• Environmental Engineering Research
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• v.15 no.2
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• pp.117-121
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• 2010

The continual extraction and indiscriminante use of groundwater for residential sectors could cause a decrease in the groundwater level in Para$\tilde{n}$aque river and Las Para$\tilde{n}$aque City; and allows saltwater to penetrate into the aquifer due to the proximity of Manila Bay. This study models the present condition and extent of saltwater intrusion in the aquifer bounded by Para$\tilde{n}$aque river River and Manila Bay. The model is simulated using a 3D finite element modeling software (FEMWATER) that is capable of modeling the groundwater flow condition in the aquifer. Moreover, the model can also be used to predict the future condition of the aquifer for better groundwater management. This study aims to raise public awareness of the extent of the problem and the possible side effects incurred. The model will serve as a basis for further studies on remediation techniques and saltwater intrusion control in the coastal aquifer of Para$\tilde{n}$aque river City.

• Proceedings of the Korean Aquaculture Society Conference
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• 2004.05a
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• pp.513-513
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• 2004

Manila clam, Ruditapes philippinarum, is commercially and ecologically important marine bivalve in Korea and japan. However, clam landings in the two countries have dramatically declined since the 1980-1990's. In the present study, the protozoan parasite, Perkinsus sp., lectin (host's defense-related glycoprotein) and histopathological features were investigated in Manila clams collected from Gomso Bay in Korea and Ariake Bay in japan (one of the largest clam beds in each country) during summer and fall, 2002-2003. DNA sequences of non-transcribe spacer (NTS), internal transcribed space. (ITS) and 5.85 rRNA of Perkinsus sp. were identical to those of P. atlanticus that was reported in Europe and Korea. For diagnosis of Perkinsus, the fluid thioglycollate medium (FTM) and the 2 M NaOH lysis methods were used. Prevalence of the parasite varied from 92.5-98.7% in Gomso Bay and 35.5-37.9% in Ariake Bay. Infection intensity, in terms of the number of Perkinsuscells per gram tissue wet weight, in the clams of Gomso Bay in fall 2002 averaged 1,010,077-470,937 recording approximately100 times higher than that of Ariake Bay, and these were twice higher than those of summer samples in each location. Mean hemagglutination titer of the clams from Gomso Bay was approximately 60-folds higher than that of clams from Ariake Bay in 2002. In histological preparation of the clams from Gomso Bay in 2002, trophozoites of P. atlanticus were in groups and resulted in severe inflammatory response of host clam. Prevalence of the trematod, Cercaria tapes-like in the clams of Gomso Bay and Ariake Bay were 8.8 % and 10.5% respectively. In conclusion, the clams from Gomso Bay showed more severe pathologic symptoms and higher immune response than those of the clams from Ariake Bay.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.4
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• pp.323-330
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• 2012

Manila Bay is home to the Port of Manila with three harbors: North Harbor, South Harbor and MICT(Manila International container Terminal). There is an adjacent fishing port to the north and another port across the Bay, the Limao Port. This study focuses on the volume of traffic movement in the Bay area taken from Manila VTMS raw data of the arrival and departure movements only. It is a two-year period of study of 2010 and 2011 traffic volume. It divides the data according to their numbers; to their sizes measured in gross tons; to the time of vessels' movements, whether daytime or night-time; and to each voyage trade: domestic or foreign. Quantitative values are calculated from the raw data based on the whole population of the two-year period. The results are illustrated by tables and graphs. Statistical measures are applied to determine the spread and frequencies of the data and test any significance from the hypotheses. These are shown in the tabulated form and interpreted to give a better picture of the frequency and volume of traffic. In the end, a summary is offered where it is hoped that this paper will propel further studies of improving the safety behavior in the premier port of the country.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.4
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• pp.555-563
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• 2015

Organic matter and trace metals were investigated in surface sediments of Gomso Bay, where there is dense Manila clam Ruditapes philippinarum farming activity, to evaluate contamination of sediments in intertidal shellfish farming area. We measured mean grain size (Mz), chemical oxygen demand (COD), ignition loss (IL), acid volatile sulfide (AVS), total organic carbon (TOC), and total nitrogen (TN), and trace metals (As, Cd, Cr, Cu, Fe, Hg, Mn, Pb and Zn) in intertidal and sublittoral sediments. The intertidal sediments were mainly composed of coarser sediments (sand, silty sand, and sandy silt), with Mz values ranging from 2.61 to 4.79 Ø. Mz and the content of organic matter in sediments were lower in the intertidal zone than in the sublittoral zone. The mean metal concentrations in surface sediments decreased in the order Fe > Mn > Zn > Cr > Pb > Cu > As > Cd > Hg. The metal concentrations in surface sediments showed a significant positive correlation with Mz and organic matter content, indicating that metal concentrations in the surface sediments of Gomso Bay are controlled by Mz and organic matter. The concentrations of organic matter and trace metals in the study region were lower than or similar to those in other intertidal zones in western coast and much lower than those reported in other shellfish farming areas in Korea. Our results suggest that intertidal Manila clam farming sediments from Gomso Bay are not contaminated by organic matter and trace metals.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.5
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• pp.511-518
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• 2019

Evaluating the habitat suitability of potential aquaculture sites for cultured species is critical to the sustainable use of tidal flats. This study evaluated the habitat suitability index (HSI) of 12 sites in a tidal flat aquaculture farm at Geunso Bay, Taean, in June 2016. The parameters used to model the suitability index were Growth (water temperature, chlorophyll ${\alpha}$, hydrodynamics), Survival (sediment-sand, mean size, air exposure), and Environment (DO, salinity). The HSI was calculated using weighted and No weighted geometric means. The results showed high habitat suitability at the bay's entrance (HIS; No weighted, 0.60-0.70; weighted, 0.60). Hydrodynamics, air exposure, sediment-sand and mean size are thought to have a significant impact on habitat selection by Manila clams Ruditapes philippinarum. This study explored the optimum habitat for Manila clams by calculating the HSI, providing basic data for tidal flat management.

• Environmental Engineering Research
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• v.15 no.3
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• pp.173-179
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• 2010

Pasig River is an important river in the Metro Manila, Philippines, since it provides food, livelihood and transport to its residents, and connects two major water bodies; Laguna de Bay and Manila Bay. However, it is now considered to be the toilet bowl of Metro Manila due to the large amount of wastes dumped into the river. Even with the efforts of the government to revive the quality of the Pasig River and its tributaries, it continues to deteriorate over time. This paper provides an overview of the current condition of the Pasig River. The existing water management policies were reviewed, and the issues and challenges hindering the improvement of its water quality identified. Moreover, the water qualities of the rivers in Metro Manila were compared to those of the major rivers in South Korea. The current watershed management system practiced by South Korea has been discussed to serve as a guideline for future recovery of the water quality of the rivers in the Philippines.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.869-877
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• 2017

Recently, Gomso Bay saw a decrease in the production of manila clam, which accounted for 17.8 % of production across the whole country in 2015, while Geunso Bay saw an increase that raised its contribution to 49.1 %. The tidal flats in these bays are inhabited by various benthos, and material flows in and out according to the tide. It is essential to understand the mass balance of these regions while giving consideration to the characteristics of these tidal flats. In this study, we compared areas where aquaculture farms were located in Gomso Bay with those without from May to August 2015. We divided the region into three sea areas (Sector I, Sector II, and Control), and the mass balance was estimated using the LOICZ model. As a result, the DIP of Sector II in Gomso Bay and another region in Geunso Bay, where a manila clam farm was located, were found to be -207.2 kg/day and 77.2 kg/day. The DIN was -4,996.7 kg/day and 926.6 kg/day. These results suggest that Gomso Bay han a higher density than Geunso Bay, which is thought to be mainly due to the feeding action of organisms. Therefore, in order to maintain a healthy tidal flat ecosystem and to sustain the production of manila clams, sustainable management to reduce the high density of tidal flat farms is necessary.

• Ocean and Polar Research
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• v.43 no.4
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• pp.365-370
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• 2021

Manila clam Ruditapes philippinarum is present at high rates of density in tidal flats in Cheonsu Bay on the west coast of Korea, where clams often exhibit mass mortalities in late summer. We monitored the pathologic condition of clams at Hwangdo tidal flat (HD) to understand the parasitic impacts on clam fitness. Manila clams were fully ripe in July and spawned during August and September, as the histology indicated. The histology revealed that clams in HD tidal flats were heavily infected by the protozoa parasite Perkinsus olseni, as the monthly prevalence ranged from 53% (September) to 93% (August). In addition, Manila clams were co-infected by the metazoan parasite Cercaria tapetis and Parvatrema duboisi with the prevalence of 0-33% and 0-14%, respectively. Massive hemocyte infiltration and subsequent inflammation were commonly observed from the gills of P. olseni infected clams. Clusters of P. olseni trophozoites and heavy hemocyte infiltration were also observed from the female gonad, suggesting that P. olseni interferes with host gonad maturation. The larval trematode occupied almost the entire host gonad, resulting in gonad castration. In addition, Metacercaria of P. duboisi were observed from the subsurface of the mantle. Ray's fluid thioglycollate medium assay (RFTM) indicated that clams collected in August and September contained approximately 4.0×106 P. olseni cells/g gills. Condition Index (CI) declined gradually from spring to early summer, and the decline in CI was interpreted as a consequence of the heavy parasitism, as the parasites drain the host's net energy to be used in somatic growth and gamete production.

• Environmental Engineering Research
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• v.21 no.4
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• pp.373-383
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• 2016

Cheonsu Bay, one of the most important in Korea as a coastal fishery is a semi-enclosed bay that is surrounded by large farmlands and industrial areas. This coastal environment has been affected by anthropogenic pollutants, such as polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs). The objectives of this study were to investigate the distribution of PCBs and OCPs in sediment, Manila clams, and mussels from Cheonsu Bay; the accumulation pattern of these chemicals in these bivalves in relation to seasonal changes; and the ecological risk from sediments and the risk to the Korean population from the consumption of these bivalves. The levels of ${\Sigma}PCBs$, ${\Sigma}DDT$, and ${\Sigma}HCHs$ were 69.3-109, 40.3-49.3 and 6.25-17.8 ng/g lipid in Manila clams, and 70.6-159, 38.6-102 and 9.00-13.5 ng/g lipid in Mussels. Significant seasonal variations in PCBs and OCPs concentrations were observed in the two bivalves, suggesting that the accumulation of PCBs and OCPs in these species is related to their spawning times. The dietary intake of these two bivalves and the resulting lifetime cancer risk (LCR) and non-cancer risk were calculated for the human population. The consumption of these bivalves seemed to be safe in relation to human health with negligible LCR and non-cancer risk.

• The Korean Journal of Malacology
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• v.32 no.3
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• pp.165-174
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• 2016

Feeding behaviour of the manila clam Ruditapes philippinarum was qualitatively and quantitatively characterized by comparing the contents composition in digestive tract of the clam and the phytoplankton community in surface sea water in Gomso Bay, west coast of Korea. The contents of digestive tract comprised diatoms (71.5%), dinoflagellates (13.1%), nannoplankton (6.6%), and detritus including mesozooplankton. The abundance of food organisms in digestive tract of the clam was high in winter and spring, while low in summer and autumn. But The biomass of phytoplankton in surface sea water revealed the highest value in autumn. Also, the larger the clam size increases the abundance of food organisms in digestive tract. The dominant species in digestive tract were Paralia sulcata and Navicula arenaria such as benthic diatoms and dinoflagellate cysts, whereas the dominant species in surface sea water were Chaetoceros, Skeletonema, Asterionellopsis such as pelagic diatoms in genus, cryptomonads, and P. sulcata. Analyses of digestive tract revealed that benthic diatoms especially represent an important constituent of food organisms in the malina clam and different of phytoplankton size and morphology explain preference for food selectivity.