Cartographie spatio-temporelle de la répartition de l’herbier à Posidonia oceanica, au-devant de la plage de Stidia (Mostaganem, Algérie).

Abstract

Posidonia meadow is the dominant marine grass is the most emblematic ecosystem of the Mediterranean Sea, it both key species of ecosystems. The widespread loss of this species is attributed to excessive anthropogenic pressure. The conservation of Posidonia meadow requires mapping to estimate the extent of existing stocks and to measure changes over time. Satellite images have been used for the localization of Posidonia meadow, they consider a cost-effective method to monitor large areas of shallow water that are a potential habitat for Posidonia meadow. The method used made it possible to produce accurate maps on a scale of 1:8000 scale maps, we produced three maps representing the evolution of the upper limit of Posidonia meadow according to three dates: 2014-2018, 2018-2022 and 2014-2022. The results obtained show a notable regression of the upper limit of the Posidonia meadow in front of Stidia beach, particularly during the period from 02/09/2014 to 06/10/2018. The following period, between 06/10/2018 and 31/10/2022, shows rather a relatively stable dynamic of the Posidonia meadow, but with a slight propensity for regression. This evolutionary dynamic could be explained by the multiplication of anthropogenic activities, namely wastewater discharges, fishing and yachting. The latter exert pressure on the ecological balance of the Stidia coastal zone through the destruction of Posidonia meadows