Technicians consider it unlikely that it can be eradicated by ‘chemical warfare’
Declaring biological warfare on the zebra mussel appears to be the only way in Spain to end in open waters one of the most harmful invasive alien species in the world due to its environmental and economic impact, but its application requires more investment and research to adapt it to the country.
In the United States, they have been successfully applying a system for years developed by scientists at the New York Museum over a decade ago, based on the use of a genetically modified pseudomonas bacteria to generate a toxin that exclusively attacks the genus Dreissena.
So, its “release” in open water kills the specimens of this species without affecting the rest of the animals or plants with which it shares a habitat, the head of the Technical Service of the Júcar Hydrographic Confederation and an expert on this invader, Concha Durán, explained to Efe.
The problem is that this bacterium is introduced into the water in the form of dust and to kill the mussel in a reservoir, amounts of product would be needed that would generate levels of sediment that could terrify older reservoirs, making it unfeasible to apply it. in Spain, has regretted.
Present in eight of the 15 river basin districts of Spain
The zebra mussel, which causes serious environmental damage in the ecosystems in which it is implanted and in the infrastructures to which it adheres, forming large clusters, It is present in eight of the fifteen Spanish river basin districts and has colonized more than sixty reservoirs.
Specifically, it is in the Ebro (first demarcation in which it was found in Spain, in 2001), Guadalquivir, Andalusian Mediterranean Basins; Guadalete and Barbate; Red, Odiel and Stones; Júcar, River Basin District of Catalonia and Segura (last in which adult species appeared, in 2022).
Besides, its appearance in Portugal is newa country with which “we share two basins”, Durán recalled.
In Spain, for the moment, the Miño-Sil, Galicia Coast, Eastern Cantabrian, Western Cantabrian, Duero, Tajo, Guadiana demarcations are saved, that is, the “silicon” part of Spain.
In some of the latter, larvae have been found but never adult specimens, which indicates that they do not meet the conditions for the survival of the species, while in “calcareous” Spain it does settle due, surely, to the fact that for to form its shell requires calcium carbonate.
so it disperses
Among the major dispersal vectors of this species are fishing, navigation and transfers or transfers of water, added the expert, who explained that although there are already physical, chemical, biological or mechanical methods to prevent their entry and spread in closed facilities, they cannot be applied in open water because they would “kill” all living beings.
For example, water treatment plants usually hyperchlorinate at the beginning of treatment, while other facilities take advantage of the cold months to transfer water, since zebra mussel larvae need higher temperatures to survive.
According to the expert, there is only one case in the world in which the complete eradication of the zebra mussel in open waters has been achieved through “chemical warfare”.
“It was in Australia, in the bay of Darwin. After finding the zebra mussel, they declared a national catastrophe, closed it for 40 days and treated it with hypochlorite. Everything died”, stressed Durán, who pointed out that, later, the native species they recolonized, which was made possible by their openness to the ocean.
More than two reproductive cycles in Spain
“In the case of Spain, honestly, I don’t think it can be eradicated unless the biological route is developed”something that for the moment has been slowed down for “technical reasons” and due to a lack of research.
In the United States, the technique has been successfully tested in specific cases, mainly jetties, but the goal would be to be able to “clean” the reservoirs in their entirety.
“I trust science. Unless research advances in other lines, currently, the only option is biological warfare. It is the technique in which I have the most hope because it is what most closely resembles nature.”
Durán has also advocated learning more about how the zebra mussel lives here, because while in other places they have documented that it has two reproduction cycles, in Spain they are observing that it has more, probably due to the higher water temperatures.
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