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首页> 外文期刊>european journal of phycology >Photosynthesis and nitrogen fixation in a cyanobacterial bloom in the Baltic Sea
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Photosynthesis and nitrogen fixation in a cyanobacterial bloom in the Baltic Sea

机译：波罗的海蓝藻水华中的光合作用和固氮

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Daily integrals of photosynthesis by a cyanobacterial bloom in the Baltic Sea, during the summer of 1993, were calculated from the vertical distributions of light, temperature and the organisms in the water column and from photosynthesis/irradiance curves of picoplanktonic and diazotrophic cyanobacteria isolated from the community. The distribution of chlorophyllain size-classes 20#x200A;#xB5;m and 20#x200A;#xB5;m was monitored over 9 days that included a deep mixing event followed by calm. Picocyanobacteria formed 70 of the cyanobacterial biomass and contributed 56 of the total primary production. Of the filamentous diazotrophs that formed the other 30,Aphanizomenoncontributed 28 and aNodularia-containing fraction 16 of the primary production. For the whole population there was little change in standardized photosynthetic O2production, which remained at about 31#x200A;mmol#x200A;m#x2212;2before and after the mixing event. There were differences, however, between the classes of cyanobacteria: in picocyanobacteria primary production hardly changed, while inAphanizomenonit increased by 2.6 and inNodulariait fell below zero. Total phytoplankton photosynthesis was strongly dependent on total daily insolation with the compensation point at a photon insolation of 22.7#x200A;mol#x200A;m#x2212;2#x200A;d#x2212;1. Similar analyses of N2fixation showed much less dependence on depth distribution of light and biomass:Aphanizomenonfixed about twice as much N2asNodulariatheir; their fixation exceeded their own N demand by about 12. Together, these species contributed 49 of the total N demand of the phytoplankton population. Computer models based on the measured light attenuation and photosynthetic coefficients indicate that growth of the cyanobacterial population could occur only in the summer months when the critical depth of the cyanobacteria exceeds the depth of mixing.
机译：1993年夏季，波罗的海蓝藻水华的光合作用的日积分是根据光、温度和水柱中生物的垂直分布以及从群落中分离出来的皮浮游和重氮营养蓝藻的光合作用/辐照度曲线计算得出的。在9天内监测叶绿素大小等级20μm的分布，包括深度混合事件，然后是平静事件。纤蓝藻占蓝藻生物量的70%，占初级生产总量的56%。在形成其他30%的丝状重氮菌中，Aphanizomenon贡献了28%和含有结节菌的部分的16%。对于整个群体来说，标准化光合O2产生几乎没有变化，在混合事件前后保持在约31 mmol m−2。然而，蓝藻的类别之间存在差异：在微藻中，初级产量几乎没有变化，而inAphanizomenonit增加了2.6，而inNodulariait降至零以下。浮游植物的光合作用总量与日日照总量密切相关，当光子日照量为22.7 mol m−2 d−1时，补偿点为22.7 mol m−2 d−1。对 N2 固定的类似分析表明，对光和生物量深度分布的依赖性要小得多：Aphanizomenonfixed 的 N2 大约是 Nodulariathir 的两倍;他们的固定量超过了他们自己的氮需求量约12%。这些物种合计贡献了浮游植物种群总氮需求的49%。基于测量的光衰减和光合系数的计算机模型表明，蓝藻种群的增长只能发生在蓝藻临界深度超过混合深度的夏季。

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