This study presents a comparative analysis of protected and exploited Mediterranean Sea food webs... more This study presents a comparative analysis of protected and exploited Mediterranean Sea food webs using standardized ecological models of two ecosystems: the Central-North Adriatic Sea (highly exploited) and the Miramare Natural Marine Reserve (Northern Adriatic Sea, protected since 1986). Food webs are analysed in terms of structural and functional traits including trophic levels, transfer efficiency, trophic role of species and keystoneness, trophic spectra and other synthetic ecological indicators. Our results highlight similarities between food webs of the Adriatic Sea, differences that are likely due to the impact of fishing and differences that should be related to other factors. Analysis of biomass distribution along functional groups and of trophic spectra indicates that protected area presents higher mean trophic level of the community, higher biomasses, lower production and generally lower transfer efficiency than fished area. Our results indicate that measures of food web complexity (system omnivory index and ascendency), as well as pelagic/demersal and fish/invertebrates biomass ratios are higher in the protected area than in exploited ecosystem due to fishing-induced changes. Thus, this study highlights that marine protected areas can efficiently contribute to maintain structural and functional traits of marine ecosystems.
Page 1. CLIMATE RESEARCH Clim Res Vol. 42: 1326, 2010 doi: 10.3354/cr00859 Published online May ... more Page 1. CLIMATE RESEARCH Clim Res Vol. 42: 1326, 2010 doi: 10.3354/cr00859 Published online May 20 1. INTRODUCTION Global Change (GC) is expected to have strong effects on the structure and function of both pelagic and coastal ecosystems. ...
Assessment of the Mediterranean marine environment, in terms of nutrient depletion and easterly d... more Assessment of the Mediterranean marine environment, in terms of nutrient depletion and easterly decreasing trophic gradients, requires full exploit of the knowledge and processes of the ecosystem dynamics.The three-dimensional model here proposed takes into account the phosphorus and nitrogen cycles coupled with the temporal and spatial hydrodynamical evolution.The food web considers, as primary producers, small autotrophs and large autotrophs uptaking on a multi-nutrient environment characterized by differential remineralizations of the detrital matter components. Grazing effects are modulated by herbivorous zooplankton response.The model is compared with the OCEAN-calibrated chlorophyll averages of the 1979–1985 Coastal Zone Color Scanner (CZCS) satellite data. This procedure validates the model biomass in the Western Mediterranean, which is 0.24 mg Chl m −3 when averaged yearly, with CZCS excess of about 10%, and in the Eastern Mediterranean, where the mean is 0.09 mg Chl m−3, with CZCS excess of 25%. The time series of the modelled results are well correlated with the CZCS estimates, with a higher value in the western than in the eastern basin.The temporal and spatial evolution of the biochemical patterns are studied. The effects of the implemented design on phosphorus and nitrogen cycles throughout the food chain are quantitatively followed and compared with results coming from specific cruises.Results about the vertically integrated biomasses are reported, giving an average of 2.7 g C m−2 for the total phytoplankton in the western basin and of 1.6 g C m−2 in the eastern one. The zooplanktonic biomass attains a mean value of 1.0 g C m−2 in the western basin and of 0.3 g C m−2 in the eastern one. Average productions accord with plankton abundances, with western primary and secondary productions, respectively, two and three times higher than the eastern ones.
The Mediterranean Sea is generally characterized by the presence of oligotrophic conditions, whic... more The Mediterranean Sea is generally characterized by the presence of oligotrophic conditions, which are more pronounced in its eastern part. The effects of physical and biological fluxes on the nitrogen and phosphorus distributions are here addressed by means of a box model. Numerical simulations obtained with realistic fluxes, as well as the analysis of the asymptotic behavior of the model support the hypothesis that inverse estuarine circulation is not sufficient to explain the oligotrophic regime. Conversely, it appears that the downward fluxes of organic matter play a major role in sustaining and stabilizing the oligotrophy as found in the observations. Indeed the trophic gradients between the western and the eastern Mediterranean arise as a consequence of the unbalance of the loads emitted in the basins, with greater inputs into the western, but, in any case, they are maintained in the long run by the biological pump.
In this work the flushing features of a tidal active coastal basin, the Venice lagoon, have been ... more In this work the flushing features of a tidal active coastal basin, the Venice lagoon, have been investigated. The water transport time scale (TTS) has been computed by means of both an eulerian and a lagrangian approach. The obtained results have been compared in order to identify the main differences between the two methods.The eulerian water transport time (WRT) scale has been computed through the definition of the remnant function of a passive tracer released inside the lagoon whereas the lagrangian water transport time (WTT) scale has been computed tracking the trajectories of simulated particles released inside the basin.Both the methodologies rely on computer modeling. A 2D hydrodynamic model based on the finite element method has been used. The model solves the shallow water equations on a spatial domain that represents the whole Adriatic Sea and the Venice lagoon.Numerical computations show that the two techniques, when applied to a tidal active coastal basin, characterized by a complex morphology and dynamic, are differently influenced by the tidal variability.In particular, the type and the phase of the tidal forcing at the beginning of the computation strongly influence the WTTs distribution within the basin. On the other hand, the WRTs computation is not affected by the tidal forcing variability.
An analysis of existing biochemical datasets, collected using different measurements methods, con... more An analysis of existing biochemical datasets, collected using different measurements methods, confirms peculiarities of the Mediterranean Sea, such as its oligotrophy, easterly decreasing gradients, and influence of hydrodynamics on the biochemical patterns. Thus assessment of this marine environment requires a model based on a three-dimensional characterization of the ecosystem dynamics. The model, which covers all the Mediterranean basin, conceptually takes into accounts the cycles of nitrogen and phosphorus through the detritus and food chains. It includes as major compartments dissolved inorganic nutrients, two pools of phytoplankton producers, one of zooplankton, and detritus. Dynamic of dissolved oxygen is also simulated. Simulations are presented and results from this conceptualization are reported.
A global sensitivity analysis is performed on a trophodynamic model of the Gulf of Trieste by usi... more A global sensitivity analysis is performed on a trophodynamic model of the Gulf of Trieste by using the Morris’ method. This screening method allows to highlight the most important processes in the system and to single out and rank the most relevant parameters of the model. The analysis is applied to a trophodynamic model specifically developed for the Gulf of Trieste, the northernmost part of the Adriatic Sea.In agreement with the specific ecological literature on the area of interest, the model considers two groups of phytoplankton (diatoms and nano-pico phytoplankton) and two groups of zooplankton (meso and microzooplankton). Heterotrophic bacteria are explicitly included in the model in order to simulate their role in DOC degradation and in phosphorus cycle, that is considered the limiting nutrient in the area of interest. The nutrient and carbon content in particulate organic matter and dissolved organic matter is also included in order to realistically reproduce the uncoupling of the nutrient and carbon cycles in the marine ecosystem. Model results reproduce fairly well the observed alternation of classical food chain and microbial food web as a result of the nutrient availability and the climatological factors used to force the system.The results of the global sensitivity analysis indicates that the most relevant parameters are those related to the growth formulations of the two phytoplankton groups, the total phosphorus in the system, the decay rate of particulate organic phosphorus and the mortality rate of bacteria. The analysis outlines that in spring and summer different processes within the two trophic pathways are dominant, and that while primary producers are mainly bottom–up controlled, bacteria experience both top–down and bottom–up controls.
This study illustrates a methodology that deals with three basic problems that concern the calibr... more This study illustrates a methodology that deals with three basic problems that concern the calibration of marine ecosystem models: (a) How many parameters can be calibrated? (b) Which subsets of parameters can be calibrated ? (c) How can the uncertainty in a given model output be estimated?The methodology is based on an a priori approach: this means that the results depend only on the structure of the model and on the set of variables which forms the data available for assimilation. The methodology is based on the computation of the sensitivities of the state variables to the model parameters, and enables one to analyze the role additional observations could play in constraining the model parameters. The methodology was applied to a one-dimensional (1D) primary production multinutrient model that describes the dynamics of pelagic ecosystem. The model describes nitrogen, phosphorus, and carbon cycles by means of a trophic chain constituted by two phytoplanktonic functional groups, one zooplanktonic pool and the detritus compartment. Nitrates, phosphates, and ammonia are considered as inorganic dissolved nutrients.Results show that the sensitivities of the majority of the parameters are strongly correlated and, therefore, only 5 of 43 parameters of our model could be accurately calibrated, even if daily measurements of nutrients and chlorophyll a were available for 1 year and at three different depths. Most of the state variables show the highest sensitivity to parameters related to the water temperature, phytoplankton growth, and phytoplankton mortality. The analysis of this case study, which, in our opinion, is representative of oligotrophic mid-latitude environments, suggests that water shading coefficient, optimal temperature coefficients for small phytoplankton, optimal temperature coefficient for large phytoplankton, a grazing parameter, and a parameter that describes the influence of water temperature on biological and chemical kinetics could be simultaneously and efficiently calibrated.Finally, indications about observational strategies are also given.
This study presents a comparative analysis of protected and exploited Mediterranean Sea food webs... more This study presents a comparative analysis of protected and exploited Mediterranean Sea food webs using standardized ecological models of two ecosystems: the Central-North Adriatic Sea (highly exploited) and the Miramare Natural Marine Reserve (Northern Adriatic Sea, protected since 1986). Food webs are analysed in terms of structural and functional traits including trophic levels, transfer efficiency, trophic role of species and keystoneness, trophic spectra and other synthetic ecological indicators. Our results highlight similarities between food webs of the Adriatic Sea, differences that are likely due to the impact of fishing and differences that should be related to other factors. Analysis of biomass distribution along functional groups and of trophic spectra indicates that protected area presents higher mean trophic level of the community, higher biomasses, lower production and generally lower transfer efficiency than fished area. Our results indicate that measures of food web complexity (system omnivory index and ascendency), as well as pelagic/demersal and fish/invertebrates biomass ratios are higher in the protected area than in exploited ecosystem due to fishing-induced changes. Thus, this study highlights that marine protected areas can efficiently contribute to maintain structural and functional traits of marine ecosystems.
Page 1. CLIMATE RESEARCH Clim Res Vol. 42: 1326, 2010 doi: 10.3354/cr00859 Published online May ... more Page 1. CLIMATE RESEARCH Clim Res Vol. 42: 1326, 2010 doi: 10.3354/cr00859 Published online May 20 1. INTRODUCTION Global Change (GC) is expected to have strong effects on the structure and function of both pelagic and coastal ecosystems. ...
Assessment of the Mediterranean marine environment, in terms of nutrient depletion and easterly d... more Assessment of the Mediterranean marine environment, in terms of nutrient depletion and easterly decreasing trophic gradients, requires full exploit of the knowledge and processes of the ecosystem dynamics.The three-dimensional model here proposed takes into account the phosphorus and nitrogen cycles coupled with the temporal and spatial hydrodynamical evolution.The food web considers, as primary producers, small autotrophs and large autotrophs uptaking on a multi-nutrient environment characterized by differential remineralizations of the detrital matter components. Grazing effects are modulated by herbivorous zooplankton response.The model is compared with the OCEAN-calibrated chlorophyll averages of the 1979–1985 Coastal Zone Color Scanner (CZCS) satellite data. This procedure validates the model biomass in the Western Mediterranean, which is 0.24 mg Chl m −3 when averaged yearly, with CZCS excess of about 10%, and in the Eastern Mediterranean, where the mean is 0.09 mg Chl m−3, with CZCS excess of 25%. The time series of the modelled results are well correlated with the CZCS estimates, with a higher value in the western than in the eastern basin.The temporal and spatial evolution of the biochemical patterns are studied. The effects of the implemented design on phosphorus and nitrogen cycles throughout the food chain are quantitatively followed and compared with results coming from specific cruises.Results about the vertically integrated biomasses are reported, giving an average of 2.7 g C m−2 for the total phytoplankton in the western basin and of 1.6 g C m−2 in the eastern one. The zooplanktonic biomass attains a mean value of 1.0 g C m−2 in the western basin and of 0.3 g C m−2 in the eastern one. Average productions accord with plankton abundances, with western primary and secondary productions, respectively, two and three times higher than the eastern ones.
The Mediterranean Sea is generally characterized by the presence of oligotrophic conditions, whic... more The Mediterranean Sea is generally characterized by the presence of oligotrophic conditions, which are more pronounced in its eastern part. The effects of physical and biological fluxes on the nitrogen and phosphorus distributions are here addressed by means of a box model. Numerical simulations obtained with realistic fluxes, as well as the analysis of the asymptotic behavior of the model support the hypothesis that inverse estuarine circulation is not sufficient to explain the oligotrophic regime. Conversely, it appears that the downward fluxes of organic matter play a major role in sustaining and stabilizing the oligotrophy as found in the observations. Indeed the trophic gradients between the western and the eastern Mediterranean arise as a consequence of the unbalance of the loads emitted in the basins, with greater inputs into the western, but, in any case, they are maintained in the long run by the biological pump.
In this work the flushing features of a tidal active coastal basin, the Venice lagoon, have been ... more In this work the flushing features of a tidal active coastal basin, the Venice lagoon, have been investigated. The water transport time scale (TTS) has been computed by means of both an eulerian and a lagrangian approach. The obtained results have been compared in order to identify the main differences between the two methods.The eulerian water transport time (WRT) scale has been computed through the definition of the remnant function of a passive tracer released inside the lagoon whereas the lagrangian water transport time (WTT) scale has been computed tracking the trajectories of simulated particles released inside the basin.Both the methodologies rely on computer modeling. A 2D hydrodynamic model based on the finite element method has been used. The model solves the shallow water equations on a spatial domain that represents the whole Adriatic Sea and the Venice lagoon.Numerical computations show that the two techniques, when applied to a tidal active coastal basin, characterized by a complex morphology and dynamic, are differently influenced by the tidal variability.In particular, the type and the phase of the tidal forcing at the beginning of the computation strongly influence the WTTs distribution within the basin. On the other hand, the WRTs computation is not affected by the tidal forcing variability.
An analysis of existing biochemical datasets, collected using different measurements methods, con... more An analysis of existing biochemical datasets, collected using different measurements methods, confirms peculiarities of the Mediterranean Sea, such as its oligotrophy, easterly decreasing gradients, and influence of hydrodynamics on the biochemical patterns. Thus assessment of this marine environment requires a model based on a three-dimensional characterization of the ecosystem dynamics. The model, which covers all the Mediterranean basin, conceptually takes into accounts the cycles of nitrogen and phosphorus through the detritus and food chains. It includes as major compartments dissolved inorganic nutrients, two pools of phytoplankton producers, one of zooplankton, and detritus. Dynamic of dissolved oxygen is also simulated. Simulations are presented and results from this conceptualization are reported.
A global sensitivity analysis is performed on a trophodynamic model of the Gulf of Trieste by usi... more A global sensitivity analysis is performed on a trophodynamic model of the Gulf of Trieste by using the Morris’ method. This screening method allows to highlight the most important processes in the system and to single out and rank the most relevant parameters of the model. The analysis is applied to a trophodynamic model specifically developed for the Gulf of Trieste, the northernmost part of the Adriatic Sea.In agreement with the specific ecological literature on the area of interest, the model considers two groups of phytoplankton (diatoms and nano-pico phytoplankton) and two groups of zooplankton (meso and microzooplankton). Heterotrophic bacteria are explicitly included in the model in order to simulate their role in DOC degradation and in phosphorus cycle, that is considered the limiting nutrient in the area of interest. The nutrient and carbon content in particulate organic matter and dissolved organic matter is also included in order to realistically reproduce the uncoupling of the nutrient and carbon cycles in the marine ecosystem. Model results reproduce fairly well the observed alternation of classical food chain and microbial food web as a result of the nutrient availability and the climatological factors used to force the system.The results of the global sensitivity analysis indicates that the most relevant parameters are those related to the growth formulations of the two phytoplankton groups, the total phosphorus in the system, the decay rate of particulate organic phosphorus and the mortality rate of bacteria. The analysis outlines that in spring and summer different processes within the two trophic pathways are dominant, and that while primary producers are mainly bottom–up controlled, bacteria experience both top–down and bottom–up controls.
This study illustrates a methodology that deals with three basic problems that concern the calibr... more This study illustrates a methodology that deals with three basic problems that concern the calibration of marine ecosystem models: (a) How many parameters can be calibrated? (b) Which subsets of parameters can be calibrated ? (c) How can the uncertainty in a given model output be estimated?The methodology is based on an a priori approach: this means that the results depend only on the structure of the model and on the set of variables which forms the data available for assimilation. The methodology is based on the computation of the sensitivities of the state variables to the model parameters, and enables one to analyze the role additional observations could play in constraining the model parameters. The methodology was applied to a one-dimensional (1D) primary production multinutrient model that describes the dynamics of pelagic ecosystem. The model describes nitrogen, phosphorus, and carbon cycles by means of a trophic chain constituted by two phytoplanktonic functional groups, one zooplanktonic pool and the detritus compartment. Nitrates, phosphates, and ammonia are considered as inorganic dissolved nutrients.Results show that the sensitivities of the majority of the parameters are strongly correlated and, therefore, only 5 of 43 parameters of our model could be accurately calibrated, even if daily measurements of nutrients and chlorophyll a were available for 1 year and at three different depths. Most of the state variables show the highest sensitivity to parameters related to the water temperature, phytoplankton growth, and phytoplankton mortality. The analysis of this case study, which, in our opinion, is representative of oligotrophic mid-latitude environments, suggests that water shading coefficient, optimal temperature coefficients for small phytoplankton, optimal temperature coefficient for large phytoplankton, a grazing parameter, and a parameter that describes the influence of water temperature on biological and chemical kinetics could be simultaneously and efficiently calibrated.Finally, indications about observational strategies are also given.
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