Effects Of The Environmental Factors On Nutritional Value And Photosynthetic Characteristics Of Typical Bait Microalgae

Microalgae are widely used in animal feeding and aquaculture due to their high nutritional value.Temperature,light intensity,nutrient concentration and other environmental factors are the main factors that affect the biomass accumulation and nutritional value of microalgae.To clarify the effects of multiple environmental factors on photosynthetic characteristics and nutritional value of bait microalgae is helpful to guide the cultivation and management of fish,shrimp,crab,shellfish,etc.,which has important production significance.In this study,Thalassiosira weissflogii and Pyramimonas sp.were selected to explore the effects of temperature,light intensity,and nitrate concentration on the nutritional value and photosynthetic characteristics of the two bait microalgae.In this study,the effects of different temperature,light intensity,and nitrate gradient on photosynthetic characteristics such as specific growth rate and pigment content of microalgae of two bait microalgae were investigated,and analyzed the effects of environmental factors on nutritional value parameters of microalgae of two baits.In addition,a multifactorial coupling experiment was conducted to study the photosynthetic parameters and fatty acid and amino acid components of the two bait microalgae,with two temperatures（10 and 25℃）,two light intensities(50 and 150μmol photons m^-2 s^-1)and two nitrate concentrations(2 and 100μmol L^-1).The results show that:（1）With the increase of temperature,the specific growth rates of T.weissflogii and Pyramimonas sp.showed an increasing trend first and then decreased,and both reached the maximum value at 25℃,and the growth rates of Pyramimonas sp.were more significantly inhibited at 30℃than those of T.weissflogii.The pigment,soluble protein and soluble carbohydrate contents of Pyramimonas sp.increased first and then decreased with the increase of temperature,and reached the highest value at 15℃.（2）The specific growth rates of T.weissflogii and Pyramimonas sp.were highest at 300μmol photons m^-2 s^-1,and the growth rates of Pyramimonas sp.were more significantly inhibited by low light.As the light intensity increases,the pigment content of T.weissflogii an increasing trend first and then decreased,reaching the highest value at 100μmol photons m^-2 s^-1,and the lowest value at 150μmol photons m^-2 s^-1.The highest soluble protein and soluble carbohydrate levels at 100μmol photons m^-2 s^-1 for both T.weissflogii and Pyramimonas sp.（3）The specific growth rates of T.weissflogii and Pyramimonas sp.increased with the increase of nitrate concentration,and both reached the highest values at 100μmol L^-1.With the increase of nitrate concentration,the pigment content of T.weissflogii and Pyramimonas sp.decreased firstly and then increased,and reached the minimum value at 2μmol L^-1.（4）Temperature,light intensity,and nitrate concentration showed significant effects on the photosynthetic characteristics and nutritional value of T.weissflogii and Pyramimonas sp.and there were interactions among the three factors:the photosynthetic performance of T.weissflogii and Pyramimonas sp.was better under the combination of high temperature and high nitrate.Low nitrogen combined conditions were favorable for nutrient accumulation of T.weissflogii;The high light combined condition was beneficial to nutrient accumulation of Pyramimonas sp.Taking the bait microalgae nutritional value and photosynthetic characteristics as the breakthrough point,research we investigated the effects of three environmental factors（temperature,light intensity,and nitrate）respectively and their interaction on typical bait microalgae T.weissflogii and Pyramimonas sp.The results of the study could provide useful information for exploring the best culture conditions and improving the nutritional value of bait microalgae.There are 31 figures,12 tables,and 133 references in this thesis.