• Ocean and Polar Research
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• v.35 no.4
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• pp.427-439
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• 2013

Carbon cycling and productivity within Weno Island of Micronesia enclosed by the coral reef may be likely self-maintained and insignificantly affected by the open ocean. Therefore, it is important to understand the role of the mangrove known as providing the organic matter and habitats for many organisms in this enclosed area. In order to trace the nutritional source of fauna (mostly invertebrates) in the mangrove forest of Weno island, we analyzed the fatty acid (FA) and carbon and nitrogen stable isotopes of potential nutritional sources (mangrove leaf & pneumatophore, seagrass leaf & root, surface sediment, and particulate organic matter (POM) in water) and consumers (4 gastropods and anomura). The mangrove and seagrass contained the abundance of 18:2${\omega}$6, and 18:3${\omega}$3, whereas FAs associated with phytoplankton and bacteria were accounted for a high proportion in the surface sediment and POM. FA composition of consumers was found to be similar to those of the surface sediment, mangrove, and seagrass. These were also confirmed through the mixing model of stable isotope for contribution of nutritional sources to consumers. Overall results with the feeding types of investigated mangrove fauna indicate that investigated mangrove fauna obtained their nutrition from the various sources, i.e. the mangrove for Littorina cf. scabra, the microalgae for Strombus sp., and omnivorous Pagurus sp. and Terebralia cf. palustris. However, it is obvious that the nutrition of most species living in the mangrove ecosystem is highly dependent on the mangrove, either directly or indirectly. More detail food-web structure and function of the mangrove ecosystem would be established with the analysis of additional fauna and flora.

• ALGAE
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• v.22 no.3
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• pp.193-199
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• 2007

This study was carried out to investigate the charateristics of environmental factors and the species compositions of phytoplanktons and periphytons in order to analyze the marine ecosystem (DOK1-3) with freshwater (Mul) in the coast of Dokdo. Mean values of conductivity (TSD) (44.3 mS cm–1), total dissolved solids (30.9 mg L–1), salinity (31.8 psu), total suspended solids (39.2 mg L–1), and ash-free dry matter (AFDM) (8.8 mg L–1) were higher in DOK1- 3 than those in Mul (3.2 mS cm–1, 2.3 mg L–1, 1.9 psu, 2.8 mg L–1 and 2.8 mg L–1, espectively), while mean amounts of soluble reactive phosphorus (SRP) (7.5 μg P L–1) and soluble reactive silicon (SRS) (0.1 μg Si L–1) were significantly lower in DOK1-3 than those in Mul (117.3 μg P L–1 and 4,105 μg Si L–1, respectively). The phytoplanktons was a total of 59 species in Dokdo, which were composed of 1 species (1.7%) for Chrysophyceae, 43 species (72.9%) for Bacillariophyceae and 15 species (25.4%) for Dinophyceae. The biomass (Chl-a, phaeopigment and AFDM) of epilithic algae (ELA), epizooic algae (EZA) and epiphytic algae (EPA) were varied with the kinds of substrates (EPA > ELA > EZA) in the whole stations. Water environments was comparatively clean in the coast of Dokdo as comparing with those of the land. However, the monitoring of marine ecosystem in the Dokdo should be continued for species conservation according to the global warming by the climatic change.

• Journal of the korean society of oceanography
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• v.35 no.1
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• pp.56-64
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• 2000

The importance of terrestrial organic matter as a food source for a brackish water clam Corbicula japonica was evaluated using stable carbon isotope ratios (${\delta}^{13}$C) in its tissues and potential food resources in an estuarine system of Youngil Bay, Korea. Suspended particulate organic matter (POM) had distinct ${\delta}^{13}$C values from riverine (-31.8 to -27.2%$_o$) to marine waters (-21.0 to -16.6%$_o$). Estuarine macroalgae had a wide ${\delta}^{13}$C range of -22.8 to -15.0%$_o$. The ${\delta}^{13}$C values of riverine POM were more negative than that of riverine phytoplankton (-26.5 to -24.2%$_o$) but similar to that of freshmarsh plant species (-29.1 to -27.5%$_o$ for Phragmites communis and -28.5 to -27.0%$_o$ for Salix gracilistyla), These ${\delta}^{13}$C values suggest that the POM transported by the Hyungsan River is predominantly of terrestrial origin rather than riverine autochthonous sources. The ${\delta}^{13}$C values of Corbicula japonica tissues (-28.7 to -27.2%$_o$) were most similar to values for riverine POM and freshmarsh plants. There was no significant difference in the isotopic composition of the clam individuals. The results indicate a predominant contribution of organic carbon derived from terrestrial and fresmarsh plant detritus to the diet of Corbicula japonica. Our results also confirm previous suggestion that terrestrial organic matter can be incorporated into estuarine food webs although its role is confined to the upper estuarine reaches.

• Korean Journal of Microbiology
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• v.38 no.4
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• pp.287-292
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• 2002

The composition of bacterial communities was detected in surface water of Cheonho Reservoir dominated by cyanobacteria, using fluorescent in situ hybridization (FISH) method. Total bacterial numbers were very high ranging from 0.6～$1.3{\times}10^7 \cells{\cdot}ml^-1$, whereas the ratio of Eubacteria to total bacteria was 29.8~45.8%, which was lower than that in other freshwater ecosystems. On average only 2.1% of DAPI-stained bacteria were detected by FISH with probes for $\alpha$, $\beta$, and $\gamma$-groups, respectively. Unknown eubacteria which was not bound to any probes except EUB 338, was relatively high. On the other hand, the Cytophaga-Flavobacterium group increased following the change of dominant species from Anabaena sp. to Microcystis sp. This result showed that bacterial communities could be affected by phytoplanktons, especially cyanobacteria.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.25 no.4
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• pp.160-172
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• 2020

To understand on-site feeding traits of Noctiluca scintillans with unprecedented high abundances around Dokdo in spring, 2014, the composition and abundance of food items in the digestive vacuole of the species were analyzed. Abundances of N. scintillans ranged from 4,328~17,791 inds.m^-3 around Dokdo during the study. The incidence of preyed items in the vacuole of N. scintillans ranged by averaged 32% (24~50%) in the surface waters around Dokdo. Diverse preyed items consisted of fecal pellet, protozoans, pollen, diatoms, dinoflagellates, copepods and ichtyoplankton, while fecal pellets were dominantly fed by N. scintillans (43%) and next by protozoans (19%), pollen (18%), diatoms (7%) and dinoflagellates (4%). Fecal pellet, protozoans and pollen were relatively preferred by N. scintillans compared to diatoms, dinoflagellates and ichtyoplankton based on the incidence in the food vacuoles. Present results indicated that high abundance of N. scintillans found around Dokdo was likely associated with non-phytoplankton items rather than previously well-known diatoms as prey during the study.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.3
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• pp.155-162
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• 2009

To characterize the initiation, propagation and termination of Cochlodinium polykrikoides blooms in the southeast coastal waters of Korea, 2008, we analyzed the data set of phytoplankton composition, physical and chemical water properties, and meterological data. C. polykrikoides bloom in 2008 were long lasting and restricted to the coastal area with a low density. Our results indicate that C. polykrikoides blooms were affected by the atypical cold waters occurring in east-south coastal water in the early July. The cold water masses probably protected the free living cells of C. polykrikoides from entering into the coastal area from offshore waters as a pelagic seed population. The low density blooms of small scale established possibly by the germination of C. polykrikoides cyst in shallow coastal bottom could have not spread over because of the weak wind and low nutrient concentrations caused by severe drought in July and September.

• Korean Journal of Ecology and Environment
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• v.34 no.1 s.93
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• pp.45-53
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• 2001

Transport of cyanobacterial toxins (microcystin-LR, -RR, -YR) were assessed from a eutrophic lake, Lake Suwa, through the outflowing river, the Tenryu River, and its irrigation channel branch. Temporal variation of phytoplankton species composition in the river coincided with those of the lake; Microcystis ichthyoblabe dominated from June to July, and M. viridis dominated from August to September. When cyanobacterial bloom occurred, microcystins were continuously detected at the concentration of $0.3{\sim}3.2\;{\mu}g/l$ even at 32 km downstream. The change of the content of three microcystin variants were related both with the total cell density of Microcystis and with the change of Microcystis species composition. When Microcystis ichthyoblabe dominated during July, only microcystin-RR (MC-RR) and -LR (MC-LR) were detected, while when Microcystis viridis dominated between August and October, microcystin-RR,-YR (MC -YR) and -LR were detected. Along 29 km flowing distance (flow time 11 hours) between site 2 and site 5 in the Tenryu River, cyanobacterial density and microcystin concentration were reduced by 73% and 72%, respectively, which is mostly contributed by the dilution effect of tributary waters (61% and 57%, respectively) . In the artificial irrigation channel microcystins and cyanobacterial cells were decreased less than in the natural river. The results indicate that cyanobacterial toxins can be transported far downstream without much removal and give hazards to water usage in downstream of eutrophic lakes with cyanobacterial blooms.

• Ocean Science Journal
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• v.41 no.1
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• pp.11-29
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• 2006

We investigated species composition and spatial distribution of the euphausiid community in the Yellow Sea and identified the relationship with environmental factors (temperature, salinity, chlorophyll $\alpha$, nitrate, phosphate, and silicate) using bimonthly data from June, 1997 to April, 1998. The environment varied during the sampling period. In warm seasons, thermocline was well developed rendering lower temperature and higher salinity and nutrient concentrations in the bottom layer. During cold seasons the water column was well mixed and no such vertical stratification was noted. Horizontal distribution of temperature, however, differed slightly between near-coast and offshore areas because of the shallow depth of the Yellow Sea, and between southern and northern areas because of the intrusion of water masses such as Yellow Sea Warm Current and Changjiang River Diluted Water. Four euphausiid species were identified: Euphausia pacifica, E. sanzoi, Pseudeuphausia sp. and Stylocheron affine. E. sanzoi and S. affine were collected, just one juvenile each, from the southern area in June and December, respectively. Pseudeuphausia sp. were collected in the eastern area all the year round except June. E. pacifica occurred at the whole study area and were the predominant species, representing at least 97.6% of the euphausiid abundance. Further, the distribution pattern of the species was varied in regards to developmental stages (adult, furcilia, calyptopis, egg). From spring to fall, E. pacifica adults were abundant in the central area where the Yellow Sea Bottom Cold Water prevailed. Furcilia and calyptopis extended their distribution into nearly all the study area during the same period. From late fall to winter, adults were found at the near-coastal are a with similar pattern for furcilia and calyptopis. The distribution pattern of E. pacifica was consistent regarding temperature, salinity, and three nutrients during the sampling period, whereas chlorophyll $\alpha$ showed a different pattern according to the developmental stages. The nutrients should indirectly affect via chlorophyll $\alpha$ and phytoplankton concentration. With respect to these results, we presented a scenario about how the environmental factors along with the water current affect the distribution of E. pacifica in the Yellow Sea.

• Korean Journal of Ecology and Environment
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• v.34 no.3 s.95
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• pp.175-184
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• 2001

The temporal and diel changes of cyanobacterial cell density, species composition, and cyanobacterial toxins (microcystin-RR, -YR, -LR) were examined for the outflow water of Lake Suwa in Japan from May to October, 1998. The highest total cell densities of Microcystis were observed in July and September, when the dominant phytoplankton was Microcystis ichthyoblabe and M. viridis, respectively. Both the species composition and total cell density of Microcystis affected the variation of the concentration of three microcystin variants. Only microcystin-RR(MC-RR) and -LR (MC-LR) were detected in July when Microcystis ichthyoblabe dominated, while microcystin-RR, -YR (MC-YR) and -LR were detected in August and October when Microcystis viridis dominated. The microcystin concentration and the cell density of Microcystis in the outflow water showed diel variations; the ratio of maximum to minimum value was $3{\sim}20$ fold far microcystin concentration, and $5{\sim}31$ fold for cell density. The diel variations of toxin concentration as well as Microcystis cell density was closely related to the diel variation of wind. During the windy period, when higher speeds occurred in the afternoon hours than morning hours, both the cell density of Microcystis and microcystin concentration tended to increase in the morning and decrease in the afternoon. The results of this study suggest that controlling the timing of lake discharge at the floodgate or intake tower can be useful for water resource management with respect to decreasing cyanobacteria biomass within intake water.

• Korean Journal of Environmental Biology
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• v.29 no.4
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• pp.296-304
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• 2011

This study was carried out to investigate the relation between water quality and structure of the aquatic ecosystem in the Lake Gachang from February to December in 2010. The annual mean COD (Chemical Oxygen Demand) in Lake Gachang was 3.5 mg $L^{-1}$, indicating, level II of environmental standards and the trophic state was mesotrophic. The seasonal succession of phytoplankton showed that Bacillariophyceae was mostly dominant species throughout the year except August. In case of zooplankton, rotifers dominate in the most seasons, but copepod (Nauplii) in August. The macrophyte plants showed diverse species composition consisted of 9 varieties, 77 species, 64 genera, 34 families and 24 orders. Surveyed species of macroinvertebrates were classified into 1 phyla, 2 classes, 4 orders, 7 families, 9 species. The macroinvertebrates showed FFG (Functional Feeding Groups) such as GC (Gathering-Collector) and SH (Shedder). A total of 42 species of fish was collected including $Zacco$ $koreanus$ and $Coreoperca$ $herzi$. In this study, we investigated environmental factors including pollutant source, load, water quality and distribution characteristics of biota such as phytoplankton, zooplankton, macrophyte plants, macroinvertebrates, fish.