Epping E, Kühl M
Max-Planck-Institut für Marine Mikrobiologie, Microsensor Research Group, Bremen, Germany.
Environ Microbiol. 2000 Aug;2(4):465-74. doi: 10.1046/j.1462-2920.2000.00129.x.
We have evaluated the effects of short-term changes in incident irradiance and temperature on oxygenic photosynthesis and oxygen consumption in a hypersaline cyanobacterial mat from the Ebro Delta, Spain, in which Microcoleus chthonoplastes was the dominant phototrophic organism. The mat was incubated in the laboratory at 15, 20, 25 and 30 degrees C at incident irradiances ranging from 0 to 1,000 micromol photons m(-2) s(-1). Oxygen microsensors were used to measure steady-state oxygen profiles and the rates of gross photosynthesis, which allowed the calculation of areal gross photosynthesis, areal net oxygen production, and oxygen consumption in the aphotic layer of the mat. The lowest surface irradiance that resulted in detectable rates of gross photosynthesis increased with increasing temperature from 50 micromol photons m(-2) s(-1) at 15 degrees C to 500 micromol photons m(-2) s(-1) at 30 degrees C. These threshold irradiances were also apparent from the areal rates of net oxygen production and point to the shift of M. chthonoplastes from anoxygenic to oxygenic photosynthesis and stimulation of sulphide production and oxidation rates at elevated temperatures. The rate of net oxygen production per unit area of mat at maximum irradiance, J0, did not change with temperature, whereas, JZphot, the flux of oxygen across the lower boundary of the euphotic zone increased linearly with temperature. The rate of oxygen consumption per volume of aphotic mat increased with temperature. This increase occurred in darkness, but was strongly enhanced at high irradiances, probably as a consequence of increased rates of photosynthate exudation, stimulating respiratory processes in the mat. The compensation irradiance (Ec) marking the change of the mat from a heterotrophic to an autotrophic community, increased exponentially in this range of temperatures.
我们评估了入射辐照度和温度的短期变化对西班牙埃布罗三角洲高盐度蓝藻席中氧光合作用和氧消耗的影响，该蓝藻席中，嗜盐栖泥绿菌是主要的光合生物。将该蓝藻席在实验室中于15、20、25和30摄氏度下培养，入射辐照度范围为0至1000微摩尔光子·米⁻²·秒⁻¹。使用氧微传感器测量稳态氧分布以及总光合作用速率，从而能够计算蓝藻席无光层中的面积总光合作用、面积净氧产生量和氧消耗量。导致可检测到的总光合作用速率的最低表面辐照度随着温度升高而增加，从15摄氏度时的50微摩尔光子·米⁻²·秒⁻¹增加到30摄氏度时的500微摩尔光子·米⁻²·秒⁻¹。这些阈值辐照度在净氧产生的面积速率中也很明显，表明嗜盐栖泥绿菌从无氧光合作用向有氧光合作用的转变，以及在较高温度下硫化物产生和氧化速率的刺激。在最大辐照度下，单位面积蓝藻席的净氧产生速率J0不随温度变化，而穿过真光层下边界的氧通量JZphot随温度线性增加。无光蓝藻席每体积的氧消耗速率随温度增加。这种增加在黑暗中发生，但在高辐照度下强烈增强，可能是光合产物渗出速率增加的结果，刺激了蓝藻席中的呼吸过程。标志着蓝藻席从异养群落向自养群落转变的补偿辐照度（Ec）在该温度范围内呈指数增加。
