Definition of Microplastics
Microplastics are synthetic polymer particles smaller than 5 millimeters in diameter, originating from the fragmentation of larger plastic debris or manufactured directly as microbeads in products like cosmetics. These particles persist in the environment due to their durability and resistance to natural degradation, entering oceans primarily through rivers, wastewater, and coastal litter.
Key Sources and Types
Microplastics are classified into primary types, such as microbeads intentionally added to exfoliants and cleaning products, and secondary types formed by the breakdown of macroplastics like bottles and bags through weathering, UV exposure, and mechanical action. Common sources include textile fibers from synthetic clothing washed into waterways, tire abrasion on roads, and industrial pellets lost during manufacturing.
Practical Example in Ocean Ecosystems
In the North Pacific Gyre, known as the Great Pacific Garbage Patch, microplastics accumulate in high concentrations, where they are ingested by zooplankton like krill. These organisms mistake the particles for food, leading to bioaccumulation as the plastics move up the food chain to fish, seabirds, and marine mammals, as observed in studies showing plastic fibers in the stomachs of over 90% of sampled seabirds.
Environmental Impacts on Oceans
Microplastics disrupt ocean ecosystems by causing physical harm through ingestion, leading to blockages, malnutrition, and reduced reproductive success in marine species. They also adsorb toxic chemicals like PCBs and heavy metals, facilitating their transfer through the food web and posing risks to human health via seafood consumption. Additionally, they alter habitats by smothering coral reefs and benthic communities, contributing to biodiversity loss and long-term ecological imbalance.