Must we stop littering plastics to avoid dolphins and turtles die? Yes.
Should we try our best to buy yoghurt in bulk instead of dozens of small containers? Yes.
It happens that microscopic pieces absorb pollutants in seawater such as PCBs, DDT and PAHs. Animals eat these and it goes up the food chain to large fish humans eat.
Many species including turtles, birds, fish, & mammals eat larger pieces and basically wind up starving to death because there is no room for food in their stomachs. 80% of this comes from shipping, 20% from land.
Please try not to consume plastics, try to send whatever plastic you use to recycling facilities and try to pass the message.