This study presents a modified version of the Lake Benthic Macroinvertebrate Multimetric Index (LBMMI) originally proposed by Park et al. (2024) in Korea. Among the six core metric elements of LBMMI, two elements-total number of taxa and the proportion of predator taxa-were excluded, as they were considered to be strongly influenced by vascular hydrohytes following eutrophication. The revised LBMMI was constructed using the remaining four metrics: Pielou’s evenness index, proportion of insect taxa, individual proportion of oligochaetes and chironomids with blood tubules, and proportion of clinger taxa. Compared to the original LBMMI, the modified index showed approximately a 6% improvement in explanatory power for the first principal component (PC 1) in principal component analysis of environmental factors, and it also exhibited a broader range of discrimination. These results suggest that the modified LBMMI can be more effectively utilized for environmental assessment of lake ecosystems.

Biological assessments of streams have been developed in many countries to evaluate ecological integrity. A multimetric index is one of the primary methods used for this purpose, incorporating chemical, physical, and biological variables of the environment. In Korea, the Benthic Macroinvertebrates Index (BMI) is currently applied in national biological monitoring programs; however, BMI reflects only organic pollution and does not account for other environmental variables in streams. This study aimed to develop a new multimetric index, the Benthic Macroinvertebrate-based Multimetric Index (BMMI), for assessing the ecological integrity of Korean streams. We analyzed data from 3,307 sites, including water quality information. Reference and disturbed streams were identified based on PC 1 scores with 7 environmental factors (Axis 1 of the PCA), genus levelbased taxa richness, and BMGI values used for trimming. From an initial set of 82 candidate metrics, six (genus level-based taxa richness, Shannon’s diversity index, percent of taxa in E.P.T., percent of individuals in collectorsgatherers, percent of individuals in clingers, BMGI based on saprobity) were selected through statistical analyses, including coefficient of variation and discriminant analysis. BMMI successfully distinguished between reference and disturbed streams and showed significant correlations with various environmental factors. These results indicate that BMMI is suitable for evaluating the ecological integrity of streams in Korea. Therefore, it is recommended that stream ecosystem assessments transition from BMI to BMMI in the future to provide a more comprehensive evaluation of stream integrity.

Current assessments of stream ecosystem health in Korea using benthic diatoms rely primarily on the Trophic Diatom Index (TDI), which is highly sensitive to phosphorus concentrations but has limited ability to capture complex environmental stressors such as organic pollution and physical habitat degradation. To address these limitations and enhance the ecological diagnostic capacity of diatom-based assessments, we developed a Korean-type multimetric diatom index, the Diatom Assessment Index (DAI). Using benthic diatom assemblage data and environmental variables collected from 3,029 sites nationwide between 2019 and 2021, we screened candidate metrics based on variability, redundancy, discriminatory power, and sensitivity analyses. Five metrics-TDI, proportion of motile diatoms, proportion of sensitive diatoms, proportion of saprophilous diatoms, and the [Achnanthes / (Achnanthes+Navicula)] ratio-were ultimately selected and integrated to calculate the DAI score. Applying the DAI to an independent dataset from 3,005 sites (2022~2024) demonstrated that the index exhibited a near-normal distribution across assessment classes, in contrast to the TDI, which tended to be skewed toward specific ranges. The DAI showed strong correlations not only with physicochemical parameters such as BOD and TP but also with physical habitat indicators, including flow velocity and the proportion of fine substrates. In addition, the DAI was significantly correlated with other biological indices, such as the Benthic Macroinvertebrate Index (BMI) and the Fish Assessment Index (FAI). These results indicate that the DAI provides a more comprehensive and ecologically meaningful measure of stream health in Korea and can serve as an effective tool for national aquatic ecosystem assessment and management.

Structural property in communities of aquatic insects and benthic macroinvertebrates could reflect the impact of environment on aquatic ecosystems. Benthic macroinvertebrates were collected at 18 different lakes across different levels of environmental impact in Korea. Community responses were analyzed by species abundance distribution (SAD). Rank-abundance (or relative abundance) curves were evaluated by classical SAD (Geometric series, Log-series, and Lognormal distribution) and niche apportionment models (dominance pre-emption, random assortment, random fraction, and dominance decay). Geometric series was more accepted in lakes among classical SAD models. Niche apportionment models were observed in a diverse manner across different level of ecological integrity in lakes. Dominance decay model and random fraction model were frequently fitted to the lakes with higher integrity, while dominance pre-emption and random assortment models tend to be presented in low to middle range in integrity.