number_concentration_of_mature_individuals_of_biological_taxon_in_sea_water m-3 [PCUM] "Number concentration" means the number of particles or other specified objects per unit volume. Mature individuals refer to individuals that have reached sexual maturity. "Biological taxon" is a name or other label identifying an organism or a group of organisms as belonging to a unit of classification in a hierarchical taxonomy. There must be an auxiliary coordinate variable with standard name biological_taxon_name to identify the taxon in human readable format and optionally an auxiliary coordinate variable with standard name biological_taxon_identifier to provide a machine-readable identifier. See Section 6.1.2 of the CF convention (version 1.8 or later) for information about biological taxon auxiliary coordinate variables.