Biodiversity and frequency of occurrence of jellyfish (cnidaria) in Al Hoceima Bay (North coast of Morocco, Alboran Sea)

Abstract

Jellyfish are the best-known group of gelatinous zooplankton; they refer to organisms from the phylum Cnidaria, including animals with cnidocytes (stinging cells). As part of our research on jellyfish that swarm in the bay of Al Hoceima conducted during the period (2021-2022), a study of the diversity of species of jellyfish in the bay has proved to be of paramount importance because of the risks associated with their proliferation, especially in summer periods. The species composition and frequency of occurrence of the jellyfish community in Al Hoceima Bay (The northern coast of Morocco) were studied during two seasons, summer 2021 and winter 2022. Zooplankton sampling was conducted within the epileptic layer (between 0 and 80 m) at 9 stations. A total of 9 species of Hydromedusae and Scyphomedusae were identified in the study area. The populations of Hydromedusae are represented by Trchymedusae (4 species), Anthomedusae (2 species), and Leptomedusae (one species). The Trachymedusa Aglaura hemistoma was widely distributed in the bay, as it was found in six sampling stations, with a frequency of occurrence Fi>66% during the summer period. The Antomedusae Pantachogon militare was inventoried for the first time in the southwestern Mediterranean Sea.The population of Scyphomedusae is represented by two species, Pelagia noctiluca and Rhizostoma Pulmo, both species showed dense aggregations in the Bay during the summer of 2022.