Abstract
16S rRNA gene amplicons were pyrosequenced to assess bacterioplankton community composition, diversity, and phylogenetic community structure for 17 stations in the northern Gulf of Mexico (nGoM) sampled in March 2010. Statistical analyses showed that samples from depths ≤100 m differed distinctly from deeper samples. SAR 11 α-Proteobacteria and Bacteroidetes dominated communities at depths ≤100 m, which were characterized by high α-Proteobacteria/γ-Proteobacteria ratios (α/γ > 1.7). Thaumarchaeota, Firmicutes, and δ-Proteobacteria were relatively abundant in deeper waters, and α/γ ratios were low (<1). Canonical correlation analysis indicated that δ- and γ-Proteobacteria, Thaumarchaeota, and Firmicutes correlated positively with depth; α-Proteobacteria and Bacteroidetes correlated positively with temperature and dissolved oxygen; Actinobacteria, β-Proteobacteria, and Verrucomicrobia correlated positively with a measure of suspended particles. Diversity indices did not vary with depth or other factors, which indicated that richness and evenness elements of bacterioplankton communities might develop independently of nGoM physical-chemical variables. Phylogenetic community structure as measured by the net relatedness (NRI) and nearest taxon (NTI) indices also did not vary with depth. NRI values indicated that most of the communities were comprised of OTUs more distantly related to each other in whole community comparisons than expected by chance. NTI values derived from phylogenetic distances of the closest neighbor for each OTU in a given community indicated that OTUs tended to occur in clusters to a greater extent than expected by chance. This indicates that “habitat filtering” might play an important role in nGoM bacterioplankton species assembly, and that such filtering occurs throughout the water column.
Highlights
The northern Gulf of Mexico supports some of the most economically and ecologically valuable marine and coastal ecosystems in North America (Rabalais et al, 1996)
Recent data derived from assessments of the Deep-water Horizon (DWH) oil spill have shown that bacterioplankton within an oil and gas plume at depths of about 1000–1200 m responded rapidly to hydrocarbon inputs, were dominated by γ-Proteobacteria, included taxa most closely related to genera known for hydrocarbon degradation, and were distinct from non-plume bacterioplankton
The trends in Proteobacteria resulted in a distinct change in the ratios of α-Proteobacteria/γ-Proteobacteria (α/γ) above and below 100 m (Figure 2)
Summary
The northern Gulf of Mexico (nGoM) supports some of the most economically and ecologically valuable marine and coastal ecosystems in North America (Rabalais et al, 1996). Carbon and nitrogen transformations are important, because of their contributions to the “microbial loop,” but because they affect the development and persistence of an extensive oxygendepleted or hypoxic zone (Pakulski et al, 1995; Chen et al, 2001; Dagg et al, 2006). This zone, which develops seasonally and threatens the integrity of both planktonic and benthic systems on the nGoM shelf, depends on elevated primary production supported by riverine nitrogen inputs, and high bacterial respiration rates that reduce oxygen concentrations. Recent data derived from assessments of the Deep-water Horizon (DWH) oil spill have shown that bacterioplankton within an oil and gas plume at depths of about 1000–1200 m responded rapidly to hydrocarbon inputs, were dominated by γ-Proteobacteria, included taxa most closely related to genera known for hydrocarbon degradation, and were distinct from non-plume bacterioplankton
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
