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To support the basic data for forecast of algal blooms, circadian vertical migration experiment was carried out in the Daning River Bay of the Three Gorges Reservoir in July, 2011. The results were as follows: in this period, different algal species were found in the Daning River Bay, including cyanobacteria, green algae, dinoflagellates and diatoms etc; the distribution of algal cells was uneven, 72.5%-76.2% of algal cells aggregated at 0.5-4.0 m water depths from 10:00 AM to 10:00 AM next day, but 7.5%-16.3% of algal cells aggregated at 0-0.5 m. Morisita's indexes (MI) of algal cells were from 1.41 to 1.97 in day time, and from 1.17 to 1.55 at night. Morisita's indexes of chlorophyll a(Chla)were from 1.31 to 1.59 in day time, and from 1.17 to 1.39 at night. The vertical migration also occurred at 0.5-4.0 m water depths. The algal density was not significantly related with the concentrations of nutrient except that of dissolved total phosphorus (DTP) (r = 0.89). The algal density was also influenced by water temperature (WT), pH and specific conductance (SPC), and the correlation coefficients were 0.96, 0.97 and -0.99, respectively.

The contents of different phosphorus forms in surface sediments and the soils of water-level-fluctuating zone of the backwater reach from input river of Three Gorges Reservoirwere measured, using thestandard measurement and test (SMT) procedure of phosphorus forms in freshwater sediments. Correlation coefficients between phosphorus forms and sample geochemical characteristics, such as organic matter and major components were analyzed. The results indicated that the TP content in surface sediments varied from 483.4-848.4 mg/kg, and the average content was 569.0 mg/kg. The TP content in surface sediments placed in the mid-lower level, comparing with the TP content in surface sediment from the shallow lakes in the middle and lower reaches of Yangtze River. The TP content in soils of water-level-fluctuating zone varied from 488.9-1487.7 mg/kg, and the average content was 813.3 mg/kg. The average content of TP in soils of water-level-fluctuating zone whole exceeded the surface sediment, indicating of the influence of human's activity on phosphorus contents in soils of water-level-fluctuating zone. Distribution characteristics of phosphorus forms were different between the sediment and soils of water-level-fluctuating zone: (1) The ratio of IP/TP in the surface sediments (average value 55.7%) was higher than that in soils of water-level-fluctuating zone (average value 49.4%); (2) The domination phosphorus forms of IP in surface sediments was Ca-P (average ratio 83.5%), and the ratio of (Fe/Al-P)/IP was only 15%. The average ratio of Ca-P/IP in the soils of water-level-fluctuating zone was 73.9%, whereas the ratio of Fe/Al-P in IP raised to 22%; (3) The average content of active phosphorus (OP + Fe/Al-P) in surface sediment was 261.8 mg/kg, the average ratio of active phosphorus in TP was 49%, whereas the average content of active phosphorus (OP + Fe/Al-P) in soils of water-level-fluctuating zone was 405.7 mg/kg, the average ratio was 54%. The active phosphorus in soils of water-level-fluctuating zone would become potential pollution sources of water under correct environmental conditions,therefore, the potential impact of phosphorus on water eutrophication in soils of water-level-fluctuating zone couldn't be neglected.

The seasonal characters of the water flux and suspended substance, phosphorus in the water of input rivers of Three Gorges Reservoir (TGR) were discussed, and the their distributions among three major input rivers (Changjiang river, Jialingjiang river and Wujiang river) were studied, according to the survey conducted from Jan. 2004 to Dec. 2005. The results indicate that those parameters' seasonal changes are obvious. The flux and suspended substance in abundant water period are more higher than them in low water period, which displays suspended substance origins from bedload and that the water and soil severely lose in drainage areas of three input rivers. In the three monitor sections of input rivers of TGR, the average contents per year of total phosphorus are about 0.12-0.29 mg/L, which exceeds the 1970s level of the three input rivers. Most of total phosphate is total solid phosphate (TPP) exceeding 75% of them. TP and TPP have both distinct positive correlation with the flux and suspended substance in water of input rivers of TGR, and TPP and TP have also the same correlation, which means that phosphate pollution in the input rivers of TGR comes from bedload. The nonpoint source pollution has had far-reaching influence upon phosphate pollution. Nitrogen and phosphate are not the major limiting factor of the nutritious salts in the input rivers of TGR. The rate of between nitrogen and phosphate (N/P) is in higher level (above 30), that is phosphate first will reach lower level and maybe become the limiting factor of the nutritious salts in the input rivers of TGR.

TP, TN, chlorophyll a, potassium permanganate index and secchi depth (SD) and phytoplankton were determined in 15 tributaries of Three Gorges Reservoir. Trophic states were assessed and output fluxes of TN, TP and potassium permanganate index were calculated. The results showed that value of TN, TP, potassium permanganate index, SD and Chla were different in each tributary. SD, TN, TP, potassium permanganate index and Chla value are 0.45 - 1.5 m, 0.65 - 4.27 mg x L(-1), 0.011 - 0.432 mg x L(-1), 0.657 - 5.37 mg x L(-1) and 0.57 - 12.2 mg x m(-3) respectively. The water body of tributaries is polluted at various levels. The concentration of TN is abundant. The rate of TN and TP showed that a part of tributaries eutrophication are limited by TP. Utilizing the method of integrated nutrition state index, it assessed the trophic states degree of tributaries. All of the studied tributaries, 3 tributaries are eutropher, 10 tributaries are mesotropher and 2 tributaries are oligotropher respectively. 129 species of phytoplankton are identified, which belongs to 7 division and 67 genera. The dominant species are Bacillariophyceae, Chiorophyceae and Cyanophyta. The type of phytoplankton community is Bacillariophyceae-Chlorophyceaetype, Bacillariophyceae-Cyanophytatype and Cyanophyta-Chlorophyceaetype. The species and numbers of phytoplankton are various in different tributaries. The nutritive peculiarity belongs to responding type of phytoplankton. The nutrient fluxes load was calculated by discharge and concentration of each tributary. The nutrient fluxes load of TN, TP and potassium permanganate index are 3.14 x 10(5) t, 1.76 x 10(4) t and 2.74 x 10(5) t respectively in one year. After the Three Gorges Dam was completed in 2009, eutrophication trend of tributaries estuaries would be more serious with the decreasing of flow velocity.

The local condition and the historical evolvement trend of nutrient elements were studied by the collection and analysis of the local investigation and the historical data. The surface seawaters are under the bad nitrogen contaminative conditions. Beitang and Dagu estuary are the main contaminative sources of inorganic nitrogen and phosphorus. The historical evolvement trend of DIN and DIP has close correlation with the yearly runoff, especially in the coastal areas near Dagu estuary. The remarkable positive correlationship between DIN, DIP and the yearly runoff indicates that the main pollution emission source of nutrient elements is the exogenous discharge input. The nutrients structures have changed greatly from 1985 to 2003. Nitrogen limiting in 1985 has changed into phosphorus limiting in 2003, which will influence the structure of phytoplanktons in Bohai Bay.

The characters of the morphological, vertical and spatial distribution of nitrogen and phosphate in the water of Changjiang Estuary were discussed, according to the survey conducted in November 2003. Among the dissolved inorganic nitrogen species, nitrate accounted for 90% in the water of Changjiang Estuary. The concentration of nitrogen nutrients in the Changjiang Estuary show higher level, and 67% of sampling stations attained or exceeded the forth standard level of seawater, according to the national standard of seawater quality. Most of total phosphate in the water of Changjiang Estuary is total dissolved phosphate (TDP), which primary composition is dissolved organic phosphate (DOP). The dramatic changes of salinity in the water of Changjiang Estuary lead to the different distribution characteristics of nutrients. The concentrations of nitrate are higher inside the estuary and lower outside the estuary due to its conservatism. On the contrast, ammonium and phosphate are influenced by the change of particle concentrations and salinity, which are higher outside the estuary and lower inside the estuary. Besides, the contents of COD in the water of Changjiang estuary are very high, and the spatial distribution characteristics are higher inside the estuary and lower outside the estuary.