The plastic pollution in the oceans is harming larger species which eat colorful pieces but can't digest it. The plastic collects in the animals digestive system and they eventually starve. More recently it was discovered that some microbes may also be absorbing plastic and are being harmed. The risk to ocean and human life is in the loss of oxygen that the microbes would otherwise be adding to the atmosphere. The photosynthetic bacteria would also be part of the food supply for other marine life. Read more: Plastic Pollution Harms Bacteria that Produce 10 Percent of Oxygen we Breathe, (The Independent).
Ocean microbes make as much as half of the oxygen in our atmosphere. Trees in the Amazon rain-forest and elsewhere also are important oxygen producers.
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