Response Of Carbon Sinking In Marine Coccolithophores To Environmental Factors Related To Climate Change

In this thesis,the responses of the coccolithophore Emiliania huxleyi calcified strain NIWA1108 and E.huxleyi non-calcified strain PMLB to changes in five environmental drivers related to global climate change,including phosphate,nitrate,irradiance and pCO2,were examined.A series of semi-continuous incubation experiments were conducted in order to investigate the effects of changes in these environmental drivers on the physiological parameters that are involved in carbon production and sinking of E.huxleyi.In each experiment,only one environmental driver was manipulated at a time.The environmental conditions were set up as the following:nitrate concentration gradient:0.5,2,4,10,20,48 and 96 ?M;phosphate concentration gradient:0.1,0.4,2,6 and 10 ?M;irradiance gradient:50,200,500 and 1000 ?mol photons m-2 s-1;temperature gradient:10?,15?,20? and 25?;pCO2 gradient:400,800,1200 and 1500 ppm.The results suggest that,the cell and coccoshphere size and cellular particle organic(POC)content of the calcified E.huxleyi strain decreased with phosphate concentration increasing,in the same time the coccoliths became thinner,with increased sinking rate.In contrast,the cell size of the non-calcified E.huxleyi strain increased with increased phosphate concentration.With nitrate concentration increasing,the cell size of the calcified E.huxleyi strain decreased,but both the cellular POC content and the sinking rate were increased.While for the non-calcified strain,the cell size was increased,but cellular POC content was decreased with increased nitrate concentration.With rising irradiance levels,the cell size of the calcified strain increased,and the coccoliths became thicker,with the cellular POC content and sinking rate both increasing.However,the cell size and the sinking rate of the non-calcified strain both were decreased by increased irradiances.The coccosphere size,cellular POC content and sinking rate of the calcified strain were all decreased with elevated temperature.Similarly,the cell size and POC content of the non-calcified strain both decreased with temperature increasing,but the sinking rate was increased at the same time.Rising pCO2 reduced the cell size,cellular POC content and sinking rate of the calcified strain.For the non-calcified strain,increase in pCO2 also increased the cell size,but decreased the POC content and sinking rate.Overall,the research provides some scientific basis for understanding the response of carbon sinking of marine coccolithophores under changes of a set of environmental drivers related to global climate change,and provides supporting data for relevant predictive biogeochemical models.