Iodide from marine algae affects the coastal climate
Almost exactly 200 years after the discovery of iodine as a new element in the ash of marine algae, a study, also involving researchers from Constance, shows that marine seaweed releases huge quantities of iodine when exposed to stress. This process contributes to cloud formation and thus has an effect on the climate.
The international study brings together contributions from Great Britain, the USA, France, Switzerland, the European Molecular Biology Laboratory (EMBL), the Netherlands and Germany and has just been published in the renowned “Proceedings of the National Academy of Sciences” (PNAS).
Marine algae play a central role in the global iodine circle and the degradation of ozone on the sea surface. The large brown kelp of the genus Laminaria store large amounts of iodine, which is an essential element for human beings, contributing, for example, to the proper functioning of the thyroid. However, until now, the chemical form as well as the biological role of iodine in Laminaria remained an enigma. The new PNAS paper shows that Laminaria stores iodine as iodide which acts as inorganic antioxidant (i.e. detoxifies potentially toxic, reactive oxygen species), and is the first inorganic antioxidant described in a living system.
“When kelp is subject to stress, for example when exposed to intense light, desiccation or atmospheric ozone at low tides, the algae very quickly begin to release large quantities of iodide into the atmosphere,” explains lead author, Frithjof Küpper from the Scottish Association for Marine Science (SAMS) located in the Scottish city of Oban. The research on which the study is based, started in 2001 at the University of Constance where Küpper did his doctoral training with the Constance biologist Prof. Peter Kroneck, who, along with Eva-Maria Boneberg, Sonja Woitsch and Markus Weiller from Constance, is also a co-author of the paper. Küpper has been working for SAMS as lecturer and head of CCAP (Culture Collection of Algae and Protozoa) since 2003.
“These ions detoxify ozone and other oxidants that could otherwise damage kelp, and, in the process, produce molecular iodine that can actually be smelt. Our data provide a biological explanation as to why we are able to measure large amounts of iodine oxide in the atmosphere above kelp forests, producing condensation nuclei of water molecules and leading to cloud formation,” said Küpper. Kelp also releases large amounts of iodide into the sea after oxidant stress. This is a kind of inflammatory reaction and part of the kelp's defence response to attacks by pathogens.
Literature: Küpper FC, Carpenter LJ, McFiggans GB, Palmer CJ, Waite TJ, Boneberg E-M, Woitsch S, Weiller M, Abela R, Grolimund D, Potin P, Butler A, Luther III GW, Kroneck PMH, Meyer-Klaucke W, Feiters MC (2008): "Iodide accumulation provides kelp with an inorganic antioxidant impacting atmospheric chemistry". Proceedings of the National Academy of Sciences of the USA 105: 6954-6958
Source: University of Constance – 14th May 2008 (P)