Entanglement is one of the major biological impacts of marine debris. I also feel like it is the most well known, likely because of the sensationalized but gruesome photos that come from such wildlife/trash interactions.
Entanglement is prevalent across all species, but is must well studied in the turtles (100% of species), seabirds (50% of species), and marine mammals (66% of species). Only recently have studies looked at entanglement in fish and marine invertebrates, but given the quantities of trash, and the diversity of each of these groups, it seems likely that both are being heavily impacted.
Entanglement can cause immediate death by starvation or drowning. It can also lead to reduced ability to swim, forage, and feed, which may lead to eventual starvation. As an animal grows, entangling plastics can cut into and injure that animal, as well as strangle digestive tracts, or other important organs.
I am always interested when a marine litter paper comes out in regards to sharks. They are not a group that gets much attention in marine litter literature. They have other major human threats (like shark fishing and finning) that are threatening their populations, but they are effected nevertheless.