• The Korean Journal of Quaternary Research
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• v.32 no.1_2
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• pp.1-29
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• 2018

We investigated the seasonal variation of diatoms from the modern bottom floor sediments of the reservoirs distributed in the southern part of the Korean Peninsula. The studied reservoirs include each three reservoirs from Southeastern part, Central Southern part and Southwestern part, respectively, to compare the dominant diatom assemblages that are ecologically controlled by local environments. In the Southeastern region, Aulacoseira spp., Fragilaria crotonensis, Fragilaria tenera, Gomphonema gracile, G. parvulum and Gyrosigma attenuatum were dominant species. Aulacoseira spp., Cymbella tumida, Cymbella turgidula, Diploneis finnica and Fragilaria crotonensis were dominant taxa in the Central Southern regions. In the southwestern region, Aulacoseira spp., Fragilaria crotonensis, Gomphonema parvulum and Stenopterobia curvular were predominated. Of which Aulacoseira spp. were predominant species at all reservoirs. In addition most of dominants are saproxenous taxa living in the clean water area, and the water quality of these reservoirs is considered to be less polluted water. As a result of seasonal comparison of diatom productivity, the first productivity is higher in summer than in winter. However, diatom valve abundance in the southeastern reservoirs was fewer from the samples collected at May than February.

• Journal of the Korean earth science society
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• v.42 no.6
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• pp.677-687
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• 2021

In this study, we analyzed diatoms from core RS15-GC41 collected in Iselin Bank, Ross Sea. A total of 24 genera and 35 species of diatoms are identified, and the having valve abundance of diatoms varies from 0.2 to 28.6×10⁶/g. Four diatom assemblage zones are established by the vertical distribution of diatoms, and changed with a cycle of 100 kyrs. RS15-GC41 were deposited over the last 400 kyrs (corresponding to Marine Isotope Stages 1-11). The open-water species Fragilariopsis kerguelensis, Rhizosolenia styliformis, and Thalassionema nitzschioides abundantly occurred in interglacial periods. Whereas, Actinocyclus actinochilus abundantly dominant during the glacial periods. The distribution of these diatoms indicated, it can be seen that the sea-ice extent was larger and lasted longer during MIS 7, 9, and 11 than that of MIS 1, 3, and 5. Moreover, Paralia sulcata was abundantly predominant in MIS 7, 9, and 11; this finding suggests likely indicating that P. sulcata was transported from the coastal/inner shelf area to the study site, during accumulated in the sediments, reworked with the influx of ice-rafted debris by the currents