Sediment Oxygen Consumption Rate and Hydrogen Sulfide Release by Dissolved Oxygen Depletion in Hypoxic Area of the Gamak Bay, Korea

Abstract

요 약 핵심용어 : 가막만, 황화수소, 빈산소, 퇴적물 산소소모율 AbstractThis study investigated sediment oxygen consumption rates and geochemical characteristics of sediment in hypoxic area of the Gamak Bay based on the chamber experiments and geochemical analyses. The organic carbon contents of surface sediment in the Gamak Bay showed that the inner bay area has higher organic carbon content than those of the outer bay. They toward the outer bay, contents dropped off. The vertical profiles of calcium carbonate (CaCO3) content at piston core sediment assumed that the hypoxia have been frequently occurred during past century in the northern inner bay. The benthic chamber experiments were conducted in February, May, August and November 2010, 2011 in the hypoxic area of the Gamak Bay. In the sediment incubation experiment with chamber at site C3 in the northern inner bay and site C17 in the southern outer bay, the sediment oxygen consumption rate ranged from 3.98 mmol m

C, N, and P Mass Balances in the Bottom Seawater–Surface Sediment Interface in the Reducing Environment due to Anoxic Water of Gamak Bay, Korea

“…Organic matter produced through a series of blooms settles at the surface sediments [9,10], and oxygen consumption is required for bacterial activity to decompose the organic matter [8,[11][12][13]. Concomitantly, the strong stratification in the water column causes the bottom hypoxia by inhibiting the oxygen supply to the bottom water [14,15].…”

“…Under oxygen-deficient conditions, marine microbes facultatively gain energy by oxidizing organic matter and other reduced species such as sulfide and manganese [22]. Ammonification and dissimilatory nitrogen reduction to ammonium (DNRA) produce ammonium nitrogen [23][24][25][26], and hydrogen sulfide is produced from sulfate-reducing bacteria-mediated reactions [12,22]. Hydrogen sulfide can be removed through the oxidation processes in the aerobic water column, but hypoxic or anoxic environments drive the accumulation of hydrogen sulfide, affecting the marine ecosystem and often forming blue tides [27,28].…”

“…Gamak Bay, located in the southern coastal waters of Korea, represents the eutrophic aspects described above. Previous studies have investigated eutrophication status and the formation of bottom hypoxia in Gamak Bay [10,12,36,37]. However, recent patterns of hypoxia or anoxia demonstrating the earlier formation and longer duration in the bay have not been considered [9,13].…”

“…The researchers have also emphasized that hypoxia and nutrient elution from sediments are the primary factors of eutrophication in this bay [9,10,12,13]. Nevertheless, C, N, and P mass balances under reducing environments in the bottom water-surface sediment interface were rarely determined for Gamak Bay.…”

“…Nevertheless, C, N, and P mass balances under reducing environments in the bottom water-surface sediment interface were rarely determined for Gamak Bay. Notably, previous studies were restricted mainly to organic carbon cycles, or ignored the ecological function of resuspension, which play an essential role in the perspective of mass balances [12,33]. In the bay, for ~100 years, hypoxia and anoxia have regularly been observed during every summer in the bay [12].…”