Researchers have found what they think may be the largest clone in the world hiding in the Baltic Sea: common bladderwrack.
For years, scientists believed that a small, bushy form of seaweed in the Baltic, known as narrow wrack, was a separate species. However, through DNA sequencing, they have now discovered that this distinctive form is actually a giant clone of bladderwrack.
The clone has spread along the coast of the Bothnian Sea – the northernmost arm of the Baltic Sea – stretching over 300 miles (more than 500 kilometres) from the town of Öregrund to the city of Umeå (both in Sweden). For context, it would take a person walking non-stop at an average speed of two miles an hour more than six days to cover this distance.
What is a clone?
A clone occurs when an organism or cell is naturally replicated. The most obvious example of this is identical twins, where two offspring are produced from a single fertilised egg that splits. Clones occur throughout the natural world, from animals to plants – and seaweeds.
How did the bladderwrack clone get so big?
Bladderwrack typically reproduces through sexual fertilisation, with separate male and female wracks. But in this case, the female bladderwrack has been cloning itself. Fragments of the original organism break off and drift with the water currents, growing into new fronds.
This process has led to the creation of a vast, genetically identical population of bladderwrack that dominates certain areas of the Baltic Sea, explains Ricardo Pereyra, a researcher and lead author of the study, published recently in the journal Molecular Ecology.
“This clone comprises millions of individuals,” says Pereyra, “and in some areas, it is completely dominant, while in other areas it grows alongside sexually propagated individuals of bladderwrack.
"We have found a few more large clones in the Baltic Sea, but the female clone off the Swedish Gulf of Bothnia is by far the largest clone – a real super female.”
Why is bladderwrack important?
Bladderwrack, a key species in the Baltic Sea, thrives in the brackish waters, which have low salinity.
It grows in dense, underwater forests, creating vital habitats for a variety of marine creatures, from small fish to large mammals. These underwater forests are essential for maintaining a healthy marine ecosystem.
What will happen to the giant clone?
While these clones have proven to be incredibly successful, there are concerns about their long-term survival. Without the genetic diversity that comes from sexual reproduction, clones are more vulnerable to environmental changes. The warming waters of the Baltic Sea, along with other climate-related shifts, could make it harder for these clones to adapt and survive.
“A clone almost completely lacks the genetic variation that otherwise means that there are individuals in a population that can handle the changes and make the species survive,” explains Kerstin Johannesson, a marine ecologist at the University of Gothenburg.
As the Baltic Sea continues to warm, the future of this giant clone – and other seaweed species like it – remains uncertain, the authors conclude.
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