Iodide accumulation provides kelp with an inorganic antioxidant impacting atmospheric chemistry

Brown algae of the Laminariales (kelps) are the strongest accumulators of iodine among living organisms. They represent a major pump in the global biogeochemical cycle of iodine and, in particular, the major source of iodocarbons in the coastal atmosphere. Nevertheless, the chemical state and biological significance of accumulated iodine have remained unknown to this date. Using x-ray absorption spectroscopy, we show that the accumulated form is iodide, which readily scavenges a variety of reactive oxygen species (ROS). We propose here that its biological role is that of an inorganic antioxidant, the first to be described in a living system. Upon oxidative stress, iodide is effluxed. On the thallus surface and in the apoplast, iodide detoxifies both aqueous oxidants and ozone, the latter resulting in the release of high levels of molecular iodine and the consequent formation of hygroscopic iodine oxides leading to particles, which are precursors to cloud condensation nuclei. In a complementary set of experiments using a heterologous system, iodide was found to effectively scavenge ROS in human blood cells

Arbitrage in Energy Markets: Competing in the Incumbents Shadow

This paper studies the welfare implications of using market mechanisms to allocate transmission capacity in recently liberalized electricity markets. It questions whether access to this essential facility should be traded on a market, or whether the incumbent should retain exclusive usage rights. We show that granting exclusive use to the incumbent might be optimal, if the capacity of the essential facility is small and the incumbent can reduce production costs by taking advantage of interregional production-cost differences. This result counters the intuition that arbitrage will improve the social surplus when there is no output contraction. The reason is that when competition is imperfect, arbitrage might reduce production efficiency. We advise policymakers to introduce market mechanisms for the allocation of transmission capacity only if sufficient investment in the network is ensured or if the market power of the incumbent is broken in at least one of the markets in which it is active.