Margalef’s mandala, Prochlorococcus, and geoengineering Autors/ores Sallie W. Chisholm Dept. of Civil and Environ. Engineering Massachusetts Institute of Technology, Cambridge, MA, USA Resum Ocean phytoplankton played a central role in oxygenating our planet’s atmosphere billions of years ago. Hence these early “geoengineers” were crucial for the evolution of life on Earth. Their modern-day ancestor, the marine cyanobacterium Prochlorococcus, is the most abundant photosynthetic cell on the planet. Its discovery 30 years ago served as a reminder of how little we understand about the complexities of marine food webs. Yet proposals to fertilize the oceans, either to mitigate climate or enhance fi sheries, continue to gain momentum both within the scientific community and in the commercial sector. If implemented, the unintended consequences of these and other geoengineering proposals are likely to be enormous, and impossible to anticipate.Keywords: Prochlorococcus · geoengineering · climate change · iron fertilization Descàrregues PDF (English) Número Vol. 10 Núm. 1 (2014) Secció Distinguished lectures Llicència This work, including photographs and other illustrations, unless the contrary is indicated, is subject to an Attributions–Non-Commercial–No Derivative Works 3.0 Creative Commons License, the full text of which can be consulted at http://creativecommons.org/licenses/by-nc-sa/3.0/. You are free to share, copy, distribute and transmit the work provided that the author is credited and reuse of the material is restricted to non-commercial purposes only and that no derivative works are created from the original material.