text: In most open ocean ecosystems only a small fraction of organic matter reaches the seafloor. Biological activity in the photic zone of most water bodies tends to recycle material so well that only a small fraction of organic matter ever sinks out of that top photosynthetic layer. Remineralisation within this top layer occurs rapidly and due to the higher concentrations of organisms and the availability of light, those remineralised nutrients are often taken up by autotrophs just as rapidly as they are released.
  What fraction does escape varies depending on the location of interest. For example, in the North Sea, values of carbon deposition are ~1% of primary production while that value is <0.5% in the open oceans on average.  Therefore, most of nutrients remain in the water column, recycled by the biota. Heterotrophic organisms will utilize the materials produced by the autotrophic (and chemotrophic) organisms and via respiration will remineralise the compounds from the organic form back to inorganic, making them available for primary producers again.
  For most areas of the ocean, the highest rates of carbon remineralisation occur at depths between  in the water column, decreasing down to about 1,200 m where remineralisation rates remain pretty constant at 0.1 μmol kg yr. As a result of this, the pool of remineralised carbon (which generally takes the form of carbon dioxide) tends to increase in the photic zone.
  Most remineralisation is done with dissolved organic carbon (DOC). Studies have shown that it is larger sinking particles that transport matter down to the sea floor while suspended particles and dissolved organics are mostly consumed by remineralisation. This happens in part due to the fact that organisms must typically ingest nutrients smaller than they are, often by orders of magnitude. With the microbial community making up 90% of marine biomass, it is particles smaller than the microbes (on the order of ) that will be taken up for remineralisation.