On May 27, the research schooner Tara just left Lorient for a 6-month expedition on European rivers. Aboard Tara, 40 scientists will relay each other to assess the concentration of plastic waste carried by rivers and its impact on marine organisms. Jean-François Ghiglione, eco-toxicologist at the Oceanological Observatory of Banyuls provides details:
This is your sixth embarkation aboard the schooner Tara, but this time, after seas and oceans, you’ll go inland following the rivers. The aim is to investigate the state of plastic pollution in European rivers. How did this project get started ?
Jean-François Ghiglione: It’s a followup to the 2014 campaign in the Mediterranean Sea which proved it to be the region in the world most affected by plastic pollution. In the past 10 years, we’ve shown that micro-debris are found in all oceans, including the polar regions. Faced with such a dispersion, oceanographers and sailors know that cleaning up the sea is impossible. We have to act upstream, on the rivers, because we know that 80% of the plastic waste arriving at sea comes from the land and passes through rivers. It’s estimated that 8 million tonnes of plastics wind up in the sea each year. Knowledge of the sources of pollution is therefore a priority if we want to fight against this scourge and take drastic measures on a European scale.
During the Tara Mediterranean expedition in 2014, the Manta net was used to collect plastic fragments on the surface. Right-hand photo shows the debris caught in the net after towing for one-hour © S. Bollendorff / N. Pansiot / Fondation Tara Océan
There were no studies on plastic waste in European rivers?
J.-F. G. : Only spotty studies exist on the subject. Recent work shows that we underestimate the amount of plastic waste present, especially because we do not take into account microplastics. The latest research done by British colleagues on the Thames surprised us all: it reveals that 66% of the waste in that river consists of microplastics. Until now, we thought plastics were fragmenting at sea under the influence of UV or waves. By what mechanisms and where do they actually fragment? This, among other things, is what we’ll try to understand, because these particles—measuring less than 5 mm— enter the entire food chain and constitute the greatest threat.
During this mission, we’ll study the sources and mechanisms of pollution/dispersion of microplastics from land to sea and their impacts on marine biodiversity. Samples will be collected in the sea-land continuum: several kilometers from the coast, in estuaries and rivers, upstream and downstream from big cities like London, Lisbon or Hamburg. About 15 French laboratories are involved in this project.
You’re starting from the estuary of the Thames (England); then the Elbe (Germany); the Rhine (Holland); the Seine, Loire and Garonne (France); the Tagus (Portugal); the Ebro (Spain); the Rhone (France), and finally the Tiber (Italy). How did you determine this route?
J.-F. G. : We chose 10 major rivers in Europe that have already been the subject of studies on which a French or foreign research team is already working. We will quantify the waste, describe it and identify its origins. If we find a lot of PVC residues, we’ll know they come from drain pipes in the roads. If it’s polyethylene terephthalate, the origin will be plastic bottles. In the case of expanded polystyrene, it comes from packaging. Once all these data are collected, we can create models. And thanks to the study of currents, we’ll know their future trajectory—how much and what kind of waste will then be found on coastal beaches, or offshore. This will be done for the 10 rivers studied.
We know that near large cities, river water and therefore microplastics contain many pollutants. Are you going to research this subject?
J.-F. G. :Yes, this is the second part of our research: studying the impact of pollutants attached to these microplastics on marine biodiversity. Plastics act like sponges and absorb everything: hydrocarbons as well as pesticides. One month before the passage of Tara, we will install cages containing mussels, both upstream and downstream of the big cities located on the estuaries, in order to compare the two results. These animals are good bioindicators because they filter and capture these pollutants. We will also analyze the presence of toxic substances in organs of other species at different points along the river and beyond the estuary.
There are also additives such as phthalates or bisphenol A, used in the composition of these plastics.
J.-F. G. : Part of our mission is to analyze the additives. We know that once ingested by fish, these endocrine disruptors have effects on their development and reproduction.
Studies on the effect of these substances on the perception of the environment are underway in our laboratory. The objective of this expedition is to try to specify the role of these microplastics in the diffusion and transport of all these pollutants and toxic substances in fresh and salt water, and to look for a possible cocktail effect on the fauna.
The “plastosphere” consists of the great diversity of organisms that live on plastic © Fondation Tara Océan
During your previous missions, you showed that these microplastics were colonized by many microorganisms. Do you think these are the same species found at sea?
J.-F. G. : We will identify them and, for the first time, carry out a study on the species that transit from rivers to the sea. These plastic particles constitute a new habitat for many species of bacteria, viruses, or microalgae. There are so many that by moving on these small artificial rafts, these micro-organisms can travel long distances and modify ecosystems. We will focus our research on the pathogenic organisms present on these debris and on the invasive species, that is to say, those that should not be where they are found.
Are these microorganisms able to move from fresh water to salt water?
J.-F. G. : That’s the whole question. In theory, freshwater pathogens die as soon as they arrive in salt water—but they are found on plastics at sea. It seems that these microplastics act as special refuges; certain bacteria must be able to hide inside and survive. If this is the case, there’s a risk of contagion for mussel and oyster farms. Mussel growers and oyster farmers are looking forward to our results!
During your previous missions aboard Tara, you were able to identify about 15 marine bacteria capable of degrading plastics. Do you think you’ll find more in the rivers?
J.-F. G. :At first glance, yes. Fresh water bacteria are certainly more numerous and have a much greater, faster capacity for plastic degradation than those found at sea. We will collect them and compare them with marine bacteria.
Beyond the scientific research work, what will you do to encourage governments and the European Union to take action?
J.-F. G. : Tara’s previous missions showed that most of the pollution was coming from single-use plastics, and contributed to the ban by the European Union on plastic bags, but also from tableware, cotton ear-buds, drinking straws, micro-beads in exfoliants, and food containers. Our results will be published in the next 2 to 3 years and will guide measures to find alternatives to these plastics. By organizing this mission on a European scale, we intend to form a motivated and involved community of researchers from the different countries we traverse, just as we did in France with the Polymers and Oceans Research Group which today brings together 200 scientists and serves as a relay of information to ministries and industry. We are living in a period of transition and all the indicators are green. We must take this opportunity to mobilize all economic and political forces.
Carina Louart / The CNRS Journal
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