• Korean Journal of Ecology and Environment
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• v.38 no.3 s.113
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• pp.412-419
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• 2005

The dynamics of zooplankton community and its relationship with environments were studied at the middle stretch (Waekwan, RK; river kilometer; above 175 km from the estuary dam) of large regulated river, Nakdong River from 1998 to 2002. There were distinct inter-annual variations and seasonal changes in total zooplankton abundance in the study site (ANOVA, p<0.01), displaying similar pattern in three years from 1999 to 2001 except 1998 and 2002. The annual average rotifers abundance during the study period was 43${\pm}76 ind. $L^{-1}$ (mean${\pm}$s.d., n = 118), followed by adult copepodids (1.6${\pm}$4.8 ind. $L^{-1}$), and small cladocerans (0.4${\pm}$1.2 ind. $L^{-1}$). Among the rotifers, Brachionus spp. Polyarthra spp., Colurella spp., Keratella spp.·, and Trichocerca spp. were the most common taxa. These species occupied more than 80% of the total rotifer abundance throughout the study period. Total zooplankton abundance rapidly increased in spring and fall and remained low throughout the winter. During summer, zooplankton dynamics seemed to be largely affected by hydrological parameters. Overall, rather the external factors (hydrological factors of the river) than internal factors (food condition for zooplankton such as phytoplankton biomass) appear to be responsible for changes in zooplankton dynamics in the middle stretch of the river.

• The Korean Journal of Malacology
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• v.24 no.3
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• pp.161-166
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• 2008

Samples were collected monthly from coastal water around Tongyeong and Sacheon in Gyeongsangnam-do, Korea, using traps. A total of 748 Octopus vulgaris were sampled from February 2007 to January 2008. Monthly changes of maturity stages and sex ratio of the common octopus were observed. Mean biomass (total wet weight) of the female specimens ranged from 129.8 to 3,381.4 g and that of the male specimens ranged from 128.6 and 2,378.4 g. The spawning periods were May to June and September. The fecundity ranged from 5,715 eggs at 252.0 g to 240,990 eggs at 3,381.4 g of total wet weight. The relationship between total wet weight (TW) and fecundity (F) was F = 26.539 $TW^{1.1548}$ ($r^2=0.8199$) and fecundity increased with total wet weight. Sex ratio was not significantly different from the 1:1 (p > 0.05).

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.2
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• pp.76-86
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• 2012

Macrozoobenthos were collected from 24 sites using small grab ($0.05m^2$) in order to see the spatial distribution of them at Sueocheon stream at the northern part of Gwangyang Bay during summer season when the maximum ecological processes are occurring. A total of 44 species of macrozoobenthos occurred, and their mean density was $789individuals/m^2$. Mollusks was the dominant faunal group accounted for 43.1% and 86.8% of the whole community density and biomass, respectively. Top five dominant species were a molluscan, Corbicula japonica (40.7%), two polychaete worms, Neanthes japonica (19.3%) and Heteromastus filiformis( 8.1%), and two crustaceans, Paranthura japonica (6.9%) and Jaeropsis sp. (6.9%). Species diversity index was very low with mean value of 1.12 and maximum value was recorded at the river mouth. At the upper stream, a brackish water species such as Corbicula japonica showed their maximum population density. The overall distribution of stream macrobenthos showed a rather simple pattern along with salinity and grain size gradients with few brackish water species occurring at coarse sediments in the stream but more diverse faunas inhabiting fine sediments in the river mouth.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.1
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• pp.97-106
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• 1996

Macroalgal community was analysed from December 1993 to October 1994 in Yonggwang vicinity, western coast of Korea. A total 51 species (12 green, 11 brown and 29 red algae) of marine algae were identified. Among four localities, the number of species observed was the highest as 34 species at Shimwon and the least as 31 species at Sunchanggum and Gamakdo. Seasonally, the number of species observed was the highest as 42 species in winter and the least as 18 species in summer. The species showing relatively high important value were Enteromorpha compressa, Sargassum thunbergii, Corallina pilulifera and Carpopeltis affinis, which were all common to four investigated localities. Seasonal and regional fluctuations of mean biomass was $66.0\~820.0\;g-wet\;wt/m^2$ at Hyanghado, $248.3\~886.3\;g-wet\;wt/m^2$ at Sunchanggum, $154.5\~510.2\;g-wet\;wt/m^2$ at Gamakdo and $85.0\~451.9\;g-wet\;wt/m^2$ at Shimwon, respectively. The flora investigated could be classified into six functional groups such as coarsely branched form $(41.2\%)$, sheet form $(25.5\%)$, filamentous form $(19.6\%)$, thick leathery $(7.8\%)$, crustous form $(3.9\%)$ and jointed calcarious form algae $(2.0\%)$. At the effluent area of the nuclear power plants, the algal composition of functional groups may affect species composition due to thermal pollution.

• 한국해양학회지
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• v.28 no.1
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• pp.52-68
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• 1993

Effects of iron and/or chelator addition on primary production in the equatorial Upwelling system were studied during the TOGA(Tropical oceans and Global Atmosphere) and EPOCS (Equatorial Pacific ocean Climate Studies) cruises in June and November-December of 1989. Changes in the phytoplankton biomass and the degree of iron stress were estimated using the changes in vivo fluorescence before and after the addition of DCMU, which is an inhibitor of photosynthetic electron transposer system. Nitrate uptake was measured using /SUP 45/N labeled KNO$_3$ to estimate the new production. When samples were taken from the Upwelling area where nitrate concentration was higher than 5 uM, there were significant differences between the control and cheated iron treatments in vivo fluorescence and in nitrate uptake capacity. However, CFC (Cellular fluorescence capacity) did not show any significant difference between the control and treatments until nutrient limitation becomes severse and cells become shifted-down. Outside of the Upwelling area where surface nitrate concentration was low (below 0.5 uM), there was no significant difference between the control and treatments in vivo fluorescence and CFC. It is evident that primary and new production in the equatorial Pacific Upwelling region are limited by the availability of iron. However, the physiology of phytoplankton indigenous to this region does not appear to be iron stressed judging from CFC values.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.2
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• pp.141-145
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• 2000

The daily fluctuations of occurrence rate and standing stock of zooplankton, the relationship between dry and wet weights of gelatinous zooplankton, and the size distributions of body length and body weight of zooplankton were investigated in the sea around Cheju Island from September 1996 to August 1997. Mean ratios of wet to dry weights were 66.46 (raging from 47.05 to 84.64) in the gelatinous zooplankton and 10.89 (raging 9.21 to 14.85) in the non-gelatinous zooplankton which consisted of crustaceans such as copepods, decapods, mysids, and ostracods etc. Rarios of gelatinous zooplankton to non-gelatinous zooplankton (G/NG) in wet weight was 0.99 (0.28-2.30), indicating high occurrence rate of gelatinous in the study area. The seasonal and diel fluctuations of the gelatinous zooplankton were very large, and G/NG ratios greatly varied with seasons and dat/night cycles. The size distributions of body length of zooplankton (250-500 urn: 35.5% in maximum), and wet (0.1-0.2 mg: 34.4%) and dry weights (0.025-0.05 mg: 44.8%) showed much difference depending composition of the zooplankton groups. These results show that quantitative estimations of zooplankton produc- tivity only based on wet weight should be corrected to better understand and evaluate marine resources in Korean waters.

• 한국해양학회지
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• v.21 no.2
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• pp.110-117
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• 1986

In southeastern sea of Korea, ammonium excretion rates of mixed macrozooplankton population ranged from 0.90 to 2.32$\mu\textrm{g}$ atoms NH$\_$4/-Nm$\^$-3/h$\^$-1/ and zooplankton excretion contributed from 3 to 15% of total nitrogen requirement by phytoplankton. Wet weight specific ex cretion rate was averaged to be 3.45$\mu\textrm{g}$ atoms NH$\_$4/-Ng$\^$-1/wet weight h$\^$-1/. Zooplankton biomass in wet weight and protein tended to increase to ward outer outer shelf. GDH assay of macrozooplankton demonstrated a typical Michaelis-Mentenkinetics with 5.1mM of half saturation constant(Km). Protein specific GDH activity in the present study ranged from 1.5 to 3.2$\mu\textrm{g}$ atoms NH $\_$4/-N mg$\^$-1/protein h$\^$-1/. Higher protein specific GDH activity in the outer shelf implies that zooplankters in the outer shelf were more active in nitrogen metabolism grazing higher primary production in the outer shelf. In the present study, averaged GDH/excretion ratio was 18.8${\pm}$2.6(n=6)showing high correlation between zooplankton GDH activity and direct ammonium excretion rate by zooplankton. GDH assay can be extremely useful in the future study for the ammonium regeneration by different size zooplankton fraction in various marine environments.

• Journal of Aquaculture
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• v.13 no.1
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• pp.87-99
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• 2000

Field survey on the variational characteristics of water quality and chlorophyll a concentraion were carried out at the 25 stations for four seasons in Kogum-sudo(Straits) southern coast of Korean Peninsula from Feburuary to October in 1993. We made an analysis on biological factor as chlorophyll a concentraion as well as physicio-chemical factors such as water temperature salinity sigma-t transparency dissolved oxygen(DO) chemical oxygen demand(COD) nutrients (ammonia, nitrite, nitrate, phosphate, and silicate) N/P ratio and suspended solid(SS). The waters in the Kogum-sudo were not stratified due to the tidal mixing. And the high productivity in photic layer were supported by high nutrients concentration from bottom waters. The high concen-trations of suspended solid in straits had a bad influence upon marine biology of nature and cultivations. In Kogum-sudo had a sufficient nutrients for primary productivity during a year. Especially phosphate and inorganic nitrogen were high the other side silicate was very low. The source of nutrients supply depend on rather mineralization of organic matters and input of seawater from outside than input of freshwaters from lands. Phytoplankton biomass as measured by chlorphyll a concentratiion was very high all the year round and it was controlled by the combination o f several environmental factors especially of phosphate in summer and dissolved nitrogen in other seasons.

• Journal of Life Science
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• v.23 no.3
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• pp.368-376
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• 2013

The optimal condition for Morus alba cv was an MS culture medium at $27^{\circ}C$ for 20 days. Cheongmoknosang callus showed inhibitory activity against Helicobacter pylori at 1.05 g of wet weight of the cultured callus. The callus formation of Morus alba cv. Cheongmoknosang was influenced by naphthalene acetic acid (NAA), 2,4-dichlorophenoxy acetic acid (2,4-D), 6-benzylaminopurine (BA) and kinetin at concentrations of 2 mg/l. The growth rate of callus was higher than it was when these hormones were mixed with a single hormone. Thus, the optimal condition for direct callogenesis was to incubate with mixture (2,4-D/NAA) of 2 mg/l concentration at $27^{\circ}C$ for 20 days. Moreover, the optimal culture condition of the biomass in the mass production of inhibitory compounds against Helicobacter pylori from Morus alba cv. Cheongmoknosang callus was to incubate in an MS broth (each concentration 1 mg/l of 2,4-D and BA). When Morus alba cv. Cheongmoknosang callus were incubated for 20 days in a bioreactor, Helicobacter pylori inhibition of callus extracts was the highest at a clear zone of 16 mm.

• Journal of Microbiology and Biotechnology
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• v.30 no.11
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• pp.1659-1669
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• 2020

1,3-α-3,6-anhydro-L-galactosidase (α-neoagarooligosaccharide hydrolase) catalyzes the last step of agar degradation by hydrolyzing neoagarobiose into monomers, D-galactose, and 3,6-anhydro-L-galactose, which is important for the bioindustrial application of algal biomass. Ahg943, from the agarolytic marine bacterium Gayadomonas joobiniege G7, is composed of 423 amino acids (47.96 kDa), including a 22-amino acid signal peptide. It was found to have 67% identity with the α-neoagarooligosaccharide hydrolase ZgAhgA, from Zobellia galactanivorans, but low identity (< 40%) with the other α-neoagarooligosaccharide hydrolases reported. The recombinant Ahg943 (rAhg943, 47.89 kDa), purified from Escherichia coli, was estimated to be a monomer upon gel filtration chromatography, making it quite distinct from other α-neoagarooligosaccharide hydrolases. The rAhg943 hydrolyzed neoagarobiose, neoagarotetraose, and neoagarohexaose into D-galactose, neoagarotriose, and neoagaropentaose, respectively, with a common product, 3,6-anhydro-L-galactose, indicating that it is an exo-acting α-neoagarooligosaccharide hydrolase that releases 3,6-anhydro-L-galactose by hydrolyzing α-1,3 glycosidic bonds from the nonreducing ends of neoagarooligosaccharides. The optimum pH and temperature of Ahg943 activity were 6.0 and 20℃, respectively. In particular, rAhg943 could maintain enzyme activity at 10℃ (71% of the maximum). Complete inhibition of rAhg943 activity by 0.5 mM EDTA was restored and even, remarkably, enhanced by Ca²⁺ ions. rAhg943 activity was at maximum at 0.5 M NaCl and maintained above 73% of the maximum at 3M NaCl. K_m and V_max of rAhg943 toward neoagarobiose were 9.7 mg/ml and 250 μM/min (3 U/mg), respectively. Therefore, Ahg943 is a unique α-neoagarooligosaccharide hydrolase that has cold- and high-salt-adapted features, and possibly exists as a monomer.