Measured settling velocities of in-situ particles over time from a ballasting experiment with and without added gypsum crystals during research expedition PS121. Gypsum crystals were added at 0 h for the ballasting treatments (red) while no gypsum was added in the control treatment (blue). Panel a compares particle settling velocities of a control treatment with particles ballasted with large gypsum crystals (>63 µm). Panel b compares particle settling velocities of a control treatment with particles ballasted with small gypsum crystals (≥30 to ≤63 µm). Settling velocities of the large-sized ballasting treatment (panel a) were significantly higher than the control treatment (ANOVA, P ≤ 0.05). Settling velocities of the small-sized ballasting treatment (panel b) were not elevated enough to show a significant increase over the control treatment (ANOVA, P ≥ 0.05).