Researchers previously believed that a small, bushy seaweed in the Baltic Sea belonged to a species called narrow wrack. New research reveals they’re actually individuals within a giant seaweed clone—perhaps the largest clone known to science.
In a study published February 17 in the journal Molecular Ecology, University of Gothenburg researchers disproved the previous assumption that 310 miles (500 kilometers) of algae in the Baltic Sea were narrow wrack seaweed. Genetic analyses revealed that they are not only a different species—common bladderwrack—but also a giant clone, which has implications for the species’ resilience to threats like climate change.
A clone is a genetically identical copy of an organism, naturally resulting from asexual reproduction. In this case, the researchers discovered that fragments of an original female bladderwrack plant gave rise to new cloned populations across more than 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 comprises millions of individuals, 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,” Ricardo Pereyra, a marine scientist at the University of Gothenburg who led the study’s genetic analyses, said in a university statement. In fact, the bladderwrack clone might be the biggest known clone overall.
Bladderwrack forms large seaweed forests as far as 32 feet (10 meters) below the surface of the water. They shelter hosts of young fish, snails, and crustaceans, as well as larger fish, making them an important marine habitat. However, clones do not contribute to the genetic diversity that typically strengthens species against threats to their populations.
“The Baltic Sea is entering a period of warmer and probably even fresher seawater. In new conditions, all species must try to adapt in order 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 means that there are individuals in a population that can handle the changes and make the species survive.”
In other words, a genetically diverse population has a higher chance of overcoming a threat, such as disease, because it’s more likely that some members of that population may have 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 its research, the team also discovered another small and bushy seaweed species. It is closely related to bladderwrack—but clearly has an easier time enduring its other half, since it only reproduces sexually.
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