A finite element ecological model: a first application to the Venice Lagoon

A Finite Element Ecological Model (FEEM) has been set up by fully coupling a primitive equation finite element hydrodynamic model (FEM) to an ecological model derived from EUTRO, the ecological submodel contained in the water quality model WASP, released by US-EPA. The work required the ‘decoupling’ of EUTRO from WASP and its transformation into a standalone program, the testing of such a structure versus the results obtained by running the WASP in the 0D version, the improvement of its parameterisation up to the inclusion of zooplankton as a dynamic variable explicitly modelled, the definition of an interface module, and the actual coupling of the improved ecological module and the hydrodynamic primitive equation model. The integrated model has then been applied, as a first test, to the Venice Lagoon (VELFEEM). To this aim idealised forcings (tide, meteo) have been used together with actual field data (river discharge, nutrient loadings) to run simulations over a one-year period. Analysis of the results shows that the model is numerically stable, variations in the state variables are consistent, and nutrients, plankton and oxygen evolves in space and time in a ecologically coherent way. Main features of the lagoon, namely oxygen seasonal evolution and dispersion of nutrients from the point sources are qualitatively reproduced. An additional result is that the improved version of the 0D ecological submodel has been organised as an independent module which can be run by a single subroutine call, and therefore can be easily integrated in any structure and coupled to any hydrodynamic model. The coupling here presented demonstrates the ease of such an integration.