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Chapter 13
Biological Productivity and
Energy Transfer
Essentials of Oceanography
7th Edition
Primary productivity
Primary productivity is the amount of
carbon (organic matter) produced by
organisms
Mostly through photosynthesis
Energy source = solar radiation
Also includes chemosynthesis
Energy source = chemical reactions
Photosynthetic productivity
Figure 13-1
Oceanic photosynthetic
productivity
Controlling factors affecting photosynthetic
productivity:
Availability of nutrients
Nitrates
Phosphates
Iron
Amount of sunlight
Varies daily and seasonally
Sunlight strong enough to support photosynthesis
occurs only to a depth of 100 meters (euphotic zone)
Locations of maximum
photosynthetic productivity
Margins of the oceans
Abundant supply of nutrients from land
Water shallow enough for light to penetrate all
the way to the sea floor
Upwelling areas
Currents hoist cool, nutrient-rich deep water to
the sunlit surface
Coastal upwelling
Figure 13-3
The electromagnetic spectrum
and light penetration in seawater
Figure 13-4
Water color and life in the ocean
Ocean color is influenced by:
The amount of turbidity from runoff
The amount of photosynthetic pigment, which
corresponds to the amount of productivity
Yellow-green = highly productive water
Found in coastal and upwelling areas (eutrophic)
Clear indigo blue = low productivity water
Found in the tropics and open ocean (oligotrophic)
Satellite view of world productivity
Figure 13-6
Photosynthetic marine
organisms: Plants
Seed-bearing
plants
Eelgrass
(Zostera)
Surf grass
(Phyllospadix)
Surf grass
Figure 13-7
Photosynthetic marine
organisms: Macroscopic algae
Brown algae
Sargassum (top left)
Macrocystis (top right)
Green algae
Codium (bottom left)
Red algae
Lithothamnion (bottom
right)
Figure 13-8
Photosynthetic marine
organisms: Microscopic algae
Microscopic algae include:
Golden algae
Diatoms (silica test resembles a pillbox)
Coccolithophores (calcite plates form a spherical test)
Dinoflagellates
Produce a test made of keratin
Posses a whip-like flagella
Bioluminescence
Exist in great abundance, creating red tides (harmful
algae blooms)
Dinoflagellates and red tides
Figure 13C
Regional productivity
Photosynthetic productivity varies due to:
Amount of sunlight
Availability of nutrients
Thermocline (a layer of rapidly changing
temperature) limits nutrient supply
Examine three open ocean regions:
Polar oceans (>60° latitude)
2. Tropical oceans (<30° latitude)
3. Temperate oceans (30-60° latitude)
1.
Productivity in polar oceans
Sunlight peaks in
summer
Nutrients available
nearly year-round
(only weak seasonal
thermocline develops)
Productivity:
Peaks in spring
Limited by sunlight
Figure 13-10a
Productivity in tropical oceans
Sunlight strong
year-round
Nutrients limited by
strong, permanent
thermocline
Productivity:
Steady, low rate
Limited by nutrients
Exceptions:
Upwelling areas
Coral reefs
Figure 13-11
Productivity in temperate oceans
Sunlight varies
seasonally
Nutrients limited
by thermocline
Productivity:
Spring bloom
limited by
nutrients
Fall bloom
limited by
sunlight
Figure 13-12
Productivity in tropical,
temperate, and polar oceans
Figure 13-13
Energy flow in marine
ecosystems
Categories of
organisms:
Producers
Consumers
Decomposers
Figure 13-14
Biogeochemical cycling of matter
Figure 13-16
Ecosystem energy flow and
efficiency
Energy is
passed between
trophic
(feeding) levels
Transfer
efficiencies:
Algae = 2%
Other levels =
10%
Figure 13-18
Comparison between a food
chain and a food web
Figure 13-19
Biomass pyramid
At each step up
the pyramid,
there is/are:
Larger
organisms
Fewer
individuals
A smaller total
biomass
Figure 13-20
Ecosystems and fisheries
Fishery = fish
caught from the
ocean by
commercial fishers
Largest proportion
of marine fish are
taken from shallow
shelf and coastal
waters
Figure 13-21
Fisheries and overfishing
World total marine
fish production has
increased
dramatically
Overfishing occurs
when adult fish are
harvested faster
than their natural
rate of reproduction
Figure 13-22
Fisheries and bycatch
Some fishing
practices produce
large amounts of
incidental catch
(bycatch):
Purse seine nets set for
tuna can trap dolphins
Driftnets (gill nets)
take many unwanted
species
Spotted dolphin
Figure 13-23
Fisheries management
Fisheries management
seeks to maintain a longterm fishery by:
Assessing ecosystem health
Determining fish stocks
Analyzing fishing practices
Enforcing catch limits
Fisheries management does
not regulate the number of
fishing vessels
Figure 13-25
End of Chapter 13
Essentials of Oceanography
7th Edition