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Unraveling the Unseen Players in the Ocean - A Field Guide to Water Chemistry and Marine Microbiology
Published on: November 5, 2014
Linking hydrocarbon gradients to microbial community variation across full-depth water columns in the Western Pacific
Lijia Jiang1, Chunlei Chen2, Songtao Hu3
1Institute of Marine Biology and Pharmacology, Ocean College, Zhejiang University, Zhoushan, Zhejiang, 316021, PR China; State Key Laboratory for Quality and Safety of Agro-Products, Zhejiang Provincial Key Laboratory of Agricultural Microbiomics, Institute of Environment, Resource, Soil and Fertilizer, Zhejiang Academy of Agricultural Sciences, Hangzhou, PR China.
Abstract:
Hydrocarbons are widely distributed in marine environments and may influence microbial communities even at the low concentrations typically found in non-contaminated marine environments, yet their vertical patterns and ecological implications in oligotrophic open-ocean systems remain poorly understood. In this study, we investigated six full-depth pelagic water-column profiles (maximum depths ranging from 1000 m to 5900 m) in the Western Pacific Ocean, integrating measurements of aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) with microbial community composition, diversity, and assembly analyses across 44 samples. The results showed that n-alkanes exhibited clear depth-related enrichment, particularly for long-chain homologues, likely associated with particle-mediated transport, whereas PAHs displayed more variable vertical patterns influenced by multiple processes. Molecular diagnostic indices indicated predominantly pyrogenic sources, suggesting potential transformation during vertical transport. Hydrocarbon gradients were associated with shifts in microbial community composition and diversity, accompanied by changes in predicted functional potential, with higher concentrations favoring hydrocarbon-associated and heterotrophic taxa. Moreover, community assembly analysis indicated that hydrocarbon variability governed niche-based transitions in microbial communities; elevated concentrations decoupled microbial taxa from their environmental niches, shifting the assembly processes from dispersal limitation to drift dominance. This transition was further supported by a structural simplification of co-occurrence networks, characterized by reduced connectivity and complexity under hydrocarbon pressure. These findings suggest that even background hydrocarbon variability may influence microbial community organization and assembly in oligotrophic marine environments. Overall, this study provides new insights into how natural hydrocarbon variability may shape microbial community organization and assembly processes in oligotrophic open-ocean ecosystems.
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