This paper provides an overview of the development and application of the National Aquatic Ecological Monitoring Program (NAEMP) in Korea, which uses biological and habitat–riparian criteria for river/stream and watershed management. Development of NAEMP began in 2003, with recognition by the Korean Ministry of Environment (MOE) of the limitations of applying chemical parameters (e.g., biochemical oxygen demand (BOD)) as the principal targets of water environment management. Ecosystem health criteria under NAEMP were developed from 2003 to 2006. Candidate sites for monitoring were also screened and established across the country. NAEMP was implemented in 2007, and since then a standard protocol of nationwide monitoring based on multi-criteria has been implemented to assess the ecological condition of rivers and streams. The monitoring results indicate that many Korean rivers and streams are severely degraded, with biological conditions that are much worse than their water chemistry suggests. In 2009, 24% of rivers and streams were in classes C (Fair) and D (Poor) for BOD, but more than 71, 53, and 27% were categorized as Fair to Poor according to fish, diatom, and benthic macroinvertebrate assemblages, respectively. NAEMP is promising in that the results have already had great impacts on policy making and scientific research relevant to lotic water environment and watershed management in Korea. In the future, NAEMP results will be used to develop more aggressive regulations for the preservation and restoration of rivers/streams, riparian buffer areas and watersheds. Another future aim of the NAEMP is to develop aquatic ecological modeling based on the monitoring results.

The diatoms are an ecologically important group of algae that have been extensively studied by ecologists and taxonomists. However, the large-scale patterns of diatom distribution and the factors underlying this distribution are largely unknown. The aims of this study were to identify the large-scale spatial patterns of benthic diatom assemblages in Korean streams and rivers, and to assess the importance of numerous environmental factors on diatom distribution. We classified 720 study sites based on diatom flora. Benthic diatoms, water chemistry, altitude, and riparian land cover and use were characterized by multivariate analyses, Monte Carlo permutation tests, and indicator species analysis. In total, we identified 531 diatom taxa. Diatom assemblages were mostly dominated by species of the genera Achnanthes, Navicula, Nitzschia, Cocconeis, Fragilaria (Synedra included), Cymbella, Gomphonema, and Melosira. Cluster analysis partitioned all 720 sites into eight groups based on diatom species composition. Canonical correspondence analysis indicated that altitude, land cover and use, current velocity, electrical conductivity, and nutrient levels explained a significant amount of the variation in the composition of assemblages of benthic diatoms. At the national scale, a downstream ecological gradient was apparent, from fast-flowing, mostly oligotrophic highland streams to slow-flowing, mostly eutrophic lowland rivers. Our data suggest that spatial factors explain some of the variation in diatom distribution. The present investigation of the spatial patterns of benthic diatoms, the ecological determinants of diatom occurrence, and the identification of diatom indicator species contributes to development of a program for assessing the biological integrity of lotic ecosystems in Korea.

Anthropogenic land use within watersheds has substantial effects on aquatic habitats and biological communities. From September 2006 to December 2008, we investigated the effects of land use on benthic macroinvertebrate communities by comparing Song Stream and Odae Stream, two adjacent mountain streams in Korea whose watersheds have different land use patterns. Song Stream is significantly disturbed by agricultural activities in the watershed, whereas Odae Stream is relatively undisturbed and is surrounded by a well-conserved forest area. Song Stream had significantly higher levels of all nutrients and sediment-related factors due to the adjacent agricultural area. As a result, Song Stream had markedly lower species community indices, such as taxa richness and abundance. In Song Stream, macroinvertebrate scrapers and predators were most adversely affected, whereas collector-gatherers became a dominant group. Based on correlation and multivariate analyses, total dissolved solids had the strongest negative relationship with macroinvertebrate assemblages, followed by electrical conductivity, total nitrogen, and pH. The proportion of cobble in stream substrate was positively related to the richness and abundance of macroinvertebrates. Our results indicate that disturbances caused by agricultural land use, particularly sand deposition, had significant adverse effects on macroinvertebrate habitats and on the biotic integrity of benthic macroinvertebrate communities.

Benthic macroinvertebrates are considered as a representative taxon that indicates the ecological status of freshwater ecosystems. Numerous indices derived from community data have been proposed to estimate either biological water quality or ecosystem health. In this study, metrics based on benthic macroinvertebrates at the family level were screened using ecological informatics to provide a multi-metric measurement that would be suitable for presenting ecological integrity across different levels of environmental impact. Benthic macroinvertebrates were collected at a total of 720 sample sites from river basins and streams in Korea in 2009. Based on four categories of community status (i.e., diversity, richness, tolerance, and composition), 37 metrics were selected as initial candidates according to the literature. The candidate metrics were evaluated according to parameters including discriminatory power, redundancy, and responsiveness to stressors. Self-organizing map was utilized to assist the screening procedure by providing ordination, clustering, and visualization of metric and environmental data. Six metrics were finally selected as a multi-metric and were compared with conventional indicators for presenting the ecological integrity of streams.

Stream development can generate environmental changes that impact fish communities. In temperate streams, the distribution of fish species is associated with environmental gradients. To analyze the relevant factors, large-scale exploration is required. Thus, to evaluate the distribution patterns of fish in Korea, sampling was conducted on a national scale at 720 sites over a 6-week period in 2009. A total of 124 fish species in 27 families were identified; Zacco platypus and Zacco koreanus of the Cyprinidae were the dominant and subdominant species, respectively. Of the species found, 46 (37.1%) were endemic and 4 (3.2%) exotic; of the latter, Micropterus salmoides and Lepomis macrochirus were widely distributed. Upon canonical correspondence analysis (CCA), both altitude and biological oxygen demand (BOD) were highly correlated with CCA axes 1 and 2, respectively. This explained 62.5% of the species–environment relationship. Altitude and stream order were longitudinally related to species distribution. The numbers of both total and endemic species gradually increased as streams grew in size to the fourth–fifth-order, and decreased in sixth-order, streams. Overall, fish communities were stable throughout the entire watershed, whereas some species showed site-specific occurrence patterns due to the paleogeomorphological characteristics of Korean peninsula. However, various anthropogenic activities may negatively affect fish communities. Therefore, both short- and long-term sustainable management strategies are required to conserve native fish fauna.

The objectives of this study were to evaluate fish guild compositions and national river health using a multi-metric model of the Korean index of biological integrity using fishes (K-IBIF) in four major Korean watersheds along with water chemistry and habitat quality. Tolerant and omnivore fish species dominated all the watersheds, and the proportions of tolerance guilds and trophic guilds reflected water chemistry and habitat quality. The number of sensitive species and insectivore species had negative correlations (r < −0.42, P < 0.01) with chemical water quality (biological oxygen demand (BOD)), while tolerant species and omnivore species had positive correlation (r > 0.27, P < 0.05) with BOD values. Physical habit conditions, based on qualitative habitat evaluation index (QHEI) model, indicated a “good” condition (mean = 68.9; range = 45–105) in three watersheds, except for the Yeongsan River watershed. Values of QHEI were significantly correlated (R2 > 0.4, P < 0.01) with nitrogen and phosphorus levels in all watersheds, suggesting that habitat degradation is associated with eutrophication. Model values of K-IBIF in the watersheds averaged 18.2, indicating a “fair” condition, and about 37% of all observations in K-IBIF model values were judged as a “poor” health condition, indicating severe health impairment. Overall, our data suggest that degradation of the river health was due to a combined effect of chemical pollution and physical habitat modifications. This research provides valuable information on Korean river conservation and restoration in the future.

This study investigated the relationships of three major aquatic assemblages (diatom, macroinvertebrate, and fish) and environmental variables, including sub-basin, hydrology, land cover, and water quality variables on multiple scales. Samples were collected at 720 sampling sites on the Korean nationwide scale. Geological variables, including altitude and slope, showed a strong positive correlation with proportions of forest in land cover types and cobbles in substrates, while they were negatively correlated with water quality variables, including conductivity and total phosphorus. Considering the concordance of the different assemblages, species richness of fish and macroinvertebrates displayed significant correlation, and diatoms were significantly correlated with fish. However, diatoms did not show significant correlation with macroinvertebrates. Altitude and slope showed significant correlation with all biological variables of the three assemblages. Macroinvertebrates and fish showed positive relations with large substrate sizes. Indices of diatoms and macroinvertebrates well reflected the perturbation of water quality variables. However, fish indices showed a relatively low association with water quality variables, compared with those of diatoms and macroinvertebrates. These patterns were also confirmed by the ordination and prediction of biological indices with environmental variables through the learning process of a self-organizing map as well as random forest. Overall, our study supports the concept of multi-scale habitat filters and functional organization in streams, and is consistent with the recommended use of multiple biological indices with more than one assemblage for the assessment of the biotic integrity of aquatic ecosystems.

Despite numerous previous studies, relationships between watershed land use and adjacent streams and rivers at various scales in Korea remain unclear. This study investigated the relationships between land uses and the physical, chemical, and biological characteristics of 720 sites of streams and rivers across the country. The land uses at two spatial scales, including a 1-km buffer and the base watershed management region (BWMR), were computed in a geographical information system (GIS) with a digital land use/land cover map. Characteristics of land uses at two spatial scales were then correlated with the monitored multidimensional characteristics of the streams and rivers. The results of this study indicate that land use types have significant effects on stream and river characteristics. Specifically, most characteristics were negatively correlated with the proportions of urban, rice paddy, agricultural, and bare soil areas and positively correlated with the amount of forest. The site-scale and BWMR-scale analyses suggest that BWMR land use patterns were more strongly related to ecological integrity than they were to site land use patterns. Improving our understanding of land use effects will largely depend on relating the results of site-specific studies that use similar response techniques and measures to evaluate ecological integrity. In addition, our results clearly indicate that the characteristics of streams and rivers are closely linked and that land use types differentially affect those characteristics. Thus, effective restoration and management for ecological integrity of lotic system should consider the physical, chemical, and biological factors in combination.

Stream restoration is an important process affecting the ecological health of stream ecosystems. There have been numerous cases of restoration, dealing with either structural or biological changes. In Korea, most restoration projects have merely dealt with improving hydrological characteristics or water quality; however, in recent years the improvement of ecological characteristics has been an increasing focus for restoration projects. In this study, we utilized data collected from 5675 stream sites in May 2007 to discover general patterns of anthropogenic modification in Korean streams. The survey results after application of the stream modification index (SMI; presence or absence type; high scores indicate more disturbed) provided a general distribution of disturbed/undisturbed streams or rivers in the watershed. We then compared the level of modification with the socio-geographical patterns (population, land coverage, elevation, and slope) for the watershed. The results show that streams in highly populated areas suffered from human modification compared with other well-preserved stream sites. In metropolitan cities, urbanized areas had positive relationship as identified by a high SMI. On the other hand, agricultural land cover identified an SMI increase for lowland river area. In general, mountainous streams possessed a better status in stream morphology due to different land-cover patterns (i.e., mainly forested area); however, some mountainous areas were impacted by concentrated summer rainfall. We could distinguish the forcing variables (i.e., land use pattern) for the disturbed streams through a comparison between the SMI and geographical information; the SMI application was able to identify areas of high necessity for restoration.