Drivers shaping the diversity and biogeography of total and active bacterial communities in the South China Sea.
Bottom Line: Although the composition of both the total and active bacterial community was strongly correlated with environmental factors and weakly correlated with geographic distance, the active bacterial community displayed higher environmental sensitivity than the total community and particularly a greater distance effect largely caused by the active assemblage from deep waters.This might be due to a high competition between active bacterial taxa as indicated by our community network models.Based on these analyses, we speculate that high competition could cause some dispersal limitation of the active bacterial community resulting in a distinct distance-decay relationship.
Affiliation: State Key Laboratory of Marine Environmental Sciences, Xiamen University, Xiang'an, Xiamen, 361101, China; Institute of Marine Microbes and Ecospheres, Xiamen University, Xiang'an, Xiamen, 361101, China.Show MeSH
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Mentions: Cyanobacterial sequences were retrieved from almost all DNA and RNA samples in the upper 1000 m, but at low abundance in the deep-water samples. A cluster pattern distinctly different from the heterotrophic bacterial assemblage was found in the NMDS and UPGMA tree of the cyanobacterial DNA- and RNA-based libraries. No depth-related distribution pattern of the cyanobacterial assemblages was obtained. Coastal DNA-based communities formed three clusters (Fig.3a), one cluster including communities of the estuarine sites P1 and P2 at 37% similarity, one cluster of site A3 at 81% similarity and one cluster of sites A4 to A7 at 84% similarity, in which open ocean communities from sites S11 and S12 near the Luzon Strait were also included (Fig.3a). Satellite altimetric history indicated that a strong cyclonic eddy was present near the Luzon Strait during our sampling with relatively high chl a concentrations (0.5–0.6 μg L−1 at 5 m). Consequently, episodic input of nutrients from deep water might have shaped the similar cyanobacterial communities at sites S11 and S12, for example highly abundant Synechococcus (Fig.4). Open ocean communities from sites A8, S9 and S10 clustered separately at 47% similarity, together with the bottom community of site A6. The chl a maximum layer (75 m) and the bottom of the euphotic zone (100 m) of site S9 were consistently distinct from adjacent sites in both the DNA- (at 95% similarity) and RNA-based (at 99% similarity) NMDS, as was the A3 site. In addition, the cyanobacterial RNA libraries formed one open ocean cluster including communities from sites A8, S9, S10 and S12 at 81% similarity and one large cluster with coastal and open ocean samples at 40% similarity, in which the estuarine sites P1 and P2 were also included (Fig.3b). Significant differences between pairwise clusters were observed using the amova test (P < 0.05).
Affiliation: State Key Laboratory of Marine Environmental Sciences, Xiamen University, Xiang'an, Xiamen, 361101, China; Institute of Marine Microbes and Ecospheres, Xiamen University, Xiang'an, Xiamen, 361101, China.