moles_of_organic_mercury_per_unit_mass_of_phytoplankton_expressed_as_carbon mol kg-1 [MLKG] The construction "moles_of_X_per_unit_mass_in_Y" is also called "molality" of X in Y, where X is a material constituent of Y. A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "Organic mercury" describes a family of chemical species in which mercury atoms covalently bonded to carbon-containing groups, forming organomercury compounds (e.g., methylmercury (MeHg), monomethylmercury (MMHg), dimethylmercury (DMHg), ethylmercury (EtHg)). Phytoplankton are algae that grow where there is sufficient light to support photosynthesis. 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.