-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 sedimentrelated 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.

In freshwater ecosystems, habitat heterogeneity supports high invertebrate density and diversity, and it contributes to the introduction and settlement of non-native species. In the present study, we identified the habitat preferences and trophic level of Brachydiplax chalybea flavovittata larvae, which were distributed in four of the 17 wetlands we examined in the Yeongsan River basin, South Korea. Larval density varied across four microhabitat types: open water area, and microhabitats dominated by Myriophyllum aquaticum, Paspalum distichum, and Zizania latifolia. Microhabitats dominated by M. aquaticum had the highest larval density, followed by those dominated by P. distichum. The larvae were more prevalent in silt sediments than in plant debris or sand. Stable isotope analysis showed that B. chalybea flavovittata is likely to consume, as a food source, other species of Odonata larvae. We conclude that successful settlement of B. chalybea flavovittata can be attributed to their habitat preferences. As temperature increases due to climate change, the likelihood of B. chalybea flavovittata spreading throughout South Korea increases. We, therefore, recommend continued monitoring of the spread and ecological impacts of B. chalybea flavovittata.

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.

This study was conducted to investigate the influence of natural degrading polymer film covering in rice paddies on the benthic macroinvertebrate community structure in Dangsu-dong, Suwon, Gyeonggi-do from May 2009 to September 2009. We compared 5 treatments: golden apple snail farming (GF), natural degrading polymer film + organic farming (NOF), natural degrading polymer film + chemical farming (NCF), conventional farming (CF), and no fertilization (NF) as the control. The total number of species was highest in NOF followed by GF, NF, NCF, and CF. The total number of individuals was highest in NOF followed by NCF, CF, NF, and GF. The Dominance index (DI) ranged from 0.43 to 0.95. The highest dominance index was in GF followed by NCF, NF=CF, and NOF. The species diversity index (H') for each experimental plot ranged from 0.49 to 2.93. The average species diversity index was highest in NOF followed by NF, GF, CF, and NCF. After the natural degrading polymer film covered the paddies, the benthic macroinvertebrates tended to recover, but leeches and aquatic beetles increased. Mollusca and Annelida, which are sensitive taxa, decreased in both species and individual numbers after the soil was covered with the natural degrading polymer film. The number of species tended to recover. However, the number of individuals continued to decrease.d, especially individuals. Since then, the number of species tended to recover. However, the number of individuals decreased.

A series of ecological monitoring surveys was conducted to examine the characteristics of benthic macroinvertebrate community and evaluate the water conditions for lake Chung-Pyoung from August 2008 to April 2009. The benthic macroinvertebrate taxa represented total 84 species belonging to 52 families, 18 orders, 7 classes, 4 phyla from the qualitative and quantitative sampling. Among these, a total of 67 aquatic insect species(about 82%) were comprised of the major groups in all communities. The relative abundance of Ephemeroptera, Trichoptera, Odonata and Mollusca was 20%, 16%, 16% and 13%, respectively. According to the results, Chironomids were major dominant taxa. The primary dominant species was Chironomidae sp.1(92.18 23.28%) followed by Chironomidae sp.6 (65.52 46.69%), Parafossarulus manchouricus(61.29%), Limnodrilus gotoi(47.83%), Ecdyonurus levis(47.27%), Tanypodinae sp.(45.51%). The average values of dominant index(DI), diversity index(H'), evenness index(J'), and species richness index(R1) were 0.78(±0.13), 1.63(±0.62), 0.64 (±0.20), and 1.35(±0.52), respectively. The water quality of all the sites was oligosaprobic in average.