Spatial And Temporal Distribution Characteristics Of Phytoplankton Functional Groups In Hulanhe Wetland

Phytoplankton play a principle component in the wetland ecosystem,as the primary producers,the community,diversity,succession were widely performed in aquantic environment monitoring and water quality assessment.Along the environmental gradients,the structure of algal community,biodiversity,and dominant species present obvious heterogeneity in rivers,lakes and wetlands.Wetland is a complex,open and multifunctional ecosystem with adjusting regional microclimates,storing flood-mitigation and purifying polluted water.Hulanhe wetland is located at the Hulanhe estuary,the north shore of the Songhua River in Harbin,Heilongjiang Province.The wetland is flat,average altitude is 116 m,with a typical temperate monsoon climate;with rich natural resources and high biodiversity.To protect the water ecosystem and biological resources this wetland arein restoration and construction now.At present study,phytoplankton samples were collected at eleven sites in Hulanhe wetland monthly from April to October in both 2018 and 2019.Physical and chemical parameters were monitored at collection time.According to the information of China Remote Sensing Data Network and the actual observations,11 sample sites were divided into four eolgocial regions,including water-inlet area,farmland affected area,wetland protection area and water-outlet area.The changes in phytoplankton composition,dominant species distribution,cell abundance,FG functional groups,and C-S-R growth strategies were studied,the spatial and temporal characteristics of phytoplankton community structure were also analysed.The adaptation of phytoplankton to the water environment and the mechanism of habitat selection were discussed.The correlation between environmental factors and FG functional groups were explored based on Q index and RDA analysis.At last,the water quality of Hulanhe wetland was evaluated comprehensively combined with the biodiversity indexes.The study aims to provide basic data for wetland restoration and protection.The main results are as follows:1.During the study period,the phytoplankton community of Hulanhe wetland was investigated.In total,265 taxa were identified,which belong to 7 phyla,9 classes,18orders,36 families and 93 genera.There are 109 species of Chlorophyta,followed by 65 species of Bacillariophyta,43 species of Euglenophyta,29 species of Cyanophyta,13species of Dinophyta,3 species of Cryptophyta,and 3 species of Chrysophyta.In 2018,the mean phytoplankton abundance in Hulanhe wetland was 70.81×10⁶ ind./L,while46.15×10⁶ ind./L in 2019.2.The results of physical and chemical factors in Hulanhe wetland showed that the mean water temperature?WT?was 19.7°C;the mean pH was 8.39,which indicated the water was alkaline;the mean of the specific conductance?SpCond.?was 346 ms/cm;the mean turbidity?Tur.?was 43.39 NTU;the mean concentration of total nitrogen?TN?was1.01 mg/L;the mean concentration of total phosphorus?TP?was 0.34 mg/L;the chemical oxygen demand(COD_Mn)was 6.30 mg/L;the mean five-day biochemical oxygen demand?BOD₅?was 1.75 mg/L.The study found that the physical and chemical parametershad significantly differenence among time and space.The results of the Trophic State Index?TSI_M?showed that water quality of the Hulanhe wetland was mesotrophic to light eutrophic.3.The diversity indexes were performed to evaluate the water quality of the Hulanhe wetland.The results showed that the range of Margalef index?H?varied from 1.29 to6.55;the Shannon-Weaver index?H'?was from 0.20 to 4.45;the Pielou evenness index?J?showed from 0.04 to 1.13;the range of Simpson?s ecological dominance?D?varied from 0.04 to 0.99;Water quality was evaluated according to the Q index as being generally tolerable or medium;the range of diversity threshold value?Dv?was from 2.48to 6.00;Our results revealed that the water quality of the Hulanhe wetland is between clean to moderate pollution levels.4.During the study period,a total of 26 functional groups were divided according to the classification of the FG,namely B/C/D/E/F/G/H1/J/LM/LO/M/MP/N/P/S1/S2/SN/T/TB/U/W1/W2/X1/X2/X3/Y groups,U-groups were not detected in 2018;There were 12 dominant functional groups,namely B/D/F/J/LO/MP/P/S1/W1/W2/X1/Y;The temporal and spatial distribution of phytoplankton functional groups and C-S-R strategies in Hulanhe wetland have certain regularities.The phytoplankton in the B group and the C-R strategic group occupied dominant positions in most periods and regions.5.The redundancy analysis?RDA?was used to analyze the correlation between the abundance of algae and environmental factors.The results showed that water temperature?WT?,chemical oxygen demand(COD_Mn),total phosphorus?TP?and specific conductivity?SpCond.?were key fatocrs for dynamic phytoplankton composition and functional groups distribution.6.Compared with the results of our prior studies between 2009?2010 and2012?2013,the water quality present in this study is slightly worse.