An investigation was carried out in Anbang River wetland,a type of high frigid swamp,from July 2005 to May 2006.Phytoplankton diversity of 104 taxa,belonging to Chlorophyta (49),Cyanophyta (25),Bacillariophyta (18),Chryso-phyta (4),Euglenophyta (3),Xanthophyta (2),Cryphophyta (2),and Pyrrophyta (1),were found.There were 17 eu-trophic taxa,34 mesotrophic taxa and 25 oligotrophy species were indentified in the studied period.Typical trophic indicators,such as Aphanizomenon flos-quae,Microcystis aeruginosa,Melosira granulate,and so on,which are usually associated with eutrophic environments,were monitored and were the dominant species in 1#,5#,9# sampling stations,with ratios of 51.31％,58.28％,and 53.37％,respectively.Trophic taxa showed that the trophic status of Anbang river wetland was meso-trophers.Total mean abundance was 183.32 × 104 ind · L-1 and biomass was 2.92 mg · L-1,respectively,with an order of temporal distribution of abundance and biomass summer ＞ autumn ＞ spring.The abundance of sampling stations were from 42.12 × 104 ind · L-1 to 178.53 ×104 ind · L-1 in spring,at 98.04 × 104～396.57 × 104 ind · L-1 in summer,and at 58.45 × 104～323.93 × 104 ind · L-1 in autumn,biomass in spring from 1.21 mg · L-1 to 3.02 mg · L-1,in summer at 2.57-4.80 mg · L-1,and in autumn at 1.34-4.35 mg ? L-1.Based on the criteria of trophic status in phytoplankton in China; (1) abundance ＜3 × 105 ind · L-1 or biomass at 1-1.5 mg · L-1 is oligotropher; (2) abundance at 3 x 105～10 × 105 ind · L-1 or biomass at 1.5-5 mg · L-1 is mesotrophers; (3) abundance ＞ 10 × 105 ind · L-1 or biomass ＞5 mg · L-1 is eutropher.There was differentia in trophic status based on the abundance and biomass.Results of abundance showed it was mesotrophers & eutropher,but biomass was mesotrophers except 8# and 10# sampling stations.Biomass of Bacillariophyta was dominant in spring (62.16％),autumn (41.30％),and mean (40.75％),only in summer was non-dominant species (27.59％),merely ＜ Chlorophyta (33.95％),revealed the phytoplankton community was Bacillariophyta type,was mesotrophers.Diversity index is a useable method in evaluating water trophic starus.Species number,Margalef's index,Shannon-Veaner' s index and Pielou' s index were collected.Correlation analysis between the species number and Margalef's index in Anbang River wetland indicated that had a positively significant correlation (Spearman r =0.988,n=30,P＜0.001),Shannon-Veaner,s index had a positively significant correlation with Pielou's index ( Spearman r = 0.875,n = 30,P ＜ 0.001),there was no significant correlation between other diversity indexes (P＞0.05,n=30).Therefore,Margalef's index and Shannon-Veaner's index were collected to measure phytoplankton community diversity.However,Margalef's index is strongly correlate to rare species,and the results maybe error,in contrast,Shannon-Veaner's index is one of best diversity index,which can be preferably reflect the phytoplankton community structure.Shannon-Veaner's index indicated that in spring there were 9,in summer 4,and in autumn 8 sampling stations,which value ＞3.30,showed most of sampling stations were oligotrophic water,not same as the indicator species and biomass estimation,based on abundance.Shannon-Veaner' s index based on biomass suggested that 3#,4#,6#,8# in spring,and 4# in autumn ＞3.30,were oligotrophic,other between 0.93 and 3.30,were mesotrophers,sustained results of indicator species and biomass evaluation.Phytoplankton compositions are affected by different environmental factors such as nutrient,pH,light,temperature,and so on,so trophic status should be monitored by vary methods.Trophic level indexes (TLI) based on chlorophyll-a (Chl-a),total nitrogen (TN),total phosphorus (TP),and secchidisk depth (SD) were conducted,TLI between 30 and 50 in all sampling stations in three seasons,and 5#,9# sampling stations in summer,which TLI were 49.459 and 49.731,nearly the eutrophic status.TLI demonstrated that water in Anbang river wetland was mesotr-phic,were likely to maintain the results of phytoplankton.In summary,water quality was well,belonging to mesotrophic,but had the potential to eutrophication.Though water trophic status assessment based on phytoplankton may seem clear enough,it served as a valuable example for the future monitoring of the Anbang River wetland water quality.
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