*3.1. Environmental Variability*

Physico-chemical parameters measured at natural sites employed for model calibration varied markedly according to the sampling season, sub-basin and location along the environmental gradients. Temperature, for instance, was characterised by seasonal fluctuations, showing average values of 19.5 (standard deviation 4.3), 25.1 (sd 2.8) and 18 ◦C (sd 5.6) in spring, summer and autumn respectively. Similarly, average dissolved oxygen values were 94.3 (sd 19.2), 73.4 (sd 19.1) and 85.6% (sd 15.2) during the three seasons. Other environmental parameters, in turn, varied spatially. Salinity ranged from 4 to 40, showing lower values at sites located in the inner portions of the lagoon, closer to freshwater inputs. Sediment grain size (range 1 to 72% sand) and water turbidity (range 1 to 69 FNU) varied both along the salinity gradient (with lower grain size and higher turbidity in inner lagoon areas) and between the two habitat locations considered (with lower grain size and lower turbidity inside saltmarsh creeks). Finally, the sampling sites in the northern, central and southern sub-basins showed some di fferences in terms of salinity, with average values of 24.2 (sd 8.8), 28.7 (sd 6.2) and 24.3 (sd 8.6) respectively, and sediment grain size, with average values of 16.9 (sd 11.9), 17.2 (sd 10.5) and 27.7% sand (sd 21.3) respectively.
