Oceans

From wave to wave…

Ocean: What is it?• One continuous body of water• Many basins: North Atlantic, South Atlantic, North

Pacific, South Pacific, Indian, and Arctic• Contain dissolved salts (mostly sodium chloride)—

from millions of years of dissolving them from rocks on the land

• Connected to land via rivers, bays, and estuaries• Ocean Zones: Ocean organized vertically according

to the amount of three factors:– 1. temperature– 2. pressure– 3. light

Estuary: What is it?• An estuary is formed where rivers meet the sea.• An estuary is a semi-enclosed river mouth or bay

where salty seawater is diluted by freshwater from rivers and creeks.

• An estuary is made up of tidal marshes, tidal flats, and open water channels.

• An estuary is flooded by the tides.

Estuaries: Functions1. Habitat—for many types of marine fish, mollusks,

crustaceans, etc.2. Buffer Zone—from the river to the ocean3. Breeding ground and nursery—for fish larvae, small

young sea creatures4. Filter—to filter out pollutants and sediment washed

down from rivers.

Open Ocean Zones

The Ocean Zones• Intertidal (Between High and Low Tide)• Neritic (Low Tide to Continental Edge)• Benthic (Ocean Floor)• Pelagic (Open Ocean )– Epipelagic (Sunlight)– Mesopelagic (Twilight)– Bathypelagic (Midnight)– Abyssopelagic (The Abyss)– Hadalpelagic (The Trenches)

Pelagic

Abyssal

Intertidal

Benthic

Intertidal Zone• Located at the edge of the

ocean, between the highest high-tide line and the lowest low-tide line.

• During periods of low tide, it is possible to explore the ocean floor in the intertidal zone.

• Most thoroughly studied, and best-known, ocean area.

• Even within the intertidal areas, the cycle of exposure to air varies markedly—so much that four different habitat bands have been identified: 1) the spray zone, 2) the high-tide zone, 3) the mid-tide zone, 4) the low-tide zone

Intertidal Zones

Intertidal Zone Creatures

High Tide

Low Tide

Neritic Zone• From low tide line to edge of continental shelf• More organisms known than any other zone• Major fishing grounds—contain nekton, or free

swimming animals like fish, octopus, and marine mammals

• Sunlight and nutrients• Two diverse habitats– Coral Reefs– Kelp forests

Coral Reefs• Made of tiny organisms surrounded by hard shells.• Shallow tropical waters• Develop over long periods of time (mm/yr)

Kelp Forest• Cold neritic waters• Rocky bottoms• Holdfast - rootlike

attachments• Kelp = algae• Photosynthesis• Symbiotic relationship

with sea otters– Urchins eat kelp– Otters eat urchins– Kelp habitat for otters

Benthic Zone* Benthic: a term meaning bottom. The zone

goes from the shore to the deepest part of the ocean.

• Benthos-- kinds of organisms that live either in or on the ocean floor– plants, anemones, sponges, fish, skates and rays, octopus, mollusks, crabs, sea stars, corals and worms. Most are scavengers.

Benthic Zone– from the shore to the depths

Conditions in the Open Ocean

• Light only at top• Fewer nutrients• Fewer organisms known• Five zones– Epipelagic Zone (Sunlight Zone)– Mesopelagic Zone (Twilight Zone)– Bathypelagic Zone (Midnight Zone)– Abyssopelagic Zone (Deep Ocean)– Hadalpelagic Zone (The Trenches)

Epipelagic Zone• The surface layer of the ocean is known as

the epipelagic zone and extends from the surface to 200 meters (656 feet). It is also known as the Sunlight Zone because this is where most of the visible light exists.

• With the light comes heat, which is responsible for the wide range of temperatures that occur in this zone.

• Plankton: small organisms in this zone:– Phytoplankton—free floating,

photosynthetic organisms, like diatoms and algae

– Zooplankton—propel themselves, microscopic crustaceans, copepods, fish larvae

Mesopelagic Zone• The Twilight Zone extends from 200

meters (656 feet) to 1000 meters (3281 feet).

• The light that penetrates to this depth is extremely faint. It is in this zone that we begin to see the twinkling lights of bioluminescent creatures.

• A great diversity of strange and bizarre fishes can be found here. Many are soft and gelatinous, from transparent squid, octopuses and jellyfish to large colonial animals called siphonophores.

Bathypelagic Zone• The Midnight Zone extends from 1000

meters (3281 feet) down to 4000 meters (13,124 feet).

• Here the only visible light is that produced by the creatures themselves.

• The water pressure at this depth is immense, reaching 5,850 pounds per square inch. In spite of the pressure, a surprisingly large number of creatures can be found here.

• Sperm whales can dive down to this level in search of food. Most of the animals that live at these depths are black or red in color due to the lack of light.

Abyssopelagic Zone • The Abyss extends from 4000 meters

(13,124 feet) to 6000 meters (19,686 feet). The name comes from a Greek word meaning "no bottom".

• The water temperature is near freezing, and there is no light at all.

• Very few creatures can be found at these crushing depths. Most of these are invertebrates such as basket stars and tiny squids. Three-quarters of the ocean floor lies within this zone.

Hadalpelagic Zone• This layer extends from 6000 meters

(19,686 feet) to the bottom of the deepest parts of the ocean in The Trenches.

• The temperature of the water is just above freezing, and the pressure is an incredible eight tons per square inch. That is approximately the weight of 48 Boeing 747 jets. Invertebrates such as starfish and tube worms can thrive at these depths.

• In the deep ocean, there are special benthic communities around hydrothermal vents whose energy comes from chemical reactions rather than from the sun.

Ocean CurrentsAn Ocean Current is a large volume of water flowing

in a certain direction.Wind-driven currents are called surface currents.Surface currents carry warm or cold water

horizontally across the ocean’s surface

Rip Currents• A rip current is a narrow,

powerful surface current which flows away from the shore.

• It is caused by pressure building up from uneven buildup of water from waves.

• They can flow very quickly and can be difficult to detect until you are in one.

• They are VERY dangerous, avoid them when swimming.

Upwelling• Upwelling is the vertical movement of water

toward the ocean’s surface.• Upwelling occurs when wind blows across the

ocean’s surface and pushes water away from an area. Deeper colder water then rises to replace it.

Upwelling often occurs along coastlines.

Upwelling brings cold, nutrient-rich water from deep in the ocean to the ocean’s surface.

Density Currents• Density Currents are a type of vertical current

that carries water from the surface to deeper parts of the ocean.

Density Currents are caused by changes in density rather than wind.

Density currents circulate thermal energy, nutrients and gases.

Great Ocean Conveyor Belt• The Great Ocean conveyor Belt is the name for a

model of the large system of ocean currents that affects weather and climate by circulating thermal energy around Earth.

• In this model, high salinity water cools and sinks in the North Atlantic, and deep water returns to the surface in the Indian and Pacific Oceans through upwelling

Oceans: Human Uses• Oceans responsible for most of

the rain (evaporation /precipitation) and ~50% of oxygen production (plankton) on Earth.

• Humans use the ocean for food (fish), medicine (plants /animals), minerals, and other resources.

• Ocean is limited—overfishing, global climate change, and pollution can severely affect the ocean environment.