Torre Guaceto wetland

In this paper, we report a study of the water, salt and nutrients budgets of the wetland part of the Torre Guaceto Nature Reserve, in which the LOICZ Biogeochemical Budget Model (Gordon et al. 1996) was applied to estimate the net system metabolism. The reserve is located in the Apulia region of Italy, on the Adriatic coast, about 15 km north of the city of Brindisi (Figure 3.12 and 3.19). The region is characterized by Mediterranean-type climatic variations, with meteorologically stable summers and unstable winters. The study took place between July 2001 and May 2002. The wetland area of the reserve was treated as a single-box, single-layer system with seasonal variation, following LOICZ guidelines. The entire system, consisting of a marine area and the salt marsh, can be considered to be in an oligomesotrophic tate on the basis of the classification proposed by Håkanson (1994), Nürnberg (1996), Dodds et al. (1998) and the measured dissolved inorganic phosphorus and chlorophyll a concentrations (0.43÷28.90 and 0.088÷1.06 mg m-3 respectively). The water volume of the brackish wetland cannot be considered constant (it varies from 2.39 to 4.54x105 m3) so the formulas of the standard LOICZ approach were modified to account for the seasonal variability of water volume and the characteristics of the system. Water inputs to the system are only precipitation and groundwater while outputs are evaporation and transport to sea via numerous small streams. The main inputs of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) are from groundwater. The estimated water turnover time in the system ranges between 21 and 69 days. Judging from the ΔDIP and ΔDIN values obtained with the model application, the system acts as a source for DIP and a sink for DIN; moreover, it seems to be slightly heterotrophic with denitrification processes prevailing over nitrogen fixation. The seasonal variations of ecosystem functions appear to be in agreement with vegetative growth and ageing of the reeds (Phragmites australis (Cav.) Trin ex Steud.), which constitute the predominant vegetation in the area.