• Fisheries and Aquatic Sciences
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• 제14권4호
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• pp.333-337
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• 2011

A new and a unique Brachionus rotifer was found in Hwajinpo coastal lagoon in Gangwon Province, South Korea. This Brachionus certainly originated from the wild rather than from aquaculture stations because Hwajinpo coastal lagoon has been under rigorous control as a military protected area and therefore could not have been contaminated by aquaculture stations. The new strain was identified as Brachionus rotundiformis based upon its morphological characteristics. The parthenogenetic female of this new rotifer strain typically shows characters similar to those of B. rotundiformis, such as the pot shape of the body, rounded dorsal plate compared with flattened ventral plate, elliptical mictic egg, four frontal spines, six pointed occipital spines, non-nodal foot, two toes, trophi typical of the Brachionus genus with five uncus plates resembling comb teeth, one wide symmetrical manubrium and ramus, and no stiffened spine as is seen in freshwater Brachionus rotifers. Moreover, its lorica was rather small in size compared with other common rotifer strains that serve as live-food organisms (Guam, Thai, and Bali strains). This new and unique Korean brackish rotifer, a B. rotundiformis strain, was therefore named the National Fisheries Research and Development Institute (NFRDI) $N^{\circ}1$ rotifer strain.

• Journal of Microbiology and Biotechnology
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• 제29권7호
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• pp.1104-1116
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• 2019

In this study, we investigated the potential of using sediment bioelectrochemical systems (SBESs) for in situ treatment of the water and sediment in brackish aquaculture ponds polluted with uneaten feed. An SBES integrated into a laboratory-scale tank simulating a brackish aquaculture pond was established. This test tank and the control (not containing the SBES) were fed with shrimp feed in a scheme that mimics a situation where 50% of feed is uneaten. After the SBES was inoculated with microbial sources from actual shrimp pond sediments, electricity generation was well observed from the first experimental week, indicating successful enrichment of electrochemically active bacteria in the test tank sediment. The electricity generation became steady after 3 weeks of operation, with an average current density of $2.3mA/m^2$ anode surface and an average power density of $0.05mW/m^2$ anode surface. The SBES removed 20-30% more COD of the tank water, compared to the control. After 1 year, the SBES also reduced the amount of sediment in the tank by 40% and thus could remove approximately 40% more COD and approximately 52% more nitrogen from the sediment, compared to the control. Insignificant amounts of nitrite and nitrate were detected, suggesting complete removal of nitrogen by the system. PCR-DGGE-based analyses revealed the dominant presence of Methylophilus rhizosphaerae, Desulfatitalea tepidiphila and Thiothrix eikelboomii, which have not been found in bioelectrochemical systems before, in the bacterial community in the sediment of the SBES-containing tank. The results of this research demonstrate the potential application of SBESs in helping to reduce water pollution threats, fish and shrimp disease risks, and thus farmers' losses.

• Journal of Microbiology and Biotechnology
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• 제29권10호
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• pp.1607-1623
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• 2019

Sediment bioelectrochemical systems (SBESs) can be integrated into brackish aquaculture ponds for in-situ bioremediation of the pond water and sediment. Such an in-situ system offers advantages including reduced treatment cost, reusability and simple handling. In order to realize such an application potential of the SBES, in this laboratory-scale study we investigated the effect of several controllable and uncontrollable operational factors on the in-situ bioremediation performance of a tank model of a brackish aquaculture pond, into which a SBES was integrated, in comparison with a natural degradation control model. The performance was evaluated in terms of electricity generation by the SBES, Chemical oxygen demand (COD) removal and nitrogen removal of both the tank water and the tank sediment. Real-life conditions of the operational parameters were also experimented to understand the most close-to-practice responses of the system to their changes. Predictable effects of controllable parameters including external resistance and electrode spacing, similar to those reported previously for the BESs, were shown by the results but exceptions were observed. Accordingly, while increasing the electrode spacing reduced the current densities but generally improved COD and nitrogen removal, increasing the external resistance could result in decreased COD removal but also increased nitrogen removal and decreased current densities. However, maximum electricity generation and COD removal efficiency difference of the SBES (versus the control) could be reached with an external resistance of $100{\Omega}$, not with the lowest one of $10{\Omega}$. The effects of uncontrollable parameters such as ambient temperature, salinity and pH of the pond (tank) water were rather unpredictable. Temperatures higher than $35^{\circ}C$ seemed to have more accelaration effect on natural degradation than on bioelectrochemical processes. Changing salinity seriously changed the electricity generation but did not clearly affect the bioremediation performance of the SBES, although at 2.5% salinity the SBES displayed a significantly more efficient removal of nitrogen in the water, compared to the control. Variation of pH to practically extreme levels (5.5 and 8.8) led to increased electricity generations but poorer performances of the SBES (vs. the control) in removing COD and nitrogen. Altogether, the results suggest some distinct responses of the SBES under brackish conditions and imply that COD removal and nitrogen removal in the system are not completely linked to bioelectrochemical processes but electrochemically enriched bacteria can still perform non-bioelectrochemical COD and nitrogen removals more efficiently than natural ones. The results confirm the application potential of the SBES in brackish aquaculture bioremediation and help propose efficient practices to warrant the success of such application in real-life scenarios.

• Parasites, Hosts and Diseases
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• 제46권2호
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• pp.77-82
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• 2008

Fishborne zoonotic metacercariae have not been reported from brackish water and marine fish from Vietnam waters although these parasites are common in the country's freshwater fish. Both wild-caught and cultured grouper (Epinephelus coioides and Epinephelus bleekeri), and mullet (Mugil cephalus) from brackish and marine waters located in Khanh Hoa province in central coastal Vietnam were examined, and found positive for zoonotic trematode metacercariae. From grouper, Heterophyopsis continua and Procerovum varium were recovered. The prevalence of H. continua ranged from 2.0 to 6.0% and that for P. varium ranged from 11.6 to 15.8%. Mullet were infected with Pygidiopsis summa and H. continua; both of these species are new records for Vietnam. The prevalence of P. summa in mullet was generally high, ranging from 17.6 to 75.5%, and was significantly higher than the prevalence of H. continua (2.5 to 32.4%). There were no significant differences in the prevalence of metacercariae between grouper from natural or cultured habitats, indicating that the highest risk of infection occurs in the wild-caught state prior to their placement in culture. Further, there was no difference in metacercarial prevalence between the 2 species of grouper. Infected wild-caught seed were only observed from January to October. Monthly variation in prevalence suggests seasonal variation in mullet infections occurs in this region with the highest transmission taking place from October to December. Basic investigations on the ecology and epidemiology of these intestinal flukes need to be carried out to determine their significance as a public health problem and the aspects of their biology that may be vulnerable to control interventions.

• 한국수산과학회지
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• 제42권4호
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• pp.335-343
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• 2009

Antimicrobial resistance patterns of Vibrio species isolated from brackish water in Geoje, Tongyeong and Goseong, Gyeongsangnamdo province into which streams, sewage and leachate all flowed. Only 19 strains (10.7%) of 177 V. parahaemolyticus were susceptible to 15 antimicrobials. 146 strains (69.5%) proved resistant against more than one antimicrobial and 12 strains (6.8%) were multi-drug resistant. The resistance rate of 152 strains were 85.9% against AM and 26.6% against RA, 16.4% against AN, 13.6% against Sand 13.0% against TMP. 86 strains of 129 V. cholerae non-O1 (66.7%) were susceptible to antimicrobials and 31 strains (24.0%) were resistant to more than one antimicrobial and 12 strains (9.3%) were multi-drug resistant. The antimicrobial resistance rate of 129 strains against 15 antimicrobials, with the exception of C, CIP, E and GM, i.e. 11 antimicrobials, was 0.7-16.2%, 16.2% of 129 strains proved resistant against RA and 13.9% against AM, 9.3% against TMP, 7.7% against SXT and 6.9% against TE. 19 of 49 strains of V. mimicus (38.8%) were susceptible to antimicrobials and 31 strains (61.2%) were resistant against more than one antimicrobial; none of the strains were multi-drug resistant. 15 strains of V. mimicus were resistant against only RA, AmC and TE. The resistance rate was 59.2% against RA (highest) 4.1% against AmC and 2.0% against TE.

• 한국수산과학회지
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• 제40권1호
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• pp.8-15
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• 2007

This study selected the optimal microalgal species for mass culture of a brackish water copepod Paracyclopina nana. Fifteen microalgal species were tested to examine nauplius production and the survival and maturation of brood females. Total and daily nauplius production were highest in P. nana fed Tetraselmis suecica followed Isochrysis galbana, Dunaliella tertiolecta, and Phaeodactylum tricornutum. With a monospecific microalgal diet, the total density was highest with P. nana fed I. galbana, at 63.3 inds./mL. With a mixed microalgal diet, the total density of P. nana fed T. suecica+I. galbana was higher than that fed other mixed diets, although there was no difference between a monospecific diet of I. galbana and a mixed diet of T. suecica+I. galbana. Examining the fatty acid composition of P. nana, the eicosapentaenoic acid (EPA) was highest in P. nana fed T. suecica at 5.4% while the docosahexaenoic acid (DHA) content was highest I. galbana diet at 31.9%. Although no DHA was detected in T. suecica, P. nana fed this microalgal species had a high DHA composition of 24.3%. We suggest that the optimal microalgal species for the mass culture of P. nana is T. suecica which is easy to culture on masse and has a high linolenic acid content.

• Fisheries and Aquatic Sciences
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• 제26권8호
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• pp.470-481
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• 2023

Algal overgrowth in shrimp culture ponds can affect the quality of the aquatic environment, thereby adversely affecting the shrimp and causing economic losses. The objective of this study was to evaluate the variation in phytoplankton composition in intensive shrimp ponds in Bac Lieu province, Vietnam. Phytoplankton samples were collected in three black tiger shrimp (Penaeus monodon) ponds and three whiteleg shrimp (Litopenaeus vannamei) ponds. The collected data were analyzed using SPSS and canonical correlation analysis softwares. In total, 75 species of phytoplankton were recorded in black tiger shrimp ponds and 64 species in whiteleg shrimp ponds. Diatoms had the highest species diversity with 29-30 species (39%-47%), followed by green algae with 9-19 species (14%-25%); species numbers of other phyla varied from 5-12 (8%-16%). The total number of phytoplankton species throughout the study varied from 34-50 species. Algal density was relatively high and ranged from 497,091-2,229,500 ind./L and 1,301,134-2,237,758 ind./L in black tiger shrimp and whiteleg shrimp ponds, respectively. The diatom density tended to increase during the final stage of the production cycle in black tiger shrimp ponds. Blue-green algae and dinoflagellates also increased in abundance at the end of the cycle, which can affect shrimp growth. Diatoms were significantly positively correlated with pH, salinity, total ammonia nitrogen, and nitrate (NO₃^-) concentrations (p < 0.05). Blue-green algae and dinoflagellates were positively correlated with salinity, phosphate (PO₄^3-), and NO₃^-. Algal species diversity was lower in the whiteleg shrimp ponds than in the black tiger shrimp ponds. Several dominant algal genera were recorded in the shrimp ponds, including Nannochloropsis, Gyrosigma, Chaetoceros, Alexandrium, and Microcystis. The results of this study provide basic data for further investigations, and they contribute to the management of algae in brackish-water shrimp ponds.

• 한국양식학회지
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• 제19권4호
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• pp.310-314
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• 2006

본 연구는 기수산 cyclopoid 요각류인 Paracyclopina nana의 먹이 종류와 농도에 따른 섭식률을 조사하였다. 먹이 공급 24 시간 후 먹이의 종류와 농도에 따른 P. nana의 장내용물 함량과 섭취된 먹이의 양을 색소분석 방법으로 조사하였다. T. suecica는 30 ng chl a/ml, I. galbana와 D. tertiolecta는 40 ng chl a/ml, P. tricornutum는 45 ng chl a/ml 농도로 공급하였을 때 섭취된 먹이의 양과 P. nana의 장내용물 함량이 가장 높았다. T. suecica, I. galbana, P. tricornutum, 그리고 D. tertiolecta에 대한 P. nana 성체 1 개체의 시간당 최대 섭식률은 각 미세조류의 공급 농도가 각각 39.3, 44.7, 44.5와 49.8 ng chl a/ml일 때 각각 0.63, 0.60, 0.41 및 0.52 ng chl a로 나타났다. 따라서 P. nana의 대량배양시 가장 적합한 먹이생물은 공급 농도가 낮으면서도 섭식률이 가장 높은 T. suecica이며, 성체 1 개체당 1일 먹이 공급량은 약 $25{\sim}39$ ng chl a (약 $10{\sim}15{\times}10^4$ cells)가 가장 경제적일 것으로 판단된다.

• Fisheries and Aquatic Sciences
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• 제18권1호
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• pp.45-50
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• 2015

A 10-day trial was conducted to evaluate the salinity tolerance and hematological responses of juvenile ship sturgeon Acipenser nudiventris under different salinity levels. A total of 240 fish averaging $6.2{\pm}0.13g$ (mean${\pm}$SD) were randomly distributed into 12 tanks in groups of 20, and each tank was then randomly assigned to one of three replicates of four different salinities at 0, 4, 8 and 12‰. At the end of 10 days of experimental period, plasma protein value of fish exposed to 0‰ and 4‰ salinities was significantly higher than those of fish exposed to 8‰ and 12‰ salinities (P < 0.05). Significantly higher values for plasma cortisol and glucose were obtained in fish exposed to 12‰ salinity compared to the fish exposed to 0‰ and 4‰ salinities (P < 0.05). Plasma potassium and sodium values increased significantly by increment of salinity levels (P < 0.05). Therefore, these results indicated that in natural environments, juvenile ship sturgeon, A. nudiventris in migratory populations could be able to migrate and adjust successfully into brackish water with a salinity of up to 8‰ without any short-term hematological stress responses.

• Fisheries and Aquatic Sciences
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• 제15권3호
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• pp.221-231
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• 2012

The marine medaka Oryzias dancena choriogenin H gene (odChgH) and its mRNA expression during estradiol-$17{\beta}$ (E2) exposure were characterized. At the amino acid level, the choriogenin H protein is predicted to possess the conserved repetitive N-terminal region, as well as zona pellucida (ZP) and Trefoil factor family (TFF) domains. At the genomic level, odChgH has an eight-exon organization with a distribution pattern of transcription factor binding sites in the 5'-upstream region, which is commonly found in other estrogen-responsive genes. The tissue distribution pattern of odChgH mRNA was found to be gender-specific, whereby females showed a higher expression level and wider tissue distribution than did males. During embryonic development, odChgH mRNA was robustly detected from the stage of visceral blood vessel formation. Experimental E2 exposure of males resulted in odChgH mRNA being induced not only in the liver, but also in other several tissues. The E2-mediated induction was fairly dose-dependent. The basal expression levels of hepatic odChgH mRNA were lower in males that were acclimated to 30 ppt salinity than in those acclimated to 0 or 15 ppt salinity. In contrast, the inducibility of odChgH mRNA during E2 exposure was greater in seawater-acclimated fish than in brackish water- or freshwater-acclimated fish.