Beaufort Sea in the Arctic Ocean has strong Mackenzie River plume, extensive area of submarine permafrost, and mud volcanoes. This study analyzed inorganic and organic matter concentrations in the surface (0-5 cm) and subsurface (5-60 cm) sediments, along with chemical and biological properties on the west and east transects, including mud volcano sites, in the Beaufort Sea. Aluminum oxide and potassium oxide typically increased from the coast to the open sea in west transect that has Mackenzie through and narrow shelves. On the contrary, there was an irregular trend in east transect, where mud volcanoes had much lower concentrations of aluminum oxide and potassium oxide than nearby sites. Redox-driven changes dominated pore water chemistry, and nitrate and nitrite concentrations in pore water reflected differences in oxygen penetration and organic matter decomposition across the shelf. Ammonium and phosphate maxima highlighted anaerobic microbial processes, particularly in the mud volcano regions where anoxic conditions enhanced ammonium and phosphate release. The high phosphate concentrations in pore water of mud volcano sediments are likely due to methane-driven release of particle-bound phosphate under reducing conditions. Moreover, total sulfur concentrations were four to seven times higher in the mud volcano sites as compared to other offshore sites, which could be due to the sulfur reduction coupled to anaerobic methane oxidation. Significant spatial trends in organic matter composition were revealed for mud volcano sediments using 15T FT-ICR MS, with molecular formula and compound group distributions reflecting differences in biological activity, sulfur cycling, and organic matter preservation from the surrounding sites. The distinguishing chemical and physical conditions of mud volcano sediments appear to produce distinct profiles of inorganic oxides, pore water nutrients, and sediment organic matter composition in the Arctic Ocean.  

 

Arctic,sediment,organic matter,nutrients