Estimation of sinking velocity using free-falling dynamically scaled models: Foraminifera as a test case

Area of Science:

• Paleontology
• Oceanography
• Fluid Dynamics
• Biophysics

Background:

• Settling velocity is crucial for understanding particle distribution in species with passive dispersal.
• Previous methods for studying fluid dynamics around objects involved flumes, wind tunnels, or towed models.
• Planktonic Foraminifera are vital for reconstructing Earth's past and present climate.

Purpose of the Study:

• To adapt dynamic scaling principles for determining the settling velocity of microscopic organisms.
• To develop a novel, non-invasive method for measuring the sinking speed of planktonic Foraminifera.
• To provide a new tool for studying the dispersal mechanisms of various settling particles.

Main Methods:

• Adapted dynamic scaling, an engineering technique, to study fluid dynamics.
• Utilized enlarged 3D printed models of Foraminifera tests.
• Sank models in viscous mineral oil, matching Reynolds numbers and drag coefficients to natural conditions.
• Predicted the sinking velocity of actual Foraminifera in seawater based on model experiments.

Main Results:

• Successfully predicted the sinking velocity of planktonic Foraminifera using free-falling models.
• Demonstrated the efficacy of dynamic scaling for determining settling velocities of biological particles.
• Established a novel methodology applicable to various settling particles.

Conclusions:

• Dynamic scaling offers a viable and innovative approach to measure the settling velocity of planktonic Foraminifera.
• This method enhances our understanding of Foraminifera distribution and their role in climate dynamics.
• The technique is adaptable for studying other microscopic settling particles like spores and seeds.