Production rate estimation of mycosporine-like amino acids in two Arctic melt ponds by stable isotope probing with NAH13CO3

Abstract

The net carbon uptake rate and net production rate of mycosporine-like amino acids (MAAs) were measured in phytoplankton from 2 different melt ponds (closed and open type pond) in the western Arctic Ocean using a¹³C stable isotope tracer technique. The Research Vessel Araon visited icecovered western-central basins situated at 82°N and 173°E in the summer of 2012, when Arctic sea ice declined to a record minimum. The average net carbon uptake rate of the hytoplankton inpolycarbonate (PC)bottles in the closedmelt pond was 3.24 mg C ·m^-3· h^-1(SD = ± 1.12 mg C · m^-3 · h^-1), while that in the open melt pond was 1.3 mg C · m^-3 h^-1(SD = ± 0.05 mg C · m^-3？ h^-1). The net production rate of total MAAs in incubatedPC bottles was highest (1.44 (SD= ±0.24) ngC ？L^-1？ h^-1) in the open melt pond and lowest (0.05 (SD= ±0.003) ngC · L^-1· h^-1) in the closed melt pond. The net production rate of shinorine and palytine in incubatedPC bottlesat the open melt pond presented significantly high values 0.76 (SD= ±0.12) ngC · L^-1 · h^-1 and 0.53 (SD= ±0.06) ngC · L^-1 · h^-1. Our results showed that high net production rate of MAAs in the open melt pond was enhanced by a combination of osmotic and UVR stress and thatin situ net production rates of individual MAA can be determined using 13C tracer inmelt ponds in Arctic sea ice.