This work aimed to explore evaluated the effects of the increased of hydrostatic pressure on a defined bacterial community on aggregates formed from an axenic culture of marine diatoms by simulating sedimentation to the deep sea by increase of hydrostatic pressure up to 30 bar (equivalent to 3000 m water depth) against control at ambient surface pressure. Our hypothesis was that microbial colonization and community composition and thus microbial OM turnover is greatly affected by changes in hydrostatic pressure during sinking to the deep ocean.

Determination of Organic and Inorganic Carbon Content and Nitrogen content Aggregate samples were concentrated onto precombusted Whatman GF/F glass filters and analyzed for organic carbon. The filters were dried at 60°C overnight. After weighting, a section of each filter was placed into a silver cup and decarbonated with 1 M HCl to determine the organic carbon content. The samples were dried at 60°C and the process repeated until bubbling stopped. The cups were closed and compacted into spheres. These samples were analyzed with a Euro-EA Elemental analyzer (Hekatech) standardized with acetanilide. The inorganic carbon content was determined from the difference between the total carbon content and the organic carbon content.