The structure and seasonality of phytoplankton community were investigated in the region of the Naktong River Mouth in 1992-1993 period. The phytoplankton species composition in the main stream of the Nakdong River followed a large lowland and nutrien...
The structure and seasonality of phytoplankton community were investigated in the region of the Naktong River Mouth in 1992-1993 period. The phytoplankton species composition in the main stream of the Nakdong River followed a large lowland and nutrient rich river`s pattern which was dominated by centric diatoms throughout the year and by green algae during the summer. Blue green algae were important in the West-Nakdong stream. The composition of dominant species at the station Dadaepo was quite similar to those found at the freshwater stations Kupo and Eulsukdo. This may be caused by the sampling strategy in which the tidal cycle was not considered and the artificial influence of the physical water mixing process of the opening of the gates on the algal flora. The chlorophyll-a content went beyond the hypertrophic level in the Nakdong River mouth. The values of diversity indices were very low and values of dominance indices were very high. The nutrient concentration in the Nakdong River mouth had shown severe fluctuations in the seasons of before and after barrage construction however, the nutrient concentration has kept high since the year of 1991. The high concentration of nutrient in the Nakdong River mouth may be caused by the waste discharge, stagnation of water, the decomposition of detritus, which was derived from the aquatic macrophytes, the introduction of agricultural fertilizer from surrounding rice field, nitrification and nutrient release from sediment. The characteristic phenomenon in the West-Nakdong stream was the blooming by blue green algae, Microcystis aeruginosa during the summer. Therefore, it is necessary to continuously monitor the phytoplankton community structure in this area throughout season.