Diatom research. Flasks containing cultures of diatoms in a temperature-controlled room. Diatoms are photosynthetic, single-celled algae that form an important part of the plankton at the base of the marine and freshwater food chains. In suitable conditions some species form huge blooms that are a valuable food source for aquatic animals and also important in removing carbon dioxide from the atmosphere. These cultures are being grown to study chemicals used for communication between diatoms. It is thought the chemicals can cause reproduction to be switched from asexual to sexual and bring about the death of the blooms. Photographed in the Department of Marine Science and technology, Newcastle University, UK.