Seasonal Variations in Primary Productivity and Pigments of Downstream Water of the Han River

한강하류수역의 기초생산과 식물플랭크톤 색소량의 년변화

This study was undertaken to assess the annual cycle of primary production and plant pigments in a downstream of the Han River. Measurements were carried out at three week intervals during April 1966 and March 1967, and ancillary data include water temperature, transparency, pH, dissolved oxygen and phytoplankton cell number. The seasonal cycle in water temperature profile shows the hihgest in the end of August with 27$^{\circ}C$, lowest in the middle of February with 0.2$^{\circ}C$. The transparency with Secchi disk reading varied from a maximum 4.0m in fall and a minimum 0.5m or less in early spring and flood season of summer. The pH of the river water varied from 6.5 to 7.3, averaged 6.91 in the surface water and 6.98 in the bottom water, showed little seasonalvariability. The dissolved oxygen in the surface water ranged from 5.93-9.64ml/L, while in the bottom water it ranged from 5.54-9.72 ml/L, and the oxygen saturation never fall below 94%. None thermal, the distribution of pH and content of oxygen, stratifications occurred. An apparent seasonal cycle of primary productivity was observed with remarkably high levels in the spring and fall, the lowest level in the winter. The range of net carbon assimilations showed 3.1-112.6 mgC/㎥/day or 15-427 mgC/㎡/day in spring, 37.0-271.2 mgC/㎥/day or 115-329 mgC/㎡/day in summer, 27.2-168.0 mgC/㎥ /day or 139-415 mgC/㎡/day in fall and 0.5-10.9 mgC/㎥/day or 5-19 mg/㎡/day in winter, respectively. Amount of chlorophyll ${\alpha}$ ranged from a minimum concentration of 0.2-0.3 mg/㎥ in the middle of February and a maximum 4.1-6.7 mg/㎥ in the middle of June. A general increase trend in chlorophyll ${\alpha}$ concentration was noted with increase of the river water temperature.

천연하천수는 다면적인 용도를 지니는 귀중한 천연자원이다. 선진국가에서의 예를 들지않드라도 우리의 사회생활이 발전함에 따라 물의 용도는 너무나 다양하게 요구되는 것이며, 이로 인한 수많은 오염요소는 물과 그 속의 천연자원을 파괴하는 현상이 현저하게 나타나게 된다. 천연자원은 그 자체가 지니고 있는 속성을 충분히 활용하면서 효과적으로 이용해야 할것이고 또 그 자원은 항구적인 보존책이 강구되어야 할 것이다. 우리나라에도 적지않은 하천수계가 있으나 그 활용은 아직은 미미한 상태에 있다. 하천수를 포함한 내수면의 수산업적이용도 그 중의 중요한 부분을 차지하는 것이니, 각하천수계의 어업생물학적조사, 수질조사를 비롯하여 식용어, 유어자원 또는 유용생물자원의 함양은 시급하게 착수되어야 할 중요한 과제라고 하겠다.