published in the journal Frontiers in Marine Science, demonstrates for the first time that fish larvae in the natural environment already contain microplastics immediately after hatching, even before they begin to feed.
Microplastics are now widely distributed throughout the environment: in water, in the air, in the soil and even inside living organisms, including marine life. However, most studies to date have focused on adult fish, including those used for human consumption. The history of these microplastics, however, remained unknown: it was not clear exactly when this contamination begins throughout the life cycle.
It was during her PhD in Aquatic Sciences at ICBAS that Sabrina Rodrigues, a researcher in the Fish Ecology and Sustainability group at CIIMAR, collected wild fish larvae directly from the natural environment and analysed the presence of microplastics at all early stages of development, including the very earliest stage, immediately after hatching.
Microplastics in early stages of development
The results now published by the CIIMAR team in the study “Are fish larvae contaminated before they start eating? First evidence of microplastic contamination in the yolk-sac of wild fish larvae” show that these microplastics are already present in larvae with a yolk sac, a stage at which the organisms have not yet opened their mouths or begun feeding.
“Previous studies on microplastics in fish were largely limited to laboratory organisms or focused solely on adults that were already actively feeding. This study was different because it sought to understand what happens during all stages of development,” explains Sabrina Rodrigues, the study’s lead author.
The results indicate that microplastic contamination at this stage does not occur through ingestion, but likely through transfer from mother to offspring, via the egg or the yolk – the nutrient-rich substance in the egg, composed mainly of proteins and fats, which nourishes the embryo during its development. This route of exposure had never, until now, been documented in wild fish.
“As a researcher, finding microplastics in larvae that had never opened their mouths was both fascinating and worrying. We realised that plastic pollution affects fish from the very start of their lives,” adds Sabrina.
A direct link to the environment
But the findings do not stop there. The study, led by CIIMAR researchers Sandra Ramos and Marisa Almeida, also found that the amount of microplastics in the larvae directly reflects the levels of this pollutant present in the surrounding environment. In other words, the higher the concentration of microplastics in the water, the greater the contamination in the larvae, regardless of species, size or stage of development.
A new route of exposure
“Our results open up a new line of research, particularly regarding how microplastics can be transmitted from adults to their offspring, how fish health is affected from these early stages, and what this means for marine ecosystems and the safety of seafood products,” says Sandra Ramos, opening up new horizons for future research.
This work thus raises new and relevant scientific questions: what are the impacts of this early exposure on the development, growth and survival of fish? And how might this initial contamination spread throughout the marine food chain?
By demonstrating that exposure to microplastics begins earlier than previously thought, the study broadens our understanding of the vulnerability of marine organisms and “underscores the need to reduce plastic pollution in the oceans at a time when the public seems to have become desensitised to news about plastic pollution”, concludes Marisa Almeida.