Assessing the ecosystem health status of Korea Gwangyang and Jinhae bays based on a planktonic index of biotic integrity (P-IBI)

To assess the responses of planktonic organisms to pollutants in the coastal ecosystems of Gwangyang and Jinhae bays in Korea, we investigated seasonal changes in various biological factors during the period from 2010 to 2012. Based on the characteristics of nutrient uptake by planktonic organisms under the coastal pollution conditions, we focused on four major parameters: total phytoplankton, harmful algal bloom (HAB) species, heterotrophic bacteria (HB) and Escherichia coli to develop a planktonic index of biotic integrity (P-IBI). The threshold values for abundances of total phytoplankton, HAB species and HB were based on the zero Z-score following normal distribution of the data for each parameter during the three years. Based on this approach, the threshold values were: 1.2 × 10⁶ cells L^?1 for total phytoplankton; 3.3 × 10⁴ cells L^?1 for HAB species; and 1.7 × 10⁶ cells mL^?1for HB. Five grade levels for the P-IBI were established, based on the zero Z-scores. The threshold value for E. coli not to be normalized was based on the USEPA and the Korean Ministry of Oceans and Fisheries guidelines. Validity of the grades and threshold values for each parameter established using the field data were tested by algal bioassays in a mesocosm enclosure, which supported the threshold values obtained in the field. In Gwangyang Bay, the annual integrated score for the P-IBI in 2010 was better than in the other years of the study. In Jinhae Bay, the P-IBI for the inner area of Masan Bay was Grade IV–V, indicating unhealthy conditions relative to the central and western outer areas, where the P-IBI varied from Grade II to III. The P-IBI values for Gwangyang and Jinhae bays were mostly rated as “Good (Grade II) or Fair (Grade III)”, except for a few stations in the semi-enclosed areas of the inner part of Jinhae Bay. From an overall view based on the P-IBI developed in this study, the coastal ecosystem health status in Gwangyang Bay was in a better condition than Jinhae Bay. The P-IBI indicated also a change to an unhealthy status during the rainy periods of spring and summer, whereas during winter and autumn the index indicated healthy conditions.     

Germination rate of Phyllospadix japonicus seeds relative to storage methods and periods

To determine the optimal storage method and longest possible storage period of Phyllospadix japonicus seeds, we examined post-storage germination rates using different storage methods and periods for P. japonicus seeds harvested in Korean coastal waters. P. japonicus seeds are classified as recalcitrant seeds with an average moisture content of 45.4%. Germination rates of P. japonicus seeds stored in seawater at 4 °C, seawater at room temperature with air supply, and an aquarium with continuous seawater circulation ranged from 35.0% to 43.5%, whereas seeds stored in seawater at 30°C, a refrigerator at ?20°C, and a desiccator at room temperature did not germinate. Seeds stored at 4°C maintained germination rates of 72.5～73.0% until 30 days of storage, but showed rapidly decreasing germination rates after 60 days and no germination after 180 days. Since few studies have investigated seed storage of P. japonicus, these results will serve as useful data for seed-based P. japonicus habitat restoration.     

Evidence for sediment recirculation on an ebb-tidal delta of the East Frisian barrier-island system, southern North Sea

The Otzum ebb-tidal delta, located between Langeoog and Spiekeroog islands along the East Frisian barrier-island coast, southern North Sea, was investigated with respect to its morphological evolution, sediment distribution patterns and internal sedimentary structures. Bathymetric charts reveal that, over the last 50 years, the size of the Otzum ebb-tidal delta has slightly shrunk, while sediment has accreted on the ebb-delta lobe to the east of the main inlet channel (west of Spiekeroog). Swash bars superimposed on the eastern ebb-tidal shoal (Robben Plate) have migrated south or south-eastwards, i.e. towards the inlet throat. The main ebb-delta body is composed of fine quartz sand, whereas the superimposed swash bars and the inlet channel bed consist of medium-grained quartz sand containing high proportions of coarser bioclastic material. Internal sedimentary structures in short box-cores (up to 30 cm long) are dominated by flood-oriented cross-beds. Longer vibro-cores (up to 1.5 m long) show that, at depth, the sediment is dominated by storm-generated parallel (upper plane bed) laminations with intercalated shell layers and dune cross-bedding. The cross-bedded sands in both box-cores and vibro-cores from the ebb-delta shoal predominantly dip towards the south or southeast, indicating transport towards the inlet throat by the flood current. The observations demonstrate that, contrary to previous contentions, the sediments of the highly mobile swash bars do not bypass the inlet but are instead being continually recirculated by the combined action of tidal currents and waves. In this model, the cycle begins with both fine and medium sands, including shell hash, being transported seawards in the main ebb channel until they reach the shallow ebb-delta front. From here, the sediment is pushed onto the eastern ebb-delta shoal by the flood current assisted by waves, becoming strongly size-sorted in the process. The medium sands together with the shell hash are formed into swash bars which migrate along arcuate paths over a base of fine sand back to the main ebb channel located south of the ebb delta. By the same token, the fine sand between the swash bars is transported south-eastwards by the flood current in the form of small dunes until it cascades into the large flood channel located to the west of Spiekeroog. From here, the fine sand is fed back into the main ebb channel, thus completing the cycle. No evidence was found on the ebb delta for alongshore sediment bypassing.     

Climate impact of transportation A model comparison

Transportation contributes to a significant and rising share of global energy use and GHG emissions. Therefore modeling future travel demand, its fuel use, and resulting CO₂ emission is highly relevant for climate change mitigation. In this study we compare the baseline projections for global service demand (passenger-kilometers, ton-kilometers), fuel use, and CO₂ emissions of five different global transport models using harmonized input assumptions on income and population. For four models we also evaluate the impact of a carbon tax. All models project a steep increase in service demand over the century. Technology change is important for limiting energy consumption and CO₂ emissions, the study also shows that in order to stabilise or even decrease emissions radical changes would be required. While all models project liquid fossil fuels dominating up to 2050, they differ regarding the use of alternative fuels (natural gas, hydrogen, biofuels, and electricity), because of different fuel price projections. The carbon tax of 200 USD/tCO₂ in 2050 stabilizes or reverses global emission growth in all models. Besides common findings many differences in the model assumptions and projections indicate room for further understanding long-term trends and uncertainty in future transport systems.     

Improved flood susceptibility mapping using a best first decision tree integrated with ensemble learning techniques

Improving the accuracy of flood prediction and mapping is crucial for reducing damage resulting from flood events. In this study, we proposed and validated three ensemble models based on the Best First Decision Tree (BFT) and the Bagging (Bagging-BFT), Decorate (Bagging-BFT), and Random Subspace (RSS-BFT) ensemble learning techniques for an improved prediction of flood susceptibility in a spatially-explicit manner. A total number of 126 historical flood events from the Nghe An Province (Vietnam) were connected to a set of 10 flood influencing factors (slope, elevation, aspect, curvature, river density, distance from rivers, flow direction, geology, soil, and land use) for generating the training and validation datasets. The models were validated via several performance metrics that demonstrated the capability of all three ensemble models in elucidating the underlying pattern of flood occurrences within the research area and predicting the probability of future flood events. Based on the Area Under the receiver operating characteristic Curve (AUC), the ensemble Decorate-BFT model that achieved an AUC value of 0.989 was identified as the superior model over the RSS-BFT (AUC = 0.982) and Bagging-BFT (AUC = 0.967) models. A comparison between the performance of the models and the models previously reported in the literature confirmed that our ensemble models provided a reliable estimate of flood susceptibilities and their resulting susceptibility maps are trustful for flood early warning systems as well as development of mitigation plans.     

Spatial Prediction of Rainfall-Induced Landslides Using Aggregating One-Dependence Estimators Classifier

In this study, the spatial prediction of rainfall-induced landslides at the Pauri Gahwal area, Uttarakhand, India has been done using Aggregating One-Dependence Estimators (AODE) classifier which has not been applied earlier for landslide problems. Historical landslide locations have been collated with a set of influencing factors for landslide spatial analysis. The performance of the AODE model has been assessed using statistical analyzing methods and receiver operating characteristic curve technique. The predictive capability of the AODE model has also been compared with other popular landslide models namely Support Vector Machines (SVM), Radial Basis Function Neural Network (ANN-RBF), Logistic Regression (LR), and Naïve Bayes (NB). The result of analysis illustrates that the AODE model has highest predictability, followed by the SVM model, the ANN-RBF model, the LR model, and the NB model, respectively. Thus AODE is a promising method for the development of better landslide susceptibility map for proper landslide hazard management.     

Investigating the impacts of typhoon-induced floods on the agriculture in the central region of Vietnam by using hydrological models and satellite data

Flooding associated with landing tropical cyclones (TCs) is one of the major natural hazards in the coastal region of Vietnam. Annually, approximately 5 or 6 TCs make landfall in Vietnam, bringing heavy rains and inducing flooding, particularly to the central coastal region because of its topography and geographic configuration. This study focuses on the modelling of typhoon-induced floods that have resulted in widespread damage to agriculture over the central Thua Thien Hue Province of Vietnam by coupling two well-known hydrological models, KINEROS2 and HEC-RAS (Daniel et al. in Open Hydrol J 5(1), 2011), and using GSMaP (Global Satellite Mapping of Precipitation) data as the satellite rainfall input. Landsat imagery and GIS are also used for mapping and analysing the inundated areas. The discharge and water level from the KINEROS2 and HEC-RAS models displayed acceptable results for the floods modelled from three selected typhoons; both the Nash–Sutcliffe simulation efficiency coefficient (NSE) and the coefficient of determination (R²) were greater than 0.6. The simulated inundation maps of these typhoon-induced floods were compared with those extracted from the Landsat imagery to assess consistency. The result revealed a similar spatial extension of the inundated agricultural areas. This information, together with the forecasted TC movements and associated rainfalls, will be helpful to plan methods for mitigating potential typhoon-induced flooding and damage, particularly damage to agricultural regions.     

Source and remediation for heavy metals of soils at an iron mine of Ulsan City,Korea

Ulsan mine produced the iron ore minerals of magnetite, arsenopyrite, and scheelite in 1992, and serpentine was developed from 1977 to 2002. The soils of the mine were contaminated by heavy metals such as As, Zn, Ni, and Cd. Heavy metals of Ni and Zn came mostly from serpentinite, and As was derived mainly from arsenopyrite in the scan-type iron ore body. As, Zn, and Ni were major contaminants, but Cd was a minor contaminant on a basis of Korean standard. The heavy metals in the deep depth (>?5 m) came from the host rocks, and those in the shallow depth (<?5 m) were derived from the organic–mineral complexation soil. The remediation plan was a soil washing for highly contaminated soils and the containment of clay materials for less contaminated soils. Even though the remediation methods were successful, the continuous monitoring and the analysis of monitoring data are still necessary for the conservation of soil and groundwater around the study area.