An Assessment Of Current And Future Methodologies For The Collection, Measurement, And Processing Of Discrete Particulate Organic Carbon (POC) Samples

Particulate Organic Carbon (POC), although it represents a small portion of the total carbon in the ocean, plays an important role in carbon sequestration due to the biological pump. Phytoplankton, the most important component of POC, are responsible for about half of the global primary production. Therefore, it is an imperative to understand the global distribution of POC in the ocean, and its role in the functioning of the biological carbon pump. Observations from satellite missions (SeaWIFS, MODIS, PACE) provide an opportunity to resolve these questions. Although empirical remote sensing algorithms to quantify POC from space exist, error inherent to the in situ measurements of the POC that were used to tune the algorithms has not been assessed. Previous studies have listed several potential causes for the observed discrepancies in POC measurements. They evaluate different aspects of sampling techniques and filtration approaches, as well as the potential influences of dissolved organic carbon (DOC) and particulate inorganic carbon (PIC) to the measured carbon content designated as POC. Our preliminary results indicate that twenty to thirty percent of the mass of carbon measured as POC on GF/F filters collected from oligotrophic waters may be due to the retention of DOC or other factors. Current community protocols do not outline a technique that accounts for these discrepancies. The intent of this research was to address these and other issues, and provide some framework for the establishment of a POC working group coordinated by the NASA Field Support Group to develop a protocol document that addresses the measurement of POC from sampling to final value reported.