Benthic Foraminifera and Diatom Relationship: Insights from RbcL Gene Sequences in Palk Bay

Understanding the symbiotic relationships between benthic foraminifera and diatoms is crucial for ecological studies, particularly in environmental changes. In this study, DNA barcoding, targeting the rbcL gene, was applied to identify diatoms and evaluate their diversity within the foraminiferal shells in Thondi, Palk Bay. Foraminifera were isolated from the sediment samples collected using grab samplers at six different locations. The separated benthic foraminifera were then used for DNA barcoding. The obtained DNA sequences were aligned and analyzed comprehensively using Geneious Pro v5.1. A higher population of Ammonia parkinsoniana was observed in March 2023 compared to May 2023, with a notable presence of algal symbionts. Seasonal temperature fluctuations exhibited a strong positive influence on the abundance of A. parkinsoniana. Changes in salinity and temperature were suggested to induce species shifts within the intertidal foraminiferal community. The symbiotic diatoms within the A. parkinsoniana shells were confirmed through rbcL gene sequencing and Scanning Electron Microscope (SEM) imaging. Phylogenetic analysis indicated a 50% similarity between the foraminifera and diatoms. SEM imagery displayed diatoms attached to the surface of A. parkinsoniana cells, while Energy Dispersive X-ray (EDX) analysis detected silica content at the diatom sites. This study highlights the potential of DNA barcoding to identify and develop novel chloroplast markers to elucidate foraminiferal symbiotic relationships.