Microplastics in the oceans: An invisible threat to the marine ecosystem

Veronica Rocco 21 Nov 2023

In recent years, the escalating global concern about plastic pollution has shifted the spotlight onto a microscopic adversary: microplastics. These tiny particles, with a diameter less than five millimeters, pose a significant and often invisible threat to marine ecosystems. As researchers delve into the intricate
web of marine life, alarming evidence emerges of the infiltration of microplastics into organisms across the entire oceanic spectrum.
Microplastics originate from various sources, including the degradation of larger plastic debris, microbeads in personal care products, and the shedding of synthetic fibers from textiles. These microscopic particles infiltrate oceans worldwide, propelled by ocean currents and winds. Their pervasiveness has turned them into silent invaders, spreading through marine habitats from the ocean surface to the seafloor.

Marine organisms, from microscopic plankton to large mammals inhabiting our oceans, are unwitting victims of this plastic invasion. The process of ingesting microplastics is complex. Filter-feeding organisms, such as bivalves and some plankton species, directly ingest microplastics from the surrounding water during feeding. Larger predators consume smaller organisms that have already ingested microplastics, leading to the biomagnification of these particles along the food chain.
The consequences of microplastic ingestion are profound and intricate. In filter feeders, ingestion can result in reduced feeding efficiency and compromised health. In larger organisms, effects extend to compromised digestive processes, the accumulation of toxins present in plastics, and even damage to internal organs.

Recent studies, including those conducted under the "i-plastic" project by the Institute of Environmental Science and Technology at the Universitat Autònoma de Barcelona (ICTA-UAB), have revealed that microplastics are not just physical hazards; they can also act as carriers of toxic substances. According to the collected data, 85% of mussels and 53% of oysters analyzed in the project had ingested microplastics. In estuary-dependent marine fish, such as mullets and breams, the percentage was 75%. In coastal regions influenced by estuarine runoff, 86% of European hake and 85% of Norwegian lobster contained microplastics or synthetic microfibers in their stomachs.
The "i-plastic" project has also highlighted that all aquatic species in the estuaries flowing into the Mediterranean Sea and the Atlantic Ocean are contaminated by microplastics. Mollusks are the most affected due to their ability to filter water.

For instance, a mussel can filter about 1.5 liters of water per hour at a temperature of around 14°C. Similarly, the European oyster can filter from 12 to 15 liters at a similar temperature, while its American counterpart surpasses 18 liters per hour when kept at 20°C. This pollution poses a threat to aquatic ecosystems, with potential adverse effects on the food chain, the fishing industry, and human health. Addressing the widespread issue of microplastics in marine organisms requires a multifaceted approach. Strategies include reducing the production and consumption of plastic, enhancing waste management systems to prevent plastic dispersion into oceans, and developing alternative materials that are less harmful to the environment. Additionally, increased public awareness and education are vital to foster responsible consumption habits. From regulatory changes to individual choices, every action contributes to steering the course towards a plastic-free future. Only through collective commitment can we hope to protect the diverse and fragile ecosystems that populate our oceans and preserve the countless species that inhabit them.

Researchers suggest that bioremediation, an approach based on using living organisms to rid water of pollutants, emerges as one of the few practical strategies to counter the widespread presence of microplastics in coastal marine ecosystems. Laboratory studies have clearly demonstrated that various filter-feeding communities, represented by different species, can effectively remove almost 90% of microplastics from the surrounding waters. This innovative approach, based on the natural ability of certain organisms to absorb and filter harmful particles, offers a promising outlook for mitigating the negative impacts of microplastics on the marine environment.

10 FACTS on microplastics and nanoplastics in estuarine environments

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Scienceonline, Autorizzazione del Tribunale di Roma 228/2006 del 29/05/06
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