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In line with the framework of strategic guidelines for marine aquacultures, mussel cultures have to be operated in Areas of Organized Aquaculture Development (AOAD). Forty per cent of the national mussel culture production, which is based in Chalastra (NW Gulf of Thessaloniki, part of the Thermaikos Gulf), uses pole and longline systems. Due to legislative changes, both farmers and the authorities are in the process of reforming the existing units and planning processes based on the principles of sustainability, as defined in AOAD. The aim of this study is to estimate the appropriate orientation lines on which the mussel socks are to be placed in the mussel culturing units, in relation to the direction of sea currents for optimum water circulation in AOAD. The hydro-dynamics of the Chalastra basin is mainly wind driven and affected by prevailing northerly and southerly winds during winter and summer periods, respectively. When placed perpendicular to sea currents, the socks in the mussel production lines form an obstacle. Thus, the appropriate orientation of pole and longline units based on natural current directions can comprise a useful tool for sustainable mussel cultures. The benefits arising from the application of the proposed scheme are twofold: (a) productivity through the appropriate circulation and regeneration of nutrients can be maximized and (b) the environmental impacts of mussel culture activity can be minimized, as byproducts can more easily be dispersed of and biodegraded. In the present study, two basic schemes are proposed: (a) the division of AOAD is being researched into three sub-areas for pole and long-line units respectively and (b) the placement of the shortest possible length of production lines parallel to sea currents. [ABSTRACT FROM AUTHOR]

A methodology describing matter transfer in coastal basins connected with a small channel is presented. More specifically, the spreading of suspended particulate matter after the sudden release from a source in Thermaikos Bay (NW Aegean Sea) and the effect to the adjacent Toroneos bay through the Potidea Channel was examined via mathematical modelling. A 2DH hydrodynamic model was applied coupled to a quasi 3D transport model. A key point was the computation of the probability for a particle reaching the computational cell, adjacent to the channel, to pass the small channel of subgrid scale and reach the adjacent bay. For that reason, another, second couple of a small scale high resolution 2DH hydrodynamic and transport models, focusing on vicinity of the channel was applied so that the aforementioned probability could be calculated for the large scale model. The simulations referred to the wind generated circulation and resulted to the eventual distribution of the particle concentrations over the two bays, thus, informing us about the potential matter transfer through the Potidea channel. It was finally shown that only a minor amount of material crosses the channel and escapes Thermaikos to reach Toroneos, under the influence of SW, NW and W winds. [ABSTRACT FROM AUTHOR]

The development and application of a three-dimensional hydrodynamic and sediment transport model for the Gulf of Thermaikos, in the Northwestern Aegean Sea is presented. The processes that control the transfer of river-borne waters and fine-grained sediments are examined. These processes are: the overall basin circulation, the wind-driven flow, the buoyancy-driven flow that is associated with river plume dynamics and the sedimentation processes (flocculation, settling, deposition and erosion). We perform individual experiments, where only some of the processes are included, in order to study the different components of the transport mechanism separately. We also perform comprehensive experiments, where all processes are taken into account. It is found that a large percentage of the suspended particulate matter is deposited on the seabed of the Thermaikos Gulf and mainly near the river discharge sites. Although the sedimentation processes are of primary importance, the transport rates and pathways are greatly affected by the hydrodynamic processes that control circulation. Furthermore, the basin topography has a considerable impact on the transport, as the main rivers discharge near the narrow basin head and near areas of strong coastline curvature that act as sediment trapping zones. [Copyright &y& Elsevier]