Impact statement

Plastic pollution is a growing threat to ocean health and is no longer confined to surface waters. Plastics and their chemical leachates are increasingly reaching the deep sea, where organisms depend on bioluminescence to find food, avoid predators, communicate and reproduce in complete darkness. Any disruption to the light-based processes extends beyond individual organisms and cascades through food webs, influencing species interactions, food web stability and biodiversity in one of the least explored parts of the planet. This letter highlights deep-sea bioluminescence as a vulnerable ecological process that may serve as an early biomarker of plastic-induced stress and functional ecological change in deep-sea organisms. By linking plastic contamination with functional ecological change, the letter calls for stronger action to reduce plastic inputs, expand monitoring beyond coastal and surface waters and include bioluminescence-based responses as sensitive indicators in future marine plastic pollution assessment frameworks.

Earth’s biosphere encompasses numerous distinctive phenomena with ecological benefits, and bioluminescence is among the most prominent. Bioluminescence is biologically produced light generated through the luciferase-catalysed oxidation of luciferin, the primary light-emitting substrate (Kahlke and Umbers, Reference Kahlke and Umbers2016). Its origin can be traced back to several events in Earth’s history (Widder, Reference Widder2010), which arose at least 40 times across diverse taxa independently (Valiadi and Iglesias-Rodriguez, Reference Valiadi and Iglesias-Rodriguez2013). Current hypotheses propose that the evolutionary origin of bioluminescence lies between the Great Oxygenation Event and the Cambrian Explosion (Wilson and Hastings, Reference Wilson and Hastings201 Reference Amelia, Khalik, Ong, Shao, Pan and Bhubalan2). The rapid rise in atmospheric oxygen during this interval led to increased oxidative stress, creating toxic conditions for many pre-existing anaerobic organisms. Bioluminescence therefore likely emerged initially as a primitive oxygen detoxification mechanism (Timmins et al., Reference Timmins, Jackson and Swartz2001), given that light production occurs through the oxygen-dependent oxidation of an organic molecule (Lee, Reference Lee2017), a common thread among bioluminescent systems (Waldenmaier et al., Reference Waldenmaier, Oliveira and Stevani2012). This phenomenon is relatively rare on land and highly restricted in the terrestrial biota compared to the marine realm (Vršanský et al., Reference Vršanský, Chorvát, Fritzsche, Hain and Ševčík2012). It has representatives in most phyla; among the exceptions are true plants and higher vertebrates (Björn, Reference Björn2008).

Marine bioluminescence serves various purposes such as defence, communication, courtship, predation, aposematism (warning colouration) and counterillumination (marine organisms produce bioluminescent light from their ventral surfaces to match the downwelling light from the ocean surface) (Schramm and Weiß, Reference Schramm and Weiß2024). It is thought to occur in ~80% of eukaryotic life in the deep sea, accounting for a significant share of total ocean biomass (Davis et al., Reference Davis, Holcroft, Wiley, Sparks and Smith2014). The faunal environments beyond the photic zone are largely unexplored and play a role in core ecological functions, such as the ocean’s biological pump. These zones (mesopelagic 100-2000 m, bathypelagic 1,000-4,000 m) host most of the bioluminescent organisms. It is considered a major ecological trait on Earth (Martini and Haddock, Reference Martini and Haddock2017), a prerequisite for the survival of organisms thriving in the dark, deep ocean depths and of utmost importance to marine life (DeLeo et al., Reference DeLeo, Bessho-Uehara, Haddock, McFadden and Quattrini2024). Any changes in the bioluminescence of these organisms can impede their survival and lead to possible collapse of the ambient ecosystem functions in which they are associated, from both trophic and structural standpoints. The trophic standpoint refers to the organism’s role in the food web, where changes can disrupt feeding interactions, energy transfer and predator-prey relationships; the structural standpoint refers to the organism’s contribution to the organisation and stability of the ecosystem, including its influence on habitat formation and community composition.

Marine pollution has extended its reach into the deep ocean in recent years (Jamieson et al., Reference Jamieson, Malkocs, Piertney, Fujii and Zhang2017; Dasgupta et al., Reference Dasgupta, Peng, Chen, Li, Du, Zhou, Zhong, Xu and Ta2018), and the consequences in the depths remain largely unknown. Among pollutants, plastics in their macro- and micro-forms {nanoplastics (<1 μm), microplastics (1 μm-5 mm), mesoplastics (5-25 mm) and macroplastics (>25 mm)} are being detected in the deep ocean (Zhu et al., Reference Zhu, Rochman, Hardesty and Wilcox2024; Froján et al., Reference Froján, Bergmann, Woodall, Mestre, Baker, Gertz, Escobar-Briones, Ekpe, Pham, Martins, Dasgupta, Bartolotta and Levin2023). A suite of pollutants (for example, heavy metals, organic contaminants, pesticides and endocrine disruptors) is known to interact with bioluminescence (Agathokleous, Reference Agathokleous2025), which forms the basis of now widely used luminescent bacteria-based biosensors (Li et al., Reference Li, Zhao, Du, Ren, Ding and Wang2024). Bacteria-based biosensors are analytical devices that use living bacteria, including engineered strains, to detect specific substances such as toxins, environmental pollutants or pathogens by converting biological responses into measurable signals, such as fluorescence or electrical outputs (Zhang et al., Reference Zhang, Liu, Song and Wang2023).

Microplastics are known to interfere with the bioluminescent patterns of symbiotic marine luminous bacteria Photobacterium leiognathi (De Jesus et al., Reference De Jesus, Iqbal, Mundra and AlKendi2024) and Photobacterium phosphoreum, which live in symbiosis with many deep-sea marine organisms (Senko et al., Reference Senko, Stepanov, Aslanli and Efremenko2025). Thus, plastic particles can induce bioluminescence quenching, which is the reduction or inhibition of light emission from a biological reaction. More than 250 highly diverse individual chemicals and complex mixtures of multiple pollutants have been found to induce bioluminescence hormesis in some microorganisms, including a wide range of globally relevant pollutants and emerging contaminants (Agathokleous, Reference Agathokleous2025). Bioluminescence hormesis is a phenomenon in which low-dose chemical stressors stimulate increased light emission in bacteria before inhibiting it at higher concentrations. This raises concerns, as marine water has higher concentrations of plastic leachate than other environments (Omidoyin and Jho, Reference Omidoyin and Jho2024). Plastic leachates comprise complex mixtures of chemical additives such as bisphenols, phthalates and flame retardants that are released from plastic materials into the environment, particularly during degradation processes such as weathering (Delaeter et al., Reference Delaeter, Spilmont, Bouchet and Seuront2022). However, the release of organic additives is slower in deep-sea environments due to low temperatures, the absence of UV radiation, high hydrostatic pressure and reduced oxidative weathering (Fauvelle et al., Reference Fauvelle, Garel, Tamburini, Nerini, Castro-Jiménez, Schmidt, Paluselli, Fahs, Papillon, Booth and Sempéré2021). Small microplastic particles and nanoparticles can disrupt quorum sensing (QS) in the marine luminescent bacterium Aliivibrio fischeri. QS is a bacterial communication system where cells release and sense small signalling molecules called autoinducers. When these signals reach a threshold level at high cell density, they coordinate gene expression and control collective behaviours such as bioluminescence (Miller and Bassler, Reference Miller and Bassler2001). Polyethene microplastic beads alter luminescence time profiles at sub-toxic concentrations, consistent with QS disruption (loss or alteration of communication), even when viability was not strongly affected (Gagné, Reference Gagné2017). Considering the wide variety of plastics and the growing number of chemical leachates in the ocean, these pollutants can interfere with the bioluminescent mechanisms of the deep-sea microorganisms and fauna.

Plastic pollution can plausibly diminish or dysregulate marine bioluminescence through several linked mechanisms. In bioluminescent dinoflagellates, light production is mediated by a luciferin-luciferase reaction occurring within specialised organelles known as scintillons. The luciferin-luciferase reaction is a biochemical light-producing process in which the enzyme luciferase catalyses the oxidation of the light-emitting molecule luciferin in the presence of oxygen (and often ATP), releasing energy as visible light. In organisms such as dinoflagellates, this reaction is triggered by mechanical stimulation, which induces intracellular changes (e.g., a drop in pH) that activate luciferase and lead to rapid light emission (Valiadi and Iglesias-Rodriguez, Reference Valiadi and Iglesias-Rodriguez2013). Consequently, any stressor that impairs cellular integrity, membrane stability, redox homeostasis (balance between oxidants such as reactive oxygen species (ROSs), and antioxidants within a cell, which is essential for maintaining normal cellular function), or overall metabolic functioning can modify the intensity, frequency or consistency of bioluminescent flashes. Evidence from previous studies supports these proposed mechanistic pathways, demonstrating that polystyrene nanoplastics can suppress growth, elevate ROS production and induce lipid peroxidation, a process in which ROS damages membrane lipids (Hazeem et al., Reference Hazeem, Yesilay, Bououdina, Perna, Cetin, Suludere, Barras and Boukherroub2020; He et al., Reference He, Yu, Li, Sun, Chen, Lin, Dai, Wang, Li and Ju2024). In Amphidinium carterae (a benthic marine dinoflagellate), such exposure has further been reported to reduce chlorophyll synthesis and promote particle adhesion and aggregation around cells (Wang et al., Reference Wang, Liu, Huang, Fan, Gao and Liu2021). Together, these compounding effects suggest that plastic-induced stress impairs the physiological processes required to sustain bioluminescent activity. Moreover, microplastic ingestion has been shown to decrease prey uptake, growth and secondary production in heterotrophic dinoflagellates. Although these studies did not directly quantify bioluminescence, the observed reduction in trophic performance suggests that plastic exposure limits the population density required for large-scale bioluminescent blooms (Fulfer and Menden-Deuer, Reference Fulfer and Menden-Deuer2021). Bioluminescent blooms are a rapid increase in the population of light-emitting microorganisms (such as dinoflagellates or bacteria) in the water, reaching densities high enough that their collective light production becomes visibly detectable, often as glowing waves or water at night. In luminous marine bacteria, the evidence is relatively direct because light emission is tightly associated with luciferase-mediated metabolism and QS control. Studies have demonstrated that microplastic exposure can interfere with QS in A. fischeri (a marine bacterium) at sub-toxic concentrations (Gagné, Reference Gagné2017). Similarly, mechanically fragmented microplastics, produced by grinding larger plastic particles into smaller fragments, have been shown to alter bioluminescence patterns, reduce cell viability, and influence biofilm formation in P. leiognathi (a species of luminous bacteria), resulting in bioluminescence quenching (De Jesus et al., Reference De Jesus, Iqbal, Mundra and AlKendi2024). Beyond direct toxicity, plastics act as surfaces for plastisphere (human-made ecosystem consisting of microorganisms that colonise the surface of plastic debris in aquatic and terrestrial environments) formation and as vectors for sorbed contaminants, thereby altering microbial community structure and increasing exposure to co-stressors that can interfere with light-producing systems (Joo et al., Reference Joo, Liang, Kim, Byun and Choi2021; Du et al., Reference Du, Liu, Dong and Yin2022). Thus, plastic pollution is unlikely to affect bioluminescence through a single pathway. It acts through a combination of oxidative stress, reduced feeding and growth, membrane and organelle dysfunction, QS disruption and contaminant transfer, ultimately leading to weaker and less stable marine bioluminescent phenomena.

Such alterations may extend to the community scale, as bioluminescence plays an important role in structuring trophic interactions and shaping marine communities by influencing prey-predator interactions, camouflage, schooling, courtship and vertical ocean habitat use. In mesopelagic systems (~200 to 1,000 m), many fish and other organisms use bioluminescence for counterillumination, prey attraction and intraspecific signalling, while predators can also use bioluminescent cues to locate prey more efficiently (Vacquié-Garcia et al., Reference Vacquié-Garcia, Royer, Dragon, Viviant, Bailleul and Guinet2012; Paitio and Oba, Reference Paitio and Oba2024; Duchatelet and Dupont, Reference Duchatelet and Dupont2025). Because these light-mediated interactions contribute to aggregation patterns such as the clustering of organisms for feeding, mating and support energy transfer across the food web, any plastic-induced disruption of bioluminescent systems can directly influence the prevailing fisheries, particularly in the wake of recent interest in harnessing fisheries resources beyond the epipelagic zone (ocean surface to 200 m) (Gatto et al., Reference Gatto, Sadik-Zada, Özbek, Kieu and Huynh2023). The implications for fisheries become even more important under rapid climate change, which is already transforming deep-sea ecosystems and exacerbating the impacts of plastic pollution on deep-sea fauna (Levin and Le Bris, Reference Levin and Le Bris2015). Plastic debris in the sea surface layer can be redistributed by rising ocean temperature and altered circulation patterns (changes in ocean currents, mixing and sinking processes) (VishnuRadhan et al., Reference VishnuRadhan, Eldho and David2019; Haque and Fan, Reference Haque and Fan2023), thereby increasing its vertical transport of plastic to deep-sea habitats (da Fonseca and Gaylarde, Reference da Fonseca and Gaylarde2025) where it accumulates and persists for long periods. Climate-driven ocean deoxygenation (Limburg et al., Reference Limburg, Breitburg, Swaney and Jacinto2020), especially deep-sea deoxygenation (Ross et al., Reference Ross, Du Preez and Ianson2020), may increase the physiological vulnerability of deep-sea bioluminescent organisms, reducing their ability to cope with additional stressors, given the fundamental role of oxygen in marine bioluminescence. Increasing rate of ocean acidification (Findlay et al., Reference Findlay, Feely, Jiang, Pelletier and Bednaršek2025) can further impact bioluminescent calcifying species, including crustaceans, molluscs, deep-sea corals, sea pens and deep-sea brittle stars, making them more susceptible to damage and predation. Plastics can also act as vectors for pathogens and other pollutants (Amelia et al., Reference Amelia, Khalik, Ong, Shao, Pan and Bhubalan2021; Beans, Reference Beans2023) and transport them to deep-sea ecosystems through vertical transport (Chen et al., Reference Chen, Kane, Clare, Soutter, Mienis, Wogelius and Keavney2025; Rynek et al., Reference Rynek, Tekman, Veit-Köhler, Wagner, Reemtsma and Jahnke2025). In this context, vertical transport describes the downward movement of plastic particles and associated contaminants from surface waters into deeper ocean layers mainly through sinking and aggregation. Together, these compounding factors create cumulative and synergistic effects, intensifying the impact of plastic pollution on bioluminescence and thereby affecting deep-sea biodiversity and ecosystem functioning.

Although recent studies (Deng et al., Reference Deng, Fu, Su, Chen, Deng, Hu, Chen and Deng2025; Ferreria et al., Reference Ferreira, Schmidt, Justino, Fudge, Lucena-Frédou, Eduardo and Mincarone2026; Flores-Ocampo et al., Reference Flores-Ocampo, Armstrong-Altrin and Pérez-Alvarado2026) provide discrete evidence of the impacts of plastic pollution on deep-sea ecosystems, high-quality data and observations are essential to draw robust conclusions. However, the fragile nature of deep-sea organisms and the inaccessibility of those depths impose stringent observational constraints, further complicating the riddle of deep-sea plastic pollution. Most marine plastics originate from land sources (Guggisberg, Reference Guggisberg2024). Thus, global, regional and local perspectives on plastic waste management are required to scale up understanding of the causes and effects of plastic pollution in the deep sea. This can further aid in quantifying and deciphering the mechanisms of bioluminescence’s interaction with marine plastic pollution. The Deep-Ocean Observing Strategy (DOOS) and the Global Ocean Observing System (GOOS) (Levin et al., Reference Levin, Bett, Gates, Heimbach, Howe, Janssen, McCurdy, Ruhl, Snelgrove, Stocks, Bailey, Baumann-Pickering, Beaverson, Benfield, Booth, Carreiro-Silva, Colaço, Eblé, Fowler, Gjerde, Jones, Katsumata, Kelley, le Bris, Leonardi, Lejzerowicz, Macreadie, McLean, Meitz, Morato, Netburn, Pawlowski, Smith, Sun, Uchida, Vardaro, Venkatesan and Weller2019) should prioritise recognising the need for a comprehensive, holistic investigation and policy amendments regarding this less-fathomed realm’s interaction with plastic pollution.

Our understanding of the deep ocean is progressing in a promising direction through the global network of experts such as the Deep-Ocean Stewardship Initiative (DOSI), which integrates science, technology, policy, law and economics to advise on ecosystem-based management of resource use in the deep ocean, and on strategies to maintain the integrity of deep-ocean ecosystems within and beyond national jurisdiction (UN, 2016). DOSI is moving beyond “business-as-usual” to a coordinated, community-led, worldwide effort with the potential to increase our understanding of deep-sea marine life at an unprecedented scale, keeping in mind the knowledge requirements of international policy processes (Hilário et al., Reference Hilário, Howell and Baker2025). The Global Partnership on Plastic Pollution and Marine Litter and the UNEP Plastics Initiative should consider recognising the impacts of plastic pollution on deep-sea bioluminescence as a priority research area. Such attention is warranted because the deep sea, although still underexplored, represents a critical component of the Earth system, contributing substantially to global ecosystem functioning and climate regulation. Accordingly, there is an urgent need to expand our understanding of deep-sea processes and of how anthropogenic stressors, including plastic pollution, alter these fragile and poorly resolved biological systems (Sander et al., Reference Sander, Tamburini, Gollner, Guilloux, Pape, Hoving, Leroux, Rovere, Semedo, Danovaro and Narayanaswamy2025). Although 66% of the entire planet is deep ocean (≥ 200 m), a recent quantification of the deep-sea floor shows that the visually observed area is less than 0.001% (Bell et al., Reference Bell, Johannes, Kennedy and Poulton2025). This limited observational coverage is especially concerning in relation to plastic pollution because a large proportion of the plastics entering the ocean are no longer accounted for in surface waters and are transported downward, ultimately accumulating in deep-sea sediments or remaining suspended in the deep-water column (Frederick, Reference Frederick2020).

The fate of bioluminescent organisms at these depths due to the influx of plastic pollutants and their derivatives, such as chemical leachates, is largely unknown. Considering that the deep sea is the largest biome on Earth, accounting for over 90% of ocean volume and covering more than 90% of the seafloor, and that bioluminescence serves as a fundamental survival strategy in this perpetually dark environment, there is a pressing need to assess how plastic pollution modifies these fragile luminous systems. Research community and agencies should encourage the prioritisation of bioluminescence-based indicators as sensitive, early-warning tools for detecting the ecological impacts of plastic pollution in the deep-sea environment. Incorporating such indicators into monitoring frameworks (Chatzievangelou et al., Reference Chatzievangelou, Bahamon, Martini, Del Rio, Riccobene, Tangherlini, Danovaro, De Leo, Pirenne and Aguzzi2021) can improve the detection of sub-lethal stress and provide more accurate assessments of ecosystem health in deep-sea and low-light habitats. Addressing the interactions and impacts of plastic pollution on marine bioluminescence can help advance the mandates of Sustainable Development Goal 14 and charter strategies beyond 2030. Greater scientific attention and policy recognition are therefore required before the ecological integrity of deep-ocean bioluminescence is further compromised.