Artificial vegetation island (AVI), which is mimicry of natural floating island, is one of ecotechnology for water quality improvement and restoration of disturbed aquatic ecosystem, and AVIs were launched in Lakes Paldang and Paro, Lakes of Korea to test their effectiveness. In Lake Paldang, an eutrophic lake, AVI could be acting as nutrients remover, but efficiencies was not clearly observed, but under the AVI, fish and zooplankton were more abundant than bulk lake water. In oligotrophic Lake Paro, where littoral zone was perfectly destroyed, AVI was installed as substitute for littoral zone. By microbial activities, Iris and other macrophytes on AVI were growing well and fishes were coming. We conclude that AVIs could be launched for partial restoration of disturbed ecosystem of oligotrophic and eutrophic lakes.

Grateloupia asiatica and G. divaricata are edibile marine red algae that commonly occur on the east coast of Korea: G. asiatica occurs in sheltered locations such as estuaries or tide pools, and G. divaricata usually grows at the depth of 2~5 meters under the sea where freshwater flows. We compared growth pattern of both species in Aninjin, Gyoam, Hosan, and Sacheon in order to find suitable location for mass culture of the Grateloupia species. In case of G. asiatica, vegetative and tetrasporangial thalli were found in Gyoam and Sacheon, while gametophytic thalli were found in Aninjin. Population from Aninjin was the largest on the average length of thalli (20.6 cm) among populations studied. Population of G. divaricata in Sacheon seems to be maintained mostly with sporophytes. However, Aninjin and Hosan populations consisted of gametophytes and sporophytes in summer. Population from Hosan was the largest on the average length of thalli (19.8 cm). Based on our results, G. asiatica and G. divaricata repeat a typical triphasic life history of red algae on the east coast of Korea.

Fish kill incidents are not rare in the upstream region of the Han River where overall water quality is suitable for supporting a fish community. However, the causes of fish kills are often not identified. In this study we examined the cause of a fish kill in an upstream tributary of the North Han River (Seo Stream, Yanggu County). In the field survey at the time when the fish kill occurred, the results did not indicate any harmful concentrations of heavy metals or toxic pesticides. Instead several tons of gingko (Ginkgo biloba) seed coat wastes were found in the water along the reach of fish kill site. Because gingko is known to be toxic, it was suspected as a cause of the fish kill. Recently gingko production has been increasing in Korea, and it is common practice for farmers to wash the seed coats of seeds in streams because the seed coats are toxic and emit an offensive odor. Toxicity of gingko fruit to humans is well known, but the toxicity to aquatic biota has not been previously reported. We investigated the toxicity of gingko seed coat extract to an invertebrate (Daphnia magna) and a fish (Oryzias latipes). After 48 hours exposure to seed coat extract the EC50 of Daphnia immobilization was 0.35% of a mixture corresponding to a dissolved organic carbon (DOC) concentration of 413 mgC L−1. In the fish experiment, the LC50 after 96 hours exposure was 0.4% of the extract mixture corresponding to a DOC of 440 mgC L−1. Thus gingko seed coat is toxic to aquatic animals and gingko washing was the likely cause of the fish kill incident. Our results suggest that gingko seed coat waste should be treated properly and not disposed of in streams.

To investigation the type of riparian vegetation and distribution, I studied the three streams, which is located in central district of Korea (Anyang Stream, Gap Stream, Seom River) from March of 2007 to December of 2008. Five different vegetation types were classified exception naked and openwater region. Natural forest type includes forest vegetation like as Quercus acutissima community and riparian woodland like as Salix koreensis community. Long and wet type of grassland consists of Phragmites australis community and so on. Robinia pseudoacacia plantation was representative of Woodland afforestation type. Short and dry type of grassland includes Elymus annuus and Humulus japonicus community. Cultivation land type. On the natural streamside was mainly made of natural riparian vegetation type, but in the artificial streamside consists of short and dry type of grassland. Riparian vegetation correlated with revetment structure, stream terrace, and microtopographical diversity. It showed that the vegetation type was divided clearly in the natural or artificial streamside.

Many animals are capable of detecting sensory information emitted by predators. When predation risk is high, orb-web building spiders should change its foraging strategy of the web construction. We examined web building behaviors of an orb-web spider, Argiope bruennichi providing sensory information of its predator, a yellow hornet, Vespa simillima. We observed web characteristics after providing sensory information of the yellow hornet (experimental group; N=29) and compared to the control group (no information provided; N=34). We hypothesized that the spiders in the experimental group would decrease investments in its web construction and stabilimentum decoration to avoid being located by the predator. The results rejected our hypothesis. Web and stabilimentum constructions decreased in the course of the experiment in both control group and experimental group. But the differences between control group and experimental group were not significant. The individuals did not reduce its stabilimentum length and did not decrease its web area in spite of sensory information of the predator.

Various problems such as erosion, leaching, and dispersion of tailings have occurred in abandoned mine areas. Especially, huge damage was caused by erosion of tailings by heavy rains in the research areas. Mine tailing of Sangdong tungsten contains various kind of heavy metals and Arsenic (As) exceeds more than 90 times than standard. In case this heavy metal flows into stream by erosion, serious damage is predicted. After experimenting Miscanthus sinensis growth of Mycorrhizae in comparison between infected and uninfected Mycorrhizae, plant infected by Mycorrhizae showed increased figures in average grass growth length (cm/ month), average organic body quantity (gfw/month) and average dry weight (gdw/month) by 47%, 33%, 32% respectively. Because of the small quantity of organic matter contained in the tailing of abandoned mine areas, the use of Mycorrhizae would be comparatively effective. This study suggests the use of Mycorrhizae infected plant to prevent erosion in abandoned mine waste areas.