For the first time, jellyfish have been observed ingesting microplastic fragments — a discovery that has highlighted how plastic is even more widespread in the marine food web than previously thought.
That plastic is a scourge for marine ecosystems and the creatures that inhabit them is certainly nothing new. We know, for example, that around 90 per cent of seabirds worldwide have plastic waste in their stomachs, or that microplastics threaten the survival of megafauna such as baleen whales, whale sharks, basking sharks and manta rays. What we did not know, however, is that this human-produced waste is also found at the bottom of the food chain — it has now been discovered that even jellyfish eat plastic.
This was revealed by the study Episodic records of jellyfish ingestion of plastic items reveal a novel pathway for trophic transference of marine litter, published in Scientific Reports, which highlighted how plastic is even more widespread in the marine food web than previously thought and raised further concern about the impact on aquatic wildlife. Off the island of Ponza, researchers observed for the first time a jellyfish species — the mauve stinger (Pelagia noctiluca) — ingesting microplastic fragments.
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Invertebrates represent the most abundant component of marine biodiversity, the study notes — conducted by a team of researchers from Italian and Russian scientific institutions and universities — yet to date the ingestion of marine litter has been documented for only a handful of species. The number of studies showing the impact of litter on marine organisms is, however, growing; plastic ingestion has currently been documented in 233 marine vertebrates.
The scientists, led by Armando Macali of the Centro ittiogenico sperimentale marino (Cismar) and Elisa Begami of the Dipartimento scienze fisiche, della Terra e dell'ambiente at the University of Siena, focused their research on the mauve stinger, the most abundant jellyfish species in the Mediterranean Sea. The mauve stinger is considered an opportunistic predator, feeding on a wide range of zooplankton. This species represents the primary food source for many large pelagic predators, such as the ocean sunfish, sea turtles, Atlantic bluefin tuna and swordfish. Jellyfish also play a valuable ecosystemic role, being capable of sequestering large quantities of carbon. The researchers therefore believe that any impact of marine litter on this species could have consequences for its predators and for the survival of marine ecosystems.
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During exploration of the waters around the Lazio island, carried out in September 2016, researchers observed jellyfish swimming among numerous pieces of waste of various sizes, colours, shapes and types. Some of these materials were found trapped between the oral lobes of the jellyfish or held within their bell. These would be the first observations of this phenomenon, according to the study's authors. Of the twenty mauve stinger specimens analysed, four contained plastic debris inside their gastrovascular cavity.
Jellyfish would have ingested plastic fragments and microplastics because, just as happens with other animals, they would have mistaken them for food or been attracted by the aromatic organic compounds present on the surface of the plastic. The researchers therefore hypothesise that jellyfish, which are prey to numerous species, may act as a vector for plastic along marine trophic cascades, exponentially increasing the danger to aquatic wildlife and, naturally, to humans who in turn feed on many species that eat plastic-laden jellyfish.