• Title/Summary/Keyword: Gamak bay

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Characteristics of Sedimentary Environments in Gamak Bay based on Numerical Experiments (수치실험에 기초한 가막만의 퇴적 환경 특성)

  • Kim, Byeong Kuk;Park, Sung Jin;Lee, Moon Ock;Lee, Yeon Gyu;Kim, Jong Kyu
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.17 no.2
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    • pp.70-80
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    • 2014
  • We carried out numerical experiments to understand sedimentary environments in Gamak Bay where is located in the center of the southern coast of Korea. Deposition rates in Gamak Bay appeared to increase in the autumn and spring whereas they appeared to decrease in the summer and winter. These seasonal variations qualitatively coincided with seasonal variations of Ignition Loss (IL) for surface sediments. Furthermore, deposition rates turned out to be prevalent compared to erosion rates in most areas of the bay. On the other hand, current measurement results at both the northeast and south mouths of the bay showed their residual components to flow into the bay. Therefore, we can conclude that contaminated materials flowing into Gamak Bay will precipitate to be deposited in the bay as long as there is no specific events such as dredging.

Composition of Phytoplankton in Gamak Bay by CHEMTAX Analyses (CHEMTAX 활용한 가막만 식물플랑크톤 군집조성)

  • Oh, Hyun-Taik;Kim, Da-Jung;Lee, Won-Chan;Jung, Rae-Hong;Hong, Suk-Jin;Kang, Yang-Sun;Lee, Yang-Woo;Tilburg, Charles
    • Journal of Environmental Science International
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    • v.17 no.10
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    • pp.1155-1167
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    • 2008
  • Chlorophyll a (chl a) has been used as an indicator for phytoplankton biomass in pelagic ecosystems due to the relative ease of measurement and selectivity for autotrophs in mixed plankton assemblages. However, the use of chi a as an indicator for phytoplankton biomass is restricted due to its inability to resolve taxonomic differences of phytoplankton and the highly variable relationship of chi a with phytoplankton. Here, we describe the analysis of High-Performance Liquid Chromatography (HPLC) photosynthetic pigment data using CHEMTAX, which is a matrix factorization program that uses chemical taxonomic indices (phytoplankton carotenoids) to quantify the abundance of phytoplankton groups. Compared to direct microscopic counting that can distinguish species within broad groups, the resolution of taxonomic groups by CHEMTAX is generally coarse. It can only distinguish between diatoms, dinoflagellates, cryptophytes, cyanobacteria, chlorophytes, prasinophytes, and haptophytes. However, CHEMTAX analysis is much faster and less expensive than microscopic counting methods. HPLC pigment observations were taken in the spring, summer, fall, and winter in$ 2005\sim2006$ within Gamak Bay, South Korea. CHEMTAX results revealed that diatoms were the dominant taxonomic group in Gamak Bay. In inner Gamak Bay, the ratio between diatoms and cryptophytes was $75\sim80%$, and the ratio between dinoflagellates and cryptophytes was $10\sim15%$. In outer Gamak Bay, the ratio between diatoms and cryptophytes was $85\sim90%$, and the ratio between dinflagellates and cryptophytes was only $1\sim5%$. The population structure was seasonal. Relative diatom populations were less in the summer than the winter season.

Comparison of marine environment and oyster culture between in Gamak and Hiroshima Bays (가막만과 히로시마만의 해양환경과 굴양식의 비교)

  • Lee, Moon-Ock;Kim, Jong-Kyu;Kim, Byeong-Kuk;Kwon, Yeong-Ah
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2006.11a
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    • pp.481-484
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    • 2006
  • This research compares oyster farming in Gamak Bay which Hiroshima Bay which has nearly similar marine environments. The marine environment of these two waters has similar variations of air temperature, sea surface temperature, precipitation and salinity. However Hiroshima Bay is higher than Gamak Bay in the sea surface temperature and Hiroshima Bay is also higher than Gamak Bay in the salinity. Their oyster farming method is basically similar but it is different in their facilities. We need to take some measures against high mortalities, and in addition, to enhance the rate of seed collection.

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Spatial distribution of phytoplankton in Gamak Bay in spring, with emphasis on small phytoplankton

  • Yeongji Oh;Yoonja Kang
    • Korean Journal of Environmental Biology
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    • v.40 no.4
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    • pp.374-386
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    • 2022
  • Phytoplankton communities, with emphasis on picoplankton and nanoplankton, were investigated in Gamak Bay, South Korea, where freshwater input and coastal water intrusion shape ecosystem functions. Shellfish farms and fish farms are located in the inner bay and outer bay, respectively, and tides translocate uneaten food and urine production from aquaculture farms toward the inner bay. Water masses were distinctly different based on a significantly different density between the surface and bottom layer and among three water masses, including the inner bay, outer bay, and Yeosu Harbor. Phytoplankton communities were quantified using flow cytometry and size-fractionated chlorophyll-a (chl-a) was measured. Salinity was a principal variable separating phytoplankton communities between the surface and bottom layer, whereas Si(OH)4 controlled the communities in the inner bay, and NH4+ and PO43- governed the outer bay communities. While phycocyanin-containing (PC) cyanobacteria dominated in the outer bay, phycoerythrin-containing (PE) cyanobacteria dominance occurred with cryptophyte dominance, indicating that nutrients affected the distribution of pico- and nanoplankton and that cryptophytes potentially relied on a mixotrophic mode by feeding on PE cyanobacteria. Interestingly, picoeukaryotes and eukaryotes larger than 10 ㎛ were mostly responsible for the ecological niche in the western region of the bay. Given that chl-a levels have historically declined, our study highlights the potential importance of increased small phytoplankton in Gamak Bay. Particularly, we urge an examination of the ecological role of small phytoplankton in the food supply of cultivated marine organisms.

Characteristics of Phosphate Flux at the Sediment-water Interface in Gamak Bay during the Hypoxic Water Mass (가막만 빈산소 발생 시 해수-퇴적물 경계면에서 인산염플럭스 특성)

  • Kim, Sook-Yang;Jun, Sang-Ho;Lee, Young-Sik;Lee, Yong-Hwa;Kim, Byeoung-Man
    • Journal of Environmental Science International
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    • v.20 no.9
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    • pp.1069-1078
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    • 2011
  • The environmental changes related to hypoxic water mass were investigated at Gamak bay in summer times, June, July and August 2006. The hypoxic water mass was found, in first, at the northern area of Gamak bay on 27 June. This water mass has been sustained until the end of August and disappear on 13 September. In Gamak bay, the hypoxic water mass was closely related to geography. During the formation of oxygen deficiency, changes in dissolved nutrients was studied and found that on surface layer and lower layer, DIN were 0.80 ${\mu}M$~19.8 ${\mu}M$(6.03 ${\mu}M$) and 1.13 ${\mu}M$~60.83 ${\mu}M$(10.66 ${\mu}M$), and DIP were 0.01 ${\mu}M$~0.92 ${\mu}M$(0.24 ${\mu}M$), and 0.01 ${\mu}M$~3.57 ${\mu}M$(0.49 ${\mu}M$), respectively, far higher distribution on lower layer of the water where hypoxic water mass was occurred. The configuration of phosphorus was analyzed to figure out the possibility of release of phosphorus from sediments. It was found that the Labile-Phosphorus, which is capable of easy move to water layer by following environmental change was found more than 70%. Therefore, in Gamak bay, it was found that the possibility of large amount of release of soluble P into the water, while hypoxic water mass was occurred in deep layer was higher. It is suggested that DIP in the northern sea of Gamak bay mainly sourced from the soluble P from lower layer of the waters where hypoxic water mass was created more than that from basin. However, existence form of phosphorus in sediments during normal times, not during creation of hypoxic water mass, needs further study.

Seasonal variation of the zooplankton community of Gamak Bay, Korea

  • Moon, Seong Yong;Kim, Hee Yong;Oh, Hyun Ju
    • Korean Journal of Environmental Biology
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    • v.38 no.2
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    • pp.231-247
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    • 2020
  • The seasonal variation in the zooplankton community and hydrographic conditions were examined in three regions (inner, central, and outer regions) of Gamak Bay, Korea. Zooplankton samples were collected over a period of 12 months from January to December 2006. The hydrographical parameters of temperature, salinity, chlorophyll-a concentrations, dissolved oxygen, and chemical oxygen demand were measured. The total zooplankton density varied from 411 to 58,485 ind. m-3, with peaks in early summer. A total of 65 taxa accounted for approximately 86.9% of the annual mean zooplankton density: Noctiluca scintillans (30.9%) Paracalanus parvus s. l.(24.3%), Acartia omorii(11.9 %), Eurytemora pacifica (5.7%), cladocerans (4.1%), cirriped larvae (3.8%), Oithona similis (3.7%), and Pseudevedne tergestina(2.5%). Copepods dominated numerically throughout the year and comprised 54.3% of the total zooplankton. Most of the dominant copepods showed a well-defined seasonal pattern. The density and diversity of zooplankton in Gamak Bay were influenced by the hydrographic environment that was subject to significant spatial and temporal variations. Multivariate statistics showed that seasonal temperature was the most significant predictor of zooplankton taxa, density, and diversity, as well as the density of dominant taxa. Our results suggest that fluctuations in the zooplankton populations, particularly copepods, followed progressive increments in the temperature and COD concentrations.

Geochemical Characteristics of Intertidal Sediment in the Semi-enclosed Bays of the Southern Region of Jeollanam Province (전남 남부 반폐쇄적인 내만 갯벌 퇴적물의 지화학적 특성)

  • Hwang, Dong-Woon;Kim, Pyoung-Joong;Jeon, Sang-Back;Koh, Byoung-Seol
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.46 no.5
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    • pp.638-648
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    • 2013
  • To understand the geochemical characteristics of intertidal sediment in a semi-enclosed bay, we measured various geochemical parameters, including grain size, ignition loss (IL), chemical oxygen demand (COD), acid volatile sulfide (AVS), and trace metals (Al, Fe, Cu, Pb, Zn, Cd, Hg, and As), in intertidal sediment from three bays (Deukryang Bay, Yeoja Bay, and Gamak Bay) in the southern region of Jeollanam Province. The intertidal sediment in Deukryang Bay consisted of various sedimentary types, such as sand, gravelly muddy sand, mud, and silt, whereas the intertidal sediments in Yeoja and Gamak Bays were composed mainly of mud. The concentrations of IL, COD, AVS and trace metals in the intertidal sediments of the three study regions were relatively high near areas affected by input of stream waters and/or shellfish farming waste. The concentrations of organic matter and trace metals in Gamak Bay were much higher than those in Deukryang and Yeoja Bays, which appears to be due to the influence of anthropogenic pollutants, originating from the city and the industrial complex near Gamak Bay. The evaluation results of organic matter and metal pollution using the sediment quality guidelines showed that the intertidal sediments in the three study regions were not polluted in terms of organic matter and trace metals. In future, sustainable management for sources of organic matter and trace metal is necessary to conserve a healthy benthic ecosystem in intertidal sediments.

Distribution Characteristics of Alkaline Phosphatase Activity and Phosphatase Hydrolyzable Phosphorus in Northern Gamak Bay in Autumn and Winter, 2009 (2009년 추계와 동계 가막만 북부해역에서 alkaline phosphatase 활성과 phosphatase 가수 분해성 인의 분포 특성)

  • Kwon, Hyeong-Kyu;Oh, Seok-Jin;Yang, Han-Soeb
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.43 no.5
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    • pp.540-546
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    • 2010
  • We investigated variations in alkaline phosphatase (APase) activity and alkaline phosphatase hydrolyzable phosphorus (APHP) in northern Gamak Bay from September to December 2009. Dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) decreased gradually, and the DIN/DIP ratio was higher than the Redfield ratio (16) based on molecular concentrations during most of the observation period. The total APase (T-APase) activity increased with decreasing DIP concentration; i.e., the Relationship between T-APase and DIP showed a high negative correlation (r=-0.80, P<0.001), with APase activity being a good indicator of DIP limiting the Redfield ratio. The T-APase was positively correlated with the concentration of chlorophyll a (r=0.73, P<0.001). This suggests that a major portion of APase activity in northen Gamak Bay seawater is attributed to phytoplankton. The proportion of APHP among dissolved organic phosphorus (DOP) was low in September and high in November. Thus, APase-producing phytoplankton may be able to grow by utilizing APHP as a phosphorus source in autumn when DIP is limiting. Thus, APase activity and the use of DOP by phytoplankton may play an important role in the growth of phytoplankton under DIP limiting conditions such as those of northern Gamak Bay.

Seasonal changes in copepod biomass and production in Gamak Bay, Korea

  • Moon, Seong Yong;Oh, Hyun Ju
    • Fisheries and Aquatic Sciences
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    • v.24 no.4
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    • pp.171-179
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    • 2021
  • To better understand the ecological functioning of the coastal ecosystem in Gamak Bay on the southern coast of Korea, seasonal changes in the density, biomass, and secondary production of the copepod community were investigated. Environmental measurements (temperature, salinity, and chlorophyll a) and copepod sampling were performed seasonally from January to December 2006. The mean density of copepods (excluding nauplii) varied from 949 to 5,999 ind · m-3; copepod density was at its highest from March to July. The copepod community comprised 32 taxa, including Calanoida, Cyclopoida, and Harpacticoida. The predominant species were Paracalanus parvus s. l., Acartia omorii, Eurytemora pacifica, Oithona similis, A. erythraea, Centropages abdominalis, Pseudodiaptomus marinus, and Calanus sinicus. There were significant spatial and seasonal variations in copepod total biomass, which ranged from 0.33 to 43.10 mg C m-3. Mean secondary production of the copepods in Gamak Bay, estimated as 2.05 ± 1.63 mg C m-3 d-1 using the Huntley and Lopez growth model, was over 2 times higher than the value given by application of the Hirst and Bunker model (1.09 ± 0.85 mg C m-3 d-1). The daily production rate to biomass (P/B) ratio varied between 0.08 and 0.86 d-1 (Huntley and Lopez model), and 0.18 and 0.33 d-1 (Hirst and Bunker model). Our results emphasize the ecological significance of using models to estimate the secondary production of copepods and provides the first report of copepod production in Gamak Bay.

Temporal and Spatial Variation in Fish Larvae in Gamak Bay and Yeoja Bay, South Sea of Korea

  • Ryu, Jung-Hwa;Kim, Jeong-Bae;Kim, Jin-Koo
    • Fisheries and Aquatic Sciences
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    • v.14 no.1
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    • pp.55-61
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    • 2011
  • Fish larvae were collected monthly with an ichthyoplankton net from 18 stations (including four stations located in eelgrass beds) in Gamak Bay and Yeoja Bay, southern Korea, in 2007. In total, 33 species of fish larvae were collected, of which Engraulis japonicus (48.5%), Tridentiger trigonocephalus (21.5%), and Omobranchus elegans (9.2%) were dominant. Dominant species varied seasonally: Hexagrammos otakii during December and January, Pholis nebulosa during January and March, Acanthogobius flavimanus in April, T. trigonocephalus in May, E. japonicus during June, July, September, and November, and Sillago japonica in August. Dominant species also differed between sites inside and outside the bays. Leiognathus nuchalis, O. elegans, and T. trigonocephalus were more abundant inside, while H. otakii was more abundant outside. From cluster analysis, three groups were identified according to sampling months (January-April, May-September, and October-December) and two groups according to station (inside and outside bays). The occurrence of small larvae of almost all major fish species indicated that the bays were used as spawning and nursery grounds. An exception was Lateolabrax japonicus, whose specimens were relatively large (>19 mm TL), suggesting that this fish may spawn offshore, with its juveniles approaching the bays with growth.