Collaboration with La Maison de la Rivière
La Maison de la Rivière (literally: River’s House) is a foundation located in Tolochenaz, next to the Geneva lake and the Boiron river. This foundation aims to protect Swiss aquatic species and perform the research for their conservation, but also facilitates a place where academics, citizens and children can meet and exchange information and opinions about the aquatic biodiversity. You can learn more on the webpage: https://www.maisondelariviere.ch/
As quagga mussels cause many damages to the aquatic environment, we contacted La Maison de la Rivière to present our project and discuss the subject with environmental professionals and scientists. On the 26th of July, we met La Maison de la Rivière co-director, Damien Robert-Charrue. He showed us the museum, the aquariums and explained to us the various studies that were taking place on quagga mussels. Mr. Robert-Charrue felt very concerned about this invasive species and gave us an example why. He told us that in 2018 a new canalisation that pumps the lake water for some of their infrastructures had been installed. The strainer arrived up to 25 m in depth, which was enough to avoid an invasion by the zebra mussels. Unfortunately, the quagga mussels started to be more and more numerous in Lake Geneva. As a consequence, this canalisation, typically operational for 50 years, lost functionality within 2 years. In 2020, the foundation sent divers to clean the strainer but only a week later it was completely blocked by quagga shells again. Since sending divers on a weekly basis is not a viable solution, they gave up and the pump is currently on standby.
The cost of a canalisation is, according to the co-director, around 500 - 1’000 Swiss francs per meter (= 500 - 1000$ per meter). During our interview, he has shared his concern with us and has admitted that engineers probably need to rethink the pumping system because of the quagga presence. Since quagga mussels can live up to 130 meters of depth in the lake, placing the strainer deeper is not a feasible solution (Mills et al., 1993).
Considering the situation, any ideas, however small they are, could get us a step closer to the final solution that we are looking for. Mr. Robert-Charrue suggested testing a few things:
- New materials for canalisation. Nowadays, these infrastructures are more often covered with PVC or PE, which are one of the favourite attachment materials for the quagga mussels.
- New strainer morphologies. A strainer is a piece placed at the beginning of the canalisation and serves to collect the water and to take out the big particles that could block the filter. For example, a rotating strainer would prevent quaggas’ entry and attachment, while a removable strainer would facilitate substitution and cleaning (since it could be cleaned outside the water).
This second idea joined our perspective to fabric a waterproof paint-like solution containing our Zosteric Acid. The waterproof property should prevent the need for frequent renewal of the protective coating. As we didn’t imagine that creating a removable strainer was an actual research, we were wondering how we could apply our paint in the canalisations that are already immersed by water. With a removable strainer, we could easily paint its surface before we replaced the one underwater. The one replaced would clean outside water, which would take less time than if the cleaning were done in the water. We also thought of using this paint for the protection of hulls, which are another favorable attachment surface for mussels, most likely involved in the spread of the invasive species from lake to lake.
As we thought to include our genetically modified Pseudomonas protegens and Escherishia coli in the canalisation, the co-director pointed out that current regulations in Switzerland do not allow the release of GMOs in nature. Also, we realized that releasing transformed bacteria could be dangerous for other species, if we couldn’t exclude the idea of eventual dispersion out of the canalisations. Therefore, in order to apply our product with the purpose to protect both the canalisations and the environment, we have to figure out a solution to release only the components that are active against mussels: the FitD toxin, and Zosteric Acid. To do so, we thought to add a step of cellular lysis, to kill all viable cells and release their content. In addition, we reached out to biologists to find the most appropriate way to separate our products from the rest of the cell content, so we will not release unnecessary compounds in the environment. For the FitD toxin application, we would use it with the aim to treat plug canalisations, as the zosteric acid would prevent their attachment to the strainer and their entry in the canalisation. As La Maison de la Rivière told us, they installed two kinds of canalisation systems, one for the infrastructures that require drinkable water and another one for all the infrastructures that don’t need drinkable water, such as bathrooms and heating. We thought to treat, as a first step, only the non-drinkable canalisation system with our FitD toxins. It would be a temporary cleaning, done only when required.
La Maison de la Rivière gave us some precious articles written by bachelor and master students. Some of them detailed their life cycle and explained that the quagga mussels are more tolerant to cold water than the zebra mussels and their reproduction was observed in 4,8°C water (which isn’t the case for the zebra mussels)(Beisel et al., 2003 & Roe, 1997). Moreover, some studies showed that once attached, quagga mussels grow up quickly and arrive at maturity before their cousins. This explained to us why quagga mussels dethroned the zebra mussels that came first in our Swiss lakes: they are better filters, cold water resistant, can reproduce despite low temperature and they reach maturity sooner. But for this last point, this requires first their attachment: a fixed quagga mussels invests less energy against water current and saves energy that permits it to reach maturity and its reproductive capacity earlier than one constantly fighting against the current.
The meeting with Mr. Robert-Charrue and this article showed us the major opportunity for the use of zosteric acid: not only will it decrease the costs for cleaning the pipes and boats, but it will reduce their reproductive capacity as they need to be attached to grow up and become healthy adults.
Note: During the mussel collection, we saw that many small shrimps lived hidden under the shells. We discussed it with the co-director and he told us that these shrimps are the Hemimysis anomala, an invasive species that profit from the presence of quagga mussels to have a habitat.
References
- Mills, E.L., Dermott, R.M., Roseman, E.F. (1993). Colonization, Ecology, and Population Structure of the "Quagga'' Mussel (Bivalvia: Dreissenidae) in the Lower Great Lakes. Canadian Journal of Fisheries and Aquatic Sciences https://doi.org/10.1139/f93-255
- Beisel, J-N., Soulignac, F. Literature review: biology, ecology, and potential impacts of Dreissena rostriformis bugensis (quagga mussel), an invasive species in Lake Geneva. Rapport de la Commission internationale pour la protection des eaux du Léman, Campagne 2020.
- Roe, S.L., MacIsaac, H.J. (1997). Deepwater population structure and reproductive state of quagga mussels (Dreissena bugensis) in Lake Erie. Canadian Journal of Fisheries and Aquatic Sciences, 54(10): 2428-2433. https://doi.org/10.1139/f97-151