Biotic stoichiometric controls on the deep ocean N:P ratio
We re-examine what controls the deep ocean N:P ratio in the light of recent findings that the C:N:P stoichiometry of phytoplankton varies with growth rate, nutrient and light limitation, species and phylum, and that N<sub>2</sub>-fixation may be limited by Fe, temperature and/or light in...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2007-06-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/4/353/2007/bg-4-353-2007.pdf |
| _version_ | 1818242118170181632 |
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| author | T. M. Lenton C. A. Klausmeier |
| author_facet | T. M. Lenton C. A. Klausmeier |
| author_sort | T. M. Lenton |
| collection | DOAJ |
| description | We re-examine what controls the deep ocean N:P ratio in the light of
recent findings that the C:N:P stoichiometry of phytoplankton varies
with growth rate, nutrient and light limitation, species and phylum,
and that N<sub>2</sub>-fixation may be limited by Fe, temperature and/or
light in large parts of the world ocean. In particular, we assess
whether a systematic change in phytoplankton stoichiometry can alter
the deep ocean N:P ratio. To do this we adapt recent models to
include non-Redfieldian stoichiometry of phytoplankton and
restriction of N<sub>2</sub>-fixers to a fraction of the surface ocean. We
show that a systematic change in phytoplankton C:N:P can alter the
concentrations of NO<sub>3</sub> and PO<sub>4</sub> in the deep ocean but cannot
greatly alter their ratio, unless it also alters the N:P threshold
for N<sub>2</sub>-fixation. This occurs if competitive dynamics set the
N:P threshold for N<sub>2</sub>-fixation, in which case it remains close
to the N:P requirement of non-fixers (rather than that of
N<sub>2</sub>-fixers) and consequently so does the deep ocean N:P ratio.
Then, even if N<sub>2</sub>-fixers are restricted to a fraction of the
surface ocean, they reach higher densities there, minimising
variations in deep ocean N:P. Theoretical limits on the N:P
requirements of phytoplankton suggest that whilst the deep ocean has
been well oxygenated (i.e. since the Neoproterozoic, with the
possible exception of Oceanic Anoxic Events), its N:P ratio is
unlikely to have varied by more than a factor of two in either
direction. Within these bounds, evolutionary changes in
phytoplankton composition, and increased phosphorus weathering due
to the biological colonisation of the land surface, are predicted to
have driven long-term changes in ocean composition. |
| first_indexed | 2024-12-12T13:40:09Z |
| format | Article |
| id | doaj.art-57df11a8248d4895bef2697634f26df4 |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-12-12T13:40:09Z |
| publishDate | 2007-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-57df11a8248d4895bef2697634f26df42022-12-22T00:22:49ZengCopernicus PublicationsBiogeosciences1726-41701726-41892007-06-014335336710.5194/bg-4-353-2007Biotic stoichiometric controls on the deep ocean N:P ratioT. M. Lenton0C. A. Klausmeier1School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UKW. K. Kellogg Biological Station, Michigan State University, Hickory Corners, MI 49060, USAWe re-examine what controls the deep ocean N:P ratio in the light of recent findings that the C:N:P stoichiometry of phytoplankton varies with growth rate, nutrient and light limitation, species and phylum, and that N<sub>2</sub>-fixation may be limited by Fe, temperature and/or light in large parts of the world ocean. In particular, we assess whether a systematic change in phytoplankton stoichiometry can alter the deep ocean N:P ratio. To do this we adapt recent models to include non-Redfieldian stoichiometry of phytoplankton and restriction of N<sub>2</sub>-fixers to a fraction of the surface ocean. We show that a systematic change in phytoplankton C:N:P can alter the concentrations of NO<sub>3</sub> and PO<sub>4</sub> in the deep ocean but cannot greatly alter their ratio, unless it also alters the N:P threshold for N<sub>2</sub>-fixation. This occurs if competitive dynamics set the N:P threshold for N<sub>2</sub>-fixation, in which case it remains close to the N:P requirement of non-fixers (rather than that of N<sub>2</sub>-fixers) and consequently so does the deep ocean N:P ratio. Then, even if N<sub>2</sub>-fixers are restricted to a fraction of the surface ocean, they reach higher densities there, minimising variations in deep ocean N:P. Theoretical limits on the N:P requirements of phytoplankton suggest that whilst the deep ocean has been well oxygenated (i.e. since the Neoproterozoic, with the possible exception of Oceanic Anoxic Events), its N:P ratio is unlikely to have varied by more than a factor of two in either direction. Within these bounds, evolutionary changes in phytoplankton composition, and increased phosphorus weathering due to the biological colonisation of the land surface, are predicted to have driven long-term changes in ocean composition.http://www.biogeosciences.net/4/353/2007/bg-4-353-2007.pdf |
| spellingShingle | T. M. Lenton C. A. Klausmeier Biotic stoichiometric controls on the deep ocean N:P ratio Biogeosciences |
| title | Biotic stoichiometric controls on the deep ocean N:P ratio |
| title_full | Biotic stoichiometric controls on the deep ocean N:P ratio |
| title_fullStr | Biotic stoichiometric controls on the deep ocean N:P ratio |
| title_full_unstemmed | Biotic stoichiometric controls on the deep ocean N:P ratio |
| title_short | Biotic stoichiometric controls on the deep ocean N:P ratio |
| title_sort | biotic stoichiometric controls on the deep ocean n p ratio |
| url | http://www.biogeosciences.net/4/353/2007/bg-4-353-2007.pdf |
| work_keys_str_mv | AT tmlenton bioticstoichiometriccontrolsonthedeepoceannpratio AT caklausmeier bioticstoichiometriccontrolsonthedeepoceannpratio |