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Standard Two:
Biological Productivity
and Energy Transfer
© 2011 Pearson Education, Inc.
Overview
• Productivity is the same as
photosynthesis, which is affected by
sunlight and nutrients.
• Productivity is globally and seasonally
variable.
• Feeding relationships are represented by
food chains and food webs.
• Oceans are being overfished.
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Primary Productivity
• Primary productivity is the rate at which
energy is stored in organic matter.
• Photosynthesis uses solar radiation.
• Chemosynthesis uses chemical reactions.
• 99.9% of the ocean’s biomass relies
directly or indirectly on photosynthesis
for food.
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Photosynthesis
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Photosynthesis and chemosynthesis are both processes by
which organisms produce food; photosynthesis is powered by
sunlight while chemosynthesis runs on chemical energy.
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Primary Production
• Ecosystems depend upon the ability of some
organisms to convert inorganic compounds into
food that other organisms can then exploit (or
eat!).
• In most cases, primary food production occurs in
a process called photosynthesis, which is
powered by sunlight.
• In a few environments, primary production
happens though a process called chemosynthesis,
which runs on chemical energy.
• Together, photosynthesis and chemosynthesis
fuel all life on Earth.
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Photosynthesis
• 1. The Sun gives off energy in the form of light.
• 2. Plants absorb sunlight. They take up nutrients
from their roots and release Carbon Dioxide
through the pores on their leaves.
• 3. Plants use solar energy to make organic
molecules, aka glucose (sugar).
• 4. The plants grow and reproduce.
• Example: Photosynthesis takes place on land
and in shallow water where sunlight can reach
seaweeds.
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Chemosynthesis
• 1. Hot water gushing from hydrothermal vents is
saturated with dissolved chemicals.
• 2. Bacteria absorb hydrogen sulfide and carbon
dioxide from vent water and oxygen from seawater.
• 3. The bacteria use energy released by oxidizing
sulfur to make organic molecules.
• 4. The bacteria grow and reproduce and are eaten
or hosted as internal symbionts by other animals.
• Chemosynthesis occurs around hydrothermal vents
and methane seeps in the deep sea where sunlight
is absent.
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In the diagram, mussels and tubeworms are using the hydrogen
sulfide released from a hydrothermal vent. The chemical
equation given here for chemosynthesis
is just one of a number
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of possibilities.
Instructions:
1.
2.
3.
•
Create a foldable of chemosynthesis vs. photosynthesis.
Construct a hydrothermal vent fauna food web.
Critical Thinking Question
Marine scientists were stunned to find complex
ecosystems based on chemosynthesis flourishing around
deep-sea hydrothermal vents. This discovery also caught
the attention of space scientists, giving them renewed
hope that they might find life elsewhere in the solar
system. Explain why chemosynthesis may be more likely
to support life on distant worlds than photosynthesis.
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Food Web
•
•
•
•
•
Top Order Carnivores:
First Order Carnivores:
Primary Consumers:
Primary Producers:
Simple Chemicals:
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Measurement of Primary Productivity
• Directly – capture
plankton in plankton
nets
• Measure radioactive
carbon in seawater
• Monitor ocean color
with satellites
– Green pigment
chlorophyll
– SeaWiFS
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Ocean Chlorophyll – SeaWiFS
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Factors Affecting Primary Productivity
• Nutrient availability
– Nitrate, phosphorous, iron, silica
– Most from river runoff
– Productivity high along continental margins
– Redfield ratio – C:N:P
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Factors Affecting Primary Productivity
• Solar radiation
– Uppermost surface seawater and shallow
seafloor
– Compensation depth – net photosynthesis
becomes zero
– Euphotic zone—from surface to about
100 meters (330 feet)
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Light Transmission in Ocean
Water
• Visible light of the electromagnetic
spectrum
• Blue wavelengths penetrate deepest
• Longer wavelengths (red, orange)
absorbed first
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Transmission of Light in
Seawater
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Color in the Ocean
• Color of ocean
ranges from deep
blue to yellow-green
• Factors
– Turbidity from runoff
– Photosynthetic
pigment (chlorophyll)
• Eutrophic
• Oligotrophic
• Secchi Disk – measures
water transparency
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Upwelling and Nutrient Supply
• Cooler, deeper seawater
is nutrient-rich.
• Areas of coastal upwelling
are sites of high
productivity.
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Upwelling and Nutrient Supply
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Types of Photosynthetic Marine
Organisms
• Anthophyta
–Seed-bearing plants
• Macroscopic (large) algae
• Microscopic (small) algae
• Photosynthetic bacteria
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Anthophyta
• Only in shallow
coastal waters
• Primarily grasses
and mangroves
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Macroscopic Algae
•
•
•
•
“Seaweeds”
Brown algae
Green algae
Red algae
– Most abundant and
most widespread
– Varied colors
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Microscopic Algae
• Produce food for 99% of marine animals
• Most planktonic
• Golden algae
– Diatoms – tests made of silica
– Coccolithophores – plates of calcium carbonate
• Dinoflagellates
– Red tide (harmful algal bloom)
– Toxins
– Fish kills
– Human illness
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Microscopic Algae
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Photosynthetic Bacteria
• Extremely small
• May be responsible
for half of total
photosynthetic
biomass in oceans
• Exert critical influence
on marine
ecosystems
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Regional Primary Productivity
Variations
• Values range from 1 gC/m2/year to
4000 gC/m2/year based on:
– Uneven distribution of nutrients
– Changes in availability of sunlight
• 90% of biomass from euphotic zone
decomposes before descending
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Regional Primary Productivity
Variations
• Only 1% of organic matter is not
decomposed in the deep ocean.
• Biological pump – moves material from
euphotic zone to sea floor
• Subtropical gyre thermoclines and
pycnoclines prevent the resupply of
nutrients to the surface.
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Polar Ocean Productivity
• Winter darkness
• Summer sunlight
• Phytoplankton
(diatoms) bloom
• Zooplankton (mainly
small crustaceans)
productivity follows
• Example: Arctic
Ocean’s Barents Sea
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Polar Ocean Productivity
• Antarctic productivity
slightly greater than
Arctic
• North Atlantic Deep
Water upwells near
Antarctica
• Productivity decrease
from UV radiation –
ozone hole
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Polar Ocean Productivity
• Isothermal waters –
little mixing
• Plankton remain at
surface
• Blue whales migrate
to feed on maximum
zooplankton
productivity.
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Productivity in Tropical Oceans
• Permanent
thermocline is barrier
to vertical mixing
• Low rate of primary
productivity – lack of
nutrients
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Productivity in Tropical Oceans
• High primary productivity in areas of
– Equatorial upwelling
– Coastal upwelling
– Coral reefs
• Symbiotic algae
• Recycle nutrients within the ecosystem
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Temperate Ocean Productivity
• Productivity limited by
– Available sunlight
– Available nutrients
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Temperate Ocean Productivity
• Highly seasonal pattern
• Winter low
– Many nutrients, little sunlight
• Spring high
– Spring bloom
• Summer low
– Few nutrients, abundant sunlight
• Fall high
– Fall bloom
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Temperate Ocean Seasonal
Cycle
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Comparison of Global Productivities
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• Upwelling is an oceanographic
phenomenon that involves wind-driven
motion of dense, cooler, and usually
nutrient-rich water towards the ocean
surface, replacing the warmer, usually
nutrient-depleted surface water.
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Learning Target
Write the questions:
1. Describe and analyze the limiting factors
that influence the primary productivity of the
oceans.
2. Antarctic productivity is slightly greater than
artic because of ____________.
3. What can an upwelling provide oceans?
4. Why is a spring bloom greater in productivity
than a fall bloom?
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Energy Flow in Marine Systems
• Biotic community – assemblage of
organisms in definable area
• Ecosystem – biotic community plus
environment
• Energy flow is unidirectional based on
solar energy input.
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Energy Flow in Marine Systems
• Three categories of organisms:
• Producers
– Nourish themselves with photosynthesis or
chemosynthesis
– Autotrophic
• Consumers
– Eat other organisms
– Heterotrophic
• Decomposers – break down dead
organisms or waste
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Energy Flow in Marine Systems
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Consumers in Marine
Ecosystems
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•
•
•
Herbivores – eat plants
Carnivores – eat other animals
Omnivores – eat plants and animals
Bacteriovores – eat bacteria
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Nutrient Flow in Marine Ecosystems
• Biogeochemical
cycling
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Feeding Strategies
• Suspension feeding or filter feeding
– Take in seawater and filter out usable
organic matter
• Deposit feeding
– Take in detritus and sediment and
extract usable organic matter
• Carnivorous feeding
– Capture and eat other animals
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Feeding Strategies
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Trophic Levels
• Feeding stage
• Chemical energy transferred from
producers to consumers
• About 10% of energy transferred to next
trophic level
• Gross ecological efficiency
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Trophic Levels
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Ecosystem Energy Flow and Efficiency
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Food Chains
• Primary producer
• Herbivore
• One or more
carnivores
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Food Webs


Branching network of
many consumers
Consumers more
likely to survive with
alternative food
sources
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Biomass Pyramid
• The number of
individuals and total
biomass decreases
at successive trophic
levels.
• Organisms increase
in size.
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Marine Fisheries
• Commercial fishing
• Most from continental
shelves
• Over 20% from areas
of upwelling that
make up 0.1% of
ocean surface area
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Overfishing
• Fish from standing stock – the mass
present in the ecosystem at any given time
• Overfishing – fish stock harvested too
rapidly, juveniles not sexually mature to
reproduce
• Reduction in Maximum Sustainable Yield
(MSY)
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Exploitation Status of Marine
Fish
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Overfishing
• 80% of available fish
stock fully exploited,
overexploited, or
depleted/recovering
• Large predatory fish
reduced
• Increased fish
production,
decreased stocks
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Incidental Catch or Bycatch
• Non-commercial species are taken
incidentally by commercial fishers.
• Bycatch may be up to 8 times more than
the intended catch.
– Birds, turtles, dolphins, sharks
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Tuna and Dolphins
• Tuna and dolphins
swim together
• Caught in purse
seine net
• Marine Mammals
Protection Act
addendum for
dolphins
• Driftnets or gill nets
banned in 1989
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Purse Seine Net
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Fisheries Management
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Regulate fishing
Conflicting interests
Human employment
Self-sustaining marine ecosystems
International waters
Enforcement difficult
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Fisheries Management
• Many large fishing
vessels
• Governments
subsidize fishing
• 1995—world fishing
fleet spent $124
billion to catch $70
billion worth of fish
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Fisheries Management
• Northwest Atlantic Fisheries such as
Grand Banks and Georges Bank
• Canada and United States restrict fishing
and enforce bans
• Some fish stocks in North Atlantic
rebounding
• Other fish stocks still in decline (e.g., cod)
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Fisheries Management Effectiveness
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Fisheries Management
• Consumer choices in seafood
• Consume and purchase seafood from
healthy, thriving fisheries
– Examples: farmed seafood, Alaska salmon
• Ecosystem-based fishery management
• Avoid overfished or depleted seafood
– Examples: tuna, shark, shrimp
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Seafood Choices
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End of CHAPTER 13
Biological Productivity
and Energy Transfer
© 2011 Pearson Education, Inc.