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oa Sedimentary Partially Hydrogenated Carotenoids Suggest a Specific Environmental Resistance Strategy for Phytoplankton
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, IMOG 2025, Sep 2025, Volume 2025, p.1 - 2
Abstract
Water stratification increasingly threatens aquatic ecosystems by inducing deep water anoxia and promoting other unfavorable conditions for the survival of many organisms (reducing conditions and euxinia, etc.). Yet, the potential resistance and adaptive response of phytoplankton under such conditions, and their associated geochemical signatures, have been little explored. Lake Dziani Dzaha, a stratified thalassohaline lake, is an ideal model ecosystem for investigating such processes. In the water column, despite the absence of light and oxygen below 1 m depth and an euxinic bottom layer, viable cells are detected below the chemocline(s), which suggests a resistance strategy and the potential preservation of phytoplanktonic biomass in sediments. GC-MS analysis of preserved organic matter in core sediment samples revealed high concentrations of partially hydrogenated carotenoids. Their lack of structural diversity and their unique stereochemistry do not match with abiotic reduction processes and thus suppose a de novo biosynthetic pathway. The good correlation with quantitative profiles of phytoplanktonic biomarkers further confirmed this hypothesis. This study aims to demonstrate a new preservation pathway for organic matter through the production of specific carotenoid derivatives, more stable than their unsaturated precursors, by phytoplankton as a resistance strategy to survive constraining environmental conditions.
