Spatial variations in time-integrated plankton metabolic rates in Sagami Bay using triple oxygen isotopes and O₂:Ar ratios

Abstract

Plankton metabolic rates, such as rates of gross, net community production and community respiration, were measured in the surface waters using triple oxygen isotopes and O₂:Ar ratios. The 17D anomaly showed clear coastal and offshore gradients that were consistent with the distribution of chlorophyll a and oxygen saturation. Gross Primary Production (GPP) rates in coastal regions were several times higher than offshore regions, and the net-to-gross production ratio (N:G) indicated that coastal regions were net autotrophic, whereas offshore regions were net heterotrophic. On a seasonal scale, about 73% of the phytoplankton-produced carbon was respired. Based on floating-sediment-trap data, export production to the aphotic zone was about 12-20 % of the GPP; the rest accumulated as Dissolved Organic Carbon (DOC) or was respired.