AKA EPIPELAGIC
OPEN OCEAN / EPIPELAGIC ZONE
 From surface to 100-200 m (300-600 ft)
 Beyond shelf break
 Similar to photic zone – layer from surface to the depth
where light limits photosynthesis
 Phytoplankton main primary producers (where
nutrients are available)
 Copepods most abundant zooplankton
 Almost all nekton carnivorous predators
ABIOTIC FACTORS
 Light
 Limited nutrients
 Organic particles sink before they can be released by
bacteria, surface waters poor in nutrients,
phytoplankton growth nutrient-limited
 Nitrogen limiting nutrient in ocean
 Iron limiting in Southern & equatorial Pacific oceans
 At high latitudes winter overturn & mixing bring
nutrient-rich deep water to surface
BIOTIC FACTORS
 Staying afloat
 Cells & tissues denser than water
 Shells & skeletons more dense
 Finding food and avoid being eaten
ADAPTATIONS
 Staying afloat
 Increased water resistance to sink slower

More surface area, more drag, slower sinking
 Increase buoyancy

Storing lipids, gas-filled floats/swim bladders
ADAPTATIONS
 Finding food and avoid being eaten
 highly developed sense organs
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Vision – well developed eyes
Lateral line – sense vibrations in the water
Hearing
Echolocation – built in SONAR in cetaceans
 Coloration & camouflage
 Countershading (dark top & light bottom)
 Excellent swimmers
 Streamlined
 Well-developed & efficient muscles
 High, narrow tails