As the saying goes, he barely arrived and sat at the window. A species of mollusk, the golden mussel (Limnoperna fortunei), left its natural environment in Asia to swim in Brazil. Dominating important ecosystems, such as the Tocantins River, it has become one of the main invasive threats to Amazonian biodiversity.
The presence of the mollusk in the Tocantins River was first recorded in August 2023 in a municipality in the interior of the state of Pará. Since then, it has spread throughout Amazonian waters, perfectly adapted to the local habitat.
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Native to Southeast Asia, the mollusk has been present in Brazil since the 1990s and is believed to have arrived here aboard commercial ships. Since then, it has been a pest of Brazilian beaches and would have accelerated its domination by adapting to Amazonian rivers, according to a study published in September in Acta Limnologica Brasiliensia.
“This species causes serious socio-economic and environmental impacts. Mathematical models have indicated its invasion in the Amazon basin only from the 2030s, with consolidation in the 2050s. The fact that we have already found the species in the Tocantins River in 2023 highlights a much faster proliferation potential than previously imagined”, explains fisheries engineer Rafael Anaisce das Chagas, from the Federal University of Pará and main author of the article, in an interview with the Bori Agency.
Consolidated invasion in the Amazon
The research focused on analyzes of Pedral do Lourenço, a rock formation located between the municipalities of Marabá and Tucuruí, in Pará. Scientists collected molluscs attached to rock surfaces. The specimens analyzed had an average length of 12 millimeters and a population concentration of 11,940 individuals per square meter.
In some points, this number reaches 15,849 individuals per m². The previous survey, dating from 2023, indicated an average density of 88 individuals per square meter.
The study emphasizes that these results represent preliminary but revealing data. The population structure observed indicates a recent but already successful settlement and at least with its second generation underway. The species has high reproductive capacity and efficient settlement. Monitoring wider areas of the Tocantins River has therefore become urgent for researchers.
“The average population density indicates that the species has already adapted to the local environment and has probably reproduced at least once, given that we found individuals between 2 and 22 millimeters,” explains Chagas.
The golden mussel is native to Southeast Asia and has spread around the world, now making its way through the Amazon.
Environmental and economic impacts of the invader
The environmental effects of golden mussels are widely known in science. The mollusk releases a large volume of pseudofeces, modifying the environment and altering the quality of the aquatic habitat. The presence of molluscs also reduces benthic organisms (microscopic beings that serve as food). Competition for food therefore compromises local biodiversity.
“The presence of the golden mussel still generates several socio-economic impacts in the Amazon. We already have reports from fishermen who have lost their nets, from fish farmers who have recorded losses due to the accumulation of the mollusk in the structures of the reservoirs and the obstruction of the pipes due to an excess of individuals in the hydraulic compartments, increasing maintenance costs,” reports Chagas.
The eradication of golden mussels in the wild is considered unfeasible. Experts point out that control is often done through physical removal or the use of chemicals. “Even if it is not possible to eliminate the species from the environment, it is possible to control the impacts in systems constructed with adequate management,” concludes the researcher.
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