Optimality-based model of phytoplankton growth and diazotrophy.

Pahlow, Markus, Dietze, Heiner and Oschlies, Andreas (2013) Optimality-based model of phytoplankton growth and diazotrophy. Open Access Marine Ecology Progress Series, 489 . pp. 1-16. DOI 10.3354/meps10449.

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Abstract

The notion that excess phosphorus (P) and high irradiance favour pelagic diazotrophy is difficult to reconcile with diazotroph behaviour in laboratory experiments and also with the observed distribution of N2-fixing Trichodesmium, e.g. in the relatively nitrogen (N)-rich North Atlantic Ocean. Nevertheless, this view currently provides the state-of-the-art framework to understand both past dynamics and future evolution of the oceanic fixed N inventory. In an attempt to provide a consistent theoretical underpinning for marine autotrophic N2 fixation we derive controls of diazotrophy from an optimality-based model that accounts for phytoplankton growth and N2 fixation. Our approach differs from existing work in that conditions favourable for diazotrophy are not prescribed but emerge, indirectly, from trade-offs among energy and cellular resource requirements for the acquisition of P, N, and carbon. Our model reproduces laboratory data for a range of ordinary phytoplankton species and Trichodesmium. The model predicts that (1) the optimal strategy for facultative diazotrophy is switching between N2 fixation and using dissolved inorganic nitrogen (DIN) at a threshold DIN concentration; (2) oligotrophy, especially in P and under high light, favours diazotrophy; (3) diazotrophy is compatible with DIN:DIP supply ratios well above Redfield proportions; and (4) communities of diazotrophs competing with ordinary phytoplankton decouple emerging ambient and supply DIN:DIP ratios. Our model predictions appear in line with major observed patterns of diazotrophy in the ocean. The predicted importance of oligotrophy in P extends the present view of N2 fixation beyond a simple control by excess P in the surface ocean.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/FP7/282723
Additional Information: WOS:000323941000001 FP7-SPACE-2011-282723
Keywords: Nitrogen fixation; Phytoplankton; Optimality; Chain model; Resource allocation; Elemental composition
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
OceanRep > SFB 754 > B2
OceanRep > SFB 754
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.3354/meps10449
ISSN: 0171-8630
Projects: SPACE, SFB754, Future Ocean
Date Deposited: 26 Sep 2013 08:26
Last Modified: 25 Jun 2018 10:00
URI: http://oceanrep.geomar.de/id/eprint/22033

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