Researchers at ETH Zurich have discovered that phytoplankton, which carry out half of global photosynthesis, release substances in layered onion-skin patterns around each cell. This finding challenges previous models that assumed simple diffusion of organic matter into seawater. The study used Raman microspectroscopy to measure fucoxanthin concentrations and found that water-repellent substances stay concentrated near the cell, creating strong chemical signals that bacteria use to locate the algae. A mucus-like coating around the microalgae traps these molecules, sharpening the gradients. These layered phycospheres are critical marketplaces for organic carbon exchange between phytoplankton and bacteria. The research improves understanding of how carbon moves through ocean ecosystems, which has implications for global carbon cycle models. The study was published in Proceedings of the National Academy of Sciences and highlights the need for experimental data alongside computer modeling in marine biology.
