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Choi K.-H.,Korea Institute of Coastal Ecology Inc | Lee S.-M.,Anyang University, South Korea | Lim S.-M.,Anyang University, South Korea | Walton M.,Korea Ocean Research and Development Institute | Park G.-S.,Anyang University, South Korea
Journal of Oceanography | Year: 2010

Yellow Sea tidal flats are internationally recognised for their contribution to biological diversity and yet are under enormous pressure from reclamation, pollution and overexploitation. The benthic macroinfauna community is the dominant community on these tidal flats and a reliable indicator of benthic environmental changes. We surveyed the current benthic macroinfauna community of the Ganghwa Southern Tidal Flat, the largest remaining Korean mud flat in the Yellow Sea, in order to examine changes in the environmental situation of this benthic ecosystem. The results show a significant decline in species diversity from the last survey made in 2003, and a shift in species composition with appearances of polychaetes indicative of pollution and physical disturbances and other opportunistic species becoming dominant in both density and biomass. The benthic community shift observed during the two study periods may be associated with increased nutrient pollution as well as increased physical disturbances in this area. However, we recognise the limitations of the data both in frequency and scope but believe the significant changes to the composition of the benthic fauna are sufficient to warrant concern. Observations are required to examine the extent to which these human activities induce benthic community shift in this tidal flat. © 2010 Springer Science+Business Media B.V. Source

Jeong S.-Y.,Inha University | Jeong S.-Y.,Korea Institute of Coastal Ecology Inc | Kim J.-H.,West Marine | Lee W.-O.,South Korean National Fisheries Research and Development Institute | And 2 more authors.
Fish Physiology and Biochemistry | Year: 2014

This study aimed to better understand the hydromineral regulatory response of the anadromous river pufferfish, Takifugu obscurus, to salinity changes through real-time RT-PCR. After abrupt transfer from 30 or 5 psu to 5 or 30 psu, respectively, we analyzed the mRNA expression of Na+/K+ ATPase, prolactin receptor, and aquaporin from osmoregulatory organs of the river pufferfish such as gills, kidney, and intestine. Na+/K+ ATPase showed notable changes in the gills and kidney when salinity was increased. In the gills, the expression level of Na+/K+ ATPase suddenly increased within a day after abrupt transfer from 5 to 30 psu and then slightly declined within 2 days after exposure. In the kidney, Na+/K+ ATPase has shown consistently high mRNA expression after the increase in salinity. Expression levels of the prolactin receptor gene increased when environmental salinity decreased. In the intestine, gene expression of the prolactin receptor remained high, even when salinity decreased. To the contrary, there was a steady increase or decrease in mRNA expression in the kidney in response to salinity decrease or increase, respectively. As for aquaporins, aquaporin 1 was mainly expressed in the intestine and kidney, and aquaporin 3 was mainly expressed in the gills and intestine. In the gills, increased expression of aquaporin 3 was found after transfer to lower salinity and in the intestine and kidney, a decrease in salinity followed by an abrupt decrease in aquaporin 1 and aquaporin 3. Contrastingly, the expression of these genes increased in the intestine after transfer to 30 psu. Osmoregulatory genes were expressed in diverse organs, apparently to overcome an influx or exhaust of water or ions. A superior adaptation ability of the river pufferfish to a wide range of salinities is most reasonably due to active osmoregulatory processes mediated by the genes monitored here. © 2013 Springer Science+Business Media Dordrecht. Source

Hong H.P.,Inha University | Hong H.P.,Korea Institute of Coastal Ecology Inc | Choi J.K.,Inha University
Ocean Science Journal | Year: 2015

The microlage Dunaliella salina, a major producer in salterns, is a serious problem for salt production. In this study we tried to assess if Fabrea salina can control D. salina. By parameterising numerical and functional response (growth and grazing vs prey abundance, respectively) at 90 psu and 30°C, where the ciliate is abundant and grows well, we developed a predator-prey model. The model is used to explore how change in microalga growth rate affect the dynamics, and the functional response is used in combination with field data to assess the potential impact of F. salina on D. salina. Over the 20 d simulation the ciliate controlled the prey population under all prey growth rates; although once D. salina were exhausted below the threshold level, F. salina died due to starvation, allowing the alga to increase in abundance, resulting in one or two predatorprey cycle, depending on prey growth rate. In general, the model predicted trends observed by others in the field, suggesting that it provided a good prediction of what may occur under the conditions we examined. Likewise we show that the ciliate can have a high impact on microalgal populations in the field. Finally, a literature review indicated that F. salina could be a good competitor with other protozoa and metazoan in salterns, depending on salinity and temperature, which requires further study and attention. In summary, we encourage continued studies on this unique ciliate on solar salterns and suggest that it may be useful in the bio-control of micoalgae. © 2015, Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht. Source

Hong H.-P.,Korea Institute of Coastal Ecology Inc | Hong H.-P.,Inha University | Han C.-H.,NFRDI | Yoo J.-K.,Marine Ecosystem Management Team
Ocean and Polar Research | Year: 2013

We investigated the population dynamics of Aurelia aurita in Sihwa Lake from April to October in 2009. Salinity ranged from 5.9 to 30.7 psu at the surface. Abundance of mesozooplankton ranged from 3 to 111,874 indiv. m-3. Ephyrae occurred from April to May with the peak in abundance occurring on 17 April. Maximum density of ephyrae was observed near the power transmission towers that are known to be habitats of polyps. Mortality of ephyrae was lower than in other areas because of the abundant prey concentration and the absence of predators. Young medusae occurred from April to July with the peak in abundance occurring on 8 May. Adult medusae occurred from May to July with the peak in abundance on 25 June and they disappeared before the rainy season. Planula occurred only in May and June with the peak in abundance on 25 June. Growth rates of Aurelia aurita ranged from -0.06 to 0.34 d-1, and decreased rapidly after May. The period in which adult medusa occurred was restricted, compared with those in other area in Korea (e.g., Masan Bay) and Japan (e.g., Tokyo Bay). In the period of this study, the available food was limited in June and salinity decreased to ca. 20 psu in May because of the beginning of the wet season. We assumed that the exceptionally short period of occurrence of the medusa may be a response of adults to changes in temperature, salinity or food limitation which leads to the precocious maturation of young medusa and the release of planula and that the brief occurrence of medusa was caused by an abrupt decrease in activity after the release of planula. Source

Jung S.W.,Maritime and Ocean Engineering Research Institute | Kim C.-S.,Korea Institute of Coastal Ecology Inc | Yoo J.-W.,Korea Institute of Coastal Ecology Inc | Kim Y.-O.,Maritime and Ocean Engineering Research Institute | And 2 more authors.
Ocean and Polar Research | Year: 2010

Single cell PCR analysis and light and scanning electron microscopic techniques were utilized to identify free living bivalve larvae in the coastal waters of Tae-an, on the west coast of Korea. Through DNA sequencing, venerid clam larvae were isolated and identified as Ruditapes philippinarum (99% similarity) and Meretrix lusoria (99%). Under microscopic observation, the D-veliger stage of R. philippinarum exhibited symmetrical shoulder angles and an elliptical ventral form. In contrast, M. lusoria displayed asymmetrical shoulder angles and a round ventral form in the umbonal stage. Size of the R. philippinarum larvae was 156±22 μm in length, 126±12 μm in height, 92±14 μm in width with a length: height ratio of 1.23. Meretrix lusoria was 202±44 μm in length, 161±35 μm in height, 96±38 μm in width with a length: height ratio of 1.25. Experimental results indicate that morphological and molecular characteristics provide evidence for the larval identification of these two venerid clam larvae species in nature. Source

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