08 Jan The activity of fiddler crabs and other mangrove organisms challenges paradigms of plastic degradation in the environment
Recent scientific research reveals that fiddler crabs (Minuca vocator) inhabiting mangrove forests are playing a key—previously unknown—role in the transformation and degradation of plastic in these ecosystems, which are considered reservoirs for the accumulation of plastic waste. The research shows that, contrary to the widely accepted belief that plastic remains virtually unchanged for decades or centuries under the exclusive action of physico-chemical processes, degradation through biological processes can occur on timescales of days to weeks.
The study, published in the scientific journal Global Change Biology on December 17, 2025, was conducted in highly contaminated mangroves of the Gulf of Urabá, in the Colombian Caribbean. Using fluorescently labeled polyethylene particles, the researchers demonstrated that fiddler crabs ingest large amounts of microplastics present in the sediment, fragment them through their digestive processes, and then excrete them.
These animals move large volumes of sediment during their burrowing and feeding activities, which is why they are considered “ecosystem engineers.”
The accumulation of excreted fluorescent particles led to their detection in the sediment days after the start of the experiment, demonstrating that this factor of plastic degradation is much faster than traditionally accepted mechanisms such as solar radiation or wave action.
Fiddler crabs (Minuca vocator)
The research was led by Professor José M. Riascos and carried out by an international team including the Universidad de Antioquia (Turbo and Medellín campuses), the University of Exeter, and the Corporation Center of Excellence in Marine Sciences (CEMarin). The study has attracted global interest and has been covered by international media such as the BBC, Euronews, and various outlets across Europe, Asia, and Latin America.
Professor Riascos explained:
We set out to answer three specific questions. The first was: what is the uptake of microspheres by the crab under natural feeding conditions? Second, we wanted to know how the microspheres are distributed among the main organs. And finally, we sought to determine whether the interaction between the crab and the microspheres resulted in their physical fragmentation into smaller particles.
“There are many stories about the harmful impacts of plastic waste on animals and plants,” says Tamara Galloway, Professor of Ecotoxicology in the Department of Biosciences at the University of Exeter. “But less frequently studied is the opposite: how animals interact with plastic waste and how they affect it, especially at pollution hotspots.”
The results indicate that crabs ingest microplastics in amounts up to 13 times higher than the quantities present in the surrounding sediment, with an uneven distribution among their organs, particularly in the hindgut and the hepatopancreas.
Graphical abstract by: José M. Riascos
This finding has global implications, as more than half of the world’s mangroves are located near rivers, ports, and large population centers that discharge enormous amounts of plastic waste, turning these ecosystems into true accumulation hotspots. Contrary to expectations, dense populations of fiddler crabs are found in these areas. Demonstrating that these organisms can accelerate plastic degradation reshapes our understanding of the ultimate fate of plastic waste in nature.
However, scientists warn that accelerating the process of plastic degradation has negative implications for humans. Faster fragmentation of plastic implies the formation and release of nanoplastics—particles that may be more harmful due to their interaction with other contaminants and their ability to enter organism tissues and spread along the food chain. This raises new questions about the long-term effects of plastic pollution, even when it is biologically transformed.
In addition, parallel research funded by CEMarin and published in the journal Marine Environmental Research suggests that while crabs play a leading role in degradation through digestive processes, other organisms degrade plastic through “bioerosion.” Plants, mollusks, and crustaceans, among others, drilled, scraped, bit, and fractured different materials experimentally placed on the mangrove floor, in the same way they do with hard materials found in nature. Taken together, these findings reinforce the idea that living organisms are not passive actors in the face of pollution, but active participants in the transformation of plastic in the environment.
If you are interested in a copy of the full article, please contact Professor José M. Riascos (jm.riascosv@gmail.com).