5/19/17
PLANKTON, PRIMARY PRODUCTIVITY,
AND BIOGEOCHEMISTRY
EPSS 15 Srping 2017 LAB #7
•  The base of the food
chain (phytoplankton)
depends upon
sunlight
•  Pelagic zone = area of
water that is not near
the bottom, or shore,
of a body of water
Green – 550 nm
Blue– 490 nm
Red – 720 nm
0
Yellow – 590 nm
•  Sunlight is critical to
the distribution of
oceanic life
Ultraviolet – 380 nm
SUNLIGHT & OCEAN ZONATION
Light
Euphotic Zone
100
200
Twilight
Dysphotic Zone
300
400
•  Benthic zone = area
associated directly
with the seafloor
Dark
Aphotic Zone
500
600
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Photic Zone – depth is
variable.
Green – 550 nm
Blue– 490 nm
Red – 720 nm
0
Yellow – 590 nm
•  Sunlight is critical to the
distribution of oceanic
life
Ultraviolet – 380 nm
SUNLIGHT & OCEAN ZONATION
Light
Euphotic Zone
100
Euphotic – region from
surface to critical layer
where photosynthesis
dominates
200
Twilight
Dysphotic Zone
300
Dysphotic – photosynthesis
no longer dominant
400
Dark
Aphotic Zone
500
600
THREE TROPHIC GROUPS
( trophic describes how an organism obtains energy)
1. 
Producers
–  Autotrophs: make complex organic
Diatoms - Producer
compounds from simple inorganic molecules,
commonly by photosynthesis (i.e. CO2, or
sulfide, methane etc.)
–  Ex: phytoplankton, bacteria, tube worms
2.  Consumers
–  Heterotrophs: feed on autotrophs or other
heterotrophic organisms for energy and
Copepod - Consumer
carbon compounds
–  Ex: copepods, mammals, zooplankton
3.  Decomposers
–  Saprotrophs: consume wastes or dead
organisms, return nutrients to the ocean
ecosystem
–  Ex: bacteria, worms, bacterioplankton
Bacterioplankton- Decomposer
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PLANKTON
•  Plankton means drifter, these
plants and animals are the base of
the ocean food chain
•  These are organisms that cannot
swim against currents. They
depend on ocean circulation to
move
•  Two types: phytoplankton and
zooplankton
•  Smallest are cyanobacteria at less
than 1µm,
•  Largest are macroplankton like
jellies and snails.
PHYTOPLANKTON
Exercise 1
Tiny Plants
–  Coccoid cyanobacteria:
0.2-2µm, half of the
photosynthetic biomass in the
ocean
–  Diatoms: 20-200µm, SiO2,
45% of ocean s primary
production, can be toxic to sea
birds in high levels
–  Dinoflagellates: 0.1-2mm,
protozoa, half phytoplankton,
half zooplankton, 2 flagella for
motion, red chlorophyll, red
tide algal blooms
–  Coccolithophores: 2-20µm,
covered in 30+ CaCO3 plates
called coccoliths
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ZOOPLANKTON
Exercise 1
Tiny Animals
–  Copepods: 1-2mm, small
crustaceans, transparent,
often feed during the night
–  Krill: 1-15cm, shrimp-like
crustaceans, move in swarms
–  Radiolarians: 0.1-0.2mm
SiO2 amoeboid protozoans,
spherical and conic
skeletons and often spines
–  Foraminiferans: 0.1-1.5mm
CaCO3 amoeboid
protozoans with chambered
shells
PRIMARY PRODUCTIVITY
•  Photosynthesis is the process by which organisms use chlorophyll to
absorb energy from sunlight and convert CO2 and H2O into glucose.
•  Primary productivity = amount of photosynthetic production
–  Units of primary production: gcarbon/year
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PRIMARY PRODUCTIVITY
•  Photosynthesis is the process by which organisms use chlorophyll to
absorb energy from sunlight and convert CO2 and H2O into glucose.
•  Primary productivity = amount of photosynthetic production
–  Units of primary production: gcarbon/year
Phytoplankton growth limited by availability of sunlight and
nutrients
Photosynthesis:
6 H2O + 6 CO2 + sunlight
C6H12O6 + 6 O2
Nutrients are needed for the reaction to be processed
C6H12O6 + 6 O2
Respiration:
6 H2O + 6 CO2 + energy
Nutrients are needed for the reaction to be processed
PRIMARY PRODUCTIVITY
•  Photosynthesis is the process by which organisms use chlorophyll to
absorb energy from sunlight and convert CO2 and H2O into glucose.
•  Primary productivity = amount of photosynthetic production
–  Units of primary production: gcarbon/year
Phytoplankton growth limited by availability of sunlight and
nutrients
Photosynthesis:
6 H2O + 6 CO2 + sunlight
C6H12O6 + 6 O2
The total amount of photosynthetic production is the Gross Primary
Product (GPP). From surface to depth where GPP=0 is the photic zone
C6H12O6 + 6 O2
Respiration (R):
6 H2O + 6 CO2 + energy
The net primary production (NPP) is the difference between the GPP
and R. The region from the surface to the critical layer (NPP=0) is the
euphotic zone.
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NUTRIENTS
•  Some nutrients required by marine organisms are limited in
supply
–  Readily available: Na+, K+, Mg2+, Ca2+, H2O, CO2
–  Limiting nutrients:
•  Nitrogen: nitrates --> NO3•  Phosphorus: phosphate --> PO43•  Silica: SiO32- or H4SiO4(aq)
•  Redfield ratio: 106 C to 16 N to 1 P
–  Average molar ratio of three
major elements taken up by
marine plankton
•  Micronutrients: only small
amounts needed for life
–  iron (Fe2+), copper (Cu2+),
selenium (Se2+)
BIOLOGICAL PUMP
•  The biological pump exports products from photosynthesis (organic
carbon) to the deep ocean
–  Zooplankton feed on phytoplankton, nutrients transferred through fecal pellets in a
process called egestion
Some materials are oxidized
or decomposed when they sink
The process of respiration
consumes oxygen to convert
organic carbon to CO2
Respiration:
C6H12O6 + 6 O2
6 H2O + 6 CO2 +
energy
Regulation of CO2 content of
atmosphere and O2 + nutrient
content of deep sea
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OCEAN CIRCULATION
•  Wind-driven and
density-driven
circulation transport
nutrients
–  O2 depleted with age of
deep water, nutrients
accumulate
•  Upwelling currents
replenish nutrients in
surface waters
–  e.g. California current,
Humboldt current
•  Interiors of Subtropical
Gyres are the least
productive regions of the
oceans because of
thermohaline
stratification
AGING DEEP WATER
•  How do we know deep water ages?
–  Radiocarbon measurements of Δ14C‰: younger waters have a
higher fraction of radioactive carbon than older waters.
As water ages, 14C decays, and CO2 accumulates
–  North Atlantic and Southern Ocean bottom waters are
younger than Pacific bottom waters
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End
THIS IS EXACTLY WHAT IT
LOOKS LIKE…
Susumu Honjo, Woods Hole Oceanographic Institution, 1997
Size of a
comma
(,)
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