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Marine Conservation Science and Policy Service
learning Program
Scientists have divided the ocean into five main layers. These layers, known as
"zones", extend from the surface to the most extreme depths where light can no longer
penetrate. These deep zones are where some of the most bizarre and fascinating
creatures in the sea can be found. As we dive deeper into these largely unexplored
places, the temperature drops and the pressure increases at an astounding rate. The
following diagram lists each of these zones in order of depth.
Module 1: Ocean and Coastal Habitats
Section 1: Ocean Zones
Sunshine State Standards
SC.912.E.7.2, SC.912.E.7.4, SC.912.E.7.5, SC.912.E.7.8,
SC.912.E.7.9, SC.912.E.6.3, SC.912.E.6.5
Objectives




Students will understand the Ocean Zones through different experiments.
Identify various coastal and ocean habitats
Describe the different ocean zones
Examine the adaptations of aquatic species that allow them to live in certain
habitats
 Students will experiment with a model of what happens to light and colors as one
descends into the ocean.
 Students will describe at least two adaptations to low or no ambient light on the
part of deep-sea organisms
 Students work in small groups to experiment with currents caused by
temperature variations that simulate the origins and flow of polar bottom currents.
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Vocabulary
Abyssopelagic Zone- The next layer is called the abyssopelagic zone, also known as
the abyssal zone or simply as the abyss. It 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. The
deepest fish ever discovered was found in the Puerto Rico Trench at a depth of 27,460
feet (8,372 meters).
Bathypelagic Zone- The next layer is called the bathypelagic zone. It is sometimes
referred to as the midnight zone or the dark zone. This 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.
Benthic- Pertaining to the ocean floor.
Consumer- An organism that consumes other organisms as a food source.
Continental margin- Underwater plains connected to continents, separating them from
the deep ocean floor.
Chemosynthesis- The chemical process by which bacteria, by oxidizing hydrogen
sulfide, serve as primary producer for a marine community.
Cosmic rain- In mid-1997, however, scientists offered a new theory on the how the
oceans possibly filled in. The National Aeronautics and Space Administration's Polar
satellite, launched in early 1996, discovered that small comets about 40 feet (12 meters)
in diameter are bombarding Earth's atmosphere at a rate of about 43,000 a day. These
comets break up into icy fragments at heights 600 to 15,000 miles (960 to 24,000
kilometers) above ground. Sunlight then vaporizes these fragments into huge clouds,
which condense into rain as they sink lower in the atmosphere.
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 come heat. This heat
is responsible for the wide range of temperatures that occur in this zone.
Fracture zone- Faults in the ocean floor that form at nearly right angles to the ocean's
major ridges.
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Guyot- An extinct, submarine volcano with a flat top.
Hadalpelagic Zone- Beyond the abyssopelagic zone lies the forbidding hadalpelagic
zone. This layer extends from 6000 meters (19,686 feet) to the bottom of the deepest
parts of the ocean. These areas are mostly found in deep water trenches and canyons.
The deepest point in the ocean is located in the Mariana Trench off the coast of Japan
at 35,797 feet (10,911 meters). 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. In spite of the pressure and temperature, life can still be
found here. Invertebrates such as starfish and tube worms can thrive at these depths
Mesopelagic Zone- Below the epipelagic zone is the mesopelagic zone, extending
from 200 meters (656 feet) to 1000 meters (3281 feet). The mesopelagic zone is
sometimes referred to as the twilight zone or the midwater zone. 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.
Pelagic- The water portion of the ocean.
Photosynthesis- The process by which green plants produce energy by converting
carbon dioxide, water, and other nutrients to simple carbohydrates, releasing oxygen as
a by-product.
Phytoplankton- Microscopic aquatic plants.
Producer- An organism that is capable of utilizing nonliving materials and an external
energy source to produce organic molecules (for example, carbohydrates), which are
then used as food.
Ridge- Very long underwater mountain ranges created as a by-product of seafloor
spreading.
Rift- Crevice that runs down the middle of a ridge.
Seafloor spreading- Process whereby new oceanic crust is created at ridges.
Seamount- Active or inactive submarine volcano.
Zooplankton- Microscopic aquatic animals.
________________________________________________________________
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Background
An ocean is a major body of saline
water, and a principal component
of the hydrosphere. Approximately
71% of the Earth's surface is
covered by ocean, a continuous
body of water that is customarily
divided into several principal
oceans and smaller seas.
More than half of this area is over
3,000 meters (9,800 ft) deep.
Average oceanic salinity is around
35 parts per thousand (ppt) (3.5%),
and nearly all seawater has a
salinity in the range of 30 to 38 ppt.
Scientists estimate that 230,000 marine life forms of all types are currently known, but
the total could be up to 10 times that number.
Though generally described as several 'separate' oceans, these waters comprise one
global, interconnected body of salt water sometimes referred to as the World Ocean or
global ocean. This concept of a continuous body of water with relatively free
interchange among its parts is of fundamental importance to oceanography.
The major oceanic divisions are defined in part by the continents, various archipelagos,
and other criteria. These divisions are (in descending order of size):





Pacific Ocean, which separates Asia and Australia from the Americas
Atlantic Ocean, which separates the Americas from Eurasia and Africa
Indian Ocean, which washes upon southern Asia and separates Africa and
Australia
Southern Ocean, which, unlike other oceans, has no landmass separating it from
other oceans and is therefore sometimes subsumed as the southern portions of
the Pacific, Atlantic, and Indian Oceans, which encircles Antarctica and covers
much of the Antarctic
Arctic Ocean, sometimes considered a sea of the Atlantic, which covers much of
the Arctic and washes upon northern North America and Eurasia
The Pacific and Atlantic may be further subdivided by the equator into northern and
southern portions. Smaller regions of the oceans are called seas, gulfs, bays, straits
and other names.
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Origin of ocean water
One scientific theory about the origin of ocean water states that as Earth formed from a
cloud of gas and dust more than 4.5 billion years ago, a huge amount of lighter
elements (including hydrogen and oxygen) became trapped inside the molten interior of
the young planet. During the first one to two billion years after Earth's formation, these
elemental gases rose through thousands of miles of molten and melting rock to erupt on
the surface through volcanoes and fissures (long narrow cracks).
Within the planet and above the surface, oxygen combined with hydrogen to form water.
Enormous quantities of water shrouded the globe as an incredibly dense atmosphere of
water vapor. Near the top of the atmosphere, where heat could be lost to outer space,
water vapor condensed to liquid and fell back into the water vapor layer below, cooling
the layer. This atmospheric cooling process continued until the first raindrops fell to the
young Earth's surface and flashed into steam. This was the beginning of a fantastic
rainstorm that, with the passage of time, gradually filled the ocean basins.
Scientists calculate that this cosmic rain adds one inch of water to Earth's surface every
10,000 to 20,000 years. This amount of water could have been enough to fill the oceans
if these comets have been entering Earth's atmosphere since the planet's beginning 4.5
billion years ago.
Ocean and life
The ocean has a significant effect on the biosphere. Oceanic evaporation, as a phase of
the water cycle, is the source of most rainfall, and ocean temperatures determine
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climate and wind patterns that affect life on land. Life within the ocean evolved 3 billion
years prior to life on land. Both the depth and distance from shore strongly influence the
amount and kinds of plants and animals that live there.
Physical properties
The area of the World Ocean is
361×106 km2.
Its volume is
approximately
1.3
billion
cubic
kilometers. This can be thought of as
a cube of water with an edge length of
1,111 kilometers (690 mi). Its average
depth is 3,790 meters (12,430 ft), and
its maximum depth is 10,923 meters.
Nearly half of the world's marine
waters are over 3,000 meters (9,800
ft) deep. The vast expanses of deep ocean (anything below 200 meters (660 ft) cover
about 66% of the Earth's surface. This does not include seas not connected to the
World Ocean, such as the Caspian Sea.
The total mass of the hydrosphere is about 1,400,000,000,000,000,000 metric tons
(1.5×1018 short tons) or 1.4×1021 kg, which is about 0.023 percent of the Earth's total
mass. Less than 3 percent is freshwater; the rest is saltwater, mostly in the ocean.
Color
A common misconception is that the oceans are
blue primarily because the sky is blue. In fact, water
has a very slight blue color that can only be seen in
large volumes. While the sky's reflection does
contribute to the blue appearance of the surface, it
is not the primary cause. The primary cause is the
absorption by the water molecules' nuclei of red
photons from the incoming light, the only known
example of color in nature resulting from vibrational,
rather than electronic, dynamics.
Glow
Sailors and other mariners have reported that the
ocean often emits a visible glow, or luminescence,
which extends for miles at night. In 2005, scientists
announced that for the first time, they had obtained
photographic evidence of this glow. It may be
caused by bioluminescence. (Image: The "milk sea"
in a composite satellite image, and the region of the
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Indian Ocean off the coast of Somalia where it was spotted by the Defense
Meteorological Satellite Program.)
Mariners have long told of rare nighttime events in which the ocean glows intensely as
far as the eye can see in all directions.
Fictionally, such a ―milky sea‖ is encountered by the Nautilus in Jules Verne classic
―20,000 Leagues Under the Sea.‖
Scientists don’t have a good handle what’s going on. But satellite sensors have now
provided the first pictures of a milky sea and given new hope to learning more about the
elusive events.
The newly released images show a vast region of the Indian Ocean, about the size of
Connecticut, glowing three nights in a row. The luminescence was also spotted from a
ship in the area.
―The circumstances under which milky seas form is almost entirely unknown,‖ says
Steven Miller, a Naval Research Laboratory scientist who led the space-based
discovery. ―Even the source for the light emission is under debate.‖
Scientists suspect bioluminescent bacteria are behind the phenomenon. Such creatures
produce a continuous glow, in contrast to the brief, bright flashes of light produced by
―dinoflagellate‖ bioluminescent organims that are seen more commonly lighting up ship
wakes and breaking waves.
―The problem with the bacteria hypothesis is that an extremely high concentration of
bacteria must exist before they begin to produce light,‖ Miller told LiveScience. ―But
what could possibly support the occurrence of such a large population?‖
One idea, put forward by the lone research vessel to ever encounter a milky sea, is that
the bacteria are not free-living, but instead are living off some local supporting
―substrate.‖
The mystery highlights how little scientists know about the ocean. Milky seas appear to
be most prevalent in the Indian Ocean, where there are many trade routes, and near
Indonesia.
―But there could be other areas we simply don’t know about yet,‖ Miller said. ―In fact,
we’re already beginning to receive feedback from additional witnesses of milky seas.
Some of these accounts occurred in regions we had not thought to look before, and
we’re currently working to find matches with the satellite data.‖
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There have been 235 documented sightings of milky seas since 1915 – mainly
concentrated in the north-western Indian Ocean and near Java, Indonesia.
Exploration
Ocean travel by boat dates back to prehistoric times, but only in modern times has
extensive underwater travel become possible.
The deepest point in the ocean is the Mariana Trench, located in the Pacific Ocean near
the Northern Mariana Islands. Its maximum depth has been estimated to be
10,971 meters (35,994 ft) (plus or minus 11 meters; see the Mariana Trench article for
discussion of the various estimates of the maximum depth.) The British naval vessel,
Challenger II surveyed the trench in 1951 and named the deepest part of the trench, the
"Challenger Deep". In 1960, the Trieste successfully reached the bottom of the trench,
manned by a crew of two men.
Much of the ocean bottom remains unexplored and unmapped. A global image of many
underwater features larger than 10 kilometers (6.2 mi) was created in 1995 based on
gravitational distortions of the nearby sea surface.
Culture
The original concept of "ocean" goes back to
notions of Mesopotamian and Indo-European
mythology, imagining the world to be encircled by
a great river. Okeanos in Greek, reflects the
ancient Greek observation that a strong current
flowed off Gibraltar and their subsequent
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assumption that it was a great river. (Compare also Samudra from Hindu mythology and
Jörmungandr from Norse mythology.) The world was imagined to be enclosed by a
celestial ocean above the heavens, and an ocean of the underworld below.
Artworks which depict maritime themes are known as marine art, a term which
particularly applies to common styles of European painting of the 17th to 19th centuries.
Ocean basin
Ocean basins are that part of Earth's surface that extends seaward from the continental
margins (underwater plains connected to continents, separating them from the deep
ocean floor). Basins range from an average water depth of about 6,500 feet (2,000
meters) down into the deepest trenches. Ocean basins cover about 70 percent of the
total ocean area.
The familiar landscapes of continents are mirrored, and generally magnified, by similar
features in the ocean basin. The largest underwater mountains, for example, are higher
than those on the continents. Underwater plains are flatter and more extensive than
those on the continents. All basins contain certain common features that include
oceanic ridges, trenches, fracture zones, abyssal plains, and volcanic cones.
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Oceanic ridges - Enormous mountain ranges,
or oceanic ridges, cover the ocean floor. The
Mid-Atlantic Ridge, for example, begins at the
tip of Greenland, runs down the center of the
Atlantic Ocean between the Americas on the
west and Africa on the east, and ends at the
southern tip of the African continent. At that
point, it stretches around the eastern edge of
Africa, where it becomes the Mid-Indian Ridge.
That ridge continues eastward, making
connections with other ridges that eventually
end along the western coastline of South and
Central America. Some scientists say this is a
single oceanic ridge that encircles Earth, one
that stretches a total of more than 40,000 miles
(65,000 kilometers).
In most locations, oceanic ridges are 6,500 feet
(2,000 meters) or more below the surface of the
oceans. In a few places, however, they actually
extend above sea level and form islands. Iceland (in the North Atlantic), the Azores
(about 900 miles [about 1,500 kilometers] off the coast of Portugal), and Tristan de
Cunha (in the South Atlantic midway between southern Africa and South America) are
examples of such islands.
Running along the middle of an oceanic ridge, there is often a deep crevice known as a
rift, or median valley. This central rift can plunge as far as 6,500 feet (2,000 meters)
below the top of the ridge that surrounds it. Scientists believe ocean ridges are formed
when molten rock, or magma, escapes from Earth's interior to form the seafloor, a
process known as seafloor spreading. Rifts may be the specific parts of the ridges
where the magma escapes.
Trenches - Trenches are long, narrow, canyon like structures, most often found next to
a continental margin.
They occur much more
commonly in the Pacific
than in any of the other
oceans. The deepest
trench on Earth is the
Mariana Trench, which
runs from the coast of
Japan south and then
west
toward
the
Philippine
Islands—a
distance of about 1,580
miles (2,540 kilometers).
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Its deepest spot is 36,198 feet (11,033 meters) below sea level. The longest trench is
located along the coast of Peru and Chile. Its total length is 3,700 miles (5,950
kilometers) and it has a maximum depth of 26,420 feet (8,050 meters). Earthquakes
and volcanic activity are commonly associated with trenches.
Fracture
zones
Fracture
zones
are
regions where sections
of the ocean floor slide
past each other, relieving
tension
created
by
seafloor spreading at the
ocean ridges. Ocean
crust in a fracture zone
looks like it has been
sliced up by a giant knife.
The faults in a zone
usually cut across ocean
ridges, often nearly at
right angles to the ridge. A map of the North Atlantic Ocean basin, for example, shows
the Mid-Atlantic Ridge traveling from north to south across the middle of the basin, with
dozens of fracture zones cutting across the ridge from east to west.
Abyssal plains Abyssal plains are
relatively flat areas
of the ocean basin
with slopes of less
than one foot of
elevation
difference for each
thousand feet of
distance.
They
tend to be found at
depths of 13,000
to 16,000 feet
(4,000 to 5,000
meters). Oceanographers believe that abyssal plains are so flat because they are
covered with sediments (clay, sand, and gravel) that have been washed off the surface
of the continents for hundreds of thousands of years. On the abyssal plains, these
layers of sediment have now covered up any irregularities that may exist in the rock of
the ocean floor beneath them.
Abyssal plains found in the Atlantic and Indian Oceans tend to be more extensive than
those in the Pacific Ocean. One reason for this phenomenon is that the majority of the
world's largest rivers empty into either the Atlantic or the Indian Oceans, providing both
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ocean basins with an endless supply of the sediments from which abyssal plains are
made.
Volcanic cones Ocean basins are
alive with volcanic
activity.
Magma
flows upward from
the mantle to the
ocean bottom not
only through rifts, but
also
through
numerous volcanoes
and other openings
in the ocean floor.
Seamounts
are
submarine volcanoes
and can be either
active or extinct.
Guyots are extinct volcanoes that were once above sea level but have since receded
below the surface. As they receded, wave or current action eroded the top of the
volcano to a flat surface.
Seamounts and guyots
typically rise about 0.6 mile
(1 kilometer) above the
ocean floor. One of the
largest known seamounts is
Great Meteor Seamount in
the northeastern part of the
Atlantic Ocean. It extends
to a height of more than
1,300 feet (4,000 meters)
above the ocean floor.
Ocean Zones
Ocean zones are layers
within the oceans that
contain distinctive plant and
animal life. They are
sometimes referred to as ocean layers or environmental zones. The ocean environment
is divided into two broad categories, known as realms: the benthic realm (consisting of
the seafloor) and the pelagic realm (consisting of the ocean waters). These two realms
are then subdivided into separate zones according to the depth of the water.
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Regions and depths
Oceanographers divide the
ocean into regions depending
on physical and biological
conditions of these areas.
The pelagic zone includes all
open ocean regions, and can
be divided into further regions
categorized by depth and
light abundance. The photic
zone covers the oceans from
surface level to 200 meters
down. This is the region
where photosynthesis can
occur and therefore is the
most biodiverse. Since plants
require photosynthesis, life
found deeper than this must
either rely on material sinking from above (see marine snow) or find another energy
source; hydrothermal vents are the primary option in what is known as the aphotic zone
(depths exceeding 200 m). The pelagic part of the photic zone is known as the
epipelagic. The pelagic part of the aphotic zone can be further divided into regions that
succeed each other vertically according to temperature.
The mesopelagic is the uppermost region. Its lowermost boundary is at a thermocline of
12 °C (54 °F), which, in the tropics generally lies at 700–1,000 meters (2,300–3,300 ft).
Next is the bathypelagic lying between 10-4 °C (43 °F), typically between 700–1,000
meters (2,300–3,300 ft) and 2,000–4,000 meters (6,600–13,000 ft) Lying along the top
of the abyssal plain is the abyssalpelagic, whose lower boundary lies at about
6,000 meters (20,000 ft). The last zone includes the deep trenches, and is known as the
hadalpelagic. This lies between 6,000–11,000 meters (20,000–36,000 ft) and is the
deepest oceanic zone.
Along with pelagic aphotic zones there are also benthic aphotic zones. These
correspond to the three deepest zones of the deep-sea. The bathyal zone covers the
continental slope down to about 4,000 meters (13,000 ft). The abyssal zone covers the
abyssal plains between 4,000 and 6,000 m. Lastly, the hadal zone corresponds to the
hadalpelagic zone which is found in the oceanic trenches. The pelagic zone can also be
split into two subregions, the neritic zone and the oceanic zone. The neritic
encompasses the water mass directly above the continental shelves, while the oceanic
zone includes all the completely open water. In contrast, the littoral zone covers the
region between low and high tide and represents the transitional area between marine
and terrestrial conditions. It is also known as the intertidal zone because it is the area
where tide level affects the conditions of the region.
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Water depth versus light penetration
Sunlight
obviously
cannot
penetrate beyond a certain depth
in the ocean. Some organisms
have, however, evolved to cope
with the absence of sunlight at
great depths. Plants require
sunlight
to
carry
on
photosynthesis—the process by
which they convert carbon dioxide,
water, and other nutrients to
simple carbohydrates to produce
energy, releasing oxygen as a byproduct. Below a depth of about
660 feet (200 meters), not enough
sunlight penetrates to allow
photosynthesis to occur. The area
of
the
ocean
where
photosynthesis occurs is known as the euphotic zone (meaning "good light").
From
the
standpoint
of
living organisms,
the euphotic zone
is probably the
most important of
all oceanic zones.
By
some
estimates, about
two-thirds of all
the
photosynthetic
activity
that
occurs on Earth
(on land and in
the water) takes
place within the
euphotic zone.
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From 660 to 3,000 feet (200 to
900 meters), only about 1
percent of sunlight penetrates.
This layer is known as the
dysphotic zone (meaning "bad
light"). Below this layer, down to
the deepest parts of the ocean,
it is perpetual night. This last
layer is called the aphotic zone
(meaning "without light"). At
one time, scientists thought that
very little life existed within the
aphotic zone. However, they
now know that a variety of
interesting organisms can be
found living on the deepest
parts of the ocean floor.
The benthic realm
The benthic realm extends from the
shoreline to the deepest parts of the
ocean floor. The benthic realm is an
especially rich environment for
living organisms. Scientists now
believe that up to 98 percent of all
marine species are found in or near
the ocean floor. Some of these are
fish or shellfish swimming just
above the ocean floor. Most are
organisms that burrow in the sand
or mud, bore into or are attached to
rocks, live in shells, or simply move
about on the ocean floor.
In the deeper parts of the ocean
floor, below the euphotic zone, no
herbivores (plant eaters) can
survive. However, the "rain" of dead
organic matter from above still
supports thriving bottom communities.
The benthic zone is the ecological region at the lowest level of a body of water such as
an ocean or a lake, including the sediment surface and some sub-surface layers.
Organisms living in this zone are called benthos. They generally live in close
relationship with the substrate bottom; many such organisms are permanently attached
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to the bottom. The superficial layer of the soil lining the given body of water, the benthic
boundary layer, is an integral part of the benthic zone, as it influences greatly the
biological activity which takes place there. Examples of contact soil layers include sand
bottoms, rock outcrops, coral, and bay mud.
Organisms
Benthos are the organisms which live in the benthic
zone, and are different from those elsewhere in the
water column. Many are adapted to live on the
substrate (bottom). In their habitats they can be
considered as dominant creatures. Many organisms
adapted to deep-water pressure cannot survive in the
upper parts of the water column. The pressure
difference can be very significant (approximately one
atmosphere for each 10 meters of water depth).
Because light does not penetrate very deep ocean-water, the energy source for the
benthic ecosystem is often organic matter from higher up in the water column which
drifts down to the depths. This dead and decaying matter sustains the benthic food
chain; most organisms in the benthic zone are scavengers or detritivores. Some
microorganisms use chemosynthesis to produce biomass.
Benthic organisms can be divided into two categories based on whether they make their
home on the ocean floor or an inch or two into the ocean floor. Those living on the
surface of the ocean floor are known as epifauna. Those who live burrowed into the
ocean floor are known as infauna.
The pelagic realm
In the region of the pelagic
zone from the surface to 660
feet
(200
meters),
phytoplankton (algae and
microscopic plants) live. They
are the primary producers of
the ocean, the lowest level on
the oceanic food web. They
use
the
process
of
photosynthesis to provide
food for themselves and for
higher organisms.
On the next level upward in
the pelagic food web are the
primary
consumers,
the
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zooplankton (microscopic animals). They feed on phytoplankton and, in turn, become
food for larger animals (secondary consumers) such as sardines, herring, tuna, bonito,
and other kinds of fish and swimming mammals. At the top of this food web are the
ultimate consumers, the toothed whales.
In the region from a depth of about 660 to 3,000 feet (200 to 900 meters), a number of
organisms survive by spending daylight hours within this region and then rising toward
the surface during evening hours. In this way, they can feed off the phytoplankton and
zooplankton available near and on the surface of the water while avoiding predators
during the day. The most common organisms found in this region are small fish, squid,
and simple shellfish. A number of these organisms have evolved some interesting
adaptations for living in this twilight world. They often have very large eyes, capable of
detecting light only 1 percent as intense as that visible to the human eye. A majority
also have light-producing organs that give off a
phosphorescence that makes them glow in the dark.
Organisms found below 3,000 feet (900 meters) have
also evolved some bizarre adaptations for survival in
their lightless environment. In the deeper regions,
pressures may exceed 500 times that of atmospheric
pressure, or the equivalent of several tons per square
inch. Temperatures never get much warmer than about
37°F (3°C). Organisms within these regions generally
prey on each other. They have developed special
features such as expandable mouths, large and very
sharp teeth, and special strategies for hunting or luring
prey.
Any water in the sea that is not close to the bottom or
near to the shore is in the pelagic zone. The pelagic
zone can be thought of in terms of an imaginary cylinder
or water column that goes from the surface of the sea
almost to the bottom, as shown in the diagram below.
Conditions change deeper down the water column; the
pressure increases, the temperature drops and there is
less light. Depending on the depth, scientists further
subdivide the water column, rather like the Earth's
atmosphere is divided into different layers.
The pelagic zone occupies 1,370 million cubic kilometers
(330 million cubic miles) and has a vertical range up to
11 kilometers (6.8 miles). Fish that live in the pelagic
zone are called pelagic fish. Pelagic life decreases with
increasing depth. It is affected by light levels, pressure,
temperature, salinity, the supply of dissolved oxygen and
nutrients, and the submarine topography. In deep water,
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the pelagic zone is sometimes called the open-ocean zone and can be contrasted with
water that is near the coast or on the continental shelf. However in other contexts,
coastal water that is not near the bottom is still said to be in the pelagic zone.
The pelagic zone can be contrasted with the benthic and demersal zones at the bottom
of the sea. The benthic zone is the ecological region at the very bottom of the sea. It
includes the sediment surface and some sub-surface layers. Marine organisms living in
this zone, such as clams and crabs, are called benthos. The demersal zone is just
above the benthic zone. It can be significantly affected by the seabed and the life that
lives there. Fish that live in the demersal zone are called demersal fish. Demersal fish
can be divided into benthic fish, which are denser than water so they can rest on the
bottom, and benthopelagic fish, which swim in the water column just above the bottom.
Demersal fish are also known as bottom feeders and groundfish.
Depth and layers
Epipelagic (sunlit)
The illuminated surface zone where there is enough light for photosynthesis. Due to
this, plants and animals are largely concentrated in this zone. Nearly all primary
production in the ocean occurs here. This layer is the domain of fish such as tuna, many
sharks, dolphin fish, and jellyfish. This zone is also known as the surface zone.
Mesopelagic (twilight)
Although some light penetrates this
deep,
it is
insufficient for
photosynthesis. At about 500 m
the water becomes depleted of
oxygen. Still, an abundance of life
copes with more efficient gills or
minimal movement. Animals such
as swordfish, squids, wolffish, a
few species of cuttlefish, and other
semi-deep-sea creatures live here.
Many bioluminescent organisms
live in this zone. Due to the relative
lack of nutritious food found in this
zone, some creatures living in the
mesopelagic zone will rise to the
epipelagic zone at night in order to
feed.
Bathypelagic (darkzone)
By this depth the ocean is pitch black, apart from the occasional bioluminescent
organism, such as lanternfish. There are no living plants, and most animals survive by
18
consuming the snow of detritus falling from the zones above or (like the marine
hatchetfish) by preying upon others. Giant squid (as well as smaller squids & Dumbo
octopodes) live at this depth, and here they are hunted by deep-diving sperm whales.
Abyssopelagic (lower midnight)
Very few creatures are sufficiently adapted to survive in the cold temperatures and
incredible pressures found at this depth. Among the species found in this zone are
several species of squid; echinoderms including the basket star, swimming cucumber,
and the sea pig; and marine arthropods including the sea spider. Many of the species
living at these depths have evolved to be transparent and eyeless as a result of the total
lack of light in this zone.
Hadopelagic
This zone is mostly unknown, and very few species are known to live here (in the open
areas). However, many organisms live in hydrothermal vents in this and other zones.
Some define the hadopelagic as waters below 6,000 m (19,685 ft), whether in a trench
or not.
The bathypelagic, abyssopelagic, and hadopelagic zones are very similar in character,
and some marine biologists combine them into a single zone or consider the latter two
to be the same. The abyssal plain is covered with soft sludge covered by the dead
organisms from above.
Minerals Nutrients
Nitrogen is generally the limiting mineral nutrient for
primary production in the oceans, although iron is
also limiting in some oceans. When organisms die,
they sink and take their minerals with them to the
bottom where the minerals are released by
decomposers. Consequently, cold deep ocean
water is often much higher in essential mineral
nutrients than surface waters where primary
production depletes them. Where ocean currents,
climate and geography force deep water to the
surface, primary production increases dramatically
with the introduction of higher levels of mineral
nutrients. This production supports entire food
chains. This upwelling is caused by both geographic
and climatic factors. It produces areas in the ocean
where the fisheries are particularly rich, and thus,
are of high interest to humans.
19
Temperatures
Complicating this issue
of heat storage in the
oceans is the fact that
the oceans are not
really just one big
monolithic
pool
of
water.
From
the
surface, we tend to
focus
on
the
separations of the
oceans in geographic
terms; the Atlantic is
distinct
from
the
Pacific is distinct from
the Arctic, and so on. From a heat reservoir and a "parcels of water with shared
characteristics" perspective, a major distinction is between the surface ocean and the
deep ocean.
In the tropics through mid-latitudes, sunlight provides a lot of heat to the uppermost
layers of the ocean. However, this warming sunlight only penetrates to depths of a few
tens of meters. The stirring action of wind-driven surface waves and the tides keeps the
uppermost layers of the oceans well mixed, so the heat provided by the Sun is
effectively distributed throughout the top few hundred meters of ocean water. However,
the deeper ocean, which contains about 90% of all ocean water, does not mingle much
with the surface layers. Sea surface temperatures range from slightly below freezing
near the poles to an annual average near 30° C in the tropics. Deep ocean
temperatures span a much more narrow range, between about 0° C and 4° C, and are
nearly uniform throughout the world's oceans. A fairly sharp transition between warmer
surface waters and the colder deep waters, called the thermocline, exists at depths of
a few hundred meters throughout most of Earth's oceans.
What significance does this separation between surface and deep ocean waters have
for climate change? Since the surface layer is exposed to the atmosphere, a warming
atmosphere can effectively transfer heat to the upper layers of the ocean. Although
water, due to its relatively high "thermal inertia", heats more slowly than air, we can
expect that increasing air temperatures will lead to warmer surface waters over time
scales of years to decades.
20
Of course, although surface and deep waters are not well-mixed, they do mix gradually
over longer timescales. A major ocean circulation system called the thermohaline
circulation (Global Ocean Conveyor Circulation) plunges cool surface waters into
the deep ocean, mostly in the North Atlantic and around Antarctica. The thermohaline
circulation eventually raises some of the deep ocean water to the surface; mostly in the
Pacific but also in the Indian Ocean. This round trip is not a quick one though; it
generally takes at least a couple hundred years, and can last as long as 1,600 to 2,000
years for water that makes the longer journey to the Pacific.
Heat and dissolved chemicals (including carbon dioxide from the atmosphere that
dissolves into sea water at the surface) do not necessarily have to travel with a parcel of
water as it makes the long journey to the deep ocean and back, but in many cases they
do. So warming (or cooling) of the deep ocean will likely occur on much longer
timescales than is the case for the ocean's surface layers, and on much, much longer
timescales than for the atmosphere. Global warming will heat the deep ocean very
slowly; but the deep ocean's recovery once we "fix" the problem (presuming we do!) will
also be extremely gradual, lasting many human generations. Effects that began early
during the industrial revolution in the 1800s are now being felt in the deep oceans. This
time lag between climate forcings and the reactions of Earth systems to those forcing is
a major feature of many aspects of global climate change that is of concern to
scientists. Policies that attempt to prevent or account for further impacts from climate
change need to take such lag times into account.
21
Salinity
Dissolved salts in ocean water make it taste salty. Fresh water has dissolved salts in it
too, but not nearly as many as ocean water! These dissolved salts can come from the
land, precipitation, or the atmosphere, and are particles that have completely mixed in
with the water.
Ocean water is about 3.5% salt. That means that if the oceans dried up completely,
enough salt would be left behind to build a 180-mile-tall, one- mile-thick wall around the
equator! And more than 90 percent of that salt would be sodium chloride, or ordinary
table salt. The oceans sure contain a lot of salt.
All over the globe and from the top of the ocean all the way to the bottom of the ocean,
salinity is between ~33-37 ppt or psu (average salinity of the ocean is 35 ppt). The
image shown on this page shows salinity measured at the surface of the ocean across
the globe. Almost the entire ocean is colored some shade of orange, corresponding to a
salinity measurement around 33-36 ppt or psu.
The oceans are naturally salty. Life in the oceans has adapted to this salty environment.
But, most creatures that live in the ocean could not live in fresh water. When the salty
waters of the ocean meet fresh water, an estuary is formed. This is a special
environment where some creatures have learned to adapt to a mixture of fresh and salt
water. Humans have the responsibility to make sure their actions are not causing
damage to these special environments where life thrives.
22
Density
The density of pure water is
1000 kg/m3. Ocean water is
more dense because of the
salt in it. Density of ocean
water at the sea surface is
about 1027 kg/m3.
There are two main factors
that make ocean water more
or less dense than about
1027 kg/m3: the temperature
of the water and the salinity
of the water. Ocean water
gets
more
dense
as
temperature goes down. So,
the colder the water, the more dense it is. Increasing salinity also increases the density
of sea water.
Less dense water floats on top of more dense water. Given two layers of water with the
same salinity, the warmer water will float on top of the colder water. There is one catch
though! Temperature has a greater effect on the density of water than salinity does. So
a layer of water with higher salinity can actual float on top of water with lower salinity if
the layer with higher salinity is quite a bit warmer than the lower salinity layer.
The temperature of the ocean decreases and decreases as you go to the bottom of the
ocean. So, the density of ocean water increases and increases as you go to the bottom
of the ocean. The deep ocean is layered with the densest water on bottom and the
lightest water on top. Circulation in the depths of the ocean is horizontal. That is, water
moves along the layers with the same density.
The density of ocean water is rarely measured directly. If you wanted to measure the
density of ocean water, you would have to collect a sample of sea water and bring it
back to the laboratory to be measured. Density is usually calculated using an equation.
You just need to measure the salinity, temperature and pressure to be able to find
density. These measurements are often made with a CTD instrument, where the
instrument is placed in the ocean water from a ship or a platform.
Pressure
Even though we do not feel it, 14.7 pounds per square inch (psi), or 1kg per square cm,
of pressure are pushing down on our bodies as we rest at sea level. Our body
compensates for this weight by pushing out with the same force.
23
Since water is much heavier than air, this pressure increases as we venture into the
water. For every 33 feet down we travel, one more atmosphere (14.7 psi) pushes down
on us. For example, at 66 feet, the pressure equals 44.1 psi, and at 99 feet, the
pressure equals 58.8 psi.
To travel into this high-pressure environment we have to make some adjustments.
Humans can travel three or four atmospheres and be OK. To go farther, submarines are
needed.
Animals that live in this watery environment undergo large pressure changes in short
amounts of time. Sperm whales make hour-long dives 7,380 feet (2,250 meters) down.
This is a pressure change of more than 223 atmospheres! By studying and
understanding how these animals are able to withstand great pressure changes,
scientists will be able to build better tools for humans to make such journeys.
Oceanic Oxygen
Oxygen at the surface is frequently high in the ocean, and the deep sea has abundant
oxygen in its cold water. A layer in between, in the mid-water or mesopelagic region, at
around 500 m may be low in oxygen. This oxygen minimum layer creates interesting
problems for mid-water species that are solved by both behavioral and biochemical
adaptations to low oxygen.
Recent Discoveries
In 1977, near the Galapagos Islands
in
the
Pacific
Ocean,
oceanographers discovered deep
sea vents and communities of
organisms never seen before. These
hydrothermal vents are located in
regions where molten rock lies just
below the surface of the seafloor,
producing underwater hot springs.
Volcanic "chimneys" form when the
escaping
superheated
water
deposits dissolved minerals and
gases upon coming in contact with
the cold ocean water. Around these
vents are bacteria that obtain energy
from the oxidation of hydrogen
sulfide escaping from the vents—a
process called chemosynthesis.
These bacteria (primary producers) are then used as food by tube worms, huge clams,
mussels, and other organisms (primary consumers) living around the vents. Since these
24
communities are not photosynthesis-based like all other biological communities, they
may provide clues to the nature of early life on Earth.
25
Activity: All That Glitters…
DuratioN: 2 hours
OBJECTIVES


Students will experiment with a model of what happens to light and colors as one
descends into the ocean.
Students will describe at least two adaptations to low or no ambient light on the
part of deep-sea organisms.
MATERIALS
For the teacher:
 3‖ x 5‖ card with 1-in slit cut in middle
 35 mm slide projector
 Prism
 Glow stick (from dive shops, fishing tackle or sporting goods stores or ―dollar‖
stores)
 One hole punch
 Optional: vial of ostracods from Carolina Biological Catalog: GR-20-3430; $32.80
Per student:
 Deep sea dive goggles made with: Blue plastic - blue plastic report covers or
blue color filter gel plastic; depending upon the ambient light in your room, you
will need 4-8 strips of plastic per goggle. Each strip should be about 8.5‖ x 3‖.
Blue color filter gels are available from Stage Light Louisiana LLC, phone (540)
818-1880; SLD Lighting, phone 800-245-6630, www.sldlighting.com; or check
your local yellow pages under ―Theatrical and Stage Lighting Equipment.‖ Ask for
Roscolux #80 primary blue, Lee #079 just blue, or Gam #850. These sheets are
24‖ x 20‖, producing 21 strips per sheet. Six sheets should produce 31 4-layer
goggles. Blue plastic report covers or index dividers are available from office
supply stores. Office Depot Insertable Index Dividers Item #455-801 is one
source for the color of blue needed for this activity.
 Elastic - about 12‖
 One ―regular‖ paper clip
 One ―binder‖ paper clip (the black and silver kind used for thick bundles of paper)
Per student pair:
 in red, orange, yellow, green, blue, black/dark brown, Sheet of black construction
paper or black craft foam
 ―Color in the Sea‖ Student Handout chart
26
BACKGROUND INFORMATION
This activity allows students to explore the nature of light, ask what happens to light as it
passes through the ocean and speculate on how deep-sea animals deal with living in
the dark. During the 2002 South Atlantic Bight Expedition,
Islands in the Stream, two scientists from the Harbor Branch Oceanographic Institution,
Dr. Tamara Frank and Dr. Edith Widder, studied vision and bioluminescence in the deep
sea. Of particular interest were animals with large eyes that live on the sea floor in the
aphotic zone. Many animals that swim in open water (pelagic) in the mesopelagic or
twilight zone have large eyes relative to their body size. Large eyes capture what little
light is available. As depth increases below the mesopelagic, eye size in many
organisms decreases. For example, two species of bristlemouths, Gonostoma
denudatum, a midwater fish, and Gonostoma bathyphilum, a deeper water fish, have
different eye sizes. The midwater species has much larger eyes. The deep water
species has much smaller eyes—the result you would expect if eyes had no value in the
total absence of light. However, an enigma exists. Many animals living on the deep-sea
floor sea have huge eyes! One possible value of vision where there is no ambient light
is that some deep-sea organisms make their own light—they are bioluminescent.
PROCEDURE
Teacher Prep
1. Cut a thin slit, just a few millimeters wide and about an inch long, in the card.
2. Tape a small piece of blue plastic over the light source. Ask students to note
what color is projected (blue). Make sure that students understand that the blue
plastic blocks part of the spectrum by absorbing colors of light other than blue.
3. Place prism in beam of light and practice rotating prism to project the colors of
the spectrum on the movie screen or white wall.
4. Cut the blue plastic into strips approximately 8.5 inches long by 3 inches wide.
5. Punch a hole in the middle of one end of every strip of plastic. Thread 4-8 sheets
of plastic through the regular paper clip. Tie one end of the elastic to this paper
clip. Tie the other end of the elastic to one of the silver ends of the binder clip.
6. Separate felt or foam squares by colors so that brown), red, orange, yellow,
green and blue.
Procedure
1. Ask your students to tell you what they know about light. Dim the lights and
project a visible spectrum on the wall. Have the students write down the colors
they observe in the order they see them in the spectrum. Review colors,
absorption and reflection.
2. Tape a small piece of blue plastic over the light source. Ask students to note
what color is projected (blue). Make sure that students understand that the blue
plastic blocks part of the spectrum by absorbing colors of light other than blue.
27
3. Challenge the students to observe what the underwater world looks like by using
Deep Sea Diving Goggles. Pass out the black paper or craft foam, Deep Sea
Diving Goggles, and foam or felt squares to each pair of students.
4. Explain that the black piece of paper represents the darkness of the deep sea.
Spread the felt or foam squares on the black paper.
5. Use only one layer of the Goggles to observe the colors of the foam or felt
squares. Add another layer and observe. Continue adding layers, simulating
what it looks like to go deeper into the ocean. What happened with each color?
The blue plastic enables students to see how colors appear in deeper water. The
blue plastic filters out other colors just as water absorbs them. Students should
observe that the color black disappears first, followed by red, then orange, then
yellow. Distribute the ―Color in the Sea‖ Student Handout chart to each student
group if you would like them to quantify their observations.
6. If they were fish wishing to hide in the mesopelagic twilight zone, what colors
would be the best camouflage? Black and then red
7. Introduce bioluminescence using the glow stick. Demonstrate ―turning it on‖—
shaking it makes it brighter as you are mixing the chemicals that produce light
when they react. Ask the students for their experiences with bioluminescence:
fireflies are the most common among eastern US students. Black light posters
are fluorescence—a very different process. Observe the glow stick with the
goggles on. How might deep-sea species use the light they make? Discuss
counter-illumination, finding a mate, finding prey, attracting prey and startling
predators by blinding them. What color would be the most effective for
bioluminescence —blue as it penetrates water most easily.
8. You may wish to go into detail about the chemical nature of bioluminescence if
your students have sufficient foundation. If you have the ostracods, place three to
five in your palm. Add two drops of water and crush the dried animals using a
finger. Show your palm; a bright blue results. When you crush the dried animals,
two chemicals mix to create blue light.
9. Visit the South Atlantic Bight OE expedition on the web or the OE CD and see
what the scientists were studying about bioluminescence.
28
29
Activity: Light at the Bottom of the Deep, Dark
Ocean
Duration: 2 hours
OBJECTIVES


Students will experience the impact of bioluminescence on finding food and
becoming prey in the deep ocean.
Students will be able to describe the positive and negative values of being able to
produce light.
MATERIALS
For the class:
 Long table in open space that can be made dark; push several tables together,
pull down shades and turn off lights; cover table with black paper
 Red, orange, yellow, green and blue 2 square cm. pieces of craft foam or felt.
For each student:
 Deep Sea Dive Goggles from All That Glitters; use hole punched at each end
and tie 18-inch strings (or use paper clips and very long rubber bands) in holes
so they may be worn hands free as a mask
 Small flashlight or glowstick
 Student worksheet
 Snack-size plastic bags

BACKGROUND INFORMATION
This exercise should be preceded by All that Glitters….It uses some of the same
equipment and assumes that the students have an understanding of light, light in the
ocean and bioluminescence. The students should have already worked with colors in
the ocean. Deep-sea fish use color to help hide—they may be camouflaged. Red is
good camouflage since red light disappears in shallow water. Black is also useful in the
dark. In this exercise students will apply what they have learned about color. Finding
food in the deep sea may be aided by use of bioluminescence—fish may have light
organs that illuminate the surrounding water, revealing prey. On the other hand, when a
fish lights up looking for prey, it exposes itself to predation by a larger fish.
Bioluminescence is an adaptation to life in the deep sea. It may be useful for
communication among members of a species, for attracting a mate, it may illuminate
prey or attract prey, and it is used for counter-illumination to obscure its outline against
the lighter surface. In this exercise, students will be deep-sea fish with light organs that
30
are used to illuminate prey so that they can eat them. They may also eat what they can
find in the dark. The teacher will be the large predatory gulper eel.
PROCEDURE
1. The day before this exercise, remind the students of what they learned in All that
Glitters… about light and color in the deep ocean. Suggest that they dress in
clothing that would make good camouflage in the deep sea for the next class.
Red or black would be best, with long sleeves and good coverage, but do not tell
them this—leave it up to them. Students wishing to go to extremes might choose
to bring a face covering ski mask. For this activity they will be modeling the
behavior of deep-sea fish that feed using bioluminescence.
2. To do this exercise, select the first set of students; give them flashlights, plastic
bags and goggles. Spread felt or foam squares thinly on the black paper on the
tabletop and tell them this is their food. They must find it in the dark, wearing the
goggles. They are fish living in deep water where there is very little light. They
may use the flashlight, their bioluminescent organ, to look for food, but whenever
it is on, you may tag them because they are visible to a predator—you. When
you tag them, a gulper eel has eaten them. They may only use one hand to
collect food—using their thumbs and forefingers to pick up one item at a time and
place it in their bag. Students not playing will watch to make sure the rules are
followed. Anyone being rowdy loses.
3. With goggles in place, dim the lights and let the students begin feeding. If they
can see the prey, they may feed without the light, but the light will illuminate
almost invisible items. Play until you have tagged about 1/2 of the students.
Repeat with another group. The students may keep their bags when tagged.
They just have to stop eating.
4. Have the students evaluate the contents of their bags for colors selected. Add up
all the felt or foam squares eaten by color versus those left on the table by color.
5. Allow all students time for reflection by having each student fill out the Student
Worksheet. Then have a class discussion about the questions.
31
32
Activity: Density Currents
Duration: 2 Hours
Objective

Students work in small groups to experiment with currents caused by
temperature variations that simulate the origins and flow of polar bottom currents.
Materials










rectangular container (glass dish, plastic shoebox or storage container)
4 small thermometers (to fit in plastic container)
cup (paper or plastic) with pinholes in bottom
tape
food coloring
crushed ice
eye dropper
paper, small approx. 1/2‖
tap water
Procedure
(see illustration - next page)
1. Divide class into small groups of 3 - 4 students. Have one student get supplies
and equipment.
2. Students tape cup in one corner of rectangular container, about one inch from
the bottom.
3. Tape 4 thermometers in bottom of dish, all oriented in same direction with equal
spacing.
4. Add water to the container, so the bottom of the cup is covered. Let water settle.
5. Record the temperature on all 4 thermometers at the start of the experiment, or
time = 0.
6. Place ice in the cup and add 10 drops of food coloring.
7. Record the temperatures again every 5 minutes for ½ hour on the data sheet.
8. Observe what happens by looking though the side of the dish at table level.
Record your observations by making a small sketch or diagram of what you see,
and explain what you think causes what think causes this.
9. NOTE: If you can not see a bottom current, heat the corner opposite the ice by
placing a beaker of hot water in the dish.
10. At the end of 30 minutes place a small piece of paper (1/2 inch square) on top of
the water in the corner opposite the ice.
33
34
Questions
1. The paper moves in which direction? (toward ice)
___________________________________________________________________
_________________________________________________________
2. What does the paper represent, a surface or deep current? (surface)
___________________________________________________________________
_________________________________________________________
3.
the ice)
___________________________________________________________________
_________________________________________________________
4. Which thermometer changed the fastest? (nearest the ice)
___________________________________________________________________
_________________________________________________________
5.
___________________________________________________________________
_________________________________________________________
6.
___________________________________________________________________
_________________________________________________________
7. Explain what happened to cause the changes in the 4 thermometers’
temperatures. (cool water sank and flowed across the container while the warm
surface water flowed toward the cup.)
___________________________________________________________________
_________________________________________________________
8. What can we learn from the movement of the colored water? (It traces the
movement of the water current across the bottom.)
___________________________________________________________________
_________________________________________________________
9. What does your cup of ice imitate in the real world? (polar sea ice)
______________________________________________________________
______________________________________________________________
35
10. How does cooling affect the density of water? (Cold water is denser than warm
water.)
___________________________________________________________________
_________________________________________________________
11. Where would you find cold water currents in the ocean? (Moving away from the
polar regions in the deep ocean)
___________________________________________________________________________
_______________________________________________________________
36
Activity: Finding the Deep Water
Masses of the Atlantic Ocean
Objective

Students will be able to describe the role of density in driving deep ocean
currents and the density layers of the ocean.
Materials




water masses data table
temperature - density - salinity graph
water masses worksheet (on cross section of the Atlantic)
Atlantic ocean map and cross section
Procedure
1. Complete the Water Masses Worksheet and Water Masses Data Table as
instructed.
2. Start by matching the temperature and salinity for each water mass to find
the density ( st ) using the Temperature-Density-Salinity graph. Record
these densities on your Water Masses Worksheet (Cross Section of the
Atlantic Ocean).
3. Next, on the Water Masses Data Table, match the latitude, temperature
and salinity to find the density ( st ) and the name of each water mass.
4. Last, fold the page with the Atlantic Ocean Map and Atlantic Ocean Cross
Section 90O to get a three dimensional view of the water masses and their
origins. This will help you answer the Evaluation questions on the next
page.
Key to Water Mass Abbreviations
NADW = North Atlantic Deep Water
MI = Mediterranean Intermediate
SW = Surface Water
AAIW = Antarctic Intermediate Water
AABW = Antarctic Bottom Water
Finding the Deep Water Masses from the Atlantic Ocean
37
38
39
40
Questions

If a person had a very long fishing line, why might it be possible to catch an
Antarctic species of shark while fishing at the Equator?
___________________________________________________________________
__________________________________________________________________

Wind driven surface currents travel at approximately one kilometers per hour,
while density driven deep ocean currents travel much slower, about one meter
per hour. How long would it take Antarctic Bottom Water to travel to the North
Atlantic sample site at 45ON, approximately 9,000 km from its Antarctic source
area?
___________________________________________________________________
___________________________________________________________________

What relationships can you describe between water temperature and salinity at
the 0O sample site?
___________________________________________________________________
___________________________________________________________________
 What happens to the water density at the 45ON sample site?
___________________________________________________________________
___________________________________________________________________

From the Temperature-Density-Salinity Graph, what happens to the density of
seawater at temperature increases? As the temperature decreases the density of
the seawater does what?
___________________________________________________________________
___________________________________________________________________
 What factor(s) increase sea surface water density at high latitudes?
___________________________________________________________________
__________________________________________________________________

What factor(s) cause the density of the surface water in the low latitude regions
to increase?
___________________________________________________________________
___________________________________________________________________

Explain why density driven circulation in the ocean depths is caused by the
interaction of the atmosphere and the ocean.
___________________________________________________________________
___________________________________________________________________
41

Why the sun is considered the source of energy for driving the density circulation
in ocean depths? Explain
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
42
Activity: Aquatic Autobiography
Duration: 3 Days
Materials




Index Cards
Poster board or Butcher paper
Art supplies
Access to library or computer with internet access
Procedure
1. Give each student an index card and ask them to write down their definition of a
2.
3.
4.
5.
6.
habitat.
 Collect the cards and read a few of them out loud.
 Ask students if any of those definitions are correct.
Give students the following definition and example of habitat (you can read it or
ask for a volunteer):
 An animal’s habitat is the place where it lives, finds food, defends itself
from predators, finds a mate and reproduces. Most animals confine their
activities to a particular kind of habitat where they are most successful at
fulfilling their needs. For example … oysters populate areas where there
is a suitable flow of oxygen-filled water, an abundant supply of plankton to
serve as a food source, and a hard surface to settle on.
Remind students of the definition of the word adaptation.
 Reread the definition and ask students to identify the adaptations that
would allow an oyster to survive in the habitat described.
Introduce the different ocean zones with the class
 Be sure to include the characteristics of each zone and example of the
types of organisms that live in each.
 Have students ID some of the special adaptations organisms would need
to survive in each zone.
Break students into groups of 3-5 students. Explain to students that they will
have the opportunity to investigate further investigate an organism from one of
the ocean zones.
 Assign each group a zone to focus on
 Give each group some time to do some research and to select an
organism from that zone
Students should address the following questions as they continue their research:
 What does the organism look like?
 What are some special features of the assigned ocean zone/habitat?
 What are some of the organism’s special characteristics or adaptations?
How does it eat? How does it protect itself? Etc.
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
What are the different life cycle stages of the organism? Does the
organism live in this zone for its entire life? If not, where else does it go?
How do its adaptations change based on its life cycle?
 What else is unique and interesting about this organism?
7. Once groups have completed their research, ask each group to write an
autobiography for their organism.
 They should include life history information, as well as daily interactions
with abiotic and biotic factors in their habitat.
 Students should create a book or poster board detailing their
autobiography.
8. Ask each group to present their final project.
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Activity: Temperature Changes: Atmosphere &
Ocean
Duration: 1 hour
Objective

Students observe temperature differences of water and air in sunlight and
darkness.
Materials



2 thermometers
2 quart- size jars with lids
water
Procedures
1. The teacher puts a thermometer in each jar, fills one jar with water and caps both
jars. Label the water jar ―ocean‖ and the empty jar ―atmosphere.‖ Record the
temperature of each on the board. Place the jars next to each other in the
sunlight for about ½ an hour.
2. Ask the students: What do they think will happen in each jar? (write in journal)
3. Which thermometer will rise quicker? Why?
4. After ½ hour record the temperatures on the board next to the first temperatures.
5. Ask the students: Which jar is hotter?
6. Which jar showed the greatest change in temperature?
7. The teacher now places the jars in the shade for about ½ hour.
8. Ask the students: Which container will cool the fastest? What do you think?
Why? Chart data in journal.
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9. After ½ hour record the temperatures. Find the difference between the new and
previous high temperature of each jar. Have students generalize about what is
happening to the atmosphere and ocean. (Water heats and cools slower than
air.)
Questions
1. In the winter, would the average temperature of the ocean or the air be warmer?
Why? (Winter has warmer ocean temperatures than air temperature).
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
__________________________________________________________________________
2. How would the summer ocean temperature differ from the air temperature?
(Summer has warmer air temperature than the cooler ocean temperature.)
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
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Activity - Deep Ocean Currents
Duration: 1 hour
Objectives

Students observe the interactions of different temperatures of water using
colored ice and a thermometer and then compare the results with global ocean
current solar heating.
Materials








world maps
activity sheets
clear glass
water – cold tap
water – hot tap with 2 drops of red food coloring
ice cubes frozen with 15 drops of green food coloring
aquarium thermometer
spoons
Procedures
1. Each group of 3-4 students obtains 1 clear glass filled ¾ full of cool tap water.
2. Students place an aquarium thermometer in the glass. Wait 2 minutes, then record
the temperature.
3. Students obtain an ice cube and place in the water, using a spoon.
4. Students observe the glass, draw the glass, and explain what is happening.
5. Wait 2 minutes and record the temperature.
6. Students obtain ¼ glass of hot colored tap water and gently pour the water down the
inside edge of the glass. Don’t disturb the rest of the water.
7. Students observe the glass, draw the glass, and explain what is happening.
8. Wait 2 minutes and record the temperature.
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Questions

Was the colored water moving away from the ice cube colder or warmer than the
water in the glass? (cooler)
______________________________________________________________________
______________________________________________________________________

Was the warm colored water that was added colder or warmer than the water in the
glass? (warmer)
______________________________________________________________________
______________________________________________________________________

Where would floating ice be found in the ocean? (near the poles)
______________________________________________________________________
______________________________________________________________________

Where would cold water be found? ( poles and in the deep ocean)
______________________________________________________________________
______________________________________________________________________

Where would cold water flow in the ocean? (at the bottom) Why?
______________________________________________________________________
______________________________________________________________________

Where would you expect to find the warmest waters in the ocean? (near the equator
and at the surface)
______________________________________________________________________
______________________________________________________________________

Where would warm moving water flow in the ocean? (near the surface) Explain.
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________

Which direction would cold water move in the ocean? (down and toward the equator
where it is heated)
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______________________________________________________________________
______________________________________________________________________
______________________________________________________________________

Which direction would warm water move in the ocean? (up and toward the poles,
where it cools.) _____________________________________________________

Scientists have found that water in the ocean is well mixed. How do differences in
temperatures
mix
ocean
waters?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
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Worksheet: Deep Ocean Currents
Temperature of cool tap water ______________________________________
What happens after adding the ice cube? Describe in words and draw a picture of
the glass.
Temperature of water with the ice cube in it ___________________________
What happens after adding the warm water?
picture of the glass?
Describe in words and draw a
Temperature of water with warm water added _________________________
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Resources
http://www.seasky.org/deep-sea/ocean-layers.html
http://www.scienceclarified.com/Mu-Oi/Ocean-Zones.html
http://weirdnewsfiles.com/tag/ocean-glow/
http://www.onr.navy.mil/focus/ocean/water/pressure1.htm
http://www2.ec.gc.ca/chocolate.en.experiment_e.htm
http://oceanexplorer.noaa.gov/edu/curriculum/section5.pdf
http://www.msc.ucla.edu/oceanglobe/pdf/climatecurents/currentsentire.pdf
http://www.cutter.com/osir/primer.htm
www.wikipedia.com
All images are taken from Google Images.
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