Dresden 2026 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 1: Active Matter I (joint session BP/CPP/DY)

CPP 1.11: Talk

Monday, March 9, 2026, 12:30–12:45, BAR/SCHÖ

Circadian gravitaxis: Photosynthetic microswimmers remodel local pH to actively tune vertical migration — Arkajyoti Ghoshal¹, Soumitree Mishra¹, Jayabrata Dhar², Hans-Peter Grossart^3,4, and •Anupam Sengupta^1,5 — ¹Physics of Living Matter, Department of Physics and Materials Science, University of Luxembourg, Luxembourg — ²Department of Mechanical Engineering, National Institute of Technology Durgapur, India — ³Department of Plankton and Microbial Ecology, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Stechlin, Germany — ⁴Institute of Biochemistry and Biology, Potsdam University, Germany — ⁵Institute for Advanced Studies, University of Luxembourg, Luxembourg

Motile phytoplankton shuttle between bright surface waters and deeper nutrient rich layers, usually controlled by internal circadian clocks. Yet many species show irregular movements, defying the expected circadian rhythm. Studying a bloom forming photosynthetic species, we found that cells adjust their vertical migration by altering local pH, mediated by a shift in their gravitactic behavior. This self-modulation of pH generates sub-populations which are physiologically similar but swim differently, remaining vertically separated even under uniform conditions. Supported by a cell-level analysis and mathematical model, we confirm that the pH-mediated circadian shift is underpinned by morphological adjustments. Our results support a circadian gravitactic model in which diurnal pH control drives diversified migration, enhancing fitness particularly in acidifying oceans.

Keywords: active swimmers; gravitaxis; circadian; morphology; physiology