In the vast plume of the Amazon River, microscopic algae adopt a surprisingly flexible survival strategy: They combine photosynthesis with the uptake of organic matter. An international research team led by the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) has now shown that this so-called mixotrophy becomes the dominant and most successful lifestyle in mature plume waters. The findings, which are now published in Nature’s journal “Communications Biology”, reveal a previously underappreciated mechanism shaping marine food webs and carbon cycling in one of the ocean’s largest river-influenced systems.