Effects of climate changes on the spatiotemporal dynamics of Posidonia oceanica in the Mediterranean Sea

Posidonia oceanica has been investigated experimentally in the last decades due to its key role in biodiversity conservation in the Mediterranean Sea [1]. More recently, a mathematical model based on a system of non-local evolutionary PDEs with Reaction-Diffusion and Clonal terms, known as the Advection-Branching-Death (ABD) model, has been used to simulate the spatio-temporal behavior of seagrass density in the Western Mediterranean basin [2-3]. By using a simplified ABD model [3], we investigated the dynamics of the density of Posidonia oceanica in the Capo Gallo – Isola delle Femmine Protected Marine Area by taking into account both the seawater temperature enhancement expected in coming years due to climate changes and the real bathymetric distribution in the studied area. Numerical results indicate that model parameters, such as mortality and branching rates, and their connection with environmental factors like seawater temperature (or accumulated degree-day anomaly) and water column depth, are crucial for predicting critical situations like desertification patterns. The theoretical analysis confirms the experimental findings acquired in the Western Mediterranean Sea in the last two decades [1], which showed that the mortality rate is directly correlated with the seawater temperature, while the branching rate is inversely correlated with water column depth. The model results show a desertification trend across wide areas of the investigated site when the seawater temperature enhancement in the deepest layer of the water column in summer is set at 0.5 °C. These theoretical results could help analyze the same phenomenon in different sites of the Mediterranean Sea.