Download The Benthic Zone

The Benthic Zone
The ocean can be divided in two general zones:
1. Pelagic Zone: The open ocean
2. Benthic Zone: The ocean floor
6 different regions of the benthic zone:
• Rocky Shores
• Sediment Covered Shores
• Subtidal Continental Shelf
• Coral Reefs
• Deep Ocean Floor
• Polar Ice
Rocky Shores
• Vertical Zonation: The
banded pattern formed
by organisms living at
different levels on rocky
shores.
• The are 3 major zones
depending on how
frequently it is covered
with water.
1. The upper tide zone
2. The middle tide zone
3. The lower tide zone
Rocky Shores
The upper tide zone
• Mostly dry, only covered in water during
high tide.
• Adaptations: Run and Hide
– Organisms often find a wet place to hide
until the tide rises.
– Ex: Crabs
Rocky Shores
The middle tide zone
• Is above and below the water line for equal
amounts of time.
• Adaptations: Clam Up
– Organisms usually have a shell that close
up to seal in some water.
– Ex: Mussels
Rocky Shores
The lower tide zone
• Covered in water most of the time and only
exposed to air during the lowest tides.
• Adaptations: Sit and Bare It
– Organisms can survive with some water
loss.
– Ex: Seaweeds
Sediment Covered Shores
Sediment Covered Shores: shores covered with gravel, sand,
silt or clay.
• There are two basic types of sediment covered shores
– Sandy beaches
– Muddy Salt Marshes
Wave energy determines the type of sediment covered
shore.
Sediment Covered Shore
Sandy Beaches can divided up into 2 zones
1. The intertidal zone
– The mostly dry region of the sandy beach
– Adaptations: Organisms prevent dehydration by
burrowing in the sediment.
Infauna: Animals that live in the sediment
Meiofauna: Animals that are so small that instead
of burrowing they live in the spaces between the
grains of sediment.
Sediment Covered Shore
2. The subtidal zone
– The region of the sandy beach that is mostly covered
in water.
– Adaptation: These organisms do not usually burrow.
Why not?
Epifauna: animals that live on the surface of the
sediment and do not burrow.
Sediment Covered Shores
Muddy Salt Marshes can be divided into 3 zones:
1. The Lower Mud Fat: completely covered at high
low, helps circulate nutrients and detritus.
2. Cord Grass Area: cord grass provides shelter and
food for many smaller marine organisms.
3. Transition Zone: the area where the muddy salt
marsh mixes with other land plants.
Sediment Covered Shores
Adaptations for feeding
in muddy salt
marshes:
• Organisms in the mud
flat tend to be deposit
feeders and not filter
feeders.
– Filter Feeders: have
adaptations to filter
food out of the water.
– Deposit feeders: eat
food that has settled
to the bottom.
Sediment Covered Shores
• Why are organisms in the mud
flat usually deposit feeders?
1. Finer sediments clog up the filter
feeder’s nets
2. There is a large amount of
detritus that settled on the mud.
The Subtidal Continental Shelf
Subtidal continental shelf: the area
extending from the lowest tidal
edge of rocky and sediment
covered shores to the abyssal
plain
• The subtidal continental shelf can
be divided into two main regions:
– Soft Bottom Community: covered
with sand or mud.
– Hard Bottom Communities: covered
with rock or the hard skeletons of
various marine invertebrates.
The Subtidal Continental Shelf
• Feeding in the Soft bottom subtidal
communities
– Primary production in the soft
bottom continental shelf is due
mostly to sea grass which has
roots that can anchor
themselves to the soft bottom
– Most organisms of the soft
bottom subtidal region feed on
detritus through deposit or
suspension feeding
The Subtidal Continental Shelf
• Feeding in the hard bottom subtidal communities
– Hard bottom subtidal communities are much more
productive than soft bottom community
– Kelp beds are especially common in cold waters,
these 100 foot long seaweeds form environments
not unlike rainforests
– Sea urchins are the most important grazers in the
hard bottom subtidal community keeping the kelp in
check.
Coral Reefs
Coral: a collection of small, sessile marine
invertebrates.
• Secrete a hard limestone skeleton that
builds up other many generations to for a
coral reef.
• Most coral have zooxanthella (small
photosynthetic organisms) that live inside
their bodies.
– The zooaxanthella provide nutrients to
the coral
– The coral provide protection to the
zooanthella
– What type of symbiotic relationship
exists?
3 Types of Coral Reefs
1. Fringing reefs: a coral reef that develops as a
narrow band close to or against a shoreline
– Because fringing reefs are so close to the shore
they are subject to more extreme conditions such
as sediment build up and exposure at low tide,
both of which could kill the coral
3 Types of Coral Reefs
2. Barrier reefs: coral reefs that develops a
distance away from the shoreline and thus has a
lagoon.
•
Lagoon: the body of water between a barrier reef
and the coast.
Sand cay: an island formed
by wave pushing sediments
on top of reefs.
Ex: Florida Keys
3 Types of Coral Reefs
• Atolls – rings of reefs that enclose
a lagoon
– Atolls are home to the most brilliant
and dramatic coral growth
– they are out in the middle of the
ocean, and not subject to harsh
conditions created by being close to
land
– All other types of coral reefs need
land and shallow water to form.
• It was a mystery as to how rings of
coral islands can form in the
middle of the ocean
3 Types of Coral Reefs
• Formation of atolls:
– First a fringing reef forms around a
volcanic island
– A barrier reef then forms as the
volcano goes extinct and starts to
erode away from the reef, creating a
lagoon between the reef and the
island.
– Eventually the island sinks
altogether leaving only a ring of
living growing coral – an atoll
Feeding Adaptations in Coral Reefs
• Coral must be adapted to survive waters low in nutrients
– Nutrient recycling:
• Coral releases CO2, nitrates and phosphates.
• Zooxanthellae absorbs CO2, nitrates and phosphates
to produce sugars and oxygen.
• The coral absorbs the sugar and oxygen and then
releases CO2, nitrates and phosphates.
Adaptations in Coral Reefs
Competition for Space
– With so many different organisms
inhabiting such a small area, space is at a
premium for corals as well as fish.
– Adaptations:
• Grow upwards and then branch out to
block out light for neighboring corals.
• Some coral have long tentacles to sting
neighbors
• Some corals can detach themselves
and move to a new location.
Deep Ocean Floor
Abyssal Plain: the large flat
region of the ocean floor
covered with sediment.
– There is virtually no light that
reaches the deep ocean floor.
– There are no photosynthetic
organisms to form the basis of
the food web.
– All primary productivity on
the deep ocean floor comes
from chemosynthetic
bacteria.
Deep Ocean Floor
The are 3 areas of the deep ocean
floor where chemosynthetic
bacteria can be found:
1. Deep sea hydrothermal vents (Black
smokers): undersea hot springs
associated with the mid ocean ridge.
• Releases hydrogen sulfide and
natural gas, very hot.
What is a mid ocean ridge?
Deep Ocean Floor
2. Cold seeps: areas of the deep
ocean floor where hydrogen
sulfide and natural gas have
seeped out of the ocean floor
and settled in a low spot.
– Similar to hydrothermal
vent, but much colder
3. Dead bodies: dead whales and
other organisms that have
settled on the deep ocean
floor
Adaptations on the Deep Ocean Floor
Adaptations of the Abyssal Plain:
• Most organism on the abyssal plain
are deposit feeders that eat dead
organism that sink to the ocean floor
from the surface.
– Ex: Sea cucumbers, Brittle Stars
• Predation is rare, but there is some . . .
– Predators usually have very large
mouths
– Adapted to hunt in low light
Adaptations on the Deep Ocean Floor
Adaptations for living near deep sea hydrothermal vents:
• Deep Sea Chemosynthetic Bacteria: bacteria that has
adapted to take in hydrogen sulfide emitted from
hydrothermal vents and covert it to food
―forms the basis for the deep sea food web
Adaptations on the Deep Ocean Floor
• Dominant animal near hydrothermal
vents is a giant tube worm.
―Chemosynthetic bacteria live inside the
giant tube worm and produce food for
the worm.
―The tube worm collects hydrogen
sulfide for the chemosynthetic
bacteria.
―What type of symbiotic relationship
exist between the tube worms and
chemosynthetic bacteria?
Adaptations on the Deep Ocean Floor
Adaptations for living near cold seeps
• Similar to hydrothermal vents
• Chemosynthetic bacteria form mutualistic relationships
with clams and mussels.
• Water is much colder and more dense.
Adaptations for the Ocean Floor
Adaptation for living on dead bodies
• Decaying organism produce hydrogen sulfide which
creates communities like those seen in hydrothermal
vents and cold seeps.
• Hydrothermal vents and cold seeps eventually “die”
and stop producing hydrogen sulfide.
• Organisms then must find another source of
hydrogen sulfide to survive.
• Dead bodies acts as stepping stones for organisms as
they find new vents and cold seeps.
The Polar Region
Two Polar regions of the Earth:
Arctic
Antarctic
Polar Adaptations
Organism have evolved adaptations to survive the
cold temperatures and obtain energy.
Adaptations to Obtain Energy
• Sympagic Organisms: form
tunnels in the ice in which
they live.
– Bacteria and phytoplankton
also live in tunnels (primary
producers)
Polar Adaptations
• Seasonal Algal Blooms
– Ice melts in the summer, and
phytoplankton up end up in
the ocean.
– In the summer the ice is
thinner = more sunlight
reaches the water = equal algal
bloom
– Organisms near the surface
consume the phytoplankton.
– Dead organisms sink to the
bottoms feed the benthic
organisms
Polar Adaptations
Adaptations to Cold
• Antifreeze proteins:
– Polar fish often survive in water that is below
freezing.
– Why do freezing temperature of destroy cells?
– Antifreeze proteins prevent ice crystal from
forming in the fish’s cells.
Polar Adaptations
• Body Shape
– Marine mammals have a
cylindrical body shape
with small appendages.
– Reduces the surface area
to volume ratio
– The smaller the SA/V to
longer it takes to heat up
and cool down.
• Blubber
Polar Adaptations
– A thick layer fat just below the skin.
– Acts as insulation from the cold.
– Explain why blubber is better insulator than fur for
diving marine organisms.
– Stores energy
Polar Adaptations
Explain how migration can be both an adaptation
form the cold and an adaptation to obtain
energy.
Short Answer Questions
• Explain how an atoll is formed in the middle of
the ocean. Use the following terms in your
answer: lagoon, guyot, fringing reef, barrier
reef, island.
• Explain how reducing the number of sea
otters will be harmful to the kelp forest.
• Explain how the relationship between the
chemosynthetic bacteria and giant tube
worms are similar to the relationship between
coral and zooxanthellae. How are they
different. (2 similarities and 2 differences)
Short Answer Questions
• Explain how reducing the number of sea
otters will be harmful to the kelp forest.
Short Answer Questions
• Explain how the relationship between the
chemosynthetic bacteria and giant tube
worms are similar to the relationship between
coral and zooxanthellae. How are they
different. (2 similarities and 2 differences)