Tang Xiangming

Comparison of the abilities of three artificial substrates in purifying eutrophic waters

The abilities of three artificial substrates( solid filler,bio-cord and nylon gauze) on purifying the eutrophic waters were compared in relation to the biotic and abiotic influencing factors based on a field microcosm experiment in Meiliang Bay of Lake Taihu. The results were as follows:( 1) all of the three artificial substrates could significantly reduce the water turbidity. In comparison,water turbidity of the nylon gauze treatment group decreased by 94. 2%,which was the highest decrease by per unit mass substrate( 36. 18 NTU /g);( 2) comparing with the control group,the growth of algae in all three treatment groups were significantly inhibited;( 3) the removal amounts of total nitrogen and phosphorus by the artificial substrates were significantly different among the three treatment groups respectively,with a 25. 55%,10. 21%,51. 54% accumulative removal of total nitrogen,and a38. 93%,38. 33%,62. 98% accumulative removal of total phosphorus for the solid filler,bio-cord and nylon gauze,respectively;and( 4) substrate physicochemical characteristic,biomass and activity of periphytic algae and bacteria,substrate quantity,and the releasing of dissolved nutrients attached on substrates are the key factors affecting the abilities of artificial substrates to purify eutrophic waters. In conclusion,nylon gauze has advantages over the other two substrates with high biomass and microbial activity by per unit mass periphyton,less dissolved nutrients attached on itself,lighter weight and cheaper price. Hence we suggest that nylongauze is an ideal artificial substrate in purifying eutrophic waters.

Phytoplankton absorption and chlorophyll-specific absorption coefficients characteristics of different trophic level lakes

Phytoplankton absorption and chlorophyll-specific absorption coefficients were analyzed,and the causes were discussed by selecting four different trophic level lakes including Lake Taihu,Lake Tianmu and Lake Bositeng.According to trophic level index using chlorophyll-a(Chl.a),total nitrogen,total phosphorus and secchi disc,Lake Taihu includeshyper and medium eutrophication zones.Meanwhile,Lake Tianmu and Lake Bositeng are light eutrophic and mesotrophic,respectively.Phytoplankton absorption coefficients at 440nm(aph(440)) are 1.02±0.51 and 0.69±0.40 forhyper and medium eutrophication in Lake Taihu,0.78±0.24 in Lake Tianmu,and 0.20±0.04 m-1 in Lake Bositeng,respectively.Correspondingly,aph(675) are 0.59±0.32,0.38±0.23,0.41±0.13 and 0.08±0.02 m-1,respectively.Statistics test shows that phytoplankton absorption ofhyper and medium eutrophic Lake Taihu,in addition to light eutrophication Lake Tianmu,is significantlyhigher than that in mesotrophic Lake Bositeng.Chlorophyll-specific absorption coefficients at 440nm(a*ph(440)) are 0.013±0.006,0.012±0.004,0.038±0.008 and 0.051±0.013m2/mgChl.a,respectively.Statistics test shows that a*ph(440) of Lake Taihu is much lower than that of Lake Tianmu,and a*ph(440) of Lake Tianmu is significantly less than that of Lake Bositeng.The order of the spectral absorption coefficient is as follows: Lake Taihu TⅠLake Tianmu Lake Taihu TⅡ Lake Bositeng,showing that phytoplankton absorption coefficients generally increase with trophic levels,but Lake Taihu TⅡ is lower than Lake Tianmu partly due to thehigh concentration of non-algae suspended matter.In contrast,chlorophyll-specific absorption coefficients decrease with enhanced trophic levels.Phytoplankton absorption coefficients generally increase with trophic levels due to the increase of biomass caused byhigh nutrient concentration.However,the decrease of chlorophyll-specific absorption coefficients with enhanced trophic level may be attributed to pigment package.

Response of planktonic bacterial abundance to eutrophication and salinization in Lake Bosten,Xinjiang

To investigate the response of planktonic bacterial abundance to lake eutrophication and salinization in drought zones,water samples of 23 stations in Lake Bosten were collected in June,2010.The DAPI-combined epifluorescence direct counting method(DAPI-FDC) was used to identify the spatial distribution pattern of planktonic bacterial abundance and the relationship with the environmental parameters.The results showed that the epilimnetic total nitrogen(TN) concentration in Lake Bosten was ranged 0.26-1.45 mg/L(mean = 0.91 mg/L),indicating a mesotrophic and eutrophic level.The concentration of total dissolved solids(TDS) varied from 219 mg/L to 1696 mg/L(mean = 1125 mg/L),which indicated that Lake Bosten is a brackish lake now.The abundance of planktonic bacteria was ranged(1.41-4.57) ×106 cells/ml(mean = 2.89×106 cells/ml),with the higher values appeared in station 5 and other heavily polluted northwest lake regions,and the lowest value appeared in the station 14 located in the estuary.Cluster analysis showed that the 23 sampling stations can be divided into two groups: freshwater region(FR) and brackish lake region(BLR).Compared with freshwater region,the concentrations of TDS,electrical conductivity,salinity,CODMn,chloride and sulfate in brackish lake region were significantly higher.The bacterial abundance was significantly positive correlated with CODMn and Cl-.In summary,the spatial distribution pattern of bacterial abundance was a response to different levels of nutrients and salinity in Lake Bosten.Hence the abundance of bacteria was a sensitive indicator reflecting the eutrophication and salinization.

Crustacean zooplankton community structure in Lake Bosten,Xinjiang

Crustacean zooplankton community in Lake Bosten was monitored and the impacts of environmental factors on curstacean zooplankton community structure were assessed during Jun.-Nov.2010 and Jan.2011.Results showed that crustacean zooplankton was mainly dominated by Cladocera,not only in species number,but also in density and biomass,with dominant species succeeding seasonally.In summer,crustaceans were dominated by large-sized Daphnia cucullata and Diaphanosoma brachyurum.With the decrease of large-sized zooplankton in fall and winter,the percentage of small-sized Bosmina coregoni increased,suggesting that competition works between zooplankton of different body size.Regression analyses indicated that crustacean biomass and mean body length were positively correlated with water temperature.Correlation analyses revealed that the biomass of B.longirostris and D.cucullata was positively correlated with transparency,but negatively with Chl.a,indicating these two dominant species being inhibited by the overgrowth of phytoplankton.Multivariate statistical analyses showed that 56.8% of the total variance in crustacean community structure was explained by environmental factors,with water temperature being the most important factor and water depth the second.High water temperature favoured the development of cyclopoids,D.cucullata and D.brachyurum.Meanwhile,B.coregoni preferred to flourish in shallow stations while D.cucullata and D.brachyurum in deep stations.The difference in distribution pattern of dominant species might be due to the fish predation.

Characteristics of amino acids during the process of algae-originated particles decomposition in Lake Taihu

The characteristics of decomposition rate and quantity of amino acids, as well as the change of nitrogen forms, were ex⁃ plored during the process of decomposition of high-density cyanobacterial particles in this study. The results showed that the initial concentrations of particulate amino acids (PAA) were 0.46 mmol / L in natural light group and 0.44 mmol / L in the aphotic group. At the end of the experiment, the PAA was much stable with a concentration of 0.30 mmol / L in natural light group, while de⁃ creased dramatically to 0.06 mmol / L in the aphotic group. The degradation rate constants were 0.03916 and 0.17424 d-1, respec⁃ tively. The concentration of dissolved amino acids (DAA) was much lower in comparison to PAA in the process of decomposition. In detail, the DAA increased gradually and peaked at 10.94 and 7.94 μmol / L for the two groups, respectively, and then declined to around the initial value in the end of the 21st day. At the beginning of the experiment, PAA accounted for 74% -80% of the total amino acids, then PAA was transformed to DAA and ammonia (NH4 ⁃N) quickly, and finally the NH4 ⁃N was transformed gradual⁃ ly to NO3 ⁃N by nitrification. Compared with the natural light group, the decomposition of particles in aphotic group was more com⁃ plete. Algal photosynthesis inhibited the decomposition of cyanobacterial particles in the natural group. Our results demonstrated that amino acids are potential nitrogen sources of phytoplankton and could be demineralized to NH4 ⁃N to support phytoplankton growth during cyanobacterial blooms. Therefore, the decomposition of high⁃density algal particles plays a key role in the mainte⁃ nance of cyanobacterial blooms.

Influence of submerged vegetation restoration on bacterial diversity and community composition in West Lake

Reconstruction of submerged vegetation is one of the key measures of eutrophication remediation.Using polymerase chain reaction-denaturing gradient gel electrophoresis(PCR-DGGE) and clone library analysis,we studied the impact of planting Potamogeton crispus and Vallisneria natans on bacterial diversity and community composition in West Lake,Hangzhou,China.Bacteroidetes(42.9%),Betaproteobacteria(30.8%) and Verrucomicrobia(14.3%) dominated in the water column from lake areas without submerged macrophytes.On the contrast,the proportion of Bacteroidetes reduced to 12.7% and 5.3%,respectively,after planting Potamogeton crispus and Vallisneria natans.Meanwhile,Betaproteobacteria increased to 52.4% and 59.5%,and Alphaproteobacteria increased from 4.4% to 19.0% and 12.8%,respectively.The proportion of Verrucomicrobia reduced substantially after planting Potamogeton crispus,but varied little after planting Vallisneria natans.This study indicates that submerged macrophytes can not only improve water quality,but also increase bacterial diversity,and shape bacterial community composition significantly.

Influence of the physicochemical characteristic of artificial substrates on water purifying capability of periphyton

Primary production,chlorophyll-a and alkaline phosphatase activity of periphyton can indicate its water purifying capacity.Five artificial substrates with different surface configurations and physicochemical characteristics were selected during this experiment.They were glass slide,PVC film,soft substrate,combined substrate and elastic substrate.The primary production,chlorophyll-a and alkaline phosphatase activity of periphyton attached on these five different substrates were investigated in situ.The results showed that physicochemical characteristics of artificial substrates were proved to be the key factors affecting the stability of periphyton community,primary production,chlorophyll-a and alkaline phosphatase activity.Generally during in situ attachment process,the maximum mass of periphyton appeared on the 8th to 10th day while periphyton primary production,chlorophyll-a and metabolic activity were also showed the highest.Primary production,chlorophyll-a and alkaline phosphatase activity of the periphyton attached on elastic and soft substrates were significantly higher than those on other three substrates.The net primary production of the periphyton attached on the elastic substrate was 164.21 mgO2/(g·h),the highest of those on the five artificial substrates.Compared with the soft substrate,the elastic substrate was more economic and better optimal artificial substrate for water quality restoration.