Plastics came into mainstream use only after World War II, but today they can be found in the remotest places on earth from pole to pole. It is the primary source of marine pollution, about 60% of plastic ever produced has already ended up in the oceans, that is about 85-150 million metric tonnes of plastic, floating around in oceans.
Marine animals are the ones most directly affected by the presence of too much plastic in the ocean, many animals ingest microplastic which proves fatal for the ghost fishing nets left in the seas trap fishes big and small entangling them to death, plastics also cloud sunlight and sometimes mask whole colonies of corals depriving them of oxygen and killing them, they decay of these organisms consumes oxygen in the water further driving the deoxygenation which is already being accelerated by the rising temperature of ocean water.
The consumption of microplastics by marine animals also puts humans in the line of danger, according to WWF 20% of canned sardines have microplastics in them, nano plastics have also been coming to light in recent years, they have been found to cross the blood-brain barrier of marine organisms altering feeding and mating behaviors putting the whole ecosystems at risk.