Environmental Studies in the Lower Part of the Han River VIII. Physicochemical Factors Contributing to Variation of Phytoplankton Communities

To reveal physicochemical factors contributing to variation of phytoplankton communities, the study was carried out biweekly at 6 stations from Feb. 2004 to Feb. 2005 in the lower part of the Han River, Korea. As results, water temperature was changed from $0.3^{\circ}C$ to $26.6^{\circ}C$, pH: 6.6${\sim}$9.1, DO: 1.89${\sim}$22.23 mg $L^{-1}$, BOD: 0.38${\sim}$9.20 mg $L^{-1}$, COD: 1.4${\sim}$15.2 mg $L^{-1}$, Conductivity: $62.5{\sim}500.0\;{\mu}s\;cm^{-1}$, SS: 3.00${\sim}$159.3 mg $L^{-1}$, and Chl a $1.7{\sim}71.3\;{\mu}g\;L^{-1}$. Phytoplankton standing crops ranged from min. $3.6{\times}10^2\;cells\;mL^{-1}$ (July 2004, St. 3) to max. $2.3{\times}10^4\;cells\;mL^{-1}$ (Feb. 2005, St. 6), and mean of those varied from $5.9{\times}10^3\;cells\;mL^{-1}$in spring, $2.1{\times}10^3\;cells\;mL^{-1}$ in summer, $4.1{\times}10^3\;cells\;mL^{-1}$ in autumn and $8.5{\times}10^3\;cells\;mL^{-1}$ in winter, respectively. In order to investigate factors influencing the total phytoplankton standing crops a multiple regression analysis was adopted for the correlation between standing crops and environmental factors. The coefficient of determination ($R^2$) value of the regression was 0.465, it showed that environmental factors which predominantly influenced phytoplankton standing crops were water temperature, COD, $NO_2-N$, $PO_4-N$, Discharge and pH. six stations could be divided into 3 groups based on similarity index in terms of environmental factors. In ANOVA analysis for physicochemical and biological factors, water temperature, chlorophyll a, silicate, phytoplankton standing crops were the same group differed little from stations. However, Station 1and 2 were grouped followed in dissolved oxygen, conductivity, COD, nitrite, nitrate, ammonia and phosphate, and Station 3, 4 and 5 were followed in dissolved oxygen, conductivity, pH and phosphate.

한강 하류의 환경학적 연구 VIII. 식물플랑크톤 군집의 변화에 미치는 물리 화학적 요인

2004년 2월부터 2005년 2월까지 1년 동안 매 격주간 한강하류역의 6개 정점에서 식물플랑크톤군집에 미치는 물리화학적 환경요인을 조사하였다. 조사결과 수온은 $0.3{\sim}26.6^{\circ}C$, pH: 6.6${\sim}$9.1, DO: 1.89${\sim}$22.23 mg $L^{-1}$, BOD: 0.38${\sim}$9.20 mg $L^{-1}$, COD: 1.4${\sim}$15.2 mg $L^{-1}$, Conductivity: $62.5{\sim}500.0\;{\mu}s\;cm^{-1}$, SS: 3.00${\sim}$159.3 mg $L^{-1}$, chlorophyll a $1.7{\sim}71.3\;{\mu}g\;L^{-1}$ 범위로 변화하였다. 식물플랑크톤 현존량은 최저 $3.6{\times}10^2\;cells\;mL^{-1}$ (2004년 7월, 정점 3)에서 최고 $2.3{\times}10^4\;cells\;mL^{-1}$ (2005년 2월, 정점 6)까지 변화하였으며, 계절별 평균 현존량은 봄철에 $5.9{\times}10^3\;cells\;mL^{-1}$, 여름철 $2.1{\times}10^3\;cells\;mL^{-1}$, 가을철 $4.1{\times}10^3\;cells\;mL^{-1}$, 겨울철에 $8.5{\times}10^3\;cells\;mL^{-1}$로 겨울철에 가장 높았다. 식물플랑크톤 현존량에 미치는 환경요인의 영향을 규명하기 위하여, 종속변수인 현존량과 독립변수인 환경인과의 단계적 중회귀 분석을 한 결과 $R^2$=0.465였으며, 그 중 중요한 요인은 수온, COD, $NO_2-N$, $PO_4-N$, 유량, pH로 나타났다. 6개 정점을 환경요인을 매개변수로 유사도 분석을 한 결과 크게 3개 group으로 나눌 수 있었으며, 물리 ${\cdot}$ 화학적 환경요인과 생물학적 요인을 대상으로 ANOVA 분석에서는 수온, chlorophyll a, 규산염, 식물플랑크톤 현존량은 정점간 차이가 없이 하나의 group이었으며, 용존산소량, 전기전도도, COD, 아질산염, 질산염, 암모니아염, 인산염이 정점 1, 2에서 같은 group으로, 용존산소량, 전기전도도, pH, 인산염이 정점 3, 4, 5에서 같은 group으로 묶였다.