Study On Effect Of Compensation And Overcompensation In Tetraselmis Tetrethele Under Several Environmental Stresses

Objective and significance: In this study, Tetraselmis tetrethele was used as experimental material for studying the effect of compensation and overcompensation and its regularities on physiology and biochemistry. The significance of this study was that the results from this study could be used as some scientific data for studying the compensation and overcompensation in microalgae. Meanwhile, the regularity of overcompensation could be used as guidance for controlling the bloom of harmful algae and carrying out aquiculture of useful algae.Methods: Firstly, Tetraselmis tetrethele had been cultured for ten days under stresses of nutrients limitation, light limitation, lower salinity and higher salinity, while normal condition was control. Then, those stresses were removed, and the treated groups and the control had simultaneously been cultured for ten days under the condition of same inoculative density and other culture conditions. In the course of culture, cell density, content of chlorophyll-a, biomass, content of intracellular protein and intracellular carbohydrate were determined and analyzed, and some other correlative parameters were calculated and compared.Conclusions: Tetraselmis tetrethele showed a strong ability of overcompensation in the course of the following culture after stresses removal. The growth between those treated groups and the control that cultured under continued normal conditions existed significant difference (P<0.05). The main character of the overcompensation in Tetraselmis tetrethele was those treated groups had a higher average relative growth rate, a more number of cells, a more biomass and a higher chlorophyll-a content than those of the control. In the course of recovery growth, the maximal rate of net cells increase of nutrients limitation group, light limitation group and salinity stress group was 121.1%, 31.6%, 35%, and the maximal rate of net chlorophyll-a increase was 90.8%, 33.9%, 46.7%, while the maximal rate of net biomass increase was 95.3%, 34.8% , 36.9%. Then, with the process of the culture time, the difference between the treated groups and the control decreased gradually. Finally, every parameter of thetreated groups and the control trended to be equivalent for the reason of the limitation of environmental capacity. Meanwhile, the content of intracellular protein, the content of intracellular carbohydrate and the ratio of protein to carbohydrate (P/C) changed under the environmental stresses, but all of them would return to their initial levels in the following culture after stresses removal. However, the arisen time of overcompensation was different under different stresses, and it appeared at initial-middle stage under the stresses of nutrients limitation and light limitation, while at middle-later stage under the stress of salinity for the cause of the lag effect of osmosis regulation. In addition, the overcompensation in microalgae was probably one internal cause of algae bloom.