Practice question

Plastic sheets, lines, and nets entangled on coral reefs can cover living tissue and restrict water movement. Shading reduces light available to photosynthetic symbiotic algae, while reduced circulation limits oxygen exchange and waste removal, especially at night or within boundary layers. Abrasion also wounds tissue. These stresses make light and oxygen deprivation plausible consequences, not enhanced photosynthesis, fertilisation, or reproduction. Standardised sampling and contamination controls are essential because airborne fibres can enter samples during collection and laboratory processing. Particle size, shape, polymer type, weathering state, and associated chemicals all influence uptake and biological response, so microplastics are not a uniform toxicant. Laboratory effects must be interpreted alongside environmentally realistic concentrations, while field detection demonstrates exposure but does not alone prove causation. Prevention requires reducing unnecessary plastic use, improving collection and recycling, controlling lost fishing gear, and limiting releases of fibres and tyre-wear particles. Because conventional polymers persist, fragmentation redistributes plastic into smaller pieces rather than removing its mass from the ecosystem.