153
systems are often close to the limit of detection for the tracer
15
N 2 isotope uptake
method (Gradoville et al. 2017). Thus, the potential roles and importance of heterotrophic bacteria in N 2 fixation in the surface and deep ocean water column still need
to be resolved.
Estimates of basin scale and global N 2 fixation based on geochemical proxies
such as N*, P* or isotope mass balances should capture heterotrophic activity, but
those based on rates scaled from direct measurements of specific diazotrophs such
as Trichodesmim would not. As noted for observations in the ETSP (Bonnet et al.
2013) and the Mediterranean (Benavides et al. 2016), when sub-euphotic zone rates
are integrated they can account for >50% of the total water column activity
(Benavides et al. 2018a; Moisander et al. 2017).
As indicated above, less progress has been made in the benthos with regard to
further establishing and refining the broader biogeochemical importance of N 2 fixation at the basin or global scale. However, one area that has seen considerable progress is in the deep sea. N 2 fixation in these difficult to sample environments has been
the focus of recent research (e.g. Dekas et al. 2018, see Chap. 4). Novel diazotrophic
associations and deep water habitats have been uncovered. Putting the recent results
into a broader biogeochemical context will be the next challenge given the extent of
deep- sea habitats.
References
Andersson, B., Sundbäck, K., Hellman, M., Hallin, S., & Alsterberg, C. (2014). Nitrogen fixation in shallow-water sediments: Spatial distribution and controlling factors. Limnology and
Oceanography, 59(6), 1932–1944.
Benavides, M., & Voss, M. (2015). Five decades of N 2 fixation research in the North Atlantic
Ocean. Frontiers in Marine Science, 2, 40.
Benavides, M., Bonnet, S., Hernández, N., Martínez-Pérez, A. M., Nieto-Cid, M., et al. (2016).
Basin-wide N 2 fixation in the deep waters of the Mediterranean Sea. Global Biogeochemical
Cycles, 30(6), 952–961.
Benavides, M., Bednarz, V. N., & Ferrier-Pagès, C. (2017). Diazotrophs: Overlooked key players
within the coral symbiosis and tropical reef ecosystems? Frontiers in Marine Science, 4(10).
https://doi.org/10.3389/fmars.2017.00010.
Benavides, M., Bonnet, S., Berman-Frank, I., & Riemann, L. (2018a). Deep into oceanic N 2 fixation. Frontiers in Marine Science, 5, 108.
Benavides, M., Shoemaker, K. M., Moisander, P. H., Niggemann, J., Dittmar, T., et al. (2018b).
Aphotic N 2 fixation along an oligotrophic to ultraoligotrophic transect in the western tropical South Pacific Ocean. Biogeosciences, 15(9), 3107–3119. https://doi.org/10.5194/
bg- 15- 3107- 2018.
Bonnet, S., Dekaezemacker, J., Turk-Kubo, K. A., Moutin, T., Hamersley, R. M., et al. (2013).
Aphotic N 2 fixation in the eastern tropical South Pacific Ocean. PLoS One, 8(12), e81265.
Brandes, J. A., & Devol, A. H. (2002). A global marine-fixed nitrogen isotopic budget: Implications
for Holocene nitrogen cycling. Global Biogeochemical Cycles, 16(4), 1120. https://doi.
org/10.1029/2001GB001856.
Brown, S. M., & Jenkins, B. D. (2014). Profiling gene expression to distinguish the likely active
diazotrophs from a sea of genetic potential in marine sediments. Environmental Microbiology,
16(10), 3128–3142. https://doi.org/10.1111/1462- 2920.12403.
References
systems are often close to the limit of detection for the tracer
15
N 2 isotope uptake
method (Gradoville et al. 2017). Thus, the potential roles and importance of heterotrophic bacteria in N 2 fixation in the surface and deep ocean water column still need
to be resolved.
Estimates of basin scale and global N 2 fixation based on geochemical proxies
such as N*, P* or isotope mass balances should capture heterotrophic activity, but
those based on rates scaled from direct measurements of specific diazotrophs such
as Trichodesmim would not. As noted for observations in the ETSP (Bonnet et al.
2013) and the Mediterranean (Benavides et al. 2016), when sub-euphotic zone rates
are integrated they can account for >50% of the total water column activity
(Benavides et al. 2018a; Moisander et al. 2017).
As indicated above, less progress has been made in the benthos with regard to
further establishing and refining the broader biogeochemical importance of N 2 fixation at the basin or global scale. However, one area that has seen considerable progress is in the deep sea. N 2 fixation in these difficult to sample environments has been
the focus of recent research (e.g. Dekas et al. 2018, see Chap. 4). Novel diazotrophic
associations and deep water habitats have been uncovered. Putting the recent results
into a broader biogeochemical context will be the next challenge given the extent of
deep- sea habitats.
References
Andersson, B., Sundbäck, K., Hellman, M., Hallin, S., & Alsterberg, C. (2014). Nitrogen fixation in shallow-water sediments: Spatial distribution and controlling factors. Limnology and
Oceanography, 59(6), 1932–1944.
Benavides, M., & Voss, M. (2015). Five decades of N 2 fixation research in the North Atlantic
Ocean. Frontiers in Marine Science, 2, 40.
Benavides, M., Bonnet, S., Hernández, N., Martínez-Pérez, A. M., Nieto-Cid, M., et al. (2016).
Basin-wide N 2 fixation in the deep waters of the Mediterranean Sea. Global Biogeochemical
Cycles, 30(6), 952–961.
Benavides, M., Bednarz, V. N., & Ferrier-Pagès, C. (2017). Diazotrophs: Overlooked key players
within the coral symbiosis and tropical reef ecosystems? Frontiers in Marine Science, 4(10).
https://doi.org/10.3389/fmars.2017.00010.
Benavides, M., Bonnet, S., Berman-Frank, I., & Riemann, L. (2018a). Deep into oceanic N 2 fixation. Frontiers in Marine Science, 5, 108.
Benavides, M., Shoemaker, K. M., Moisander, P. H., Niggemann, J., Dittmar, T., et al. (2018b).
Aphotic N 2 fixation along an oligotrophic to ultraoligotrophic transect in the western tropical South Pacific Ocean. Biogeosciences, 15(9), 3107–3119. https://doi.org/10.5194/
bg- 15- 3107- 2018.
Bonnet, S., Dekaezemacker, J., Turk-Kubo, K. A., Moutin, T., Hamersley, R. M., et al. (2013).
Aphotic N 2 fixation in the eastern tropical South Pacific Ocean. PLoS One, 8(12), e81265.
Brandes, J. A., & Devol, A. H. (2002). A global marine-fixed nitrogen isotopic budget: Implications
for Holocene nitrogen cycling. Global Biogeochemical Cycles, 16(4), 1120. https://doi.
org/10.1029/2001GB001856.
Brown, S. M., & Jenkins, B. D. (2014). Profiling gene expression to distinguish the likely active
diazotrophs from a sea of genetic potential in marine sediments. Environmental Microbiology,
16(10), 3128–3142. https://doi.org/10.1111/1462- 2920.12403.
References