Abstract
Posidonia oceanica is one of the most important endemic species of the infralittoral stage of
the Mediterranean Sea. It plays an important economic and ecological role. It is also routinely
used as an indicator of the quality of the Mediterranean coastal environment. In order to
assess the responses of Posidonia oceanica to environmental stresses, a study was conducted
to evaluate the morphological and physiological parameters among nine (09) stations. As a
first step, we analyzed leaf biometrics in terms of leaf number, leaf length, leaf width, and leaf
area. A notable decrease in the latter parameter was associated with proximity to a port and
the presence of sewage discharges. Then we considered the epiphyte index, which showed an
increase probably related to the proximity of urban wastewater discharges. Finally, we
analyzed the nitrogen content in the leaves, which shows significant values when the meadow
is polluted with municipal waste. Finally, the good correlation between global nitrogen
content and global epiphyte index supports the use of this parameter (nitrogen content in
leaves) in monitoring programs as a parameter that can provide important information on the
vitality of Posidonia oceanica meadows on the Algerian coast.
Keywords: Posidonia oceanica; leaf biometrics; nitrogen content; bioindicator; Algerian
coast.