• Animal Systematics, Evolution and Diversity
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• v.25 no.3
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• pp.325-329
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• 2009

Lepomis macrochirus from the family Centrarchidae, commonly known as Bluegill sunfish, is an introduced freshwater fish in Korea that thrives in lakes, ponds, reservoirs and rivers. Since its introduction into Korea in 1969, Lepomis macrochirus has rapidly dispersed out and increased in number almost all over the freshwater ecosystems in Korea. Consequently this species causes a severe ecological problem, threatening native fishes due to its omnivorous foraging behaviors upon fish juveniles and many freshwater invertebrates. To address population genetic structure of L. macrochirus, 74 fish samples from 10 populations were collected and compared for their mitochondrial D-loop control region. As the result we found that the genetic diversity of L. macrochirus is extremely low such as resulting only four haplotypes with a few nucleotide differences among them. Analysis of molecular variance (AMOVA) revealed that the source of population genetic variation is largely retained in the comparisons among individuals within populations, while it is relatively low with slight significance at the highest hierarchical group. This distribution pattern differs from what is expected when biogeography is under the influence of natural geographic barriers such as mountain ranges in Korea. Instead the result is accord with the influential role of random spreading events facilitated by local people for aquaculture and fishing, and subsequent dispersals since its single point of introduction into Korea.

• Korean Journal of Ichthyology
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• v.21 no.sup1
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• pp.29-37
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• 2009

The tiny fragment of freshwater body is providing home for huge biodiversity and resources for the existence of human. The competing demand for freshwater have been increased rapidly and it caused the declination of biodiversity in recent decades. Unlike the natural process of extinction in gradual progress, the current species extinction is accelerated by human activity. As a result many fish species are already extinct or alive only in captivity in the world and about fifty eight animal species are in endangered in Korea including eighteen freshwater species. Conservation of biodiversity is the process by which the prevention of loss or damage is attained, and is often associated with management of the natural environment. The practical action is classified into in-situ, or ex-situ depending on the location of the conservation effort. Recovery means the process by which the status of endangerment is improved to persist in the wild by re-introduction of species from ex-situ conservation population into nature or translocation of some population. However there are a lot of restrictions to complete it and successful results are known very rare in case. In this article the authors explore some strategies for conservation and restoration of freshwater fish species conducted in Korea for few years. The major causes are discussed in relation with the decline of freshwater fish diversity during few decades and some strategies are evaluated to advance the process of conservation. A study on the Korean bullhead, Pseudobagrus brevicorpus, is introduced as a case for ex-situ conservation and restoration in freshwater ecosystem.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.11 no.2
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• pp.49-67
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• 2006

A mesocosm, an artificial tidal flat ecosystem, was constructed outdoors to simulate in situ physical and biochemical environmental conditions of natural tidal flat as much as possible. During the experiment from February to August 2004, the study was focused on the biogeochemical variations of superficial water and porewater after introduction of freshwater into the mesocosm. The mesocosm has three experimental conditions; SW-M-T: maintaining the saline water of approximately 20 psu; FW-M-T: complete exchange of freshwater ul the mesocosm with continuous mixing of water column: FW-NM-T: complete exchange of saline water to freshwater in the mesocosm without mixing of water column. Mass extinction of benthic macrofauna appeared due to drastic decrease of porewater salinity from 20 psu to less than 10 psu between the 63th and 91st day of freshwater introduction in FW-M-T and FW-NM-T. Throughout the periods, 7/8 of bivalves and 2/3 of polychaete populations have been extinguished in the sediment. In FW-NM-T, as temperature rises, both evident decrease of DO in water column and active release of DIP from sediment were observed. ${NO_3}^-$ was removed from water column into sediment throughout the periods. Therefore extremely low ${NO_3}^-$ was found during late spring and summer. Whereas ${NH_4}^+$ exhibited only $1/2{\sim}1/8$ of ${NO_3}^-$ concentration. Unexpectedly even after mass extinction of benthic macrofauna, we were not able to find high ${NH_4}^+$. This mesocosm study suggests that when fresh water introduce to natural tidal flat, its sediment activity functions as a potential source of DIP, but a sink of ${NO_3}^-$.

• Journal of Korean Society on Water Environment
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• v.26 no.1
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• pp.148-155
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• 2010

Water quality and plankton community dynamics after the introduction of two domestic freshwater shellfishes (Unio douglasiae Griffith & Pidgeon and Cipangoplaudina chinese malleata Reeve), were monitored daily in enclosures, which constructed in the tidal zone of eutrophic agricultural reservoir (Shingu reservoir, Korea) for one week between July 31 and August 6, 2007. This biomanipulation study to improve the water quality of eutrophic lake, comprised eight enclosures (duplicate x four kinds), enclosure had no mussels (Control), stocked only with U. douglasiae at density of 60 individuals (UD), stocked only with C. chinese malleata at density of 60 individuals (CCM), and combined-stocked with 30 individuals of UD and 30 individuals of CCM (MIX), respectively. Our results clearly indicate that UD strongly decreased the concentration of chlorophyll-a and increased the water transparency, whereas CCM and MIX (included CCM) did increase algal density or decrease transparency, due perhaps to the disturbance of C. chinese malleata. Therefore, the field application of shellfish to enhance the water quality of eutrophic agricultural reservoir, should consider the grazing characteristics of biological control agents, especially active moving animals like snail.

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.614-621
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• 2010

A indigenous freshwater bivalve Unio douglasiae was introduced to compare the differences in the efficacy of algal bloom control and the appearances of mussel-mediated adverse effects between two different reservoirs such as mesotrophic (Shingu r.) and hypertrophic (Seokmun r.). We constructed the study mesocosm in the shore of each reservoir, stocked the mussel at density of $30indiv./m^3$ for 7 days, and measured daily the phytoplankton density and water quality. In mesotrophic reservoir, even though approximately 38% of suspended solids and chlorophyll-a was reduced by stocked bivalves for the first 3 days, algal density, ammonia and soluble reactive phosphorus gradually increased with increasing mussel death. In hypertrophic reservoir, mussels strongly inhibited suspended solids and chlorophyll-a by the termination of study with no increase of mussel death and nutrient, especially ammonia concentration. In both reservoirs, a strong selectivity showed mussels preferred to diatom rather than cyanobacteria and green algae without algal density and nutrient level. Our results indicate that an introduction of freshwater bivalve U. douglasiae is more strategic to improve water quality of hypertrophic than mesotrophic reservoir, but many preliminary studies on the treatment method and the selection of target water system are required.

• The Plant Pathology Journal
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• v.34 no.4
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• pp.286-296
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• 2018

Maintenance of a beneficial microbial community, especially in the rhizosphere, is indispensable for plant growth and agricultural sustainability. In this sense, plant growth-promoting rhizobacteria (PGPR) have been extensively studied for their role in plant growth promotion and disease resistance. However, the impact of introducing PGPR strains into rhizosphere microbial communities is still underexplored. We previously found that the Proteus vulgaris JBLS202 strain (JBLS202) promoted growth of Kimchi cabbage and altered the relative abundance of total bacteria and Pseudomonas spp. in the treated rhizosphere. To extend these findings, we used pyrosequencing to analyze the changes in bacterial communities in the rhizosphere of Kimchi cabbage after introduction of JBLS202. The alterations were also evaluated by taxon-specific realtime PCR (qPCR). The pyrosequencing data revealed an increase in total bacteria abundance, including specific groups such as Proteobacteria, Acidobacteria, and Actinobacteria, in the treated rhizosphere. Time-course qPCR analysis confirmed the increase in the abundance of Acidobacteria, Actinobacteria, Alphaproteobacteria, and Betaproteobacteria. Furthermore, genes involved in nitrogen cycling were upregulated by JBLS202 treatment indicating changes in ecological function of the rhizosphere soil. Overall, these results indicate that introduction of JBLS202 alters both the composition and function of the rhizosphere bacterial community, which can have direct and indirect effects on plant growth. Therefore, we propose that long-term changes in bacterial composition and community-level function need to be considered for practical use of PGPRs.

• Fisheries and Aquatic Sciences
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• v.24 no.12
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• pp.415-427
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• 2021

Wetland ecosystems act as natural freshwater purification systems, but their rich biodiversity is being threatened with the introduction of the non-native freshwater snail, Pomacea canaliculata. This study was conducted to measure the herbivory effects and growth rate of P. canaliculata on common macrophytes: Ipomoea aquatica, Ipomoea batatas, Pandanus amaryllifolius and Cucurma longa. In separate experiments, the macrophyte species were served as the snails' food as individual species and simultaneously. In the individual treatment, the growth pattern and rate were based on the snails' weight (mg/snail/day; n = 9) while the individual feeding consumption (mg/snail/day) was calculated from the leftover food. In the simultaneous treatment, the herbivory effects were evaluated as the feeding preference (%) from observations every two hours, while the total feeding consumption (mg) was calculated based on the food remaining after a 12-hour experiment (3 replicates: total n = 27). The results indicated that the growth pattern was significant for snails grazing on I. aquatica but not when other macrophyte species were eaten. The individual feeding consumption was higher when using I. aquatica than P. amaryllifolius but the growth rate for snails grazing on I. aquatica and P. amaryllifolius did not differ significantly. Meanwhile, the consumption of C. longa deterred the snails' growth rate. Although the snails consumed all the macrophytes in the individual experiment, when given the species simultaneously, the feeding preference and total feeding consumption were directed significantly more toward I. aquatica than P. amaryfollius and C. longa. We conclude that P. canaliculata is a generalist feeder given a limited choice of food but tends to show a strong feeding preference after being introduced to more food choices. These findings indicate that the introduction of P. canaliculata into wetland ecosystems may increase the herbivory effects on macrophytes, making these ecosystems vulnerable to the impact of eutrophication and biodiversity reduction.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.2
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• pp.84-90
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• 2009

We incubated marine columnar sediments at $25^{\circ}C$ for 230 days to simulate the responses of phosphorus in the sediment which was exposed to freshwater. The incubation was composed of three different treatments (FW: freshwater, FWA: freshwater under anoxic condition, and SW: seawater as a Control). Six particulate fractions of phosphorus in sediment were obtained through sequential extraction and, for comparison, phosphate concentrations in porewater and superlying water were also determined. After the incubation, evidently higher concentrations of phosphate were found in FW and FWA compared to SW. Mass extinction of living organisms in marine sediment from freshwater shock and consequent decay of their corps probably contributed such high phosphate spike in the overlying water. Higher concentrations of BD-P(lron-bound P) were found in FW compared to SW. After exposure to the freshwater, we could determine that penetration depth of dissolved oxygen in marine sediment will be deeper. A result of increases of ferrous compounds in freshwater where contained less sulfide has been obtained. Because of these phenomena, BD-P was increased in FW. On the contrary, BD-P was decreased in FWA since poor dissolved oxygen concentration. In FWA, total amount of Leachable P(SUM of LOP) has been remarkably increased through the experiment, which strongly suggested the easy conversion of the leachable P into reactive P. This experiment has shown that most of diverse P species in marine sediment were leachable under freshwater and low oxygen condition. Therefore reclamation of natural tidalfalt and consequent freshwater introduction seems to trigger the conversion of diverse P-species to leachable P in the marine sediments, which will exert high benthic load of phosphate to the overlying water.

• Journal of agricultural medicine and community health
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• v.8 no.1
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• pp.44-65
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• 1983

As a part of the epidemiological studies of clonorchiasis, this study was conducted to evaluate the current endemicity and the natural transition of the Clonorchis infection in Gimhae Gun and delta area a high endemic area in Korea in recent years, prior to the introduction of praziquantel which will eventually influence the status of the prevalence. The data obtained in this study in 1983 were evaluated for natural transition of the infection in comparison with those obtained 16 years ago in 1967 by the author(Kim, 1974). The areas of investigation, villages and schools surveyed, methods and techniques used in this study were the same as in 1967, except for the contents of the questionnaire for raw freshwater fish consumption by the local inhabitants. 1) The prevalence rate of clonorchiasis in the general population of the villages was 48.1% on the average out of a total of 484 persons examined. The average of those of the riverside-delta area was 65.2% and 43.0% in the inland area. Among the schoolchildren, the prevalence rate was 8.2% on the average out of a total of 1,423 examined. By area, the prevalence rate was 10.8% in the riverside delta area and 2.8% in the inland area. By sex, difference in the prevalence was seen only in the inhabitants of the inland area showing 52.4% in the male and 33.5% in the female. 2) In the natural transition of the infection, the prevalence rate among the inhabitants has decreased from 68.8% in 1967 to 48.1% in 1983, and in the schoolchildren from 56.4% in 1967 to 8.2% in 1983. The reduction rate was higher in the riverside-delta area than in the inland area. 3) In the prevalence rate by age, 11.9% was first seen in the 5-9 age group and the rate gradually increased up to 75.0% in the 50-59 age group. By sex, the rate was higher in the male than in the female in the 20-29 age group and over. 4) In the natural transition of the prevalence rate by age, the reduction rate of the infection during the past 16 years was greater in the younger age groups up to the 40-49 age group and reached the same level in the age group 50-59. Reduction was seen again in the age group over 60s. By sex, the reduction rate was greater in the female than in the male in the 20-29 age group and over. By area, the reduction rate was greater in the riverside delta area than in the inland area, particularly in the young age groups. 5) In the intensity of the infection among the cases, the mean egg out-put per mg feces per infected cases(EPmg) in the inhabitants was 6.3. EPmg of those of the river-side-delta area was 15.4 and that of the in-land was 2.8. On the other hand, in the schoolchildren, EPmg was 3.2, and no difference was seen between the two areas, the river-side-delta area and the inland area. 6) In the transition of the intensity of the infection by area, EPmg among the inhabitants inexplically increased from 7.8 in 1967 to 15.4 in 1983. This was probably caused by uneven specimen collection in the process of sampling the population. EPmg of the inhabitants in the inland area and those of the schoolchildren of both riverside delta and inland areas showed a similar decrease in the past 16 years. 7) The intensity of the infection by age showed a relatively low level in the 20-29 age group and below, and EPmg 5.1-9.5 was seen in the 30-39 age group and over. Sex, Epmg was 5.8 in the male and 4.7 the female. By in 8) In the transition of the intensity of the infection, EPmg decreased from 6.2 in 1967 to 5.4 in 1983. By age, in contrast to the figures of 1967 in which EPmg gradually increased with some fluctuation from 1.1 in the 0-4 age group to peak 10.5 in the 50-59 age group, in 1983 lower intensity of the infection was seen in the age group from 10-14 to 20-29 with the EPmg range of 0.6-2.7. 9) In the distribution of the clonorchiasis cases by the range of EPmg value, 43.2% of the cases were in 0.1 0.9 and 34.6% in 1.0-4.9. As a whole by cumulative percent, 44.6% of them were under 0.9 as light infection and 86.1% of them under 9.9 up to moderate infection. By sex, no difference was seen in Epmg. 10) In the transition of the distribution by the range of Epmg, the cases were distributed up to the range 80.0-99.9 in 1967 and to 60.0-79.9 in 1983. By cumulative percent, in the range of 0.1-0.9 and less, light infection, 34.3% of them were distributed in 1967 and 44.6% in 1983 with about 10% increase. In the range of 5.0-9.9 and less, up to moderate infection, 83.2% in 1967 and 86.1% in 1983 of the cases were seen, respectively. 11) The practice of raw freshwater fish consumption among the inhabitants seems to have decreased in recent years. Those who admitted to raw freshwater fish consumption in the last two years among the infected inhabitants were 59.3%, although 86.8% of them professed to have experience with raw freshwater fish consumption. 31.7% of those who have had experience of the raw freshwater fish consumption denied any further consumption in recent years. From an interview of 543 school-children, 24.1% of them admitted to an experience of raw freshwater fish consumption. However, those who have practised in the past two years comprized 17.9%. Those who denied raw freshwater fish consumption in recent years among those who had such experience were 26.0% out of 131 interviewed. The rate of raw freshwater fish consumption in both inhabitants and schoolchildren were higher in the male than in the female. On the contrary, the rate of those who did not practise in recent years among those who had experience of raw freshwater fish consumption was higher in the female than in the male. 12) The major reason for the reduction of raw freshwater fish consumption among the local inhabitants was the risk of the fluke infection. However, it has become apparent that such change of taste has resulted from water pollution impact which has affected throughout the areas of the freshwater systems in this locality since last several years. 13) In animal survey, Clonorchis infection was seen in 14.8% of 88 dogs examined and 3.7% of 27 house rats examined. It was noted that populations of dogs and cats have increased in the villages surveyed. Although the prevalence rate was lower in the present survey than those of 1967, the significance of the animals as the reservoir host has not changed. 14) Prevalence rate of Clonorchis infection by cercariae in the first intermediate host, Parafossarulus manchouricus, was 0.6% out of 517 snails examined. The infection rate was lower in comparison with 2.3% out of 2,124 examined in 1967. Moreover, sharp decreases in number and distribution of the intermediate host snails in many watershed areas of the huge freshwater systems in this locality seemed to reduce transmission of Clonorchis in connection with the intermediate host stage of its life cycle. 15) Clonorchis infection in the second intermediate fish hosts was relatively low. The mean number of Clonorchis metacercaria per fish in Pseudorasbora parva was 517 in 1983, whereas it was 1943 in 1968 through 1969. Environmental water pollution has also caused the decreased fish population density in these areas, and this has also apparently affected to the practice of raw freshwater fish consumption among the local inhabitants. 16) In conclusion, endemicity of Clonorchis infection in Gimhae Gum and delta area of the Nagdong River has sharply decreased during the past 16 years. The major cause of the regressive transition of the infection was the water pollution of the land water systems of this locality. The pollution has upset the ecosystems comprizing of the intermediate hosts of Clonorchis in many areas, and also affected to a significant extent to the discontinuance of the local inhabitants for raw freshwater fish consumption.

• Journal of agricultural medicine and community health
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• v.8 no.1
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• pp.66-80
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• 1983

As a part of the epidemiological studies of clonorchiasis in Korea, this study was conducted to evaluate the current endemicity and the natural transition of the Clonorchis infection in Goyang Gun a low endemic area in recent years, prior to the introduction of praziquantel which will eventually influence to the status of the prevalence. The data obtained in this study in 1983 were evaluated for natural transition of the infection in comparison with those obtained 16 years ago in 1967 by the author (Kim, 1974). The areas of investigation, villages and schools surveyed, methods and techniques used in this study were the same as in 1967, except for the contents of the questionnaire for raw freshwater fish consumption by the local inhabitants. 1) The current prevalence rate of Clonorchis infection among the inhabitants was 7.5% on the average out of a total of 479 persons examined. The prevalence rate was 9.0% in the riverside area and 4.2% in the inland area. Among the schoolchildren, the prevalence rate was 1.1% out of a total of 1 319 examined. By area, it was 1.4% in the riverside area and 0.7% in the inland area. By sex, the prevalence rate was 13.3% in the male and 1.3% in the female in the inhabitants and no difference was seen in the schoolchildren. 2) In the natural transition of the infection, the prevalence rate in the inhabitants has decreased from 22.5% in 1967 to 7.5% in 1983, and in the schoolchildren, from 9.5% in 1967 to 1.1% in 1983. The reduction rate was higher in the riverside area than in the inland area. 3) In the prevalence rate by age, 1.2% was seen in the 10-14 age group and gradually increased to 8.1% in the 30-39 age group and reached peak 18.1% in the 40-49 age group. By sex, in the male, the prevalence rates have increased to 31.9% and 33.3% in the 40-49 and 50-59 age groups, respectively and decreased thereafter. In the female, the prevalence rate less than 5% was seen only in between the 10-14 and 30-39 age groups. 4) In the natural transition of the prevalence rate by age, sharp decrease was seen in the male from around 50% in 1967 between 15-19 and 30-39 age groups. The generation over 40s showed less decrease. In the female, the prevalence rate has decreased from 13% in 1967 to 5% in 1983 in the middle age groups and dropped to 0% in the rest of the age groups. 5) The intensity of the infection among clonorchiasis cases by mean EPmg (number of eggs per mg feces) value was 1.4. In the inhabitants, the value was 2.0 in the riverside area and 0.4 in the inland area. While in the schoolchildren, the value was 0.2 in both riverside and inland areas. 6) In the transition of the intensity of the infection, EPmg among the inhabitants has decreased from 3.9 in 1967 to 2.0 in 1983 in the riverside area, and from 2.9 to 0.4 in the inland area. In the schoolchildren, the reduction was similar in both riverside and inland areas resulting from 1.0-1.1 in 1967 to 0.2 in 1983. 7) In the intensity of the infection by age, EPmg 3.4 was peak at the 40-49 age group and 0.2-1.0 was seen in the rest of the age groups. The mean value was 1.5 in the male and 0.6 in the female. 8) In the natural transition of the intensity of the infection, the EPmg has decreased from 2.7 in 1967 to 1.4 in 1983. By age, reduction was seen in all of the age groups, particularly in the young and the old age groups of 50s and over, except in the 40-49 age group in which reverse phenomenon was seen. By sex, it has decreased from 3.5 in 1967 to 1.5 in 1983 in the male and from 1.0 to 0.6 in the female. 9) In the distribution of the clonorchiasis cases by the range of EPmg value, 70.3% of the cases were placed in the range of 0.1-0.9 as the most and 16.2% in 1.0-4.9 as the next. With such figures, those included in the range less than 0.9 as light infection were 78.4% and under 5.0-9.9 up to moderate infection 99.3% of the cases were covered. The cases were distributed up to 20.0-39.9 in the male and to 1.0-4.9 in the female. 10) In the transition of the distribution of the clonorchiasis cases by EPmg, the highest intensity reached up to 60.0-79.9 in 1967 and to 20.0-39.9 in 1983. In the range of light infection, under 0.1-0.9, the distribution in rate was 64.5% in 1967 and 78.4% in 1983. Up to the range of moderate infection, under 5.0-9.9, 91.7% in 1967 and 97.3% in 1983 were seen respectively. 11) In a survey for raw freshwater fish consumption among the local inhabitants,78.3 of the clonorchiasis cases interviewed admitted their experience of the raw consumption. However, those who practised in the past two years were 34.8% 55.6% of those who have such experience in the past professed that they did not practise raw freshwater fish consumption in the past two years. 12) The major cause of the reduction of the raw freshwater fish consumption among the inhabitants were the wide spread water pollution in the locality. The most common reason professed for stopping raw freshwater fish consumption among the inhabitants was the risk of the fluke infection. 13) In animal survey, 3.1% of dogs were found infected with Clonorchis, decreasing from 21.6% in 1967. 14) The distribution of the first intermediate host, Parafossarulus manchouricus has greatly diminished in this locality and found only in two localized ponds. No Clonorchis infection was found from the snails examined. 15) The second intermediate freshwater fish host has been further limited by extended water pollution. No susceptible fish host could be examined. 16) In conclusion, the endemicity of Clonorchis infection in Croyang Gun, low endemic area, has significantly decreased during the past 16 years. The major cause of the regressive transition of the infection was the water pollution of the freshwater system of this locality. This has upset the ecosystems of the intermediate host of Clonorchis sinensis in many areas of waterbodies and further discouraged to a significant extent the local inhabitants from raw freshwater fish consumption.