Millions of seaweed rafts sail through the ocean, transporting animals over distances of thousands of kilometers. This allows the seaweed and its passengers to settle in new regions, reports an international team led by scientist Ceridwen Fraser from the University of Otago in the journal Current Biology. For their study, the researchers modelled the drift of the seaweed and used DNA analysis to investigate the origin of seaweed, which had washed up on the coasts off New Zealand, Australia and Antarctica for decades. On the southeastern beaches of New Zealand they found seaweed powered by subantarctic islands in the southern Indian Ocean and in Tasmania seaweed from islands in the South Atlantic.
This is by no means about rare individual cases, the working group reports. Such trips are frequent and transport large amounts of biomass. The vegetable rafts are up to twelve meters long and are home to starfish, woodlice, crabs, crustaceans, arthropods, molluscs and worms, among others. As a result, they connect the ecosystems of all the coasts of the southern Hemisphere, which are often separated by entire oceans. The kelp can even overcome the barriers around Antarctica, which are actually difficult to overcome, which is separated from the rest of the oceans by strong circumpolar currents and oceanic fronts.
For the animal species involved, this remote transport is important protection against extinction through changing environmental conditions, for example through climate change. With increasing temperatures, the main habitat of marine species is expected to move further towards the poles. Thanks to the sea tang, species can follow climate change, even if their habitat is a small island in the middle of the ocean.
