• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.47 no.6
• /
• pp.1026-1036
• /
• 2014

Real-time monitoring for environmental factors (temperature, salinity, chlorophyll-a, etc.) and fugacity of carbon dioxide ($fCO_2$) was conducted at an oyster Crassostrea gigas farm in Goseong Bay, south coast of Korea during 2-4th of November, 2011. Surface temperature and salinity were ranged from $17.9-18.7^{\circ}C$ and 32.7-33.8, respectively, with daily and inter-daily variations due to tidal currents. Surface $fCO_2$ showed a range of $390-510{\mu}atm$ and was higher than air $CO_2$ during the study period. Surface temperature, salinity and $fCO_2$ are showed significant correlations with chl.-a and nutrients, respectively. It means when chl.-a value is high in surface water of the oyster farm, active biological production consume $CO_2$ and nutrients from environments and produce oxygen, suggesting a tight feedback between biological processes and environmental reaction. Thus, factors affecting the surface $fCO_2$ were evaluated using a simple mass balance. Temperature and biological productions by phytoplankton are the main factors for $CO_2$ drawdown from afternoon to early night, while biological respiration increases seawater $CO_2$ at night. Air-sea exchange fraction acts as a $CO_2$ decreasing gear during the study period and is much effective when the wind speed is higher than $2-3m\;s^{-1}$. Future studies about organic carbon and biological production/respiration are required for evaluating the roles of oyster farms on carbon sink and coastal carbon cycle.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.16 no.3
• /
• pp.241-248
• /
• 2010

Hypoxic(oxygen-deficient) water masses are a key threat to the ecosystem of shallow marine coastal areas worldwide. The phenomena of hypoxia occurred at Gamak Bay, on the southeast coast of Korea, in late June 2007. In this paper, the physicochemical characteristics of seawater were surveyed for a period of hypoxic water mass disappearance. The hypoxic water mass was located between Sunso and the northwestern area of the inner bay. The dissolved oxygen(DO) concentrations of surface and bottom water were $1.3mgL^{-1}$ and less than $2mgL^{-1}$, respectively, in the hypoxic water masses, and $4.5{\sim}6.8mgL^{-1}$ and $3.8{\sim}6.0mgL^{-1}$ at the other oxygen-rich sample sites, respectively. Chlorophyll a concentrations were $4.9{\sim}25.3{\mu}gL^{-1}$ at the surface, $2.3{\sim}23.1{\mu}gL^{-1}$ in the middle, and $1.9{\sim}9.0{\mu}gL^{-1}$ at the bottom of the hypoxic water masses. When the hypoxic water mass appeared in Gamak Bay, it formed three different vertical types. The first type occurred throughout the water depth around Sunso. The second type developed from the bottom. The third type of hypoxic water mass was formed in the middle water layer when the inversion of water temperature occurred. The third type of phenomena appeared at only St. 9, St. 14 and St. 21 sites near the Hodo coast. Aquatic surface respiration of bottom-dwelling fishes such as the oriental goby(Acanthogobius flavimanus) was observed and many crustaceans were seen along the adjacent shore of the hypoxic water mass area. About 3,000 oriental gobies as well as many crustaceans died due to this event in Gamak Bay. The results of this study could provide fundamental data for the mechanism of hypoxic water masses in Gamak Bay.