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Brazilian Journal of Biology

Print version ISSN 1519-6984

Braz. J. Biol. vol.72 no.1 São Carlos Feb. 2012

 

Do toxic cyanobacteria affect feeding and survival of the invasive bivalve golden mussel?

 

 

Researchers from Federal University of Rio Grande do Sul and Federal University of Rio de Janeiro analyzed the effects of toxic cyanobacteria Microcystis aeruginosa on feeding and survival of the invasive bivalve golden mussel Limnoperna fortunei according to the paper published in Brazilian Journal of Biology Volume 72(1) and revealed the mussel was able to feed and survive in the presence of toxic cyanobacteria. This fact shows the potential of this invasive bivalve as a vector to the transference of cyanotoxins to higher trophic levels, which means that toxins can accumulate in organisms that feed on mussels, mainly freshwater fishes, enhancing the risk of contamination.

Mussels used in the experiments were collected from the natural environment (Guaíba Lake, Southern Brazil). A short and a long-term grazing experiment were conducted at the laboratory. In the short-term experiment, golden mussel filtration rates were evaluated in the presence of toxic and non-toxic strains of cyanobacteria and non-toxic phytoplankton. According to the research, cyanobacteria toxicity is not the main factor influencing golden mussel feeding behavior. Mussels fed at highest rates on non-toxic phytoplankton. However, golden mussel preferentially ingested cyanobacteria cells, both toxic and non-toxic, and expelled non-toxic phytoplankton in large quantities. In the long-term experiment, mussels were exposed to toxic and non-toxic strains of cyanobacteria during 5 days. Filtration rates were not significantly different for toxic and non-toxic cyanobacteria throughout exposure period, indicating cyanotoxins do not affect feeding and survival of golden mussel.

The presence of golden mussel might promote a decrease of cyanobacteria cells, and an increase of diatoms. On the other hand, the efficiency of golden mussel in removing cyanobacteria cells could be reduced in the presence of cyanobacteria blooms. These blooms are usually formed by large colonies and filaments of cyanobacteria that would probably be rejected by golden mussel.

Cyanobacteria dominance is a global problem, especially in freshwater ecosystems, because of bloom formation and toxin production. Poisoning and even death of wild animals, domestic animals, and humans may be linked to cyanobacteria toxicity. The knowledgment about golden mussel impacts on cyanobacteria and food chain is scarce. Since its invasion in South America in 1991, golden mussel has been proliferating and dominating aquatic ecosystems such as rivers, lakes, and reservoirs. These facts indicate the importance of studying the role of this invasive species in food chain of invaded ecosystems due to its powerful filtering capacity and its ability to quickly proliferate and turn into massive populations.

This study is part of the Vanessa Gazulha's Doctorate Dissertation developed at the Federal University of Rio Grande do Sul, which focus on the assessment of feeding impacts of golden mussel on plankton communities, especially toxic cyanobacteria, and their consequences to aquatic trophic chain. The financial support is from the National Council for Scientific and Technological Development (CNPq).

 

 

Dra. Vanessa Gazulha
vanessagazulha@gmail.com
Federal University of Rio Grande do Sul, Brazil

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