Comment on Egusphere-2023-3110

Lipid remodeling, the modification of cell membrane chemistry via structural rearrangements within the lipid pool of an organism, is a common physiological response amongst all domains of life to alleviate environmental stress and maintain cellular homeostasis. Whereas culture experiments and environmental studies of phytoplankton have demonstrated the plasticity of lipids in response to specific abiotic stressors, few analyses have explored the impacts of multi-environmental stressors at the community-level scale. Here, we study changes in the pool of intact polar lipids (IPLs) of a phytoplanktonic community exposed to multi-environmental stressors during a ~2-month long mesocosm experiment deployed in the eastern tropical South Pacific off the coast of Callao, Perú. We investigate lipid remodeling of IPLs in response to changing nutrient stoichiometries, temperature, pH, and light availability in surface and subsurface water-masses with contrasting redox potentials, using multiple linear regressions, classification and regression trees, and Random Forest analyses. Notable responses include the proportional increases of certain glycolipids (namely mono- and di-galactosyldiacylglyercols; MG and CO2(aq) availability and high pH are associated with increased DG and sulfoquinovosyldiacylglycerol (SQ) concentrations. DG, respectively) associated with thermal stress as well as the degradation of these lipids under oxygen stress. Reduced Higher production of MG in surface waters corresponds well with their stablished photoprotective and antioxidant mechanisms in thylakoid membranes. Certain phosphatidylglycerol (PG) moieties show strong linear trends with light availability and are known to be important components in electron transport processes of photosystems I and II. IPL remodeling suggests the variable pH, hypoxia, and photoinhibition. These physiological responses reallocate resources from structural or recycling of acyl chains for energy storage in the form of triacylglycerols (TAGs) in response to stressors; like N limitation, extrachloroplastic membrane lipids (i.e., phospholipids and betaine lipids) under high-growth conditions, to thylakoid/plastid membrane lipids (i.e., glycolipids and certain PGs) and TAGs under growth-limiting conditions. Investigation of this lipid remodeling system is necessary to understand how membrane reorganization can affect the pools of cellular C, N, and S, and how it may influence fluxes of biologically relevant elements to higher trophic levels and to the dissolved organic matter pool.