Abstract

Coastal marine sites were examined for the occurrences and diversity of indigenous bacterial populations using high resolution 16S rRNA gene pyrosequencing approach to further understand the ecological importance of environmental variables. Samples containing slurries of seawater and sediments were collected from nine different sites along the north Atlantic Ocean in Monrovia, Liberia and were divided into three spatially distinct groups. The bacterial assemblages were found to be quite diverse in their occurrences among the examined sites. The majority of the sequences that dominated among the assemblages were associated with members of the Actinobacteria (1.3 to 4.8%), Bacteriodetes (2.9 to 5.8%), Acidobacteria (8.0 to 13.7%), Planctomycetes (15.3 to 28.8%), and Proteobacteria (40.7 to 48.8%). Gammaproteobacteria was the most abundant bacterial class, representing between 29 and 39% of the operational taxonomic units (OTUs) in all the coastal sites, while members belonging to the Planctomycetia, ranged between 10 and 18.8%, were relatively more abundant in the southern region of Monrovia which is mostly influenced by a freshwater lagoon. Alpha- and beta diversity indices as well as rarefaction analysis were used to determine the species richness, evenness and coverage among the sites. Canonical correspondence analysis (CCA) and clustering using UPGMA (Unweighted pair group method with arithmetic mean) revealed the separation of the OTUs into groups probably based on the influence of various site-specific environmental variables at the coastal sites.

Key words: Marine coast, bacterial assemblages, 16S rRNA gene sequencing, diversity.