Environment, Headlines, Latin America & the Caribbean

ENVIRONMENT-MERCOSUR: United Against Mussel Plague

Mario Osava

RIO DE JANEIRO, May 4 2004 (IPS) - A lesson learned is worth more than a thousand warnings. After the invasion of the region’s rivers and waterways, Brazil and its trade partners in the Mercosur bloc have agreed to a joint plan for controlling bilge water, used in ships for stability when sailing without cargo.

The golden mussel poses a serious challenge to South America’s Southern Cone region. It is difficult to eradicate because it is a freshwater species and a newcomer to this part of the world, Brazilian researcher Evandro Colares told IPS.

The invasive mussel species, Limnosperna fortunei, comes from Asia, and probably arrived here in the bilge water of some ship. It was first recorded in the Rio de la Plata, the estuary between Argentina and Uruguay, in 1991.

Its proliferation has been dramatic, advancing northwards along the Rio de la Plata’s tributaries, it reached the Paraná River and extended to the Brazilian state of Sao Paulo.

The species spread "240 kilometres per year, against the current," indicating an intimidating capacity for reproduction, said Colares, head of research for the municipal water department of Porto Alegre, capital of the southern Brazilian state of Rio Grande do Sul.

The mussel’s main victim so far has been the big Yacyretá hydroelectric complex on the Argentine-Paraguayan border. Its pipelines and filters have been blocked by the accumulation of the golden mussels, requiring repairs and removal efforts – driving up electricity costs.

Concentrations of up to 180,000 mussels per cubic metre have been reported in Yacyretá, according to a report presented during a recent meeting in Brasilia, where representatives of the four countries of Mercosur (Southern Common Market – Argentina, Brazil, Paraguay and Uruguay) gathered to discuss the problem.

The invasion in Brazil is not yet that serious. The Itaipú hydroelectric dam, shared with Paraguay, has reported the presence of the mollusc since 2001, but it has not caused the harm recorded at Yacyretá, according to the Itaipú company’s environment department.

The problem is kept under control through the normal cleaning procedures, with a bit more attention paid the mussels. Itaipú Binacional is conducting a series of studies to determine the effectiveness of various chemical and filter treatments to deal with a potential increase in the mussel population in the future, say company spokespersons.

But the golden mussel is already creating headaches for sanitation companies. The water supply in Porto Alegre, for example, is suffering the effects of the species’ proliferation in Guaíba River, where it first appeared in 1998.

Since 2000, the drawing of water to supply the 1.5 million residents of the state capital has run into problems resulting from the mussels encrusted inside the pipes, said Colares.

To keep the system in working condition and to control the expansion of the mussel population, cleaning is done by hand, involving divers, and sometimes chemicals, such as copper sulphide in low concentration to remove the molluscs.

There is no danger of the mussels contaminating the water supply of consumers, because the water is treated with aluminium sulphate and chlorine, which the larvae of the mussel cannot survive, said the expert.

There are other methods to combat the mussel. The pipelines can be left to dry for a period of time. They can be treated with electric shocks. Chemicals can be used in the water uptake systems. But these approaches pose other difficulties, such as shutting off water supplies and the danger of chemical contamination, said Colares.

It is a relatively new problem and there is a lot of room for further research, he added.

Employing an electromagnetic field to the water system, as is done in undersea petroleum exploration and extraction, might also be useful against the mussels, but it is a technology developed for saltwater environments, and would need to be adapted to freshwater.

Eradicating the golden mussel is not an achievable goal – for now. The mollusc has found ideal conditions to go forth and multiply in the countries of Mercosur.

Among these conditions are climate, with a temperature that allows it to reproduce year round, which it cannot do in China, for example. And the water in this South American region contains a great deal of organic matter that serves as food for the mussel..

The absence of natural enemies also favours this exotic species. But in the Pantanal region of Brazil, a vast wetlands area along the Bolivian border, some types of fish have been found that feed on the golden mussel, Robson Calixto, marine contamination adviser to the Ministry of Environment, told IPS.

Brazil has launched an action plan against the golden mussel and is promoting a regional Mercosur plan to control ballast water and invasive marine species, following the guidelines set by the International Maritime Organisation and the International Maritime Convention adopted in February.

The aim is to prevent contamination from the bilge water that ships use for balance and stability when they are travelling without cargo. The water is discharged in the ports where the ships take on their cargo, and that is where the threat of introducing exotic species arises.

The four Mercosur countries will have to adapt their national legislation to better monitor the ballast water discharge processes.

In addition to the golden mussel, bilge water has brought to Argentina another mollusc of Asian origin, the Rapana venosa, but it flourishes in saltwater, said Calixto.

A study by the Brazilian navy of Sepetiba port, near Rio de Janeiro, identified 1,012 marine species, 12 of which were exotic – having found their way to Brazil from other countries, likely aboard a ship.