PRODUCTION RATE ESTIMATION OF MYCOSPORINE-LIKE AMINO ACIDS IN TWO ARCTIC MELT PONDS BY STABLE ISOTOPE PROBING WITH NAH(13)CO(3)

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 (MPs; closed and open type pond) in the western Arctic Ocean using a C-13 stable isotope tracer technique. The Research Vessel Araon visited ice-covered western-central basins situated at 82 degrees N and 173 degrees E in the summer of 2012, when Arctic sea ice declined to a record minimum. The average net carbon uptake rate of the phytoplankton in polycarbonate (PC) bottles in the closed MP was 3.24 mg C . m(-3) . h(-1) (SD = +/- 1.12 mg C . m(-3) . h(-1)), while that in the open MP 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 incubated PC bottles was highest (1.44 (SD = +/- 0.24) ng C . L-1 . h(-1)) in the open MP and lowest (0.05 (SD = +/- 0.003) ng C . L-1 . h(-1)) in the closed MP. The net production rate of shinorine and palythine in incubated PC bottles at the open MP presented significantly high values 0.76 (SD = +/- 0.12) ng C . L-1 . h(-1) and 0.53 (SD = +/- 0.06) ng C . L-1 . h(-1). Our results showed that high net production rate of MAAs in the open MP was enhanced by a combination of osmotic and UVR stress and that in situ net production rates of individual MAA can be determined using C-13 tracer in MPs in Arctic sea ice.