• Journal of the korean society of oceanography
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• 제38권2호
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• pp.68-79
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• 2003

Although seagrasses are relatively abundant, few studies have been conducted on seagrass physiology and ecology in Korea. Zostera marina is the most abundant seagrass species, widely distributed throughout all coastal areas of the Korean peninsula. To examine seasonal dynamics and spatial variations of eelgrass, Zostera marina distributed on the coast of Korea, morphological characteristics, biomass, tissue nutrient constituents, leaf productivity and environmental factors were monitored monthly from the eelgrass beds in Kabae Bay and Kosung Bay on the south coast of the Korean peninsula from June 2001 to June 2002. Eelgrass density, biomass, morphological characteristics, leaf productivities, and tissue nutrient constituents exhibited clear seasonal variations, and these seasonal trends reflected seasonal changes in water temperature. Eelgrass shoot density and biomass at Kabae Bay site showed more obvious seasonal trends than Kosung Bay. No strong seasonality in Kosung Bay site appeared to be caused by high water temperature ($>30{\circ}C$) during summer months at this site. Despite differences in nutrient availabilities between two study sites, eelgrass biomass and leaf productivities were not significantly different between study sites, and this lack of spatial variations implies that the ambient nutrient availabilities at the present study sites are in excess of seagrass nutrient demand. Eelgrass tissue N content and sediment pore water DIN concentrations exhibited reverse relationship at the present study. This reverse relationship suggests in situ nutrient concentrations are not good indicator of nutrient availabilities, and regeneration and turnover rates of sediment nutrients are also important factors to determine nutrient availabilities at the site.

• Journal of the korean society of oceanography
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• 제39권3호
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• pp.186-196
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• 2004

Since seagrasses are highly productive and provide a source of organic carbon for a wide variety of marine organisms in coastal and estuarine ecosystem, accurate assessment of seagrass production is critical to understand the functions and values of seagrasses in these ecosystems. Zieman's leaf marking technique has been mostly used to estimate seagrass leaf production rates. However, inherent problems on the traditional leaf marking technique have been discussed by the several researchers, and these problems can cause underestimation of seagrass production. To develop an accurate and reliable assessing method for seagrass production, production rates of eelgrass, Zostera marina in three bay systems on the south coast of the Korean peninsula were estimated using the conventional leaf marking technique and the plastochrone method. The plastochrone method has been recently suggested as an effective method for reliable assessments of seagrass production. In the present study, leaf production rates estimated by the plastochrone method were significantly higher than the rates derived from the traditional leaf marking technique. Annual eelgrass leaf production assessed using the leaf marking technique was about 65 to 89% of the estimated production using the plastochrone method. The differences in annual productions between assessment techniques imply that the conventional leaf marking technique significantly underestimated eelgrass leaf production. Total eelgrass productions estimated using the plastochrone method in the present study sites were about 600 to 806 g DW $m^{-2} y^{-l}$, and below-ground production accounted for about 20 to 23% of the total production. The plastochrone method was suggested to be an effective and accurate assessing method for eelgrass production.

• KSBB Journal
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• 제27권4호
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• pp.227-231
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• 2012

Whole plants of Zostera asiatica were extracted twice with acetone/methylene chloride (A+M) and methanol (MeOH) in turn. The combined crude extracts were evaporated in vacuo and then the residue was partitioned between water and methylene chloride. The aqueous layer was fractionated into $H_2O$ and n-butanol and then the organic layer was also fractionated into 85% aq. MeOH and n-hexane, successively. The crude extracts and their solvent fractions were evaluated for their inhibitory effect on growth of human cancer cells AGS, HT-29, MCF-7, and HT-1080 cells by MTT reduction assay. Among samples tested, 85% aq. MeOH and n-hexane fractions showed strong cytotoxic effect against AGS, HT-29, and MCF-7 cells. On the other hand, for HT-1080 cell, 85% aq. MeOH fraction exhibited the strongest cytotoxic effect.

• 한국해양바이오학회지
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• 제11권2호
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• pp.62-70
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• 2019

We investigated the variation of morphological features, density, biomass and characteristics of reproductive shoot on Zostera marina. This species was monthly monitored and collected during a year in Tongyeong (from January 2016 to December 2016). Morphological features, biomass and density showed significantly seasonal variation (p<0.001). Dimensions of Z. marina were highest in spring and early summer but lowest in winter. Biomass and leaf density of Z. marina showed highest value in May (4,700.5 g w·wt m^-2) and June (858.0 leaves m^-2) respectively and lowest value in November (515.9 g w·wt m^-2 and 312.0 leaves m^-2). Reproductive shoot was monitored from April (13℃) to June (21℃) and grew up to ca. 200 cm. Spathe length, spadix weight, numbers and weight of fruit showed significantly different on monthly. None mature flowers were monitored in April but matured flowers, fruits were founded in May and seed releasing were occurred in June.

• ALGAE
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• 제19권1호
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• pp.39-47
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• 2004

Production dynamics of eelgrass, Zostera marina was examined in Jindong Bay on the south of the Korea peninsula. Eelgrass leaf productivities and environmental factors such as underwater photon flux density, water temperature, and nutrient availabilities in the water column and sediments were monitored from March 2002 to December 2003. While water temperature exhibited a distinct seasonal trend, underwater irradiance and nutrient availabilities exhibited high degree of fluctuation, and did not show a seasonal trend throughout the experimental periods. Eelgrass leaf elongation and production rates showed significant seasonal variations. Leaf productivity was highest in May (30.0 mg dry wt sht$^{-1}$ d$^{-1}$ or 3.7g dry wt m$^{-2}$d$^{-1}$) and lowest in November (3.2 mg dry wt sht$^{-1}$ d$^{-1}$ or 0.12 g dry wt m $^{-2}$ d$^{-1}$). Eelgrass leaf productivities did not show a strong correlation with underwater irradiance or environmental nutrient availabilities. The production rates, however, were positively correlated with water temperature during spring periods, and were correlated negatively at high water temperature exceeded 20℃ during summer months. While relative growth rates were highest in spring and lowest in high water temperature periods, plastochrone interval was longest during summer and shortest during spring. These results imply that seasonal growth dynamics of eelgrass, Z. marina was mainly controlled by water temperature.

• ALGAE
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• 제19권2호
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• pp.129-137
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• 2004

Since cultural eutrophication has the detrimental effects on estuarine and coastal ecosystems, recognition of early stage of nutrient over-enrichment is critical for effective managements of the ecosystems. Since released nutrients into coastal ecosystems are diluted and dissipated through tidal action and rapid uptakes by marine plants, monitoring of in situ nutrient concentrations may not be useful for detecting early eutrophication on coastal and estuarine ecosystems. To develop an effective indicator of cultural eutrophication using marine plants, tissue N content and area normalized leaf mass of eelgrass, Zostera marina were examined in Kosung Bay and Koje Bay on the south coast of Korea from June 2001 to April 2003. Eelgrass tissue N content exhibited obvious seasonal variations. Leaf N content was highest during winter and early spring and lowest during summer. Eelgrass tissue N content was higher at Kosung Bay site, which has higher sediment organic content, than at Koje Bay site. Area normalized leaf mass showed reverse trend of leaf N content, and consequently, eelgrass leaf N content and leaf mass exhibited strong negative correlation at both study sites. The results of the present study suggested that the ratio of eelgrass leaf N content to area normalized leaf mass can be applied to assess environmental nitrogen conditions on the coastal and estuarine ecosystems.

• ALGAE
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• 제20권2호
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• pp.157-166
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• 2005

Uptake kinetics of Cd and Zn by leaves and rhizome of the seagrass Zostera marina were examined in controlled laboratory radiotracer experiments. Subsequently, acute toxicity of Cd, Cu and TBT on photosynthetic quantum yield (ΔF/Fm’ of Z. marina were determined, and the differential sensitivities of rapid light curve (RLC) to those harmful substances were also compared. All measurements on photosynthetic activity were determined by chlorophyll a fluorescence method using pulse amplitude modulation (PAM). Metal uptake by Z. marina was saturated with increasing exposure time in leaves and rhizomes. Uptake of Zn by Z. marina was faster than that of Cd. Metal uptake rates in Z. marina decreased with the increase of dissolved metal concentrations and also with the increase of biomass. The adverse effect of TBT on effective quantum yield was stronger than other pollutants. Average acute toxicity on the RLC of the seagrass exposed to TBT and two heavy metals (Cd and Cu) was going to decrease as follows: TBT > Cd > Cu. Our preliminary results in this study suggested that Z. marina potentially can be used as a biomonitor of harmful substances contamination in coastal waters.

• Ocean and Polar Research
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• 제24권1호
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• pp.55-61
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• 2002

Eelgrass, Zostera marina L. widely spreads throughout all the coastal areas of the Korean Peninsula. However, some previously reported eelgrass populations disappeared. The disappearance was probably caused by anthropogenic disturbance such as reclamation and pollutant or exceeded nutrient release. Eelgrass beds occurred from the intertidal to the subtidal zone, mainly in lagoon, estuaries, ports, barrier reef and bays. Eelgrass beds were also found at the intertidal mud and sand flats, subtidal mud and sandbank in more exposed areas. Habitat characteristics of eelgrass beds distributed on the coasts of the Korean Peninsula varied among coast areas. Eelgrass distributed constantly throughout the southern coast of Korea, while the distribution was limited at lagoon, bay, port, or barrier reef on the eastern coast, because of steep water depth and high wave energy in that coast. On the western coast, eelgrass mainly appeared at the intertidal and subtidal zones in islands. Sediment characteristics of the Z. marina beds varied with locality, tidal current and water motion. Sediments of Z. marina beds were composed of sand, muddy sand, sandy mud and mud. Mean grain size ranged from 1.5 to 4.1 phi.

• ALGAE
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• 제22권2호
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• pp.141-146
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• 2007

Seagrass bed is an important component in coastal and estuarine ecosystems, providing food and habitats to a wide variety of marine organisms. Recently, seagrass coverage has declined significantly due to anthropogenic impacts such as cultural eutrophication and reclamation, and thus efforts are under way to prevent further losses and restore disturbed seagrass habitats worldwide. Seagrass transplantation techniques for habitat restoration include vegetative and seed-based methods. Seagrass seeds can be collected easily, and sowing seeds is an economically effective method for large-scale restoration. However, large numbers of seed can be lost by seed predation and physical disturbance in the planting areas. In the present study, Zostera marina seeds were coated with loess to reduce seed loss by predation and sweeping away by the water currents, and germination rates of coated seeds and seedling growth were examined to assess the feasibility of the seed-coating method for large-scale restoration. Germination rate of the coated seeds with loess was significantly higher than that of the uncoated seeds. Additionally, seedling growths were not significantly different between the coated and the uncoated seeds. These results suggest that coating of eelgrass seeds with loess enhances success of seed germintion with no harmful effects on seedling growth. Therefore, the seed coating method using loess may be an effective and applicable seedbased transplanting technique for large-scale restoration.

• ALGAE
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• 제25권1호
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• pp.27-35
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• 2010

Marked declines in seagrass meadows are increasingly being reported from coasts around Korea and many regions of the world. The transplantation of seagrasses has been attempted to mitigate and control their degradation from a range of anthropogenic factors. In this study, Zostera marina shoots, which were collected from a donor bed in Koje Bay, were transplanted in Jindong Bay in December 2004. In 2008, a comparative investigation of shoot morphology, growth, and reproduction strategy of Z. marina was carried out between the donor and transplant sites to assess their adaptation success. Shoot height, individual shoot weight, and leaf productivity at the transplant site were significantly greater than those at the donor site. However, below-/aboveground tissue ratio was significantly lower at the transplant site compared to the donor site. Z. marina survival was maintained through vegetative reproduction, while peak season for lateral shoot recruitment was late winter for both donor and transplant site populations. However, vegetative reproduction mainly occurred during late winter and spring at the transplant site, whereas lateral shoots were evident across all seasons except late spring in the donor site. More pronounced seasonal variations were found at the transplant site compared to the donor site. These results indicate that Z. marina populations at the two sites possess distinct phenotypic variations induced by different environmental conditions, and Z. marina transplants have adapted well to the new transplant environment.