MEPS 551:53-62 (2016)  -  DOI: https://doi.org/10.3354/meps11755

Significant nitrogen fixation activity associated with the phyllosphere of Mediterranean seagrass Posidonia oceanica: first report

Nona S. R. Agawin1,*, Pere Ferriol1, Callum Cryer2, Elena Alcon1, Antonio Busquets1, Eva Sintes3, Constanza Vidal1, Gabriel Moyà1

1Interdisciplinary Ecology Group, Biology Department, Universidad de las Islas Baleares, 07122 Palma de Mallorca, Spain
2School of Biological Sciences, University of Portsmouth, Portsmouth, Hampshire PO1 2DY, UK
3Department of Marine Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
*Corresponding author:

ABSTRACT: The present study provides first estimates of dinitrogen (N2) fixation activities associated with the phyllosphere of Posidonia oceanica in the Mediterranean Sea. N2 fixation rates in the phyllosphere reached values up to 2.53 µg N gDW h-1 or 15.2 mg N m-2 d-1 (integrated to daily rates and by areal basis), which is higher than most rates reported in the phyllosphere of tropical seagrasses. These rates can potentially supply the total N demand of P. oceanica and may contribute significantly to the N budget in the Mediterranean Sea. Our results showed differences in N2 fixation rates among leaf segments of different age with higher activities in older segments that were heavily epiphytized and higher activities during summer when epiphyte biomass accumulation was higher than in spring. N2 fixation activities occurred during day and night, suggesting that the community of N2 fixers in the phyllosphere of Posidonia oceanica is complex and is not attributable to a single group of diazotrophs. Molecular analysis of nifH genes (coding for the nitrogenase enzyme) of epiphytic samples in the phyllosphere of P. oceanica revealed bacterial nifH sequences, closely related to as-yet uncultured and unidentified bacteria. To support the ecological importance of N2 fixation in P. oceanica beds, more measurements with wider spatial and temporal scope are needed. 


KEY WORDS: Nitrogen fixation · Posidonia oceanica · Mediterranean Sea


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Cite this article as: Agawin NSR, Ferriol P, Cryer C, Alcon E and others (2016) Significant nitrogen fixation activity associated with the phyllosphere of Mediterranean seagrass Posidonia oceanica: first report. Mar Ecol Prog Ser 551:53-62. https://doi.org/10.3354/meps11755

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