Responses of South Caspian Coastal Foraminifera to Warming: Spatial Patterns and Assemblage Shifts

Abstract This study investigated the spatial distribution of coastal foraminifera at four stations, identifying seven distinct species representing five genera and three families, with Ammonia beccarii caspica as the dominant species. The Bandar Gaz station exhibited the highest density, species richness, evenness, and Shannon diversity. Consequently, Bandar Gaz was selected for a controlled field experiment examining benthic foraminiferal community responses to increased surface water temperature (20°C, 24°C, 27°C, and 30°C) over 60 days. While the highest total density and evenness were observed at 30°C, the total number of species and Margalef and Shannon indices did not significantly differ among treatments. Temperature changes significantly altered community structure through shifts in species dominance. Ammonia beccarii displayed resilience and increased dominance with higher temperatures, replacing other species. Elphidum advenum density decreased significantly at 30°C, while Ammonia tepida increased in dominance with rising temperatures. These findings highlight temperature-driven alterations in foraminiferal assemblages, with implications for coastal ecosystem monitoring in the context of climate change.