The role of biogenic calcium carbonate and silicate in the preservation of organic carbon

The sinking of particulate organic carbon out of the upper ocean and its preservation in sediments is one way the ocean acts as a sink for atmospheric carbon dioxide. In the water column, the sinking flux of organic matter is correlated with the sinking flux of mineral ballast, including biominerals. Here I present evidence that the organic template incorporated into biominerals during biomineralization is preferentially preserved as particles sink. In addition, this protein-rich organic template that aids mineral precipitation is a significant portion of preserved organic matter in environments that are characterized by high biomineral concentrations and low organic carbon concentrations. This research investigated one biogenic opal rich environment (the Southern Ocean) and two biogenic calcium carbonate rich environments (sediments of the Dry Tortugas and Scleractinian coral skeletons). Organic matter that is preserved within these biominerals represents an important archive of unaltered chemical and isotopic information. This research lays the groundwork to refine ongoing and future paleoceanographic investigations involving carbon and nitrogen isotopes. These isotopic studies will shed new light on the carbon cycle and nutrient dynamics of the present and past ocean.