Water column bottle samples at multiple depths are taken during CalCOFI cruises (since 2004, ongoing) at various CTD stations, filtered, and stored at -20°C. Measurements of particulate organic carbon (POC) and nitrogen (PON) are performed onshore in the lab where samples are acidified, dried and analyzed by high-temperature combustion. The sample and tin capsule react with oxygen and combust at 1000°C, and the sample is broken down, thus converting organic carbon to CO2 and reducing nitrogen oxides to N2 gas. Both gases are measured by thermal conductivity. Samples analyzed within the CCE constrain the mean C:N ratio of small particulates and by difference relative to measured living biomass, the biomass of suspended detritus.