Abstract
BackgroundThe total bacterial community plays an important role in aquatic ecosystems. In this study, bacterial communities and diversity along the shores of the Upper Gulf of Thailand were first characterized. The association between bacterial communities and types of land use was also evaluated.ResultsThe bacterial communities and diversity of seawater in the Upper Gulf of Thailand, with regard to types of land use, were first revealed by using Illumina next-generation sequencing. A total of 4953 OTUs were observed from all samples in which 554 OTUs were common. The bacterial communities in sampling sites were significantly different from each other. The run-off water from three types of land use significantly affected the community richness and diversity of marine bacteria. Aquaculture sites contained the highest levels of community richness and diversity, followed by mangrove forests and tourist sites. Seawater physicochemical parameters including salinity, turbidity, TSS, total N, and BOD5, were significantly different when grouped by land use. The bacterial communities were mainly determined by salinity, total N, and total P. The species richness estimators and OTUs were positively correlated with turbidity. The top ten most abundant phyla and genera as well as the distribution of bacterial classes were characterized. The Proteobacteria constituted the largest proportions in all sampling sites, ranging between 67.31 and 78.80%. The numbers of the Marinobacterium, Neptuniibacter, Synechococcus, Candidatus Thiobios, hgcI clade (Actinobacteria), and Candidatus Pelagibacter were significantly different when grouped by land use.ConclusionsType of land use significantly affected bacterial communities and diversity along the Upper Gulf of Thailand. Turbidity was the most influential parameter affecting the variation in bacterial community composition. Salinity, total N, and P were the ones of the important factors that shaped the bacterial communities. In addition, the variations of bacterial communities from site-to-site were greater than within-site. The Proteobacteria, Bacteroidetes, Actinobacteria, Cyanobacteria, Verrucomicrobia, Euryarchaeota, Planctomycetes, Firmicutes, Deep Sea DHVEG-6, and Marinimicrobia were the most and common phyla distributed across the Upper Gulf of Thailand.
Highlights
The total bacterial community plays an important role in aquatic ecosystems
total suspended solid (TSS), total N, and total P of all sites ranged from 2.32 ± 0.03 to 102.00 ± 1.00 nephelometric turbidity units (NTUs), 22.00 ± 0.80 to 177.66 ± 5.50 mg/l, 0.13 ± 0.00 to 1.30 ± 0.13 mg/l, and 0.03 ± 0.00 to 0.10 ± 0.01 mg/l, respectively
Most of the bacterial sequence reads in marine sediments from Jeju Island, South Korea, were associated with the Proteobacteria and Bacteroidetes, followed by the Actinobacteria, Acidobacteria, and Firmicutes [20]. This is the first report of the bacterial communities and diversity associated with seawater along the Upper Gulf of Thailand that was categorized into three types of land use including mangrove forests, tourist sites, and aquaculture sites
Summary
The total bacterial community plays an important role in aquatic ecosystems. The Gulf of Thailand locates from 6°N to 13°30′N latitude and 99°E to 104°E longitude It is a semi-enclosed tropical marine embayment which is surrounded by the land masses of Thailand, Cambodia, Vietnam, and Malaysia [1]. It constitutes a part of the South China Sea and is characterized as an estuary of drowned river valley. The total bacterial community, which plays an important role in aquatic ecosystems, should be considered as a rigorous criterion for water quality to promote sustainable development. Marine bacterial community structure is affected by several factors such as inorganic nutrient concentration [6], N [7, 8], P [7], change in season, adjacent habitat [9], depth [8, 10], oxygen [10], protist predation pressure [11], salinity [7, 8, 12], dominance of algae, particulate organic carbon, Si (OH)4 [8], human disturbance, and sand mining activity [13]
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