Algae. 2001; 16(2): 165-177.

Changes in Marine Environment and Primary Production due to Freshwater Input in the Nakdong Estuary

Sung Ryull Yang, Hwan Seok Song, Chang-Ho Moon, Kee-Young Kwon, Han-Seob Yang

Division of Civil and Environmental Engineering, Kwangju University, Department of Oceanography, Pukyong National University, Korea
Inter-University Institute of Ocean Science

Physico-chemical factors and primary productivities were measured during the dry (May, 2000) and wet (July, 2000) seasons in the Nakdong estuary to investigate the effects of freshwater input. Water column transparencies, one of the major factors controlling primary productivity, were mainly affected by the shallow depth, tidal mixing and freshwater input. Nutrient concentrations were low during the dry season, excess nutrients, especially nitrogen, were observed during the wet season associated with the input of freshwater into the estuarine area. The major sources of nutrients in the estuary seemed be the river water and the inflow from nearby Jinhae and Dadaepo areas. Primary productivities ranged between 0.3 and 103.4 mg·C·m super(-3)·hr super(-1) showing high variabilities among stations and between seasons. The average value was 55.8(±29.2) mg·C·m super(-3)·hr super(-1) during the dry season, and 16.4(±22.3) mg·C·m super(-3)·hr super9-1) during the wet season. Freshwater phytoplankton biomass occupied 22.8% and 73.8% of total phytoplankton biomass for the dry and wet seasons, respectively. Freshwater input through Nakdong river caused a drastic decrease in salinity, excess nutrient input and increase in suspended matter, which resulted in the changes in phytoplankton composition and a large decrease in primary productivity in the estuarine area.

Keywords : freshwater input, in vivo fluorescence, Nakdong estuary, primary production