At a time when anthropogenic activities are increasingly disturbing the overall ecological integrity of freshwater ecosystems, monitoring of biological communities is central to assessing the health and function of streams. This study aimed to use a large nation-wide database to develop a multimetric index (the Korean Benthic macroinvertebrate Index of Biological Integrity—KB-IBI) applicable to the biological assessment of Korean streams. Reference and impaired conditions were determined based on watershed, chemical and physical criteria. Eight of an initial 34 candidate metrics were selected using a stepwise procedure that evaluated metric variability, redundancy, sensitivity and responsiveness to environmental gradients. The selected metrics were number of taxa, percent Ephemeroptera-Plecoptera-Trichoptera (EPT) individuals, percent of a dominant taxon, percent taxa abundance without Chironomidae, Shannon’s diversity index, percent gatherer individuals, ratio of filterers and scrapers, and the Korean saprobic index. Our multimetric index successfully distinguished reference from impaired conditions. A scoring system was established for each core metric using its quartile range and response to anthropogenic disturbances. The multimetric index was classified by aggregating the individual metric ..scores and the value range was quadrisected to provide a narrative criterion (Poor, Fair, Good and Excellent) to describe the biological integrity of the streams in the study. A validation procedure showed that the index is an effective method for evaluating stream conditions, and thus is appropriate for use in future studies measuring the long-term status of streams, and the effectiveness of restoration methods.

Conserving and enhancing freshwater biodiversity are global issues to ensure ecosystem integrity and sustainability. To meet this, it is critical to understand how the biological assemblages are determined by environmental gradients in different spatial scales. Nevertheless, information on their large-scale environmental relationships remains scarce in Korea. We aimed to understand nationwide spatial distribution patterns of benthic macroinvertebrates and important environmental factors affecting their distribution in 388 streams and rivers across Korea. A total of 340 taxa, belonging to 113 families in 23 orders of five phyla, were identified. Assemblage composition in most Korean streams included a few predominant colonizers and a majority of rare taxa. Cluster analysis based on benthic macroinvertebrates classified a total of 720 sampling sites into five clusters according to the pollution levels from fast-flowing less polluted streams with low electrical conductivity to moderately or severely polluted streams with high electrical conductivity and slow water velocity. Canonical correspondence analysis revealed that altitude, water velocity and streambed composition were the most important determinants, rather than watershed and water chemistry variables, for explaining the variation in macroinvertebrate assemblage patterns. The results provide basic information for establishing the conservation and restoration strategies of macroinvertebrate biodiversity against anthropogenic disturbances and developing more confident bio-assessment tools for diagnosing stream ecosystem integrity.

Understanding the relationship between benthic macroinvertebrates and environmental variables is the first step toward establishing sustainable freshwater ecosystems in terms of biodiversity, and this knowledge can be applied in river management. We analyzed major environmental variables that affect biotic communities on the national scale in the Republic of Korea. To achieve this goal, 2647 sampling stream sites were surveyed from 2016 to 2018 to collect benthic macroinvertebrates and measure 14 environmental variables. We identified a total of 359 taxa, belonging to 32 orders in 9 classes of 5 phyla, most of which were aquatic insects including Ephemeroptera, Odonata, Plecoptera, Coleoptera, Diptera and Trichoptera. Two-way indicator species analysis (TWINSPAN) based on biotic communities divided the sampling sites into six groups. Discriminant analysis identified gradient, streambed substrates, velocity, biological oxygen demand (BOD) and altitude as the major environmental variables that distinguished each TWINSPAN group. In addition, stream order and stream width also influenced aquatic macroinvertebrate communities, but the influence was low. The indicator taxa in each group were gradually changed from sensitive organisms preferring high altitudes, fast velocities and coarse substrates to tolerant organisms preferring low altitudes, slow velocities and fine substrates in each group from one to six. Canonical correspondence analysis confirmed that the composition of benthic macroinvertebrate communities in the Republic of Korea was dependent on stream gradient, microhabitat, organic pollution and geographical feature rather than on stream size or other water quality variables. Our study identified variables affecting the overall distribution patterns of biotic communities on a national scale and provides useful information for conservation and management of stream ecosystems in the Asian monsoon region.

Benthic macroinvertebrate functional feeding groups (FFGs) are influenced by the availability of food sources, which can be affected by stream size and gradient. We investigated the spatial distribution patterns of FFGs by stream size (stream order, catchment area and stream width) and gradient (altitude and slope). In addition, we attempted stream classification based on the distribution patterns of FFGs. To achieve these goals, a total of 996 sampling sites of national scale located in the Republic of Korea were investigated from 2008 to 2016. Among the five physical variables, stream width and slope showed linear relationships with the indicator values of FFGs. These two physical variables had larger influences on the distribution of FFGs compared to other variables. Geology (the type of rocks) showed little influences on the distribution of benthic macroinvertebrate communities. We classified streams focusing on catchment (stream size) area and altitude (stream gradient) because they are constants that do not change with disturbances. The FFGs and benthic macroinvertebrate assemblages were distinctly changed by stream types, indicating that the stream classification criterion adequately represented changes in physical variables in biotic terms. In addition, the distribution of FFGs and biotic assemblages showed that benthic macroinvertebrates in the Republic of Korea were more influenced by the altitude (stream gradient) than the catchment area (stream size). In overall, this study found that the stream size and gradient markedly influence the distribution of FFGs in national regions of the Republic of Korea. Further research is needed focusing on the level of microhabitats and other parameters to identify the promising variables that influence biotic distribution.

Aquatic macrophytes determine the physical structure of many microhabitats in water and strongly influence the distribution of various aquatic animals. In this study, we analyzed the main microhabitat characteristics that affected the spatial distribution of invertebrates in shallow wetlands of South Korea (Jangcheok Reservoir). Environmental variables, macrophyte biomass, and invertebrate groups were used to analyze invertebrate distribution using a self-organizing map (SOM). Thirteen invertebrate groups were mapped onto the SOM, and each group was compared with the distribution of environmental variables and macrophyte biomass. Based on a U-matrix, five clusters were categorized according to Euclidean distance on the SOM. Invertebrate groups were closely related to macrophyte biomass. In particular, Lymnaeidae, Physidae, Viviparidae, Ecnomidae, and Hydrophilidae were abundant in quadrats with a high cover of Paspalum distichum and Nelumbo nucifera. Bithyniidae and Coenagrionidae were strongly associated with Trapa japonica and Hydrocharis dubia, whereas Planorbidae, Corduliidae, and Hydrophilidae were abundant with a high cover of Typha orientalis. Similar habitat preferences were found in a survey of gastropod distribution on the surface of each macrophyte species. The results clearly indicated that invertebrate distribution clusters were related to the spatial distribution of aquatic macrophytes in a shallow wetland.

In recent years, Non-Point Source Pollution has been rising as a significant environmental issue. The sediment-laden water problem is causing serious impacts on river ecosystems not only in South Korea but also in most countries. The vegetative filter strip (VFS) has been thought to be one of the most effective methods to reduce the transport of sediment to down-gradient area. However, the effective width of the VFS first needs to be determined before VFS installation in the field. To provide an easy-to-use interface with a scientific VFS modeling engine, the Web GIS-based VFSMOD system was developed in this study. The Web GIS-based VFSMOD uses the UH and VFSM executable programs from the VFSMOD-w model as core engines to simulate rainfall-runoff and sediment trapping. To provide soil information for a point of interest, the Google Map interface to the MapServer soil database system was developed using the Google Map API, Javascript, Perl/CGI, and Oracle DB programming. Three modules of the Web GIS-based VFSMOD system were developed for various VFS designs under single storm, multiple storm, and long-term period scenarios. These modules in the Web GIS-based VFSMOD system were applied to the study watershed in South Korea and these were proven as efficient tools for the VFS design for various purposes.