Diurnal variations of pCO(2) in relation to environmental factors in the cascade reservoirs along the Wujiang River, China

We have investigated the diurnal variations of the pCO(2) and related environmental factors in the cascade reservoirs with different trophic levels along Wujiang River. In surface water the pCO(2) was 357 +/- 11 mu atm in Hongjiadu Reservoir, 338 +/- 48 mu atm in Dongfeng Reservoir, 682 +/- 303 mu atm in Wujiangdu Reservoir, and 1677 +/- 429 mu atm in Liuguang, respectively. The results indicated that these cascade reservoirs had much lower pCO(2) values in surface water than river did, and hypereutrophic reservoir showed larger diurnal variations of pCO(2) than meso-eutrophic reservoir. In water column, pCO(2) tended to increase with the depth. Phytoplankton and the environmental factors such as temperature and pH had different influences on pCO(2) diurnal variations due to different trophic levels, and the effect of phytoplankton on pCO(2) variation increased with the increase of trophic level in these reservoirs.