Fig. 3: The \({\mathbf{DON}}\text{--}{{\mathbf{NO}}}_{\mathbf{3}}^{\mathbf{-}}\) relationship and the sub-basin mean daily solar radiation and calculated phytoplankton growth rate.

a,b, The \({\rm{DON}}\text{--}{{\rm{NO}}}_{3}^{-}\) relationship in the carbonate-dominated (a) and the non-carbonate-dominated (b) regions. The solid lines indicate the linear regression fits, and the shaded areas are 95% confidence bands, the green and brown dots represent the data points in wet and dry seasons, respectively, and the dashed lines represent the 1:1 line of DON and NO₃⁻. c,d, The zonation of DON, solar radiation⁴⁸ and calculated growth rate in the wet (c) and dry (d) seasons, and the results of the Pearson correlation analysis are indicated by lines. In c and d, the green lines indicate the solar radiation (W m⁻²), the purple lines indicate the growth rate (d⁻¹), the coloured boxes indicate the 25–75% quartiles of the DON concentration using the overall data, the black dots indicate the means, the horizontal black line inside the boxes indicate the median values, the vertical lines above and below the boxes indicate the 1.5 interquartile range (IQR) and the purple and green dots indicate the data points.