A Rapid Method to Identify the Effects of Coastal Artificialization on Posidonia oceanica Meadows in Coves

This study proposes a rapid and cost-effective method to identify the effects of coastal artificialization on the distribution of shallow Posidonia oceanica meadows. Seven embayed coves were selected along the Ligurian coastline (Italy, NW Mediterranean) to evaluate the influence of the coast geometry on the depth and morphology of the meadow upper limits (i.e., the shallowest depth reached by the plants towards the coastline). The areas under investigation are characterized by rocky coasts and exhibit varying degrees of embayment, resulting in different levels of exposure to wave action. The geometric features of embayed coastlines, along with hydrodynamics and physical parameters, were examined in relation to the structure of P. oceanica meadows within each cove. The results indicated that both natural and anthropogenic (i.e., artificial) coastal geometries influence the spatial distribution of P. oceanica meadows, leading to significant heterogeneity in their upper limits. The configuration of the embayment system produces various types of hydrodynamic circulation. The existence of a cellular circulation pattern leads to the formation of rip or megarip currents, which cause erosion in the shallow portions of the meadows and create sandy channels that disrupt the continuity of the meadows. Establishing a relationship between the hydrodynamics within the coves and the characteristics of the upper limits of the meadows proved to be a valuable method for promptly distinguishing whether the observed conditions stemmed from natural or human influences. This proposed approach enables a preliminary and cost-effective assessment of the origins of erosive processes affecting the shallow portions of P. oceanica meadows. Such an approach represents a clear management advantage in the environmental impact assessment of coastal engineering projects.