Gao Guang

Spatio-temporal heterogeneity of water quality(2010-2011) and succession patterns in Lake Bosten during the past 50 years

To investigate the spatio-temporal heterogeneity of water quality in Lake Bosten,water qualities of six stations were monitored from June 2010 to June 2011.The results showed that water qualities were distinctly different among stations,and monthly variations of water quality among stations were not uniform.In the open lake area of Lake Bosten: the water quality was the worst in northwest;whereas water quality in the river mouth of Kaidu River was the best,though changed greatly from month to month.In the less-open lake area of Lake Bosten: water quality was the best in Lake Lama(GradeⅠto Ⅲ);water quality in lake wetlands was the worst(Grade Ⅴ or even worse).The main pollutants in Lake Bosten were salinity,total nitrogen,sulfate and chloride.In general,the trophic level of Lake Bosten is mesotrophic,and sometimes it reaches light eutrophic.Agricultural non-point source pollutions,hydrology,lake currents and aquatic plants were the main factors attributed to the spatio-temporal heterogeneity of water quality in Lake Bosten.Analysis of the variation of water quality in the past 50 years shows that Lake Bosten has converted from the largest inland freshwater lake to a brackish lake since 1970s.The process of salinization could be divided three stages: rapid rise,slow decline and increase again.Accompanied with the lake salinization,concentrations of other pollutants increased rapidly as well.Overall,the variation of water quality in Lake Bosten is controlled by natural factors and human factors.In recent decades human activities have exacerbated the salinization and eutrophication of Lake Bosten.To investigate the spatio-temporal heterogeneity of water quality in Lake Bosten,water qualities of six stations were monitored from June 2010 to June 2011.The results showed that water qualities were distinctly different among stations,and monthly variations of water quality among stations were not uniform.In the open lake area of Lake Bosten: the water quality was the worst in northwest;whereas water quality in the river mouth of Kaidu River was the best,though changed greatly from month to month.In the less-open lake area of Lake Bosten: water quality was the best in Lake Lama(GradeⅠto Ⅲ);water quality in lake wetlands was the worst(Grade Ⅴ or even worse).The main pollutants in Lake Bosten were salinity,total nitrogen,sulfate and chloride.In general,the trophic level of Lake Bosten is mesotrophic,and sometimes it reaches light eutrophic.Agricultural non-point source pollutions,hydrology,lake currents and aquatic plants were the main factors attributed to the spatio-temporal heterogeneity of water quality in Lake Bosten.Analysis of the variation of water quality in the past 50 years shows that Lake Bosten has converted from the largest inland freshwater lake to a brackish lake since 1970s.The process of salinization could be divided three stages: rapid rise,slow decline and increase again.Accompanied with the lake salinization,concentrations of other pollutants increased rapidly as well.Overall,the variation of water quality in Lake Bosten is controlled by natural factors and human factors.In recent decades human activities have exacerbated the salinization and eutrophication of Lake Bosten.

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.

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.

Variation of bacteria in water and attached on Microcystis colonies and their activity during the algal blooms

The bacterial abundance and active bacterial abundance of water and algae attached, as well as the Chl.a and nutrient concentrations, were investigated, and the metabolism coupling between algae and bacteria were also discussed. The results showed: 1) The bacterial abundances of water increased with the Chl.a concentrations increasing(r2=0.466, P0.05), although the peak value was delayed with the Chl.a concentration. Variation of the algae attached bacterial abundances were the similar patterns. 2) There was a significantly positive relationship between the active bacterial abundances and total bacterial abundance(r2=0.678, P0.05). Although the algae attached active bacterial abundance was less than the active bacterial abundance of water, the significantly increased patterns were also founded with the active bacterial abundance of water increasing (r2=0.836, P0.05). 3)The algae attached bacteria abundances and activities were determined by the algae growth status. The ratio of active algae attached bacteria/total algae attached bacteria was higher than that of total bacteria, and this ratio was increased in the period of May to September during the algal blooms.

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.

Bacterial alkaline phosphatases and affiliated encoding genes in natural waters: A review

Soluble reactive phosphorus is the main form of phosphorus directly available for phytoplankton in natural waters, and the organophosphate mineralization catalyzed by bacterial alkaline phosphatases maintains the supply of soluble reactive phosphorus. We summarized the species and subcellular location of bacterial alkaline phosphatases and found that PhoA, PhoX and PhoD were the main phosphatase species. Over 50% of PhoX were distributed outside of bacterial cells, which is particularly important for the regeneration of soluble reactive phosphorus in natural waters. The research progress in communities of alkaline phosphatase enco⁃ ding bacteria and the environmental factors influencing the expression of alkaline phosphatase encoding genes were also reviewed. We compared and analyzed the characteristics and developing trend of identification methods towards bacterial communities genera⁃ ting alkaline phosphatases. Most of studies about bacterial alkaline phosphatase⁃encoding genes were focused on oligotrophic marine ecosystems, and little was on the lake ecosystems which are also facing the phosphorus⁃limiting problem. Further researches should construct the bacterial metagenomic databases for certain eutrophic lakes to provide basis for build the methodology for bacterial al⁃ kaline phosphatases and affiliated encoding genes in freshwater ecosystems, which are beneficial to understand the microbial mech⁃

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.

Variation of bacterial dominated population abundance in Meiliang Bay,Lake Taihu,detected by FISH during summer and winter

FISH was used to analyze the abundance of dominated bacteria population in Meiliang Bay of Lake Taihu in winter and summer in 2008.The four dominated bacteria population(α-proteobacteria,β-proteobacteria,γ-proteobacteria,Bacteroidetes) were analyzed by in situ hybridization with specific fluorescently(FITC) labeled rRNA-targeted oligonucleotide probes in the test.The results indicated:①The proportion of each of the four dominated species in the total number of bacteria was all significantly higher in winter than that in summer(P0.01);②the abundance ofα-proteobacteria rose notably with the increase of TP concentration (R~2=0.860,P0.01);③there was ascending trend in the abundance of bacteria along with the increase of Chl.a concentration, especially that ofγ-proteobacteria was more remarkable than the others(R~2=0.857,P0.01);④the abundance of bacteria population,especially for Bacteroidetes,was also influenced by PO_4~(3-) concentration(R~2=0.733,P0.05).