The Analysis Of Algal Community Structure And Effect Of Dominant Group On Calcium Carbonate Deposition In Huanglong Scenic Area

The periphytic algae are breeding rapidly in the travertine deposition landscapes of Huanglong,Sichuan province,China.In order to ascertain the reasons,trends and effects of this situation.An investigation was carried out in 2015,water samples and algae samples were collected in spring,summer and autumn from twelve typical sampling spots.According to the analysis results of environmental factors and community structure,CCA(canonical correspondence analysis)was applied to find out the key environmental factors affecting the community structure.Meanwhile,sufficient diatoms and xanthophyceae were separated and purified from travertine walls,and a simulated situation of local water environment was set up in lab.The changes of deposition system pH value,calcium and magnesium ion concentration were measured to analyze the effect of diatoms and xanthophyceae on deposition process.The phase structures,vibrational frequencies,micromorphology features and element contents of deposition were detected respectively by the means of X ray diffraction(XRD),fourier transform infrared spectrometer(FT-IR spectrometer),scanning electron microscopy(SEM)and energy dispersive X-ray spectrometer(EDX spectrometer).The monosaccharide components in polysaccharides,low molecular weight organic acids and amino acids of algal extracellular products were qualitatively and quantitatively determined by use of HPLC(high performance liquid chromatograph).The results showed that: 1.Effect of environmental factors on algal community structure in Huanglong Scenic Area(1)a total of 88 species of algae which affiliated with 5 phyla,9 classes,18 orders,20 families and 37 genera were identified.Meanwhile,the oligotrophic and native species had always occupied an absolute advantage.As the seasons changed,the species abundance,biomass and Margalef index increased,the Pielou index and Wilson-Shmida index decreased,the index of Shannon-Wiener and Simpson smoothed.(2)To some extent,the Huanglong water environment has been affected by human,especially the great seasonal differences existed in human factors.Based on the results of CCA,the human factors(TOC,TN and CODMn)were thought to be crucial factors for the community structure.2.Effect of Huanglong psychrophilic periphytic diatoms on calcium carbonate deposition in low temperature environment(1)During the trial period,the pH values of diatom,xanthophyceae and blank group showed a changing trend of rapid rise,slow rise and gradual stabilization.(2)Many highly reactive sites in the diatomaceous cytoderm surface could be an ideal template for crystal nucleation and promote calcium carbonate deposition,the extracellular acidic metabolites of xanthophyceae eroded calcium carbonate deposition.What‘s more,A little of magnesium ion replaced the position of calcium ions in the lattice,commonly known as isomorphism.(3)The diatomaceous and xanthophyceae extracellular polymeric substances(EPS)had little effect on crystal form of deposition.Calcite formed in the depositional environment of pH 8 to 9 and 10?,and it is in accord with the results of blank group.However,the EPS caused unit cell parameters changed,spectral line shifted and crystallinity decreased.The crystallization results of diatom group and xanthophyceae group were different with the blank group,The EPS of diatoms and xanthophyceae had a certain regulating effect on the morphology of calcium carbonate,and the chimeras of ring crystal and cubic crystal were formed in the diatom system,the etch figures of crystal faces were formed in the xanthophyceae system.(4)Individual diatoms have bred faster than filamentous xanthophyceae.The main components of two algal extracellular products were consisted of monosaccharide components in polysaccharides,low molecular weight organic acids,amino acids and pigments.Among this,the polysaccharides and proteins deposited minerals,the low molecular weight organic acids eroded minerals and pigments colored minerals.Above all,the research provides an illustration for the biological action of Huanglong travertine deposition and a guidance for the environmental governance.