This is clearly emphasized, among others, by a catastrophic forecast officially released some years ago by the World Economic Forum, which literally states that "(there will be) more plastic than fish in marine ecosystems by the year 2050" (World Economic Forum Report, 2016).
Within such an alarming scenario, adequate attention should be also paid to the role of MNPs as powerful "attractors and concentrators" for a large amount of persistent environmental pollutants (PEPs), including heavy metals like methylmercury (MeHg) and organic xenobiotics such as polychlorinated biphenyls (PCBs), dioxins, polycyclic aromatic hydrocarbons (PAHs) and perfluorinated alkylated substances (PFAS) (1). Indeed, this could exert a very destabilizing (and yet overlooked) impact especially on filter-feeding organisms, including large vertebrates like whales, whose position as "secondary consumers" within the marine food web would consequently undergo a "sudden" escalation, with special reference to those sea and ocean ecosystems characterized by a prominent PEP-loaded MNP contamination, such as the Mediterranean Sea basin (2).
By doing so, in fact, whales would end up mimicking the feeding behaviour of "apex predators" like dolphins, orcas and polar bears (3). Under similar circumstances, PEP exposure's magnitude (and its related bioaccumulation and biomagnification processes) following MNP ingestion may result in severe adverse health effects for whales, given the well-known immunotoxic, neurotoxic and endocrine-disrupting roles played by several PEP categories and, synergistically, by their mixtures (4). This scenario is made even more alarming by the well-established role of MNPs as carriers of microbial pathogens impacting cetaceans' health and conservation across the globe, including also antibiotic-resistant bacteria largely benefitting from the horizontal transfer of genes involved in antimicrobial resistance between the bacterial communities colonizing MNP substrates (5).
Within this challenging and scientifically intriguing context, a "One Health, One Earth, One Ocean"-centred approach would undoubtedly represent the best strategy to properly assess and, thereafter, counteract the detrimental effects of PEP-loaded MNPs on the increasingly threatened health and conservation status of free-ranging whales and dolphins, our most reliable planetary seas' and oceans' "sentinels"!
References
1. Xiang Y., et al. Microplastics and environmental pollutants: Key interaction and toxicology in aquatic and soil environments. J. Hazard. Mater. 2022; 422:126843.
2. Concato M., et al. Detection of anthropogenic fibres in marine organisms: Knowledge gaps and methodological issues. Mar. Pollut. Bull. 2023; 191:114949. doi: 10.1016/j.marpolbul.2023.
3. Berta A., Kienle S.S., Lanzetti A. Evolution: Killer whale bites and appetites. Curr. Biol. 2022; 32(8):R375-R377. doi: 10.1016/j.cub.2022.03.001.
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