Water in ocean Mixture of water and more than 70 chemical elements Measure of amount of chemical elements salinity – Ocean 3.5 percent salinity – Mineral salts – sodium, chloride, sulfur, and magnesium Water in ocean Mixture of water and more than 70 chemical elements Measure of amount of chemical elements salinity – Ocean 3.5 percent salinity – Mineral salts – sodium, chloride, sulfur, and magnesium

Circulation of water throughout the ocean Two main types – First type is wind-driven Move upper parts of ocean current horizontally Planetary-scale prevailing winds create current Gulf stream major wind-driven current California current moves cold arctic waters southward

Aspects of wind-driven ocean currents – Vertical distribution of heat – Called upwelling – Moves surface waters from equator to continents – Warm water replaces by cooler deeper water – Brings cool, nutrient-rich water up – Linked to changes in global climate patterns

Second type is thermohaline circulation – Thermo means heat, haline means salilinty Driven by temperature and salinity Cold waters of North Atlantic Ocean – Create cold, saline-rich water that sinks – Creeps along bottom until reaches upwelling zones – How nutrients and heat are circulated

Euphotic – top zone – Enough sunlight for photosynthesis – Extends no deeper than 600 feet Disphotic zone – Small amount of sunlight – No photosynthesis – Depth 3,000 feet

Aphotic zone – No light at all – Strange species of aquatic organisms Benthic zone – Subject to extreme pressure – near freezing – Composed of thick mudlike sediments Can be more than 1 mile thick

Important feature of the ocean – Thermocline Area where: – Warm, nutrient-poor mixes with cold, nutrient-rich water Area of extreme temperature change Depths varies from 50 to more than 600 feet Organisms migrate to thermocline as depth changes Life Zones in the Ocean ( continued )

Shallow, sloping area around margins of continents Average depth of 400 feet Most are in the euphotic zone Support a variety of aquatic life – 90 % of all fish and shellfish Stretch out about 45 miles – Can be up to 900 miles

Along edges of shelves deep submarine canyons Depths up to 12,000 feet Associated with world’s largest rivers Shaped by sediments and currents from rivers Submerged Canyon from Hudson River – 3,600 feet deep and 5 miles wide

Areas along shore – Within reaches of low and high tides Harbor abundance of life – Consist of shorelines and tidal pools Harsh aquatic environment – Rise/fall of water – Strong currents – Wave action – Periodically exposed to air

Two basic types: – Rocky intertidal Composed of large rocks that line the shore – Sandy intertidal Made up of mostly sand – Both have their own unique organism communities