초록 열기/닫기 버튼
Phytoplankton is one of the important primary producers providing organic matter through photosynthesis in aquatic environments. In order to determine a temporal and spatial variation in primary productivity after weir construction in the Nakdong River, we investigated carbon uptake rates using in-situ 13C labeling experiments and identified algal communities contributing to primary productivity using HPLCCHEMTAX analysis from October to December, 2017. The primary productivity gradually decreased from fall to early winter season (249~933 mgC m-2 d-1 in October, 64~536 mgC m-2 d-1 in November and 60~274 mgC m-2 d-1 in December, respectively). This is attributed to the temporally declining light intensity and the decreasing biomass and physiological activity of phytoplankton in winter. The contribution of diatoms to the phytoplankton community in the Nakdong River was approximately 63% at all the sampling sites and seasons, while the contribution of cryptophytes increased from 9% in October to 32% in November and December. The temporal changes in the primary productivity and the dominant phytoplankton species in the mid and downstream weirs of the Nakdong River was investigated for the first time, after construction of the weirs, and major environmental factors controlling the temporal variation in primary productivity and phytoplankton communities were identified in this study. We suggest that seasonal field investigations will provide further information on the major environmental factors which affect the annual variation of primary productivity and phytoplankton communities.
