Size-fractionated chlorophyll from water column bottle samples collected during NES-LTER Transect cruises, ongoing since 2017.

Size-fractionated chlorophyll a and phaeopigments are measured from discrete bottle samples collected during CTD-rosette casts on Northeast U.S. Shelf Long-Term Ecological Research (NES-LTER) Transect cruises (ongoing since 2017), as a proxy for phytoplankton biomass. Sampling frequency is approximately seasonal. Samples were processed by three lab groups using different methods. Size fractions in addition to whole seawater (>0.7 micron) include >5 , <10, >10, and >20 microns with some samples pre-filtered <200 microns. Pigments were analyzed using fluorometers in which fluorescence was measured versus a blank and a standard, and final concentrations were calculated in micrograms per liter (or mg per cubic meter). Some of the data are from cruises in collaboration with the Ocean Observatories Initiative (OOI).