This study explores the relationships between environmental factors and the distribution of epilithic diatoms in 161 estuaries of three coastal areas on the Korean peninsula. We investigated epilithic diatoms, water quality, and land use in the vicinities of the estuaries during the months of May 2012, 2013 and 2014, because Korea is relatively free from the influences of rainfall at that time of year. We recorded 327 diatom taxa from the study sites, and the assemblage was dominated by members of the Naviculaceae. Bacillariaceae accounted for the largest proportion of diatoms, and Nitzschia inconspicua (18%) and N. frustulum (9.6%) were the most dominant species. A cluster analysis based on epilithic diatom abundance suggested that the epilithic diatom communities of Korean estuaries can be classified into four large groups (G) according to geography, as follows: Ia—the East Sea watershed, Ib—the eastern watershed of the South Sea, IIa—the West Sea watershed, and IIb—the western watershed of the South Sea. The former two groups, Ia and Ib, showed higher proportions of forest land cover and use, higher species occurrence, lower salinity, lower turbidity, and lower concentrations of nutrients than the latter two groups, while the latter groups, IIa and IIb, had higher proportions of agricultural land cover and use, higher electrical conductivity, higher turbidity, higher concentrations of nutrients, and lower species occurrence. The environmental factors underlying the distribution of epilithic diatoms, representative of each region, are as follows: dissolved oxygen and forest land cover and use for Reimeria sinuate and Rhoicosphenia abbreviate of the East Sea (ES), salinity and turbidity for Tabularia fasciculate of the West Sea (WS), and biochemical oxygen demand (BOD) and nutrients for Cyclotella meneghiniana of the WS. On the other hand, the most influential environmental factors affecting the occurrence of indicator species showing the highest indicator values (>60%) of each group were electrical conductivity for Navicula saprophila and Reimeria sinuate of Ia, and turbidity for Encyonema minutum of IIa. Collectively, the distribution of epilithic diatom communities inhabiting Korean estuaries are determined by geographical factors and water quality, which are in turn influenced by land cover and use, and which differ from east to west.

Mosquitoes are a public health concern because they are vectors of pathogen, which cause human-related diseases. It is well known that the occurrence of mosquitoes is highly influenced by meteorological conditions (e.g., temperature and precipitation) and land use, but there are insufficient studies quantifying their impacts. Therefore, three analytical methods were applied to determine the relationships between urban mosquito occurrence, land use type, and meteorological factors: cluster analysis based on land use types; principal component analysis (PCA) based on mosquito occurrence; and three prediction models, support vector machine (SVM), classification and regression tree (CART), and random forest (RF). We used mosquito data collected at 12 sites from 2011 to 2012. Mosquito abundance was highest from August to September in both years. The monitoring sites were differentiated into three clusters based on differences in land use type such as culture and sport areas, inland water, artificial grasslands, and traffic areas. These clusters were well reflected in PCA ordinations, indicating that mosquito occurrence was highly influenced by land use types. Lastly, the RF represented the highest predictive power for mosquito occurrence and temperature-related factors were the most influential. Our study will contribute to effective control and management of mosquito occurrences.

Industrial effluent containing heavy metals discharged into streams may pose high toxicity risks to aquatic organisms and to human health. Therefore, it is important to understand how to change the amount of effluent with heavy metals discharged from industries into open aquatic ecosystems both for effective management of heavy metals and to foster sustainable ecosystems. This study was conducted to characterize the release of heavy metals from industries based on the Pollutant Release and Transfer Registers database in Korea from 1999 to 2010. From the database, we selected nine heavy metals (Pb, Cd, Mn, Sb, Cu, Zn, Cr, Sn, and Ni) and compared the differences in their effluent for different types of industries. The heavy metal effluents released into freshwater ecosystems were classified into four clusters through the learning process of the self-organizing map. Cluster 1 was characterized by the relatively higher effluent volumes of heavy metals, whereas cluster 4 had lower effluent volumes. The different patterns of the effluent volumes in heavy metals were closely associated with the differences of industrial types, and the changes of effluents of heavy metals reflected the changes in regulations and laws for aquatic ecosystem management.