Ecology: the study of how organisms interact with
each other and their environment.
Ocean Ecology
Symbiotic Relationships
Symbiosis: any relationship where two species live closely
together.
There are 3 types of symbiotic relationships
1. Mutualism: A
relationship that
benefits both
organisms involved.
Why does the eel not eat
the tiny shrimp?
Symbiotic Relationships
2. Commensalism: A
relationship where
one organism benefits
and the other is
unaffected.
3. Parasitism: A relationship
where one organism
(parasite) benefits and
the other organism (host)
is harmed.
Symbiotic Relationships
• Predation: the consumption of one organism (the prey)
by another (predator)
– One organism is benefited and the other is harmed.
– How is predation different than symbiosis?
– The energy from the prey is transferred to the predator.
Marine Lifestyles
Types of Organisms based on
Lifestyle
• Plankton: organisms that
float in the ocean and rely
on currents to move from
place to place.
– Phytoplankton:
organisms that float and
photosynthesize.
– Zooplankton: organisms
that float in the ocean but
do not photosynthesize
(the eat other organisms)
Marine Lifestyles
• Nekton: organism that can
swim well enough to oppose
ocean currents.
– Ex: Fish, whales, sea
turtles, squid.
• Benthos: organism that live
on or buried in the bottom
of the ocean.
– Ex: Crabs, starfish, coral,
seaweed
Energy Flow in a Marine Ecosystem
Organisms Based on Feeding Relationships
• Autotrophs (Primary Producers): make
their own food through photosynthesis or
chemosynthesis.
• Heterotrophs (Consumers): obtain
energy by feeding on producers or other
consumers.
– Primary Consumers: eat primary
producers
– Secondary Consumers: eat primary
consumers
– Apex Predators: top of the food chain,
has no predators
Energy Flow in a Marine Ecosystem
• Food Chain: Shows the flow of energy
from one organism to another.
– Energy moves from producers to
primary consumer to secondary
consumer, etc.
• Trophic Levels: any class of organisms
that occupy the same position in a
food chain
– How many trophic levels are in the
food chain?
Energy Flow in a Marine Ecosystem
• Ecological pyramids: an illustration of the reduction in
energy as you move through each trophic level in an
ecosystem.
– What % of energy is passed from one trophic level to
the next?
What is the ultimate
source of energy in this
ecological pyramid?
Energy Flow in a Marine Ecosystem
• What happens as you move up the food chain?
– Energy
– Size of the organisms
– Population Size
Energy Flow in a Marine Ecosystem
• Food web: interconnected food chains in an ecological
community
What will happen
to the killer whales
if the disappeared
from the
ecosystem?
How will an
increase in leopard
seals affect the krill
population?
Photosynthesis in the Ocean
Autotrophic organisms make up
the bottom every food chain.
• Most autotrophic organisms
are photosynthetic
• Phytoplankton accounts for
the majority of photosynthesis
on the Earth
• Other photosynthetic
organisms in the ocean
include sea grasses and
seaweed.
Photosynthesis in the Ocean
Seagrass
• The only type of plant that can
survive in the ocean.
• Grows in shallow water with a
muddy or sandy bottom.
• Structure of Seagrass:
– Roots: anchor plants in sand
or mud and absorb nutrients.
– Stems: supports the plant,
spreads horizontally
underground.
– Leaves: absorb sunlight for
photosynthesis.
Photosynthesis in the Ocean
Seaweed
• A type of algae.
• Grows in shallow water that has a
rocky bottom
• Structure of Seaweed
– Holdfast: helps the seaweed
grip the hard ocean bottom.
– Stipe: supports the seaweed.
– Blade: collect sunlight for
photosynthesis.
– Pnuematocysts: gas-filled
structures that help the blades
float.
Photosynthesis in the Ocean
Photosynthetic organisms
provide heterotrophs with
energy and oxygen.
• Oxygen Minimum Zone: the
layer of water where there is
the least amount of oxygen
available.
– Above: high levels of
oxygen because there is a
lot of photosynthetic
organisms near the
surface.
Photosynthesis in the Ocean
– In the oxygen minimum zone:
it is too dark for
photosynthesis but there are
heterotrophs removing oxygen
for respiration.
– Below: there is no
photosynthesis and very little
respiration. Downwelling adds
oxygen to deep water.
– What are the equations for
photosynthesis and
respiration?
Nutrient Cycles
• Carbon is absorbed from
the atmosphere as CO2.
• Dissolved CO2 is absorbed
by autotrophs and used in
photosynthesis to make
sugar.
• Autotrophs respire and
the carbon in the sugar
becomes CO2 dissolved in
water.
• If the autotroph is eaten
by a heterotroph carbon is
passed through the food
chain until it is released by
respiration or death.
Nutrient Cycles
• Organisms need
phosphorous to make
organic molecules like
DNA.
• Phosphorous is added to
ocean water through
eroding rocks and
fertilizer runoff.
• Phosphorous is absorbed
by autotrophs.
• Heterotrophs eat
autotrophs to obtain
phosphorous.
• Once any organism dies
the phosphorous either
dissolves in the water or
becomes fossilized in
sediment
Nutrient Cycles
• Living things need
nitrogen to make proteins
and DNA.
• Most nitrogen exist as
nitrogen gas (N2) in the
atmosphere which most
living things cannot use.
• Nitrogen fixing bacteria:
the only organism that
can take nitrogen gas (N2)
and convert it into a form
that can dissolve in water
Nutrient Cycles
• Fertilizer from farms and
eroding rocks increase the
amount of dissolved
nitrogen in the ocean.
• Dissolved nitrogen starts
out as ammonia (toxic).
• Bacteria converts
ammonia into nitrite
(toxic) and then nitrate
(safe).
• Nitrate is the only
compound that is not
toxic and can be used by
autotrophs.
Nutrient Cycles
• Nitrogen is passed to
heterotrophs when the
autotrophs are eaten.
• Nitrogen is released
from heterotrophs
through releasing
waste or death and it is
dissolved back into
water.
• Denitrifying Bacteria:
Converts nitrogen
dissolved in the ocean
into nitrogen gas in the
atmosphere.
How Populations Grow
Exponential Growth: When a population grows at a constant
maximum rate.
• Small populations grow slowly
• The larger the population the faster it grows.
• Requires ideal conditions and unlimited resources.
Ex: One plankton cell
reproduces every 20
minutes. Assume
unlimited resources . . .
– How many plankton after 1
hour?
– How many plankton after 2
hours?
– How many after one day?
How Populations Grow
Logistic Growth: The rate of population grow decreases and
eventually stops due to a limiting factor.
• Carry Capacity: The maximum population size an
ecosystem can support.
• Limiting factor: any biotic or abiotic factor that prevents a
population from becoming too large.
• Explain why the rate
of population growth
changes over time.
Nitrogen in Atmosphere
Denitrifying
Bacteria
Nitrogen-Fixing
Bacteria
Nitrate
Nitrogen in Fertilizer
and Rocks
Erosion and
Agricultural
Run-Off
Forms of Dissolved
Nitrogen
AA
Nitrite
Ammonia
Waste
Absorbed
Autotrophs
Dissolves
(Converted by Bacteria)
Consumed by
Heterotrophs
Death
Death
Detritus