Modelling approach for the evaluation of burial and erosion processes on Posidonia oceanica meadows

Abstract Seagrass loss can be partially attributed to naturally- or anthropogenically-induced sediment dynamics that involve excessive burial or erosion processes. The main goal of this work was to develop a modelling approach for analysing bottom morphological changes on Sites of Community Importance (SCIs) characterized by the presence of Posidonia oceanica meadows. Sediment dynamics (settling fluxes) and composition (grain size and mineralogy) within the two SCIs of the Civitavecchia coastal zone (north-eastern Tyrrhenian, Italy) were investigated using sediment traps and bottom sediment samples. Moreover structural, morphological, and dynamic parameters of P. oceanica meadows were analyzed. The results showed high reliability in reproducing the settling fluxes of medium and coarser sands (the most abundant sediment fractions of the two SCIs) compared to the corresponding fluxes estimated with sediment traps. To further confirm the accuracy of the proposed approach, a significant relationship was shown to exist between bottom morphological changes reproduced by the numerical model and plant rhizome growth as measured by in-situ sampling; this relationship attests to the capacity of P. oceanica to withstand burial and erosion processes. The model allowed us to perform a high spatial resolution evaluation of erosion levels and deposition processes that occur within the two SCIs, providing a predictive and useful tool towards a more sustainable management and conservation strategy of P. oceanica meadows in coastal zones.