Dissolved organic matter composition and bioavailability reflect ecosystem productivity in the Western Arctic Ocean

[摘要] Dissolved organic carbon (DOC) and total dissolved amino acids (TDAA) weremeasured in high (Chukchi Sea) and low (Beaufort Sea) productivity regionsof the western Arctic Ocean to investigate the composition andbioavailability of dissolved organic matter (DOM). Concentrations andDOC-normalized yields of TDAA in Chukchi surface waters were relativelyhigh, indicating an accumulation of bioavailable DOM. High concentrationsand yields of TDAA were also observed in the upper halocline of slope andbasin waters, indicating off-shelf transport of bioavailable DOM from theChukchi Sea. In contrast, concentrations and yields of TDAA in Beaufortsurface waters were relatively low, indicting DOM was of limitedbioavailability. Concentrations and yields of TDAA in the upper halocline ofslope and basin waters were also low, suggesting the Beaufort is not a majorsource of bioavailable DOM to slope and basin waters. In shelf waters ofboth systems, elevated concentrations and yields of TDAA were often observedin waters with higher chlorophyll concentrations and productivity. Surfaceconcentrations of DOC were similar (p > 0.05) in the two systemsdespite the contrasting productivity, but concentrations and yields of TDAAwere significantly higher (p < 0.0001) in the Chukchi than in theBeaufort. Unlike bulk DOC, TDAA concentrations and yields reflect ecosystemproductivity in the western Arctic. The occurrence of elevated bioavailableDOM concentrations in the Chukchi Sea implies an uncoupling between thebiological production and utilization of DOM and has important implicationsfor sustaining heterotrophic microbial growth and diversity in oligotrophicwaters of the central Arctic basins.

[学科分类] 地球化学与岩石