The Marine Biodiversity Guide
Explore the major organisms, habitats and ecological relationships found in marine environments.
A field guide to life in the ocean: how depth shapes marine habitats, which groups of organisms live there, and how to explore marine species and ecosystems in Biosphere.
- Organization
- Biosphere
- Type
- field guide
- Format
- guide
- Audience
- general, students
- Topics
- oceans, coral reefs, wildlife, biodiversity
Key information
- Coverage: Open ocean, deep sea, coral reefs, polar seas
- Level: Introductory
The ocean is the largest living space on Earth. Light, temperature, pressure and nutrients change with depth and distance from the coast, and each combination supports a different community of life.
The ocean by depth
| Zone | Approximate depth | Conditions |
|---|---|---|
| Sunlight zone (epipelagic) | 0–200 m | Enough light for photosynthesis; most marine life lives here |
| Twilight zone (mesopelagic) | 200–1,000 m | Faint light; many animals migrate up at night to feed |
| Midnight zone (bathypelagic) | 1,000–4,000 m | No sunlight; some animals produce their own light |
| Abyssal zone | 4,000–6,000 m | Near-freezing water and very high pressure |
| Hadal zone | Below 6,000 m | Deep ocean trenches |
Who lives there
- Plankton — microscopic algae and tiny animals that drift with the currents and support almost every marine food web.
- Marine mammals — such as the blue whale and the orca, which breathe air and travel huge distances.
- Reptiles — sea turtles like the green sea turtle, which graze seagrass and nest on beaches.
- Reef fish — including the clownfish, which lives among sea anemones on coral reefs.
Explore it in Biosphere
Open the Oceans and Coral Reefs habitat guides to see the species, threats and conservation context of each ecosystem, then open a species profile to learn more about it.