For four years, Maeva Goulais studied the impact of plastic materials used by pearl farmers on oysters, bacteria and the balance of ecosystems. His research on the Tuamotu atolls reveals widespread pollution and sometimes unsuspected toxic effects. The researcher offers concrete solutions to limit the damage: better regulate materials, reduce their use and also strengthen waste management.
Is pearl farming, fenua’s second resource, also a threat to marine ecosystems? Maeva Goulais, a 30-year-old doctoral student, devoted four years of research to this question. In her thesis, she examines the impact of pearl plastics on lagoons and suggests ways to make this activity more sustainable. To understand the effects of plastic pollution on ecosystems, Maeva Goulais carried out several experiments mainly concerning four atolls of the Tuamotu: Takapoto and Takaroa, where pearl farming is well established, as well as Tikehau and Anaa, two atolls little or not affected by this activity. One aspect of his research focused on the growth of pearl oysters. These were divided into four batches and submerged on each atoll for six months. “We noticed significant differences in the growth of animals depending on the atolls. Anaa, for example, was the place where oysters grew best”she explains.
The multiple origins of plastic pollution
But by analyzing the amount of plastic present in oysters and in water, an unexpected result appeared: “We found as many plastic particles in oysters from pearl atolls as in those from non-pearl atolls”underlines Maeva Goulais. An observation that pushed the researcher to dig deeper. She discovered that cellulose fibers, of natural or anthropogenic origin, play a role in the growth of oysters. “The more these fibers an oyster contained, the less it developed”she specifies. In fact, this cellulose can be natural because we know, for example, in the Tuamotu, there are many coconut groves. So there’s nothing we can do about it. But there is also a large entropic contribution, which therefore comes from humans, and which could be due to the discharge of wastewater, particularly water from washing machines into the lagoon.”
Toxicity of pearl plastics: alarming results
Results which therefore confirm that the contamination of a lagoon is certainly due to local pollution, that produced by the inhabitants, but also comes largely from external contributions. Beyond the direct contamination of oysters, Maeva Goulais was also interested in the biological effects of pearl plastics on other marine species. Using larval tests, she observed the development of eggs of five marine species placed in plastic solutions at different concentrations. The results are clear: “Some larvae presented abnormalities or developmental delays, confirming the toxicity of plastic leachates. » The doctoral student therefore insists on the need to identify the most toxic chemical additives among those used in pearl culture collectors and ropes. “ Some additives may be harmless, but others must be very toxic. The interest would ideally be to prohibit its use for materials which are destined to end up in water. So already, it would be a big step to be able to really limit and regulate the additives used in pearl and aquaculture plastic materials. »
Pathogenic bacteria and risks for lagoons
Another part of his thesis explores the biological effects of plastic waste on lagoons. By this, mean their impact on bacteria. Invisible but “extremely important” organisms for marine ecosystems. “it’s true that we rarely become aware of it, because it’s invisible. It’s a bit of a forgotten compartment”says the doctoral student. For two months, Maeva Goulais therefore followed their evolution in aquariums containing varying quantities of plastic. “In the most polluted aquarium, certain pathogenic bacteria were over-represented” she explains. These bacteria, while representing a risk for pearl farming, also threaten the balance of marine ecosystems.
Faced with these findings, Maeva Goulais calls for priority actions which must come from public authorities. “Pearl farmers are aware of their impact and ready to collaborate, but ambitious public policies are needed to support this transition”she assures. Her work is similar to that of another UPF doctoral student, Margaux Crusot, whose research on a biomaterial capable of replacing plastic in pearl farms earned her a prestigious prize last year. Also related to research on a method of collecting waste in pearl-producing atolls. For Maeva Goulais, it is urgent to regulate the import and use of pearl plastics by controlling their chemical composition. It would also be necessary to reduce the current quotas, which she considers “extremely high” but also to set up systematic campaigns for the recovery and treatment of waste from pearl farming.
