Modelling dissolved oxygen dynamics in coastal lagoons

High frequency dissolved oxygen measurements in Mediterranean coastal lagoons show different dynamics on different time scales. In this paper the seasonal and daily dynamics are analysed and discussed and a continuous simulation model is developed to represent them for the salt lake of Fogliano (Italy). Field and laboratory experiments evidenced that primary production slows down in highly oxygenated and irradiated summer days, acting in feedback regime with the oxygen already present in the media, that wind stress contributes in exceeding the oxygen saturation concentration and that there is a firm correlation between oxygen consumption at the sediment layer and overhanging water temperature. Water temperature, solar radiation and wind regime are the forcing functions of the model; the main state variables are dissolved oxygen and detritus in the pelagic and benthic layers, together with carbon dioxide and vegetal biomass. The slow seasonal and fast diel dynamics are both revealed by the model evidencing detailed aspects of oxygen dynamics in a coherent agreement with field observed data trends.