Guebuem Kim

• Ph.D.
• Professor at Seoul National University

The swimming crab, Portunus trituberculatus, supports the world’s largest crab fishery. Hard-shell crabs have fully developed exoskeletons and are rich in meat, while soft-shell crabs, which have recently molted, contain less meat. To determine their nutritional status and feeding behavior, we measured amino acids (AAs), organic carbon (OC), δ¹³C,...

Rivers transport ~200 Tg of particulate organic carbon (POC) to the global ocean annually, of which 30% is known to be buried in continental‐shelf sediments. The fate of the remaining “missing” terrestrial POC (POCterr) remains uncertain, with proposed explanations including rapid remineralization or transport to the remote deep ocean. Here, based...

The transport of particulate organic carbon (POC) from land to deep‐sea sediments is a critical component of the global carbon cycle. However, the transport processes of terrestrial POC across continental shelves remain poorly understood due to the complexity of these systems. In this study, we investigated the vertical fluxes and fates of terrestr...

Fluorescent dissolved organic matter (FDOM) provides crucial information regarding the sources and characteristics of DOM in oceans. However, the FDOM measurements vary depending on filter blanks, pore sizes, and sample storage. To develop more reliable methods for FDOM measurements, in this study, we examined the uncertainties associated with diff...

We measured ¹³⁷ Cs in seawater, particulate matter, and sediment cores from two coastal bays (Masan Bay and Suyeong Bay) in Korea in August 2016 and July 2017 to examine its deposition in water and remobilization in the sediments. The ¹³⁷ Cs activities in the bay seawaters were similar to those in the remote ocean seawaters, suggesting that there a...

The northern East China Sea is one of the Large Marine Ecosystems, which experiences the fastest ocean warming across the globe. With the anticipation of stimulated Tsushima Warm Current (TWC) transport and rapid ocean warming, the importance of picoplankton will increase in this ecosystem. Thus, the spatiotemporal distribution of picoplankton was...

Terrestrial groundwater travels through subterranean estuaries before reaching the sea. Groundwater‐derived nutrients drive coastal water quality, primary production, and eutrophication. We determined how dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved organic nitrogen (DON) are transformed within subterranea...

Measurements of dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP) concentrations are used to characterize the dissolved organic matter (DOM) pool and are important components of biogeochemical cycling in the coastal ocean. Here, we present the first edition of a global database (CoastDOM v1; available at 10.1594/PANGAEA.964012, L...

Actinium‐227 (²²⁷Ac) has been used as a powerful tracer of diapycnal mixing in the ocean, assuming that it is conservative and originates mainly from deep‐sea sediments. However, here we show an unexpectedly large source (continental margin) and sink (scavenging) of ²²⁷Ac in the ocean, based on high‐resolution ²²⁷Ac distributions obtained for the f...

The East Sea (also known as the Japan Sea) is connected to the Northwest Pacific via shallow straits and has independent deep water circulation, as a model miniature ocean. The radiocarbon age of dissolved organic carbon (DOC) in the East Sea ranged from 2,000 to 3,700 years, exceeding the water turnover time (∼100 years). The oldest DOC was found...

We measured dissolved organic carbon (DOC) and total dissolved amino acid (TDAA) in seawater and sediment porewater of the Ulleung Basin in the East/Japan Sea. The DOC and TDAA concentrations were 1.1‐ and 1.4‐fold higher in the euphotic zone, and 11‐ and 43‐fold higher in sediment porewater, respectively, than those in the deep ocean. Consequently...

The measurements of dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP) are used to characterize the dissolved organic matter (DOM) pool and are important components of biogeochemical cycling in the coastal ocean. Here, we present the first edition of a global database (CoastDOM v1; available at https://figshare.com/s/512289eb43c4f...

Iron (Fe) is an essential micronutrient for phytoplankton growth, and its availability limits primary production in half of the global ocean. Traditionally, atmospheric input of natural mineral dust has been considered as a main source of Fe in the surface ocean. However, here we show that about 45% of the water-soluble Fe in aerosols collected ove...

Despite the increasing numbers of red tide events in the pristine subtropical ocean, a paucity of previous observations has limited understanding of harmful algae in the seas around the Korean Peninsula. Therefore, using six years (2012–2017) of Geostationary Ocean Color Imager (GOCI) satellite data, we characterized the red tides around Jeju Islan...

We examined the changes in the concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) in the surface waters of the Yellow Sea (YS), the southern sea (SS) of Korea, and the East/Japan Sea (ES) from 1995 to 2021. These marginal seas neighboring the Korean Peninsula maintained nutrient concentrations approximately an order of magnit...

The concentrations of ²²²Rn and dissolved inorganic nutrients in river water at a fixed station of the Nakdong River estuary which has an artificial barrage were continuously measured from October 2014 to May 2015. Monthly benthic ²²²Rn flux from the river bottom was estimated using a simple mass balance model, taking into account ²²²Rn sources and...

Dissolved organic carbon (DOC) and the optical properties of dissolved organic matter (chromophoric- and fluorescent dissolved organic matter; CDOM and FDOM) were measured to determine the distributions and drivers of DOM in the northwestern Pacific marginal seas, including the East China Sea, the Yellow Sea, and the East/Japan Sea, in August 2020....

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on March 11, 2011 resulted in the release of immense amounts of radioactive materials into the ocean. However, the dispersion of radioactive materials in the subsurface has not yet been clarified due to the spatiotemporal limitation of observations. Thus, herein, a tracer experiment was imp...

In this study, we investigated the influence of fish-farm activities on the inventory of trace elements (Mn, Fe, Co, Ni, and Cu) in the coastal waters off the fish-farm plants on Jeju Island, Korea. NH4+ and rare earth elements (REEs) were used as tracers to examine the production and removal processes. Relatively higher concentrations of trace ele...

We investigated the effects of eddies and typhoons on the biogeochemistry of the tropical northwest Pacific by examining the distribution of nutrients, dissolved oxygen (DO), chlorophyll-a (Chl-a), gross primary production (GPP), dissolved organic carbon (DOC), and fluorescent dissolved organic matter (FDOM). Water samples were collected from antic...

Vertical profiles of ²²⁸Ra (half-life: 5.75 years) in the ocean provide valuable information on water mixing and ages of the upper ocean. However, its application is hampered by extremely low levels of ²²⁸Ra in the deep ocean. In this study, we measured high-resolution ²²⁸Ra/²²⁶Ra ratio profiles (>21 depths) in the East Sea (Japan Sea) by mooring M...

We examined particulate organic carbon (POC) export using ²³⁸U–²³⁴Th disequilibrium in the tropical northwest Pacific Ocean, where numerous eddies are present. We obtained data from an anticyclonic eddy in 2019 and from both anticyclonic and cyclonic eddies in 2020. In 2019, excess ²³⁴Th and higher POC concentrations were observed in the upper 100...

We measured the concentrations of dissolved inorganic and organic nutrients, dissolved organic carbon (DOC), total hydrolyzable amino acids (THAA), fluorescent dissolved organic matter (FDOM), phytoplankton pigments, and δ13C-DOC during the summer of 2019 in the harmful dinoflagellate bloom regions of the southern coast of Korea. In the harmful din...

The concentrations of nutrients and dissolved organic matter (DOM) in the coastal waters off Jeju Island, Korea, are known to be influenced mainly by submarine groundwater discharge (SGD) and fish-farm effluents, in addition to the background open-ocean seawater from the Tsushima Current. However, the differentiation of the effect of fish-farm effl...

The East Sea (also known as the Japan Sea; hereafter, EJS) is a semi-enclosed marginal sea surrounded by the Korean Peninsula, Russia, and the Japanese Islands. The EJS is connected to the Pacific through shallow straits. Thus, the EJS has its own thermohaline circulation and the characteristic biogeochemistry. The deep overturning circulation play...

We investigated the behaviors of dissolved trace elements (Mn, Fe, Ni, Cu, Zn, and Cd) associated with humic dissolved organic matter (DOMH) of varying origins in the surface waters of two Korean coastal regions (Jinhae Bay [JH] and offshore Tongyeong [TY]). Both regions displayed intensive scavenging and settling of the particle-reactive Ce and ²³...

The surface nutrient concentrations of the Northwest Pacific Ocean have shown distinct changes over the past four decades, which have been variably attributed to changes in anthropogenic nitrogen inputs or stratification. Here, we present a new data compilation that demonstrates a long‐term decline in the surface nutrient concentrations caused by a...

The effects of benthic dissolved organic carbon (DOC) flux on the dynamics of DOC in the deep continental margins (200 – 2000 m depth) is poorly understood. We investigated heterotrophic prokaryotes (hereafter bacteria) production (BP) and the bio-reactive properties of sediment-derived dissolved organic matter (SDOM) to elucidate microbially media...

To identify the sources of organic matter, we examined nitrogen isotopes of the amino acids of sinking particles collected from July 2017 to March 2018 at 1000 and 2250 m in the Ulleung Basin, the southwestern part of the East Sea (Japan Sea). Compared to the 1000 m samples, sinking particles at 2250 m were found to contain more resuspended sedimen...

The cycling of particulate organic carbon (POC) in continental shelf regions of the Yellow Sea (YS) and the East China Sea (ECS) was investigated by analyzing the concentrations and carbon isotope signatures (δ¹³C, Δ¹⁴C) of POC, together with the particulate aluminum (Al) concentration and ²³⁴Th activity over the period 10–20 August 2020. POC conce...

Fluxes of dissolved organic carbon (DOC) from continental shelves to the ocean may play a critical role in marine carbon cycling and budget. However, these fluxes have been poorly constrained because complicated biogeochemical reactions of riverine, atmospheric, and marine organic carbon occur in continental shelf-waters. We used multiple tracers o...

The distributions of trace elements (Fe, Mn, Co, Cu, Cd, and Ni) were measured, for the first time, in the entire East Sea (22 stations, n = 276, 0–3400 m), which is located in the region directly affected by East Asian monsoon and the upstream of Tsushima Current. In general, the distribution patterns of these trace elements were similar to those...

In order to determine the atmospheric input of ²¹⁰Pb and seawater-dissolvable Pb in the East Sea (Japan Sea), we measured the concentrations of total ²¹⁰Pb and dissolved Pb (<0.2 μm) in seawater and ²¹⁰Pb and ²²⁶Ra in sinking particles. The East Sea is deep (∼3700 m) and enclosed by surrounding continents except for the shallow sills (<150 m). Sinc...

The East China Sea (ECS) and Yellow Sea (YS) are East Asian marginal seas and mainly cover shallow continental shelves with depths of <200 m. These seas have high biological productivities with large spatial and temporal variabilities. Nevertheless, there are a limited number of studies on the biological pump in the ECS and YS. We observed net comm...

Thorium-234 (234Th; t1/2 = 24.1 days) has been widely used as a tracer of particle settling and organic carbon export in the ocean. However, the use of 234Th in the ocean has been hampered by labor-intensive procedures, low throughputs, and large uncertainties related to source impurities. Here, we demonstrate a more efficient technique developed t...

The sulphate ion (SO 4 ²⁻ ) is one of major species in freshwater as well as seawater, originating from various natural and anthropogenic processes (Krouse & Mayer 2000). Compared to the Northern Hemisphere, where human activities affect the sulphate concentration and isotopic signatures, the contribution of anthropogenic sulphate is likely to be n...

We measured the total, truly dissolved (<10 kDa), colloidal (10 kDa–0.2 μm), and particulate phases (>0.2 μm) of ²¹⁰Pb and ²¹⁰Po in the East China Sea (ECS) shelf water and the East Sea (Japan Sea). In order to examine the behaviors of ²¹⁰Pb and ²¹⁰Po in different marine environments, we compiled our results with previously reported data in the sam...

The transport of terrestrial sources of trace elements to the ocean has proven to be crucial in constraining not only their own biogeochemical behaviors but also regulating global carbon cycling and ecosystem changes. Most terrestrial dissolved trace elements are known to be largely scavenged in the estuarine mixing zone or coastal waters before re...

The transport of carbon from land to ocean, via rivers, groundwater, and aerosols, is an important component of the global carbon cycle that must be known to accurately assess anthropogenic CO2 storage on land and in the ocean. Current global carbon cycle budgets have adopted terrestrial carbon inputs to the ocean ranging from 0.5 GtC/yr to 0.9 GtC...

We measured the north–south transactional distributions of nutrients, dissolved organic carbon (DOC), and fluorescent dissolved organic matter (FDOM) in the East Sea (Japan Sea) in November 2019. The humic-like (C peak and M peak) and protein-like (T peak) components were identified using the parallel factor analysis model. The concentrations of C...

In order to determine the origins of dissolved organic matter (DOM) occurring in the seawater of Sihwa Lake, we measured the stable carbon isotope ratios of dissolved organic carbon (DOC-δ13C) and the optical properties (absorbance and fluorescence) of DOM in two different seasons (March 2017 and September 2018). Sihwa Lake is enclosed by a dike al...

Radon‐in‐air monitor (RAD7, Durridge Co.) has been widely used to measure 222Rn in water samples. RAD7 measures 222Rn via 218Po+ (t1/2 = 3.1 min), which is electrically attracted to a silicon alpha detector. In this study, a new method was developed for measuring 222Rn in water samples by modifying a commercially available pulsed ionization chamber...

The concentrations of dissolved rare earth elements (REEs) and trace elements (Al, V, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, and Pb) were measured along the Nakdong River Estuary. In general, REE concentrations presented negative correlations with salinity, except for the sampling sites close to the wastewater treatment plant (WWTP), where the concentrati...

We measured dissolved organic carbon (DOC), δ¹³C-DOC, fluorescent dissolved organic matter (FDOM), dissolved inorganic and organic nitrogen (DIN; DON), dissolved inorganic phosphate (DIP), and radium isotopes (²²³Ra, ²²⁴Ra, and ²²⁶Ra) in three different bays: Gwangyang Bay (GB), Suyoung Bay (SB), and Ulsan Bay (UB), Korea. The water residence times...

We measured the concentrations of nutrients, fluorescent dissolved organic matter (FDOM), and photosynthetic pigments in seawater during the springs of 2018 and 2019 in Jinhae Bay, Korea. The samplings were carried out during the severe and weak outbreaks of paralytic shellfish poisoning (PSP) in April 2018 and March 2019, respectively. The additio...

In order to determine the origins of dissolved organic matter (DOM) occurring in coastal seawater of the Sihwa Lake, South Korea, which is semi-enclosed by a dyke, we measured the stable carbon isotopic ratio of dissolved organic carbon (DOC-δ13C) and optical properties (absorbance and fluorescence) of the DOM in two different seasons (March 2017 a...

The distributions of rare earth elements (REEs) were measured at 14 stations from 0 to 3365 m (n = 176) in the entire East Sea for the first time. The East Sea has its own deep-convection system, which operates on a time scale that is approximately one tenth that of the global ocean; it is also a downwind region of Asian dust. The vertical distribu...

Atmospheric brown carbon (BrC) plays significant roles in the light absorption and photochemistry of the atmosphere. Although the sources and occurrences of BrC have been studied extensively, its removal processes and optical characteristics in the atmosphere have been poorly understood. In this study, we examined the seasonal changes in sources an...

The removal mechanism of refractory deep-ocean dissolved organic carbon (deep-DOC) is poorly understood. The Amundsen Sea Polynya (ASP) serves as a natural test basin for assessing the fate of deep-DOC when it is supplied with a large amount of fresh-DOC and exposed to strong solar radiation during the polynya opening in austral summer. We measured...

The sources of dissolved organic matter (DOM) in coastal waters are diverse, and they play different roles in the biogeochemistry and ecosystems of the ocean. In this study, we measured dissolved organic carbon (DOC) and nitrogen (DON), the stable carbon isotopic composition of dissolved organic carbon (δ13C-DOC), and fluorescent dissolved organic...

We measured dissolved rare earth elements (REEs) in the water samples from Shihwa Lake (SL), which was assumed to be highly polluted, as well as in the downstream portion of the Han River (HR), which runs through, Seoul, Korea. Among the investigated REEs, only gadolinium (Gd) was found to be significantly enhanced after REE concentrations were sha...

The spatio-temporal variability of the chlorophyll-a (chl-a) concentration in the East Sea (Japan Sea) (EJS) was investigated using Moderate Resolution Imaging Spectroradiometer (MODIS) data over 13 years from 2003 to 2015 to understand the impact of physical environmental changes on low-trophic level marine ecosystems. The chl-a images were compos...

Plain Language Summary Changes in the nutrients and biogeochemical cycles in the surface waters of the northwest Pacific Ocean have been mainly attributed to the atmospheric inputs of anthropogenic nutrients. However, we hypothesized that continental shelf waters, which receive large inputs of nutrients from rivers, groundwater, and the atmosphere,...

It is a well held concept that the magnitude of red-tide occurrence is dependent on the amount of nutrient supply if the conditions are same for temperature, salinity, light, interspecific competition, etc. However, nutrient sources fueling dinoflagellate red-tides are difficult to identify since red tides usually occur under very low inorganic-nut...

Abstract. Atmospheric brown carbon (BrC) plays significant roles in the light absorption and photochemistry of the atmosphere. Although the occurrence and sources of BrC have been studied extensively, its removal processes and optical characteristics in the atmosphere have been poorly understood. In this study, we examined the seasonal changes in s...

The number of studies concerning Submarine Groundwater Discharge (SGD) grew quickly as we entered the twenty-first century. Many hydrological and oceanographic processes that drive and influence SGD were identified and characterized during this period. These processes included tidal effects on SGD, water and solute fluxes, biogeochemical transforma...

The sources of dissolved organic matter (DOM) in coastal waters are diverse, and they play different roles in biogeochemistry and ecosystems. In this study, we measured dissolved organic carbon (DOC) and nitrogen (DON), δ¹³C-DOC, and fluorescent dissolved organic matter (FDOM) in coastal bay waters surrounded by heavily industrialized cities (Masan...

Recent studies have shown that the global input of dissolved inorganic phosphorus (P) to the oceans through submarine groundwater discharge (SGD) is twice as high as the input through rivers. This estimation is based on a relatively high level of particle-reactive P (∼2.0 μM) observed globally in coastal saline aquifers, although the mechanism for...

Several studies have documented the characteristics of seasonal, decadal, and spatial variations of tritium in different regions including North America, Australia, and Europe. However, long-term data such as these studies were not yet reported for Northeast Asia. In this study, we document the extensive spatial-temporal monitoring data of tritium...

To determine the seasonal variations in the removal efficiency of fine aerosols (PM2.5) in the Northeast Asia, we analyzed ⁷ Be data collected for the surface air and precipitation over 20 years in Korea. The ⁷ Be activity concentrations in the surface air were relatively higher in spring owing to tropopause folding but lower in summer owing to eff...

The main sources of nutrients fueling coastal green tides off a volcanic island surrounded by an oligotrophic ocean are obscure, although they result in many societal and ecosystem problems. In this study, we attempted to trace the source inputs of nutrients in coastal waters off a volcanic island, Jeju, Korea, where the formation of green tides is...

Submarine groundwater discharge (SGD) plays an important role in coastal biogeochemical processes and hydrological cycles, particularly off volcanic islands in oligotrophic oceans. However, the spatial and temporal variations of SGD are still poorly understood owing to difficulty in taking rapid SGD measurements over a large scale. In this study, w...

In order to determine the origins of dissolved inorganic nutrients and dissolved organic matter in coastal waters off Jeju Island, Korea, we measured the concentrations of ²²²Rn, nutrients, fluorescent dissolved organic matter (FDOM), and dissolved organic carbon in coastal waters during September 2016 and October 2017. The lower salinity waters oc...

The Changjiang River is one of the main nutrient sources in the northwestern Pacific marginal seas. However, most of the previous studies have neglected the long-range transport (>200 km) of riverine nutrients since they are rapidly consumed. In this study, we examined the long-range transport (200-800 km) of nutrients in the surface layer during t...

The activities of tritium in water-vapor (n = 649) and precipitation (n = 2404) samples were measured from 1998 to 2015 around the Wolsong nuclear power plant (NPP) site where four pressurized heavy water reactors and two pressurized water reactors operated. The activity concentrations of tritium in the water-vapor and precipitation samples were in...

Fluorescent dissolved organic matter (FDOM) is important for marine organisms and the global carbon cycle contributing to the optical properties of surface seawater and organic carbon budgets. Rivers are known to be the main source of FDOM in coastal oceans and marginal seas. In this study, however, we show that the contribution of FDOM produced fr...

We monitored seasonal variations in dissolved organic carbon (DOC), the stable carbon isotope of DOC (δ13C-DOC), and fluorescent dissolved organic matter (FDOM) in water samples from a fixed station in the Nakdong River Estuary, Korea. Sampling was performed every hour during spring tide once a month from October 2014 to August 2015. The concentrat...

Riverine and atmospheric inputs are often considered as the main terrestrial sources of dissolved inorganic nitrogen (DIN), phosphorus (DIP), and silicon (DSi) in the ocean. However, the fluxes of nutrients via submarine groundwater discharge (SGD) often exceed riverine inputs in different local and regional scale settings. In this study, we provid...

We investigated phytoplankton pigments, dissolved organic carbon (DOC), and fluorescent dissolved organic matter (FDOM) during the summers of 2013 and 2016 in the coastal area of Tongyeong, Korea, where Cochlodinium polykrikoides blooms often occur. The density of red tides was evaluated using a dinoflagellate pigment, peridinin. The concentrations...

The abundance of fluorescent dissolved organic matter (FDOM) in the surface ocean plays a critical role in the growth of marine microorganisms and corals by affecting the optical properties (i.e., the penetration of UV radiation) of seawater. In general, it is known that rivers are the main source of FDOM to surface ocean waters. Here, however, we...

Brown carbon (BrC) plays a significant role in the Earth’s radiative balance, yet its sources and chemical composition remain poorly understood. In this work, we investigated BrC in the atmospheric environment of Seoul by characterizing dissolved organic matter in precipitation using excitation-emission matrix (EEM) fluorescence spectroscopy couple...

We monitored seasonal variations of dissolved organic carbon (DOC), stable carbon isotope of DOC (δ¹³C-DOC), and fluorescent DOM (FDOM) in water samples from a fixed station in the Nakdong-River Estuary, Korea. Sampling was performed every hour during spring tide once a month from September 2014 to August 2015. The concentrations of DOC and FDOM sh...