Particulate organic carbon (POC) and particulate organic nitrogen (PON) concentrations were obtained from water samples filtered on precombusted (450°C for >5 hours) 47mm Whatmann GF/F (0.7 µm) filters. The filters were dried overnight at 60°C and vacuum-sealed for storage in aluminum foil kept at -20°C until analysis. To determine POC and PON concentrations, the filters were acidified with 200-350 µl HCl 2N to remove carbonates, dried at 60°C overnight and then burned on a pre-calibrated CHN analyzer (Perkin Elmer, combustion at 925°C) for determination of the CO2 produced (Doxaran et al. 2012; doi:10.5194/bg-9-3213-2012).

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