The Open Ocean 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 Finding food and avoid being eaten 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 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