| “Qingtai”is a general term for a variety of filamentous algae,including Spirogyra,Cladophora,Zygnema,Mougeotia,etc.,and Cladophora which is difficult to control has been studied the most.Due to its strong adaptability to the environment and rapid reproduction rate,filamentous algae can form a huge amount of biomass in a short period of time,thus causing harm to fishery,shipping,landscape,ecology,etc.Therefore,filamentous algae control is a problem the whole world facing.At present,researches on filamentous algae mainly focus on basic ecology and control methods.Basic ecology mainly involves life history,growth and development laws,etc.,whereas the control includes chemical,physical and biological methods,among which chemical algae removers and heavy metals are the main ones.At present,many methods have varying degrees of side effects,so to explore safe and effective methods in controlling filamentous algae is still the main direction of filamentous algae research.1.Investigation of on the species and habitats of filamentous algae occurred in aquaculture pondsThe species and habitat of filamentous algae were investigated in this study.The species survey showed that there were various filamentous algae species,mainly including Zygnema,Spirogyra,Cladophora and Mougeotia,and there were various species or subspecies within the genus,showing different genetic relationships.The habitat survey results showed that there were no significant differences in total nitrogen and phosphorus levels between filamentous algae occurred ponds and no filamentous algae occurred ponds in five groups（P>0.05）,whereas the content of Chlorophyll a in filamentous algae occurred ponds in four groups was significantly higher than that in no filamentous algae occurred ponds（P<0.05）.The ratio of available N/P in sediment was below 0.5 in the five groups,and the ratio of available N/P in no filamentous algae occurred ponds was 26.32%higher than filamentous algae occurred ponds.Phytoplankton growth could be inhibited in low N/P ratio condition,whereas filamentous algae has strong adaptability to low nitrogen content and N/P ratio environment.In addition,the detection of filamentous algae propagules showed that they were widely presented in water bodies and sediment of filamentous algae occurred ponds,no filamentous algae occurred ponds and water sources,and filamentous algae propagules were detected even in sterilized and sun-exposed ponds.Therefore,it is not a one-shot solution to control filamentous algae by killing moss propagants in aquaculture ponds,but can be used as an auxiliary measure,and it is a promising direction to control filamentous algae by regulating the nitrogen content and the ratio of nitrogen to phosphorus in aquaculture pond system.2.Effects of sediment nitrogen and phosphorus regulation on filamentous algae occurrence in aquaculture pondNitrogen and phosphorus and its ratio play an important role in the growth of algae and have an important effect on the niche competition between filamentous algae and planktonic algae.In order to investigate the effects of nitrogen and phosphorus content and nitrogen and phosphorus ratio on the occurrence of filamentous algae,the microecosystem was simulated.The results showed that when N/P was 40:1,it was relatively unfavorable for moss growth.It was also found that benthic cyanobacteria could inhibit the growth of filamentous algae,and there was a significant negative correlation between them（P<0.01）.In addition,there was a significant positive correlation between total nitrogen and phytoplankton biomass（P<0.05）,and there was a significant positive correlation between benthic cyanobacteria cover area and phytoplankton biomass（P<0.01）.A total of 313species of secondary metabolites of benthic cyanobacteria were annotated,and Cis,Cis-muconic acid（32.48‰）,Erucamide（9.52‰）,Phosphoric acid（6.97‰）,Fenpropidin（6.53‰）and Propionic acid（5.16‰）accounted for more than 5‰,respectively.This study provided a new idea for filamentous algae control from two perspectives of nitrogen and phosphorus nutrients in sediment and allelochemicals from others species.3.The life history of Cladophora and effects of selected ecological factors on the release of propagulesCladophora has strong reproductive ability and special reproductive modes;therefore,the study of its life history is important if its biomass is to be adjusted artificially.In this study,we observed the life history of Cladophora sp.in freshwater in China and studied the effects and relative strength of culture medium,p H,light intensity and temperature on the release of propagules.This study discovered a new life history of Cladophora sp.The four factors had significant effects（P<0.05）on the release of propagules.The culture medium,p H,light intensity and temperature that had the highest zoospore release were Aquatic No.6,p H 5,4000 Lx and 35°C,respectively,whereas those that had the highest gamete release were Knop culture medium,p H 4,4000 Lx and 30°C,respectively.In this study,the order of the factors in terms of the effect on zoospore release from strong to weak was:temperature,culture medium,p H and light intensity,and the order of the factors in terms of the effect on gamete release from strong to weak was:culture medium,p H,temperature and light intensity.This study has enriched the cognition of life history of Cladophora,and has reference valu e for artificial adjustment of environmental factors to regulate the biomass of Cladophora.4.Effects of different ecological factors and control methods on Cladophora growthAt present,there are few studies on the effects of ecological factors on the growth of Cladophora,which is difficult to support the research and control of filamentous algae.There are still few studies on the effects of ecological factors on its growth,which is difficult to support the research and control of filamentous algae.Therefore,this paper studied the effects of environmental factors,nutrients and physical control measures on the growth of Cladophora,and measured SOD activity and total antioxidant capacity to help understand the stress situation.In this study,it was found that under high nutrient conditions,the wet weight of Cladophora increased briefly and then decreased rapidly due to reproduction,whereas under oligotrophic conditions,Cladophora underwent slow vegetative growth without reproduction.In the common green algae culture medium,BG11 is relatively beneficial to the culture experiment of Cladophora.It was found that light,p H and temperature had significant effects on the growth of Cladophora.The concentration of nitrogen and phosphorus nutrients had an important effect on Cladophora.In this experiment,it was found that phosphorus compensation point of Cladophora was 3μmol L-1,and 10μmol L-1 was the mutation point that starvation stress relief.In addition,Cladophora had strong tolerance to low nitrogen or high nitrogen environment.The effective inhibitory concentrations of bright blue and sodium humate were 16 mg L-1 and 12 mg L-1,respectively,and they had synergistic inhibitory effects with bacillus and EM bacteria,respectively.This experiment is of great significance to understand the impact of environmental factors on Cladophora,and the study of nutrients and culture medium is of reference value for the cultivation experiment and control of Cladophora in the future.5.Study on the inhibitory effects and oxidative damage of different chemical substances on CladophoraIn order to explore the effective and ecological ways to deal with overgrowth of filamentous algae,berberine,copper acetate,Na Cl O and DBNPA as well as organosilicon additives and iron ions were screened for a series of experiments.In this experiment,berberine,copper acetate,Na Cl O and DBNPA all showed strong inhibitory effect on Cladophora.The inhibitory rate of 0.10 mg L-1 berberine reached82.86%on the 5th day,and that of 4.0 mg L-1 copper acetate reached 73.05%on the5th day.The inhibitory rate of 0.8 mmol L-1 Na Cl O was 96.32%at day 5,and that of9 mg L-1 DBNPA reached 71.28%at day 5.When the above four substances were combined with organosilicon additives or iron ions,the synergistic effect only appeared in the Na Cl O organosilicon complex group.In each experimental group,the change rule of MDA was similar to that of total protein,which proved that membrane lipid and protein were susceptible to oxidative damage,and the oxidative damage was similar.When membrane lipid underwent oxidative damage,the cell accelerated protein synthesis.The cell ruptured and MDA dissolved into the solution under high concentration of inhibitor,showing the decrease of MDA content in the cell.The change of SOD activity was similar to that of total protein.SOD activity is prone to decrease by the effect of inhibitors,and when it decreases to a certain extent,cells will accelerate the synthesis of non-enzyme antioxidants and show the increase of T-AOC.The proportion of enzymatic antioxidants in T-AOC is lower than that of non-enzymatic antioxidants.Enzymatic antioxidants are vulnerable to oxidative damage and their activity is reduced.However,non-enzymatic antioxidants can also be reduced due to the action of inhibitors,such as Na Cl O and DBNPA.This study provided some reference for the prevention and control of filamentous algae,and preliminarily revealed the inhibitory mechanism of the above four chemicals on filamentous algae.6.Grazing effects of Xenocypris davidi Bleeker（Cyprinidae,Cypriniformes）on filamentous algae and the changes of intestinal microbial composition and metabolic function after grazingIn order to explore safe and ecological biological control methods,we comparatively studied the grazing effects of Xenocypris davidi Bleeker on Cladophora（one species）and Spirogyra（two species）and intestinal microbiota which related to digestion and absorption closely.The results showed that this fish was more receptive to Spirogyra than Cladophora and the intakes to different species of Spirogyra were also different.The fish weight increased slightly after feeding Spirogyra.Compared with the initial values,the levels of total nitrogen and total phosphorus increased significantly（P<0.05）.Intestinal microbiota diversity and richness were different feeding on three filamentous algae species,and the similarity was higher feeding on two Spirogyra species.The microbial species detected in this study belonged to 40 phyla and 838 genera.The most dominant community members at the phylum level were Proteobacteria,Actinobacteria,Firmicutes,Verrucomicrobia and Fusobacteria.The clustering characteristics of different groups and subgroups were obvious based on microbial composition.Some significant differences in relative abundance of eight nutrition-related metabolism functions were found among groups and subgroups（P<0.05）.The results of this study proved the strong plasticity of intestinal microbiota of Xenocypris davidi Bleeker and showed the feasibility of biological control of filamentous algae by domestication at seedling stage.7.A comparative study on metabolome of Cladophora and waterweed（Elodea nuttallii）In order to explore the method of killing filamentous algae discriminately without harming waterweed,we conducted a comparative study on the metabolome of the two species.The results showed that there were obvious differences in metabolite composition between Cladophora and waterweed.A total of 377 annotated differential metabolites were identified between the two species,among which 208were up-regulated and 169 were down-regulated.There were 43 unique metabolites in Cladophora compared with waterweed.In this experiment,there were 65 KEGG compounds detected that were significantly different between Cladophora and waterweed,mainly including polypeptides,steroids,nucleosides,lipids and carbohydrates.In this experiment,the top 20 important pathway metabolites in relative quantity upregulated in Cladophora were screened out,among which 4important pathways were 0 and 2 close to 0 in waterweed,but the content of the 6important pathway metabolites was high in Cladophora.Compared with waterweed,11 metabolites of Cladophora contributed significantly to the difference,whereas 19metabolites of waterweed contributed significantly to the difference.This study is of great significance for targeting enzymes in important metabolic pathways of Cladophora and selectively killing it. |
