The pelagic oceanic biome is physically characterized by the makeup and behavior of the waters. The pelagic zone is a salt-water biome, making it completely distinct from the various freshwater biomes. The water in the pelagic zone is generally cold, though it is crisscrossed throughout with both warm and cold ocean currents. Tides and waves are also characteristics of the pelagic zone, which discern the pelagic zone from the more stable zones that lie below it: the benthic and abyssal zones.
The plants and animals of the pelagic zone form a food chain that is distinct among all biomes. At the bottom of the food chain are algae and surface seaweeds that sustain animals such as plankton and small fish. The pelagic zone is also home to larger fish such as sharks and tuna, as well as various species of aquatic mammals such as dolphins and whales. These larger life forms, both herbivorous and carnivorous, form the upper echelon of the pelagic zone food chain. These feed on the smaller fish and plankton that populate the pelagic zone to form a food chain that is significantly different from those of the other marine biomes.
Few people would ever equate the abundantly populous and decidedly wet open ocean with a desert, but the pelagic zone is actually quite similar to a desert in terms of its energy absorbed via photosynthesis. This process of energy absorption is called primary productivity. The most productive ecosystems are swamplands, while the driest deserts and the pelagic zone rank among the least productive. The production that does occur in the pelagic zone is mainly the work of microscopic organisms such as bacteria and algae.
