…in the Ocean…
• Biological Productivity
• We know what the ocean zones are and who
lives there…but HOW do they live there
together?
• TROPHIC STRUCTURE:
– Flow of energy or matter through an ecosystem,
a “feeding” or trophic system
– Primary, Secondary etc. PRODUCERS AND
CONSUMERS
– Food web/chain/pyramid
Ecosystems
• An ecosystem is the totality of the
environment encompassing all parts:
–
–
–
–
Chemical
Physical
Geological
Biological
• Ecosystems function by the exchange of
matter and energy.
• Plants use chlorophyll in photosynthesis:
– to convert inorganic material into organic
compounds
– to store energy for growth and reproduction
• Plants are autotrophs and the primary
producers in most ecosystems.
• All other organisms are heterotrophs, the
consumers and decomposers in
ecosystems.
• Herbivores eat plants and carnivores eat
animals; omnivores eat both.
• Material is constantly recycled in the
ecosystem.
– Energy gradually dissipates as heat and is lost.
Ecosystem Model
The word “trophic” refers to nutrition
• Trophic dynamics is the study of the nutritional
interconnections among organisms within an
ecosystem.
• Trophic level is the position of an organism within
the trophic structure of an ecosystem.
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–
–
–
Autotrophs form the first trophic level.
Herbivores are the second trophic level.
Carnivores occupy the third and higher trophic levels.
Decomposers form the terminal level.
A food chain is the succession of organisms within
an ecosystem based upon trophic dynamics.
Who is eaten by whom.
Fnft: Simple Food Chain
A food web consists of interconnected and
interdependent food chains
Fnft: Food Web
• An energy pyramid represents a food chain in terms of the
energy contained at each trophic level.
• The size of each level in an energy pyramid is controlled by
the size of the level immediately below.
Fnft: Energy Pyramid
Food chains transfer energy from one trophic
level to another
• Biomass is the quantity of living matter per
unit area or per volume of water.
• With each higher trophic level:
–
–
–
–
the size of organisms generally increases
the reproductive rate decreases
The number of organisms decreases
the total biomass decreases
• The two major food chains in the ocean are:
– the grazing food chain
– the detritus food chain (non-living wastes form
the base of the food chain)
• Only about 10-20% of energy is transferred
between trophic levels.
• This produces a rapid decline in biomass at
each successive trophic level.
Energy Transfer Between Trophic Levels
Fnft: Energy Transfer Between Tropic Levels
• As the primary producers, plants require for
photosynthesis :
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–
–
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Sunlight
Nutrients
Water
Carbon dioxide
• The formula for photosynthesis is:
6CO2 + 6H2O + solar energy  C6H12O6 (sugar) + 6 O2
Sun
Producers
Photosynthesizers:
Green plants
and algae, and
specialized
bacteria
To space
Consumers
Respirers:
Animals and
decomposers and
plants at night
• Sunlight and nutrients are the limiting
factors in marine ecosystems.
• Phytoplankton blooms are the rapid
expansion of a phytoplankton population
because sunlight and nutrients are abundant.
• Factors that limit plant growth and reduce primary
production include:
– Major Factors:
• solar radiation
• nutrients
– Secondary Factors:
•
•
•
•
Upwelling
Turbulence
grazing intensity
turbidity
• Only 0.1 to 0.2% of solar radiation is used for
photosynthesis, and its energy stored in organic
compounds.
• Primary production is the total amount of
carbon (C) converted into organic material
per square meter of sea surface per year
(gC/m2/yr)
• Productivity varies greatly in different parts of the
ocean in response to the availability of nutrients
and sunlight.
• In the tropics and subtropics sunlight is abundant.
• This generates a strong thermocline that:
– restricts upwelling of nutrients
– results in lower productivity
• High productivity locally occurs in:
– areas of coastal upwelling
– tropical waters between the gyres
– coral reefs
• In temperate regions productivity is
distinctly seasonal.
• Polar waters are nutrient-rich all year.
• Productivity is only high in the summer
when light is abundant.
Variations in Primary Productivity
North Atlantic
Tropics
Spring Diatom Bloom in the North Atlantic
• Primary productivity varies from 25 to 1250
gC/m2/yr in the marine environment.
• It is highest in estuaries and lowest in the open
ocean.
• In the open ocean primary productivity
distribution resembles a “bull’s eye” pattern.
– The lowest productivity is in the center
– The highest is at the edge of the basin
• Water in the center of the ocean is a clear blue
because it is an area of downwelling, above a strong
thermocline.
– It is almost devoid of biological activity.
• Continental shelves display moderate productivity between
50 and 200 gC/m2/yr.
• This is because:
– nutrients wash in from the land
– tide- and wave-generated turbulence recycle nutrients
from the bottom water
• Polar areas have high productivity because there is no
pycnocline to inhibit mixing.
• Equatorial waters have high productivity because of
upwelling.
• Centers of circulation gyres, which occupy most of the
open ocean, are biological deserts.
Global Variations in Primary and Secondary
Production
Fnft: Primary Productivity
Upwelling in the South Pacific
Figure 10-14 Upwelling
Coastal Upwelling
…so that’s only 1 side of the equation…
What about the CONSUMERS?
Animals must consume pre-existing organic
material to survive
• Animals break down the organic compounds
into their inorganic components to obtain the
stored energy.
• The chemical formula for respiration is:
C6H12O6 (sugar) + 6O2  6CO2 + 6H2O + Energy
• The recovered energy is used for:
– Movement
– Reproduction
– Growth
• The food consumed by most organisms is
proportional to their body size (exceptions
occur).
– Smaller animals eat smaller food
– Larger animals eat larger food
• The basic feeding strategies of animals are:
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–
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Grazing
Predation
Scavenging
Filter feeding (suspension feeding)
Deposit feeding/Detritovores
• Population size is dependent upon food
supply and grazing pressure.
• Definitions:
– Grazing – scrap algae/food off of coral/rocks/hard surface. Ex.
parrotfish
– Predation – one animal (typically larger/stronger) “preying” on
another (typically weaker/smaller). Ex. Shark, barracuda
– Scavenging – feeding on other dead animals and other food
sources, not “picky.” Ex. Crab, lobster
– Filter feeding (suspension feeding) – creating a feeding “current,”
or to “filter” food particles out of the water column through
various methods. Ex. Whale shark, barnacle, shrimp
– Deposit feeding – eating organic matter from the bottom. These are
commonly “tube builders” or “burrowers.” Many eat detritus (nonliving & organic waste, e.g. DOM, fecal pellets, dead
animals/plants etc.) and are called Detritovores. Ex. Sea cucumber
Predator
Feeding Strategies
Filter Feeder – Feather Duster
Worm; Shrimp, (Ancient) Fish
Barracuda
Scavenger
Crab
Grazing
Feeding Strategies
Filter Feeder
Parrotfish (on coral)
Deposit Feeder
Sea Cucumber
Prey-Predator Relationships
Fnft: Prey-Predator Relationships
• And finally, the “other” consumer…
• Bacteria are
decomposers.
• They break down
organic material and
release nutrients for
recycling.
Fnft: Nutrient Cycling
Now let’s break it down…
• …the “basics”
• Food Webs and Trophic structures are
different in different parts of the world (i.e.
each HABITAT has its’ own unique
balanced feeding structure)
• Each section is a (larger) part of the whole
Fnft: Simplified paths of the flow of oxygen and carbon in an idealized
marine ecosystem
Fnft: Biogeochemical cycle of nitrogen or phosphorus
Fnft: Energy flow in a marine ecosystem
Fnft: Major biotic components of a marine ecosystem
Adapted from W. D. Russell-Hunter. Aquatic Productivity. Macmillan,
1970
Fnft: Food pyramid that leads to an adult herring
Herring during
different
stages of
development
(growth)
Figure 15.24
Figure 10.13
antarctic
food
chain
antarctic
food
web
Figure 10.14
Benthic food web
Epipelagic
Food
web
Figure 15.25
• Epipelagic food web
Remember
• EACH habitat will have its own food
web/trophic structure based on:
- location (and water chemistry)
- organismal make-up
- other abiotic “influences” (including
proximity to land/pollution sources)
WATCH FOR THESE AS WE STUDY
EACH HABITAT IN THE COURSE!