| Title |
Long-term Water Quality Fluctuations in Daechung Reservoir and the Limiting Nutrient Evaluations Using In Situ Enclosure Nutrient Enrichment Bioassays (NEBs) |
| Authors |
박향미 ( Hyang Mi Park ) ; 안광국 ( Kwang Guk An ) |
| Keywords |
Daechung Reservoir; Empirical linear model; Nutrient enrichment bioassay; Phosphorus |
| Abstract |
The objectives of this study were to elucidate spatio-temporal heterogeneity of water chemistry and develop empirical models using trophic variables in Daechung Reservoir during 2005-2010 along with in situ tests of nutrient enrichment bioassays (NEB). The relations of water quality parameters in regard to precipitation showed that seasonal and interannual fluctuations of biological oxygen demand (BOD), total nitrogen (TN) and pH were minor, whereas conductivity, suspended solids (SS), and total phosphorus (TP) were largely varied in response to the magnitude of rainfall. The CHL maxima occurred immediately after the spate of TP during the high flow, indicating that phytoplankton growth was directly controlled by phosphorus. Empirical linear models of CHL-TP indicated that the variation of CHL in premonsoon was accounted 60% (R2= 0.60, p < 0.05, n=54) by TP. In the mean time, empirical models of annual CHL-TN showed that the variation of CHL was weakly accounted (R2=0.16, p < 0.001) by TN and more strongly (R2=0.44, p < 0.001) by TP. Thus, the variation of CHL was more explained by the variation of TP than TN. In situ tests of Nutrient Enrichment Bioassays (NEBs) showed that the growth of CHL was greater in the P-treatments (as PO4-P) than the control and N-treatment (as NO3-N). Overall, our results suggest that phosphorus was aprimary limiting nutrient controlling the seasonal phytoplankton growth, based on the in situ experiments of NEBs. |