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The key outputs of the marine carbon system are particulate organic matter (POC) and calcium carbonate (PIC) preservation as well as reverse weathering. [1] While there are regions with local loss of CO 2 to the atmosphere and hydrothermal processes, a net loss in the cycle does not occur.
Marine biogenic calcification is the biologically mediated process by which marine organisms produce and deposit calcium carbonate minerals to form skeletal structures or hard tissues. This process is a fundamental aspect of the life cycle of some marine organisms, including corals , mollusks , foraminifera , certain types of plankton , and ...
This is the origin of both marine and terrestrial limestone. [57] Calcium precipitates into calcium carbonate according to the following equation: Ca 2+ + 2HCO 3 − → CO 2 + H 2 O + CaCO 3 [112] The relationship between dissolved calcium and calcium carbonate is affected greatly by the levels of carbon dioxide (CO 2) in the atmosphere.
The carbonate pump is sometimes referred to as the "hard tissue" component of the biological pump. [45] Some surface marine organisms, like coccolithophores, produce hard structures out of calcium carbonate, a form of particulate inorganic carbon, by fixing bicarbonate. [46] This fixation of DIC is an important part of the oceanic carbon cycle.
The carbonate pump is sometimes referred to as the "hard tissue" component of the biological pump. [19] Some surface marine organisms, like coccolithophores, produce hard structures out of calcium carbonate, a form of particulate inorganic carbon, by fixing bicarbonate. [20] This fixation of DIC is an important part of the oceanic carbon cycle.
The balance of these carbonate species (which ultimately affects the solubility of carbon dioxide), is dependent on factors such as pH, as shown in a Bjerrum plot.In seawater this is regulated by the charge balance of a number of positive (e.g. Na +, K +, Mg 2+, Ca 2+) and negative (e.g. CO 3 2− itself, Cl −, SO 4 2−, Br −) ions.
Calcium carbonate is a precipitate from calcium and the bicarbonate ions, while the carbon is precipitates as limestone. [1] Many shallow marine environments are associated with carbonate factory zones, where processes that remove CO 2 from the water change bicarbonate ions into carbonate ions, supporting lime precipitation.
Marine calcifying organisms, such as mollusks and corals, are especially vulnerable because they rely on calcium carbonate to build shells and skeletons. [ 23 ] A change in pH by 0.1 represents a 26% increase in hydrogen ion concentration in the world's oceans (the pH scale is logarithmic, so a change of one in pH units is equivalent to a ...