Burrowing deeper into benthic nitrogen cycling: the impact of bioturbation on nitrogen fixation coupled to sulfate reduction
Burrowing deeper into benthic nitrogen cycling: the impact of bioturbation on nitrogen fixation coupled to sulfate reduction
复制标题
DOI：
10.3354/meps08639
复制
发表时间：
2010-01-01
影响因子：
2.5
通讯作者：
Ziebis, Wiebke
中科院分区：
文献类型：
--
作者：
Bertics, Victoria J.;Sohm, Jill A.;Ziebis, Wiebke
生物固氮（N-2）是固定氮（N）进入海洋生物圈的主要输入，使其成为所有生物体生物功能的重要过程。由于生物有效氮往往限制海洋生产力，微生物过程导致其损失和增益（e。G.反硝化作用和N-2固定作用）在全球生态地球化学循环中起着重要作用。已知生物扰动会影响底栖氮循环，最常报告的是反硝化作用的增强和随后系统中N-2的损失。N-2固定在生物扰动研究中很少涉及。相反，沉积N-2固定通常被认为是重要的，在相对罕见的，局部的栖息地，如根际和光养微生物垫环境。然而，在海洋沉积物中固定N-2的潜力可能更为广泛。我们在这里表明，固氮酶活性可以非常高（高达5 nmol C2 H4 cm（-3）h（-1））在沿海沉积物中的鬼虾Neotrypaea californiensis的生物扰动和深度低于5厘米。综合地下N-2固定率高于之前在无植被河口沉积物中发现的固定率，并且与光合微生物垫和根际的固定率相当。抑制实验和遗传分析表明，该活性主要与硫酸盐还原有关。硫酸盐还原菌（SRB）广泛存在于海洋沉积物中，其中许多具有固定N-2的遗传能力。我们的研究结果表明，生物扰动沉积物中SRB的N-2固定可能是导致新的N输入到海洋沉积物中的重要过程。鉴于生物扰动和SRB在海洋沉积物中的普遍存在，这种被忽视的底栖N-2固定可能在海洋N和C循环中发挥重要作用。
Biological dinitrogen (N-2) fixation is the primary input of fixed nitrogen (N) into the marine biosphere, making it an essential process contributing to the biological functions of all organisms. Because biologically available N often limits marine productivity, microbial processes leading to its loss and gain (e. g. denitrification and N-2 fixation, respectively) play an important role in global biogeochemical cycles. Bioturbation is known to influence benthic N cycling, most often reported as enhancement of denitrification and a subsequent loss of N-2 from the system. N-2 fixation has rarely been addressed in bioturbation studies. Instead, sedimentary N-2 fixation typically has been considered important in relatively rare, localized habitats such as rhizosphere and phototrophic microbial mat environments. However, the potential for N-2 fixation in marine sediments may be more widespread. We show here that nitrogenase activity can be very high (up to 5 nmol C2H4 cm(-3) h(-1)) in coastal sediments bioturbated by the ghost shrimp Neotrypaea californiensis and at depths below 5 cm. Integrated subsurface N-2-fixation rates were greater than those previously found for un-vegetated estuarine sediments and were comparable to rates from photosynthetic microbial mats and rhizospheres. Inhibition experiments and genetic analysis showed that this activity was mainly linked to sulfate reduction. Sulfate-reducing bacteria (SRB) are widespread and abundant in marine sediments, with many possessing the genetic capacity to fix N-2. Our results show that N-2 fixation by SRB in bioturbated sediments may be an important process leading to new N input into marine sediments. Given the ubiquity of bioturbation and of SRB in marine sediments, this overlooked benthic N-2 fixation may play an important role in marine N and carbon (C) cycles.