Effects Of Water Suspended Particulate Mater On The Growth Of Freshwater Algae And Its Feedback Effect

The eutrophication of water body is one of the major issues of waterenvironment at present. In the state of eutrophica water, the aerobic algae increasedrapidly in a short time will cause “bloom” or “algae blooms”. However, suspendedparticulate matter, as a special kind of pollutants in the waterbody, rarely wasreported that its effects on the algae growth mechanism in the waterbody. And theimpact of algae and its extracellular secretion on the flocculation and sedimentationof suspended particular matter was very rarely studied. In this paper, From views ofthe cells growth, physiological and biochemical characteristics and the changes ofphotosynthetic activity, we explored the mechanism of the effects of differentconcentrations and particle sizes of the suspended particulate matter on Scenedesmusobliquus, Chlorella phyrenoidosa and Microcystis flosaquae. The main conclusionsare as follows:(1) All of the three kinds of algaes under the stress of different concentrationstreated and untreated suspended particular matter had the “low concentrationspromote and high concentrations inhibition” phenomenon, that will promote thegrowth of algae in a certain concentration range, but exceeds a critical concentration,it will had the inhibition effect on the algae growth, with concentration going by. The40mg/L of treated suspended particulate matter and50mg/L untreated suspendedparticulate matter had the biggest inhibition effect on Scenedesmus obliquus. The60mg/L of treated suspended particulate matter and40mg/L untreated suspendedparticulate matter had the biggest inhibition effect on Chlorella phyrenoidosa. Butboth of the30mg/L of treated and untreated suspended particulate matter had thebiggest promotion effect on Microcystis flosaquae, the50mg/L of treated anduntreated suspended particulate matter had the biggest inhibition effect onMicrocystis flosaquae.(2) Under the stress of the different concentrations or particle size of suspendedparticulate matter, there were bigger effects on the superoxide dismutase (SOD) and catalase (CAT), the content of malondialdehyde (MDA), soluble protein content,reactive oxygen species (ROS) levels, cell cycle and apoptosis rate of three kinds ofalgae body, and the integrity of DNA molecule of Scenedesmus obliquus andMicrocystis flosaquae were affected, but it no effect on the integrity of DNAmolecule of Chlorella phyrenoidosa.(3) For the suspended particulate matter with same size and differentconcentrations, the small particle size of the suspended particulate matter had biggereffects on the algae growth than the large one. The untreated suspended particulatematter lengthened the retardation period of Scenedesmus obliquus, and it had theinhibition effect on the chlorophyll a content of Scenedesmus obliquus. Apart fromthe chlorophyll a content of96-150μm group was inhibited, the treated suspendedparticulate matter had the promotion effect on the other size groups. The untreatedsuspended particulate matter75-96μm group had the strongest inhibition effect, allthe treated suspended particulate matter showed the promotion effect on theChlorella phyrenoidosa. However, the untreated suspended particulate matter75-96μm group had the promotion effect on the Microcystis flosaquae, and0-75μm groupshowed the inhibition effect.(4)Different concentrations and/or sizes suspended particulate matter havedifferent effects on the photosynthetic activity of three kinds of algae. It showed thatthe effects on the photosynthetic activity have different target sites, so themechanisms of the influence were different. With the induction of different concentrationsof suspended particulate matter, the relative electron transport rate of Scenedesmus obliquuswas reduced in a certain extent, with time going by. But this inhibition effect was in the range oftolerance of the algal cells, the algal cells could recover the electron transport rate to normallevels or even higher to resist adverse environment by self-regulation. When more thanself-regulating capacity of the algae, it can not through its own ability to repair the damage,photosynthetic activity was strongly inhibited.(5)The suspended particulate matter played the role of the “source” and “sink” for thenitrogen and phosphorus, when the culture medium were rich in nitrogen and phosphorus, thesuspended particulate matter uptook nitrogen and phosphorus, it played the role of the “sink”;when the culture medium occurred the consumption of nitrogen and phosphorus, coming into being an interfacial potential energy, the susupended particulate matter started to releasing thenitrogen and phosphorus to culture medium, it played the role of the “source”. Three kinds ofalgae on the absorption of NH4-N and PO4-P fit the enzymatic reaction kinetics of theMichaelis-Menten equation. Belong to the same green algae, Scenedesmus obliquusand Chlorella phyrenoidosa closed to the maximum absorption rate of NH4-N.However, belong to the blue algae, Microcystis flosaquae demonstrsted thecharacteristics of rapid absorption of NH4-N, and the maximum absorption rate washigher than the green algae. For the absorption of NH4-N and PO4-P, we can see thecompetitive ability of three kinds of algae from strong to weak: Chlorellaphyrenoidosa> Microcystis flosaquae> Scenedesmus obliquus...