• Ocean Science Journal
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• v.42 no.2
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• pp.69-79
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• 2007

A vertical transect with 4 km length was established for the macrofaunal survey on the Chokchon macrotidal flat in Kyeonggi Bay, Incheon, Korea, 1994. Tidal elevation (m) and sediment mean grain size $(\phi)$ were inversely predicted by the transfer functions from the faunal assemblages. Three methods: weighted average using optimum value (WA), tolerance weighted version of the weighted average (WAT) and maximum likelihood calibration (MLC) were employed. Estimates of tidal elevation and mean grain size obtained by using the three different methods showed positively corresponding trends with the observations. The estimates of MLC were found to have the minimum value of sum of squares due to errors (SSE). When applied to the previous data $(1990\sim1992)$, each of three inference models exhibited high predictive power. This result implied there are visible relationships between species composition and faunas' critical environmental factors. Although a potential significance of the two major abiotic factors was re-affirmed, a weak tendency of biological interaction was detected from faunal distribution patterns across the flat. In comparison to the spatial and temporal patterns of the estimates, it was suggested that sediment characteristics were the primary factors regulating the distribution of macrofaunal assemblages, rather than tidal elevation, and the species composition may be sensitively determined by minute changes in substratum properties on a tidal flat.

• Journal of the Korean earth science society
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• v.24 no.1
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• pp.46-60
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• 2003

In Namyang Bay of western Korea, macrotidal-flat deposits are divisible into three late Quaternary units: Unit M1 of upper marine mud, Unit T1 of middle siderite-bearing terrestrial clay, and Unit M2 of lower marine mud. Unit M1 represents typical Holocene intertidal mudflat deposits, showing a coarsening-upward textural trend. It probably resulted from the continual retrogradation of tidal flat during the mid-to-late Holocene sea-level rise. Reddish brown-color Unit T1 consists of homogeneous clay with abundant freshwater siderite grains and plant remains. Unit T1 is clearly separated from the overlying Unit M1 by a sharp lithologic boundary. Radiocarbon age, siderite grains and lithologic features indicate that Unit T1 is originated from freshwater bog or swamp deposition infilling the localized topographic lows during the early Holocene age. Overlain unconformably by early Holocene swamp clay, Unit M2 is orange to yellow in color and mottled, suggesting significant degree of weathering during the sea-level lowstand. Such subaerial oxidation is confirmed in the vertical profiles of geotechnical properties, clay mineral assemblages and magnetic susceptibility. Unit M2 appears to be correlated with the upper part of the late Pleistocene tidal deposits developed along the western Korean coast. The sedimentary succession of the Namyang-Bay tidal-flat deposit provides stratigraphic information for the Holocene-late Pleistocene unconformity and also permits an assessment of the preservation potential of the late Pleistocene marginal marine deposit along the western coast of Korea.

• Fisheries and Aquatic Sciences
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• v.2 no.2
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• pp.199-209
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• 1999

Before investigating the long-term variations in macrobenthic communities sampled in the Chokchon macrotidal flat in Inchon, Korea, from 1989 to 1996, we need to understand how environmental factors in the area vary. As potential governing agents of tidal flat communities, abiotic factors such as mean sea level, seawater, air temperature, and precipitation were considered. Data for these factors were collected at equal intervals from 1976 or 1980 to 1996, and were analyzed using a decomposition method. In this analysis, all the above variables showed strong seasonal nature, and yielded a significant trend and cyclical variation. Positive trends were seen in the seawater and air temperatures, and based upon this relationship, it was found that the biological sampling period of our program has been carried out during warmer periods in succession. This paper puts forth some hypotheses concerning the response of tidal flat macrobenthos communities to the changing environment including mild winters in succession.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.1
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• pp.39-47
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• 2020

In order to investigate current characteristics at the Gungpyung beach, which is a macrotidal flat, field measurements were carried out in the summer and winter at the intertidal and the subtidal zones. The distribution of residual current at intertidal flat was dominant in the northward direction in the summer and dominant in the northward and southwestern directions in the winter. The direction and speed of the residual current in the winter are highly correlated with the significant wave height, and the turbidity is also highly correlated with the significant wave height. Therefore, in the winter, high sediment rates are suspended by high waves, and sediments are transporting due to the residual current in the southwest direction. On the other hand, it is expected that the northward residual current is predominant due to the small wave in the summer, and sediment transport does not occur largely due to less suspended sediments. In addition, sediment transport in the southern direction is blocked by the dock, which is the artificial structure, and the erosion occurs in the south side of the dock. The erosion pattern in the macrotidal zone of Yellow sea is dominated by seasonal waves, and blocking of sediments by artificial structure is very important.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.05a
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• pp.369-370
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• 2000

생태계에 대한 지속적 연구를 통하여 축적되는 장기변동 자료와 이에 대한 관찰은 의미있는 가설의 전개와 생태학적 개념의 타당성에 대한 검정 등에 중요한 역할을 한다고 볼 수 있다 (Franklin, 1987). 최근들어, long-term scale에서의 생태계 변화는 생태학자들 간에 주된 관심사가 되고 있다. 이러한 배경에서 본 연구자들은 인천 연안의 대조차 간석지에서 수행되고 있는 척전 갯벌 program을 통하여 간석지 대형 저서 동물 군집의 장기 변동 (1989 ∼ 현재)을 관찰, 분석하고 있으며, 그 첫 단계로서 계절성에 관한 분석을 시도하였다. (중략)

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.5
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• pp.549-559
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• 1994

Razor clam, Solen (Solen) strictus, was collected between May 1989 and July 1990 on a macrotidal flat, Inchon, Korea. The population sampled at just above mean sea level had a mean density of 126 individuals/$m^2$. Age was determined for 872 specimens by counting annuli, a series of closely-spaced concentric growth lines. According to the fatness index spawning seemed to have occurred once per year in June, and the first recruits for the 1989 year cohort population were found in July. Solen (Solen) strictus on the Chokchon tidal flat reached a shell length of 6.2 cm in four years. Mean growth in shell length can be described by the von Bertalanffy function, which yielded estimates of growth parameters equivalent to $L_{\infty}=81.865\;mm$ shell length and K=0.320 per year: $$L_{t}=81.865(1-e^{-0.320(t+0.487)})$$$$W_{t}=7.173(1-e^{-0.320(t+0.487)})^3$$

• 한국해양학회지
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• v.20 no.1
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• pp.43-49
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• 1985

The Changgu Bay, a macrotidal coastal embayment of the west coast of Korea, is an area of extensive intertidal sedimentation. Three types of major sediment facies are identified based on grain size analysis: silt, sandy-silt, and silty-sand facies. It is found that intertidal sediment facies comprise a continuum of progressively finer sediments from lower flat to upper one. The X-radiography of the cores in the intertidal zone show a wide variety of physical and biogenic sedimentary structures. The major structures include bioturbation, current ripple and parallel-laminae. Bioturbations are observed in all core samples, especially in the silt flat zone. The degree of bioturbation increases laterally from sandy facies (low tide level) to silt facies (high tide level) due to favorable properties of fine mud for organisms. The ripple laminae, composed of current ripple foresets, characterize the silty-sand and sandy-silt flats. The parallel laminae are extensively bioturbated, and two types of laminae are distinguishable; thick-laminae with a thickness of 1 to 5mm and thin-laminae with a thickness of less than 1mm.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.5
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• pp.560-571
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• 1994

A single station representative of the razor clam, Solen (Solen) strictus, on a macrotidal flat, Inchon, Korea was sampled at bimonthly intervals between May 1989 and July 1990 by using a can corer. Estimates of growth rate and annual production of this razor clam have been made using the techniques of cohort growth analysis. Growth rate and production were highest during the first year after spawning and recruitment. The annual production was $2.83g\;DWt/m^2/yr$, mean annual biomass $256.3\;g/w^20$, and a turnover time of 5.00 yea, giving an annual turnover rate (P/B) of $0.20\;yr^{-1}$. The total annual production in wet weight ($33.22g\;WWt/m^2/yr$) appeared to consist of water in live flesh($72.6\%$) and shell($18.9\%$), whereas the dry weight of the soft parts was $8.52\%$, the ash-free dry weight $5.4\%$, and the ash content $3.1\%$ of the total wet weight.

• Fisheries and Aquatic Sciences
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• v.2 no.2
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• pp.210-217
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• 1999

Chemical oxygen demand (COD), phytoplankton cell number and chlorophyll-a concentration (Chl-a), sediment mean grain size and ignition loss were studied to determine their temporal trends in the study area. Historical data of COD, cell number and Chl-a were gathered from the late 1960s or early 1980s to 1997, and trends in temporal domain were obtained from a simple regression. Sediments for grain size and ignition loss (as organic contents in sediments) were sampled from the Chokchon macrotidal flat bimonthly from September 1990 to November 1996, and were analyzed using the decomposition method of time series analysis. In general, the first three data showed increasing trends based on regression analysis. The trends of sediment grain size fluctuated in a neutral pathway while those of ignition loss yielded no increasing pattern. In contrast with the suggestions from Ahn and Choi (1998) who reported a coarsening variation in sediment grain size to be a cause of the directional and remarkable changes of macrofaunal communities in this area, we could not find such a corresponding variation pattern from our samples. In diagnosing eutrophication, a paradoxical phenomenon was encountered between the trends in water column (COD, cell number and Chl-a) and sediment (ignition loss) data. In this paper, we inferred the possible processes that produce the discrepancy. Some explanations and biological responses to eutrophication were predicted and discussed.

• Journal of the korean society of oceanography
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• v.36 no.3
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• pp.83-92
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• 2001

An investigation on the zonal communities in Chokchon macrotidal flat, Incheon, Korea, was carried out on July 1994, eight years after the initial survey done by Frey et al. (1987a and b). A survey transect (4 km long) was established with 41 stations having an equi-interval of 100 m. Macrofaunas were sampled in July 1994. R-mode cluster analysis and ordination analysis (detrended correspondence analysis or DCA) were performed. The aims of the investigation were to: (1) observe the distribution and abundance patterns, including zonation of benthic macrofaunal communities in the area; and (2) gain information about faunal changes between two different periods. The primary feature of distribution was corresponded with Frey's zonation, and this was shaped by three level-specific species groups. Significant changes in dominant species were detected when compared with the faunal assemblages of 1986. The bivalve mollusk, Meretrix petechialis, seemed to have disappeared. Two newly arrived organic pollution indicator species, Theora fragilis and Capitella capitata, were regarded as impregnable proof of response to eutrophication, although the concrete evidence on the eutrophication source was not found.