Zooplankton are dominant pelagic consumers in lake ecosystems with high population and biomass. Their broad geographical distribution, ease of quantification, and rapid responses to abiotic environmental factors, such as eutrophication, acidification, and climate change, make them highly suitable as indicator organisms for assessing lake ecosystem health. The multi-metric index (MMI) provides an effective framework for capturing the complex responses of biological communities to varying environmental stressors, making it a valuable approach for improving the practical effectiveness of lake ecosystem management based on biological assessments. This study introduces the Lake Zooplankton Assessment Index (LZAI), developed for 90 lakes in South Korea. The LZAI comprises four components: a sensitive species index based on cladocerans, a eutrophication index based on rotifers, a food web index based on copepods, and a habitat index based on species diversity. Applying the LZAI to 90 lakes showed that lake grades followed a normal distribution regardless of sampling season, though A-grade and E-grade lakes exhibited greater seasonal variability. When compared with the clustering results based on zooplankton community composition, the LZAI closely reflected the underlying patterns in community structure. However, in brackish lakes-where population densities are lower and Calanoida copepods dominate relative to freshwater lakes-the M1 and M4 indices were consistently low, while M2 and M3 were high. This suggests that the LZAI requires index adjustments tailored to regional and lake-type factors, including size, depth, and salinity. Incorporating biomass data into the index would further improve the accuracy of assessing community structure and its role in nutrient and energy cycling.

This study analyzed and presented zooplankton species occurrence, diversity distribution, and community composition in ninety lakes across South Korea using samples collected through the “Survey of Lake Aquatic Ecosystem Status and Health Assessment.” When comparing our results with the National Species Checklist, we identified factors within each of the three taxa that warrant improvement due to their influence on diversity assessments. To bridge the gap between the ongoing lake ecosystem surveys and the continually updated National Species Checklist-and to enhance the accuracy of diversity evaluations-we conclude that (1) greater taxonomic rigor must be reflected in the national checklist, and (2) the limitations of morphology-based identification (α-taxonomy) must be addressed. Because the National Species Checklist does not distinguish among species, subspecies, and morphospecies, it can give rise to taxonomic oversplitting and taxonomic inflation, leading to ambiguous diversity-index results. Moreover, the low resolution of morphological identification for zooplankton (at the genus, family, or class level) can introduce errors when comparing communities across habitats or detecting non-native introductions. Although alternatives such as environmental DNA and functional diversity exist, they require further refinement before being adopted in policy; therefore, they should be implemented alongside and in comparison with current aquatic ecosystem health assessment methods.

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.

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.

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 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 note summarizes the application of zooplankton indices for water quality management and estimation based on main research topics of articles focusing on wetland ecosystems, topics that are remained poorly investigated in S. Korea. The aquatic ecosystem-based consists of indices that respond to different target environmental factors, including environmental disturbance. Among the major indicator species and biota, we reviewed that management strategy for the wetland environment has to be focused more on small-sizes, in terms of zooplankton ecology and indices. The ecology of zooplankton communities in freshwater ecosystem has been the focus of an increasing number of studies since 2019, and considerable progress has been made in understanding the major mechanisms involved in regulating their abundance, diversity and spatio-temporal patterns. Even though studies on the freshwater ecosystem in Korea have a long history, a few of studies on zooplankton biota were conducted at wetlands. We suggested the candidate zooplankton indices proposed by the U.S. EPA and EU to suit Korean conditions. In the step of selecting metrics, the best available metrics are species-related variables, such as composition and abundance, as well as richness and diversity. Overall, in spite of several limitations, the development of a plankton-based multivariate assessment method in Korea wetlands is possible using mostly field research data. Later, it could be improved based on qualitative metrics on zooplankton, and with the emergence of further survey data. The present information can be used as basic information for researchers who are dealing with aquatic environments and its interaction with organisms.

본 연구에서는 남극 로스해 연안에 서식하는 아델리펭귄(Pygoscelis adeliae)과 황제펭귄 (Aptenodytes forsteri)의 분변 시료를 기반으로 펭귄 장내 미생물 메타지놈 연구를 수행하였 다. Taxonomy 분석 결과, 아델리펭귄과 황제펭귄의 장내 미생물에는 주로 7개의 문(phylum), 18개의 과(family)가 존재하는 것으로 나타났다. 또한 미생물 다양성을 평가하기 위해 Alpha diversity 및 OTU abundance 분석을 수행한 결과, 전반적으로 아델리펭귄의 장내 미생물 다양 성이 황제펭귄보다 높은 것을 확인하였고, PCoA를 기반으로 한 Beta diversity 분석을 통해 두 개체군 간 장내 미생물 군집에 차이가 존재함을 확인하였다. PICRUSt를 활용한 기능적인 차원의 KEGG pathway 분석을 통해서는 아델리펭귄과 황제펭귄 시료에서 nucleoside and nucleotide biosynthesis pathway가 가장 많이 존재하는 것을 확인하였다. 본 연구를 통해 남극 아델리펭귄과 황제펭귄의 장내미생물 구성과 다양성을 비교분석 할 수 있었다. 본 연구 결과 는 향후 펭귄의 먹이 섭식 관련 연구에 활용될 수 있으며, 더 나아가 다양한 남극 생물의 장내 미생물 메타지놈 분석에 대한 기초가 될 수 있을 것이다.

This study compares the abundance and community structure of zooplankton organisms from pelagic regions, and considers particularly the trophic levels vs. zooplankton abundances and biomass. Zooplankton samples were collected three times from May to November 2022, at 30 temperate lakes and reservoirs, which belong to four different river basins. The total zooplankton abundance, biomass and species index were showed considerable spatial variation. The spatial pattern of rotifer abundance was similar to that of total zooplankton abundance, while there were not showed similar patterns of zooplankton biomass (μg L-1) in lentic ecosystems. The rotifer strongly dominated the zooplankton assemblage in smaller lentic system than that of larger. A total of 130 species of zooplankton were identified (83 rotifers, 34 cladocerans and 13 copepods). The total average of zooplankton abundance and biomass were 213.7±342.3 Ind. L-1 (n=129) and 1382.8±1850.4 μg L-1, respectively. Total and average of zooplankton abundance were usually dominated by the rotifers (>56.9%), while those of zooplankton biomass were dominated by the cladocerans and copepods (>73.6%) in lentic ecosystems. Considering the Trophic State Index (TSI), the factors of zooplankton abundance and biomass were included in between meso- and eutrophic states (27 lakes, 90% of all). The mean abundance and biomass of zooplankton in eutrophic systems were higher than that of meso- and hypertrophic systems. From this result, we suggest that management strategy for the lentic ecosystem water environment has to be focused more on small-sized lakes and reservoirs, in terms of zooplankton assemblages.

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.