High rates of microbial dinitrogen fixation and sulfate reduction associated with the Mediterranean seagrass Posidonia oceanica

Lehnen, Nadine; Marchant, Hannah K.; Schwedt, Anne; Milucka, Jana; Lott, Christian; Weber, Miriam; Dekaezemacker, Julien; Seah, Brandon K. B.; Hach, Philipp F.; Mohr, Wiebke; Kuypers, Marcel M. M.

doi:10.1016/j.syapm.2016.08.004

Cited by 39 publications

(45 citation statements)

References 56 publications

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“…Mesocosm experiments showed that C. nodosa is more resistant to warming than P. oceanica (Olsen et al, 2012), concurrent with thermal niche models (Chefaoui et al, 2016(Chefaoui et al, , 2018; however, a loss of 46.5 % in C. nodosa extension is predicted by 2100 under the worst-case warming scenario (Chefaoui et al, 2018). Although C. prolifera thrives well in warm waters, its photosynthesis is inhibited at temperatures above 30 • C (Lloret et al, 2008;Vaquer-Sunyer and Duarte, 2013), compromising its survival at temperatures above this threshold.…”

Section: N Garcias-bonet Et Al: Nitrogen Fixation In Mediterraneanmentioning

confidence: 80%

“…Nitrogen (N 2 ) fixation plays a fundamental role in balancing nutrient budgets at the basin scale in the Mediterranean Sea, with most of this N 2 fixation associated with P. oceanica seagrass meadows (Béthoux and Copin-Montégut, 1986). Indeed, endophytic nitrogen-fixing bacteria have been detected in roots of P. oceanica (Garcias-Bonet et al, 2012 and N 2 fixation has been reported in leaves and roots of P. ocean-ica (Agawin et al, 2016;Lehnen et al, 2016) and in situ incubations (Agawin et al, 2017). Therefore, the high productivity of P. oceanica in the oligotrophic Mediterranean waters is partially supported by N 2 fixation.…”

Section: N Garcias-bonet Et Al: Nitrogen Fixation In Mediterraneanmentioning

confidence: 99%

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Warming effect on nitrogen fixation in Mediterranean macrophyte sediments

et al. 2019

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Abstract. The Mediterranean Sea is warming faster than the global ocean, with important consequences for organisms and biogeochemical cycles. Warming is a major stressor for key marine benthic macrophytes. However, the effect of warming on marine N2 fixation remains unknown, despite the fact that the high productivity of macrophytes in oligotrophic waters is partially sustained by the input of new nitrogen (N) into the system by N2 fixation. Here, we assess the impact of warming on the N2 fixation rates of three key marine macrophytes: Posidonia oceanica, Cymodocea nodosa, and Caulerpa prolifera. We experimentally measured N2 fixation rates in vegetated and bare sediments at temperatures encompassing current summer mean (25 and 27 ∘C), projected summer mean (29 and 31 ∘C), and projected summer maximum (33 ∘C) seawater surface temperatures (SSTs) by the end of the century under a scenario of moderate greenhouse gas emissions. We found that N2 fixation rates in vegetated sediments were 2.8-fold higher than in bare sediments at current summer mean SST, with no differences among macrophytes. Currently, the contribution of N2 fixation to macrophyte productivity could account for up to 7 %, 13.8 %, and 1.8 % of N requirements for P. oceanica, C. nodosa, and C. prolifera, respectively. We show the temperature dependence of sediment N2 fixation rates. However, the thermal response differed for vegetated sediments, in which rates showed an optimum at 31 ∘C followed by a sharp decrease at 33 ∘C, and bare sediments, in which rates increased along the range of the experimental temperatures. The activation energy and Q10 were lower in vegetated than bare sediments, indicating the lower thermal sensitivity of vegetated sediments. The projected warming is expected to increase the contribution of N2 fixation to Mediterranean macrophyte productivity. Therefore, the thermal dependence of N2 fixation might have important consequences for primary production in coastal ecosystems in the context of warming.

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Section: N Garcias-bonet Et Al: Nitrogen Fixation In Mediterraneanmentioning

confidence: 80%

Section: N Garcias-bonet Et Al: Nitrogen Fixation In Mediterraneanmentioning

confidence: 99%

Warming effect on nitrogen fixation in Mediterranean macrophyte sediments

et al. 2019

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“…Posidonia oceanica take up phosphorus and nitrogen through roots and leaves (Fresi and Saggiomo, 1981;Lepoint et al, 2002). Nutrient uptake by roots, while supplemented by nitrogen-fixation (Garcias-Bonet et al, 2016), is diffusion-limited, and thus may be insufficient to meet nutrient requirements (Lepoint et al, 2002). Material deposited in seagrass meadows is typically low in nitrogen and phosphorus, but nevertheless over annual cycles can meet the demand of P. oceanica (Gacia et al, 2002).…”

Section: Potential For Nutrient Recycling Within the Canopymentioning

confidence: 99%

High Net Primary Production of Mediterranean Seagrass (Posidonia oceanica) Meadows Determined With Aquatic Eddy Covariance

et al. 2020

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We report primary production and respiration of Posidonia oceanica meadows determined with the non-invasive aquatic eddy covariance technique. Oxygen fluxes were measured in late spring at an open-water meadow (300 m from shore), at a nearshore meadow (60 m from shore), and at an adjacent sand bed. Despite the oligotrophic environment, the meadows were highly productive and highly autotrophic. Net ecosystem production (54 to 119 mmol m −2 d −1) was about one-half of gross primary production. In adjacent sands, net primary production was a tenth-to a twentieth smaller (4.6 mmol m −2 d −1). Thus, P. oceanica meadows are an oasis of productivity in unproductive surroundings. During the night, dissolved oxygen was depleted in the open-water meadow. This caused a hysteresis where oxygen production in the late afternoon was greater than in the morning at the same irradiance. Therefore, for accurate measurements of diel primary production and respiration in this system, oxygen must be measured within the canopy. Generally, these measurements demonstrate that P. oceanica meadows fix substantially more organic carbon than they respire. This supports the high rate of organic carbon accumulation and export for which the ecosystem is known.

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“…Our study further indicates that H. stipulacea is a very suitable substrate for diazotrophs that actively fix N and thus provide an additional N source to be used for plant production and growth. Recently, high N 2 fixation rates and a diverse community of diazotrophs have been reported for roots of the endemic Mediterranean seagrass P. oceanica (Agawin et al 2016;Garcias-Bonet et al 2016;Lehnen et al 2016), suggesting that N 2 fixation may support growth also in this primary producer. While this is likely, H. stipulacea possesses characteristics that are exceptional compared with other tropical and temperate seagrass species, such as a high affinity for NH 1 4 uptake, a similar uptake capacity and efficiency of leaves and roots and a high invasiveness potential in sites under eutrophic conditions (Alexandre et al 2014;van Tussenbroek et al 2016).…”

Section: Ecological Implicationsmentioning

confidence: 99%

N₂ fixation and primary productivity in a red sea Halophila stipulacea meadow exposed to seasonality

Cardini

Hoytema

Bednarz

et al. 2017

Limnology & Oceanography

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The tropical seagrass Halophila stipulacea exhibits a limited capacity to use nitrate, but has a high uptake capacity and efficiency for ammonium. Consequently, N 2 fixation by associated diazotrophic epiphytes may be important in providing ammonium needed for seagrass photosynthesis and growth. When exposed to seasonality, this association could provide a competitive advantage for H. stipulacea in relation to other seagrass species, but related knowledge is scarce. Here, we thus report measurements of net photosynthesis (O 2 fluxes) and N 2 fixation (acetylene reduction) associated with H. stipulacea from the Northern Red Sea over all four seasons of 2013. In parallel, we characterized the seagrass meadow areal extent, shoot and leaves density, and the leaf area index. Using this data, we quantified meadow net primary production and N 2 fixation and estimated the photo-metabolic N demand met by N 2 fixation at the community level. Results revealed a marked seasonality of meadow N 2 fixation, with rates ranging from 0.06 in winter to 4.60 mmol N m 22 d 21 in summer, i.e., an increase by two orders of magnitude. In summer, when nutrient concentrations in the water column were lowest and light intensity and temperature highest, there was a significant positive linear relationship between meadow net primary production and N 2 fixation, with the latter accounting for ca. 20% of the photo-metabolic N demand. These findings suggest that N 2 fixation by associated diazotrophic epiphytes can mitigate N limitation of H. stipulacea meadows under N scarcity. This trait may also favor the ongoing geographical expansion of H. stipulacea.

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High rates of microbial dinitrogen fixation and sulfate reduction associated with the Mediterranean seagrass Posidonia oceanica

Cited by 39 publications

References 56 publications

Warming effect on nitrogen fixation in Mediterranean macrophyte sediments

Warming effect on nitrogen fixation in Mediterranean macrophyte sediments

High Net Primary Production of Mediterranean Seagrass (Posidonia oceanica) Meadows Determined With Aquatic Eddy Covariance

N₂ fixation and primary productivity in a red sea Halophila stipulacea meadow exposed to seasonality

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High rates of microbial dinitrogen fixation and sulfate reduction associated with the Mediterranean seagrass Posidonia oceanica

Cited by 39 publications

References 56 publications

Warming effect on nitrogen fixation in Mediterranean macrophyte sediments

Warming effect on nitrogen fixation in Mediterranean macrophyte sediments

High Net Primary Production of Mediterranean Seagrass (Posidonia oceanica) Meadows Determined With Aquatic Eddy Covariance

N2 fixation and primary productivity in a red sea Halophila stipulacea meadow exposed to seasonality

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N₂ fixation and primary productivity in a red sea Halophila stipulacea meadow exposed to seasonality