Projected area calculation for microalgae using a three-dimensional model

This application allows users to explore a dataset of microalgae characteristics with computed parameters.

Authors

Borics Gábor¹, Verona Lerf^1,2, János Falucskai³, Viktória B-Béres¹, Tibor Kisantal¹, István Tóth¹, Enikő-T-Krasznai¹, Igor Stanković⁴, Judith Görgényi¹, Áron Lukács^1,5, Gábor Várbíró¹

Affiliations

¹ HUN-REN Centre for Ecological Research, Institute of Aquatic Ecology, Functional Algology Research Group, Debrecen, Hungary

² University of Debrecen, Juhász-Nagy Pál Doctoral School of Biology and Environmental Sciences, Hungary

³ University of Nyíregyháza, Institute of Mathematics and Informatics, Hungary

⁴ Josip Juraj Strossmayer Water Institute, Zagreb, Croatia

⁵ University of Helsinki, Lammi Biological Station, Finland

Corresponding author: Gábor Várbíró (varbirog@gmail.com)

Abstract

Light acquisition and sinking properties of microalgae fundamentally affect how species perform in aquatic environments. Both properties are the function of their projected area (Ā), a crucial morphological trait of microalgae. Despite their importance, species-specific Ā values have not been computed for microalgae. The reason for this is that although using an analytical approach Ā can be calculated for every convex shape, a vast majority of planktic algae are concave and currently not known how to calculate the projected area of concave shapes. Applying shape-realistic 3D models of microalgae and a novel numerical approach combined with computer simulation, we calculated the projected area for more than 800 microalgae. Validating this approach using convex shapes and the analytical Ā = surface area/4 formula we found, that the proposed method achieves less than 5% estimation bias. We also studied how Ā values of species can be predicted by easy-to-measure morphological metrics (such as Gald/width ratio, compactness, relative surface area extension, relative elongation, surface area constant, volume constant). We have found that the metrics do not show a sufficiently close relationship with the projected area to allow us to estimate species-specific Ā values. We demonstrated that the morphological differences among species can result in up to 6-fold differences in Ā values for the same volume. Spindle-form, filamentous species and loosely packed coenobia are the most efficient adaptations to maximize Ā. This study provides an innovative methodology and a huge dataset containing Ā values of 844 planktic freshwater microalgae. Although the dataset contains species only for the Pannonian and Dinaric ecoregions, because of the cosmopolitan nature of planktic algae it can be used for other ecoregions. Species-specific projected area values multiplied by cell counts give a new metric that characterizes the shading property of the given phytoplankton assemblage and enables us to better understand the changes in light availability and study the vertical processes in the water.

Highlights

• The application of Coachy’s formula for concave forms significantly overestimates their projected areas (Ā).
• A numerical approach and computer simulation can accurately estimate Ā for all microalgae.
• Models linking morphological metrics to projected area offer only rough approximations of Ā.
• Morphological variation can lead to up to sixfold differences in Ā for the same volume.
• Microalgae exhibit efficient morphological adaptations for light optimization.

Reference

Graphical example

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