Coupling Organic Composition with Metaproteomics to Track the Functional Responses of Arctic Ocean Microbiomes to Carbon Inputs

The coupling of microbial "–omics" with geochemical measures are infrequent but have the potential to describe biogeochemical processes driving carbon preservation. Using shipboard incubations over 10 days, we followed two Arctic microbiomes (Bering Strait sub-surface and Chukchi Sea benthic) via measures of bacterial community composition and activity through metaproteomics together with changes to particulate organic composition. Comparative measures under conditions of either added or absence of algal organic matter followed functional responses under rapidly changing organic availability. A peak in functional dissimilarity occurred between the two Arctic microbiomes within one day after algal organic input and was primarily due to the increase in transcription, translation, protein transport and carboxylic acid metabolism by Bering Strait Alphaproteobacteria, Flavobacteria and Gammaproteobacteria. In contrast, organic removal from the Chukchi Sea microbiome led to ion transport and energy production largely associated with Gammaproteobacteria and functions related to energy production for polypeptide transport. Despite differences in community structure between the two regions, rapid inputs of algal organic matter drove functional convergence between the two microbiomes. Bacterial enzymatic activity (e.g. ester-specific hydrolases) increased within both microbiomes, with up to a 40% decline seen in highly unsaturated diatom fatty acids accompanied by an increase in bacterial lipid synthesis. Although enzymatic profiles showed that the bottom water community from the Chukchi Sea were less diverse than the Bering Strait, collective activity of the Chukchi Sea enzymes provided the functionality to degrade lipid substrates at similar rates. These findings show that despite significant difference in community taxonomy, organic degradation showed a high degree of functional consistency between the two microbiomes. It suggests that that Arctic Ocean bacterioplankton collected from different water masses and having differing taxonomy may nevertheless have a predictable order and high degree of functional consistency for organic matter degradation.