CCE LTER measures particulate organic carbon (POC) and nitrogen (PON) by high-temperature combustion. Samples analyzed within the California Current Ecosystem constrain the mean C:N ratio of small particulates and by difference relative to measured living biomass, the biomass of suspended detritus.
Complete methods of POC and PON determination can be found here.
For the analysis of particulate organic carbon and nitrogen (POC/PON) 4 liters of seawater are filtered on glassfiber filters and stored at -20°C for analysis ashore. Ashore samples are acidified, dried and analyzed by high-temperature combustion (1000°C) on an ECS 4010 CHNSO Analyzer. The sample and tin capsule react with oxygen and combust at 1000°C. 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.
POC/PON samples are collected for 66 CalCOFI stations and 9 SCCOOS stations located in the CCE. Three to eight depths are sampled. POC/PN samples are collected in 0.5, 1.04 or 2.2 Liter, brown polypropylene bottles. Smaller volumes are collected when high chlorophyll concentrations are measured from the CTD fluorometer. High concentrations are typically measured around the coastal stations. 3.2. Samples are filtered on precombusted Whatman GF/F 25mm under low vacuum pressure (40 mm Hg). 3.3. Filter is removed, folded in half with the particulate part inside the fold and wrapped in precombusted aluminum foil. 3.4. Samples are stored in Liquid Nitrogen and transferred post cruise to a -20°C freezer until processed.