Part 4: Ocean Life Zones
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Factors that Affect Life in the Ocean
1. Amount of sunlight
2. Temperature of the water
3. Water pressure
 How does depth affect each of these?
 Where would you expect to find the
greatest abundance of organisms?
2
Three Major Groups of Organisms
 Grouped according to
their habits and where
in the water they live
1. Plankton - floaters
2. Nekton - swimmers
3. Benthos – bottom
dwellers
3
Plankton
 Float at or near the
surface (up to 200 m
deep in open ocean)
 Plankton comes from the
Greek word planktos
that means drifting
 Many are microscopic
 Foundation of the ocean
food web
Whale shark eating plankton
http://commons.wikimedia.org/wiki/File:Whale_shark_eating_plankton.JPG
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Plankton
 Phytoplankton,
primarily diatoms and
dinoflagellates along
with brown algae and
cyanobacteria, use
photosynthesis to make
food.
 Source of food for
zooplankton
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Plankton
 Zooplankton includes
animal-like protists
(radiolarians,
forminiferans, ciliates
and zooflagellates),
jellyfish, siphonophores
such as the Portuguese
man-of-war, and
copepods and krill (two
types of crustaceans)
Krill
Copepod
Photo credit: Jamie Hall, NOAA
photo by Uwe Kils
Model of a radiolarian at
the Smithsonian Museum
Photo by Hofikai
http://www.flickr.com/photos/23165290@N00/7282108674
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Nekton
 All the organisms that
swim freely in the ocean,
independent of current
 Live in shallow or deep
water
Video of nekton in the depths
of the ocean:
http://ocean.si.edu/oceanvideos/sea-creatures-deep-videonational-geographic-and-censusmarine-life
Three main types:
 Cordates - bony fish,
whales, sharks, turtles,
snakes, eels, porpoises,
dolphins and seals
 Molluscan – octopus and
squid
 Arthropods - shrimp
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Nekton
Great White Shark
Photo by Irvin Calicut
Bottlenose Dolphin
A young loggerhead sea turtle
Common Octopus
Photo by Albert Kok
A Caridean Shrimp- moves
primarily by swimming
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Benthos
 Organisms that live on
the ocean floor
Includes:
 Plants - seagrass
 Many invertebrate
animals – sea stars, sea
anemones, sponges, sea
urchins, oysters, clams,
crabs, sponges, coral, etc.
 Protists – brown, red,
and green algae
(seaweed)
Sally Lightfoot Crab
Photo by Peter Wilton
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Major Life Zones
Three major environments or life
zones:
 Intertidal
 Neritic
 Open-Ocean




Photosynthetic Zone
Bathyal
Abyssal
Hadal
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Intertidal Zone
 The region between high
tide and low tide
 Most changeable zone
 Varies back and forth
from dry to under water
twice a day
 Organisms must also
withstand the affects of
waves breaking on the
shore.
Photo Credit: Eric Guinther
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Intertidal Zone
 Many organisms attach
themselves to rocks so as to
avoid being washed out to
sea.
 Others burrow into the wet
sand
 Starfish, barnacles,
anemones, seaweed, sea
urchins, clams, mussels,
hermit crabs, etc. live here.
A beautiful array of starfish , sea urchins
and mussel shells in the rocky intertidal
zone of Kachemak Bay.
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Neritic Zone
 From low-tide line to edge




of continental shelf, down
to about 200 meters
Also called coastal waters
Plenty of sunlight for
photosynthesis
Plankton, nekton, and
benthos all found here
Richest life zone in the
ocean
A close-up of a small mass of sargassum
weed. The numerous small round spheres
are floats filled with carbon dioxide. These
provide buoyancy to the algae.
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Open-Ocean Zones
Photosynthetic Zone –
 Extends from the ocean surface to
approximately 200m
 Sunlight penetrates the entire zone
 Plankton and nekton live in this zone
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Open-Ocean Zones
Bathyal Zone:
 Begins at continental slope
and continues to depths of
about 2,000 meters
 Water temperature about
4°C
 Little if any light, so no
photosynthesis
 Many forms of nekton live
here including whales,
squids, and octopuses
 Benthos organisms also
live here, including
sponges and sea stars
 Great biodiversity in this
zone
Sperm Whales
Photo credit: Réunion Underwater Photography
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Open-Ocean Zones
Skeleton of a Glass Sponge
Abyssal Zone:
 2,000-6,000 meters
 No sunlight
 Great pressure
 Temperature 2-4°C
 Creatures that live here
may be blind or
bioluminescent
Giant Squid
Photo: NTNU Museum of Natural history
and Archeaology
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Open-Ocean Zones
Hadal Zone:
 Very deepest parts of the
ocean, below the abyssal
zone
 Totally dark
 Immense pressure
 Creatures removed from
this zone will die in the
lower-pressure areas
above.
 The most common
creatures found here
include jellyfish, viperfish,
tube worms, sea
cucumbers and deep sea
angler fish.
 Video:
http://www.telegraph.co.u
k/earth/earthvideo/916881
7/James-Camerons-firstfootage-from-thedeep.html
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