État des herbiers à Posidonia oceanica au niveau de quelques sites de la côte de Mostaganem

Abstract

In order to assess the condition of the Posidonia oceanica seagrass beds off the coast of Mostaganem, phenological parameters were monitored at the two sites of Hadjadj and Petit Port, at depths of between -1.20 and -1.50 m, during the month of May 2026. The seagrass bed at the Hadjadj site grows on loose substrate. The results show a higher average number of leaves per tuft, leaves that are generally shorter but slightly wider, a higher A coefficient, as well as higher epiphytic load and recovery rate, and a higher frequency of grazed apices. These characteristics suggest a more pronounced influence of biological and environmental interactions at this site. The seagrass bed at the Petit Port site grows on a mixed sandy and rocky substrate. It has longer leaves, resulting in a larger average leaf area, and a higher frequency of broken apices. These observations could be explained by stronger currents, the movement which causes mechanical stress on the leaves. Overall, the results highlight clear environmental disparities between the two sites. Whilst the Hadjadj site appears to be more sensitive to biotic pressures (epiphytism and herbivory), Petit Port seems to be more clearly influenced by hydrodynamic factors.