This study investigated the distribution and growth performance of Bolboschoenus planiculmis under varying estuarine environmental conditions. We aimed to determine the optimal planting methods and environmental conditions with respect to salinity, soil texture, and tidal regimes on its growth performance. Our findings revealed a significant reduction in B. planiculmis coverage, shrinking to 955,393 m2 in 2024, representing only 38.59% of that compared to 2004. The plant’s survival rate exhibited a clear salinity gradient: 0 ppt (89±8.01%)>5 ppt (64±4.56%)>15 ppt (37±4.25%)>30 ppt (0±0.00%). Planting density significantly influenced growth, with 24 tubers m-2 yielding the highest number of plants per tuber (14.67±0.33). A planting depth of 5 cm proved optimal for tuber germination and growth. Soil texture analysis demonstrated that a lower sand content promoted growth, with the highest density observed in soil containing 10% sand (435±6.96 plants m-2). Tidal influence also played an important role, with areas experiencing regular tidal fluctuations fostering the most successful growth. Planting tubers or young plants with attached tubers in these tidal zones led to the highest survival rates and biomass.

Ecological indicators are tools used to evaluate the state of specific environments by monitoring the ecological characteristics and changes of organisms, and they are widely utilized in environmental monitoring and management. Such indicators should be sensitive to environmental changes, maintain long-term stability, and be easy to investigate and analyze. This study aimed to evaluate whether the spraint density of the Eurasian otter (Lutra lutra) can monitor the state and changes in river ecosystems. Using spraint density data over nine years (2014~2024), we analyzed temporal and spatial changes in otter distribution. Generalized Additive Models were applied to assess annual variability, and spatial clustering and distribution changes were examined using Hotspot Analysis and Geo-SOM (Geo-Self-Organizing Map). The results indicated stable spraint density trends in most sub-watersheds, with higher variability in developed areas. This study highlights the potential of spraint density as a cost-effective and simple ecoological indicator for long-term river ecosystem monitoring.

Fishways, particularly installed at the estuary, have a purpose to encourage fluent migration for migratory fishes, as well as amphidromous and even freshwater species. Not choosing the laborious traditional method of using traps, we assessed the efficiency of the two fishways installed at the west and east barrage of the Nakdong River estuarine barrage respectively, by analyzing the videos recorded through automatic monitoring system. We randomly selected 30 videos monthly at each fishways and identified what kind of fishes were using the fishways and categorised their behaviour such as size, time and whether they passed the monitoring system or not. As a result, a total 8 families 14 species were recorded by monitoring system, with the most dominance of Erythroculter erythropterus (Relative Abundance: 59.5%), followed by Micropterus salmoides (R.A: 19.9%) and Mugil cephalus (R.A: 9.9%). The monitoring system can capture passing fishes during night but the number of appearances of fish species at each hour of a day indicated significant diurnal activities (p<0.05). When fishes pass the monitoring system, approximately 70% of them passed through the monitoring device, while 17% of them showed fallback movement. Our finding indicates that species-specific characteristics of each fish are well represented through video monitoring method. In order to maximise advantages of using video monitoring, it is necessary to consider the installation point properly so that the monitoring system does not interfere with the movement of fish. Also, the utilisation of AI technology in the future is also necessary.

This study investigated fish communities at a total of 11 sites across four rivers in the region in 2005 and 2015. Sampling was conducted twice at each site using cast nets (10×10 mm mesh size) and scoop nets (4×4 mm and 5×5 mm mesh sizes). Basic water quality measurements and river naturalness assessments were also performed. Based on fish community survey results, a Self-Organizing Map (SOM) analysis was employed to evaluate the impact of urbanization on fish communities in the study area. The results revealed a tendency for decreased electrical conductivity in water quality and improved scores in river naturalness assessments. Compared to the environmental conditions in 2005, the overall naturalness of the study area appeared to have increased by 2015. A total of 721 individual fish representing 32 species from 12 families were collected. The dominant species was largemouth bass (Micropterus salmoides, 141 individuals, 19.6%), and the subdominant species was dark chub (Zacco temmincki, 132 individuals, 18.3%). The SOM analysis demonstrated a clear distinction in fish community distribution patterns between the survey years. Brackish water species such as Plecoglossus altivelis, Lateolabrax japonicus, and Mugil cephalus, along with introduced species like Erythroculter erythropterus, exhibited higher frequencies in 2015. Although the occurrence of exotic species tended to decrease compared to 2005, the presence of bluegill (Lepomis macrochirus) showed an increase in 2015. These findings suggest an increase in species favoring deeper waters and lacustrine environments, with notable growth in populations of introduced and exotic species.

This study investigated the annual change and distribution of flora, including endangered species, Korean Red List species, and invasive plants, in the Nakdong River Estuary Ecological Park over a 10-year period (2013~2023). The park was established in 2009 as part of the Four Major Rivers Restoration Project. The investigation identified a total of 704 taxa, comprising 137 families, 401 genera, 631 species, 18 subspecies, 38 varieties, 11 forms, and 6 hybrids. Eulsukdo Ecological Park exhibited the highest plant diversity with 531 taxa, followed by Hwamyeong (404 taxa), Samnak (387 taxa), Daejeo (369 taxa), and Maekdo (356 taxa). The endangered wildlife survey identified three endangered plant species (Class II): Euryale ferox, Brasenia schreberi, and Saururus chinensis. Following the endangered species restoration project, E. ferox has been consistently observed both within the restoration area and the riparian of main channel. The Urbanization Index (UI) was highest in Eulsukdo Ecological Park (24.1%), followed by Hwamyeong (20.0%), Samnak (18.1%), Maekdo (17.8%), and Daejeo Ecological Parks (16.7%). Twelve invasive plants were identified: Sicyos angulatus, Lactuca scariola, Ambrosia trifida, Ambrosia artemisiifolia, Solanum carolinense, Aster pilosus, Hypochaeris radicata, Rumex acetosella, S. altissima, Paspalum disticum, Paspalum distichum var. indutum, and Humulus japonicus. Notably, S. altissima showed a significant decrease in its total distribution area, shrinking from 741,092 m2 in 2021 to 241,396 m2 in 2024. Continuous monitoring and management are necessary to prevent invasive plants, including ecosystem-disturbing species, from forming large colonies and hindering the growth of native plants.

This study employed text mining techniques to analyze the major topics and research trends in plant ecological studies conducted in the Nakdong River basin. A total of 131 research articles published between 1977 and 2023 were collected from domestic and international academic databases. Our analysis revealed that the primary research themes include: wetland plant management and restoration, regional flora investigation, the relationship between aquatic plant communities and water quality, wetland plant community structure and distribution, riparian vegetation, and Phragmites australis (common reed). The majority of these studies were based on short-term field surveys (less than one year in duration; 79.7%), with a focus on regional flora investigation (30.5%), vegetation mapping (21.4%), and plant growth characteristics (17.6%). To ensure the longterm sustainability of the Nakdong River ecosystem, we suggest prioritizing long-term ecological research (LTER) initiatives and incorporating diverse research approaches, such as mesocosm experiments that manipulate key environmental factors. This comprehensive approach to plant ecological research will be crucial for evaluating the stability and resilience of the Nakdong River ecosystem and will ultimately contribute to the development of robust, scientifically informed decision-making processes and management strategies.

This study investigated the long-term dynamics of phytoplankton communities, key environmental factors, and indicator species in Mulgeum, a major downstream site of the Nakdong River, from 1993 to 2020. Monthly phytoplankton densities ranged from 189 to 52,757,982 cells mL-1, with diatoms dominating yearround (29.1~93.4%). Notably, cyanobacteria exhibited the highest growth rates, which could exacerbate algal blooms under long-term climate change. Using generalized additive models, five environmental factorsdissolved oxygen, transparency, total phosphorus, phosphate, and discharge-were found to significantly influence monthly variations in most taxa. Cyanobacteria were most sensitive to environmental changes, while chrysophytes showed minimal dependence on specific factors. Principal component analysis grouped environmental conditions into five clusters, with each cluster characterized by distinct conditions and indicator species. A total of 122 species were identified as indicators, with green algae contributing the most. Cluster 1, characterized by high transparency and low phosphorus, was dominated by Stephanodiscus hantzschii, a common species in eutrophic waters. Cluster 4, associated with high phosphorus, highlighted Cyclotella ocellata as a key indicator, emphasizing phosphorus as a crucial determinant for diatom structure. These findings underscore the critical role of hydrological and nutrient factors in shaping phytoplankton communities and provide insights into ecological responses to environmental changes in the Nakdong River system. The results can inform sustainable management strategies to mitigate eutrophication.

This study used text mining to analyze public interest and research trends related to the Nakdong River. We examined news articles (1990~2024) and academic publications (1960~2024) to understand the evolving relationship between societal concerns and scientific research. Main findings reveal growing public interest towards the Nakdong River, with initial focus on pollution related to the industrial development shifting to large-scale river modification projects and water quality issues. This increased awareness mirrored trends in research, where early emphasis on classic ecology and water quality expanded to include sociocultural, educational aspects and advanced methodologies. The study highlights a dynamic interplay between public discourse and scientific inquiry, with research priorities aligning with societal concerns like water pollution, algal blooms, and biodiversity loss, underscoring the need for integrated, multidisciplinary research that addresses emerging environmental challenges and promotes sustainable management of the Nakdong River ecosystem under climate change and other societal shifts.

In stable continental regions, selecting appropriate ground motions for seismic design and dynamic response analysis presents significant challenges. This study evaluates the liquefaction potential of the Nakdonggang delta region, South Korea, by generating synthetic ground motion scenarios and applying a scenario-based liquefaction assessment approach. We utilized a hybrid broadband ground motion simulation method proposed by Graves and Pitarka (2010, 2015) to create bedrock ground motions for three hypothetical earthquakes (Mw 6.2 and 6.0) occurring along the Dongrae and Miryang faults. The generated synthetic ground motions were used as input for onedimensional nonlinear site response analyses, incorporating shear wave velocity profiles derived from surface wave inversion. The simulated ground motions demonstrated higher responses at short periods and relatively weaker responses at long periods compared to the Korean design spectra. This amplification of long-period components was attributed to the dynamic response of deep sedimentary layers, while high-frequency components were generally deamplified due to damping effects in shallow silty layers. Liquefaction susceptibility was assessed using surface ground motions derived from the site response analyses, following the SPT-based simplified method proposed by Idriss and Boulanger (2008). Results indicated high liquefaction potential across most sites for the Dongrae earthquake scenario, while liquefaction was unlikely for all sites under the Miryang-1 scenario. For the Miryang-2 scenario, liquefaction was predicted at some sites. Overall, liquefaction is expected at PGA values of approximately 0.13 g or higher, with sites exhibiting lower shear wave velocities being more vulnerable to liquefaction

This study summarizes the history of zooplankton research in the Nakdong River basin, Korea, and discusses its main characteristics by topic. A review of major academic search portals revealed 56 studies on zooplankton in the Nakdong River basin, which account for 27.6% of the 203 domestic freshwater zooplankton studies. With the exception of one study conducted before the construction of the estuary barrage, all other research was carried out after the barrage was built. Of the studies, 27 were related to lotic ecosystems, and 29 focused on lentic ecosystems, with research predominantly conducted south of Daegu Metropolitan City. Short-term studies of less than a year were common for lentic ecosystems, while longterm studies were mainly focused on lotic ecosystems. The key research sites were the Mulgeum water intake in the lower Nakdong River and Upo Wetland, the largest inland wetland in Korea, where research periods and zooplankton sampling were most diverse. Research on predation and prey interactions has been ongoing, as zooplankton plays an intermediary role by feeding on phytoplankton and serving as food for juvenile fish. Recent studies show that, since around 2015, the water quality and zooplankton community dynamics around Mulgeum have changed, requiring continuous monitoring. To address this, predictive model analysis, isotope analysis, and indicator analysis, widely used in Nakdong River research, could help develop health indicators for aquatic ecosystems using zooplankton.

강으로부터 해양으로 유입되는 퇴적물은 유역분지의 지질, 지리, 지형, 기후 등의 영향을 반영하며, 육상 유역분 지에서 퇴적물 생성 과정에서 수반되는 화학적 풍화는 대기 중 이산화탄소 농도를 조절하는 데에 중요한 역할을 하는 것으로 알려져 있다. 본 연구에서는 한반도 남해안 낙동강 하구 인근 해저 표층 퇴적물의 지화학 조성을 이용하여 화 학적 풍화의 강도와 퇴적물의 기원지에 분포하는 암석의 조성을 추정하였다. 연구 시료의 화학적 풍화 강도는 중간에 낮은 정도(평균 Chemical Index of Alteration=68)이며 A-CN-K 도표에서 추정한 풍화의 추세는 퇴적물의 기원지 성분 이 평균적인 상부 대륙지각과 매우 유사한 것으로 보인다. 이는 낙동강 유역분지에 분포하는 중생대 화강암류와 경상누 층군 퇴적암이 혼합된 성분을 반영하는 것으로 판단되기 때문에 연구 대상인 퇴적물이 낙동강 하구로부터 유입되는 퇴 적물의 성분을 대표하는 것으로 해석한다. 표층 퇴적물의 희토류원소는 분화된 경희토류-중희토류의 비와 음의 Eu 이상 을 나타내어 상부 대륙지각과 매우 유사하다. 본 연구의 결과를 전 세계 강 하구 퇴적물 자료 및 국내의 큰 강 자료와 비교하였으며, 이를 통하여 지질 및 지형의 잠재적인 영향을 고려할 수 있다.

The damage to structures during an earthquake can be varied depending on the frequency characteristics of seismic waves and the geological properties of the ground. Therefore, considering such attributes in the design ground motions is crucial. The Korean seismic design standard (KDS 17 10 00) provides design response spectra for various ground classifications. If required for time-domain analysis, ground motion time series can be either selected and adjusted from motions recorded at rock sites in intraplate regions or artificially synthesized. Ground motion time series at soil sites should be obtained from site response analysis. However, in practice, selecting suitable ground motion records is challenging due to the overall lack of large earthquakes in intraplate regions, and artificially synthesized time series often leads to unrealistic responses of structures. As an alternative approach, this study provides a case study of generating ground motion time series based on the hybrid broadband ground motion simulation of selected scenario earthquakes at sites in the Nakdonggang delta region. This research is significant as it provides a novel method for generating ground motion time series that can be used in seismic design and response analysis. For large-magnitude earthquake scenarios close to the epicenter, the simulated response spectra surpassed the 1000-year design response spectra in some specific frequency ranges. Subsequently, the acceleration time series at each location were used as input motions to perform nonlinear 1D site response analysis through the PySeismoSoil Package to account for the site response characteristics at each location. The results of the study revealed a tendency to amplify ground motion in the mid to long-period range in most places within the study area. Additionally, significant amplification in the short-period range was observed in some locations characterized by a thin soil layer and relatively high shear wave velocity soil near the upper bedrock.

Daemadeung, located in the estuary of the Nakdong River, is formed by sand dunes and possesses well-developed intertidal flats. This study aimed to investigate the habitat of benthic microalgae, photosynthetic pigments, and photosynthetic efficiency in the intertidal flats of Daemadeung from January to December 2011. The inorganic nitrogen content in the sediment pore water was primarily composed of ammonium, while nitrate+nitrite was dominant in the upper layer water. The concentration of chlorophyll a and fucoxanthin in the sediment surface was significantly higher than the mean of all the sediment layer. The average Fv/Fm of benthic microalgae during the entire survey period was 0.52±0.03, with the highest value (0.61±0.08) observed in February. The rETRmax showed a seasonal trend, being high from spring to early autumn (April to October) and low from winter to early spring (January to March, November, December), with the highest value (153.05±2.30 μmol electrons m-2 s-1) in July and the lowest (38.49±5.17 μmol electrons m-2 s-1) in January. The average Fv/Fm of diurnal microalgae was 0.48±0.03, with the highest value (0.61±0.08) observed at noon. The rETRmax showed a highest peak at noon (54.24±11.35 μmol electrons m-2 s-1) and reached its lowest point at 16:00 (26.17±4.75 μmol electrons m-2 s-1). These findings suggest that the productivity of benthic microalgae varies significantly depending on the survey time and sediment depth. Therefore, to quantify the productivity of benthic microalgae using Diving-PAM, surveys should be conducted based on tidal conditions, and simultaneous pigment analysis of sediment layers should also be performed.

기후변화에 따라 수자원의 취약성이 증가하고 있고, 그로 인해 지하수 자원의 필요성이 강조되고 있다. 특히, 낙동강권역이 자리 잡은 한반도 남부는 매년 봄 가뭄과 같은 물 부족 현상이 빈번하게 발생하고 있다. 물 부족의 대안 으로 지하수 자원 이용이 대두되고 있으나, 지하수 자원의 활용에는 수질 안정성이 반드시 요구된다. 이 연구는 2023년 8월과 10월, 2회에 걸쳐 낙동강 하류 광려천 유역을 대상으로 지하수 관정 총 54개소와 하천수 총 5개의 지점에서 시 료를 채취하여 현장 수질 및 실내 수질 분석을 수행하였다. 현장에서 측정한 전기전도도의 값은 지하수와 하천수 모두 연구 지역 수계 하류로 갈수록 농도가 증가하는 경향을 보여 준다. 이는 하류의 농업 활동이 하천수에 직접적으로 유 입됨을 지시한다. 실내 수질 분석 결과 연구 지역의 수질 유형은 주로 [Ca-HCO3] 유형이 가장 많고, [Ca-SO4] 유형이 그 뒤를 이었다. 8월과 10월 시간에 따른 수질 유형의 변화를 확인하면, Ca 함량이 우세한 지역이 Na 함량이 우세한 지역으로 변화하고, 이러한 지하수 관정은 주로 하류에 위치하고 있음을 확인하였다. 결국 연구 지역 하류의 하천수·지 하수의 농도 변화는 공장단지, 폐수 처리시설, 농경지의 분포 현황 및 낙동강 하류의 유입과 밀접한 관계가 있고, 이를 통해 인위적인 오염이 발생하였음을 유추할 수 있다.

Stomatal pore is an important physiological trait that is closely linked to photosynthesis and transpiration as carbon dioxide and water vapor move through it between the atmosphere and plants. The present study investigated stomatal traits, such as stomatal density, index and size, of herbaceous native and alien plant species living in a riparian park on the Nakdong River to understand how those traits vary and to know if successful settlement of alien plants is attributed to those traits. There was no difference in stomatal density, index and size between native and alien plants with kidney-shaped stomata, suggesting that an empty ecological niche is not an essential prerequisite for the successful settlement of alien plants. Stomatal density showed a negative correlation with leaf thickness and leaf dry weight content (LMDC), but there was no correlation with Specific leaf area (SLA). All plants with kidney-shaped stomata had amphistomatous leaves, and the density and size of dumbell-shaped stomata were lower than those of kidney-shaped stomata.

This study analyzed the relationship between distribution of Bolboschoenus planiculmis which is main food source of swans (national monument species) with environmental factors, discharge, rainfall, and salinity in Eulsuk-do from 2020 to 2023. The distribution area of B. planiculmis in Eulsuk tidal flat was 103,672 m2 in 2020, 95,240 m2 in 2021, 88,163 m2 in 2022, and 110,879 m2 in 2023, and represents a sharp decrease compared to the 400,925 m2 area recorded in 2004. From 2020 to 2023, the growth densities of B. planiculmis were 243.6±12.5 m-2, 135.45±7.38 m-2, 51.10±2.54 m-2, and 238.20±16.36 m-2, respectively, and the biomass was 199.89±28.01 gDW m-2, 18.57±5.12 gDW m-2, 6.55±1.12 gDW m-2, and 153.53±25.43 gDW m-2 in 2020, 2023, 2021, and 2022, respectively. Based on discharge during May~July, which affects plant growth, the left gate discharge of the estuary barrage from 2020 to 2023 was 62,322 m3 sec-1, 33,329 m3 sec-1, 6,810 m3 sec-1, and 93,641 m3 sec-1, respectively; rainfall was 1,136 mm, 799 mm, 297 mm, and 993 mm, respectively; and average salinity was 14.7±9.4 psu, 21.1±4.7 psu, 26.1±2.7 psu, and 14.5± 11.1 psu, respectively. In 2022, cumulative rainfall (978 mm, about 70% of the 30-year average) and discharge (43,226 m3 sec-1) decreased sharply, resulting in the highest mean salinity (25.46 psu), and the distribution area, density, and biomass of the B. planiculmis decreased sharply. In 2023, there was a rise in discharge with an increase in rainfall, leading to a decrease in salinity. Consequently, this environmental change facilitated the recovery of B. planiculmis growth.

Invasive predators are one of the most damaging species groups to biodiversity. In the Nakdong River, the lake skygazer Chanodichthys erythropterus is a dominant species that is fiercely carnivorous and a concern for commercial fish. Although it is important to understand the ecological characteristics related to the feeding habit, studies on the diets of lake skygazer in Nakdong River have been limited to studies of gut contents. In this study, the trophic position (TP) and feeding habits of C. erythropterus were studied by calculating TPs using samples collected from 13 sites throughout the Nakdong River. Compound-specific isotopic analysis of amino acids provided reliable TPs from the muscle of Lake skygazer C. erythropterus without any isotope baseline. The results were approximately 3 to 3.6 and suggesting a carnivorous but size-dependent prey variation. In particular, the TP variability of C. erythropterus observed in the Nakdong River showed that it had a selective feeding habit compared to carnivorous fish species of relatively similar trophic levels.

This study was conducted to investigate the current status of seagrass species in the Nakdong River estuary from May to June 2023. To survey the seagrass habitat area, the Nakdong River estuary was divided into seven zones. Aerial photography using drones was conducted to find seagrass areas, GPS tracking was carried out on foot in the intertidal zone and by boat and SCUBA diving in the subtidal zone. To analyze the seagrass status, we measured the morphological characteristics, shoot density, and biomass of representative seagrass species in each zone. Four seagrass species were found in this area: Zostera japonica, Z. marina, Ruppia maritima, and Phyllospadix japonicus. The distribution areas of each species was 338.2 ha, 92.9 ha, 0.9 ha, and 1.4 ha, respectively, with a total area of 432.5 ha. Z. japonica was widely distributed in most of the tidal flats and mudflats of the Nakdong River estuary, while Z. marina was restricted to Nulcha-do, Jinu-do, and Dadae-dong. R. maritima occurred within the habitat of Z. japonica in Eulsukdo and Myeongji mudflats, and P. japonicus inhabited rocky areas in Dadae-dong. The shoot density of each species was 4,575.8±338.3 shoots m-2, 244.8±12.0 shoots m-2, 11,302.1±290.0 shoots m-2, and 2862.5±153.5 shoots m-2, respectively. The biomass of each species was 239.7±18.5 gDW m-2, 362.3±20.5 gDW m-2, 33.3±1.2 gDW m-2, and 1,290.0±37.0 gDW m-2, respectively. The results of this study revealed that Z. japonica was dominant in the Nakdong River estuary. In particular, Z. japonica habitats of Eulsukdo, Daema-deung, and Myeongji mudflats were identified as the largest in Korea. The Nakdong River estuary is an important site of ecological, environmental, and economic value, and will require continuous investigation and management of the native seagrasses.

Bolboschoenus planiculmis has been acknowledged as a key species in whooper swans (Cygnus cygnus) habitat by providing food for this migratory waterfowl. B. planiculmis wetlands are being degraded by water shortages and salinization caused by anthropogenic activities and climate changes. In 2004, the distribution of B. planiculmis in the tidal flats of the Nakdong Estuary was 2,475,568 m2, and in 2021, the distribution area was 798,731 m2, which decreased by 32.3%. In order to restore the degraded B. planiculmis wetlands, shoot transplantation and seed sowing were tentatively used in three places with different salinity and water levels. The average density per unit area in September at the optimal growth period after planting were A (fresh water level 50 cm) 58±15.65 m-2, B (brackish water level 0~5 cm) 188±63.83 m-2, C (brackish water level 0 cm or less) 188±45.13 m-2. The tubers were observed as A 0 g dw m-2, B 25.32±2.94 g dw m-2, and C 13.39±0.91 g dw m-2. Tubers were distributed in the soil, with only 3.0% at the 10~20 cm depth but 97.0% at the 0~10 cm depth. In contrast, the germination rate of B. planiculmis seeds was observed to be 0%. Results of this study provide technical support for the restoration of B. planiculmis wetland and the improvement in the quality of whooper swans habitat.