1
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
J. P. Zehr, D. G. Capone, Marine Nitrogen Fixation,
https://doi.org/10.1007/978-3-030-67746-6_1
Chapter 1
Nitrogen Fixation in the Marine
Environment
Nitrogen (N 2 ) fixation is an important reaction in the elemental cycle of nitrogen
(N). N 2 fixation, whether abiologically catalysed in the atmosphere, industrially
produced or biologically mediated by microorganisms in the environment, is an
important nutrient input for terrestrial and aquatic environments, and balances N
losses to the atmosphere through denitrification, sequestration in soils and runoff
and sedimentation in the oceans (Fig. 1.1).
Biogeochemical cycles move elements from rocks and soils to freshwaters, the
oceans, and the atmosphere and among the major habitats and ecosystems on Earth.
The elements of biological materials in life, the macro-nutrients and trace elements,
cycle from one chemical form to another (different molecules), and for many of the
elements (including N) among different oxidation and physical (solid, liquid, gas)
states (Schlesinger and Bernhardt 2013). These transformations contribute to their
relative biological availability and the habitability of the planet. Particularly critical
for life are carbon (C), nitrogen (N), sulphur (S), phosphorus (P), oxygen (O),
hydrogen (H) and a number of trace elements that are all used in the organic molecules of life as we know it on Earth, including carbohydrates, lipids, proteins and
nucleic acids. These elements have reservoirs in living and dead organic and inorganic forms in terrestrial (e.g. soils and rocks), water and even the atmosphere
(Schlesinger and Bernhardt 2013). Many, if not most, of the chemical transformations are catalysed by organisms, most of them microbes (Falkowski 2015;
Falkowski et al. 2008). The individual reactions themselves are controlled by different physical, chemical and biological factors, making the relative availability of
individual elements vary in both time and space. The composite effect of these
changes in state (chemical, physical and redox) result in complex cycles for many
of the elements. Moreover, there are significant interactions of major nutrient species which bridge two or more cycles and thereby make for complex interconnections among the cycles. These characteristics have important implications for life in
ecosystems. One of the most important factors is O 2 availability, which can itself
define the nature of specific environments (e.g. oxic vs. anoxic) which will in turn
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
J. P. Zehr, D. G. Capone, Marine Nitrogen Fixation,
https://doi.org/10.1007/978-3-030-67746-6_1
Chapter 1
Nitrogen Fixation in the Marine
Environment
Nitrogen (N 2 ) fixation is an important reaction in the elemental cycle of nitrogen
(N). N 2 fixation, whether abiologically catalysed in the atmosphere, industrially
produced or biologically mediated by microorganisms in the environment, is an
important nutrient input for terrestrial and aquatic environments, and balances N
losses to the atmosphere through denitrification, sequestration in soils and runoff
and sedimentation in the oceans (Fig. 1.1).
Biogeochemical cycles move elements from rocks and soils to freshwaters, the
oceans, and the atmosphere and among the major habitats and ecosystems on Earth.
The elements of biological materials in life, the macro-nutrients and trace elements,
cycle from one chemical form to another (different molecules), and for many of the
elements (including N) among different oxidation and physical (solid, liquid, gas)
states (Schlesinger and Bernhardt 2013). These transformations contribute to their
relative biological availability and the habitability of the planet. Particularly critical
for life are carbon (C), nitrogen (N), sulphur (S), phosphorus (P), oxygen (O),
hydrogen (H) and a number of trace elements that are all used in the organic molecules of life as we know it on Earth, including carbohydrates, lipids, proteins and
nucleic acids. These elements have reservoirs in living and dead organic and inorganic forms in terrestrial (e.g. soils and rocks), water and even the atmosphere
(Schlesinger and Bernhardt 2013). Many, if not most, of the chemical transformations are catalysed by organisms, most of them microbes (Falkowski 2015;
Falkowski et al. 2008). The individual reactions themselves are controlled by different physical, chemical and biological factors, making the relative availability of
individual elements vary in both time and space. The composite effect of these
changes in state (chemical, physical and redox) result in complex cycles for many
of the elements. Moreover, there are significant interactions of major nutrient species which bridge two or more cycles and thereby make for complex interconnections among the cycles. These characteristics have important implications for life in
ecosystems. One of the most important factors is O 2 availability, which can itself
define the nature of specific environments (e.g. oxic vs. anoxic) which will in turn