Declaring biological methods against the zebra mussel might seem like a possible path forward. Spain faces one of the world’s most damaging invasive species in open waters, with clear environmental and economic consequences. yet, implementing such strategies requires more funding and research to adapt them safely within the country.
For years the United States has operated a system to manage this threat. Over a decade ago, scientists at a prominent museum explored approaches that could target the zebra mussel genus by altering certain bacterial pathways to produce toxins aimed at the Dreissena group.
This rationale suggests releasing a treatment into open water that would kill zebra mussels while leaving other organisms largely unharmed. An expert on invasive species, Concha Durán, leader of a regional hydrographic service, spoke about shared habitats and their implications for control strategies to a news agency.
The challenge remains that the proposed bacteria arrive as a powder and a substantial amount of product is needed to impact mussel populations in reservoirs. This raises concerns about sediment buildup and long-term reservoir health, a worry that Durán expressed for Spain.
Present distribution across Spain’s river basins
Zebra mussels cause major ecological disruption by forming large clusters on ecosystems and infrastructure. They are currently present in eight of Spain’s fifteen river basin districts and have established populations in more than sixty reservoirs.
In specific basins such as the Ebro, Guadalquivir, Andalusian Mediterranean Basins; Guadalete and Barbate; Red, Odiel and Stones; Júcar, Catalonia’s River Basin Region and Segura, adult specimens were observed at different times, with Segura noting the latest appearance in 2022.
There was also a look toward Portugal, where authorities noted that two basins were shared with neighboring regions.
Spain’s eastern and western Cantabrian basins, along with Miño-Sil and the Galician coast, have shown persistence of larvae in some cases, while adult populations remain limited. In calcareous regions, where calcium carbonate supports shell formation, the species appears more stable.
Why the species spreads
Key spread channels include angling, boating, and the transfer of water or equipment. While there are physical, chemical, biological or mechanical means to limit introduction and spread within closed facilities, these options would harm other life if used in open waters. As a result, the focus remains on targeted strategies and containment.
Some water treatment plants use initial high levels of disinfectants at the start of treatment, while others schedule water transfers during cooler months, since larval mussels often require warmer conditions to survive.
An expert notes that there is one documented case worldwide where open-water eradication relied on chemical methods: Darwin Bay, Australia. After identifying a zebra mussel outbreak, authorities declared a disaster, halted activities for several days, and applied a strong chemical treatment. The population declined, but recolonization occurred once open-ocean access returned.
Multiple breeding cycles in Spain
The specialist believes that eradicating the mussel in Spain may require deploying a biological strategy alongside other measures, noting that progress has been slowed by technical barriers and a need for deeper research.
In the United States, certain techniques have undergone testing in places like breakwaters, with the overarching aim of eventually clearing reservoirs entirely.
The expert emphasizes faith in science, suggesting that ongoing research might broaden options beyond current approaches and that progress depends on understanding how the zebra mussel lives in local waters, including noticing more breeding cycles in Spain potentially due to warmer temperatures.
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Contact information for the environmental department is not included here.