Characteristics of a landscape water with high salinity in a coastal city of China and measures for eutrophication control

Eutrophication of landscape waters is drawing public concerns in China but few studies have been conducted on the problem associated with high water salinity as what happens at Sino-Singapore Tianjin Eco-city in Tianjin, a coastal metropolis of northern China. In order to find ways for eutrophication control, a comparative study was conducted on three landscape water bodies, namely Qingjing Lake, Jiyun River and Jiyun River Oxbow, which are under varied conditions of salinity, organic, and nutrients intrusion. The spatial and temporal variations of water quality were revealed by water sampling and analyses, and correlative relationships were obtained between water salinity and other parameters related to eutrophication. By utilizing a trophic level index (TLI), the eutrophication status of the three landscape water bodies in different seasons could further be evaluated. As a result, water temperature, as expected, showed the strongest effect on eutrophication because higher TLI together with higher Chl-a concentrations tended to occur in later spring and summer seasons, while nutrient concentration, especially TP, was also the determinative factor to the eutrophication status. Of the three water bodies, the Jiyun River Oxbow showed a salinity as high as 20 g/L or more in contrast with the other two water bodies with salinity as 4-5 g/L. Although its TP concentration was usually very low (about 0.1 mg/L), it was under a moderate eutrophication status almost in all seasons, indicating that high salinity tends to induce alga growth. Dilution of saline inflow and nutrients reduction could thus be proposed as the main measures for eutrophication control of landscape waters in the study area.