A Multidisciplinary and Ecosystemic Approach in the Oristano Lagoon-Gulf System (Sardinia, Italy) as a Tool in Management Plans.

This paper provides an overview of some of the research activities carried out in the Oristano 1 - Lagoon-Gulf system (western Sardinia, Italy) aimed at assessing the ecological quality of a complex transitional-coastal system renowned for its naturalistic and economical value, but subject to an increasing anthropogenic pressure. Numerical models concerning physical and ecological processes have been applied, including a fully 2 - coupled hydrodynamic-ecological model based on the finite element method, suited for application to lagoons and coastal seas. Different scenarios characterized by modified settings of the hydraulic balance between the Gulf of Oristano and the Cabras Lagoon have been considered and numerical simulations have been carried out to predict the evolution of both hydrological and ecological variables within the system under different meteorological forcing. Parallel investigations on the physical and chemical characteristics of the sediments and macrobenthic 3 - assemblages have been conducted in the Cabras Lagoon and the adjacent coastal area of the Gulf of Oristano. These studies have shown a close link between the distribution of organic-C bounding fine sediments (<8 ?m grain size fractions) and benthic macroinvertebrates, and the water residence times computed from the model. In the Gulf, the structural and functional importance of Posidonia oceanica and Cymodocea nodosa seagrass meadows in sustaining a high biodiversity and as a natural trapping of fine particles is highlighted. Studies on the effect of hypoxia on ecophysiology, energetics and behaviour have been carried out on 4 - the various species of lagoon fishes (Liza aurata, Mugil cephalus and Dicentrarchus labrax), with the specific goal of identifying the thresholds for the effects of hypoxia, a common phenomenon occurring in coastal lagoons, on various physiological and behavioral traits (e.g. swimming energetics, escape performance). The results show that these thresholds ranged from 10 to 50% of air saturation, and were species- and variable-specific. Our multidisciplinary and ecosystemic approach, applicable to other similar systems, is aimed at 5 - supporting local administrations in decision making with regard to the management of the transitional and coastal waters of the Oristano Lagoon-Gulf system within the context of the European Water Framework Directive (WFD; EC, 2000).