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要旨:
Marine bacteria are capable of thriving in all oceanic habitats, from several kilometers below the seafloor to the top millimeter of the ocean surface. Aquatic bacteria live also of organic matter point sources such as particles/aggregates and higher organisms. Pelagic bacteria consist of free-living bacteria that spend their whole lifecycles individually; and bacteria that spend most of their life attached to living/non living particles. So far, sampling strategies focus solely on the free-living bacterial fractions, overlooking the fact of complex lifestyles that marine bacteria may possess. Although there has been evidence that aggregates as well as their surrounding are sites and hot-spots of microbial processes, the microbial diversity in aggregates is yet to be understood.
In this study, for the first time, the bacterial diversity of individual particles > 300 μm was investigated. During the EUROPA cruise onboard R/V Polarstern, particles of anthropogenic origin and neuston were collected from the ocean surface applied the Manta trawl, in addition to water samples collected with CTD-rosette from 5 m below the ocean surface. Along the north-to-south transect in the Atlantic Ocean, 30 samples from 5 stations were analyzed. Here, we report a comprehensive comparison of bacterioplankton diversity between particles of anthropogenic origin and their surrounding neuston, as well as free-living and attached-living bacterial fractions, using standardized methods for pyrosequencing the partial bacterial 16S rRNA gene. The chemical nature some for the anthropogenic particles, suspected to be plastic material, was identified by Raman spectroscopy.
The results suggest that there are no specific populations inhabiting different aggregates attached on anthropogenic particles, as well as their surrounding sites. Although the study confirmed that microorganisms can live attached to anthropogenic particles and show a high diversity. The data also came in agreement with the expectation that the free-living and particle-associated bacterial populations show different diversity. Therefore, no clear difference was evident to support the hypothesis of specific bacteria populations inhabiting non-living aggregates with a potential of degradation. Further investigations have to be performed applying robust sampling methods in order to assess the whole spectrum of bacterial lifestyles, as well as the interactions with the organic matter.
