Marine Benthic Algae of the Eastern Samar Islands of Homonhon, Sulu-an, and Manicani, Philippines

Botanical explorations in the Philippines have been conducted for the most part in easily accessible regions, resulting in fragmentary information that prevents a thorough assessment of its total biological richness. Many insular sites, which are potentially biologically diverse, remain unexplored due to reasons of geographic isolation, weather disturbance, and logistical considerations. To address these gaps and to provide added information on the diversity and distribution of the seaweed flora around the archipelago, we report herein the taxonomy of the marine benthic algae of three islands in Eastern Samar province. Macrobenthic algae were collected in 18 sites in Homonhon, Sulu-an, and Manicani islands in Guiuan. Seaweeds were identified in situ up to the lowest taxonomic level possible and further analyzed in the laboratory. Cluster analysis based on the Jaccard index using the PAST software was used to infer similarities among the sampling sites with respect to the seaweed flora of the newly collected samples. Analysis of similarities and similarity percentage were also used to further support the results of the study. The paper highlights 56 seaweeds (Chlorophyceae: 28 spp.; Phaeophyceae: 11 spp.; Rhodophyceae: 17 spp.) collected in 18 collection sites in Homonhon, Manicani, and Sulu-an Islands in Guiuan, Eastern Samar. All are considered new records to the small islands, whereas 39 are considered new records of species in the Eastern Samar province. Cluster analysis suggests similarities in seaweed flora in the islands, which may be attributed to the substrates and hydrodynamism in the islands. The islands have a relatively diverse seaweed flora, despite its narrow areas highlighting 5% of the total seaweed flora of the country. This paper is the first attempt to provide better documentation of macroalgal communities in remote islands in the Eastern Philippines (Guiuan, Eastern Samar).