Journal Articles Geochemical Perspectives Letters Year : 2025

Origins of the pervasive luminescence in modern stromatolites

Abstract

Stromatolites are emblematic geobiological objects in the search for signatures of life. Their biogenicity has usually been assessed based on their macroscopic morphology, texture and/or the presence of microfossils. Surprisingly, ancient stromatolites, as well as the lithified portion of modern stromatolites, contain limited amounts of organics, although they are originally formed by biofilms. This raises intriguing questions about the fate of organics during lithification of microbial communities. Here, we analysed modern stromatolites from a coastal pond in Western Sardinia with confocal laser scanning microscopy (CLSM). We evidenced pervasive fluorescence in stromatolites and distinct spectral signals tentatively attributed to preserved chlorophyll/phycocyanin pigments, providing a direct link to the photosynthetic activities of microbial communities. Additionally, some signals were indicative of various stages of chlorophyll/phycocyanin degradation, producing a non-specific green autofluorescence (GAF), with a degradation advance varying with laminations. This calls for a wider application of CLSM to track this pervasive carbon reservoir in ageing stromatolites and possibly find an additional indication of their biological origin.

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hal-05143965 , version 1 (04-12-2025)

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Juliette Debrie, Jean-Paul Saint Martin, Dimitri Prêt, France Lam, Kadda Medjoubi, et al.. Origins of the pervasive luminescence in modern stromatolites. Geochemical Perspectives Letters, 2025, 35, pp.18-23. ⟨10.7185/geochemlet.2518⟩. ⟨hal-05143965⟩
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