The Influence Of Environmental Factors On Uptake Kinetics Mechanism Of Ammonia And Growth Of Caulerpa Sertularioides

Marine macroalga can effectively absorb the nitrogen and phosphorus in aquaculture wastewater,as the indoor recirculation aquaculture system(RAS)has been established,the large algae for processing the water has some ornamental requirements.This article use Caulerpa srtularioides as the research object,analysis the influence of SGR and Chlorophyll content on Caulerpa sertularioides,under the follow culture conditions:different species of inorganic nitrogen,different concentration of nitrate and different salinity.At the same time,under the different light intensity conditions,we have researched characteristics of the uptake kinetics about ammonia nitrogen for Caulerpa sertularioides.The results showed that(1)Caulerpa sertularioides can use the nitrate best in three species of inorganic nitrogen.The group using ammonia nitrogen has gain better growth rate in early period than the other two groups,and has the larger max SGR,as 5.767±1.3810%/d,but the water quality has serious deterioration in later period,the macroalga died soon,average SGR in this group is 1.938±0.9387%/d;The group using nitrate has gain less growth rate than the ammonia group in early period,but the macroalga put on weigh for a long time,max SGR and average SGR are 4.619±1.2985%/d and 2.266±0.4117%/d,respectively.The max SGR and average SGR in the last group hasn’t significantly different with control group,which are 2.664±0.4345%/d and 1.169±0.4279%/d,respectively;The control group has the lowest growth rate,the max SGR and average SGR are 2.457±0.3029%/d and 0.993±0.2094%/d,respectively.(2)In six groups of different nitrate concentration,the SGR of Caulerpa sertularioides and nitrate concentration in water has positive correlation,in the group which nitrate concentration is 2.4mg/L,macroalga has the best growth rate,and the best max SGR and average SGR are 5.952±1.0809%/dand 2.994±0.9867%/d,respectively;in the group which nitrate concentration is 4.8mg/L,the SGR of macroalga is falling,the max SGR and average SGR are 5.024 ± 1.0621%/d and 2.307 ± 0.2094%/d,respectively.the group which nitrate concentration is 2.4mg/L has maximum value of Chlorophyll and Chlorophyll a,the value are 0.471 ±0.0334mg/g,0.278±0.0174 mg/g,respectively.(3)In the seven groups of salinity gradient,in the salinity of 15 ‰ and salinity of 45 ‰,Caulerpa sertularioides cannot survive,Caulerpa sertularioides can survive between salinity of 20 ‰ and salinity of 40 ‰.In different condition of salinity,average SGR and max SGR of macroalga has significant differences(P<0.05).In the salinity of 35 ‰,macroalga has the best growth rate,max SGR and average SGR are 8.172 ±1.2037%/d and 3.076 ± 0.4415%/d,respectively;average SGR of macroalga has no significant differences(P>0.05),between salinity of 30‰ and salinity of 40‰,as well as salinity of 20 ‰ and salinity of 25 ‰.In the salinity of 30‰,macroalga’s Chlorophyll and Chlorophyll a content has achieved maximum,0.5459±0.0605mg/g,0.3239±0.0357 mg/g,respectively.(4)The interval in sampling time is the period for adding ammonium nitrogen after 3-12 h,and the most appropriate interval is 3h.Using Michaelis-Menten equation fit the uptake kinetics curve of Caulerpa sertularioides under three light intensity conditions.The result show that,under lower light intensity conditions(3000Lux),macroalga’s Vmax is 2.9687μmol/g/h,Ks is 38.8903μmol/L;under medium light intensity conditions(6000Lux),macroalga’s Vmax is 4.1549μmol/g/h,Ks is 39.7701μmol/L;under lower light intensity conditions(9000Lux),macroalga’s Vmax is 2.7457μmol/g/h,Ks is 34.9443μmol/L.