The objective of this study was to develop an index of biological integrity (IBI) for national-level monitoring of watersheds as an ecosystem health assessment methodology for the South Korean government. A 10-metric IBI model (IBI KW ) was developed for watershed management and then applied to 76 streams in four major watersheds in Korea. The model assessments showed that 32.9% of all streams were judged to be in 'excellent-good' condition, whereas 67.1% were in 'fair-poor' condition, indicating severely impaired ecological health. Nutrient analyses of stream water revealed a two-to fivefold increase in nutrient and biological oxygen demand (BOD) levels in urban-and cropland-dominant streams compared to forest-dominant streams. The guild structure within the watersheds indicated that tolerant species were predominant in severely degraded regions (BOD>6 mg L −1 ), and sensitive species were distributed in regions with BOD<2 mg L −1 . Factors affecting ecosystem health (IBI KW scores) included chemical water quality parameters, physical habitat parameters and land use around the stream. In particular, land use was one of the major factors influencing ecosystem health, as indicated by the strong relationships between the percentages of urban and forest streams and the IBI KW scores. The integrated ecosystem health assessment technique developed here can be applied for both regular bioassessments and post-restoration assessments.

-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 0.27, 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 (R 2 > 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.

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The objectives of this study were algal control and health assessments in a temperate eutrophic reservoir. Laboratory and mesocosm-scale in situ topdown biomanipulation experiments using planktivorous fishes and filter-feeding macroinvertebrates were conducted along with identification of the limiting nutrient using nutrient enrichment bioassays (NEBs), and ecosystem health evaluation based on the modified index of biological integrity model (Reservoir Ecosystem Health Assessment; REHA). Nutrients and N/P ratio analyses during 5 years revealed that the reservoir was in a eutrophic-hypertrophic state and that the key limiting nutrients, based on the NEBs, varied among seasons. Reservoir trophic guilds indicated declines in sensitive and endemic fish species and dominance of tolerant omnivores. Model values from multimetric REHAs averaged 25.8, indicating that the ecological health was in "fair to poor" condition. Overall microcosm biomanipulation tests suggested that macroinvertebrates, specifically Palaemon paucidens and Caridina denticulata, were effective candidates for phytoplankton control, compared to fishes. In situ mesocosm experiments revealed the highest removal rates with bluegreen algae and a phytoplankton size fraction of 2-19 μm (R e >90%, Mann-Whitney U= 64.5-74.0, p<0.01), the dominant fractions in the reservoir. Our biomanipulation technique may provide a key tool for efficient management and restoration of eutrophied reservoirs.

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