• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.spc1
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• pp.236-241
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• 2006

We measured the secondary production of the amphipod Monocorophium acherusicum Costa in a seagrass bed (Zostera marina L.) in Gwangyang Bay, southern Korea. M. acherusicum biomass was positively correlated (P<0.05) with seagrass standing crop, suggesting that there were biological interactions between the two species. M. acherusicum displays two main breeding periods per year: spring (March to April) and fall (October to November). M. acherusicum biomass in the spring breeding periods was higher than in the fall. Annual secondary production of M. acherusicum was 3.54 g DW/$m^2$/yr with an annual P/B ratio of 3.48. Secondary production and the P/B ratio of M. acherusicum were lower than those observed for other amphipods inhabiting seagrass beds. These results suggest that biological interactions between M. acherusicum and seagrass, as well as dietary competition with other amphipods can potentially cause declines in secondary production and the P/B ratio.

• The Journal of the Acoustical Society of Korea
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• v.27 no.1
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• pp.33-39
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• 2008

Void fraction of air bubble in the seagrass bed by photosynthesis was estimated with sound speed dispersion. A field experiment was conducted at Seagrasss bed of which bottom type is sandy mud and 120 kHz CW waveform was transmitted to obtain backscattered signals from seagrass bed. The differences of the arrival time of received signal from seagrass bed were observed between day and night. The diurnal variation of arrival time was caused by sound speed dispersion of air bubble generated by photosynthesis of seagrass.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.4
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• pp.305-312
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• 2010

Seagrass beds are a type of coastal wetland with many ecosystem services and precious economic values. Seagrass meadows used to be widespread along the coasts in northern Chinese seas, yet they have long been overlooked and lack devoted study on their history and status. This paper firstly reveals, by synthesis of information on composition of seagrass species and their distribution, that the seagrasses in this region have experienced considerable declines, both in terms of distribution and biomass, from the earliest record to present days. Then, a case study at the seagrass bed of Chudao is described to show the status of representative seagrass meadows. The results indicate that the environmental condition is good, seagrasses are in recovery, the planktoners are healthy and rich fishery resources and the mammal finless porpoise are associated with the seagrass bed. The cause(s) of historical seagrass decline and current conditions are also discussed, and future recommendations on seagrass protection and mapping are suggested.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.3
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• pp.181-188
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• 2012

Despite the ecological importance of seagrass beds, their distributional information in Korean coastal waters is insufficient. Therefore, we used hydroacoustic system to collect accurate bathymetry and classification of seagrass, and Kompsat-2 (4 m spatial resolution) image for detection of seagrass beds at Deukryang Bay, Korea. The accuracy of Kompsat-2 image classification was evaluated using hydracoustic survey result using error matrix and Kappa value. The total area of seagrass beds from satellite image classification was underestimated compared to the hydroacoustic survey, estimated 3.9 and $4.5km^2$ from satellite image and hydroacoustic data, respectively. Nonetheless, the accuracy of Kompsat-2 image classification over hydroacoustic-based method showing 90% (Kappa=0.85) for the three class maps (seagrass, unvegetated seawater and aquaculture). The agreement between the satellite image classification and the hydroacoustic result was 77.1% (the seagrass presence/absence map). From our result of satellite image classification, Kompsat-2 image is suitable for mapping seagrass beds with high accuracy and non-destructive method. For more accurate information, more researches with a variety of high-resolution satellite image will be preceded.

• ALGAE
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• v.22 no.2
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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.

• Proceedings of KOSOMES biannual meeting
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• 2009.06a
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• pp.157-158
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• 2009

Phytoplankton plays an important part as indicator and primary producer in marine ecosystem. Therefore, phytoplankton community appeared variously according to marine environment, so the data of nutrients, chlorophyll a, temperature, salinity, and DO were analyzed in seagrass bed of Yeoja Bay. Consequently, the phytoplankton community structures were associated with investigation time and place, and seen difference according to the existence and nonexistence of seagrass bed.

• Journal of Ecology and Environment
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• v.33 no.1
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• pp.59-65
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• 2010

Because seagrass production significantly contributes to the biodiversity and production of coastal and estuarine ecosystems, accurate estimation of seagrass productivity is a critical step toward understanding the ecological roles of seagrass in these ecosystems. To develop an accurate and effective method of measuring seagrass productivity, we estimated leaf productivity of eelgrass (Zostera marina) on the southern coast of Korea using three methods, the conventional leaf marking method, the elongation-mass method (Short '87 method), and the plastochrone method. In each season, shoots were pierced through the bundle sheath using a hypodermic needle and were collected after 2-4 weeks had elapsed to estimate their productivity. The leaf elongation and the leaf plastochrone intervals varied significantly among seasons. On an annual basis, the conventional leaf marking method showed the lowest leaf productivity estimates compared to the elongation-mass method and the plastochrone method, suggesting that the conventional leaf marking method underestimated leaf productivity as it ignored leaf maturation processes and new leaf growth within the sheath. Since the elongation-mass method considered leaf maturation processes, this method produced higher leaf productivity estimates than the conventional leaf marking method. On an annual basis, the plastochrone method produced the highest leaf productivity estimates. Below-ground productivity, which can be easily estimated using the plastochrone method, ranged between 3.29 and 5.73 (mg dry weight $shoot^{-1}\;day^{-1}$) and accounted for about 17.8% to 30.3% of total productivity. Because of the high contributions of below-ground productivity to total seagrass production, we suggest that the plastochrone method is an effective and simple technique for assessing both above- and below-ground productivities.

• The Journal of the Acoustical Society of Korea
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• v.24 no.2
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• pp.97-102
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• 2005

Acoustic experiments were performed with Zostera marina to study the characteristics of backscattering of seagrass living in the bottom interface. Field experiments were conducted in the Dongdae man, Namhae for day and night to consider the effects of air-bubble from photosynthesis of seagrass. The multi-frequency (30$\~$120 kHz) responses were measured and the distributions of back scattering strength due to the movement of seagrass were Presented by PDF (probability density function) at 120 120 kHz. The results were shown both the frequency dependence and diurnal variation of the backscattering strength between day and night. This diurnal variation may be caused by the amount of oxygen in dissolved bubbles formed by Photosynthesis of seagrass.

• Korean Journal of Environmental Biology
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• v.30 no.4
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• pp.339-348
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• 2012

To survey the seagrass distribution in Jeju and Chuja Islands, we directly observed seagrass beds using SCUBA in July, 2011. Distributional area, species composition, morphology, density, and biomass of seagrasses and environmental characteristics were examined in investigation sites. In particular, three protected seagrass species (Zostera marina, Z. caulescens and Z. caespitosa) were found in the investigation areas. While the three species were found in Chuja Island, only Z. marina was distributed in Jeju Island. Z. marina was distributed only north-eastern coast of Jeju Island, and the total coverage was $238,572m^2$. Total seagrass coverage of Chuja Island was $23,584m^2$. In detail, Z. caulescens Z. caespitosa and Z. marina were 21,216, 1,870 and $498m^2$, respectively. Of these, Z. marina was found from the intertidal to subtidal zones of 5m MSL (mean sea level) depth. Z. caespitosa and Z. caulescens were found in subtidal zones of 3~4 m and 4~6m MSL depth, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.5
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• pp.533-542
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• 2011

Numerous seagrass habitat restoration projects have been attempted recently due to the remarkable decline in seagrass coverage. Seagrass transplants tend to adapt to a new environment after experiencing transplanting stress during the early stages of transplantation. Once acclimated, the transplants grow into healthy seagrass beds via vegetative propagation. The establishment and growth dynamics of transplanted seagrasses in bays and coasts are widely reported, but few studies have been conducted on estuaries in Korea. We transplanted Zostera marina in November 2007 and November 2008 in the Nakdong estuary using the staple method, and monitored the survival, adaptation, and growth dynamics of the transplants as well as environmental factors every month for 1 year. Both transplants adapted well to the new environment without initial losses and showed rapid productivity during early summer. However, density of transplants increased 320% in 1 year from the previous year's transplants but that decreased to 59% during the following year. This significant reduction in density in the second year may have been caused by exposure to low salinity (10 psu) for 3 weeks during the unusually long monsoon season. While the survival and growth dynamics of seagrass transplants planted in bays and coasts are mainly controlled by underwater photon flux density and water temperature, salinity was the critical factor for those planted in Nakdong estuary.