The significance of nitrogen fixation to new production during early summer in the Baltic Sea
The significance of nitrogen fixation to new production during early summer in the Baltic Sea
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波罗的海初夏固氮对新产量的重要性
DOI：
10.5194/bg-4-63-2007
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发表时间：
2006
期刊：
影响因子：
4.9
通讯作者：
B. Bergmann
中科院分区：
文献类型：
--
作者：
U. Ohlendieck;K. Gundersen;M. Meyerhöfer;P. Fritsche;K. Nachtigall;B. Bergmann
抽象。1998年和1999年6月至7月在波罗的海进行了为期9天的样带巡航，测定了氮（N2）固定率和初级生产率。假设蓝藻水华的早期阶段持续了一个月，总的N2固定率为新产量贡献了15 mmol N m−2（1998年）和33 mmol N m−2（1999年）（Dugdale和Goering，1967）。这比同一地区的其他年度估计（7月中旬至10月中旬）多12-26%。观测站之间的变化，在总氮固定和初级生产力大大强调需要多个站点和季节性采样策略在波罗的海的海洋地球化学研究。大部分来自N2固定的新N由丝状蓝藻贡献。平均而言，在1998年（73%）和1999年（81%），>20 µm的蓝藻细胞能够通过N2固定提供其生长所需的大部分氮。然而，站间变异性很高，范围从28-150%的N需要满足初级生产的C掺入率。在丝状蓝藻细胞的摩尔C：N速率掺入比（C：NRATE）是可变的（范围7-28），平均几乎两倍的雷德菲尔德比（6.6），在这两年。由于在丝状蓝藻细胞的C：N摩尔质量比（C：NMASS）一般低于C：NRATE在一些站，我们建议，固氮菌纳入过量的C在短期的基础上（碳水化合物压载和浮力调节），释放氮或利用其他再生的N营养源。测定的总N2固定率仅占13%（范围4-24）在1998年和18%（范围2-45）在1999年的社区初级生产所需的N量的一小部分。平均9%和15%的总N2固定在细胞中
Abstract. Rates of dinitrogen (N2) fixation and primary production were measured during two 9 day transect cruises in the Baltic proper in June–July of 1998 and 1999. Assuming that the early phase of the bloom of cyanobacteria lasted a month, total rates of N2 fixation contributed 15 mmol N m−2 (1998) and 33 mmol N m−2 (1999) to new production (sensu Dugdale and Goering, 1967). This constitutes 12–26% more new N than other annual estimates (mid July–mid October) from the same region. The between-station variability observed in both total N2 fixation and primary productivity greatly emphasizes the need for multiple stations and seasonal sampling strategies in biogeochemical studies of the Baltic Sea. The majority of new N from N2 fixation was contributed by filamentous cyanobacteria. On average, cyanobacterial cells >20 µm were able to supply a major part of their N requirements for growth by N2 fixation in both 1998 (73%) and 1999 (81%). The between-station variability was high however, and ranged from 28–150% of N needed to meet the rate of C incorporation by primary production. The molar C:N rate incorporation ratio (C:NRATE) in filamentous cyanobacterial cells was variable (range 7–28) and the average almost twice as high as the Redfield ratio (6.6) in both years. Since the molar C:N mass ratio (C:NMASS) in filamentous cyanobacterial cells was generally lower than C:NRATE at a number of stations, we suggest that the diazotrophs incorporated excess C on a short term basis (carbohydrate ballasting and buoyancy regulation), released nitrogen or utilized other regenerated sources of N nutrients. Measured rates of total N2 fixation contributed only a minor fraction of 13% (range 4–24) in 1998 and 18% (range 2–45) in 1999 to the amount of N needed for the community primary production. An average of 9 and 15% of total N2 fixation was found in cells