Dinitrogen fixation and primary productivity by carbonate and silicate reef sand communities of the Northern Red Sea
Dinitrogen fixation and primary productivity by carbonate and silicate reef sand communities of the Northern Red Sea
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DOI：
10.3354/meps11224
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发表时间：
2015-05-07
影响因子：
2.5
通讯作者：
Wild, Christian
中科院分区：
文献类型：
--
作者：
Bednarz, Vanessa N.;van Hoytema, Nanne;Wild, Christian
可渗透沉积物是珊瑚礁中具有高度生物活性的隔室。相关的密集微生物群落维持有机物的快速降解，从而在珊瑚礁内的营养循环中发挥关键作用。除了养分循环外，微生物群落还通过固氮（N-2）获得新的营养物质（如氮），但关于砂矿物学和关键环境因素对这一过程的影响的知识很少。因此，本研究量化了北红海珊瑚礁中相邻碳酸盐和硅酸盐砂的季节性N-2固定（通过乙炔还原）和总光合作用（通过O-2通量）。研究结果表明，碳酸盐砂的N-2固结率明显高于硅酸盐砂(分别为2.88和1.52 nmol C2H4 cm(-2) h(-1))，并且前者的季节性响应更为明显，这可能是由于其更高的渗透率、粒度和微生物丰度所致。环境光和有机质有效性是影响土壤氮素固结的主要环境因子。碳酸盐砂和硅酸盐砂表现出相似的总光合速率(270和233 nmol O-2 cm(-2) h(-1))，与N-2固定呈正相关（碳酸盐砂）或负相关（硅酸盐砂），可能是由于不同的重氮营养群落。碳酸盐砂上微生物垫的季节性出现使氮-2固定和总光合作用增加了一个数量级。每年平均而言，碳酸盐和硅酸盐砂通过N-2固定获得了约8%的光代谢N需求，微生物席群落通过N-2固定获得了约13%的光代谢N需求。
Permeable sediments are highly bioactive compartments in coral reefs. The associated dense microbial communities sustain fast degradation of organic matter, thereby playing a key role in nutrient recycling within the reef. Besides nutrient recycling, new nutrients (i.e. nitrogen) are acquired by dinitrogen (N-2) fixing microbial communities, but knowledge about the influence of sand mineralogy and key environmental factors on this process is scarce. Therefore, this study quantified seasonal N-2 fixation (via acetylene reduction) along with gross photosyn thesis (via O-2 fluxes) by adjacent carbonate and silicate sands in a Northern Red Sea coral reef. Findings revealed significantly higher N-2 fixation in carbonate than in silicate sands (2.88 and 1.52 nmol C2H4 cm(-2) h(-1), respectively) and a more pronounced seasonal response in the former, likely caused by its higher permeability, grain size and microbial abundance. Ambient light and organic matter availability were the main controlling environmental factors for sand-associated N-2 fixation. Carbonate and silicate sands showed similar gross photosynthesis rates (270 and 233 nmol O-2 cm(-2) h(-1)) that positively (carbonate sands) or negatively (silicate sands) correlated with N-2 fixation, likely due to different diazotrophic communities. Seasonal appearance of microbial mats on carbonate sands increased N-2 fixation and gross photosynthesis by up to one order of mag nitude. On an annual average, carbonate and silicate sands obtain similar to 8% and microbial mat communities obtain similar to 13% of their photo-metabolic N demand via N-2 fixation.