Acknowledgments
We thank Laura Córdoba, Chiara Bordier, Raul Machado and Anja Wulf for
technical support in the lab, and Anika Lehmann, Marie Spohn and
Alexander Tischer for their valuable input for the development of the
experimental design. Philip Hoelzmann and Manuela Scholz helped with
elemental analyses. MCR acknowledges funding from an ERC Advanced Grant
(694368).