For four times, zooplankton collection were conducted seasonally in October 2015- July 2016 at five sites located in the wet lands of the lower Han River, ie., Si-am, Sung-dong, Gong-reung stream, San-nam and Jang-hang. A total of 46 species of zooplankton were collected, which comprise 25 species of rotifers, seven cladocerans, ten copepods, and one species of nematod, ostracod and decapod, respectively. No brackish and marine species were distributed except for two species of brackish water copepods. Prosperity in the species number of 15 species was observed in October at Sung-dong and Jang-hang. The maximum abundance was recorded in March at Si-am with 8,000 indiv. L-1 with the explosion of Brachionus calyciflorus. Other sites also showed high abundances in March with the abundance higher than 5,000 indiv. L-1. Except in March, the abundance levels were recorded as less than some hundred indiv. L-1 throughout the study. Species diversity varied between 0.4-1.8. The gut contents of the copepodite showed that various diatoms might be their major food items, and lots of unidentified materials were also observed. The environmental conditions of water temperature, pH and dissolved oxygen content showed to vary 10.1-28.2°C, 7.1-8.6 and 4.5-11.0 mg L-1, respectively.

Nonylphenol is one of endocrine disruptors, as structurally stable, hydrophobic compounds exhibit high condensability and long-lasting in the natural environment. The purpose of this study was to determine the toxic effects of nonylphenol on Daphnia magna. In acute toxicity test, D. magna was exposed for 48 h at concentrations of 0, 10, 18, 32, 56 and 100 μg L-1 nonylphenol. In chronic toxicity test, D. magna were exposed through water for 21 days at concentrations of 0, 1.0, 1.8, 3.2, 5.6 and 10 μg L-1 nonylphenol. Acute toxicity was assessed on the basis of immobility, while chronic toxicity was assessed on the basis of fecundity. The acute toxicity test on nonylphenol was showed that the values of 24 h and 48 h EC50 were 25.0 μg L-1 and 13.7 μg L-1, respectively. In chronic test, fecundity was reduced significantly at 5.6 μg L-1 of nonylphenol. These results indicated that nonylphenol have some hazard for acute or chronic toxicity to freshwater invertebrate organism.

춘계 영월 한반도습지 주변 유수역의 동물플랑크톤 군집 동태 연구를 위하여 2014년 3월부터 7월까지 3개 정점에서(정점 1: 영월 서강, 정점 2: 평창강, 정점 3: 주천강) 4회의 동물플랑크톤 시료를 채집하였다. 총 58종류의 동물플랑크톤이 출현하였으며 27종의 윤충류, 18종의 지각류, 8종류의 요각류, 4종류의 수서곤충 유생 및 한 종류의 선충류로 이루어져 있었다. Alona속의 종들과 같은 씨물벼룩과에 속하는 지각류가 다양하게 출현하였고 정수역 대표종들인 물벼룩과와 긴뿔물벼룩과의 지각류가 미출현한 것은 조사 수역의 유수성을 보여준다. 동물플랑크톤 출현량은 정점 3에서만 입방미터당 4,451~ 8,011개체로 높았고 나머지 정점들에서는 500개체를 넘지 않았다. 정점 1에서 3월부터 6월까지는 수서곤충의 유생이 우점하다가 7월에는 지각류와 요각류의 우점으로 천이가 이루어졌으며 유사한 천이가 정점 3에서도 관찰되었으나 정점 2에서는 이러한 천이가 없었다. 종다양성지수는 3월을 제외하면 정점 1에서 항상 높게 나타났다. 조사 기간 내내 높은 용존산소량은 (9.0~11.0 mg·liter-1) 산간 계류의 특성을 보이는 것이며 수온은 3월에 10.1°C에서 7월에 27.9°C로 서서히 증가하였고 높은 pH는 (7.9~ 8.9) 조사 수역 주변의 석회석 광산과 시멘트 공장의 영향으로 추정된다.

Pre-monsoon dynamics of zooplankton community were investigated in the downstream of the Gagok stream flowing into the East Sea of Korea. Monthly sampling was carried out to collect zooplankters at five sites in the stream during the period between April and July 2014. Dissolved oxygen contents exceeded 7.0 mg L-1 all the time. Water temperature was in a range of 15.7 to 24.9˚C and pH 7.4 to 8.8, respectively. A total of 75 taxa consisted of 36 species of rotifers, 16 species of cladocerans, 16 species of copepods, four kinds of aquatic insects, two kinds of decapods and one nematod was occurred. One species of marine copepod and one cladoceran, and one species of brackish rotifer and one copepod distributed at the station located in the stream mouth. Zooplankton abundance showed to vary from 42 to 4202 individuals m-3 due to the explosion of aquatic insects and Alona sp. at site 2 located in the downstream in April. Heavy rainfall during the monsoon period seems to decrease the zooplankton abundance caused by diffusion and drifting to the sea. Species diversity indices were generally high between 1.2~2.3 and were recorded to be high at the downstream throughout the study period. With the zooplankton dynamics, the influence of the input of sea waters into the stream seemed to be confined to some hundred meters of the stream mouth facing the East Sea.

A Study on zooplankton fauna and phytoplankton flora was carried out three times in June, August and September 2012 at the Hyuncheon wetland in Gangwon-do, Korea. A total of 14 taxa of zooplankton were distributed, which consisted of six rotifers, four cladocerans, two copepods, one nematode and one aquatic insect larvae. Occurrence of Simulium japonicum supports that studied water is the first grade clear water. It was observed that the abundance of zooplankton was never exceeded over 55 ind.L-1. Rotifers dominated in the months of June and August, whereas cladocerans in September, respectively. The phytoplankton flora was consisted of 26 species. The standing crops varied between 4,080~10,120 cell.L-1. Docidium undulatum is the typical species distributed in muddy wetland and Closterium acerosum is distributed widely from wetlands through lakes. Navicula spp. and Nitzchia spp. were recorded to be distributed in lentic waters of big lakes such as Paldang Lake. Species diversity indices decreased gradually from June to September between 1.3~1.9 in zooplankton but lowest in August between 0.9~1.6 in phytoplankton, respectively. Based on my study observation, I anticipate that the poor distribution of zooplankton, phytoplankton, and low values of species diversity index are likely to be a cause of narrow area with shallowness of waters during the short period.

Zooplankton dynamics were investigated based on samples collected monthly during the period between November 1998 and October 1999 at 15 stations in Gwangyang and Sachon Bay. Zooplankters were quantitatively collected with horizontal towing through the su