Richard Sempéré

Microplastics (MPs) are now widespread in marine environments, yet knowledge is still lacking regarding the contribution of common single-use items to marine MP contamination. Among these items, cigarette butts (CBs) and disposable face masks (DFMs) are globally pervasive plastic wastes, yet their microplastic release under environmentally relevant marine conditions remains poorly quantified. In this study, CBs and DFMs were incubated in natural seawater under laboratory-controlled conditions for 67 days. MP release was monitored under both biotic and abiotic conditions to assess microbial influence on fragmentation dynamics. MP generation showed contrasting responses to microbial activity depending on polymer type. CBs released more MPs under abiotic conditions (15 227 ± 7 190 MPs CB-1), whereas DFMs exhibited greater release under biotic conditions (40 767 ± 7 197 MPs DFM-1), indicating that microbial activity reduced MP accumulation from cellulose acetate-based materials while enhancing fragmentation of polypropylene-based materials. The MPs emitted consisted predominantly of fibers (~85%) and fragments (~15%), with modified cellulose acetate (95%) dominating CB-derived particles and polypropylene (89%) dominating DFM-derived particles. Our global-scale estimates indicate that degradation of CBs (10 quadrillion MPs y-1; 62 000 tons of cellulose acetate MPs y-1) and DFMs (15.9 trillion MPs y-1; 3 800 tons of polypropylene MPs y-1) could release substantial quantities of MPs annually into coastal marine environments, posing significant ecological risks with potential implications for marine ecosystem integrity and human exposure.

Tire particles can enter the marine environment e.g. through direct discharge of road runoff, sewage systems or riverine inputs. Their fate in marine waters remains largely unknown, though the deep sea could be a final sink as for other marine litter. To simulate these conditions, we investigated in laboratory-controlled conditions the effects of high-hydrostatic pressure [20 MPa] vs atmospheric pressure [0.1 MPa] on the leaching of 17 organic compounds from cryo-milled tire tread particles (μm sized) and crumb rubber particles (mm sized) into natural seawater. We monitored the abundance of heterotrophic prokaryotes in the leachates over the 14 day exposure period under biotic conditions. Abiotic controls were employed to delineate the influence of prokaryotes on the fate of leached chemicals. Our results showed leaching of dissolved organic carbon and target chemicals under all experimental conditions, with higher concentrations of certain target chemicals under high-hydrostatic pressure conditions (e.g., 1,3-diphenylguanidine [DPG]: max. 703 (20 MPa) vs 119 μg/L (0.1 MPa) from cryo-milled tire tread particles under biotic conditions). Under abiotic conditions leaching was weaker for DPG and other chemicals, with contrasting trends for chemicals prone to biotransformation. In crumb rubber leachates chemical concentrations increased with time, but showed no significant differences between biotic/abiotic or high-hydrostatic/atmospheric pressure conditions. Prokaryotic abundance increased in all samples containing tire particles compared to seawater controls, indicating the use of the rubber and/or leached chemicals as an energy source.

Plastic waste in the environment gradually degrades into microplastics, while organic additives within these plastics, can leach out over time during plastic aging. Each year, approximately 5.4 trillion cigarettes are produced, leading to the disposal of 4.5 trillion of cigarette butts worldwide. Similarly, with mask production potentially reaching 34.5 billion units annually, as observed in 2022 during the pandemic, and 10-20% of plastic waste being inadequately managed globally—whether left uncollected, improperly disposed of, or released into natural environments—it’s estimated that between 0.69 and 1.04 billion masks may end up in marine ecosystems each year. Yet, the environmental impact of these plastics, especially in marine ecosystems covering over 70% of the Earth’s surface, is still poorly understood.In this study cigarette butts and face masks, were incubated in natural seawater under laboratory-controlled conditions for 80 days. The generation of microplastics and the leaching of toxic organic additives, such as phthalates (PAEs) and organophosphate esters (OPEs), from these plastic items into the dissolved phase were closely monitored. Changes were tracked using LDIR for microplastics and GC/MS for additives, with bacterial conditions (biotic and abiotic) varied throughout the experiment. Our results showed that polypropylene (98.5%) was the primary polymer released from face masks, while modified cellulose acetate (91.5%) was predominant in cigarette butts. We found that that a single cigarette butt releases approximately 590 ± 310 microplastic particles (n = 6) per litter, while a single face mask contributes around 1 500 ± 1 000 particles into seawater (n = 6). Additionally, our findings revealed that these microplastic debris types (cigarette butts and masks) were composed of around 20% fibers and 80% fragments.Our results also indicated that both cigarette butts and face masks released significant amounts of PAEs followed by OPEs into the surrounding seawater during the first month. Di-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DnBP) were the primary PAEs leached from face masks, accounting for 31% and 21%, respectively, of the total PAEs released. In cigarette butts, diethyl phthalate (DEP) was the dominant PAE at 57%, followed by di-isobutyl phthalate (DiBP) at 11%. In both materials, 2-ethylhexyl diphenyl phosphate (EHDP) was the main OPE detected, contributing 19% and 18%, respectively. Finally, our results demonstrated that bacterial exposure had minimal impact on the average concentrations of additives released.

Environmental challenges in the marine environment, such as pollution, habitat degradation, overexploitation, natural hazard and impacts of climate change, are intrinsically complex and involve interacting natural and human factors. Therefore, interdisciplinarity is necessary to address these challenges, as it allows for a more comprehensive understanding of the interactions between human societies and marine ecosystems. In this perspective, Social Sciences and Humanities (SSH) provide crucial insights into how communities perceive, value, and impact ocean environments, thereby fostering more inclusive and effective conservation strategies. This communication explores the importance of this interdisciplinary approach and highlights various international initiatives, and those of Ocean Sciences Institute (OCEAN, Aix-Marseille University) as a telling example in bridging the gap between marine science and SSH. In recent decades, Institutions and Universities worldwide have been increasingly committed to embedding interdisciplinarity in marine sciences, including students and researchers training to address global marine issues more holistically and effectively. Our experience at the OCEAN Institute indicated that such structure can sustain interdisciplinary research and education projects involved in studying socio-ecological systems. By examining both ecological dynamics and social dimensions, OCEAN aims to facilitates a deeper understanding of human-environment interactions and community engagement in conservation efforts. For instance, OCEAN has financed since 2021 various research programs that successfully integrated natural sciences and SSH. Such projects intersect, among others, marine pollution and history, social geography and chemistry, ecology and environmental psychology, or education program combining marine science and environmental law. Regarding educational challenges, we found that OCEAN’s interdisciplinary summer schools dealing with marine protected areas or plastic pollution may efficiently prepare future researchers and professional to navigate both natural and social sciences, enhancing problem-solving skills and promoting a transversal approach to marine conservation. In this communication, we provide an overview and feedback on how university institutes can mobilize different disciplines, and a comparison of this experience with initiatives carried out on an international scale. We also discuss this experience by providing a critical dimension on the successes and obstacles encountered. We propose that the evaluation of the success of a project should focus on how interdisciplinarity has enabled to shed light on a research question by bridging knowledge gaps, and/or by adding an applied dimension to the research results, particularly when addressed to stakeholders (transdisciplinarity). Scientific interdisciplinarity also faces conceptual and methodological challenges when combining divergent paradigms and methods. Interdisciplinary work may struggle to fit within the traditional valuation system of scientific research. As a result, such an approach may be time-consuming and challenging to manage, leading marine scientists to consider SSH as subsidiary rather than a core dimension of research projects. Hence the importance of an institutional support such as the one provided by Aix-Marseille University through the Mission for Interdisciplinarity, which has developed an original tool for designing and carrying out an interdisciplinary research project. In this communication, we propose simple guidelines based on our real “learn by doing” experience to encourage institutions and scientists to adopt a reflexive approach to their practices, embracing collaboration, open communication, and flexible methodologies.

In spring 2016, the temporal evolution of organic carbon and carbohydrate concentrations was monitored in and under the sea ice during the microalgal–ice algae and subsequent phytoplankton–productive periods in western Baffin Bay (Canadian Arctic). The results showed that total carbohydrates (TCHO) closely followed total organic carbon, with the highest concentrations observed in the bottom-most few centimeters of sea ice (mean 186 µM C, n = 22). Such organic matter accumulation likely comprises labile organic matter, reflecting the presence of a concentrated algal biomass, as suggested by the significant correlation between TCHO and chlorophyll a ( r = 0.625, p < 0.05). Compositionally, the bottom-most ice core was dominated by monosaccharides, which accounted for 38%–90% of TCHO, and were probably the result of an important in situ exoenzymatic activity of polysaccharides. Conversely, total dissolved carbohydrates in the underlying water did not follow dissolved organic carbon patterns and were dominated by dissolved polysaccharides, indicating that carbohydrates may have multiple sources, not solely from microalgae in either pelagic or sympagic (ice-associated) environments. Overall, our results suggest significant differences in carbohydrate dynamics between sea ice and the under-ice water, despite the strong coupling of these systems during ice melt, highlighting the complexity of the processes occurring within these ecosystems.

The Green Edge project was designed to investigate the onset, life, and fate of a phytoplankton spring bloom (PSB) in the Arctic Ocean. The lengthening of the ice-free period and the warming of seawater, amongst other factors, have induced major changes in Arctic Ocean biology over the last decades. Because the PSB is at the base of the Arctic Ocean food chain, it is crucial to understand how changes in the Arctic environment will affect it. Green Edge was a large multidisciplinary, collaborative project bringing researchers and technicians from 28 different institutions in seven countries together, aiming at understanding these changes and their impacts on the future. The fieldwork for the Green Edge project took place over two years (2015 and 2016) and was carried out from both an ice camp and a research vessel in Baffin Bay, in the Canadian Arctic. This paper describes the sampling strategy and the dataset obtained from the research cruise, which took place aboard the Canadian Coast Guard ship (CCGS) Amundsen in late spring and early summer 2016. The sampling strategy was designed around the repetitive, perpendicular crossing of the marginal ice zone (MIZ), using not only ship-based station discrete sampling but also high-resolution measurements from autonomous platforms (Gliders, BGC-Argo floats …) and under-way monitoring systems. The dataset is available at https://doi.org/10.17882/86417 (Bruyant et al., 2022).