Winter Stephanodiscus bloom development in the Nakdong River regulated by an estuary dam and tributaries

Winter blooms of Stephanodiscus spp. (>85% of total community; mean chlorophyll value of 63.2±67.2 μg l−1) were repeatedly observed in the lower Nakdong River (1994–2001). Diatoms were abundant all year round, except summer (June to September). Four major genera (Aulacoseira, Cyclotella, Stephanodiscus and Fragilaria) accounted for over 70% of the numeric abundance of total phytoplankton. A significant increase in the biomass of this Stephanodiscus occurred in late November, peaking in January to February. Low water temperature, increase of the reservoir's retention time, and low grazing by zooplankton may have allowed development of this diatom species. This diatom declined with the decrease of SiO2,increase of water temperature and high zooplankton density from mid-April. Biological controls act only when physical constraints are alleviated for phytoplankton – here Stephanodiscus blooms.

[1]  G. Joo,et al.  The phytoplankton succession in the lower part of hypertrophic Nakdong River (Mulgum), South Korea , 1998, Hydrobiologia.

[2]  N. L. Huff,et al.  Algae in Water Supplies , 1926 .

[3]  Kent W. Thornton,et al.  Reservoir Limnology: Ecological Perspectives , 1990 .

[4]  G. Joo,et al.  Spatial and temporal dynamics of phytoplankton communities along a regulated river system, the Nakdong River, Korea , 2002, Hydrobiologia.

[5]  M. Dokulil,et al.  Changes of nutrients and phytoplankton chlorophyll-a in a large shallow lake, Taihu, China: an 8-year investigation , 2003, Hydrobiologia.

[6]  G. Joo,et al.  Role of Silica in Phytoplankton Succession : An Enclosure Experiment in the Downstream Nakdong River (Mulgum) , 2000 .

[7]  Gea-Jae Joo,et al.  Microcystis bloom formation in the lower Nakdong River, South Korea: importance of hydrodynamics and nutrient loading , 1999 .

[8]  C. Mervin Palmer,et al.  Algae in Water Supplies of Ohio , 1962 .

[9]  G. Joo,et al.  The phytoplankton succession in the lower part of hypertrophic Nakdong River (Mulgum), South Korea , 1998 .

[10]  M. Grabowska,et al.  Long-term variations of phytoplankton primary production in a shallow, polyhumic reservoir , 2003, Hydrobiologia.

[11]  H. V. Leland.  The influence of water depth and flow regime on phytoplankton biomass and community structure in a shallow, lowland river , 2003, Hydrobiologia.

[12]  Jean-Pierre Descy,et al.  USE OF PHYTOPLANKTON IN LARGE RIVER MANAGEMENT , 1998 .

[13]  David G. Mann,et al.  Diatoms: Biology and Morphology of the Genera , 1990 .

[14]  J. Descy,et al.  Can a community of small‐bodied grazers control phytoplankton in rivers? , 1998 .

[15]  G. Joo,et al.  The longitudinal distribution and community dynamics of zooplankton in a regulated large river: a case study of the Nakdong River (Korea) , 2000, Hydrobiologia.