Open Ocean
Pelagic Zone: Light penetrates the top few meters
Except in areas of upwelling, nutrient concentrations are generally low, because the remains of dead organisms sink to the bottom of the ocean.
All organisms are floating or free-swimming “nekton”. The major producers are photosynthetic algae.
Abyssal Zone: Nutrients reach this zone by falling from above.
Light is absent. This zone supports a wide variety of specially-adapted organisms