Brown Algal Diversity Along Selected Coastlines of the Jaffna Peninsula and Delft Island, Sri Lanka

Marine algae are important biological resources with considerable ecological and economic significance. Understanding their diversity and distribution is essential for biodiversity conservation and the sustainable utilization of marine resources. However, comprehensive information on the diversity and distribution of marine algae along the northern coastal regions of Sri Lanka has remained limited for more than five decades. Therefore, this study investigated the diversity and distribution of brown algae along selected coastal areas of the Jaffna Peninsula and Delft Island, Sri Lanka. The study was conducted at four sites within the Jaffna Peninsula and three sites on Delft Island. Brown algal communities were surveyed using the transect method, in which 0.5 m x 0.5 m quadrats were placed at uniform intervals along each transect. Three replicate transects were established at each study site. Brown algal species were identified based on their morphological characteristics, and species diversity was assessed using the Shannon-Wiener and Simpson’s diversity indices. A total of thirteen brown algal species were identified across the study sites, with significant variations in species diversity observed among locations. The highest diversity was recorded at Site-1 on Delft Island (09°31'19.9" N, 79°43'32.6" E ) (Shannon-Wiener index, H=1.90; Simpson’s diversity index, 1-D=0.85). Members of the family Sargassaceae were the most dominant brown algae across the majority of the selected sites, Padina boryana exhibited the highest relative abundance across three sites.  The findings of this study demonstrate the occurrence of diverse brown algal community along the coastal areas of the Jaffna Peninsula and Delft Island. These baseline data provide valuable information for future ecological studies, conservation initiatives, and the sustainable management of marine algal resources in northern Sri Lanka.