Prior to recent discoveries, scientists had assumed that a particular type of small, bushy seaweed in the Baltic Sea was a species known as narrow wrack. However, new findings have revealed that these seaweeds are actually part of a massive clone of a different species, potentially the largest known clone in science.

A study published on February 17 in the journal Molecular Ecology, conducted by researchers from the University of Gothenburg, has debunked the long-held assumption that 310 miles (500 kilometers) of algae in the Baltic Sea consisted of narrow wrack seaweed. Through genetic analysis, the researchers found that the seaweeds are not only a different species, known as common bladderwrack, but also a giant clone. This discovery has significant implications for the species’ ability to withstand threats such as climate change.

A clone refers to a genetically identical copy of an organism, resulting from asexual reproduction. In this case, the researchers discovered that fragments of an original female bladderwrack plant had given rise to new cloned populations spanning over 310 miles (500 kilometers) of the Bothnian Sea, a northern part of the Baltic Sea, by traveling on water currents. Normally, female bladderwrack seaweed plants reproduce through sexual fertilization with male bladderwrack seaweed plants.

“This clone is comprised of millions of individuals and, in some areas, is completely dominant, while in other areas, it coexists with sexually propagated individuals of bladderwrack. We have identified 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,” stated Ricardo Pereyra, a marine scientist at the University of Gothenburg who led the study’s genetic analyses, in a university statement. In fact, the bladderwrack clone may be the largest known clone overall.

Bladderwrack forms extensive seaweed forests as far as 32 feet (10 meters) below the surface of the water, providing shelter for hosts of young fish, snails, and crustaceans, as well as larger fish, making them a crucial marine habitat. However, clones do not contribute to the genetic diversity that typically enables species to withstand threats to their populations.

“The Baltic Sea is entering a period of warmer and likely fresher seawater. In these new conditions, all species must adapt to survive, including the important bladderwrack,” explained Kerstin Johannesson, a biologist at the University of Gothenburg and co-lead author of the study. “A clone almost completely lacks the genetic variation that otherwise allows individuals in a population to handle changes and ensure the species’ survival.”

In other words, a genetically diverse population has a higher chance of overcoming a threat, such as disease, because it is more likely that some members of that population may possess disease-resistant genes. Conversely, if all individuals share the same disease-prone genetics, the entire population could be wiped out. This principle applies to a wide range of threats, and it remains to be seen how the bladderwrack will handle climate change-driven threats.

During their research, the team also discovered another small and bushy seaweed species that is closely related to bladderwrack. However, this species has an easier time enduring its surroundings, as it only reproduces sexually.