Edvard and May-Britt Moser

(e.g. seaweeds, barnacles). This coating adds significantly to the drag of large ships and thus increases fuel consumption. The only chemical solution known to prevent this from happening is tributyl tin, which was banned in the late 1980s on environmental grounds. Jim Callow at the University of Birmingham is among the very small number of people investigating this phenomenon and looking for new solutions. “Our main test species is the green macroalga (seaweed) Ulva but we also use the unicellular diatom Navicula specifically because diatoms show opposite adhesion preferences,” Callow explains. “Ulva tends to adhere most strongly to hydrophilic coatings while diatoms such as Navicula adhere most strongly to hydrophobic coatings, especially those that are silicone-based. The frontiers of this subject lie in the development of the next generation of marine antifouling/ fouling-release coatings based on amphiphilic surface-active block copolymers coatings that are able to resist both types of algae.” A final application of diatoms brings us back to climate change — some species of diatoms are investigated with the aim of developing them for the industrial production of biofuels. This sounds surprising, as their most conspicuous attribute is their silica shell, which doesn’t help with the biofuel production and would have to be recycled. However, as Kröger explains, some species can survive without silicon. Phaeodactylum tricornutum, for instance, can switch between three different morphotypes in response to specific environmental conditions, and only one of the forms needs silicon (Protist (2011) 162, 462–481). “The idea is that if we remove certain nutrients like nitrogen or silicon from the medium, the diatoms accumulate lipids. The challenge is to find conditions where they do that and still grow to good yields,” Kröger explains. Here, as in the geochemical role of diatoms discussed above, progress is limited by the incomplete understanding of the molecular physiology of diatoms. More research into these intriguing organisms is definitely needed.