Publications (6)4.15 Total impact
- [Show abstract] [Hide abstract] ABSTRACT: The development of shellfish farming was analyzed with a coupled watershed and 3D biogeochemical model for the Sacca di Goro coastal lagoon (Northern Adriatic Sea, Italy). Sacca di Goro is the second site in Europe for the production of the Manila clam (Tapes philippinarum). Different scenarios were identified and analyzed, considering clam productivity under different environmental conditions, namely with and without macroalgal blooms. In addition, the influence of climatic variability – dry, average and wet years – was assessed. Model simulations indicated that macroalgal blooms have an important negative impact on clam productivity due to the risk of anoxia and subsequent clam mortality. Furthermore, simulation results evidenced that meteorological conditions also affect clam productivity, especially in a dry year due to a shortage of food supply.
- [Show abstract] [Hide abstract] ABSTRACT: Growth of the seaweed Ulva rigida C. Agardh was investigated in relation to biomass densities, internal nutrient pools and external nutrient supply. Research was carried out from 23 March to 5 July 1994 in the Sacca di Goro (Po Delta, Northern Italy), whose south-eastern part was covered by extensive mats of Ulva rigida. Two types of field experiments were conducted by incubating Ulva thalli inside large cages. In the first experiment, beginning on 23 March, 100 g of wet thalli were placed into the cages, allowed to grow for two weeks, then collected and replaced. This procedure was repeated 8 times over the study period. In the second experiment, Ulva thalli were left inside the cages and collected at selected time intervals (14, 27, 41, 64 and 76 days) in order to simulate the effects of increased density on growth and nutrient storage. We recorded specific growth rates (NGR) ranging from 0.025 to 0.081 d−1 for a period up to two months in the repeated short-term experiments performed at relatively low initial algal densities (300–500 g AFDW m−3). These NGR resulted significantly related to dissolved inorganic nitrogen (DIN) in the water column. Tissue concentrations of total Kjeldahl nitrogen (TN) were almost constant, while extractable nitrate decreased in a similar manner to DIN in the water column. Total phosphorus showed considerable variation, probably linked to pulsed freshwater inflow. In the long-term incubation experiment, NGR of Ulva was inversely related to density. Internal concentrations of both total P and TN reached maximum values after one month; thereafter P concentration remained almost constant, while TN decreased below 2% w/w (by dry weight). The TN decrease was also accompanied by an abrupt decrease in nitrate tissue concentration. The biomass incubated over the two month period suffered a progressive N limitation as shown by a decreasing N:P ratio (49.4 to 14.6). The reciprocal control of Ulva against biogeochemical environment and viceversa is a key factor in explaining both resource competition and successional stages in primary producer communities dominated by Ulva. However, when the biomass exceeds a critical threshold level, approximately 1 kg AFDW m−3, the macroalgal community switches from active production to rapid decomposition, probably as a result of selfshading, biomass density and development of anaerobic conditions within the macroalgal beds.
- [Show abstract] [Hide abstract] ABSTRACT: The Po di Volano canal–Sacca di Goro lagoon is asmall hydrographic system partially located in the southern part of the Po River Delta. The total surface area is 830km2 for the watershed and 26km2 for the lagoon, respectively. The watershed is exploited for agriculture, whilst the coastal lagoon is one of the most important European sites for clam (Tapes philippinarum) farming. The lagoon and small inland zones are also included in the Po River Delta Regional Park. Since the mid 1980s, in the Sacca di Goro lagoon abnormal macroalgal blooms occurred, mainly due to the proliferation of the green seaweed Ulva rigida. The enormous macroalgal biomass production was often followed by summer anoxia and dystrophic crises. In this paper, areview of the main studies concerning altered nutrient cycling and water and sediment pollution is presented. Special attention is paid to the discussion of the different aspects of the watershed–coastal lagoon interactions: main features of the watershed and its evolution, anthropogenic pressures, river runoff influence, nutrient and other contaminant cycles, shellfish farming, and macroalgal blooms. Finally, abrief presentation of possible scenarios is given in an ecological economics perspective.
Article: SACCA DI GORO LAGOON - ITALY
- [Show abstract] [Hide abstract] ABSTRACT: Different scenarios and their prioritization were identified for the Sacca di Goro (Adriatic Sea, Northern Italy), an eutrophic lagoon which is exploited with extensive clam farming activities. A preliminary scenario assessment was investigated with qualitative modelling. Economic and environmental variables were accommodated in a comprehensive model of the lagoon that describes major interactions between selected compartments. This kind of analysis is specially suited for systems that are partially specified. In a second step, we addressed the first priority scenario identify by end-users and which concerns clam farming activities in the lagoon. This scenario was analysed using a quantitative approach based on a 3D integrated hydrodynamic- biogeochemical model. Such approach allowed the assessment of the implications of an increase in the clam farming area. The first results seems to indicate that a further increase of clam farming areas (or a more intense exploitation) inside the Sacca di Goro lagoon would increase the risk of anoxia and the vulnerability of clam farming to Ulva blooms. On the contrary, an increase in the exploitation area outside the lagoon will increase the average productivity and maintain constant the risks of anoxia and the vulnerability to Ulva blooms. Furthermore, the cost of measures taken by the local and regional authorities for the lagoon management and to control nuisance macroalgal blooms are potentially compensated by the increase in clams production predicted by the model. The focus on clam farming provides only a partial view of a more complex system which composes by agriculture, urban, touristic areas, and natural sites and is under the influence of climate changes. However, such scenarios constitute only the first stage in the procedure of overall lagoon scenario analysis, and a second iteration is necessary to define the main constraints and boundaries, as well as to incorporate the economic evaluation and social implications of the different options.