• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.4
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• pp.252-261
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• 2012

To determine the temporal variations of submarine groundwater discharge (SGD) and SGD-driven nutrients inputs, we measured the seepage rate and the nutrient concentrations of pore water/groundwater in Bangdu Bay of Jeju Island at two and three month intervals from September 2009 to September 2010. The seepage rate of groundwater ranged from 0 to 330 cm/day (average ~170 cm/day) during the five sampling periods, which increased sharply from high tide to low tide due to changes in hydraulic pressure gradient between water table in land and water sea level in the coastal ocean by the tidal cycles. The submarine inputs of groundwater were also relatively higher in summer than in winter. The nutrient fluxes from SGD were about 90~100%, 70~95%, and 65~100% of the total input (except from open ocean waters) for dissolved inorganic nitrogen (DIN), phosphorus (DIP), and silicate (DSi), respectively, potentially supporting about 0.9~33 g $carbon/m^2/day$ of new primary production in Baugdu Bay. Thus, our study suggests that SGD-driven nutrients may play an important role in the eutrophication and biological production in the coastal ocean of Jeju Island.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.6
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• pp.679-686
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• 2010

To investigate the contribution of macroalgae to biogeochemical nutrients and carbon cycles, we measured the uptake rates of nutrients and $CO_2$ by Undaria pinnatifida using an incubation method in an acrylic chamber. From January to March 2010, U. pinnatifida was sampled at Ilkwang, a well-known area of macroalgae culture in Korea. The initial and final concentrations of nutrients, dissolved oxygen, total alkalinity, and pH of the chamber water were measured, and production/uptake rates were calculated using concentration changes, chamber volume, and incubation time. The production rate of dissolved oxygen by U. pinnatifida (n = 32) was about $5.4{\pm}4.0\;{\mu}mol\;g_{fw}^{-1\;}h^{-1}$. The uptake rate of total dissolved inorganic carbon (TDIC), calculated by total alkalinity and pH, was $7.9{\pm}6.5\;{\mu}mol\;g_{fw}^{-1}\;h^{-1}$. Nutrients uptake averaged $141.7{\pm}119.2$ nmol N $g_{fw}^{-1}\;h^{-1}$ and $15.0{\pm}9.1$ nmol P $g_{fw}^{-1}\;h^{-1}$. A positive linear correlation ($r^2$ = 9.6) existed between the production rate of dissolved oxygen and the uptake rate of total dissolved inorganic carbon, suggesting that these two factors serve as good indicators of U. pinnatifida photosynthesis. The relationships between fresh weight and uptake rates of nutrients and $CO_2$ suggested that younger specimens (<~50 g fresh weight) are much more efficient at nutrients and $CO_2$ uptake than are specimens >50 g. The amount of carbon uptake by the total biomass of U. pinnatifida in Korea during the year of 2008 was about 0.001-0.002% of global ocean carbon uptake. Thus, more research should be focused on macroalgae-based biogeochemical cycles to evaluate the roles and contributions of macroalgae to the global carbon cycle.

• Korean Journal of Remote Sensing
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• v.27 no.3
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• pp.235-258
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• 2011

The purpose of this study is to investigate climatological variations from the temporal and spatial surface particulate organic carbon (POC) estimates based on SeaWiFS spectral radiance, and to determine the physical mechanisms that affect the distribution of pac in the Gulf of Mexico. 7-year monthly mean values of surface pac concentration (Sept. 1997 - Dec. 2004) were estimated from Maximum Normalized Difference Carbon Index (MNDCI) algorithm using SeaWiFS data. Synchronous 7-year monthly mean values of remote sensing data (sea surface temperature (SST), sea surface wind (SSW), sea surface height anomaly (SSHA), precipitation rate (PR)) and recorded river discharge data were used to determine physical forcing factors. The spatial pattern of POC was related to one or more factors such as river runoff, wind-derived current, and stratification of the water column, the energetic Loop Current/Eddies, and buoyancy forcing. The observed seasonal change in the POC plume's response to wind speed in the western delta region resulted from seasonal changes in the upper ocean stratification. During late spring and summer, the low-density river water is heated rapidly at the surface by incoming solar radiation. This lowers the density of the fresh-water plume and increases the near-surface stratification of the water column. In the absence of significant wind forcing, the plume undergoes buoyant spreading and the sediment is maintained at the surface by the shallow pycnocline. However, when the wind speed increases substantially, wind-wave action increases vertical motion, reducing stratification, and the sediment were mixed downward rather than spreading laterally. Maximum particle concentrations over the outer shelf and the upper slope during lower runoff seasons were related to the Loop Current/eddies and buoyancy forcing. Inter-annual differences of POC concentration were related to ENSO cycles. During the El Nino events (1997-1998 and 2002-2004), the higher pac concentrations existed and were related to high runoffs in the eastern Gulf of Mexico, but the opposite conditions in the western Gulf of Mexico. During La Nina conditions (1999-2001), low Poe concentration was related to normal or low river discharge, and low PM/nutrient waters in the eastern Gulf of Mexico, but the opposite conditions in the western Gulf of Mexico.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.23 no.1
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• pp.32-48
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• 2018

The mechanisms of $CH_4$ uptake into and release from the ocean are not well understood due mainly to complexity of the biogeochemical cycle and to lack of regional-scale and/or process-scale observations in the marine boundary layers. Without complete understanding of oceanic mechanisms to control the carbon balance and cycles on a various spatial and temporal scales, however, it is difficult to predict future perturbation of oceanic carbon levels and its influence on the global and regional climates. High frequency, high precision continuous measurements for carbon isotopic compositions from dissolved $CH_4$ in the surface ocean and marine atmosphere can provide additional information about the flux pathways and production/consumption processes occurring in the boundary of two large reservoirs. This paper introduces recent advances on optical instruments for real time $CH_4$ isotope analysis to diagnose potential applications for in situ, continuous measurements of carbon isotopic composition of dissolved $CH_4$. Commercially available, three laser absorption spectrometers - quantum cascade laser spectroscopy (QCLAS), off-axis integrated cavity output spectrometer (OA-ICOS), and cavity ring-down spectrometer (CRDS) are discussed in comparison with the conventional isotope ratio mass spectrometry (IRMS). Details of functioning and performance of a CRDS isotope instrument for atmospheric ${\delta}^{13}C-CH_4$ are also given, showing its capability to detect localized methane emission sources.

• Ocean and Polar Research
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• v.33 no.3
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• pp.211-221
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• 2011

Contents of biogenic components [opal, $CaCO_3$, TOC (total organic carbon)] were measured in Core LHB-3PC sediments collected off Lutzow-Holm Bay, in order to understand glacial-interglacial cyclic variation of the high-latitude surface-water paleoproductivity, in the Indian Sector of the Southern Ocean. An age model was established from the correlation of ARM/IRM ratios of Core LHB-3PC with LR04 stack benthic ${\delta}^{18}O$ records, in complement with radiocarbon isotope ages and biostratigraphic Last Appearance Datum (LAD). The core-bottom age was estimated to be about 700 ka. Although the $CaCO_3$ content is very low less than 1.0% throughout the core, the opal and TOC contents show clear glacial-interglacial cyclic variation such that they are high during the interglacial periods (7.2-50.3% and 0.05-1.00%, respectively) and low during the glacial periods (5.2-25.2% and 0.01-0.68%, respectively). According to the spectral analysis, the variation of opal content is controlled mainly by eccentricity forcing and subsequently by obliquity forcing during the last 700 kyrs. The opal contents of Core LHB-3PC also represent the apparent Mid-Pleistocene Transition (MPT)-related climatic variation in the glacial-interglacial cycles. In particular, the orbital variation of the opal contents shows increasing amplitudes since marine isotope stage (MIS) 11, which defines one of the important paleoclimatic events during the late Quaternary, called the "Mid-Brunhes Event". Based on the variation of the opal contents in Core LHB-3PC, we suggest that the surface-water paleoproductivity in the Indian Sector of the Southern Ocean followed the orbital (glacial-interglacial) cycles, and was controlled mainly by the extent of sea ice distribution during the last 700 kyrs.

• Journal of Ocean Engineering and Technology
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• v.20 no.1 s.68
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• pp.55-62
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• 2006

Recently, pollution by development in coastal areas is going from bad to worse. The Korean government is attempting to make policies that prevent water pollution, but it is still difficult to say whether such measures are lowering pollution to an acceptable level. More specifically, the general investigation that has been done in KOREA does not accurately reflect the actual conditions of pollution in coastal areas. An investigation that quantitatively assesses water quality management using rational prediction technology must be attempted, and the ecosystem model, which incorporates both the 3-dimensional hydrodynamic and material cycle models, is the only one with a broad enough scope to obtain accurate results. The hydrodynamic model, which includes advection and diffusion, accounts for the ever-changing flow and (quality) of water in coastal areas, while the material cycle model accounts for pollutants and components of decomposition as sources of the carbon, phosphorus, and nitrogen cycles. In this paper, we simulated the rates of dissolved oxygen (DO), chemical oxygen demand (COD), total nitrogen(T-N) and total-phosphorous(T-P) in Korea's Ulsan Area. Using the ecosystem model, we did simulations using a specific set of parameters and did comparative analysis to determine those most appropriate for the actual environmental characteristics of Ulsan Area. The simulation was successful, making it now possible to predict the likelihood of coastal construction projects causing ecological damage, such as eutrophication and red tide. Our model can also be used in the environmental impact assessment (EIA) of future development projects in the ocean.

• Ocean and Polar Research
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• v.41 no.3
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• pp.159-168
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• 2019

Understanding the interaction between climate and the water cycle is critical especially in a drought sensitive region such as California. This study explored hydrologic changes in central and southern California in relation to the glacial-interglacial climate cycles over the last 30 thousand years. To do this, we reconstructed paleovegetation using plant wax carbon isotopic compositions (${\delta}^{13}C$) preserved in marine sediment cores retrieved from the central California continental shelf (ODP Site 1018) and Santa Barbara Basin (ODP Site 893A). The results were then compared to the existing sea surface temperature (SST) and pollen records from the same cores to understand terrestrial hydrology in relation to oceanographic processes. The Last Glacial was generally dry both in central and southern California, indicated by grassland expansion, confirming the previously suggested notion that the westerly storm track that supplies the majority of the precipitation in California may not have moved southward during the glacial period. Southern California was drier than central California during the Last Glacial Maximum (LGM). This drying trend may have been associated with the weakening of the California Current and northerly winds leading to the early increase in SST in southern California and decline in both offshore and coastal upwelling. The climate was wetter during the Holocene in both regions compared to the glacial period and forest coverage increased accordingly. We attribute this wetter condition to the precipitation contribution increase from the tropics. Overall, we found a clear synchronicity between the terrestrial and marine environment which showed that the terrestrial vegetation composition in California is greatly affected by not only the global climate states but also regional oceanographic and atmospheric conditions that regulate the timing and amount of precipitation over California.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.19 no.2
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• pp.147-154
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• 2014

Bacteria play an important role in biogeochemical cycles in marine environments and their functional attributes in ecosystems depend primarily on species composition. In this study, seasonal variation of bacterial diversity was investigated by pyrosequencing of 16S rDNA in surface sediment and overlying seawater collected in the south East Sea, planned for the site of $CO_2$ sequestration by the carbon capture and storage (CCS) project. Gammaproteobacteria was dominant in the sediment in most seasons, whereas Alphaproteobacteria was a most dominant group in the overlying water. Thus, the bacterial diversity greatly differ between sediment and seawater samples. On the genus level, bacterial diversity between two habitats was also different. However, the number of genera found over 5% were less than 10 in both habitats and the bacterial community was composed of a number of diverse minor or rare genera. Elevation of $CO_2$ concentration during a $CO_2$ storage process, could result in change of bacterial diversity. Thus, this study will be very useful to access the effect of $CO_2$ on bacterial diversity and to predict functional change of the ecosystem during the process of CCS project.

• Journal of the Korean earth science society
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• v.43 no.1
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• pp.91-109
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• 2022

The ocean is a significant sink for atmospheric anthropogenic CO₂, absorbing one-third of the total CO₂ emitted by human activities. In return, oceans have experienced significant declines in seawater pH and the aragonite saturation state also called ocean acidification. This study evaluates the distribution of aragonite saturation state, an indicator to assess the potential threat from ocean acidification, by combining newly obtained data from the west coast of South Korea with previous datasets covering the Yellow Sea, East Sea, northern South China Sea, and southeast coast of South Korea. In general, offshore waters absorb atmospheric CO₂; however, most of the collected water samples show aragonite oversaturation. On the southeast coast, the aragonite saturation state was significantly affected by river discharge and associated variables, such as freshwater input with nutrients, seasonal stratification, biological carbon fixation, and bacterial remineralization. In summer, hypoxia and mixing with relatively acidic freshwater made the Jinhae and Gwangyang Bays undersaturated with respect to aragonite, possibly threatening marine organisms with CaCO₃ shells. However, widespread aragonite undersaturation was not observed on the west coast, which receives considerable river water discharge. In addition, occasional upwelling events may have worsened the ocean acidification in the southwestern part of the East Sea. These results highlight the importance of investigating site-specific ocean acidification processes in coastal waters. Along with the above-mentioned seasonal factors, the dissolution of atmospheric CO₂ and the deposition of atmospheric acidic substances will continue to reduce the aragonite saturation state in Korean waters. To protect marine ecosystems and resources, an ocean acidification monitoring program should be established for Korean waters.

• Ocean and Polar Research
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• v.32 no.3
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• pp.309-319
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• 2010

To assess community structure and diversity of archaea, a clone sequencing analysis based on an archaeal 16S rRNA gene was conducted at three sediment depths of the continental slope and Ulleung Basin in the East Sea. A total of 311 and 342 clones were sequenced at the slope and basin sites, respectively. Marine Group I, which is known as the ammonia oxidizers, appeared to predominate in the surface sediment of both sites (97.3% at slope, 88.5% at basin). In the anoxic subsurface sediment of the slope and basin, the predominant archaeal group differed noticeably. Marine Benthic Group B dominated in the subsurface sediment of the slope. Marine Benthic Group D and Miscellaneous Crenarchaeotal Group were the second largest archaeal group at 8-9 cm and 18-19 cm depth, respectively. Marine Benthic Group C of Crenarchaeota occupied the highest proportion by accounting for more than 60% of total clones in the subsurface sediments of the basin site. While archaeal groups that use metal oxide as an electron acceptor were relatively more abundant at the basin sites with manganese (Mn) oxide-enriched surface sediment, archaeal groups related to the sulfur cycle were more abundant in the sulfidogenic sediments of the slope. Overall results indicate that archaeal communities in the Ulleung Basin show clear spatial variation with depth and sites according to geochemical properties the sediment. Archaeal communities also seem to play a significant role in the biogeochemical carbon (C), nitrogen (N), sulfur (S), and metal cycles at each site.