co-farming C. gigas. In perspective, the methodology could be used for getting insights on changes to the potential productivity indicators due to climatic changes

Testing a model of pacific oysters’ (Crassostrea gigas) growth in the adriatic sea: Implications for aquaculture spatial planning

Assessing the potential biomass yield is a key step in aquaculture site selection. This is challenging, especially for shellfish, as the growth rate depends on both trophic status and water temperature. Individual ecophysiological models can be used for mapping potential shellfish growth in coastal areas, using as input spatial time series of remotely sensed SST and chlorophyll-a. This approach was taken here to estimate the potential for developing oyster (Crassostrea gigas) farming in the western Adriatic Sea. Industry relevant indicators (i.e., shell length, total individual weight) and days required to reach marketable size were mapped using a dynamic energy budget model, finetuned on the basis of site-specific morphometric data collected monthly for a year. Spatially scaled-up results showed that the faster and more uniform growth in the northern Adriatic coastal area, compared with the southern one, where chlorophyll-a levels are lower and summer temperatures exceed the critical temperature limit for longer periods. These results could be used in planning the identification of allocated zones for aquaculture, (AZA), taking into account also the potential for farming or co-farming C. gigas. In perspective, the methodology could be used for getting insights on changes to the potential productivity indicators due to climatic changes

Ecosystem functioning and ecological status in the Venice lagoon, which relationships?

The implementation of management measures for improving the ecological status within an Ecosystem Based Management approach represents one the of the main challenges in coastal and transitional water environments. In general terms, ecological status and ecosystem functioning are expected to be positively associated, being good ecological processes a sort of prerequisite for the ecosystem health, but often relationships between ecosystem functioning indicators and the metrics used to define ecological status resulted to be rather puzzling. Moreover, the Biological Quality Elements (BQEs) do not show a consistent response to the changes in the ecosystem. This situation does not allow to recognize where interventions are really needed, hindering the definition of effective management strategies. In the present paper, a spatially explicit food web model of the Venice lagoon (with the resolution of 300 m) is used to simulate changes in the ecological status and related them to different management scenarios. Functional changes in the food web were investigated by comparing values of a set of 12 indicators derived by the ecological network analysis. In general, results highlighted on one hand the need for more discussion about the implementation of the WFD, at least in complex and spatially heterogeneous transitional waters environments, as the Venice lagoon; on the other, results remark the opportunity to support the BQEs monitoring with an ecological modelling approach. These models are certainly not the panacea for addressing questions about the environmental management, as they have inherent uncertainties (on parameters, structure, processes etc.); however, they can prove useful for selecting among different policy choices, since they offer the opportunity to simulate the mean effects, preliminarily verifying the efficacy of the proposed interventions

Petri nets for modelling and analysing trophic networks

We consider trophic networks, a kind of networks used in ecology to represent feeding interactions (what-eats-what) in an ecosys- tem. We observe that trophic networks can be naturally modelled as Petri nets and this suggests the possibility of exploiting Petri nets for the analysis and simulation of trophic networks. Some preliminary steps in this directions and some ideas for future development are presented