A ship crosses the Paraná River on its way to the port of Rosario.
Credit: Marcela Valente/IPS
Asian Mussel Invasion Largely Ignored by Southern Cone Governments
By Marcela Valente
Some 3,000 species are transported around the world every day in the ballast water of ships. They may be viruses, bacteria, algae or invertebrates, but only a small percentage of them become invasive species.
BUENOS AIRES, Jul 9 (Tierramérica).- The governments of most of the countries that share the Río de la Plata basin are doing little or nothing to halt the golden mussel invasion, despite the serious damages and losses it is causing.
Limnoperna fortunei, an inedible freshwater bivalve mollusk, is native to the rivers and streams of China and Southeast Asia. From Asia, it travels around the world as a “hitchhiker” or “stowaway” on ocean-going cargo vessels. It first appeared in South America in 1991.
With no local predators, golden mussels quickly adapted to the Southern Cone region of South America, reproducing rapidly over the last 20 years and spreading from the Río de la Plata estuary to the Paraná and Uruguay Rivers and their various tributaries, all the way to the Brazilian city of São Paulo.
Biologist Gustavo Darrigran, director of the Invasive Mollusk Research Group at the School of Natural Sciences and Museum of the National University of La Plata, explained to Tierramérica why the golden mussel’s presence in the region is considered an “invasion”.
“An exotic species is one that is introduced to a new place, whether intentionally or not, and remains where it entered. An invasive species is one that becomes naturalized in its new environment and then quickly and rapidly spreads,” he said.
Darrigran, who recorded the appearance of the first specimens in 1991, stressed that the invasion “is causing impacts on both the natural environment and on humans.” Nevertheless, he added, the concern shown by the region’s governments over these impacts has been only partial.
The mussels attach themselves to any kind of hard surface, natural or artificial, and form colonies that block the pipes and filters of drinking water purification plants, industrial cooling systems, electric power plants and irrigation channels, as well as affecting navigation, tourism and fishing.
“They travel upstream around 240 km a year, an incredible speed considering that they live attached to any available hard surface,” said Darrigran.
Just three years after they were first observed in the region, golden mussels had clogged the water intake pipes of a drinking water treatment plant in Bernal, south of Buenos Aires, leading to the need for more frequent and costly cleaning, he said.
By the beginning of the new millennium, the fast-moving mollusks had already reached the Pantanal wetland spanning Bolivia and Brazil. They later wreaked havoc on the Argentine-Paraguayan Yacyretá hydroelectric dam and the Brazilian-Paraguayan Itaipú dam, both on the Paraná River. They have also taken up residence in the Salto Grande hydroelectric dam on the Uruguay River, shared by Argentina and Uruguay.
At the Yacyretá dam, where some 248,000 specimens per square meter were found, according to Darrigran, the dam’s chambers were lined with golden mussels, the filters in the pipes were obstructed, and some of the machinery stopped functioning due to overheating.
“They say that an unscheduled shutdown of one power-generating unit in a large-scale hydroelectric dam causes a loss of 450,000 dollars a day. It takes three days to clean out each unit. And there are 20 units in every dam,” he said.
But this proliferation seems to have had little impact on governments in the region. “Some countries are not doing anything. Others are doing something, with good intentions or to look good, but in both cases they are doing it either poorly or incompletely,” commented Darrigran.
To spur a response from the authorities, environmental lawyer Enrique Zárate, president of the Environmental Law Institute of the Bar Association of Rosario, a city in eastern Argentina, coordinated a research study on the impact of the golden mussel invasion and presented it in May to the National Ombudsman’s Office, calling for the adoption of measures.
The Ombudsman’s Office accepted the proposal and informed Zárate this month that it is investigating the matter. “They asked for reports from the Naval Prefecture and the Ministry of Environment (and Sustainable Development) and are going to study the economic damages caused,” Zárate told Tierramérica.
“It is very promising that economic studies are finally going to be undertaken, because this mussel has the capacity to shut down drinking water treatment plants, hydroelectric plants and factories,” he said.
Darrigran believes that to obtain results, it is important to raise the awareness of the public, “so that they will demand that the governments of the region take coordinated and sustainable action.”
He also recommended the promotion of research into measures for prevention and control, and the establishment of state institutions to take responsibility for these tasks, independently of changes in government.
At this point, eradicating this invasive species would be impossible, but it would be possible to coexist with it if measures of strict control are adopted to slow down its reproduction and spread.
“We want the state to recognize the problem, to react, and to implement strict control, because remediation is very difficult,” stressed Zárate.
According to the research group headed by Darrigran, some 3,000 species are transported around the world every day in the ballast water of ocean-going freighters, a phenomenon heightened by the globalization of trade.
These species may be viruses, bacteria, algae or invertebrates. Only a small percentage of them become invasive species, like the golden mussel.
These mussels have also altered the biodiversity of the region, displacing native species such Heleobia piscium and Gundlachia concentrica, two snail species that are now classified as “accidental”, meaning they are rarely found, said Darrigran.
Colonies of golden mussels attach themselves to the hulls of freighters and smaller vessels and even travel overland on trailer trucks to places far away from water, where specimens have also been found.
It is assumed that this is how they reached the large reservoir in Embalse, a town in the central Argentine province of Córdoba. The Embalse nuclear power plant is located on the shore of the reservoir, and the seriousness of the problem became clear when mussels blocked the reactor’s cooling system.