• Article

    Distribution Characteristics of Organic Carbon and Nutrient in Effluent of Land-based Aquaculture Farms around Wando in Korea

    하계 완도 주변 육상 양식장 배출수 중 유기탄소 및 영양염의 분포 특성

    GyuRi Kim, Yujeong Choi, Tae–Hoon Kim

    김규리, 최유정, 김태훈

    To evaluate the impact of effluents from land-based fish farms on the coastal ocean of Wando, Korea, we analyzed inorganic nutrients, particulate … + READ MORE
    To evaluate the impact of effluents from land-based fish farms on the coastal ocean of Wando, Korea, we analyzed inorganic nutrients, particulate organic carbon (POC), dissolved organic carbon (DOC), and colored dissolved organic matter (CDOM) in the effluent and influent of land-based fish farms during the summer (July) of 2021. The average concentrations of nutrients (Dissolved inorganic nitrogen, phosphorus, and silicate; DIN, DIP, and DSi, respectively) in the effluents of this study area were 17±3.7 μM, 1.4±0.7 μM, and 14±1.6 μM, respectively. The average concentrations of POC and DOC were 37±22 μM and 81±13 μM, respectively, with POC accounting for about 30% for total organic carbon in effluents. The Reduced Dissolved Inorganic Nitrogen/Total Dissolved Inorganic Nitrogen ratio (0.7), potential short-period index, indicates that the discharge of nutrients excreted by the fish and unconsumed feed into coastal water results in such nutrients being deposited and accumulated in the sediment. Subsequently, this continuous accumulation triggers the release of ammonium ions during organic matter decomposition, and the ammonium-enriched waters that encroach on fish farms as influent seem to be due to the diffusion of high concentrations of ammonium from bottom sediment. Furthermore, we used fluorescence indices to examine the characteristics of organic matter sources, obtaining mean values of 1.54±0.19, 1.06±0.06, and 1.56±0.06 for the humification index, biological index, and fluorescence index, respectively, in the effluent. These results indicate that the organic matters had an autochthonous origin that resulted from microbial decomposition, and such organic matters were rapidly generated and removed by biological activity, likely supplied from the sediment. Our results suggest that the effluent from land-based fish farms could be a potential source of deoxygenation occurrence in coastal areas. - COLLAPSE
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    30 September 2023

  • Article

    Response of Size-fractionated Phytoplankton to Humic Acids in the Seawater of Yeongsan River Estuary

    영산강 하구에서 부식산이 식물플랑크톤에 미치는 영향

    Sehee Kim, Yongsik Sin

    김세희, 신용식

    Humic substances are refractory organic compounds that are relatively low in biological activity but known to stimulate phytoplankton growth in estuarine and … + READ MORE
    Humic substances are refractory organic compounds that are relatively low in biological activity but known to stimulate phytoplankton growth in estuarine and marine environments. The effect of humic substances on phytoplankton growth was investigated in the seawater zone of the Yeongsan River estuary where an episodic anthropogenic freshwater is discharged, affecting its water properties directly. Water samples and data of water properties were collected at three stations (Sts. A–C) along the channel of the seawater zone in February, May, August and November, 2009. The collected water samples were incubated after humic acids (HA) were added in mesocosm experiments. Phytoplankton (chlorophyll-a) were fractionated into net- (> 20 µm) and nano-size (< 20 µm) to examine the response of phytoplankton according to size. Their response to HA treatment was assessed by repeated measures analysis of variance (RM- ANOVA). The experiments showed that phytoplankton biomass (chlorophyll-a) significantly increased after HA were added at the stations near the sea dike. Especially, nano-sized chlorophyll-a concentrations increased significantly throughout the seasons. This indicates that understanding the behavior of refractory organic matters such as humic substances is required to better manage altered estuarine ecosystems including the Yeongsan River estuary which are affected by episodic discharge of freshwater from sea dikes. - COLLAPSE
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    30 September 2023

  • Article

    Composition and Abundance of Meiofaunal biofouling on the Surface of Plastic Debris Washed Ashore

    해변 표착 플라스틱 쓰레기 서식 중형저서부착생물 조성과 서식밀도

    Eun-Ran Baek, Minju Kim, Hyeon Kim, Jung-Hoon Kang

    백은란, 김민주, 김현, 강정훈

    We investigated meiofaunal biofouling (40–1,000 μm) on stranded marine plastic debris (hereafter MPD) collected from 8 coastal areas highly affected by plastic … + READ MORE
    We investigated meiofaunal biofouling (40–1,000 μm) on stranded marine plastic debris (hereafter MPD) collected from 8 coastal areas highly affected by plastic pollution located in the southern part of Korea during June, 2021, in order to analyze the abundance and composition of MPD associated organisms. A total of eight shapes of MPD was collected and classified into four types of plastics (LDPE, PET, PP and EPS) based on Resin Identification Coding System. Meiofounal biofouling was identified into 35 taxa belonging to 11 phylum, 10 classes and 12 order, and were numerically dominated by harpacticoids (EPS: 21.6%, PP: 27.1%), nematodes (LDPE: 23.2%) and foraminiferans (PET: 29.6%). Surface area of MPD was negatively correlated with abundances of organisms on the plastic debris (r = -0.487, p< 0.05, n = 24), indicating that abundances (avg. 3,225 inds. 0.1 m-2) on the smallest area of PP debris (avg. 0.0208 m2) were higher than those (avg. 50 inds. 0.1 m-2) on the largest area of LDPE debris (avg. 0.4029 m-2). Whereas, there was no correlation between surface area of MPD and the number of taxa on the debris (r = 0.147, p = 0.49, n = 24). These results showed that higher abundances of meiofaunal biofouling were observed on the PP material debris than those on the other debris collected from eight hot spots of the southern coastal waters in Korea, associated with not only polymer type and surface area of the PP debris, but also possibly surface microstructure of the PP debris. - COLLAPSE
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    30 September 2023

  • Article

    Variation of Biogenic Opal Production on the Conrad Rise in the Indian Sector of the Southern Ocean since the Last Glacial Period

    남극해 인도양 해역에 위치한 콘래드 해령 지역의 마지막 빙하기 이후 생물기원 오팔 생산의 변화

    JuYeon Yang, Ikehara Minoru, Hyuk Choi, Boo-Keun Khim

    양주연, MinoruIkehara, 최혁, 김부근

    Biological pump processes generated by diatom production in the surface water of the Southern Ocean play an important role in exchanging CO … + READ MORE
    Biological pump processes generated by diatom production in the surface water of the Southern Ocean play an important role in exchanging CO2 gas between the atmosphere and ocean. In this study, the biogenic opal content of the sediments was measured to elucidate the variation in the primary production of diatoms in the surface water of the Southern Ocean since the last glacial period. A piston core (COR-1bPC) was collected from the Conrad Rise, which is located in the Indian sector of the Southern Ocean. The sediments were mainly composed of siliceous ooze, and sediment lightness increased and magnetic susceptibility decreased in an upward direction. The biogenic opal content was low (38.9%) during the last glacial period and high (73.4%) during the Holocene, showing a similar variation to that of Antarctic ice core ΔT and CO2 concentration. In addition, the variation of biogenic opal content in core COR-1bPC is consistent with previous results reported in the Antarctic Zone, south of the Antarctic Polar Front, in the Southern Ocean. The glacial-interglacial biogenic opal production was influenced by the extent of sea ice coverage and degree of water column stability. During the last glacial period, the diatom production was reduced due to the penetration of light being limited in the euphotic zone by the extended sea ice coverage caused by the lowered seawater temperature. In addition, the formation of a strong thermocline in more extensive areas of sea ice coverage led to stronger water column stability, resulting in reduced diatom production due to the reduction in the supply of nutrient-rich subsurface water caused by a decrease in upwelling intensity. Under such environmental circumstances, diatom productivity decreased in the Antarctic Zone during the last glacial period, but the biogenic opal content increased rapidly under warming conditions with the onset of deglaciation. - COLLAPSE
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    30 September 2023

  • Review

    Review of the Melting of West Antarctic Ice Shelves in the Amundsen Sea and Its Influence: Research Issues and Scientific Questions

    아문젠해 서남극 빙붕 용융과 영향에 대한 고찰: 연구동향 및 과학적 질문

    Seung-Tae Yoon

    윤승태

    The collapse of ice shelves is a process that can severely increase the rise of global sea-levels through the reduction of the … + READ MORE
    The collapse of ice shelves is a process that can severely increase the rise of global sea-levels through the reduction of the buttressing effect of ice shelves and the consequent acceleration of the ice flow of ice sheets. In recent years, the West Antarctic ice shelves in the Amundsen Sea, whose buttressing effect is essential for a great part of the West Antarctic ice sheet, have been experiencing the most rapid melting and thinning in the world. The melting of the West Antarctic ice shelves is caused primarily by heat transported by Circumpolar Deep Water (CDW). For this reason, it is important to investigate ice-ocean interactions that could influence the melting of ice shelves and evaluate the stability of West Antarctic ice shelves. A lot of researchers have been actively investigating the West Antarctic ice shelves in the Amundsen Sea. High-impact journals have recognized the importance of and published studies on ice-ocean interactions occurring near and under the ice shelves as well as the connections among ice shelves. However, in situ observations are limited due to extreme weather and sea-ice conditions near the ice shelves; therefore, many scientific questions remain unanswered. This study introduces the characteristics of the Amundsen Sea and investigate the past and latest research issues in this region. This study also gives suggestions regarding important scientific questions and directions for future research that should help early-career scientists take the lead in future research on the melting dynamics of the West Antarctic ice shelves in the Amundsen Sea. - COLLAPSE
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    30 September 2023

  • Note

    Current Status and Ecological, Policy Proposals on Barren Ground Management in Korea

    우리나라 갯녹음 관리 현황과 생태적‧정책적 제언

    Seongwook Park, Jooah Lee

    박성욱, 이주아

    The barren ground phenomenon in Korea began to occur and spread in the southern coast region and in Jeju Island in the … + READ MORE
    The barren ground phenomenon in Korea began to occur and spread in the southern coast region and in Jeju Island in the 1980s, and since the 1990s, the damage has become serious in the east coast region as well. Korea has enacted the fisheries resource management act to manage such barren ground through the installation of sea forests among projects for the creation of fishery resources. Until now, projects related to the identification of the cause of barren ground have focused on the density of crustose coralline algae, sea urchins and seaweed, so the original cause of barren ground has not yet been identified. In order to manage barren ground, it is necessary to identify the cause of barren ground. To identify these causes, it is necessary to comprehensively consider i) studies on spatial characteristics such as rock mass distribution, slope and water depth, ii) studies on ecological and oceanographic characteristics such as water temperature, salinity, El Niño, and typhoons etc, iii) studies on organisms such as crustose coralline algae, macroalgae, and sea urchins, and iv) studies on coastal use such as living and industrial sewage inflow. Next, as with regard to legislative policy proposals , it is necessary to prepare self-management measures by the government, local governments, and fishermen as well as address management problems related to the use of sea forests by fishermen after their creation . In addition, when creating a sea forest, a management model for each resource management plan is required, and evaluation indicators and indexes that can diagnose the cause of barren ground and guidelines for barren ground measures should be developed. - COLLAPSE
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    30 September 2023
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