Production rate estimation of mycosporine‐like amino acids in two A rctic melt ponds by stable isotope probing with NAH 13 CO 3

The net carbon uptake rate and net production rate of mycosporine‐like amino acids ( MAA s) were measured in phytoplankton from 2 different melt ponds ( MP s; closed and open type pond) in the western A rctic O cean using a 13 C stable isotope tracer technique. The Research Vessel Araon visited ice‐covered western‐central basins situated at 82°N and 173°E in the summer of 2012, when A rctic 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 MAA s 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 MAA s 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 13 C tracer in MP s in A rctic sea ice.