First characterization of seagrass diatom assemblage in the Arabian Gulf: Structure, composition, spatial patterns, and potential use in environmental assessment

Diatoms, a critical component of the microphytobenthos, have been widely recognized for their utility as bioindicators of environmental health. This study provides the first comprehensive evaluation of epiphytic diatom biodiversity associated with seagrass meadows in the Arabian Gulf, an ecologically significant yet understudied marine region. During this study, the abundances and diversity of epiphytic diatom communities on three types of marine seagrasses (i.e., Halodule uninervis , Halophila stipulacea, and Halophila ovalis ) with varying morphologies were analyzed during two seasons (i.e., winter and summer) along the coastal areas of the Arabian Gulf in Saudi Arabia. Seasonal sampling and analysis using standardized morphological techniques revealed a high diversity of epiphytic diatoms, with Cocconeis spp. representing the most abundant genus across the investigated seagrass species. Multivariate analyses revealed significant seasonal differences in diatom community composition, with temperature emerging as the main factor associated with variations in assemblage structure and abundance. Differences among seagrass species were also observed, suggesting a potential influence of host characteristics on epiphytic diatom communities. The observed patterns provide valuable insights into the ecological drivers shaping epiphytic diatom assemblages in Arabian Gulf seagrass meadows. This study establishes a baseline for epiphytic diatom biodiversity in the western Arabian Gulf's seagrass ecosystems and underscores their role in environmental assessment and conservation efforts.