IT07-001-M (Sacca di Goro), IT07-002-M (Valli di Comacchio) The Sacca di Goro is a shallow-water embayment of the Po River Delta approximately triangular in shape with a surface area of 26 Km2, an average depth of 1.5 m, and it is connected to the sea by two mouths about 0.9 Km wide each. The lagoon is characterized by a clear zonation with the low energy eastern area separated from two higher energy zones, the western area influenced by freshwater inflow from the Po di Volano and the central area influenced by the sea The eastern zone is very shallow (maximum depth 1 m) and accounts for one half of the total surface area and one quarter of the water volume. The lagoon is surrounded by embankments. The main freshwater inputs are the Po di Volano River, the Canal Bianco and Giralda, which have approximately the same discharge rates. Freshwater inlets are also located along the Po di Goro River and are regulated by sluices. There are no direct estimates of the freshwater input from the Po di Goro, which is usually assumed to be equivalent to that of the Po di Volano. The freshwater system is mostly located in a subsident area and is regulated by a system of pumping stations (scooping plants). The fresh water or hydraulic residence time oscillates monthly between 2.5 and 122 days with a mean value of 24.5 days, whereas the water exchange time ranges from 2 to 4 days. The tidal amplitude is ca 80 cm. The bottom of the lagoon is flat and the sediment is alluvial mud with high clay and silt content in the northern and central zones. Sand is more abundant near the southern shoreline, whilst sandy mud occurs in the eastern area.

The Valli di Comacchio are a large (115 km2) complex of shallow-water (with depth ranging from 0.5-1.5 m) brackish lagoons located in the southernmost part of the Po River deltaic area (Figure 1). The Valli are, nowadays, constituted by three main basins, i.e. Valle Magnavacca, Valle Fossa di Porto and Valle Campo. This semi-enclosed lagoonal complex is almost completely surrounded by earthen dikes, and separated by the sea by the highly anthropogenically impacted, 2.5 km-wide Spina spit. The Valli are connected with the Adriatic Sea by three marine channels, Portocanale, Logonovo and Gobbino, but since the latter is impounded, major water exchange with the sea occurs only through the firsts two channels. The former receives also nutrient-enriched continental water from Valle Fattibello. Water exchange with the sea is both tidal and man-regulated. Moreover, from February to May, large amounts of freshwater are conveyed through the Reno river through two dams in the southermost parts of Valle Magnavacca and Valle Fossa di Porto. Due to the shallowness of the basins and their limited water renewal, salinity (annual range: 24-38 psu) is mostly influenced by meteorological events, such as evaporation and occasional heavy rainstorms. The bottoms of the Valli are typically muddy, but sparsely vegetated meadows of the seagrass Ruppia cirrhosa occur in the southern parts of the Valli Magnavacca and Fossa di Porto. These meadows are the remnants of the larger macrophytic coverage that characterized the bottom of the Valli in the early 1970s