Studies On The Effects Of Cyanobacteria And Antibiotics On The Population Ecology Of Rotifer Brachionus Calyciflorus

In recent years, more human activities and social progress worsen the waterenvironment problems, especially in close water which have a weak water massexchange. Water environment problems have become as one of the environmentproblems which the world concluded we need to solve. Algae bloom and antibioticmisuse were the major cause of water pollution in most countries. The goal of presentstudy is to discuss the effects of cyanobacteria and antibiotics on the growth andreproduction of Brachionus calyciflorus with the laboratory experiments. Main resultsfor this study are as follows:1.We investigated the effects of M. aeruginosa on the survival and reproductionof Brachionus calyciflorus using the life table method at different temperatures. Thefindings showed that concentration of M. aeruginosa significantly affected theintrinsic rate of increase (rm), net reproductive rate (R0), average lifespan (L) andoffspring number (P <0.05). Temperature also significantly affected the generationtime (T), average lifespan (L) and offspring number (P <0.05). Moreover, theinteraction between temperature and concentration had statistically significant effectson offspring number (P <0.05). M. aeruginosa suppressed the survival andreproduction of B. calyciflorus, particularly at a concentration of106cells/mL. The rmvalues of the rotifers exposed at106cells/mL decreased more than200%comparedwith those of the control group. However, At a lower concentration,104cells/mL, M.aeruginosa may supply appropriate nourishment to rotifers. In addition, atconcentrations of105and106cells/mL, the inhibition of rotifers by M. aeruginosaheightened with increasing temperature.2.The effect of temperature and Microcystis aeruginosa concentration on thepopulation growth of Brachionus calyciflorus was studied at15,25,30and35°Cunder concentration of0,104,105,106cells/mL by population accumulative culture.The rotifer was fed with Chlorella pyrenoidosa at a concentration of5.0×105cells/mL.The results showed that temperature and M. aeruginosa concentration affected thepopulation density very significantly (P <0.01). Temperature, M. aeruginosaconcentration and the interaction between temperature and concentration affectedpopulation growth rate very significantly (P <0.01). In the range of temperaturestudied, the rotifer population growth rate increased and the maximum populationdensity tended to increase initially and then declined. The population growth rate was minimum under15°C, and the population density could be maximum under30°C. Inthe range of Microcystis aeruginosa concentration studied, under the sametemperature, the rotifer population density and population growth rate were declinedobviously with increase in concentration.3.We investigated the effects of Synechocystis sp. PCC6803on the survival andreproduction of Brachionus calyciflorus using means of individual culture andpopulation accumulative culture at different temperatures. The findings of populationaccumulative culture showed that the population growth rates of rotifers fed onSynechocystis or Chlorella pyrenoidosa was higher than these at starvation status androtifers fed on Synechocystis grew faster than that fed on C. pyrenoidosa at15°C.However, at25°C and35°C, the population growth rates of rotifers fed onSynechocystis was far below than that fed on C. pyrenoidosa. The results ofexperiments of individual culture showed that the survivorship of Brachionuscalyciflorus increased with increasing concentration of Synechocystis at15°C. At25°C and35°C, there were opposite exactly. The fecundity of rotifers increased withincreasing concentration of Synechocystis at any temperature. Temperaturesignificantly affected the offspring number of rotifers, but no significant effects on thenet reproductive rate (R0), generation time, intrinsic rate of increase (rm) and averagelifespan (L). The interaction between temperature and Synechocystis concentrationhad statistical significant difference on offspring number and average lifespan ofrotifers. In conclude, B. calyciflorus was able to utilize this strain of Synechocystis asa food source, especially at low temperature. The inhibition of growth andreproduction of rotifers by Synechocystis might be relative to Synechocystis morphaand then it formed colonial structure to disturb mechanically rotifers.4.By population accumulative culture, we investigated the effect ofchloramphenicol and erythromycin on the population growth and reproduction ofBrachionus calyciflorus at different concentration of chloramphenicol anderythromycin, and the rotifer was fed with Chlorella pyrenoidosa at concentration of5.0×10~5cells/mL. The results showed that erythromycin affected population growthrate significantly (P <0.05) but it has no significant influence on population density(P>0.05). At the low density (6.25μg/mL) of chloramphenicol and erythromycin, allof the population density and population growth rate were increased. When theconcentration of chloramphenicol and erythromycin increased to12.5~50μg/mL, therotifer population was inhibited and this inhibition increased with the antibioticsconcentration. When the antibiotics concentration is100μg/mL, the inhibition ofantibiotics on rotifers is more obvious. 5.Using means of individual culture, we investigated that different concentrationsof chloramphenicol and erythromycin (0μg/mL,6.25μg/mL,12.5μg/mL,25μg/mL,50μg/mL and100μg/mL) on the growth and reproduction of Brachionus calyciflorus.The results showed that6.25μg/mL of erythromycin have no inhibition effects on thegrowth and reproduction of B. calyciflorus, instead, it can promote their growth andreproduction. When the concentration of erythromycin increased to12.5μg/mL,erythromycin began to have negative effects on rotifers, and the inhibition becamemore and more obvious with the increasing concentration. Similarly, chloramphenicolcan promote rotifers’s growth and reproduction when its concentration fell below12.5μg/mL. Moreover, at6.25μg/mL, chloramphenicol have greater positive effects onrotifers than erythromycin. At higher concentration (12.5μg/mL~100μg/mL),chloramphenicol also have greater inhibition effects than erythromycin.