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Why scientists are fighting to keep golden mussels out of Amazon waters

The invasive mollusk species has colonized in various river basins throughout South America, and scientists are fearful the golden mussel will soon reach the Amazon.

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    Biologist Marcela Uliano da Silva examines golden mussels which have latched onto tires in the Jacuí River, Rio Grande do Sul State, in Brazil.
    Rogério da Silva/Marcela Uliano da Silva
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Scientists dubbed the golden mussel an “ecosystem engineer,” not for its ability to build new ecosystems, but its efficiency in changing them. And not necessarily for anyone else's benefit.

Now the golden mussel has been discovered in five South American countries, including Brazil, and biologists are concerned the species could do damage to the Amazon River. But one young scientist is trying to find a solution before that can happen.

The golden mussel, native to China, spread to Taiwan and Japan in the second half of the 20th century. The bivalve made its first appearances in South America in the 1990s, after ships traveling to the continent incidentally carried the mussels on their ballasts. From the La Plata River in Argentina, the species moved northward and entered the Uruguay, Paraguay, and Tiete rivers.

Biologist Marcela Uliano da Silva, a PhD candidate at the Universidade Federal do Rio de Janeiro, has been studying the mussel species for more than four years. Uliano da Silva has seen the effects of the invasive mollusk firsthand.

“One of its characteristics is that it reproduces a lot, creating huge populations,” Uliano da Silva told the Monitor.

And because the species is a filter feeder – it strains food particles and other matter from the water – more mussels means the more transparent the water becomes. From there, sunlight can reach lower depths and alter aspects of the ecosystem, like phytoplankton levels. At first, the impact of the mussel’s presence may not appear so bad.

“In some rivers, there is evidence showing that the fish population has increased 20% because they have a new food resource in the mussels. But when you increase the number of fish, it has a domino effect,” wrote Uliano da Silva. “Ultimately, when the mussel invades, it transforms the ecosystem, decreasing biodiversity and homogenizing the environment.”

Uliano da Silva is trying to sequence the golden mussel’s genome in an effort to come up with a way to control the species. The researchers have found that the mussel can exist in a variety of habitats across South America, unlike in its native region, where the species can survive only in a narrow range of temperature and acidity. So Uliando da Silva and her colleagues propose that the mussel’s "robust" genetic makeup allows it to express a wide range of traits to help it thrive in South American waters.

One possible strategy once Uliano da Silva’s team has pinned down the genome involves injecting the mussels with molecules that silence target survival genes. When the mussels are released into waters, they are unable to breed successfully and population numbers are kept in check. Scientists studying the Aedes aegypti mosquito have offered a similar technique to control dengue fever, which is believed to be transmitted by the mosquitoes, in Asia and Latin America.

While Uliando da Silva works on a way to keep the mussel at bay, the situation provides a perfect example of how some species are kept in balance in certain ecosystems, but can become a major threat in others.

“In China the golden mussel has predators and competitors, which keeps it under control,” wrote Uliando da Silva. “South America has proven to be a perfect scenario for the golden mussel to spread: less competitors and plenty of food.”

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