Abstract: The study showed that the migration and transformation of marine carbon had a close relation with the biogeochemical processes driven by various chemical factors.The growth and decline of nutrient concentration, pH,dissolved oxygen (DO),redox potential (Eh),SO₄^2-,and sulfur potential (Es) could change marine chemical environment,and thus,affect the migration and transformation of marine carbon.When the nutrient supply was adequate to the nutritional demand of phytoplankton,CO₂ was conveyed to deep sea through photosynthesis and organic matter oxidation,which caused the decrease of sea water P_CO2 and the increase of seaair CO₂ flux and organic carbon output,making the sea area as a CO₂ sink.But,the increasing acidification of marine environment caused by CO₂ dissolution and organic matter degradation brought about the solubility augmentation of carbonate in seawater.Moreover,the mineralization of organic carbon was coupled with the changes of DO,Eh,SO₄^2- and Es,and the deposition and burial process of carbon in sediments.In sea water body,high DO and high Eh accelerated the transformation from inorganic carbon to organic carbon,while in sediment,high SO₄^2- was adverse to the burial of organism with low DO and low Eh.

Key words: Black soil, Long term fertilization, Application of recycled nutrients, Crop yield