Written by the Fiveable Content Team • Last updated August 2025
Written by the Fiveable Content Team • Last updated August 2025
Definition
The pelagic realm is the open water area of an ocean or lake, not associated with the shore or bottom. It includes all water column habitats from the surface to the deepest parts of these bodies of water.
The pelagic realm is divided into different zones based on depth and light penetration, including epipelagic, mesopelagic, bathypelagic, abyssopelagic, and hadopelagic zones.
Organisms in the pelagic realm are adapted to living in open water with no solid substrate for attachment.
The epipelagic zone (surface to about 200 meters) is where photosynthesis occurs due to sufficient sunlight penetration.
Pelagic organisms include plankton, nekton (like fish and squid), and larger marine animals such as whales.
Nutrient levels in the pelagic realm can vary greatly; upwelling areas bring nutrient-rich waters to the surface, supporting high productivity.
Related terms
Benthic Zone: The ecological region at the lowest level of a body of water including the sediment surface and sub-surface layers.
Plankton: Small and microscopic organisms drifting or floating in the sea or freshwater, crucial as a food source in aquatic ecosystems.
Nekton: Aquatic animals that can swim and move independently of water currents, such as fish, squid, and marine mammals.