The research addresses one of the most perplexing puzzles in marine science, known as the ‘missing plastic’ paradox. Ocean-input models predict far more microplastic floating at the sea surface than scientists actually find there, suggesting that most plastic sinks. Marine sediments are now recognized as the principal global sink, potentially sequestering 70 to 90 percent of all plastic entering the ocean. Dense polymers such as polyethylene terephthalate and polyvinyl chloride sink directly, while buoyant polymers like polyethylene and polypropylene are dragged down after biofouling — the accumulation of microbial films — increases their density. Yet the seafloor is not a dead end. Once particles arrive, the fate of burial, resuspension, or transfer up the food chain is governed by the organisms living in the sediment, and that is where nematodes take center stage.

To probe this hidden role, a team led by Flávia Juliana Lobato de França and Giovanni Amadeu Paiva dos Santos of the Universidade Federal de Pernambuco in Brazil, together with Anna-Maria Vafeiadou and Tom Moens of Ghent University in Belgium, ran two independent microcosm experiments using sediment from Cupe Beach in Ipojuca, Pernambuco, Brazil. Each experiment used glass beakers holding 400 grams of sediment — a blend of natural live sediment and defaunated sediment that had been frozen and thawed to remove animals while preserving much of the native microbial community. The worms were exposed to fluorescent polystyrene microspheres just one micrometer in diameter, a size chosen to mimic the bacterial prey that many deposit-feeding nematodes naturally consume. Exposure densities spanned 10³, 10⁵, and 10⁷ particles per milliliter of sediment, with the lowest reflecting levels found in moderately polluted coastal sediments and the higher tiers representing plausible future scenarios. One experiment ran for nine days, with sampling at days three, six, and nine; the other stretched to thirty days, with sampling at days fifteen and thirty.

The results were strikingly conditional. Ingestion was detected exclusively in the highest-density treatment. In the short-term experiment, a total of 4,452 particles were quantified across 13 of the 52 nematode genera identified, and the community’s gut burden nearly doubled between day three and day nine, rising from an average of 294 to 581 particles. Most particles accumulated in the intestine rather than the pharynx, with the posterior gut holding significantly more than the anterior region — a pattern consistent with the posterior intestine serving as the principal site of retention and transit. In the long-term experiment, total uptake was far lower, just 571 particles across ten genera, and did not increase significantly with exposure time, hinting at a dynamic equilibrium in which particles are rapidly ingested and egested rather than stored indefinitely.

Even more revealing was who was doing the eating. In the short-term experiment, a single genus, Daptonema — which made up more than 87 percent of the community’s relative abundance — accounted for 89.9 percent of all ingested particles, averaging roughly ten particles per individual. Other genera such as Rhynchonema, Marylynnia, Viscosia, and Theristus collectively contributed about eight percent. Daptonema is a non-selective deposit-feeder with an opportunistic, r-selected life strategy, classified as a colonizer-persister group 2 organism, and its dominance of the sequestration function perfectly matched the researchers’ hypothesis that fast-living, indiscriminate feeders with wide buccal cavities would be the main gateways for microplastic entry into the benthic food web. In the long-term experiment, where the starting community was structurally very different and Daptonema was nearly absent, the sequestration role shifted to a consortium of four genera — Rhynchonema, Latronema, Marylynnia, and Theristus — which together carried over 91 percent of ingested particles. These were functionally more diverse taxa, dominated by more K-selected, persistent life strategies, yet all shared fairly wide buccal cavities.

That anatomical detail appears to be a fundamental constraint. Selective deposit-feeders, which possess tiny or absent buccal cavities, showed minimal to no ingestion, and previous work has demonstrated that microplastic uptake is only possible when the buccal cavity exceeds the particle diameter by a factor of roughly 1.3. Body size mattered too: across both experiments, the researchers found significant positive correlations between individual and community biomass and the number of ingested particles, suggesting that larger worms, with higher feeding rates and larger gut volumes, are more efficient sequestrators. In the short-term trial, Daptonema’s individual biomass correlated strongly with its particle load, while in the long-term trial total community biomass correlated with total ingestion, indicating that the sequestration function had become distributed across the community’s collective biological mass rather than concentrated in one taxon.

The most counter-intuitive finding, however, concerned harm rather than uptake. The most severe community-level impacts — reduced nematode density and biomass — occurred at the lowest and intermediate plastic densities, precisely where no ingestion was detected. In the 10³ particles per milliliter treatment, Daptonema’s abundance collapsed to less than 17 percent of the community by day three, and nematode densities remained significantly below control levels throughout the short-term experiment. The researchers propose several possible explanations, including a behavioral avoidance response that exhausts the animals metabolically, a hormetic stress reaction in which low doses trigger stronger effects than high ones, or adverse effects mediated by direct physical contact with particles — polystyrene microspheres have previously been shown to inhibit nematode reproduction even without detectable ingestion. At the highest density, by contrast, Daptonema persisted at control-like abundances while simultaneously functioning as the community’s principal biological sink, a striking decoupling of the sequestration function from direct ecological harm.

Long-term exposure told a different story again. Chronic exposure consistently lowered nematode density across all treatments, and the community lost 16 of its 37 genera between days fifteen and thirty, although much of that loss occurred in the control microcosms as well, pointing to experimental bottling effects. The dominance structure shifted transiently: at day fifteen, the control was dominated by Chromadorella, while the highest-density treatment was co-dominated by Rhynchonema, Latronema, and Theristus. Crucially, in the long-term experiment the researchers found a complete decoupling between community structure and sequestration function — none of the standard diversity metrics correlated with total ingestion, suggesting that under chronic exposure, the identity and traits of the taxa present, rather than their abundance or diversity, determine how much plastic the community processes.

So how much does any of this matter for the ocean’s plastic budget? The team ran a back-of-the-envelope calculation assuming a realistic intertidal community of about 1,000 nematodes per 10 square centimeters, all non-selective deposit-feeders carrying roughly ten particles each, all eventually eaten by predators. In a sediment volume containing 10⁷ particles per milliliter, such a community would transfer about 1.1 × 10⁴ particles to higher trophic levels out of a total sediment load of 2 × 10⁸ — less than one percent. The quantitative importance of nematode gut storage for trophic transfer therefore appears very limited. But the authors caution against complacency. Gut loads at any instant are a minute fraction of total throughput, since many nematodes pass gut contents in minutes to hours, and if gut enzymes dislodge or modify pollutants adsorbed to plastic surfaces, the cumulative pollutant exposure could exceed what gut loads suggest by one or two orders of magnitude.

The study paints the seafloor not as a passive graveyard for plastic but as an active biological processing zone, where the smallest and most abundant animals continuously encounter, ingest, and transform microplastic particles. The sequestration function is conditional, dependent on a high-contamination threshold well beyond most currently recorded sediment loads, and its identity shifts over time from opportunistic specialists to a more diverse, persistent consortium. The authors acknowledge the limitations of using a single polymer type and particle size in simplified microcosms, and they call for validation under natural conditions, experimental tests of trophic transfer and its consequences for carbon assimilation in higher consumers, and assessments of how different polymer shapes and sizes alter these pathways. As plastic production continues and coastal sediments near urban and industrial zones already approach the densities tested here, the humble nematode may prove to be a small but telling barometer of how the ocean’s largest waste problem plays out at its smallest scale.

Subject of Research: Microplastic sequestration and community-level effects of microplastic exposure in marine nematodes

Article Title: Community dynamics and functional traits drive microplastic sequestration by marine nematodes

Article References: de França, F. J. L., Silva, R. B. D., França, D. A. D. A., Frasson, I. D., Silva, G. A. X. D., Rodrigues, M. E. L., Pessoa, G. L., Vafeiadou, A.-M., Moens, T., & dos Santos, G. A. P. (2026). Community dynamics and functional traits drive microplastic sequestration by marine nematodes. Discover Oceans, 3(1), Article 16. https://doi.org/10.1007/s44289-026-00125-5

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00125-5

Keywords: marine nematodes, microplastics, benthic sediments, meiofauna, functional traits, missing plastic paradox, polystyrene microspheres, buccal cavity morphology, trophic transfer, community ecology, Daptonema, ocean plastic pollution