Diatoms account for a large proportion of the phytoplankton found in the water, and live both in the open sea and in freshwater lakes. By reviving 100-year-old spores that had laid buried and inactive in bottom sediment, researchers at the University of Gothenburg, Sweden, have shown that diatoms are also genetically stable and survival artists.
Recent research has shown that diatoms exhibit great genetic differences and that they occur in discrete populations, which means that they multiply sexually to a greater extent than previously believed. What makes diatoms special is that if the environment they live in becomes too inhospitable they form resting spores, which gather in sediment at the bottom of the sea. When conditions improve, the spores can be revived.
The study concerned is based on a sample of sediment from a highly eutrophic Danish fjord on the east coast of Jutland, Mariager Fjord, whose anoxic bottoms and bottom sediments today do not show any signs of life. After dating the different layers of a sediment core, the researchers took small pieces of sediment from various depths and transferred them to an environment favourable to diatoms. This enabled them to revive resting spores.
"We revived hundreds of genetic individuals of diatoms and induced them to start dividing again and to form cloned cultures. The oldest are more than 100 years old, the youngest quite fresh. We then identified the revived individuals genetically," says Anna Godhe of the Department of Marine Ecology at the University of Gothenburg.