Figure 5. The vertical distribution of buoyant microplastics (0.5–5 mm) in the ocean.

Grey circles show normalised mass (top panels) and numerical (bottom panels) microplastic concentrations. The exponential model is shown for three different parameterizations: (1) fitted parameters (black lines), (2) hydrodynamic parameterization with the average buoyant terminal rise velocity reported by Kukulka et al.¹¹ (orange lines) and (3) hydrodynamic parameterization with the weighted buoyant terminal rise velocity from the experiments of this study (blue lines). Mean parameter values (solid lines) with their uncertainty intervals (dotted lines) are indicated. Concentrations exceeding surface concentrations are not visualised in this figure, but are included in the statistical model.