Abstract
Seaweeds play an important role in energy production in marine, coastal and Island ecosystems. Baseline research was carried out in Saint Martin’s Island, Bangladesh in the northern Bay of Bengal, in order to demonstrate the habitat structure, diversity patterns and species co-occurrence of seaweeds. A total of 34 species were identified belonging to Chlorophyta (7 species), Rhodophyta (17 species) and Phaeophyta (10 species). Among them, eleven species were common to all three sampling zones whereas, eight were dominant species. Species richness and species diversity were both higher in the upper subtidal zone and lower in the intertidal zone. Species distribution revealed that 23 species were present in the upper intertidal zone, 29 species in the intertidal and, 24 species in the upper subtidal zone. The zonation profile of seaweeds revealed that three types of vegetation were covered in this area. The highest density of Chlorophyta (23 ind./m2) was found in the upper intertidal zone while, Phaeophyta (15 ind./m2) and Rhodophyta (9 ind/m2) were recorded at higher densities in the upper subtidal zone. The standing crops (biomass) were higher for Chlorophyta in the upper intertidal zone (78 gm/m2), Rhodophyta in the intertidal zone (35 gm/m2) and, Phaeophyta in the upper subtidal zone (65 gm/m2). Species co-occurrence revealed that 22 species were significantly correlated with each other. The community composition of Chlorophyta covered 59% of the upper intertidal zone while Phaeophyta covered 75% of the upper subtidal zone. These three groups, Chlorophyta, Rhodophyta and Phaeophyta covered the intertidal zones at ratios of 20%, 39% and, 41%, respectively. Findings of this study suggest that habitat structure of rocky substratum might significantly shape the zonation and, distribution patterns of seaweed communities in this marine ecosystem in the Bay of Bengal.