Linking Dinoflagellate Cyst Assemblages with Nutrient Dynamics in the Gulf of Annaba (Southwestern Mediterranean)

Soumaya, Behnas; Aicha Beya, Amira; Zaidi, Raouf; Ouafa, Sadlaib; Frihi, Hocine

doi:10.21608/ejabf.2025.393301.6156

Linking Dinoflagellate Cyst Assemblages with Nutrient Dynamics in the Gulf of Annaba (Southwestern Mediterranean)

Document Type : Original Article

Authors

¹ Department of Marine Sciences, Badji Mokhtar University, Annaba

² Department of Marine Sciences, Badji Mokhtar University Annaba

³ Department of marine sciences, Chadli Bendjedid Unversity El Tarf Algeria

⁴ Badji Mokhtar university Annaba -Algeria

10.21608/ejabf.2025.393301.6156

Abstract

This study investigates modern dinoflagellate cyst assemblages and their relationships with environmental parameters as indicators of eutrophication in the Gulf of Annaba, Algeria. In 2018, surface sediment and water samples were collected from three coastal stations, including a commercial port, to evaluate spatial variations in cyst abundance, diversity, and nutrient enrichment. A total of 874, 544 and 150 dinoflagellate cysts were recorded at stations 1 (Port), 2, and 3, respectively, reflecting strong ecological gradients linked to anthropogenic pressure and sediment characteristics. Species richness and diversity were the highest in muddy, organic-rich sediments at the port station, with dominant taxa such as Lingulodinium machaerophorum, Alexandrium pacificum indicating eutrophic conditions and potential harmful algal bloom (HAB) risks. Analyses of physico‑chemical parameters indicated significantly elevated concentrations of dissolved inorganic nitrogen (DIN), phosphate (PO₄), and silicate (SiO₄) in the bottom layers, with Station 1 showing the highest values. Ammonium (NH₄) was the predominant nitrogen form, comprising over 50% of total DIN in surface and bottom waters at the port station, highlighting localized organic enrichment likely driven by urban, industrial, and port-related discharges. The distribution of dinoflagellate cysts correlates strongly with these nutrient and sedimentary patterns, validating their use as bioindicators of eutrophication. These findings underscore the ecological sensitivity of the Gulf of Annaba to anthropogenic impacts and advocate for the integration of cyst monitoring in coastal environmental.

Keywords