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Nano‐ and picophytoplankton are a major component of open‐ocean ecosystems and one of the main plankton functional types in biogeochemical models, yet little is known about their trace metal contents. In cultures of the picoeukaryoteOstreococcus lucimarinus, iron limitation reduced iron quotas by 68%, a fraction of the plasticity known in diatoms. In contrast, a commonly co‐occurring cyanobacterium,Prochlorococcus, showed variable iron contents with iron availability in culture. Synchrotron X‐ray fluorescence was used to measure single‐cell metal (Mn, Fe, Co, Ni, Zn) quotas of autotrophic flagellates (1.4–16.8‐μm diameter) collected from four ocean regions. Iron quotas were tightly constrained and showed little response to iron availability, similar to culturedOstreococcus. Zinc quotas also did not vary with zinc availability but appeared to vary with phosphorus availability. These results suggest that macronutrient and metal availability may be equally important for controlling metal contents of small eukaryotic open‐ocean phytoplankton.

Recycling spent lithium‐ion batteries (LIBs) is an important consideration both to preserve metal resources and to reduce hazardous waste. One recycling method is to extract lithium and cobalt ions using organic solvents that contain battery components. However, it is hard to achieve the complete separation of metal ions and this also requires multiple steps. Herein, functionalized polymeric resins are reported, that can capture both lithium and cobalt ions from organic solutions and separate them chromatographically. Specifically, Merrifield resin is functionalized with oligoethylene glycol derivatives, which are structurally similar to crown‐ethers. To test the lithium‐ion depletion, these resins are incubated with bulk solutions of lithium cations at ≈50 ppm in acetonitrile. The results showed 30–45% depletion after filtration in optimal cases. To test this polymer support for chromatographic separation and check the potential for LIB recycling, a column is packed with the functionalized resin beads, and a mixture of lithium (≈200 ppm) and cobalt (≈200 ppm) ions is loaded. The column can achieve baseline separation of these ions and can be used multiple times without degradation. These results suggest that the current solvent extraction steps during recycling processes can be greatly simplified.