Cosimo Solidoro

End-To-End Models for the Analysis of Marine Ecosystems: Challenges, Issues, and Next Steps

Abstract There is growing interest in models of marine ecosystems that deal with the effects of climate change through the higher trophic levels. Such end-to-end models combine physicochemical oceanographic descriptors and organisms ranging from microbes to higher-trophic-level (HTL) organisms, including humans, in a single modeling framework. The demand for such approaches arises from the need for quantitative tools for ecosystem-based management, particularly models that can deal with bottom-up and top-down controls that operate simultaneously and vary in time and space and that are capable of handling the multiple impacts expected under climate change. End-to-end models are now feasible because of improvements in the component submodels and the availability of sufficient computing power. We discuss nine issues related to the development of end-to-end models. These issues relate to formulation of the zooplankton submodel, melding of multiple temporal and spatial scales, acclimation and adaptation, behavioral movement, software and technology, model coupling, skill assessment, and interdisciplinary challenges. We urge restraint in using end-to-end models in a true forecasting mode until we know more about their performance. End-to-end models will challenge the available data and our ability to analyze and interpret complicated models that generate complex behavior. End-to-end modeling is in its early developmental stages and thus presents an opportunity to establish an open-access, community-based approach supported by a suite of true interdisciplinary efforts.

Current state, scales of variability, and trends of biogeochemical properties in the northern Adriatic Sea

[1] This paper illustrates the main results of a statistical analysis performed on a data set obtained by integrating experimental observations collected during many oceanographic research projects on the northern Adriatic Sea (NAS). The observations cover the last 20 years and provide a robust base for the assessment of the current state and scales of variability for temperature, salinity, nutrients, dissolved oxygen, and chlorophyll. The results confirmed a clear seasonal cycle and marked spatial gradients for most parameters in all seasons. The largest proportion of the river Po input flows south along the coast, but significant eastward freshwater fluxes are also present in all seasons, more markedly in winter. The coastal belt south of the Lagoon of Venice is the most eutrophic area, mainly because of river inputs, while an oligotrophic condition prevails along the eastern part of the basin. Small-scale structures, including eddies and jets, are permanent features of the system. In order to test the existence of significant trends of variation in the physical and biogeochemical parameters, the data set has been enlarged by including observations from 1976. Analyses of trends over 30 years show an increase in salinity, which might be a consequence of both reduced outflows from rivers and a more sustained inflow of water along eastern coast, and a clear reduction in concentrations of phosphate and ammonia in coastal areas, probably due to new regulations regarding the control of nutrient loads and possibly suggesting the occurrence of cultural oligotrophication. No decrease is instead observed for concentration of nitrate.

Managing the rearing of Tapes philippinarum in the lagoon of Venice: a decision support system.

The paper illustrates a multicriteria approach for the rational choice of the areas to be dedicated to extensive aquaculture in a coastal basin. Areas are selected by combining spatial information, such as healthiness and depth, with the results of a 3D model, which simulates the dynamics of the primary production and that of the species to be reared. The approach has been applied to the rearing of the bivalve Tapes philippinarum in the lagoon of Venice. The areas more suitable for rearing activities have been identified, and the relation between yield and seeding density is discussed.

Modelling macroalgae (Ulva rigida) in the Venice lagoon: Model structure identification and first parameters estimation

Abstract The paper describes the definition and a first parametrization of a dynamic model of macroalgae ( Ulva rigida ) population. Based on specific literature, a two-step kinetic scheme is selected for modelling growth and uptake of nitrogen and, therefore, the intratissual concentration of nitrogen has been considered as a state variable of the model. Accordingly, Ulva r. growth rate depends on the concentration of phosphorus in the external medium and on the intratissual nitrogen concentration, which influences, in turn, the uptake rates of reduced and oxidized nitrogen. The influences of temperature and light intensity on Ulva r. photosynthetic activity are also discussed. The dynamics of dissolved oxygen has also been modelled and a specific mortality rate, depending on dissoved oxygen, has been adopted. The model has proved to be qualitatively consistent with the available literature, while a first parametrization yields results in quantitative agreement with short term laboratory experiments, regarding samples collected in the lagoon of Venice. The model has been applied to data sets collected in the lagoon of Venice and is capable of reproducing the main features of the seasonal dynamic of Ulva r. These results prompted its inclusion in a comprehensive 3D transport-water quality model of the Venice lagoon ecosystem.

Addressing Sustainability of Clam Farming in the Venice Lagoon

The clam fishing and aquaculture system in the Venice Lagoon still appears insufficiently resilient to buffer external and internal perturbations, such as productivity fluctuations, unregulated fishing, and market related dynamics, despite the efforts of regional and local authorities to achieve the sustainable development. According to the System Approach Framework (SAF), based on previous studies and stakeholder interactions, we developed a model integrating ecological, social, and economic (ESE) aspects. We chose the aspects necessary to represent the essential dynamics of major ecological, social, and economic clam farming system components to project the consequences of implementing alternative management policies and to address the ecological and social carrying capacity. Results of the simulations suggest that a properly managed farming system can sustain an acceptable income and support the local community, while reducing negative environmental impacts, social conflicts, and consumer health risks and improving system resilience. The results highlight the importance of an interdisciplinary, participatory, and adaptive approach in planning the management of this important renewable resource.

Ecological and economic considerations on fishing and rearing of Tapes phillipinarum in the lagoon of Venice

A population dynamic model for Tapes philippinarum has been developed, using experimental data for the estimation of mortality, and literature information for recruitment. The population dynamic model has been coupled to a eco-physiological model of T. philippinarum previously developed, in order to simulate the evolution of individual size and number of individuals in each age class. The resulting age-size class model has been used to analyse the implication of different scenarios of fishing/harvesting of the bivalve in the lagoons of the Northern Adriatic Sea, where fishery and aquaculture represent important economic activities. Ten years long simulations have been performed, in which initial density, harvesting efficiency, minimum harvested size, were varied. Comparisons between the different strategies are made in term of total yields and bio-economic income. The model gives suggestions on the optimal fishing effort, in case of fishery, and on optimal seeding size and seeding moment, in case of aquaculture. A discussion of model results provides indications on harvesting policies which are appropriate from ecological-economical point of view. The final result is that economically more profitable strategies coincide with ecologically more conservative policies.

A finite element ecological model: a first application to the Venice Lagoon

Abstract A Finite Element Ecological Model (FEEM) has been set up by fully coupling a primitive equation finite element hydrodynamic model (FEM) to an ecological model derived from EUTRO, the ecological submodel contained in the water quality model WASP, released by US-EPA. The work required the ‘decoupling’ of EUTRO from WASP and its transformation into a standalone program, the testing of such a structure versus the results obtained by running the WASP in the 0D version, the improvement of its parameterisation up to the inclusion of zooplankton as a dynamic variable explicitly modelled, the definition of an interface module, and the actual coupling of the improved ecological module and the hydrodynamic primitive equation model. The integrated model has then been applied, as a first test, to the Venice Lagoon (VELFEEM). To this aim idealised forcings (tide, meteo) have been used together with actual field data (river discharge, nutrient loadings) to run simulations over a one-year period. Analysis of the results shows that the model is numerically stable, variations in the state variables are consistent, and nutrients, plankton and oxygen evolves in space and time in a ecologically coherent way. Main features of the lagoon, namely oxygen seasonal evolution and dispersion of nutrients from the point sources are qualitatively reproduced. An additional result is that the improved version of the 0D ecological submodel has been organised as an independent module which can be run by a single subroutine call, and therefore can be easily integrated in any structure and coupled to any hydrodynamic model. The coupling here presented demonstrates the ease of such an integration.

The Extended Kalman Filter (EKF) as a tool for the assimilation of high frequency water quality data

The Extended Kalman Filter (EKF) was applied to the analysis of high frequency field measurements of dissolved oxygen (DO), water temperature, salinity, collected by multiparametric sensors in the lagoon of Venice. This paper focuses on the practical aspects of the implementation of the EKF as a data assimilation technique and does not deal with the problems associated with the identification of the model. In this regard, the EKF has proved to be a useful tool for the updating of the estimates of the parameters of a simple DO-chlorophyll model, which can be used for linking the high frequency data to meteorological forcings, such as solar radiation and wind, and to other low frequency measurements of water quality parameters, such as the concentrations of Chlorophyll a and nutrients. The model can subsequently be used as a tool for checking the consistency of all this data, and may also be employed for controlling the quality of the data collected by the multiparametric sensors.

Nutrients cycling in Mediterranean basins: the role of the biological pump in the trophic regime

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.

Short-term simulations under winter conditions in the lagoon of Venice : a contribution to the environmental impact assessment of temporary closure of the inlets

A primitive equation finite element hydrodynamic model developed for the lagoon of Venice some years ago has been internally coupled with the Streeter-Phelps module of Water Quality Analysis Simulation Program (WASP). The coupled model (VELFEEM) has been applied for a first evaluation of the impact on water quality of the lagoon of Venice induced by a reduction in the exchange with the Adriatic Sea, which could be caused by the temporary closure of the inlets. Such closures have been proposed to prevent the flooding (acqua-alta) of the historical city occurring in winter time and would be obtained by specifically designed mobile gates (MOSE). Short-term simulations of biochemical oxygen-dissolved oxygen (BOD-DO) dynamics are performed under winter conditions, in both the presence and the absence of the mobile closure. Results suggest that the mobile closures do not significantly affect the water quality of the lagoon, even in the case of repeated closures, and that, in any case, the lagoon seems to be able to return rather easily to its unperturbed condition when the inlets are open again.