RS

The golden mussel, popularly known as Limnoperna fortunei, is invading the São Francisco River. Besides impacting native aquatic ecosystems, the species affects water capture systems, energy production, and fishing. This pest, if not combated, could still bring many problems to the São Francisco River basin. “The golden mussel is a small mollusk about two centimeters long. This invader is responsible for significant environmental impacts, such as the death of native fish and changes in the food chain and water quality,” explained Professor Newton Pimentel de Ulhôa Barbosa, from the Center for Bioengineering of Invasive Species at the Federal University of Minas Gerais (CBEIH/UFMG), who has been studying the effects of this invasion.

The mollusk was first detected in the São Francisco River in 2015, in the Sobradinho reservoir (PE). The advance of the golden mussel occupation since its first record has been extremely fast: in 2017, the city of Piaçabuçu had problems in its water supply system, from the Alagoas Sanitation Company (Casal), which was suspended due to the widespread obstruction caused by the golden mussels. Since then, the species has spread throughout the Lower São Francisco River.

Environmental and economic impacts occur mainly due to its high reproduction rates and competition for resources. “Moreover, it does not encounter predators, parasites, or even environmental variations capable of reducing its population growth in Brazilian waters,” said the professor. Therefore, this organism currently constitutes one of the most serious threats to the aquatic ecosystem of the São Francisco River.

The superpopulations of golden mussels (which can reach 200,000 per square meter), combined with the great capacity of these organisms to adhere to rigid surfaces of any nature, cause problems of obstruction of pipelines and increased corrosion of materials. The clogging of pipelines of equipment responsible for cooling turbines in a hydroelectric plant, for example, implies even the temporary shutdown of the system. These shutdowns cause enormous economic losses, mainly due to the loss of energy that the plant stops generating and the cost of the worker used to remove and dispose of these organisms.

In the São Francisco River basin, there are five hydroelectric plants (UHEs): Três Marias, Sobradinho, Itaparica, Paulo Afonso, and Xingó. “Studies show that the shutdown of a single 40 MW turbine for bioincrustation control can cost US$ 6.2 million per year in lost energy generation!” added Newton Pimentel.

The golden mussel and fishing

The golden mussel and fishing The presence of the golden mussel is especially worrying for producers of fish in net-pen systems, where commercially important species are confined within structures of nets or screens that allow water exchange with the environment. Golden mussels can adhere to nets and form colonies on screens, which impairs oxygenation and the elimination of fish waste and food remains. In extreme cases, there may be the sinking of the net pens caused by the weight of the colonies.

The high population density of these mussels also rapidly alters the presence and abundance of various native species. With fewer prey available, some fish feed on the mussels, but many of them are unable to digest the shells and die. Additionally, the golden mussel has the highest filtration rate (which represents the demand for food). Considering the population contingents, the invasion by the golden mussel demands a large volume of plankton for its feeding, impacting the entire food chain and potentially significantly reducing populations of fish and other organisms in the ecosystem that rely primarily on it as a food source. Preventive management and environmental education are the way to combat the golden mussel.

“The growing economic threat caused by species like this offers a strong economic incentive to invest in preventive management, such as biosafety and rapid response eradication. Another issue is to be aware of the degradation of the São Francisco basin and work on environmental education,” concluded the UFMG professor.

Hitchhiking on ships

the golden mussel is a freshwater bivalve mollusk (which has a shell with two closed pieces). Originally, its geographical distribution was limited to Southeast Asia, mainly the Yangtze River in China. In the 1960s, it was first found as an invasive species in Hong Kong, and in 1991, it was found in South America.

This introduction probably occurred through the water stored in the ships’ ballast water to give them stability. This practice introduces non-native species worldwide because only one cargo ship can transport millions of liters of water that cross states, countries, and continents.

These waters may contain organisms capable of surviving long-distance and long-duration trips and thus end up invading new environments as the water is released. Researchers believe that the process of moving fish from one river to another“stocking” - helped to displace the mollusk to the São Francisco River - the larvae, invisible to the naked eye, can be in the same water.

Webinar

Concerned about the invasion of the golden mussel, the São Francisco River Basin Committee (CBHSF) held a webinar on the topic. The goal was to show what an invasive species is, the issues of the golden mussel, and how to cope with this new challenge in the basin. The webinar was presented by UFMG professor Newton Ulhôa and moderated by CBHSF councilor, University of Sergipe (UFS) professor Carlos Garcia.

The invasive species golden mussel is known for its potential to cause obstruction of pipes and equipment in hydroelectric and water supply facilities.