Modeling the biogeochemical dynamics of a shallow lagoon impacted by intensive shellfish farming (Sacca di Goro, Po river delta, Northern Adriatic Sea).

Abstract

Within the European Interreg Italy-Croatia project “CoAStal and marine waters integrated monitoring systems for ecosystems proteCtion AnD managemEnt (CASCADE)” ( https://www.italy-croatia.eu/web/cascade), an off-line coupled physical-biogeochemical box-model was implemented in the shallow Goro lagoon (northern Adriatic Sea, Po river delta region) in order to study its biogeochemical dynamics. The lagoon is subject to intensive shellfish (Ruditapes Philippinarum) farming: more than one third of the lagoon surface is exploited for clam farming, with an annual production that reached a maximum of approximately 15,000 t y-1 in the early 1990s.The biogeochemical component of the modelling system is the Biogeochemical Flux Model (BFM), accounting for the biogeochemical cycling processes occurring in water and sediments, including (with a functional groups approach) the planktonic and the zoobenthic biota, and fully resolving the benthic pelagic coupling. BFM is implemented in several areas of the lagoon having homogeneous characteristics and different shellfish farming conditions. The areas resolved by the BFM are connected among each other by the mass exchanges (dissolved and particulate) depending by the water circulation in the lagoon that is modeled by the Shallow Water Hydrodynamic Finite Element Model (SHYFEM).The results of the simulation show that the model is able to capture the essential dynamics of the lagoon, with values almost in the same order of magnitude with the measurements from experimental campaigns runned during the project. Particular attention (trough sensitivity experiments) is given to the impact of the the shellfish farming on the lagoon biogeochemical dynamics. The ultimate goal of this work is to provide stakeholders with useful information regarding the evolving biogeochemical conditions that favor the sustainability  of the  shellfish farming.