Monosaccharide composition of POM-derived carbohydrates in the western North Atlantic Ocean

Collection of particulate organic matter Particulate organic matter (POM) was collected by filtering between 5-15 liters of water through a 47-mm pre-combusted (400℃ for 6 hours) glass fiber filter (GF/F; nominal pore size 0.7 μm; for volumes filtered at each depth and station, see the dataset). Monosaccharide composition of POM The monosaccharide constituents of total combined carbohydrates (i.e., polysaccharides, glycoproteins, glycolipids, etc.) of POM (collected as described above) were determined from triplicate filter punches (11.2 mm diameter). Samples were acid hydrolyzed by adding 1 M HCl to each filter piece, flame sealing each piece in a glass ampule, and placing the ampules in a drying oven at 100°C for 24 hours. After acid hydrolysis, the samples were dried on a speed-vac and resuspended in Milli-Q to remove any HCl. The quantity and composition of the resulting monosaccharides were measured using a modified protocol (Engel and Handel (2011), as described by Vidal-Melgosa et al. (2021)). In brief, neutral, amino, and acidic sugars were quantified using high performance anion exchange chromatography on a Dionex ICS-5000+ system with pulsed amperometric detection (HPAEC-PAD). Peaks were identified using retention times of purified monosaccharide standards; abundance was quantified from standards using the peak area for a given monosaccharide. The limit of detection for monosaccharides varied from 0.5 – 1 ug/L, depending on the specific monosaccharide measured.