Studies On The Impact Of Carbon Dioxide And Other Environmental Factors On Photosynthetic Characteristics And Growth Of Gracilaria Chouae

As the planet’s largest active carbon storeroom, although ocean has unceasingly absorbed CO2 from the atmosphere to ease the global warming at the maximum limitation, it makes the average p H value of the surface waters has decreased from 8.2 at the beginning of the industrial revolution to its current 8.1, and the value will be dropped to 7.9 or 7.8 at the end of 21 century.Marine ecosystems will be singnificantly affected. Large sea algae is about 10% of the total primary productivity, it plays an important role in the carbon cycle for offshore ecosystem, so the increasing CO2 concentration of atmospheric will affect a series of physiological activities such as large algae growth, photosynthetic carbon and nutrient absorption. In this study, it not only investigated different CO2 and environmental factors have effected on the G.chouae growth, biochemical composition and photosynthetic carbon sequestration ability,but aslo formed different atmospheric environment to study diurnal variation regularity of water inorganic carbon utilization of gracilaria. Some crucial results as following:1.Different intensity light and nutrient levels can affect G.chouae photosynthetic carbon sequestration.The change of water dissolved oxygen and the carbonate systemn were measured to study the effects on G.chouae photosynthetic carbon sequestration ability in different intensity light and nutrient levels and their interaction.There were three gradient intensity lighting: 40、100 and 160μ mol·m-2·s-1;Na NO3 had four gradient:control, 100、300 and 500μ mol·L-1, KH2PO4 was added as 1:10, each setting had three lines.After 3 h, the G.chouae photosynthetic oxygen production rate(RO,μmol?g-1·h-1), carbon sequestration rate(RDIC,μmol?g-1·h-1),CO2 absorption rate(RCO2,μmol?g-1·h-1), and the absorption rate of HCO3-(RHCO3μmol?g-1·h-1) etc were calculated according to the change of the parameters in the water.The results indicated:light intensity, nutrient and both of their interaction have significantly influence on the G.chouae photosynthetic carbon sequestration ability(P < 0.05), and light intensity is the key influence factors.RO and RDIC of the G.chouae were the highest in light intensity 100μ mol·m-2·s-1、 nutrient levels 100μ mol·L-1.RO and RDIC rised gradually with the increasing of light intensity, and tend to be stable, but they fell slightly under the strong lighting.Under low lightting, increasing nutrient had no significant effec on RO and RDIC(P > 0.05), with the increasing of nutrient in 100 and 160μ mol·m-2·s-1 group, RO and RDIC rised gradually and tends to be stable, but in the high nutrient group the value fell slightly.RCO2 and RHCO3 had shown the same tendency.2. G.chouae had diurnal variation by the use of water inorganic carbon in different CO2 concentrations condition.It supposed that different CO2 concentrations would affect sea carbonate system, CO2 absorption and G.chouae physiological. There were two CO2 concentrations(400μ atm and 800μ atm), each group repeated three times through 24 h disposed and the dark cycle was 12L:12D, water samples were measured after 3 h once a time to calculate p H, total alkalinity and dissolved oxygen,ect.Results had shown that algae can significantly affect aquatic carbonate system in the two kinds of circumstances. In days of high CO2 concentration, DIC, HCO3- and CO2(aq) decreased significantly higher than that of control group, higher than about 19%, 10% and 19% respectively,and three parameters tended to be consistent in two treatment groups, and at the end of the light period, three values were stability at about 2100μ mol·L-1、1720μmol·L-1and 5.3μ mol·L-1, in the dark, this three parameters is stable, its content gradually increases and the growth of high CO2 group was significantly higher than that of control group(P < 0.05), but the gap is far less than in the daytime.During the period of 24 h the value of F was negative, the sea water kept uptake of CO2 all the way, the maximum F value of two groups were-3.05 mmol m-2?d-1and-5.55 mmol?m-2?d-1,the experiment group was 82% higher than the control group.Meanwhile, the carbon caquisition rate and the respiratory rate of G. chouae at high CO2 concentration were higher than at the controlgroup.3. Effects of carbon and nitrogen enrichment on growth and biochemical compositions in G. chouae.G. chouae was exposed in two carbon processing concentrations of 800 μatm CO2(enhanced), 400 μatm CO2(as control), and in four N processing of 100, 300 and 500 μ mol·L-1 NO3--N(enhanced), 10 μ mol·L-1 NO3--N(as control), with three replicates for each group. The culture density of G. chouae was 1 g·L-1. The algae were cultured under 100 μ mol photons·m-2·s-1 illuminated by incandescent tubes for 12:12 h photoperiod and at 20℃. The culture seawater was aerated continuously and renewed every two days. Differences of seaweed growth, soluble sugar(SS), soluble protein(SP), phycoerythrin(PE), chlorophyll a(Chla), total nitrogen(TC) and total carbon(TN) were measured 10 days after being disposed. The results indicated that an enhanced C and N were proposed to increase growth of the seaweed, the special growth rate(SGR) reached its peak(11.70 %·d-1) in the treatment of 800 μ l·L-1 CO2 and 100 μ mol·L-1 NO3--N; High CO2 levels induced the decrease of SP、PE and Chla content, whereas increasing SS content; With the density increase of Na NO3, PE and SP gradually increased, SS gradually reduced, Chla had no significant change(P > 0.05). Contents of TN was increasing, but TC and C/N were decreasing with a increasing Na NO3. TN and TC showed significant negative correlation in G. chouae(P < 0.05). These results showed that ocean acidification promotes the growth of G. chouae and directly affects its physiological and biochemical characteristics. The growth rate of G. chouae stayed at a high level under the condition of high N and P. Therefore, G. chouae can be considered as a suitable bioremediation species for artificial culture in the eutrophication regions.