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Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →Genetic analysis has identified a huge female clone of common bladderwrack (Fucus vesiculosus) along more than 500 kilometres (about 310 miles) of Sweden’s Bothnian Sea coast. The University of Gothenburg says it may be the world’s largest clone of any organism—but that remains a qualified possibility, not a confirmed global record.
What the “giant clone” actually is
The seaweed is common bladderwrack, Fucus vesiculosus, a habitat-forming brown alga native to the Baltic region. Researchers used genome-wide single-nucleotide-polymorphism data to show that much of the small, bushy form long treated as a separate species, Fucus radicans, is predominantly one female lineage of F. vesiculosus in the northern Baltic.
That means the visible plants are many physically separate individuals, but they descend vegetatively from the same female ancestor. “Clone” describes their genetic origin, not one continuous organism or an uninterrupted carpet of seaweed.
Where the clone is found
The University of Gothenburg’s 4 March 2025 announcement places the reported clone along more than 500 km (roughly 310 miles) of Bothnian Sea coastline, from Öregrund in Uppland to just south of Umeå. The distance is a geographic range between reported locations, not proof that one unbroken bed covers every kilometre.
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The clone dominates some areas and grows alongside sexually propagated bladderwrack in others. A separate University of Gothenburg management page uses a 550 km coastline figure, but the available sources do not explain whether that is a different measurement, an earlier description, or the same lineage under older terminology. The current announcement’s “more than 500 km” figure is therefore the safer description.
How bladderwrack reproduces in two different ways
| Feature | Clonal spread | Sexual reproduction |
|---|---|---|
| How new plants form | Fragments from a female plant drift with currents, settle and grow. | Separate male and female plants reproduce, creating offspring with newly combined genes. |
| Genetic pattern | Many individuals can share one lineage and have little variation within it. | Each generation can contain new genetic combinations. |
| What the survey found | The focal northern Baltic lineage is a very large female clone. | Sexually propagated bladderwrack occurs alongside the clone in some places. |
| What the measurement means | Individuals from the lineage occur across the reported coastal range. | It does not imply that the entire coast is covered by one genotype. |
Vegetative spread can be effective in the Baltic’s low-salinity water: a drifting piece can establish a new plant without finding a mate. Over time, currents and local growth can produce millions of individuals descended from the same female lineage.
Why bladderwrack matters to the Baltic ecosystem
Bladderwrack forms underwater forests that the university describes as reaching depths of about 10 metres in the Baltic context. These stands provide structure for fish fry, snails, crustaceans and larger fish, making the alga a foundation species rather than just another piece of shoreline vegetation.
The University of Gothenburg’s Ricardo Pereyra described the lineage as comprising millions of individuals. He said it is completely dominant in some areas but grows with sexually propagated bladderwrack elsewhere.
Could low genetic diversity make the clone vulnerable?
A large clone can be locally successful while still having fewer genetic options for future change. If most individuals share the same inherited traits, a new combination of warmer temperatures, lower salinity or disease may leave fewer plants able to tolerate the conditions.
Kerstin Johannesson, a University of Gothenburg professor of marine ecology and lead author, warned that the Baltic is entering a period of warmer and probably fresher seawater. She explained that a clone “almost completely lacks the genetic variation” that can leave some individuals able to handle environmental change.
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This is a vulnerability mechanism, not evidence that the Swedish clone has already collapsed or that a particular climate event has harmed it. The paper reports ecological-distribution models predicting a significant loss of Baltic F. vesiculosus under ocean warming unless populations can adapt; a model projection is not a certainty about what will happen to this lineage.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why the finding changes monitoring and management
Seaweed populations that look different may not represent separate species, while populations that look similar may contain very different genetic lineages. That genetic mosaic makes monitoring based only on visible form or conventional population assumptions unreliable.
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The University of Gothenburg’s management guidance emphasizes maintaining population size and connectivity and identifying and protecting populations that reproduce sexually. Those populations can preserve more genetic variation, providing raw material for adaptation alongside the extensive clonal stands.
- Protect sites where sexual reproduction is documented, not only sites with the largest visible beds.
- Maintain connections among coastal populations so fragments and sexually produced offspring can disperse.
- Use genetic data when distinguishing lineages or deciding which populations represent conservation priorities.
- Track environmental change without assuming that every plant in a large bed has the same adaptive capacity.
Is it really the world’s biggest clone?
It may be one of the largest reported clones, and the university uses the stronger wording “may be the world’s largest clone of any organism.” The available study and announcement do not provide an exhaustive, independently adjudicated comparison with every known clonal organism, so “world’s biggest” should remain qualified.
Nor do they establish the clone’s age, a precise census of its individuals, or continuous seabed coverage across the full range. The strongest supported claim is that genetic evidence identifies a predominantly female F. vesiculosus lineage extending across more than 500 km of the northern Bothnian Sea coast.
A separate Estonian seaweed should not be folded into the claim
During the broader survey, researchers also found a small, bushy, closely related seaweed on Estonia’s coast that reproduces sexually and was described as reproductively isolated from bladderwrack there. The release does not identify that Estonian seaweed as part of the Swedish female clone; it is a separate finding.
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The Molecular Ecology paper, published on 17 February 2025, analyzed genome-wide variation across the east Atlantic, a transition zone and the Baltic Sea. Its central taxonomic result is that the formerly described Fucus radicans is predominantly a large female clone of F. vesiculosus in its northern Baltic distribution. The University of Gothenburg announcement adds the coastal range, ecological context and conservation implications.
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