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Oceans
The student will understand...
•that the ocean is a dynamic system in which many chemical, biological, and physical
changes are taking place
•that estuaries are areas where fresh and salt water mix, producing variations in
salinity and high biological activity
•that from the seashore to the deepest depths, oceans are home to some of the most
diverse life on Earth
•that in the ocean there are innumerable individual food chains overlapping and
intersecting to form complex food webs
•how winds have a powerful effect on the oceans and are an important force in
creating ocean currents
•that seawater has many different gases dissolved in it, especially nitrogen, oxygen and
carbon dioxide
•that carbon dioxide is one of the most important gases that dissolve in the ocean, and
that the ocean is one of Earth's most valuable natural resources
The ocean is a dynamic system where many
chemical, biological, and physical changes are
taking place.
• Largest reservoir of water on Earth
• Largest reservoir of heat on Earth
–Stored heat drives weather
–Causes climate near ocean to be milder
• Summer: heat energy is absorbed
• Winter: heat energy is released
• 92 elements are found in the Ocean:
Sodium and Chlorine are
most abundant
Why is the ocean salty?
• Dissolved chemicals eroded from the earth’s
crust and washed into the sea
• Solid and gaseous ejections from volcanoes
• Particles swept from the land by winds
• Materials dissolved from sediments deposited
on the ocean floor
• Salinity
– The measure of the amount of dissolved salt
contained in water
– Every 1000 grams of seawater contains an
average of 35 grams of salt
– The ocean salinity has actually stayed constant
for the past 1.5 billion years
• Salinity changes
– Increased by evaporation and freezing
– Decreased by rainfall, runoff, or melting ice
How Stuff Works: Why is the Ocean Salty
How is the ocean “zoned”?
• Temperature
• Light
• Plant/animal life
• Distance from shore
Oceanic Zones and Layers
Temperature
• Three layers
– Surface Layer
• Heated by sun
• Mixed by wind/waves
– Thermocline
• Temperature drops fast
with depth
– Deep Water
• Cold all year, anywhere on
the globe
Light
A lot of sunlight
Little to no sunlight
Distance From Shore
1. Intertidal Zone (Closest to shore)
2. Neritic Zone
3. Oceanic Zone (Farthest from Shore)
Oceans are home to the some of the most
diverse life on Earth.
• Oceanographers divide the ocean into zones according
to how far down sunlight penetrates.
• Plants are only in the sunlit zone, where there is
enough light for photosynthesis however animals are
found at all depths in the ocean.
• All life is dependent on plants- only plants have the
ability to manufacture food out inorganic substances.
• Algae are an important food source in the ocean, as
well as an important source of oxygen in the
atmosphere.
• In order to grow, phytoplankton need nutrients from
the sea water as well as an abundance of sunlight.
Estuaries
• Areas where fresh and salt water mix
– Trap nutrients and sediment from land (rivers)
and ocean (tides)
– Nutrients are constantly being mixed because of
tides and river flow
• One of the most productive ecosystems on
earth
– Shallow waters= sunlight can reach the bottom
=more plants
– Good nurseries for species to hatch and grow,
with a lot of diversity
Estuaries
• Environmental filter :
Plants and animals filter pollutants out of the water
– Salt Marsh Plants: trap chemicals and move them
to soil
– Oysters: collect contaminates in bodies as they
eat
– Bacteria: eat organic matter in sediment and
release into atmosphere to prevent build-up in
estuary
• The Pamlico Sound is the largest estuary in
North Carolina What is an estuary?
Upwelling
• Movement of ocean water upwards
• Happens when warm surface water near the coast is
blown offshore by winds
• Cold water along the ocean floor rises bringing
sediment and nutrients with it
• Phytoplankton uses these nutrients to grow and
reproduce at a rapid rate.
• This attracts organisms that rely on phytoplankton,
and their consumers.
• Areas of upwelling are areas of rich biological activity
• Approximately ½ of the fish caught in the world come
from areas where there is upwelling.
Hydrothermal Vents
• Hydrothermal vents are driven by heat
from volcanism beneath the seafloor.
• They are a diverse environment
• Aphotic zone (little to no sunlight)
• Contains cracks in earth’s crust that
release gases
– Bacteria use the chemical to produce “food”
– Chemotrophs (get their energy from
oxidation of organic or inorganic
compounds)
Hydrothermal Vents
What gases are in ocean water?
• Oxygen and other gases dissolve in water
– Oxygen, Nitrogen, CO2
– Same gases as air
• Ocean animals take in Oxygen and give off CO2
(cellular respiration)
• Plants and algae convert CO2 and H2O into food
and release Oxygen (photosynthesis)
Most Common Gases Dissolved:
Nitrogen
Oxygen
Carbon Dioxide
Seawater and Dissolved Gases
The action of ocean wind and waves agitates the ocean
surface, stimulation the exchange of these gases
between the ocean and the atmosphere.
Marine plants depend on dissolved carbon dioxide in
order to perform photosynthesis. Photosynthesis
releases oxygen into ocean water which is in turn used
by ocean organisms for respiration.
Respiration releases energy from stored carbohydrates
and produces carbon dioxide and water as byproducts.
Some properties of seawater affect how
much gas can be dissolved in it
Cold water holds more gas than warm water.
Seawater with low salinity holds more gas than
high salinity water.
Deep water, which has a high pressure, holds
more gas than shallow water.
Carbon Dioxide
• Most important gas in the ocean
• Most reacts to form bicarbonates, which
removes dissolved CO2 from water
• Marine organisms use bicarbonates to
form calcium carbonate shells
Deep Ocean
• At one time, scientists thought life could not exist
on the deep ocean floor
• Submersibles- small vehicle that operates
underwater
– Alvin- 1977
• Scientists discovered new community of organisms
– Can withstand tremendous pressure, high temperatures,
darkness, and toxic chemicals
• Chemosynthetic- create food using chemicals
(oxygen) rather than light
– Found near hydrothermal vents
The Deep Sea
Mapping the Ocean Floor
• Sonar
– Uses sound waves to measure distances and
locate objects
– For mapping small areas
• Satellite imaging
– Detect tiny bumps and dips in the oceans height
Seeing the Ocean Floor with Sonar
Natural Resources from the Ocean…
• Removes CO2 from atmosphere and provides O2,
regulating Earth’s climate
• Source of biomedical organisms with potential for fighting
disease
• Food- fish!
• Shipping- moving cargo between seaports
• Tourism
– Can have negative impact on ocean (garbage and sewage)
– Can promote conservation (ecotourism)
• Mining: Diamonds, Gold, Silver, Metal Ores
– Can have negative impact on ecosystems (dredging pulls up the
ocean floor- the sediment rises in the water interfering with the
photosynthesis process.
• Oil
Marine Food Chains and Food Webs
• Food web: Shows feeding relationship
between organisms in a habitat
– Energy transfer represented by arrows
– Amount of energy decreases as you move up the
web
• Phytoplankton: main producer
• Most marine creatures eat a variety of foods.
If one link in a chain is depleted, the other
consumers in the chain have alternate food
sources.
Marine Food Chains and Food Webs
Ocean organism generally belong to several
different food chains that are linked to form a
food web.
Links to terrestrial food chains and webs when land
animals eat fish.