Picophytoplankton abundance during dilution experiments in EL.

<p>Vertical profiles of <i>Prochlorococcus</i> (rectangles), <i>Synechococcus</i> (circles) and picoeukaryotes (triangles) mean abundances up to the DCM. Symbols also point out sampling depths. Horizontal bars represent ± S.D. The 10⁵ cells mL⁻¹ scale is for <i>Prochlorococcus</i>, whereas <i>Synechococcus</i> and picoekaryotes scale is 10³ cells mL⁻¹.</p

Phytoplankton integrated biomass in the water column during our experiments.

<p>Carbon based measurements were estimated using the C:Chl <i>a</i> ratios reported by Marañón et al. 2007 (see Methods). WL and EL refer to the West and East Lagrangian, respectively (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069159#pone-0069159-g001" target="_blank">Figure 1</a>). % Chl <i>a</i> <5: Contribution of phytoplankton Chl <i>a</i> biomass <5 µm to the total Chl <i>a</i> biomass. % C <5: Contribution of phytoplankton C biomass <5 µm to the total C biomass.</p

Estimated growth and grazing rates for small (<5 µm) and large (>5 µm) phytoplankton size fractions.

<p><i>µ_n</i>: phytoplankton growth rate estimated from treatments with added nutrients. <i>µ₀</i>: phytoplankton growth rate estimated from treatments with no nutrients added. <i>m</i>: microzooplankton grazing rate. <i>μ-m</i> balance: balance between <i>μ</i> and <i>m</i>. % pNPP: % Particulated net primary production grazed. SE: Standard error of regression parameters. **<i>r</i> significant at <i>p</i><0.01. *<i>r</i> significant at <i>p</i><0.05.</p

Estimated growth and grazing rates for <i>Prochlorococcus</i> in EL.

<p><i>µ_n</i>: <i>Prochlorococcus</i> growth rate estimated from treatments with added nutrients. <i>µ₀</i>: <i>Prochlorococcus</i> growth rate estimated from treatments with no nutrients added. <i>m</i>: microzooplankton grazing rate. pN<i>P</i>P: Particulate net <i>Prochlorococcus</i> production. <i>P</i>G: <i>Prochlorococcus</i> grazing losses. <i>μ-m</i> balance: balance between <i>μ</i> and <i>m.</i> % <i>P</i>P: % <i>Prochlorococcus</i> production grazed. SE: Standard error of regression parameters. *<i>r</i> significant at <i>p</i><0.05.</p

Vertical profiles of Chl <i>a</i> concentration up to the DCM during dilution experiments in WL and EL.

<p>Solid lines stand for total Chl <i>a</i> average values. Dashed lines indicate average Chl <i>a</i> <5 µm. Horizontal bars represent ± S.D. Numbers point out the percentage of Chl <i>a</i> <5 µm.</p

θ<i>-S</i> diagrams during dilution experiments.

<p>θ<i>-S</i> plots obtained from all the potential temperature (θ) and <i>S</i> measurements conducted in the upper 200 m during dilution experiments in WL (top) and EL (bottom). The color intensity of the dots indicates the depth associated to each θ<i>-S</i> pair. Black lines are isopycnals. Numbers above them point out sigma-theta values (σ_θ = potential density −1000 Kg m⁻³). Dotted lines are isotherms between which θ<i>-S</i> plots dispersion was higher.</p

Plots of dilution experiments based on Chl <i>a</i> measurements.

<p><b>Simple linear regressions between dilution factor and phytoplankton apparent growth rate for both phytoplankton size fractions and Lagrangians.</b> Quadratic fits are showed if they significantly (<i>p</i><0.05) improve the relationship. White dots indicate phytoplankton apparent growth rate in treatments with no nutrients added. Black dots point out phytoplankton apparent growth rates in treatments with nutrient added. Dashed lines indicate apparent growth rate = 0.</p

Plots of dilution experiments based on <i>Prochlorococcus</i> abundances.

<p><b>Simple linear regressions between dilution factor and </b><b><i>Prochlorococcus</i></b><b> apparent growth rate in EL.</b><b> </b> White dots: <i>Prochlorococcus</i> apparent growth rate in treatments without added nutrients. Black dots: <i>Prochlorococcus</i> apparent growth rates in nutrient added treatments. Dashed lines indicate apparent growth rate = 0.</p

Map showing the study area and the location of the surveys.

<p>Two Lagrangian surveys were conducted during the CARPOS cruise near the center of the subtropical gyre, <i>i.e.</i> the West Lagrangian (WL), and near the eastern boundary, <i>i.e.</i> the East Lagrangian (EL).</p

Vertical profiles summarizing the results of dilution experiments.

<p>Phytoplankton growth rates (black squares and lines), grazing rates (grey squares and lines) and <i>μ-m</i> balances (white squares and black dashed lines) of both phytoplankton size fractions and Lagrangians. Squares also point out the depths at which dilution experiments were performed. Grey dashed lines indicate the zero value.</p