Projected area calculation for microalgae using three-dimensional models.

Area of Science:

• Aquatic Ecology
• Phycology
• Biophysics

Background:

• Microalgal light acquisition and sinking are critical for aquatic environments.
• These properties depend on projected area (Ā), a key morphological trait.
• Calculating Ā for concave microalgae has been a significant challenge.

Purpose of the Study:

• To develop a novel method for computing the projected area (Ā) of concave microalgae.
• To generate a comprehensive dataset of Ā values for numerous microalgal species.
• To investigate the relationship between Ā and other morphological metrics.

Main Methods:

• Utilized shape-realistic 3D microalgal models and a numerical approach with computer simulation.
• Calculated projected area (Ā) for over 800 microalgal species.
• Validated the method against convex shapes and the analytical Ā = surface area/4 formula.

Main Results:

• Developed a validated method with less than 5% estimation bias for projected area (Ā).
• Found that common morphological metrics cannot reliably predict species-specific Ā values.
• Demonstrated that morphological differences can cause up to 6-fold variations in Ā for the same volume.

Conclusions:

• Spindle-form, filamentous, and loosely packed coenobia maximize projected area (Ā).
• Provides an innovative methodology and a dataset of 844 planktic freshwater microalgae Ā values.
• The new metric, derived from Ā and cell counts, enhances understanding of phytoplankton shading and light availability.