Size-fractioned primary productivity on the Mississippi-Alabama Shelf in Fall 2015

While net primary production measured using carbon-14 bicarbonate incorporation is common, the bulk values provide no significant information on which phytoplankton are most important to productivity. Although methods exist for taxon-specific productivity, these are usually laborious and costly. Filtering different size fractions as carbon-14 incubations are terminated, is a widely used strategy to provide information on the distribution of production among large (>5 μm) and small (<5 μm) phytoplankton. Such information is useful for biogeochemical modelers who typically divide phytoplankton into groups based on size.