Dataset: Presence and abundance of blue particles in Oceanic Flux Program (OFP) samples collected from 1984-2019 at the OFP mooring in the Sargasso Sea

The Oceanic Flux Program (OFP) sample collection involves three 0.5-square-meter (m²)PARFLUX Mark 8 sediment traps (McLane Labs, Falmouth, MA) with programmable, rotating sampling carousels that are affixed to the OFP mooring at depths of 500, 1500, and 3200 meters (m). The sediment traps continuously sample the sinking particle flux at a nominal biweekly integration period. Sample collection bottles affixed to the carousel are low density polyethylene (LDPE) and filled with seawater brine of ~40 grams per kilogram (g/kg) (40‰) poisoned with ultra-high purity mercuric chloride at a concentration of 0.74 millimoles per liter (mmol/L). After recovery, samples are refrigerated (at 4 degrees Celsius) until processing. Samples are fractionated into four size fractions (>1000, 500-1000, 125-500, and <125 micrometers (µm)).

Samples visually noted to contain blue particles were targeted for various analyses in this study. Most of the blue particle-containing samples have been processed and dried as described above. The blue particles in dried samples, identified based on color, shape, and size, were picked using a brush wetted with ethanol under a dissecting microscope. Additionally, in a few samples, the blue particle aggregates were picked out during processing and preserved in the trap collection brine. These blue particles were briefly rinsed with MilliQ water and then dried for analysis.