YIN Dacong (殷大聪) , ZHENG Lingling (郑凌凌) , SONG Lirong (宋立荣) , **. Spatio-temporal distribution of phytoplankton in the  Danjiangkou Reservoir, a water source area for the South-to-North Water Diversion Project (Middle Route), China.   Chinese Journal of Oceanology and Limnology Vol. 29 No. 3, P. 531-540, 2011

DOI: 10.1007/s00343-011-0120-9

Abstract: One of the water source areas of the South-to-North Water Diversion Project is the  Danjiangkou Reservoir (DJKR). To understand seasonal variation in phytoplankton composition, abundance  and distribution in the DJKR area before water diversion, as well as to estimate potential risks of water  quality after water diversion, we conducted an 

investigation on phytoplankton in the DJKR from August  2008 to May 2009. The investigation included 10 sampling sites, each with four depths of 0.5, 5, 10, and  20 m. In this study, 117 taxa belonging to 76 genera were identified, consisting of diatoms (39 taxa), green  algae (47 taxa), blue-green algae (19 taxa), and others (12 taxa). Annual average 

phytoplankton abundance  was 2.01×106  ind./L, and the highest value was 14.72 × 106  ind/L (at site 3 in August 2008). Phytoplankton  abundance in front of the Danjiangkou Dam (DJKD) was higher than that of the Danjiang Reservoir Basin.  Phytoplankton distribution showed a vertical declining trend from 0.5 m to 20 m at most sites in August  2008 (especially at sites of 1, 2, 4 and 10), but no distinct pattern in other sampling months. In December  2008 and March 2009, Stephanodiscus sp. was the most abundant species, amounting to 55.23% and  72.34%, respectively. We propose that high abundance of Stephanodiscus sp. may have contributed greatly  to the frequent occurrence of Stephanodiscus sp. blooms in middle-low reaches of the Hanjiang River  during the early spring of 2009. In comparison with previous studies conducted from 1992 to 2006, annual  average 

phytoplankton density, green algae and blue-green algae species, as well as major nutrient  concentrations increased, while phytoplankton diversity indices declined. This 

indicates a gradual decline  in water quality. More research should be conducted and countermeasures taken to prevent further  deterioration of water quality in the DJKR.

Keyword: Danjiangkou Reservoir; phytoplankton; South-to-North Water Diversion Project;  eutrophication