• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.2
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• pp.101-109
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• 1997

The present study was carried out to investigate the temporal and spatial changes in species composition and abundance of polychaetes in Lake Shihwa. Macrobenthic fauna were collected from eight sampling surveys performed in March, June, September and December of 1994, March and October of 1995, February and August of 1996, using a modified van Veen grab with 0.1 $m^2$ coverage area. Polychaete worms, the most abundant macrofaunal group, comprised of 1~22 species at each investigation; number of species continuously decreased during the survey period. The mean density of polychaete was $794{\pm}1,275\;indiv.{\cdot}m^{-2}$ and showed a large fluctuation over time. The variation in abundance was mainly coupled with the domination of Polydora ligni occupying 83% in total density. The next dominant species were Pseudopolydora kempi (mean density of 31 $indiv.{\cdot}m^{-2}$) and Capitella capitata (mean density of 23 $indiv.{\cdot}m^{-2}$). Abundant polychaetes in Lake Shihwa are known to be tolerant to sediment pollution. Ecological indices such as diversity (H') and dominance (D) also indicated that the number of species significantly decreased and a few species predominated in Lake Shihwa after the dike construction. The azoic zone were extended from the upper reach of Lake Shihwa to the vicinity of the dike over time. The reduced number of species, predominance of pollution indicator species and development of an azoic zone reflect severe deterioration of benthic environments in Lake Shihwa.

• Korean Journal of Microbiology
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• v.15 no.1
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• pp.20-30
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• 1977

Relationship of soil properties and seasonal variation on microbilogical population to-continuous culture and first-time culture of ginseng was investigated by bimonthly from May 1976 to January 1977. pH and P contents of 2 years continuous culture of soil were higher than other culture plot of soil, and contraty to the above, 2 years first-time culture of ginseng soil was conplot of soil, and contraty to the above, 2 years first-time culture of ginseng soil was contained more potassium contents than other culture plot of soil. In microbiological fluctuation with seasonr in various soil conditions, the population, trends of Fusarium spp., Erwiniaspp., and flourescent Psedudomonas spp. were increased in May and July in general, but decreased in the other month. It was observed that in all type of soil, Fusarium spp. was distributed in abundance in and on rihizosphere, and decreased the propagules numbers as soil depth increase. The numbers of Erwinia spp. and fluorescent Pseudo-monas spp. were distributed greater in numbers on the surface zone of soil depth decreasing the numbers along the soil layer increase, and also in 2years continuous culture of soil especially, a great numbers of Erwinia spp. and fluorescent Pseudomonas were evenly distributed in surface zone and rhizosphere. Ginseng disease with a high incidence of bacterial disease in continuous culture of 2 and 4 years was seemed to be associated with soil bacteria that was high in numbers of Erwinia spp. and fluorescent Pseudomonas spp. in May and July.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.1
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• pp.19-30
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• 2005

To investigate the seasonal distribution and grazing impacts of benthic protozoa in mud flat, their abundance, biomass and grazing rates of benthic protozoa were evaluated at interval of two or three month in Gangwha Island from April, 2002 to April, 2004. Heterotrophic flagellates and ciliates accounted for an average 98% of benthic protozoa biomass. Abundance and carbon biomass of heterotrophic flagellates ranged from $0.2{\times}10^5$ to $5.9{\times}10^5\;cells\;cm{-3}$ and from 0.02 to $9.2\;{\mu}gC\;cm^{-3}$, respectively. Biomass of heterotrophic flagellates was high in spring and fall, and showed no differences among stations. Abundance and biomass of heterotrophic flagellates decreased with the depth and were high within the surface 2.5 m sediment layer. The majority of heterotrophic flagellates were less than $10\;{\mu}m$ in length, and few euglenoid flagellates were larger than $20\;{\mu}m$. Abundance and carbon biomass of ciliates ranged from $0.1{\times}10^3$ to $17.8{\times}10^3\;cells\;cm^{-3}$ and from 0.02 to $9.1\;{\mu}gC\;cm^{-3}$, respectively, and those of ciliates were high in spring and fall. Biomass of ciliates was high within the surface 2.5 mm sediment layer and was higher at st. J2 and st. J3 than st. J1. Among the revealed benthic ciliates, the hypotrichs were the most important group in terms of abundance and biomass. During the sampling periods, an average 66% of benthic protozoa biomass was covered by ciliates. The seasonal distribution of benthic protozoa showed an almost similar fluctuation pattern to that of chlorophyll-a. The results suggest that the biomass of benthic protozoa were mainly controlled by prey abundance, for example, diatoms. Based on ingestion rates, benthic protozoa removed from 13.4 to 40.7% of bacterial production and from 20.1 to 36.4% of primary production. Ingestion rates of benthic protozoa on bacteria and microphytobenthos were high in April. Benthic protozoa in this study area may play a pivotal role in the carbon flow of the benthic microbial food web during spring.

• Journal of Environmental Science International
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• v.19 no.11
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• pp.1323-1336
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• 2010

This study was carried out to determine marine environments and phytoplankton community around Mokpo harbour on March to November during the period of 2004-2009. The remarkable fluctuations of marine environments were shown around Mokpo harbour depending on monthly and yearly. Among seasons, summer was a great that was associated with extremely releasing the freshwater from Youngsan River Weir, contributing to effect the fluctuations of water quality. Nevertheless of monthly and yearly, the molecular ratio of N:P was always shown in above 16 that was mainly attributed to freshwater discharge on March to November. This indicates that phosphorus playes an important role in limiting factor as growth in phytoplankton. During this study, Skeletonema costatum was found to be richer than the other groups of diatoms in terms of abundance and species number. Mokpo harbour, with the presence of a narrow avenue for exchange with offshore waters, has limited growth in phytoplankton, but this species is able to well adapt and fast grow under even high level of suspended solid and low intensity of light compared with other species. The discharge of freshwater is associated with significantly fluctuation of marine environments in this region, but it does not affect the quantitative and qualitative distribution of phytoplankton. It is necessary to persistently monitor based on water quality and phytoplankton community.

• Journal of Aquaculture
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• v.19 no.4
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• pp.236-241
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• 2006

Seasonal variation of the infection by three species of symbiotic copepods in clam, Tresus keenae was investigated in south coast of Korea. The prevalence and abundance of three symbiotic copepods showed seasonal variation with a peak in winter. Reproduction of the copepods occurs from early autumn to spring as indicated by higher ratio of gravid copepods. The frequency distribution of Lichomolgus inflatus, Pseudomyicola spinosus and Anthessius progectus in their host population could be fitted with negative binominal distribution. Results from the present study suggest that seasonal fluctuation in prevalence, relative density and mean intensity is related to temperature and life history of the symbiotic copepods.

• Journal of Fisheries and Marine Sciences Education
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• v.11 no.1
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• pp.98-113
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• 1999

Demersal fishes as second study for the protection-nourishment of fisheries resources in Chinhae Bay were analysed using fish samples collected by a small otter trawler at bimonthly-interval from August, 1997 to June, 1998. Of the 55 species identified, Hexagrammos otakii, Pleuronichthys cornutus, Leiognathus nuchalis, Thrissa koreana, Callionymous lunatus, Acanthogobius flavimanus and Trachurus japonicus predominated in abundance. Especially, Hexagrammos otakii, Pleuronichthys cornutus and Leiognathus nuchalis were always collected at anywhere around a year in the bay. The seasonal fluctuation of number of species is very large as the ranging from 14 species in August to 25, December. The diversity index of individual number and biomass by month and station is 0.68(February)~1.13(October), 0.38(February)~1.06(October) respectively. The indices above mean that the number of species were not distributed broadly over the bay and also concentrated in several species only owing to the local pollutant extent.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.2
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• pp.51-59
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• 2002

The seasonal variation in species composition and abundance distribution of zooplankton was studied in the Seomjin river estuary along the salinity gradients. In this estuary, marine taxa predominated in all seasons and very limited number of freshwater species appeared. The total abundances showed a seasonal fluctuation. The highest total abundance appeared in spring with over 3,000 individuals/m$^3$. In summer, the high abundance was sustained although it decreased a little. The abundance was minimal in fall with about 500 individuals/m$^3$. When the study area was divided into three salinity regimes, oligohaline (salinity less than 5 psu), mesohaline (5${\sim}$18 psu), and polyhaline zone (over 18 psu), the zone of high abundance as well as the composition of zooplankton community in each salinity regime changed seasonally. In fall, marine copepods predominated in oligohaline zone while marine species other than crustaceans dominated in polyhaline zone. However, in winter copepods predominated in all area. In spring and summer, holozoic dinoflagellate Noctiluca scintillans dominated in higher salinity regimes. We listed major copepod species of each salinity regime for each season with the ranges of water temperatures (T) and salinities (S) of their occurrence. T, S's of maximum abundances of those major copepod species were also reported. The observed very wide tolerance ranges of major copepod species for salinity suggested that the concept of 'indicator species' should be used in quantitative context rather than qualitative.

• Journal of Ecology and Environment
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• v.43 no.2
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• pp.104-116
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• 2019

Background: The composition of wild bird populations in temperate zones greatly varies depending on phenological changes rather than other environmental factors. Particularly, wild birds appearing in wetlands fluctuate greatly due to the crossover of species arriving for breeding during the summer and for wintering. Therefore, to understand the changes to species composition related to phenology, we conducted this basic analysis of populations to further the cause of the protection of wetland-dependent wild birds. Methods: It is wrong to simply divide a wild bird population investigation into seasons. This study identifies species composition and indicator species that change along with seasons. Wetlands to be surveyed are protected by natural monuments and wetland inventory and are in a state close to nature. In order to identify as many species as possible in wetlands, a survey was conducted in both shallow and deep wetlands. The water depth varied in these areas, ranging from 0.2 to 2.0 m, allowing for both dabbling and diving ducks to inhabit the area. Surveys were conducted using line-transect and distance sampling methods and were conducted at intervals of 2 weeks. The survey was conducted under the following three categories: the eco-tone and emergent zone, the submergent zone, and the water surface. The survey was conducted along a wetland boundary by observing wild birds. A PC-ord program was used for clustering, and the SAS program was used to analyze the changes in species composition. The data strongly indicates that day length is the main factor for seasonal migration periods, despite the fact that climate change and increasing temperatures are often discussed. Results and conclusions: The indicator species for determining seasons include migrant birds such as Ardea cinerea, Alcedo atthis, Anas penelope, and Poiceps ruficollis, as well as resident birds such as Streptopelia orientalis and Emberiza elegans. Importantly, increases in local individual counts of these species may also serve as indicators. The survey results of seasonal fluctuations in temperate zones shows that spring (April to June), summer (July to September), autumn (October), and winter (November to March) are clearly distinguishable, even though spring and summer seasons tend to overlap, leading to the conclusion that additional research could more clearly identify fluctuation patterns in species composition and abundance in the study area.

• Korean Journal of Ecology and Environment
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• v.45 no.1
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• pp.52-61
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• 2012

Distribution, abundance and biomass of submerged macrophytes were assessed using a double-headed rake and an echo-sounder in the Keumpoong Reservoir to investigate the temporal and spatial variations of submerged macrophytes in a small agricultural reservoir located upstream. Slope steepness and water depth in the littoral zone were important controlling factors on flora and vegetation structure of submerged macrophytes. Biodiversity of submerged macrophytes was increased at a gentle slope of the littoral zone. The results of DCA (detrended correspondence analysis) showed that the structure of submerged vegetation depended on the depth of water. Submerged macrophytes were distributed at the maximum water depth of 2.8 m in the Keumpoong Reservoir. The area occupied by the submerged macrophytes was estimated at only 6% of the total reservoir area because of the steep slope of the littoral zone and the large annual water-level fluctuation of 3.5 m. The increase of water level and inflow of turbid water in the rainy season might reduce the biomass of submerged macrophytes in the reservoir. It may be concluded that submerged vegetation in the Keumpoong Reservoir, a small agricultural reservoir located at the upstream, appears to be particularly susceptible to water level fluctuations and slope steepness of the littoral zone.

• Korean Journal of Ecology and Environment
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• v.40 no.3
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• pp.395-402
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• 2007

Concentrative samplings of 35 times on standing crops of phytoplankton and physicochemical factors were conducted at five sites over Seongsu Bridge to Seongsan Bridge in lower parts of the Ban River from January to December 2006. Over the study, all physicochemical factors showed no large differences among the sampling sites except station 2 having high concentrations of BOD, TN, and TP. Heavy rain also cause these concentrations to decrease. The phytoplankton species and abundance (88 taxa and $1{\sim}41$,104 cells $mL^{-1}$) were varied according to the season, and sharply decreased during heavy rains. In particular, cyanobacteria dominated the phytoplankton community during dry seasons, while green algae and diatom dominated during the rainy seasons. However, after the termination of rain, high water temperatures over $20^{\circ}C$ and low N/P ratios $(9.4{\sim}18.9)$ evoked the cyanobacterial bloom. These results indicate that although the heavy rain (huge outflows of Paltang Dam) temporarily diluted the nutrient level and effected the cyanobacterial bloom in the lower parts of the Han River, cyanobacterial abundance was recovered by the high temperature and low N/P ratio as the rainfall discontinued.