Mean nitrogen and carbon isotopic signature in MICRO, MESO and BFTL.

<p>δ¹⁵N (A) and δ¹³C (B) isotopic signature (Mean±SE) for different planktonic compartments analyzed (microzooplankton [MICRO,55−200 μm], mesozooplankton [MESO, >200 μm] and bluefin tuna larvae [BFTL]) in Eastern Gulf of Mexico (E-GOM) (●), Western Gulf of Mexico (W-GOM) (●) and Balearic Sea (MED) (○) regions. Regions (E-GOM, W-GOM and MED) and plankton size fraction (MICRO, MESO and BFTL) were the main factors for the 2-way ANOVA analysis. Post-hoc comparisons were made using a Tukey’s test. Different letters indicate significant differences (<i>p</i>< 0.05) among plankton size fractions within same region. * denotes a significant difference (<i>p</i>< 0.05) between regions for the same plankton size fraction.</p

Biplot of mean nitrogen and carbon stable isotopes in bluefin tuna larvae.

<p>Mean (±SE) δ¹³C versus δ¹⁵N (‰) values mesozooplankton (MESO-triangles) and bluefin tuna larvae (BFTL-circles) in Eastern Gulf of Mexico (E-GOM) (●), Western Gulf of Mexico (W-GOM) (●) and Balearic Sea (MED) (○) regions. Microzooplankton as primary consumers has been used as baseline. The ellipses represent the isotopic variance for each region, encircling the isotopic signature for the different plankton size fractions (MICRO, MESO and BFTL).</p

Bluefin tuna larval size frequency distributions.

<p>Eastern Gulf of Mexico (E-GOM), Western Gulf of Mexico (W-GOM) and Balearic Sea (MED) bluefin tuna larval size frequency distributions analyzed for trophic ecology studies.</p

Location of the study areas.

<p>(A) Gulf of Mexico (GOM) and Balearic Sea (MED). (B) Eastern (E-GOM) and Western (W-GOM) and (C) MED bluefin tuna study area showing the oceanographic-planktonic stations sampling distribution. Bathymetric image generated from ETOPO1 database [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133406#pone.0133406.ref051" target="_blank">51</a>].</p

Nitrogen and carbon stable isotopes <i>vs</i> bluefin tuna larvae size relationship.

<p>Different δ¹⁵N (A) and δ¹³C (B) isotopic signature <i>vs</i> standard length (SL) relationships of bluefin tuna larvae in Eastern Gulf of Mexico (E-GOM) (●), Western Gulf of Mexico (W-GOM) (●) and Balearic Sea (MED) (○) regions.</p

Biomass of zooplankton size fractions.

<p>One-way ANOVA analyses of both (A) microzooplankton [MICRO,55−200 μm]- and (B) mesozooplankton [MESO, >200 μm] size fraction biomass (mg·m^-3) in Eastern Gulf of Mexico (E-GOM) (●), Western Gulf of Mexico (W-GOM) (●) and Balearic Sea (MED) (○) regions. Post-hoc comparisons were made using a Tukey’s test. Different letters indicate a significant difference between ecosystems. Box represents std error and whisker Std dev respectively.</p

Basic hydrographic data of the study area.

<p>Temperature (°C) and salinity (‰)of the selected stations from the Eastern Gulf of Mexico (E-GOM) Western Gulf of Mexico (W-GOM) and Balearic Sea (MED) sampling regions.</p><p>Basic hydrographic data of the study area.</p