Life can be abundant, if nutrients and sunlight are plentiful.
Most animals have low-energy tissues and sluggish lifestyles to cope with low food energy, since no algae can grow, and life gets sparser the deeper one goes. Bacteria, salps, shrimp, jellys, squid and fish are typical. Examples of animals are shrimp and anglerfish, though no fish has ever been seen or caught below 8,000m. The surface is mostly mud and organic ooze. Most life here must also cope with low food supply, and again most food chains start with detritus and bacteria.