Microplastic pollution is not only a question of how much plastic is in the ocean, but also when fish meet it. A global analysis now suggests that reproductive seasons can turn familiar contamination into a sharper ecological threat. By bringing together seawater observations, fish microplastic burden records, reproductive traits and environmental data, the study shows that spawning windows often overlap with pollution hotspots and co-occurring chemical contaminants. The work highlights spring spawning grounds as a vulnerable point in the marine life cycle and suggests that protecting fish populations will require pollution management that follows biology, not just annual averages or static maps.
Microplastics, plastic fragments smaller than 5 millimeters, are widely recognized as stressors in aquatic ecosystems. They can be ingested by fish, disturb reproduction and act as carriers for persistent pollutants. Yet many risk assessments still treat contamination as relatively steady over time. That assumption may miss what happens when fish gather in coastal spawning areas, where river inputs, wastewater, shipping and seasonal environmental change can converge. Some species also spawn in narrow windows or move into nearshore nurseries that are already polluted. Threatened species are especially at risk because limited ranges and low population resilience leave little room for added stress. Due to these challenges, deeper research is needed into how reproductive timing reshapes microplastic exposure and ecological risk.
The study was led by researchers from the Key Laboratory of Pollution Processes and Environmental Criteria/Carbon Neutrality Interdisciplinary Science Centre, College of Environmental Science and Engineering, Nankai University, and the Fujian Ocean Innovation Center. The article will appear (DOI: 10.1016/j.ese.2026.100732) in Environmental Science and Ecotechnology . and examines how microplastics, spawning timing, pollutant vectors, warming and low-oxygen conditions combine across global marine fish communities and threatened species.
The team integrated 6,327 in situ seawater microplastic observations, 3,959 fish microplastic burden samples, 528 polycyclic aromatic hydrocarbon (PAH) records and 1,891 perfluorooctane sulfonate (PFOS) records. These data were linked with reproductive parameters for 992 marine fish species across 65 large marine ecosystems (LMEs). Using species sensitivity distribution (SSD) analysis, machine learning, Shapley additive explanations (SHAP), structural equation modeling and bioconcentration factor (BCF) comparisons, the researchers mapped where spawning fish may face amplified exposure. They found that 7.8% of global critical spawning grounds exceeded ecological safety thresholds. In the Baltic Sea and Gulf of Thailand, mean microplastic concentrations in spawning grounds were more than 7.8 times the global average. From 1998 to 2023, global mean concentrations rose from 0.2 to 0.3 items per cubic meter, while habitats crossing two key risk thresholds expanded by 72.4% and 184.0%. Reproductive individuals also carried higher microplastic burdens than non-reproductive individuals, and 45.5% of LMEs showed enhanced transfer efficiency during reproduction. Combined pollutant risk peaked in March, underscoring a spring risk window that would be blurred in annual averaging. The microplastic-associated PAH interaction index was 42.3% higher during reproduction, and the PFOS interaction index was 16.2% higher. Warmer and more oxygen-poor waters further increased vulnerability.
The authors said the findings reframe microplastics as a problem of timing as well as concentration. During spawning, they said, fish are physiologically strained and often concentrated in habitats where plastic particles, chemical contaminants and environmental stressors meet. A short reproductive window can therefore become a decisive exposure window. They said this life-cycle view helps explain why critically endangered species may experience disproportionate risk, even when average pollution levels appear moderate across the year, and why seasonal management can reveal risks that annual surveys may miss.
The results point to practical changes in ocean management. Seasonal risk maps could help managers focus monitoring, wastewater controls, shipping measures and habitat protection on months and places where spawning fish are most exposed. Conservation plans for threatened species should also consider reproductive-period exposure instead of relying only on annual averages or single-pollutant thresholds. The study found that critically endangered species had combined risk indices 9.0 and 13.3 times higher than least-concern species for microplastic-associated PAHs and PFOS, respectively. This gap shows why endangered populations may need more targeted safeguards. As warming and ocean deoxygenation intensify coastal stress, protecting spring spawning windows may become a direct strategy for sustaining biodiversity and fisheries.
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References
DOI
Original Source URL
https://doi.org/10.1016/j.ese.2026.100732
Funding information
This research was funded by the Fujian Ocean Innovation Center (Grant No. 25FV0CWZ02 ), the China Postdoctoral Science Foundation ( 2025M781188 ), the National Natural Science Foundation of China (Grant No. 22576112 ), Natural Science Foundation of Xinjiang Uygur Autonomous Region (Grant No. 2025D01E63 ), Tianjin Municipal Natural Science Foundation (Grant No. 25JCYBJC00100 ), the Central Public Research Institutes Basic Funds for Research and Development (Grant No. 1102021600110070049 ), the Fundamental Research Funds for the Central University and the 111 progamme (Grant No. B17025).
About Environmental Science and Ecotechnology
Environmental Science and Ecotechnology (ISSN 2666-4984) is an international, peer-reviewed, and open-access journal published by Elsevier. The journal publishes significant views and research across the full spectrum of ecology and environmental sciences, such as climate change, sustainability, biodiversity conservation, environment & health, green catalysis/processing for pollution control, and AI-driven environmental engineering. The latest impact factor of ESE is 14.3, according to the Journal Citation ReportsTM 2024.
Environmental Science and Ecotechnology
Global microplastic pollution poses a disproportionate reproductive threat to critically endangered marine fishes
9-Jul-2026
The authors declare that they have no competing interests