한강하류의 환경학적 연구 - Ⅱ. 식물플랑크톤의 동태 -

Abstract

This study on the seasonal dynamics of phytoplankton was conducted between June of 1995 and 1996 during the dry season at 7 stations along the lower part of the Han River. During this study, a total of 145 taxa of phytoplankton were found, including 82 diatoms, 50 green algae, 7 bluegreen algae, 3 euglenoids and 1 species each of dinoflagellate, chrysophyte and silicoflagellate. Though the seasonal fluctuations in phytoplankton standing crops were very wide and recorded a minimum of 3.2×10^5cells/ℓ(July 1995, st.3) and a maximum of 1.5x10^7cells/ℓ(June 1996, st. 3), during the flood period, excluding July, more than 10^6∼10^7 cells/ℓof annual blooms were recorded. Five representative species were recorded by all stations as appearing every month in the surveyed area including Asterionella gracillima, aulacoseira granulata, Fragilaria crotonensis, Synedra ulna and Scenedesmus longispina, Aulacoseira granulata, Fragilaria crotonensis, Synedra granulata, A. granulata var. angustissima f. spiralis, A. italica, Asterionella gracillima, Fragilaria crotonensis, Stephanodiscus hantzschii f. tenuis and Stephanodiscus parvus, it was the first dominant species, in particular, that occupied the highest ratio. Though the dominance index and the inverse proportion of the species diversity index of phytoplankton com-munities was very low, the ratio occupied by the standing crops, number of occurring species, and dominant species was accompanied by a great deal of variation in the evenness index. In addition, even though there is a direct relationship between the richness index and the total number of occurring species, if the standing crops variation is large, the richness index will show a large variation in the same number of occurring species.