1. Ocean Primary Production and
Biogeochemical Controls
Oceanic ecosystem largely depends on
the biochemical process of phytoplankton
2. 1. Understand the trophic dynamics in the ocean
2. Know the marine productivity and its global
distribution
3. Biological productivity in the upwelling water
Learning Objectives
3. ENERGY
Autotrophs: organisms
capable of self-nourishment
by synthesizing food from
inorganic nutrients
heterotrophs: organisms not
belonging to autotrophs; all
animals are heterotrophs
c.f. Fig.10-1 in text
8. Trophic levels
and dynamics
Trophic dynamics: study the interrelationships among
organisms by means of the nutrition flow in the
ecosystem
The first trophic level is the autotroph, i.e. the plant
producer, providing the matter and energy to the
higher trophic levels, i.e. consumers
Although simple, it
reminds us that all of
the energy that a
species expends relies
on the photosynthesis
of plants
Simple food chain
9. Food Web: a network of interlaced and
interdependent food chains
Omnivore: both
plant and animal
eater
grazing food chain
phytoplankton → zooplankton → nekton
detritus food chain
detritus → deposit feeder → nekton
11. simple rule
Typically, a positive correlation
exists between body size of aqua
animals and their trophic level
Exceptions?
Energy transfer between trophic levels is not efficient
12. Five basic consuming types of aqua animals
(Fig.10-3 in text)
•Grazer − herbivores (e.g. sea urchin)
•Predator − carnivores (e.g. shark)
•Scavenger − benthic invertebrates (e.g. crab)
•Filter feeder − animals living in burrows
•Deposit feeder − animals living in sediments
Dynamical time
lag exists
between the food
abundance and
animal population
13. Trophic levels
and dynamics
Food Web
Energy
Sunlight and
nutrition supplies are
two principal factors
that limit the primary
production in the
ocean.
In addition to forming
carbohydrates (via
photosynthesis),
plants also
manufacture other
organic compounds,
including proteins,
lipids, and nucleic
acids such as DNA
and RNA.
14. Plankton blooms
Cell division causes
diatom populations to
increase dramatically
and rapidly (within
several days) under
preferable growth
conditions
Red tide
15. Plankton Blooms
Bands of the dionflagellate Lingulodinium polyedrum moving
onshore over the troughs of a series of internal waves
16. Nonlinear Internal Waves and Phytoplankton
Isopycnals
Have you
noted
how fast
the time
lapse is !
22. Why do we care about the Carbon Export
Production?
• The total amount of carbon in the ocean is about
50 times greater than the amount in the
atmosphere, and is exchanged with the
atmosphere on a time-scale of several hundred
years.
• At least 50% of the oxygen we breathe comes
from the photosynthesis of marine plants.
• Currently, 48% of the carbon emitted to the
atmosphere by fossil fuel burning is sequestered
into the ocean.
• But the future fate of this important carbon sink is
largely uncertain (therefore anxious) because of
potential climate change impacts on ocean
circulation, biogeochemical cycling, and
ecosystem dynamics
=> Definition of primary productivity in the ocean
23.
24. Roles of bacterial in the ecosystem
1.Bacterial decompose dead tissue and
release essential inorganic nutrients into
the water for recycling by plants.
*NH3 + 2O2 → H+ + NO3
- +H2O (aerobic
bacterial)
*SO4
2- → 2O2 + S2- (anaerobic bacterial)
2.Plays both the starting point (providing
nutrients for plant photosynthesis) and
the ending point (proceeding the decay of
organic matter) of the food cycle that
provides the linkage between nonliving
and living matter.
3.Also serve as food for some species of
zooplankton
26. Cyanobacteria (blue-green algae) are
predominantly photosynthetic prokaryotic
(初核質 ) organisms containing a blue
pigment in addition to chlorophyll. They
use sunlight directly to manufacture food
from dissolved nutrients.
27. Hydrothermal vents and Chemosynthetic bacteria
The base of vent community is
occupied by microbes rather
than by plants, because there is
no light in the deep sea.
Chemical energy released by the
oxidation of inorganic compounds is
used to produce food.
29. (1) Nutrient Sources for Primary Production
and (2) limitations of CO2 fluxes
The fluxed of organic carbon must be
sustained by an adequate flux of
macronutrients (P, N, Si)
If macronutrients are unavailable
then the CO2 flux is reduced!
What are the controllers on Export Production?
Macronutrients vs. micronutrients (p339 in text)
30. 1) Ocean nutrient inventory
2) Utilization of nutrients in HNLC condition
3) Change of Redfield Ratio (A. C. Redfield 1958;1963)
What are the controllers on Export Production?
31. Nitrogen appears to be the most
important controlling factor that limit the
primary productivity of ecosystems.
1) Ocean nutrient inventory
What are the controllers on Export Production?
Why ? (important; p339 in text)
• N is an essential nutrient for all living
organisms (nucleic acids and amino acids)
• N has many oxidation states, which makes
speciation and redox chemistry very
interesting
• NH4+ is the preferred N nutrient
32. NO3
Chlorophyll
Large
detritus
Organic matter
N2 NH4 NO3
Water column
Sediment
Phytoplankton
NH4
Mineralization
Uptake
Nitrification
Nitrification
Grazing
Mortality
Zooplankton
Susp.
particles
Aerobic mineralization
De-nitrification
N2
Fixation
Mix Layer
depth
De-nitrification − the removal of fixed N, mostly NO3-, resulting in
the formation of nonbiologically available N, primarily N2 gas
Continental
shelf
sediments are
responsible for
up to 67% of
marine N
denitrification
estimates
33. 2) Utilization of nutrients in HNLC
What are the controllers on Export Production?
34. HNLC − High-Nutrient, Low-Chlorophyll
It describe areas of the ocean where the
number of phytoplankton are low in spite of
high macronutrient concentrations (nitrate,
phosphate, silica acid).
HNLC is thought to be caused by the scarcity
of iron (a micronutrient which phytoplankton
require for photosynthesis) and high grazing
rates of micro-zooplankton that feed on the
phytoplankton.
The HNLC condition has been observed in the
equatorial and sub-arctic Pacific Ocean, the
Southern Ocean, and in strong upwelling
regimes, such as off central and northern
California and off Peru.
36. Southern Ocean HNLC • Nitrate and phosphate
concentrations are high
year round but standing
stocks of phytoplankton
are always low (0.2-0.4
µg/L; normal yield is 1 µg
/L)
• Iron concentrations in
these waters are sub-
nanomolar: the same as
those that are known to
limit growth of
phytoplankton,
particularly large species
such as diatoms.
• Addition of low levels of
Fe promotes growth of
large phytoplankton.
-bottle experiments
-in situ fertilization
experiments
37. One of the
possible solutions
to global warming
is to fertilize HNLC
ocean areas
lacking iron with
iron to increase
CO2 absorption
from
phytoplankton.
38. Redfield ratio (stoichiometry) − the molecular
ratio of carbon, nitrogen and phosphorus in
phytoplankton.
Redfield (1963) described the remarkable
congruence between the chemistry of the deep
ocean and the chemistry of living things in the
surface ocean (i.e. phytoplankton). Both have N:P
ratios of about 16.
When nutrients are not limiting, the molar
element ratio C:N:P in most phytoplankton is
116:16:1.
Redfield thought it wasn't purely coincidental that
the vast oceans would have a chemistry perfectly
suited to the requirements of living organisms.
He considered how the cycles of not just N and P
but also C and O could interact to result in this
match.
39. N* = N – 16 P
N = 25790
N2 fixation
De-nitrification
Modern Time
41. Regions with upwelling represent
the productivity
Equatorial
upwelling
Coastal
upwelling
Water
turbidity
42. ocean terrestrial area
Open ocean deserts
continental shelves forest; grassland
upwelling regions rain forests
shallow estuaries farmlands
43.
44. Both physical and biological processes in the ocean affect
the carbon cycle. In addition, physical processes
influence the net production of biological oceanography.
