Nutrient-flux evaluation by the LOICZ Biogeochemical Model in Mediterranean lagoons: the case of Cabras Lagoon (Central-Western Sardinia)

Abstract

In this study, the Land-Ocean Interactions in the Coastal Zone (LOICZ) budgeting procedure was used to evaluate the main nutrient pathways and ecosystem functions within Cabras Lagoon (Central-Western Sardinia, Italy) in 2004. The results of a simple one-box and one-layer model showed that nutrient accumulation prevailed over mobilisation for both dissolved inorganic phosphorus (annual mean of 675.69 mol d−1) and dissolved inorganic nitrogen (mean of 6120.05 mol d−1). Net ecosystem metabolism (NEM) was always positive, implying that production predominated over respiration throughout the year (mean of 3.3 mmol C m−2d−1). Estimates obtained from the model also highlighted the fact that nitrogen fixation prevailed over denitrification (mean of 0.14 mmol m−2d−1). Finally, extended water-residence times (mean of 192 days) were observed in the lagoon, particularly in the summer. An approach based on the improvement of water exchange with the sea would provide a relatively simple and short-term interim strategy, until more comprehensive actions aimed at reducing the anthropogenic nutrient loads in the watershed can be implemented.