CS08 Biogeochemical Cycles
Date: Tuesday, June 11, 2002
Location: Poster Session - VCC
Soonmo/An, Kyungnam Univeristy, Masan, Republic Of Korea, sman@kyungnam.ac.kr
Choi, J, , Korea Ocean Research and Development, Ansan, Republic Of Korea, jwchoi@kordi.re.kr
Kim, G, , Gyeongsang University, Jinju, Republic Of Korea, 
Kwon, Y, , Kyungnam Univeristy, Masan, Republic Of Korea, kwonyt@kyungnam.ac.kr
Yang, W, , Kyungnam University, Masan, Republic Of Korea, babo@kyungnam.ac.kr
Gardner, W, , University of Texas, Marine Science Institute, Port Aransas, USA, gardner@utmsi.utexas.edu
McKarthy, M, , University of Texas, Marine Science Institute, Port Aransas, USA, markm@utmsi.utexas.edu
Denitrification and organic matter removal capacity in intertidal flat sediments
An extensive inter-tidal zone (horizontal expansion = ~20 km) that has a high tidal range (up to 10 m) has developed along the west and south fringe of the Korean peninsula. Oxic and anoxic conditions occur within short depth intervals in this sediment as a result of high organic-matter supply rates from land, efficient oxygen supply via direct contact to the atmosphere, and physical disturbances produced by tidal currents. Abundant benthic faunal activity adds heterogeneity in the sediments. Masan Bay is polluted from organic matter and metal input from nearby cities and limited water exchange with the open ocean. As a cleanup effort, large amounts of bottom sediment were dredged and deposited to Gapo area in 1994. A large intertidal flat (~ 1 km^2), which formed from the deposition, emerges and submerges every 12 hours. Biogeochemical processes have not been well studied in this region but complex redox conditions provide abundant sites for microbial degradation of organic matter and nutrient cycling. Overlying water exchange occurs via a narrow opening and this site provides ideal conditions to study biogeochemical processes in an intertidal flat with a macro-tidal regime. Water column concentrations of POM, DOM, DIN, DIP, heavy metals and suspended solid were measured every hour for 12 hours in the narrow openings of the Gapo area. Budgets of various chemicals relating to organic matter and nutrients were calculated from concentration differences between spring and ebb tides. The organic matter and heavy metal concentrations were higher in inflow than in outflow water. Inorganic nutrient (DIN, DIP) concentrations were higher in outflow than inflow water. The concentration changes with time were modeled using the concentration data and detailed topological information. Sediment oxygen demand, dissolved inorganic carbon (DIC) and DIN flux, and denitrification rates were measured using intact sediment cores and will be compared with budget calculations.