Marine Fungi Associated with the Seagrass Posidonia oceanica (L.) Delile from the West Coast of Libya: Diversity, Taxonomy, and Ecological Significance

Abstract

Posidonia oceanica (L.) Delile, a marine endemic seagrass, serves as a critical ecosystem engineer in coastal marine environments of the Mediterranean Sea. This study investigates the fungal communities associated with P. oceanica along the west coast of Libya, thereby complementing previous research conducted on the eastern coast of the country. Fungal assemblages were examined through microscopy and culture-dependent methods applied to surface-sterilized samples of roots, rhizomes, and leaves collected from depths of 5–12 m from the beaches of Tripoli extending from Al-Qarabolli to Al-Siyahiyya. A total of 34 fungal isolates belonging to twelve taxa were obtained and identified. The identified taxa encompass: Halotthia posidonia and Chaetomium sp. (Ascomycetes); Alternaria sp., Aspergillus fumigatus, A. niger, Cladosporium sp., Humicola sp., Penicillium sp., Fusarium sp., and Scopulariopsis sp. (Hyphomycetes); and the Mucoromycetes representatives Mucor sp. and Rhizopus sp. Modern taxonomic classification assigns ten taxa to Ascomycota (83.3%) and two to Mucoromycota (16.7%). The highest recorded frequency of appearance was shared equally by Alternaria sp. and Aspergillus fumigatus (17.65% each), followed by A. niger (14.71%). The lowest frequency (2.94%) was recorded for both Cladosporium sp. and Penicillium sp. Statistical analysis confirmed significant variation in the frequency distribution among the isolated taxa (χ² = 32.18, df = 9, p < 0.001). Most isolated taxa exhibit characteristics of terrestrial-derived (facultative marine) fungi, while Halotthia posidonia and Humicola sp. are considered obligate marine species. These findings expand our knowledge of the mycobiome of P. oceanica meadows along the Libyan coastline and underscore the need for further molecular-based surveys.