Nutrient limitation of primary productivity in the Southeast Pacific (BIOSOPE cruise)

Bonnet, Sophie; Guieu, Cécile; Bruyant, Flavienne; Prášil, Ondřej; Wambeke, F. Van; Raimbault, Patrick; Moutin, Thierry; Grob, Carolina; Gorbunov, Maxim Y.; Zehr, Jonathan P.; Masquelier, Sylvie; Garczarek, Laurence; Claustre, Hervé

doi:10.5194/bg-5-215-2008

Cited by 125 publications

(125 citation statements)

References 51 publications

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“…Nevertheless, in this area, picophytoplankton cell abundances (Grob et al 2007) and P incorporation rates also increased in the bottom layer of the euphotic zone (between 3 and 1% PAR). These results suggest that the majority of the picophytoplankton lived in the bottom layer of the euphotic zone, which was located at the vicinity of the nitracline, so enabling the smaller phytoplankton to take advantage of their large surface area to volume ratio to access N, the limiting nutrient in the SPG (Bonnet et al 2008). The accumulation of a picophytoplankton biomass at the level of 1% PAR is common to other oligotrophic gyres in the world's oceans (Teira et al 2005).…”

Section: Role Of Microorganisms In the Carbon Budgetmentioning

confidence: 84%

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Carbon and phosphate incorporation rates of microbial assemblages in contrasting environments in the Southeast Pacific

Duhamel¹,

Moutin²

2009

Mar. Ecol. Prog. Ser.

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Size-fractionated chlorophyll a (chl a) was determined along with carbon (C) and phosphate (P) incorporation rates over a west-east transect in the Southeast Pacific (between 146.36°W and 72.49°W). A clear longitudinal gradient was observed for both chl a and C and P incorporation rates from the productive areas, near the Marquesas Islands and the Chilean upwelling, to the hyperoligotrophic area associated with the central part of the Southeast Pacific Gyre (SPG). The 0.2-0.6 µm fraction represented 15 to 43% (29 ± 7% mean ± SD, n = 24) of the P incorporation rate along the transect, suggesting that heterotrophic bacteria were important factors in the P cycle as dissolved inorganic P consumers. Small-sized cells (< 2 µm) formed the bulk of chl a biomass (69 ± 4%) and accounted for 49 ± 7% of total primary production in the SPG. In contrast, large phytoplankton (> 2 µm) accounted for a significantly larger fraction of the total primary production, despite having lower chl a biomass and P incorporation rates. Consequently, larger cells presented higher photosynthetic efficiency values than the smaller phytoplankton. The C:P incorporation rate ratios exhibited increasing deviation from the canonical stoichiometric ratios of 106 and 50 (for phytoplankton and heterotrophic bacteria, respectively) towards the centre of the SPG. We propose hypotheses to explain these deviations.

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Section: Role Of Microorganisms In the Carbon Budgetmentioning

confidence: 84%

“…In the oligotrophic area, nitrate concentrations were < 3 nmol l -1 while DIP concentrations were >120 nmol l -1 . Primary and bacterial productions were shown to be N-limited , Bonnet et al 2008.…”

Section: Methodsmentioning

confidence: 99%

Carbon and phosphate incorporation rates of microbial assemblages in contrasting environments in the Southeast Pacific

Duhamel¹,

Moutin²

2009

Mar. Ecol. Prog. Ser.

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“…The Equatorial Pacific Upwelling Region sampled here has been shown to have extremely low available iron (≤0.1 nM) and is thought to limit phytoplankton growth (40,41). Part of the Indian Ocean gyre may also be iron limited (42,43), although the BEC model suggests otherwise (22).…”

Section: Discussionmentioning

confidence: 98%

“…Iron addition experiments carried out in the Eastern Equatorial Pacific found that most phytoplankton, including marine Synechococcus, underwent rapid growth upon addition of iron (41,(45)(46)(47). The most striking exception was Prochlorococcus, which showed only a minimal response both in growth and fluorescence to iron enrichment.…”

Section: Discussionmentioning

confidence: 99%

Characterization ofProchlorococcusclades from iron-depleted oceanic regions

Rusch

Martiny

Dupont

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

161

190

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Prochlorococcus describes a diverse and abundant genus of marine photosynthetic microbes. It is primarily found in oligotrophic waters across the globe and plays a crucial role in energy and nutrient cycling in the ocean ecosystem. The abundance, global distribution, and availability of isolates make Prochlorococcus a model system for understanding marine microbial diversity and biogeochemical cycling. Analysis of 73 metagenomic samples from the Global Ocean Sampling expedition acquired in the Atlantic, Pacific, and Indian Oceans revealed the presence of two uncharacterized Prochlorococcus clades. A phylogenetic analysis using six different genetic markers places the clades close to known lineages adapted to high-light environments. The two uncharacterized clades consistently cooccur and dominate the surface waters of high-temperature, macronutrient-replete, and low-iron regions of the Eastern Equatorial Pacific upwelling and the tropical Indian Ocean. They are genetically distinct from each other and other high-light Prochlorococcus isolates and likely define a previously unrecognized ecotype. Our detailed genomic analysis indicates that these clades comprise organisms that are adapted to iron-depleted environments by reducing their iron quota through the loss of several iron-containing proteins that likely function as electron sinks in the photosynthetic pathway in other Prochlorococcus clades from high-light environments. The presence and inferred physiology of these clades may explain why Prochlorococcus populations from iron-depleted regions do not respond to iron fertilization experiments and further expand our understanding of how phytoplankton adapt to variations in nutrient availability in the ocean.

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“…It supports high N 2 fixation rates (235 µmol N m −2 d −1 ; Garcia et al, 2007), high Trichodesmium sp. (Dupouy et al, 2000;Le Borgne, 2008, 2010) and UCYN abundances (Biegala and Raimbault, 2008). This site therefore represented an ideal location to investigate the fate of DDN.…”

Section: Introductionmentioning

confidence: 99%

Biogeochemical fluxes and fate of diazotroph-derived nitrogen in the food web after a phosphate enrichment: modeling of the VAHINE mesocosms experiment

2016

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Abstract. The VAHINE mesocosm experiment in the oligotrophic waters of the Nouméa lagoon (New Caledonia), where high N 2 fixation rates and abundant diazotroph organisms were observed, aimed to assess the role of the nitrogen input through N 2 fixation in carbon production and export and to study the fate of diazotroph-derived nitrogen (DDN) throughout the planktonic food web. A 1-D vertical biogeochemical mechanistic model was used in addition to the in situ experiment to enrich our understanding of the dynamics of the planktonic ecosystem and the main biogeochemical carbon (C), nitrogen (N) and phosphate (P) fluxes. The mesocosms were intentionally enriched with ∼ 0.8 µmol L −1 of inorganic P to trigger the development of diazotrophs and amplify biogeochemical fluxes. Two simulations were run, one with and the other without the phosphate enrichment. In the P-enriched simulation, N 2 fixation, primary production (PP) and C export increased by 201, 208 and 87 %, respectively, consistent with the trends observed in the mesocosms (+124, +141 and +261 % for N 2 fixation, PP and C export, respectively). In total, 5-10 days were necessary to obtain an increase in primary and export productions after the dissolved inorganic phosphate (DIP) enrichment, thereby suggesting that classical methods (short-term microcosms experiments) used to quantify nutrient limitations of primary production may not be relevant. The model enabled us to monitor the fate of fixed N 2 by providing the proportion of DDN in each compartment (inorganic and organic) of the model over time. At the end of the simulation (25 days), 43 % of the DDN was found in the non-diazotroph organisms, 33 % in diazotrophs, 16 % in the dissolved organic nitrogen pool, 3 % in the particulate detrital organic pool and 5 % in traps, indicating that N 2 fixation was of benefit to non-diazotrophic organisms and contributed to C export.

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Nutrient limitation of primary productivity in the Southeast Pacific (BIOSOPE cruise)

Cited by 125 publications

References 51 publications

Carbon and phosphate incorporation rates of microbial assemblages in contrasting environments in the Southeast Pacific

Carbon and phosphate incorporation rates of microbial assemblages in contrasting environments in the Southeast Pacific

Characterization ofProchlorococcusclades from iron-depleted oceanic regions

Biogeochemical fluxes and fate of diazotroph-derived nitrogen in the food web after a phosphate enrichment: modeling of the VAHINE mesocosms experiment

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