Study On Impacts Of Algal Accumulation On Ecology Of Water Hyacinth And Decomposition Of Plant Residues

Cyanobacterial cells accumulated seriously by the wind and lake flow in the bay area especially where aquatic plants grow. The effects of water hyacinth growth and physiological response changes in no more than 25℃ or above 25℃, different concentrations of cyanobacteria gathered were studied.This study also focused on changes of water and sediment organic matter in the decomposition of water hyacinth and which would provide a theoretical basis to mitigate adverse impacts and improve water purification effect and monitor organic matter content.(1)The effects of water hyacinth growth and physiological response changes in no more than 25℃ were studied. We used simulation test and designed five different concentrations of cyanobacteria. After adding cyanobacteria, water dissolved oxygen, pH, oxidation-reduction potential declined, concentration of nitrgon and phosphorus increased. Plant root length, total length, fresh weight in different treatment, increased compared with the beginning of the experiment, the increase of root length, total length and fresh weight were 0.29-2.44 times, 0.41-0.76 times and 0.9-1.43 times. The increase of root length, total length decreased with the increase of algae density. Leaf soluble sugar, MDA contents increased, which reduced the degree of injury to the plasma membrane of water hyacinth, it indicated that the water hyacinth can adapt to the adversity condition as algae density less than 60 g-L"1. While algae density above 60 g-L-1, soluble sugar contents had change trend of low-high-low, MDA contents increased, it indicated that the water hyacinth had irreversible stress.(2) The effects of water hyacinth growth and physiological response changes in above 25℃ were studied. We used simulation test and designed three different concentrations of cyanobacteria. The dissolved oxygen was quickly consumed after algae blooms gathered in above 25℃, EC conductivity increased, nutrient content increased. Water hyacinth stomatal conductance and transpiration rate decreased after algae blooms gathered. Water hyacinth roots were directly affected by the stress within the plant root key antioxidant enzyme activity changed in response to the sharp. SOD, POD, CAT in treatment two and three, increased compared with the blank, the increase of SOD, POD and CAT were 1.7,1.9 times,2.5,3.0 times and 1.0,2.0 times. Plant roots died. Total plant biomass, root biomass and root/leaf ratio declined, compared with the blank.(3) The changes of organic matter after plant residue decomposition were studied. We used simulation test and designed a blank and a treatment. As the decay of water hyacinth, concentration of Do、pH and OPR declined. Concentration of nitrgon and phosphorus increased. Δ1gK of fulvic acid extracted from water and sediment increased, E465/E665 decreased, it indicated that fulvic acid fat content were increased, aromaticity were decreased; Δ1gK of sediment humic acids were decreased, E465/E665 were increased, it indicated that humic acids aromatic was enhanced. The FT-IR spectrum showed that characters were similar between fulvic acid and humic acids, fulvic acid contained more fat and oxygen-containing functional groups, sediment humic acid contained more hydroxyl groups compared with fulvic acid. The fluorescence spectra showed that the aromatic of fulvic acid were decreased; the aromatic of humic acid were slightly increased with the decomposition of water hyacinth.