Across marine environments, plastic is often eaten rather than avoided. Sea turtles mistake bags for jellyfish; seabirds pick bright fragments and feed them to chicks; fish and invertebrates ingest microplastics suspended in water or settled in sediments.

This article explains the mechanisms through which plastic ingestion disrupts digestion and feeding, how harmful substances accumulate over time, and why acting before waste reaches the sea is essential.

Mistaking plastic for food

Many species use vision and smell to find prey. Floating bags, films, and foams mimic natural cues—jellyfish for turtles, fish eggs for seabirds, zooplankton-like particles for filter feeders. In turbid waters or at night, shape and contrast override caution, leading to ingestion. Once swallowed, plastics can lodge in the oesophagus or stomach, abrade tissues, and reduce the space available for real food. The problem spans sizes: from macroplastics that block the gut to microplastics that pass but still interact with tissues and vital functions.

False satiety

Rigid fragments, caps, lighters, and monofilaments tangle and compact into masses that hinder digestion. Animals feel “full” but receive no energy, entering a starvation spiral. Even partial obstruction slows gut transit, reducing assimilation of nutrients and water. Internal tissues may become irritated or damaged, raising the risk of infections; compromised individuals struggle to dive, evade predators, or migrate. At a broader scale, these effects reduce survival and reproductive capacity: in colonies and schools, harm to individual organisms translates into impacts on the entire population.

Chemical exposure

Plastics are not inert materials: they contain chemical additives—such as plasticizers, stabilizers, and flame retardants—and once in the sea, they also tend to bind other pollutants present in the environment. During residence in the gut, some additives and contaminants can transfer to tissues, adding to the animal’s chemical burden. The extent of this transfer varies depending on the type of plastic, the size of the fragments, and the animal’s internal conditions, but the mechanism is clear: ingesting plastic increases exposure to potentially harmful compounds. These effects are particularly critical during the most sensitive life stages—eggs, larvae, and juveniles—where even small disruptions can affect growth, development, and survival.

Energy drain

Searching for food with a compromised gut costs time and energy. Even without causing immediate death, plastic ingestion slows growth and weakens animals, altering how they swim, where they feed, and how they interact with predators. Seabirds that repeatedly regurgitate plastic to chicks show reduced provisioning of nutritious prey; fish with microplastics in the gut spend more time feeding to compensate, increasing exposure to additional hazards. Over time, these energetic penalties depress individual fitness and, cumulatively, population resilience.

Life stages at risk

Early life stages encounter plastics in nursery habitats—estuaries, bays, and coastal fronts—where marine litter concentrates. Eggs and larvae are sensitive to both physical and chemical stress; juveniles are exploratory feeders and ingest fragments readily. Long-lived species accumulate risks across decades. On the seafloor, microplastics mixed into sediments are ingested by detritus-feeding organisms and then move up the food chain; in open waters, floating fragments and fibers are taken up by filter feeders and plankton-feeding species. Exposure pathways differ, but the outcome converges: a progressive decline in organism health and ecological balance.

Plastic and microplastics do not remain an isolated problem within a single species. They move through marine food webs, starting with plankton and small fish and gradually working their way up the food chain—eventually reaching us. This is why Ogyre takes action on two complementary fronts: removing waste directly from the sea in collaboration with local fishers, and intercepting ocean-bound waste along coastal areas before it spreads into marine environments. Acting early—before plastic reaches the ocean—is key to protecting ecosystems, food systems, and human health.

Plastic ingestion is not an accidental event, but a predictable outcome of plastic spreading through the environments where animals feed and interact with their ecosystems. The mechanisms are well understood: plastic is mistaken for prey, causes physical blockages, introduces harmful substances, and increases energy expenditure, with effects that begin at the level of individual organisms and extend to entire populations.

For this reason, action is needed both to remove waste already present in the sea and to prevent it from dispersing in the first place. Recovery at sea, interception along coastal areas, and responsible end-of-life management—supported by transparent tracking systems—reduce the risk of waste damaging marine ecosystems and the biodiversity they support, helping preserve the Ocean’s capacity to sustain life.

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