Microsensor studies of photosynthesis and respiration in the symbiotic foraminifer Orbulina universa
Microsensor studies of photosynthesis and respiration in the symbiotic foraminifer Orbulina universa
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DOI：
10.1007/s002270050350
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发表时间：
1998-07
期刊：
影响因子：
2.4
通讯作者：
S. Rink;Michael Kühl;J. Bijma;H. Spero
中科院分区：
文献类型：
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作者：
S. Rink;Michael Kühl;J. Bijma;H. Spero
采用氧微电极和pH微电极研究了浮游有孔虫宇宙水藻及其鞭毛内共生生物的微环境。有孔虫壳周围有一个扩散边界层，限制了o2和质子从壳向周围海水的输运，反之亦然。由于共生光合作用，在饱和辐照下，在有孔虫的壳表面测量到高达206%的空气饱和度和高达8.8的pH值，即比环境海水高0.5个pH单位。在黑暗中，寄主-共生体系统的呼吸作用使壳表面的o2浓度降低到周围空气饱和水体氧含量的70%以下。在黑暗中，壳表面的pH值降至7.9。我们测量的平均总光合速率为8.5±4.0 nmol O2h−1有孔虫−1。净光合作用平均为5.3±2.7 nmol O2h−1。在光照条件下，计算呼吸速率达到3.9±1.9 nmol O2h−1，而在黑暗条件下，呼吸速率明显较低（1.7±0.7 nmol O2h−1）。光照-暗循环实验证明了共生体对光照条件变化的动态响应。总光合作用与标量辐照度曲线（pvse2）显示，光饱和辐照度（Ek）分别为75 μmol和137 μmol光子m−2s−1in 2 oo。分别universaspecimens。当辐照强度达到700 μmol光子m−2s−1时，没有观察到光合作用受到抑制。共生缔合的光补偿点为50 μmol光子m−2s−1。有孔虫内部的标量辐照度（Eo）的径向剖面测量表明，壳表面的标量辐照度（Ed）略有增加，达到入射辐照度（Ed）的105%。
Oxygen and pH microelectrodes were used to investigate the microenvironment of the planktonic foraminiferOrbulina universaand its dinoflagellate endosymbionts. A diffusive boundary layer surrounds the foraminiferal shell and limits the O2and proton transport from the shell to the ambient seawater and vice versa. Due to symbiont photosynthesis, high O2concentrations of up to 206% air saturation and a pH of up to 8.8, i.e. 0.5 pH units above ambient seawater, were measured at the shell surface of the foraminifer at saturating irradiances. The respiration of the host–symbiont system in darkness decreased the O2concentration at the shell surface to <70% of the oxygen content in the surrounding air-saturated water. The pH at the shell surface dropped to 7.9 in darkness. We measured a mean gross photosynthetic rate of 8.5 ± 4.0 nmol O2h−1foraminifer−1. The net photosynthesis averaged 5.3 ± 2.7 nmol O2h−1. In the light, the calculated respiration rates reached 3.9 ± 1.9 nmol O2h−1, whereas the dark respiration rates were significantly lower (1.7 ± 0.7 nmol O2h−1). Experimental light–dark cycles demonstrated a very dynamic response of the symbionts to changing light conditions. Gross photosynthesis versus scalar irradiance curves (PvsEocurves) showed light saturation irradiances (Ek) of 75 and 137 μmol photons m−2s−1in twoO. universaspecimens, respectively. No inhibition of photosynthesis was observed at irradiance levels up to 700 μmol photons m−2s−1. The light compensation point of the symbiotic association was 50 μmol photons m−2s−1. Radial profile measurements of scalar irradiance (Eo) inside the foraminifera showed a slight increase at the shell surface up to 105% of the incident irradiance (Ed).