mole_concentration_of_particulate_organic_matter_expressed_as_carbon_in_sea_water mol m-3 [MLM3] Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction mole_concentration_of_X_in_Y, where X is a material constituent of Y. A chemical or biological species denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". The phrase "expressed_as" is used in the construction A_expressed_as_B, where B is a chemical constituent of A. It means that the quantity indicated by the standard name is calculated solely with respect to the B contained in A, neglecting all other chemical constituents of A.