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Impact of a recent invader on a freshwater top predator exposure to microplastics and flame retardants
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Scientists studying rivers in Portugal found that an invasive crayfish species may be helping spread microplastics and toxic flame retardant chemicals up the food chain to otters, top predators that eat the crayfish. This matters beyond otters because it shows how invasive species can act as a hidden "delivery system" for pollutants that build up in animals we eat, like fish and shellfish — a reminder that plastic and chemical pollution in waterways doesn't stay contained, and invasive species could make human exposure through seafood worse than expected.
Biological invasions and pollution are pervasive pressures on freshwater ecosystems, yet their combined effects on top predators remain poorly understood. We tested whether the non-native signal crayfish, Pacifastacus leniusculus (Dana, 1852), increases exposure to microplastics and polybrominated diphenyl ethers (PBDEs) in Eurasian otters, Lutra lutra (Linnaeus, 1758). Along the Rabaçal and Tuela River basins (NE Portugal), 10 invaded and 4 non-invaded sites were surveyed. We quantified riverbank macroplastics (ATR-FTIR), microplastics (Raman microscopy), and PBDE congeners (GC–MS) in otter spraints and crayfish. Macroplastics were dominated by polyethylene and polypropylene, with no spatial differences in abundance or colour. Microplastics were detected in otter spraints and signal crayfish; blue fibres (47%) and nylon (56%) were prevalent, and otter spraints from invaded sites contained higher microplastic loads. Blue fibres covaried between crayfish and otters, suggesting trophic transfer. PBDE concentrations generally did not differ between sites, but otter spraints from invaded sites showed higher 5-MeO-BDE-100 and BDE-183 levels (P = 0.047, P = 0.040, respectively). BDE-47 was higher in Tuela than in Rabaçal. No sex-related differences were found in crayfish. These results indicate a coupled particulate–chemical pathway by which non-native crayfish may intensify otter exposure to microplastics and PBDEs, highlighting the need to include biological invasions in contaminant risk assessments.
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Microplastics, Alien Species and Amphibian Male-specific Predation in River Otter Diet (lutra Lutra). a Study of Two Populations in the Ticino Valley (north Italy) and Sila Massif (south Italy).
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Researchers studied otter diet and distribution in two Italian rivers and found evidence that otters are consuming prey contaminated with microplastics and invasive species. The study highlights how predators at the top of freshwater food chains can accumulate plastic pollution through their diet.
From Core to Front: Microplastic Loads Along a Signal Crayfish ( Pacifastacus leniusculus ) Invasion Gradient
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Even remote, protected mountain rivers in Portugal aren't safe from plastic pollution—researchers found microplastics (mostly tiny fibers from things like plastic bottles and packaging) in the guts of invasive crayfish, with the highest amounts at the invasion's leading edge. This matters because it shows plastic contamination is working its way into wildlife even in pristine-seeming environments, and since these crayfish are eaten by other animals (and sometimes humans), the plastic particles they ingest could move up the food chain.
Microplastic burden in invasive signal crayfish (Pacifastacus leniusculus) increases along a stream urbanization gradient
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Researchers found microplastics in the digestive tracts of invasive signal crayfish at every site along a stream gradient from rural to urban, with concentrations rising as more of the upstream area was developed — and detected microplastics in crayfish tail muscle tissue for the first time. Because crayfish are important prey for many species, their accumulation of microplastics in both gut and tissue suggests these pollutants can move through freshwater food chains more broadly than previously recognized.
Anthropogenically altered trophic webs: alien catfish and microplastics in the diet of Eurasian otters
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Researchers analyzed Eurasian otter diet along Italy's River Ticino using spraint analysis, finding otters adapted to feed heavily on invasive European catfish, and recording for the first time microplastic particles—polyethylene terephthalate and polyamide—in otter feces, indicating microplastic transfer through freshwater food webs.
Modelling the transfer and accumulation of microplastics in a riverine freshwater food web
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Researchers built a computer model of a river food web in Ireland to track how microplastics move from invertebrates through fish to otters, finding that microplastics do not appear to magnify in concentration as they travel up the food chain, though more data on how long organisms retain plastics is still needed.
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When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.