Fig. 6: DDA Seasonality

: a This plot shows regions in nutrient space where either DDAs or Unicellular Diazotrophs should out-compete one another based on nutrient limited growth. Nitrate is .0025 μM but does not factor into the relative competition of modeled diazotrophs (κ = 0 for nitrogen). Black circles are monthly averages interpolated from the spline fits in Fig. 4. Phosphate errors are the standard error on the mean from the HOT data set (data can be found at http://hahana.soest.hawaii.edu/hot/hot-dogs/). Iron error bars are approximately the analytic errors for the measurement [58]. The observed statistical errors are larger than the seasonal cycle because the system is very under-sampled (see Fig. 4). The thick black line is where growth rates of model DDAs (diameter of 40 μm) and unicellular diazotrophs are equal. The gray region shows the sensitivity to ±2 μm in diameter for the model DDA. DDAs have a higher growth rate in the upper right region and unicellular diazotrophs have a higher growth rate in the lower left region. b This plot shows the percentage of the time our model predicts DDAs grow faster than unicellular diazotrophs in a given month out of approximately 20 sample years. The color bar represents the fraction of the time DDAs have a higher growth rate than unicellular diazotrophs in the simple model. This uses all available data. Notice the competitive advantage in December which occurs approximately half the time for DDA sizes near 20 microns