Diversity and Community Structure of Endophytic Fungi Isolated from the Brown Seaweed <i>Sargassum thunbergii</i> in Coastal Regions of Korea

This study investigated the diversity of endophytic fungi isolated from the brown seaweed, <i>Sargassum thunbergia,</i> collected from six coastal regions in Korea: Gangneung, Pohang, Buan, Taean, Tongyeong and Yeosu. A total of 154 fungal strains were isolated using ITS rDNA sequence analysis, resulting in 84 species across 43 genera. Species diversity, assessed based on the Shannon index, was highest in Tongyeong (H'=3.273), followed by Pohang (H'=3.209), Buan (H'=2.691), Yeosu (H'=2.649), Gangneung (H'=2.342), and Taean (H'=2.025). Principal Coordinates Analysis (PCoA) revealed that water temperature and dissolved oxygen are the primary environmental factors influencing the regional variation in fungal community structure. This study underscores the significance of environmental conditions in shaping the diversity and community composition of endophytic fungi in <i>S. thunbergii</i>.