Science & Society
Microplastics: No Small Problem for Filter-Feeding Megafauna

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Microplastic pollution can impact filter-feeding marine megafauna, namely mobulid rays, filter-feeding sharks, and baleen whales. Emerging research on these flagship species highlights potential exposure to microplastic contamination and plastic-associated toxins. Research and its wide communication are needed to understand the magnitude of the issue and improve marine stewardship.

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Susceptibility to Microplastic Ingestion

Data-calibrated models have been developed to estimate the distribution of microplastics at the sea surface layer [3], with predictions of microplastic pollution hotspots, which include five oceanic gyres, semienclosed basins (Gulf of Mexico, Mediterranean Sea, and Bay of Bengal) and biodiversity hotspots (Coral Triangle). In addition to these five oceanic gyres, four key regions stand out as high-priority areas for research and intervention based on our assessment of overlap between regions

Effects of Microplastic Ingestion

The effects of ingesting indigestible particles include blocking adequate nutrient absorption and causing mechanical damage to the digestive tract. Microplastics can also harbor high levels of toxins and persistent organic pollutants (POPs) (Box 1), and introduce these toxins to organisms via ingestion 2, 4 (Box 1, Figure IC). These toxins can bioaccumulate over decades in long-lived filter-feeding megafauna, leading to a disruption of biological processes (e.g., endocrine disruption [4]), and

Future Directions

Studies have yet to confirm directly that filter-feeding megafauna are exposed to POPs and other plastic-associated toxins and additives through microplastic ingestion. Gaining direct evidence through conventional methods used to study diet, such as stomach-content analysis or collecting egested material, relies on opportunistic observations and, thus, is not suitable for threatened marine megafauna. However, as the analytical approaches available to detect toxins continue to increase, it is

Value of Focusing on Megafauna

Many filter-feeding megafauna are charismatic and iconic species that can serve as flagship species for marine conservation. Filter-feeding megafauna are also ideal umbrella species candidates [9] due to their wide habitat ranges, including coastal and pelagic environments. While umbrella species are useful for directing intervention strategies that cascade through marine ecosystems for the benefit of the systems as a whole, flagship species can provide a mechanism for communicating awareness

Acknowledgments

This work benefited from support from the Australian Postgraduate Award & Murdoch International Top Up For International Postgraduate Research Studentship Award (ESG), and research funding by the Ocean Park Conservation Foundation (ESG, ADM), Fortuna Foundation (ESG), the PADI Foundation (ESG), Idea Wild (ESG), the Marine Megafauna Foundation and private donors (ESG, ADM). The research field discussed in this work benefited from the technical and scientific research support provided by Dr.

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