Analysis Of The Key Components Of Phaeocystis And Its Influence On Pseudo-homomorpha Sinensis

The frequent outbreak of cyanobacteria bloom has attracted people’s attention to harmful algae,and harmful algae could have bad effects on aquatic organisms.Most harmful algae belong to Cyanophyta,Physalis and Pyrrhophyta,which can casue harmful algal blooms both in eutrophic inland waters and oceans.To study the effect of toxic algae on Cladocera,This paper selected Ochromonas gloeopara as Daphnia similoides sinensis’s food.We fed D.similoides sinensis with O.gloeopara to understand the impacts of O.gloeopara on the D.similoides sinensis.The main content of the experiment include the analysis of the key components of O.gloeopara,the influence of O.gloeopara and the filtrate of O.gloeopara on the life history of and D.similoides sinensis,the changes of several anti-stress proteins of D.similoides sinensis under the stress of O.gloeopara.The main results of the experiment are summarized as follows:1、Analysis of the key components of O.gloeopara.The method of chemical extraction and vacuum drying was used to extract and purify the toxin of O.gloeopara.The toxin was white and crystal granula.The results showed that the crude toxin of O.gloeopa.has a strong lethal effect on the D.similoids sinensis.The toxin of O.gloeopara was the same as the toxin of Prymnesium parvum,and it had hemolytic toxicity and fish toxicity.The results showed that the amino acid composition of O.gloeopara was not significantly different from that of Scenedesmus obliquus.but the contents of all kinds of amino acids were significantly lower than that of S.obliquus.The content of unsaturated fatty acids in O.gloeopara was much lower than that of S.obliquus.So,O.gloeopara was not a high-quality food.2.Effects of food combinations on the life history of D.similoides sinensis.In the experiment of life history,we set up a different combination of O.gloeopara and S.obliquus with the equal total density of algae,we fed D.similoides sinensis with mixed food,observed and recorded the life history parameters.The results showed that the presence of O.gloeopara significantly reduced the survival rate of Daphnia,and affected their ability to reproduce.Only when the cladocerans were cultured in the conditions of all S.obliquus and a low proportion of O.gloeopa 25%,Daphnia can reproduce.Even we removed O.gloeopara out of the food,it still cannot eliminate the adverse effects of O.gloeopara on D.similoides sinensis.It illustrated the influence of O.gloeopara to Daphnia was not only caused by the limitation in nutrition,toxins of O.gloeopara also had adverse effects in D.similoides sinensis.In the part of the filtration rate experiment,we added two different kinds of food including O.gloeopara and 0.gloeopara mixed with S.obliquus to the cladocerans.The results revealed that the addition of S.obliquus into the food setting with only O.gloeopara can help to improve the water filtration rate of D.similoidessinensis,it can help D.similoides sinensis resist toxic effects of O.gloeopara in a short period of time,to a certain extent.3.Effects of the filtrate of O.gloeopara on the life history of D.similoides sinensis.The experimental results showed that the filtrate of O.gloeopara had strong toxicity to Daphnia,the toxicity of O.gloeopara could prolong D.similoides sinensis’s maturation time,reduce the reproductive capacity of D.similoides sinensis and lifetime of D.similoides sinensis.What’s more,the toxicity effect cannot be relieved by S.obliquus even if we changed D.similoides sinensis’s living condition from full of the filtrate of O.gloeopara to normal condition aeration water.The results of the treatment group also proved that if the damage of toxic substances in the filtrate of 0.gloeopara was accumulated in D.similoides sinensis,Daphnia itself had no ability to repair this kind of damage.4.Effects of O.gloeopara on several anti-stress proteins of D.similoides sinensis.Three groups of O.gloeopara with different densities were set upw:4 x 105,1 x 105,5 x104 cells mL-1.We cocultured O.gloeopara and D.similoides sinensis for 48 hours.Then we determined the contents of several anti-stress proteins in D.similoides sinensis.The experimental results showed that the response of anti-stress proteins in D.similoides sinensis to different densities of 0.gloeopara stress was different.Medium and low density of 0.gloeopara could increase the activity of SOD,CAT and GST in D.similoides sinensis.D.similoides sinensis resisted O.gloeopara through the up regulation of related enzymes and heat shock proteins in the body.When the density of O.gloeopara was high,the expression of the anti-stress protein related to the D.similoides sinensis may be inhibited.The D.similoides sinensis cannot cope with the free radical oxidative damage by the repair function of enzyme and heat shock proteins.To sum up,the lack of the nutrients and the toxins produced by O.gloeopara could have bad effects on the D.similoides sinensis,and when effects were accumulated,and cannot be alleviated by the improvement of the food quality in the later period.0.gloeopara could also affect the activity of various anti-stress proteins in the D.similoides sinensis,and destroy the normal physiological function of D.similoides sinensis.