High rates of N fixation in seagrass sediments measured via a direct 30N2 push-pull method

Marine ecology progress series

Lillian R. Aoki^1¹ 

[1] Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904, USA^1

关键词: Nitrogen fixation;    Seagrass;    Zostera marina;    Push-pull;    30N2;   

DOI  :  10.3354/meps12961

学科分类：海洋学与技术

来源: Inter-Research

【 摘 要 】

Highly productive seagrass meadows often occur in oligotrophic waters, and nitrogen (N) fixation may play a role in supporting the N demand of the meadows. To date, most studies of N fixation in seagrass sediments have relied on indirect measurements via the acetylene reduction technique. Recent measurements of N fixation in submerged estuarine sediments using direct methods (e.g. N2:Ar ratio) in laboratory core incubations have shown higher rates than acetylene reduction measurements. Direct methods have not yet been applied to seagrass sediments in situ. In this study, we used a new in situ 30N2 push-pull method to measure N fixation rates in seagrass sediments and compared those rates to traditional acetylene reduction slurries. On average, hourly rates of N fixation measured via the 30N2 push-pull method were more than an order of magnitude greater than the acetylene reduction rates during summer (388 and 7.8 µmol m-2 h-1, respectively). These push-pull rates exceeded other published rates of N fixation in seagrass sediments (measured via acetylene reduction) but were within the range of reported rates for direct measurements of N fixation in submerged estuarine sediments. These results indicate the need for further investigation of N fixation rates in seagrass sediments via direct and in situ measurements. In order to fully understand the role of seagrass meadows in coastal N cycling, it is critical to accurately determine the magnitude of N fixation that occurs in these highly productive ecosystems.

【 授权许可】

Unknown