181
• How does organic matter composition and dynamics affect N 2 fixation and how
will it change with global changes in C and N cycling?
Ecological/Biogeochemical
• To what extent does Fe availability limit N 2 fixation rates in the oceans and how
will that change in the future?
• Is N 2 fixation in the meso- and bathy-pelagic zones of a significant magnitude
relative to other inputs and outputs of the marine N cycle?
• What are the fates of different diazotrophs in the surface ocean and the relative
rates of their contribution to the microbial loop, food webs and vertical export?
How will these change in the future?
• What is the contribution of benthic N 2 fixation to the global marine N budget?
• What overall role does mesoscale variability play in basin scale N 2 fixation rates?
• How will climate change affect the balance of N 2 fixation and denitrification?
• How will anthropogenic impacts ranging from eutrophication, to global warming
to plastic pollution affect the microbiology of the oceans and N 2 fixation?
Methodological/Technological
• How do the issues of slow dissolution of substrate and contamination affect the
validity of past
15
N 2 uptake observations?
• Can problems with molecular methods be successfully adressed to reliably quantify cell abundances and activities?
• Can marine N 2 fixers be used to produce fertilizer N, subsidize mariculture and
promote bioremediation?
10.11 Closing Comments
While there have been important discoveries and major changes in our conceptual
models, many challenges yet remain in order to fully understand and predict the
trajectory of N 2 fixation in the oceans. These include detailed information on the
organisms, interactions and factors controlling this process. The coming decades
promise to yield exciting new insights and yet more shifts in paradigms of marine
N 2 fixation. Understanding N 2 fixation and its role in the N cycle of the oceans and
earth at large is critical for understanding and predicting the effects of global environmental changes on the biology and chemistry of the seas.
10.11 Closing Comments
• How does organic matter composition and dynamics affect N 2 fixation and how
will it change with global changes in C and N cycling?
Ecological/Biogeochemical
• To what extent does Fe availability limit N 2 fixation rates in the oceans and how
will that change in the future?
• Is N 2 fixation in the meso- and bathy-pelagic zones of a significant magnitude
relative to other inputs and outputs of the marine N cycle?
• What are the fates of different diazotrophs in the surface ocean and the relative
rates of their contribution to the microbial loop, food webs and vertical export?
How will these change in the future?
• What is the contribution of benthic N 2 fixation to the global marine N budget?
• What overall role does mesoscale variability play in basin scale N 2 fixation rates?
• How will climate change affect the balance of N 2 fixation and denitrification?
• How will anthropogenic impacts ranging from eutrophication, to global warming
to plastic pollution affect the microbiology of the oceans and N 2 fixation?
Methodological/Technological
• How do the issues of slow dissolution of substrate and contamination affect the
validity of past
15
N 2 uptake observations?
• Can problems with molecular methods be successfully adressed to reliably quantify cell abundances and activities?
• Can marine N 2 fixers be used to produce fertilizer N, subsidize mariculture and
promote bioremediation?
10.11 Closing Comments
While there have been important discoveries and major changes in our conceptual
models, many challenges yet remain in order to fully understand and predict the
trajectory of N 2 fixation in the oceans. These include detailed information on the
organisms, interactions and factors controlling this process. The coming decades
promise to yield exciting new insights and yet more shifts in paradigms of marine
N 2 fixation. Understanding N 2 fixation and its role in the N cycle of the oceans and
earth at large is critical for understanding and predicting the effects of global environmental changes on the biology and chemistry of the seas.
10.11 Closing Comments