Fatty acid composition, somatic growth and reproduction of <i>Acartia tonsa</i> across CO₂ treatment combinations.

<p><b>A</b>) Percentage of polyunsaturated (PUFA), monounsaturated (MUFA), and saturated (SFA) fatty acids relative to total fatty acids in female copepods. <b>B</b>) Principal component analysis (PCA) of fatty acid composition for the dietary algae <i>Thalassiorira pseudonana</i> and <i>A. tonsa</i> of the different treatment combinations. PCA scores 1 explained 40% of the variability (see <i>x</i>-axis of c) and was highly negatively correlated with 22:6<i>n</i>-3 (r² = 0.73), 20:4<i>n</i>-6+20:5<i>n</i>-3 (r² = 0.85), 18:3<i>n</i>-6 (r² = 0.73) and 16:1 (r² = 0.79), and positively with 22:1<i>n</i>-9 (r² = 0.25) and 18:1<i>n</i>-9<i>t</i> (r² = 0.57). PCA score 2 explained 17% of the overall variability (see <i>y</i>-axis of c) and was strongest positively correlated with 24:0 (r² = 0.84). Loadings of the PC scores are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0034737#pone.0034737.s002" target="_blank">Figure S2</a>). <b>C</b>) Stage distribution of <i>A. tonsa</i> individuals at day 10. C4, C5, C6 = copepodite stage 4, 5, and adult, respectively. <b>D</b>) Egg production rate (EPR) of incubated females (n = 12 per treatment level). EPR was significantly different between treatments (F_{(3, 44)} = 18.02, <i>p</i><0.001). Different letters above bars represent significant differences from a Tukey HSD test. The bars represent the 25^th, 50^th and 75^th percentiles, whiskers stand for the 10^th and the 90^th percentiles and black points show outliers. Legend refers to treatment combinations of copepod zooplankton (Z) and phytoplankton food source (P) at low (L) and high (H) <i>p</i>CO₂.