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•Cellular energy threats: Presence of mercury was linked to inefficient fuel use during energy production in wild birds’ cells, while certain per- and polyfluoroalkyl substances (PFAS) may prevent protective responses to cell stress
•Foraging shapes exposure: Older birds and males carried more mercury through diet, food choice and lifetime accumulation in a key component of the birds’ blood, however PFAS levels showed no such links, suggesting different contamination routes
•Conservation questions: Scientists fear cell-level impacts may compound with those of other ocean threats like global heating and overfishing, raising critical questions about long-term effects on breeding and survival
Common pollutants are disrupting energy production at the cellular level in wild seabirds, potentially affecting fitness, new research reveals. The study, published in Environment & Health, focused on Scopoli's shearwaters breeding on Linosa, a small and remote volcanic island in the Sicilian Channel. Scientists found that widespread contaminants such as mercury and certain PFAS compounds affect the function of mitochondria, tiny cellular powerhouses that generate energy for activities from flight to reproduction.
In the oceans, mercury is often converted to highly dangerous methylmercury by bacteria, which accumulates in tissues and concentrates up the food chain, meaning top predators carry the highest levels. PFAS – synthetic "forever chemicals" found in products including non-stick cookware and stain-resistant fabrics – accumulate in greater numbers despite international efforts to control their use. These pollutants are highly toxic even at low concentrations and reach the ocean through the atmosphere and surface runoff. Laboratory studies showed they could impact energy generation in mitochondria, but these studies may not reflect pollution levels found currently in ecosystems, and the effects in wildlife remained unknown until now.
The international team of researchers lead by Stefania Casagrande, a scientist at the Max Planck Institute for Biological Intelligence, measured both pollutant levels and mitochondrial function in Scopoli's shearwaters. Mitochondria build up an electrical charge that drives production of adenosine triphosphate (ATP), the cell's energy currency. In birds with higher mercury levels, mitochondrial membranes become more porous through a process known as "proton leak": letting more energy dissipate without producing ATP, like water bypassing a hydroelectric dam's turbines. High levels of certain PFAS compounds have the opposite effect, stiffening membranes and reducing energy leak, but blocking a safety valve that prevents harmful molecule buildup, potentially causing a different type of oxidative cellular damage.
"Pollutants of global concern, such as PFAS and mercury, are well known to be toxic. However, it is only now that advancements in fine-scale technology and minimally invasive field methods have allowed us to understand their effects on wildlife at the ecosystem scale, with important implications for developing conservation approaches," says Guadalupe Lopez-Nava, co-first author and graduate student at the Max Planck Institute for Biological Intelligence. "We found mercury and certain PFAS compounds disrupt cellular energy production in wild shearwaters, affecting cellular energy efficiency. While cells may compensate by increasing energy production, this itself is costly, and even small shifts in cellular efficiency could silently undermine fitness."
Connecting diet to exposure and cellular damage
As top predators with decades-long lifespans, shearwaters accumulate contaminants over time, making them indicators of ocean health. The team sampled 52 breeding adults over two seasons, measuring mercury and mitochondrial function in all birds, with PFAS analyzed in 20 birds from one season. Stable isotopes – chemical fingerprints revealing diet and foraging location – connected what birds ate to their exposure levels and cellular impacts. Mercury was higher in older birds and males (females expel mercury through egg-laying) and increased with trophic position, matching expected food chain patterns. PFAS showed no such links to age, sex, or diet, suggesting fundamentally different contamination routes than mercury. The scientists say understanding these different exposure pathways is critical for protecting seabird populations and developing targeted pollution reduction strategies.
"Chemical pollution is one of the more complex threats to marine ecosystems at all levels, due to its inconspicuous nature and diverse impacts," says Lucie Michel, co-first author and graduate student at the University of Giessen. "During the demanding breeding season, when adults alternate long self-provisioning and short foraging trips while caring for chicks, energy costs from pollutant exposure could be especially significant. Future work must examine impacts on survival, breeding success, and overall fitness. It is also critical to understand these impacts in the context of other threats to wildlife such as including overfishing, plastic pollution, and global heating. Long-term monitoring will be essential to answer these questions, with implications also for understanding their impacts on human health, since we face similar exposures."
Dr. Stefania Casagranda
Scientist
MPI for Biological Intelligence
stefania.casagrande@bi.mpg.de
Pollutant Exposure Shapes Mitochondrial Bioenergetics in a Wild Seabird
Guadalupe Lopez-Nava*, Lucie Michel*, Giacomo Dell’Omo, Petra Quillfeldt, Paco Bustamante, Stefania Casagrande
* contributed equally to this work
Environment & Health, online 22 December 2025
DOI: 10.1021/envhealth.5c00297
https://www.bi.mpg.de/hau - Research group website
Researchers found that common pollutants like mercury and certain PFAS compounds (forever chemicals) ...
Copyright: © MPI for Biological Intelligence / Guadalupe Lopez-Nava
The team sampled breeding adults over two seasons on Linosa measuring mercury, PFAS and mitochondria ...
Copyright: © MPI for Biological Intelligence / Guadalupe Lopez-Nava
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