This study evaluated the management priority of small catchments in the Nam River basin, comprehensively considering the impact of non-point pollution sources for water quality improvement. Water quality data from the Water Environment Measurement Network and additional field survey data were collected to understand the water quality status at the small catchment level. The management priority was calculated by integrating data on pollution sources, land cover, and runoff using a weighted method. As a result, the E08-2 small catchment, located downstream of the Nam River, showed the highest priority, followed by A18, B09, E04, and A19. The main factor influencing the water quality improvement priority was the pollution source characteristics within the small catchment, especially the influence factor and land use condition. This study contributes to the efficient water quality management of the Nam River basin by identifying the priority by small catchment through analysis that simultaneously considers point and non-point pollution sources.

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.

Busan and Gyeongsangnam-do region host numerous significant wetlands, including the Nakdong River Estuary, one of the largest migratory bird habitats in East Asia, making it an essential habitat for waterbirds. However, issues such as wetland area reduction have arisen due to accelerated industrialization and urbanization since the 1980s. This study analyzed annual and monthly changes in waterbird populations and examined habitat use patterns and interrelationships among four wetlands in Busan and Gyeongsangnam-do: the Nakdong River Estuary (NRE), Lower Nakdong River (LNR), Junam Reservoir (JUR), and Upo Wetland (UPO), using waterbird data collected from 1999 to 2024. The results showed a decreasing trend in waterbirds at the NRE and UPO, while an increasing trend was observed at the LNR and JUR. Notably, populations of Anatidae decreased at the NRE and UPO but increased at the LNR and JUR, indicating that changes in Anatidae significantly influenced waterbird population trends. Monthly population fluctuations were particularly pronounced at the NRE and LNR. While the population decreased at the NRE after November, it increased at the LNR. This suggests that waterbirds moved to the LNR due to habitat and food resource reductions in the NRE. In contrast, the JUR and UPO exhibited weaker associations with the other sites. This study aims to contribute to future wetland management and waterbird conservation strategies in the Busan and Gyeongsangnam-do region.

This study investigates the role of Junam Reservoir and its surrounding paddy fields as a habitat for migratory birds by considering how different scenarios of habitat loss may affect their populations. It will focus on wintering Anatidae species and take advantage of the population data available for Junam Reservoir and adjacent agricultural fields to analyze habitat-use and dependency patterns. A Bayesian regression model was fitted to estimate the relative dependency at each reservoir and paddy field for each bird species. Network analysis was used to assess the interaction structure and connectivity between habitats and bird species. Furthermore, habitat loss scenarios were simulated in order to predict the outcome of reservoir-paddy field loss on the populations of birds. Among these species, the reservoir loss was much more critical for those highly dependent on reservoirs, such as bean goose, Anser fabalis, and Whooper swan, Cygnus cygnus, but the loss of paddy fields became much more vital for those with higher dependence on paddy fields, such as Baikal teal, Anas formosa. Species that depended on both types of habitats, such as the white-naped crane (Antigone vipio) and the hooded crane (Grus monacha), had additive impacts and suffered the most significant population decline when both reservoirs and paddy fields were lost simultaneously. Network analysis demonstrated that both reservoirs and paddy played equally critical roles in the central nodes of the migratory bird species habitat network and acted as important connectors along migration routes. It is exemplary of the need to develop landscape-level means of maintaining migratory birds and ecosystem stability through the incorporation of ecological connectivity between paddy fields and reservoirs and vice-versa. This stresses integrated management relevant for the entire habitat network rather than single-site focused management, a call for multifaceted conservation efforts, securing of alternative habitats, and restoration of degraded habitats.

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.

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.

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.

The predator-prey interaction in freshwater ecosystems is a crucial area in the ecological study field and one of example to find such interaction is to investigate stomach contents. However, traditional method through visual inspection often induce misidentification, as it depends critically on intactness of physically visible data. In this study, we utilized Next-Generations Sequencing (NGS) technology to test the applicability stomach content analysis and overcome such limitation. NGS was applied to analyze the stomach contents of the Hemibarbus labeo, Tachysurus fulvidraco, and Plecoglossus altivelis collected in the lower part of Nakdong River. As a result, T. fulvidraco had a higher number of Animalia operational taxonomic units (OTUs) intake rate than H. labeo. At the same time, P. altivelis had higher number of Plantae OTUs intake rate than T. fulvidraco and higher Protozoa OTUs intake rate than H. labeo respectively. Therefore, NGS technology application enable to overcome traditional method’s limitation and discover hidden interspecific interaction which can further be used in appropriate habitat assessment.

The research was based on long-term studies on the major physico-chemical and hydrological factors and zooplankton community dynamics in the Hwang River. We had 341 times survey and collected zooplankton samples in the Hwang River of mid-Nakdong River from 1995 to 2013. We identified 97 zooplankton species, including 77 rotifers, 16 cladocerans, and 4 copepods. The total zooplankton abundance and species diversity were shown distinctive temporal variation (ANOVA, p<0.001). Annual average of zooplankton population density was 58.4±3.2 ind L-1 (n=341) and the lowest was 17.0±3.8 ind L-1 (1996, n=20), while the highest was 151.5±32.3 ind L-1 (2010, n=22). For zooplankton, small rotifer groups (e.g., Keratella sp., Brachionus sp., Trichotria sp.) dominated the study site for 19 years survey. Statistical analysis revealed that there were positive relationships with SiO2 (p=0.002) and water level (p<0.001) for the high abundance of rotifer community. There were considerable variations both the total cladocerans population and the number of cladocerans’ species concerning annual precipitation. Despite the appearance of various zooplankton in the Hwang River, the mean population density remained low. Due to the lateral structures in the Nakdong River, the downstream basin of the Hwang River is inevitably affected. The zooplankton community in our study site is considered to be mainly influenced by external factors that can stably increase and maintain the volume of the water body and internal factors that induce an increase in food sources through the inflow of nutrients into the water body.

Anthropogenic disturbances on freshwater ecosystem are known to degrade biodiversity, especially on fish assemblage. In this study, we have conducted fish surveys to identify impact of a bridge construction on fish assemblages. A total of eight study sites were surveyed in the Danjang and the Dong Stream in southern part of South Korea from June to November in 2021. The fish samplings were carried out five times, using cast-nets (10×10 mm mesh size), scoop-nets (4×4 mm, 5×5 mm mesh size), set-nets (10×10 mm mesh size), and fish traps (3×3 mm mesh size), along with the Stream/River Ecosystem Survey and Health Assessment by the Ministry of Environment of Korea and basic water quality measurement. Also, we applied the species diversity index and length-weight relationship regressions on certain species to identify interspecific growth rate differences in accordance with study sites. As a result, a total of 782 individuals, 23 species and 10 families were collected. The dominant species was Zacco Koreanus and relative abundance was 50.89%. When applying the length-weight relationship regressions on certain species, the ‘b’ value for Z. Koreanus was lower at the downstream points than at the upstream points of the construction site. In addition, when comparing to the results of the past survey, relative density of demersal fish at the upstream and downstream points decreased from 26% to 1.4%, and from 18% to 6.3%, respectively. In conclusion, it is considered that bridge construction negatively affects the habitat of fishes, especially on demersal fishes. Therefore, appropriate conservation efforts such as installation of silt protector and sand sedimentation pond are needed to alleviate the disturbance in habitat such as occurrence of turbidity and destruction of micro-habitats.

본 연구는 낙동강지류인 밀양강에 소상한 연어를 대상으로 소상, 산란 분포를 최초로 파악하고 소상 한계선을 확인 하였다. 2020년 10월 25일부터 11월 28일까지 확인된 개체들 중, 사체는 전장을 측정하고 암-수 구별을 하였다. 조사 결과 총 40개체의 연어를 발견하였으며 이 중 사체는 25마리, 살아있는 개체는 15마리였다. 대부분 산란장으로 판단 되는 지점 인근 수변부에서 살아있는 개체와 사체가 발견되었다. 연어의 소상 한계선 파악의 경우 연어가 소상할 수 없는 형태의 보가 등장할 때까지 상류방향으로 이동하여 확인 하였으며, 밀양강 본류의 경우 예림교 기준 상류 13 km, 지천인 단장천의 경우 밀양강 합류부에서부터 12 km까지 연어의 소상이 가능할 것으로 확인하였다. 따라서 연어가 소상 하기 위한 보의 철거 및 어도설치와 같은 하천연결성 확보가 필요한 것으로 판단되며, 연어의 치어생존률을 높이기 위한 산란장 및 미소서식처 자연성 확보 방안이 필요할 것으로 판단된다.

본 연구에서는 영산강, 섬진강 유역에서 호소 간의 동물 플랑크톤의 군집구조 특성이 만수면적에 따라 분류된 소· 중·대형의 저수지에서 종 수 및 개체수가 유의한 차이를 보이는 것을 확인하였다. 윤충류보다 지각류에서 민감도가 높은 것을 확인하였으며, 특히 두 분류군 모두 양의 상관 관계를 나타냈지만, 지각류에서 조사지점이 늘어날수록 개체수 증가가 확연한 것을 알 수 있었다. 또한 네트워크 분석 개념을 활용한 고유벡터 중심성 및 그룹화 분석을 사용 하여 호소 간의 동물플랑크톤 군집구조를 비교했을 때, 만수면적에 따른 대·중·소형 호소 내에서도 지리적 특성과 미소환경 공간의 차이점을 구별할 수 있었다. 따라서 이러한 특성을 볼 때, 네트워크 분석은 담수 동물플랑크톤 군집구조 분석에 있어 만수면적 크기, 지리적 특성, 미소환경 특성을 반영할 수 있는 것으로 고려된다. 마지막으로, 네트워크 분석은 다양한 군집분석을 간소화하며 시각화를 통한 직관적 이해를 돕는 데 유용할 것이다.

We analyzed research topics, temporal distribution of field sites, and researcher network of 1,508 limnology publications in the Korean Journal of Limnology (1968~2012) and the Korean Journal of Ecology and Environment (2013~2017). We found that water quality and sediment, phytoplankton, invertebrates, and fish were major subjects during the study periods. Survey of flora and fauna and physiological experiment of freshwater species were the largest subjects during 1970~80s, while other subjects including production, behavior, modeling, and ecological assessment have been rapidly increased since the 1990s. Most of the biological taxa equally studied lotic and lentic system, however, invertebrates and fish related studies more focused on the lotic system. Spatially, the field site of Korean limnology studies was found to be concentrated in main river channels runs through urban areas and artificial lakes than preserved natural areas. Freshwater system, located at the elevation range of 301~400m(upstream of main channels), had the lowest number of field sites. Collaboration among researchers and different institution types have been steadily increased and expanded as the number of publications increased.

In order to consider application and evaluation of value and class of domestic wetland, we investigated 146 wetlands located Gyeongsangnam-do using Rapid Assessment Method (RAM). We utilized Self-Organizing-Map (SOM) to analysis relationship between evaluation index and land coverage ratio surrounding wetland. Among total 8 evaluation index, ‘Fish and herptile habitat’ and ‘Aesthetic value’ were higher, most of the wetlands evaluated as 2, 3 grade. Result of SOM analysis, ‘vegetation diversity and wild animals habitat’ is negatively related to the ‘Fish and herptile habitat’, because fishs were not prefer habitat excessively occupied by plant. However, high vegetation diversity can be support high score of ‘Aesthetic’ in wetland. Also, ‘Erosion control’ and ‘Flood storage and control’ were closely related, wetlands with high score of ‘Erosion control’ have high score of ‘Flood storage and control’. When applied RAM in domestic wetland, six out of 6 evaluation index induced biased results, the index of RAM need a little change as some new or modify evaluation index. Therefore, we consider to need adjustable, subdivide, and actualization of some evaluation index for application of RAM in domestic wetlands. Consequently, wetland assessment and class using RAM can be utilized as important indicate for conservation and management of wetland, and contributed greatly to maintain biodiversity include to endangered species by preserving remaining wetland.