The Primary Producers
y The primary food producers or autotrophs are
the organisms that synthesize their own food,
i.e., they synthesize carbohydrates from
inorganic matter.
y Both the primary food production activities ―
y
y
y
Photosynthesis and chemosynthesis ― occur
in the oceans.
A primary food production activity like
Photosynthesis
H2O
+
CO2
CH2O
z
+
Nutrients
O2↑
O2
+
4H2S
Example of
Bacterial
Chemosynthesis
Plant Photosynthesis
— requires sunlight, nutrients, water and
P h y to p la n k to n s
carbon dioxide (CO2) and
S u n lig h t
— is measured in gC/m2/yr.
Planktons carry most of the oceanic biological
N u tr ie n ts
activity. Of them, phytoplanktons are microZ o o p la n k to n s
scopic to submicroscopic primary food
producers in the oceans. These marine
autotrophs account for 90-98%, marine plants
for 2-10%, and chemosynthesis perhaps <1%,
of ocean’s primary food production activity.
Not surprisingly, therefore, phytoplanktonic as
well as zooplanktonic activities in the temperate
W in te r S p r in g
Sum m er
A u tu m n W in te r
waters follow the seasonality of the thermocline.
Indeed, a similar dependence on thermocline is y Marine biological productivity and
also what produces the daily vertical migration
production are generally limited to where
of microorganisms that was first observed
nutrients are available in the photic waters,
during World War II: it was named “deep
i.e., the coastal regions and upwellings
scattering layer” because it disrupted sub(equatorial and circum-Antarctic).
marine communications by scattering
sonar signals.
Total primary
Primary production Ocean area
rate (gC/m2/yr)
Open ocean 50
Coastal Sea 100
Upwelling
300
(million km2)
325
36
0.36
90%
10%
0.1%
Land plants
Marine Autotrophs:
y Plant evolution occurred in four stages: from
y
y
y
y
y
z
CO2
CH2O
+
4S
+
3H2O
production
(tons C/yr)
16 billion 82%
4 billion 18%
0.1 billion 0.5%
Marine plants
Spermatophytae
Spermatophytae
(seed bearing plants)
(seed bearing plants)
Pteridophytae
(ferns)
thallophytae (algae and fungi) Æ bryophytae (mosses)
Æ pteridophytae (ferns) Æ spermatophytae (seed
Bryophytae
bearing plants). These are therefore the four
(moss)
subkingdoms of the plant kingdom. Only the first and the
last of these are found in the oceans, however.
Thallophytae
Thallophytae
Clearly, the evolution of marine spermatophytae could
(algae and fungii)
(algae and fungii)
not have been intrinsic to the marine environment.
Thallophytae like algae and fungi are the phytoplanktons that dominate marine life. These include
blue-green, brown and red algae, diatoms and dinofllagelates. Seaweed is a large marine
multicellular algae.
Carbon compensation depth defines the depth extent for phytoplanktonic life.
Marine vascular plants include sea grass and mangroves.
There is increasing evidence of chemisynthesis in the oceanic environment (e.g., visit the URL:
http://www.ocean.udel.edu/deepsea/level-2/chemistry/chemo.html).