For aquatic ecosystems, CO 2 must first be dissolved in water before being used by primary producers. Calcium carbonate may precipitate out and get buried in ocean sediments. More carbon in dead organic matter than in living organisms. Except, release of C formerly stored in fossil fuels is perturbing atmospheric levels of CO 2 and influencing levels of primary production. Carbon Cycle Plant biomass large relative to phytoplankton biomass, but NPP on lands and in ocean are comparable.
P is depleted in soils.
On even longer time scales, there is a balance between weathering of rock, loss of P to marine sediments, and creation of new land. The conversion of atmospheric N 2 into inorganic nitrogen. Early in soil development, P is in mineral form. As it weathers, it becomes biologically available. The quality of the litter produced by plants depends on the nutrient status of the soils.