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Marine Ecology Progress Series

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Measuring nitrogen fixation directly (with stable isotopes) and in situ (using a push-pull method) captures the effects of seagrass roots. Graphic: Lillian Aoki

Aoki LR, McGlathery KJ


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

Seagrass meadows are important sites for nitrogen (N) fixation in the coastal zone, yet traditional methods of measuring N fixation rely on indirect measurements of acetylene reduction and do not fully capture the stimulation of N fixation by seagrass roots. Here we used a novel in situ 30N2 push-pull method to measure N fixation directly in seagrass sediments. We found rates that greatly exceeded measurements made using laboratory acetylene reduction incubations but were comparable to direct measurements of N fixation in other submerged sediments. Based on these findings, we conclude that traditional measurements of N fixation in seagrass sediments may underestimate true rates. Future measurements should be made in situ in order to fully capture plant effects.


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