Jungho Nam

Improved water quality in response to pollution control measures at Masan Bay, Korea

The total pollution load management system (TPLMS) was first applied in 2007 to the highly developed Masan Bay watershed, Korea. To evaluate the effect of TPLMS on water quality improvement, we analyzed the water qualities in rivers and bay during 2005-2010, targeting chemical oxygen demand (COD), suspended sediment (SS), total nitrogen (TN), and total phosphorus (TP) loads. Land-based pollutant loading all decreased during this period, with a significant reduction in COD and SS loads (p<0.01). The COD reduction in seawater, following the TPLMS implementation, was also significant (p<0.01). Time-lagged responses in COD and Chl-a supported an estimated seawater residence time of ~1 month. Land-based nutrient loads were also significantly reduced for TN (p<0.01) and TP (p<0.05), however, significant reductions were not observed in the bay, indicating potential alternative nutrient inputs from non-point sources into the bay system.

Remote sensing and water quality indicators in the Korean West coast: Spatio-temporal structures of MODIS-derived chlorophyll-a and total suspended solids

The Yellow Sea is a shallow marginal sea with a large tidal range. In this study, ten areas located along the western coast of the Korean Peninsula are investigated with respect to remotely sensed water quality indicators derived from NASA MODIS aboard of the satellite Aqua. We found that there was a strong seasonal trend with spatial heterogeneity. In specific, a strong six-month phase-lag was found between chlorophyll-a and total suspended solid owing to their inversed seasonality, which could be explained by different dynamics and environmental settings. Chlorophyll-a concentration seemed to be dominantly influenced by temperature, while total suspended solid was largely governed by local tidal forcing and bottom topography. This study demonstrated the potential and applicability of satellite products in coastal management, and highlighted find that remote-sensing would be a promising tool in resolving orthogonality of large spatio-temporal scale variabilities when combining with proper time series analyses.

Linkage between Freshwater Inflow and Primary Productivity in Texas Estuaries: Downscaling Effects of Climate Variability

ABSTRACT Kim, H.; Son, S.; Montagna, P.; Spiering, B. and Nam, J., 2014. Linkage between freshwater inflow and primary productivity in Texas estuaries: Downscaling effects of climate variability. The estuaries of Texas are lagoons that lie in a climatic gradient in the northwestern Gulf of Mexico (GOM). Estuaries located in the northeastern part of the Texas coast receive more rainfall than estuaries in the southwestern part, and consequently greater runoff and concomitant freshwater inflow. Extreme inter-annual variability of precipitation caused by El Niño Southern Oscillation (ENSO) events is another characteristic of the Texas coast. During El Niño periods, salinities in Texas estuaries decrease because of increased precipitation and increased freshwater inflow to the coast. During La Niña periods, salinities increase due to drier climatic conditions and reduced freshwater inflow. The combination of the climatic gradient and temporal variability of freshwater inflow drive changes in the frequency, timing, duration, and magnitude of river flows to coastal waters, which in turn control the salinity, nutrients, organic matter, and sediments in Texas estuaries. Chlorophyll biomass, as an indicator of primary production, was estimated from Moderate Resolution Imaging Spectroradiometer (MODIS) data from July 2002 to December 2011 for all Texas estuaries. The climate patterns in the Pacific Ocean delivers a cascading signal via freshwater inflow changes to estuaries that effects primary production subsequently. The maximum correlation was found at the 5th lag (month) with correlation coefficient (ρ) being 0.45 (NIÑO3.4 is fixed as a reference). The combination of the local climatic gradient and quasi-periodic natural variability in ENSO has been influencing estuarine ecosystem dynamics over decadal scales in this region. The present study demonstrates that freshwater inflow is an important driver in maintaining primary productivity of Texas estuaries, which is required to maintain estuarine health and sustainability.

Analysis of forty years long changes in coastal land use and land cover of the Yellow Sea: The gains or losses in ecosystem services

The drastic land cover change and its impacts in the Yellow Sea have long been significant issues in terms of coastal vulnerabilities, but holistic data analysis is limited. The present study first reports 40 years long geographical changes of the Yellow Sea coasts including all three neighboring countries of China, North Korea, and South Korea. We delineated tidal flats by analysis of Landsat series satellite imageries (662 scenes) between 1981 and 2016. A total area of the Yellow Sea tidal flats has been considerably reducing for the past 36 years, from ∼10,500 km2 (1980s) to ∼6700 km2 (2010s), say ∼1% annual loss. A majority loss of tidal flats was mainly due to the grand reclamations that conducted in almost entire coast of the Yellow Sea, particularly concentrated in the 1990s-2000s. Coastal reclaimed area during the past four decades reached ∼9700 km2, including ongoing and planned projects, which corresponds to over half the area of precedent natural tidal flats of the Yellow Sea. The potential carbon stocks in the eight representative regions with large scale reclamation indicated significant loss in carbon sink capacity in the South Koreas coast (∼99%), while evidenced a lesser loss from the Chinas coast (∼31%). It was noteworthy that the progradation of tidal flats after the reclamation in Chinas coast significantly reduced the loss of carbon sequestration. According to the ecosystem services valuation for the Yellow Sea, a total loss was estimated as ∼8 billion USD yr-1 with relatively high proportional loss (up to 25%) of climate regulating services (viz., carbon sequestration). Overall, huge losses in ecosystem services being provided by the Yellow Sea natural tidal flats need immediate action to prevent or at least alleviate accelerating ecological deteriorations. Finally, future conservative policy direction on coastal wetlands management has been proposed towards enhancement of marine ecosystem services.

A comparative review and analysis of tentative ecological quality objectives (EcoQOs) for protection of marine environments in Korea and China

Ecological quality objectives (EcoQOs), as tools for implementing ecosystem approach, have long been acknowledged to protect the marine ecosystems and fisheries in regional seas through joint efforts by surrounding countries over the past decade. The present review analyzed the best available meta-data relating to the five ecosystem elements that were recently proposed by the Northwest Pacific Action Plan to evaluate the current status of coastal ecosystem health in marine environment of the Yellow Sea. We suggested the six tentative EcoQOs among five ecological quality elements including: 1) biological and habitat diversity; 2) invasive species; 3) eutrophication; 4) pollutants; and 5) marine litters. Environmental status was assessed, depending on the EcoQOs targets, by comparison to the world average values, existing environmental standards, or reported values of other regional seas. Results of analysis revealed that among the six tentative EcoQOs, two target objectives to marine biodiversity and concentrations of nutrients (viz., DIN and DIP) were met towards good environmental status. Whilst, three EcoQOs relating to hypoxia and red-tide, pollutants (persistent toxic substances and metals), and marine litters (including microplastics) did not meet and one relating to invasive species could not be judged due to insufficient data sets. The biggest weak point for developing suitable EcoQOs and assessing status of ecosystem health could be insufficient meta-data sets available and/or discrepancy in methodological details cross the data-sets or between the two targeted countries. Thus, the cooperation of neighboring countries, viz., Korea and China for the Yellow Sea, is necessary for the ecosystem based management of our regional sea in the future. Overall, this first time review for the assessment of target tentative EcoQOs in the Yellow Sea region encompassing coasts of Korea and China would provide a better understanding of the current status of environmental pollution and ecosystem health.