164
Novel approaches for large-scale measurements include continuous sampling
(Cassar et al. 2018) or advanced mathematical techniques such as machine learning
(Tang et al. 2019). The unique optical signatures of some cyanobacterial diazotrophs such as Trichodesmium (Subramaniam et al. 1999) has allowed us to map
their distributions in tropical surface waters (Blondeau-Patissier et al. 2018;
McKinna 2015) and utilization of color sensors on unmanned aerial vehicles (UAVs/
drones) from land and ships will provide a new level of spatial resolution (Shang
et al. 2017). Similarly, deployment of autonomous vehicles with capabilities to
detect the distribution of certain marine diazotrophs have been developed and are
actively being deployed (Anderson et al. 2018).
The coming decades are sure to see new technological advances which will continue to improve our understanding of marine N 2 fixation.
9.6 Conclusions
Although there is much yet to be learned about N 2 fixation in the oceans, including
what the relative contributions are of different diazotrophs, and the magnitude of N 2
fixation relative to N losses, the global environment is changing rapidly primarily
due to climate change. Fundamental physical and chemical controls on N 2 fixation
need to be better understood in order to predict how N 2 fixation will change in the
future. In addition to direct effects of changes in temperature and pH, indirect
changes in nutrient distributions and fluxes are occurring although not wellunderstood. It is particularly difficult to predict since we do not entirely understand
the current mechanisms at play, how they have already changed, and more importantly how they will be affected by simultaneous changes in multiple environmental
factors. Critical to assessing current and predicted N 2 fixation are the continued
development of methods, particularly those that can address the large time and
space scales of the oceans. The future of marine N 2 fixation research, particularly
with relevance to environmental change, will present major challenges but also will
undoubtedly result in continued exciting discoveries leading to a fuller view of N 2
fixation in the oceans that will facilitate better predictive abilities.
References
Anderson, E. E., Wilson, C., Knap, A. H., & Villareal, T. A. (2018). Summer diatom blooms in
the eastern North Pacific gyre investigated with a long-endurance autonomous surface vehicle.
PeerJ, 6, e5387.
Aumont, O., & Bopp, L. (2006). Globalizing results from ocean in situ iron fertilization studies.
Global Biogeochemical Cycles, 20(2), 1.
Bakun, A. (1990). Global climate change and intensification of coastal ocean upwelling. Science,
247, 198–201.
Balch, W. M. (2018). The ecology, biogeochemistry, and optical properties of coccolithophores.
Annual Review of Marine Science, 10, 71–98.
9 Marine N 2 Fixation, Global Change and the Future
Novel approaches for large-scale measurements include continuous sampling
(Cassar et al. 2018) or advanced mathematical techniques such as machine learning
(Tang et al. 2019). The unique optical signatures of some cyanobacterial diazotrophs such as Trichodesmium (Subramaniam et al. 1999) has allowed us to map
their distributions in tropical surface waters (Blondeau-Patissier et al. 2018;
McKinna 2015) and utilization of color sensors on unmanned aerial vehicles (UAVs/
drones) from land and ships will provide a new level of spatial resolution (Shang
et al. 2017). Similarly, deployment of autonomous vehicles with capabilities to
detect the distribution of certain marine diazotrophs have been developed and are
actively being deployed (Anderson et al. 2018).
The coming decades are sure to see new technological advances which will continue to improve our understanding of marine N 2 fixation.
9.6 Conclusions
Although there is much yet to be learned about N 2 fixation in the oceans, including
what the relative contributions are of different diazotrophs, and the magnitude of N 2
fixation relative to N losses, the global environment is changing rapidly primarily
due to climate change. Fundamental physical and chemical controls on N 2 fixation
need to be better understood in order to predict how N 2 fixation will change in the
future. In addition to direct effects of changes in temperature and pH, indirect
changes in nutrient distributions and fluxes are occurring although not wellunderstood. It is particularly difficult to predict since we do not entirely understand
the current mechanisms at play, how they have already changed, and more importantly how they will be affected by simultaneous changes in multiple environmental
factors. Critical to assessing current and predicted N 2 fixation are the continued
development of methods, particularly those that can address the large time and
space scales of the oceans. The future of marine N 2 fixation research, particularly
with relevance to environmental change, will present major challenges but also will
undoubtedly result in continued exciting discoveries leading to a fuller view of N 2
fixation in the oceans that will facilitate better predictive abilities.
References
Anderson, E. E., Wilson, C., Knap, A. H., & Villareal, T. A. (2018). Summer diatom blooms in
the eastern North Pacific gyre investigated with a long-endurance autonomous surface vehicle.
PeerJ, 6, e5387.
Aumont, O., & Bopp, L. (2006). Globalizing results from ocean in situ iron fertilization studies.
Global Biogeochemical Cycles, 20(2), 1.
Bakun, A. (1990). Global climate change and intensification of coastal ocean upwelling. Science,
247, 198–201.
Balch, W. M. (2018). The ecology, biogeochemistry, and optical properties of coccolithophores.
Annual Review of Marine Science, 10, 71–98.
9 Marine N 2 Fixation, Global Change and the Future