Effects Of Temperature And Solar Radiation On The Growth And Nitrate Reductase Activity Of Some Typical HAB Alga In ECS

Taking the four common alga （Skeletonema costatum, Chaetoceros curvisetus,Prorocentrum donghaiense, Karenia mikimotoi）, which are the chief criminals of thered tide, as our test objects, this paper studies the the NRA of these alga, their growthand the relation between NRA and the alga’s growth under different temperatures.Based on the experiment under the same temperature of20°C but under diverse lightintensities, we tentatively studied the NRA and the growth of Prorocentrumdonghaiense and Skeletonema costatum and the relation between their growth andNRA, through which we expect to analyze the characteristics of the alga’s growthunder different temperatures and light intensities in order to help illuminate the effectsof temperature and light intensity during the rising and ebbing of the red tide in EastSea. And the conclusions are summaried as follows:（1） All alga in this study, except Karenia mikimotoi, can grow under five giventemperatures, while the Karenia mikimotoi can’t grow normally at the lowesttemperature of10°C and the highest of30°C. The terminate biomass（Bf）,_maximumgrowing rate(μ_max) as well as the_maximum NRA(NRA_max) change in a similar trendwith the change of temperature. In a certain range of temperature, μ_maxand Bfincreasewith the rise of temperature, while beyond this range, they decreased. There is anoptimum temperature for each alga and the the temperature differed according to thealga. For example, the optimum temperature for Prorocentrum donghaiense andKarenia mikimotoi are about25°C, and those for Skeletonema costatum Chaetoceroscurvisetus are all around20°C. When under the same temperature, the μ_maxand(NRA_max)vof the four alga conform to the following rule: Skeletonemacostatum>Chaetoceros curvisetus>Prorocentrum donghaiense> Karenia mikimotoi. Itproves that temperature affects the alga’s ability of nitrate assimilation, and thus influence the growth of the alga.（2） P.donghaiense and S.costatum can grow normally in the solar radiationrange of30⁶0W·m^-2. The growth curve was "S" type. But when the solar radiation isbelow9W·m^-2, the two alga can hardly grow. The NRA_maxof the two alga appeares atthe moment when exponential growth phase is to turn up. In the range of0⁶0W·m^-2,the three parameters (NRA_max、μ_max、Bf) increase with increase of the light intensity,during which light inhibition don’t appear. Under the given light intensities by theexperiment, the (NRA_max)vof S.costatum is far greater than that of P.donghaiense, buttheir variation trends were alike with the change of light intensity. Based on this, wecan conclude that the solar radiation intensity effects the growing of marine algathrough affecting their cellular NRA.（3） The CV%of NRA_max、μ_maxof solar radiation is larger than temperature,according to which we can infer that the effect of light of these two alga maybeslightly bigger than the effect of temperature.