• Korean Journal of Environmental Biology
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• v.30 no.1
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• pp.47-53
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• 2012

To evaluate adaptation success of $Zostera$ $caespitosa$ transplants, we transplanted the seagrass shoots at the bare area in close proximity to the donor bed using staple method in October 2005. Shoot density, morphological characteristics and leaf productivity of transplants and reference plants in the vicinity of the planting site were monitored monthly for 2 years. While shoot density of reference plants exhibited significant seasonal variations; increasing during spring and summer and decreasing during fall and winter, that of transplants increased consistently without initial loss during the whole study period. Although sheath length, leaf width and shoot height and weight of sheath, leaf and shoot of transplants were smaller than those of reference plants at the start of transplantation, increased rapidly reaching even higher values than those of reference plants 5 months after transplantation. Leaf productivity of transplants and reference plants showed seasonal variations; increasing during spring and summer and decreasing during fall and winter. But, leaf productivity of transplants increased at the beginning of transplantation during fall which is low production period. All of the $Z.$ $caespitosa$ transplants survived during the whole study period. Rapid changes in shoot morphology and growth of transplants indicated that $Z.$ $caespitosa$ transplants had great morphological plasticity and adapted successfully within 5 months.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.4
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• pp.373-379
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• 1994

Final biomass yields(cells/ml) and growth rates(divisions/day) of 4 clones of marine diatoms isolated from the Korean coastal waters were measured in media with 6 different levels of added cadmium concentrations. A neritic diatom, GS-12(Chaetoceros sp.), showed no growth at 0.1ppm cadmium, and its $IC_{50}$ for final biomass yield and growth rate was 0.03 and 0.02ppm, respectively. Two clones isolated from tidal pool, NC-37 and NC-29, showed enhanced tolerance to cadmium toxicity. Extremely high tolerance to cadmium addition was found in J-21 from a eutrophicated bay, with its high $IC_{50}$ for biomass yield(1.07ppm) and growth rate(1.92ppm). Present results implied a habitat related pattern of coastal diatom clones in the cadmium tolerances. Except GS-12, the other three diatom clones are considered to be highly tolerant to cadmium stresses.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.3
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• pp.345-352
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• 1999

The sand dollar, Astriclypeus manni is commonly encountered on a subtidal sand bottom along the coast of Cheju Island. limited information has been reported on their ecology despite their natural abundance. This study reports ecology and an annual reproductive cycle of the sand dollars present at Hamdock, northern coast of Cheju Island. A. manni collected from Hamdock revealed that they are 80 to 200 mm in test diameter. Sediment Brain size analysis indicated that A. manni mostly occurs on medium (particle diameter of 500 $\mu$m) to very find sand (particle diameter of 125 $\mu$m), particularly on fine sand (particle diameter of 250 $\mu$m). Internal morphology and in situ observations on their feeding habit indicated that A. manni is a deposit feeder, feeding on organic debris contained in the sediment around its habitat. A. manni were more frequently observed near Zostrea marina bed where content of organic matter in the sediment is considered to be higher. Gonadal tissues of the male were yellow in color while female gonads appeared to be purple. Fully mature eggs, with a mean diameter of 381 $\mu$m, and sperm were observed from the histological slides of the sand dollars collected in late July to August, suggesting that A. manni spawn during July to August when water temperature reaches 20 to $25^{\circ}C$.

• ALGAE
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• v.30 no.1
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• pp.59-66
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• 2015

The growth and hole formation of Ulva australis were examined at seven coastal areas of Korea between July and August, 2013. Animal species and weight growing on the Ulva fronds were estimated at Haseom, Pohang, and Woedo. The effects of wave exposure on the morphological features and residential animals of Ulva fronds were investigated at wave-exposed and sheltered sites of Seongsan on October 19, 2013. U. australis had different frond areas ($82-665cm^2$), hole areas ($2.5-6.3cm^2$), and hole numbers (9.8-41.3 holes) at the seven sites. Within $0.1m^2$ of Ulva frond, hole areas ranged from 0.37 to $5.94cm^2$, and between 4.9 and 36.2 holes were observed. Fourteen residential animal species were observed at the three evaluated sites, 75.0 (Haseom) to 408.7 individuals $100g^{-1}$ Ulva (Pohang) per site. The dominant residential species at each site differed with Amphithoe sp. at Haseom, Monodonta spp. at Pohang, and Pagurus sp. at Woedo. The growth (frond area, wet weight) and hole number of Ulva fronds, and the number of residential animals were significantly greater in samples collected from the sheltered shore than the wave-exposed shore of Seongsan. The present results showed U. australis grew well at sheltered shores and had more holes on the fronds due to abundance of residential animals. The dominant residential animals (crabs, gammaridea, and snails) were similar in the Ulva populations of sheltered and wave-exposed shores, but greater species diversity was observed at the exposed shore (18 species ver. 11 species). In conclusion, U. australis is a keystone species providing habitat to various invertebrates and frond holes are positively correlated to the number of residential animals.

• Korean Journal of Ichthyology
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• v.21 no.2
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• pp.76-80
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• 2009

Genetic diversity and genetic structure within the Geum River and Mankyung River populations of the Korean endangered Black shinner (Pseudopungtungia nigra) were assessed by amplified fragment length polymorphism (AFLP). AFLP analysis using five primer combinations generated 447 AFLP bands with 64.1% polymorphism (Geum River 74.6% and Mankyung River 53.6%). The heterozygosities within the two populations were calculated to be 0.170 and 0.104, respectively. Their average genetic diversities are 0.240 and 0.147, respectively. The pairwise Fst value (0.150) indicated distinct genetic differentiation between the two populations. A UPGMA dendrogram based on genetic distance among the individuals revealed a division corresponding to geographical regions, with low genetic variation within the Mankyung River population, and low genetic distance (0.026) between the two populations. Consequently, the two populations may have the same genetic origin The Geum River population will be more suitable than the Mankyung River population for conservation plans to increase the population sizes. Genetic and habitat management will be necessary for the Mankyung River population.

• Journal of Fisheries and Marine Sciences Education
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• v.29 no.2
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• pp.453-465
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• 2017

UN adopted the 2030 Agenda for Sustainable Development and the Sustainable Development Goals (SDGs) in 2015, a set of 17 objectives with 169 targets expected to guide actions over the next 15 years (2016-2030). One goal expressly focuses on the oceans, that is, SDG 14 'Conserve and sustainably use the oceans, seas and marine resources for sustainable development'. More than 30% of fish stocks worldwide were classified by FAO(2016) as overfished. Globally, world capture fisheries are near the ocean's productive capacity with catches on the order of 80 million metric tons. Aquaculture production is increasing rapidly and is expected to continue to increase, but aquaculture encounters some environmental challenges, including potential pollution, competition with wild fishery resources, potential contamination of gene pools, disease problems, and loss of habitat. Accordingly, there have been a variety of world organization and conferences stressing the importance of the implementation of the ecosystem-based fisheries management(EBFM) to overcome these problems. Annual catch of Korean fisheries have shown continuously declining patterns since late 1990s. Most fish stocks are currently known to be over-exploited, and some stocks are depleted due to the increase in fishing intensity and over-capitalization of fishing fleets. Other reasons for the depletion are land reclamations and coastal pollution, which destroy spawning and nursery grounds along the coastal regions. Aquaculture production is also increasing rapidly in Korea. However, several important issues such as gene pool and interaction with capture fisheries should be considered. The EBFM approach should use the best available information coupled with a reasonable application of the precautionary approach. The EBFM has global relevance, and so the real challenge will be to develop and use reliable, robust and cost-effective means of assessing and monitoring the status of ecosystems and their resources, and rapid means of detecting any undesirable and excessive impacts that threaten sustainable use. Future fisheries education should take into account UN's SDGs, which were adopted to achieve the global 2030 agenda. However, there are some difficulties in the current fisheries education system in Korea. First, the current education organizations are limited within the old frame of traditional fisheries sciences. Second, the fisheries education is currently lack of the future-oriented education system and of customized schools or departments. Third, the on-going fisheries education has been based upon few educational policies which are sufficiently relevant to holistic SDGs of the global standard. Accordingly, directions to modern fisheries education for achieving SDGs would be, first, the transition of fisheries education structure into the future-oriented and customized education system. Second, fisheries education needs to shift to the new paradigm, which combines traditional fisheries science education with related fields such as oceanography and environmental sciences to adopt the concept of EBFM. Lastly, fisheries education should accompany relevant policies for effectively achieving SDGs.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.22 no.3
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• pp.69-76
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• 2017

Eelgrass, Zostera marina is a marine flowering plant that grows in submerged habitats for most of its lifetime, and experiences desiccation stress when exposed to air. Although the desiccation stress observed in adult eelgrass has been frequently studied, there has been little research on desiccation stress in eelgrass seeds. To survey desiccation stress in eelgrass seeds, we studied the germination rate and moisture content upon desiccation caused by exposure to air. The germination rate of the eelgrass seeds exposed to air for 1 hour at $20^{\circ}C$ and 50% relative humidity decreased markedly, and it decreased consistently as the exposure time increased. Eelgrass seeds exposed to air for longer than 11 hours did not germinate. As the exposure time of eelgrass seeds to air increased, the germination rate and moisture content decreased, showing a negative correlation. In addition, eelgrass seeds exposed to air at $30^{\circ}C$ showed significantly lower germination rates than those exposed to air at $10^{\circ}C$ or $20^{\circ}C$. Our results revealed that desiccation causes a decrease in the germination of eelgrass seeds, which will provide useful information for eelgrass habitat restoration using seeds.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.1
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• pp.1-7
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• 2020

As of 2018, Steel slag was generated approximately 24.23 million tons. Howeve, except blast furnace slag, steel slag is a typical by-product which does not have a clearly defined purpose in recycling. Thus, countries around the world are putting great efforts into developing a purpose for the recycling of steel slag. The vast habitat foundation of marine life has been destroyed due to recent reckless marine development and environment pollution, resulting in intensification of the decline of marine resources, and a solution to this issue is imperative. In order to propose a method to recycle large amounts of by-product slag into a material that can serve as an alternative to natural aggregate, the engineering properties and applicability for each mixing factor of environment friendly porous concrete as a material for the composition of seawater purification were in this study. Regarding the nutrient elution properties, it was clear that the nutrients continuously flowed out up to an immersion time by 8 months in natural seawater; the nitrogenous fertilizer displayed excellent elution properties in this regard.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.23 no.4
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• pp.192-203
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• 2018

The surfgrass Phyllospadix iwatensis is native in the exposed rocky shores of the Northwestern Pacific Ocean. In Korea, P. iwatensis is mainly found on the rocky subtidal zone in the central eastern coast. In this study, to examine the ecological characteristics of P. iwatensis, we investigated changes in morphological characteristics, density, biomass, and leaf productivity as well as changes in the underwater irradiance and water temperature of its habitat monthly from August 2017 to July 2018. Underwater irradiance and water temperature showed clear seasonal changes; increases in spring and summer and decreases in fall and winter. Morphological characteristics, shoot density, biomass, and leaf productivities of P. iwatensis exhibited significant seasonal variations, increasing in winter and spring and decreasing in summer and fall months. P. iwatensis leaf productivities both per shoot and per unit area showed significant positive correlations with underwater irradiance. The average leaf productivity of P. iwatensis per area was $6.3{\pm}1.3g\;m^{-2}d^{-1}$, while minimum and maximum values were $2.4{\pm}0.3g\;m^{-2}d^{-1}$ in February 2018 and $16.4{\pm}4.4g\;m^{-2}d^{-1}$ in May 2018, respectively. The optimum water temperature for the growth of P. iwatensis in this study was between $12-13^{\circ}C$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.1
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• pp.105-113
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• 1995

Seasonality in biomass and egg Production was investigated for Calanus sinicus, one of the major copepods in Asan Bay, Korea. Biomass of this species in this restricted embayment showed only one Peak in spring, but e99 Production showed two Peaks, spring (April and May) and fall (September). Average egg Productions during the spawnlng seasons were 16.3 egg/female/day (spring) and 7.6eggs/female/day (fall) with maximum egg Production of 39.0 eggs/female/day. Food concentrations in this bay measured'1 terms of particulate organic carbon (POC) were relatively high around the year, and correlation between egg Production and POC was not significant. With the food Provided sufficiently animals Produced a lot of fecal Pellets, but egg Production was ceased after several days of experiment. From these results it was believed that egg Production in this bay was influenced by food quality and feeding history rather than food concentrations. Habitat temperatures also seem to have influence on egg Production from the tacts that no egg was Produced at extreme habitat temperatures, although the correlation between the two was not significant. In this bay, two generations with different time periods seem to progress yearly. Distribution was coupled with life cycle only at certain time of the year. During the other periods predation pressure by the higher trophic levels and shift of the centers of the distributions toward deeper outer bay seemed to be responsible for the observed distribution and egg Production of this species in this bay. Comparing with the Previous reports, migration of fairly long distance and continual reproduction seemed possible for this species.