Abstract: This paper dealt with the effects of increasing salinity and alkalinity on the chemical and hydrobiological factors in saline alkaline ponds.The experiment was conducted in Daluhu Aquaculture Company,Gaoqing County,Shandong Province during July and August,1998.Raw salt and NaHCO_-3 were used to adjust the salinity and alkalinity.The results showed that increasing alkalinity from HCO_-3^- rsulted in the reduction of pH value,calcium ion concentration and COD in a short term.When alkalinity was increased from 6.64?0.40 to 13.47?0.31 mmol稬^-1,no significant effect on plankton was observed. However,when salinity was increased from 2.10?0.22 to 11.29?0.99 g稬^-1,it decreased the plankton biomass,species number and diversity index decreased,and affected the composition of plankton community structure.

Key words: Saline-alkaline ponds, Salinity, Alkalinity, Plankton