Ocean Ecosystem
Goal:
To understand the factors (both biotic and abiotic) that control
the distribution and abundance of life in the oceans
Ecosystem Review
Ecosystem:
“Any area of nature that includes living
organisms and non-living substances that
interact to produce and exchange of materials
between living and non-living parts is an
ecological system or ecosystem.” (E.P.Odum)
Ecosystems consist of 4 components: abiotic,
producers, consumers, and decomposers;
• Ecology is the study of the interrelationships between the
physical and biological aspects of
the environment.
-It is the study of how organisms
adapt to their environment and in
turn alter it.
Ecosystem Review
Biotic Components of the Ecosystem
•
•
•
plants
animals
bacteria
Abiotic Components of the Ecosystem
•
•
•
geological

basin shape, size, & topography
physical

temperature, currents, pressure, light
chemical

carbon, nitrogen, phosphorus, oxygen, salinity, trace
metals, vitamins
The Environment
•
The ocean water column can be separated into 2 distinct
zones: the surface zone and the deep zone
1.
Surface zone
•
extends down to about 100- 300 meters
•
well mixed
•
known as the “mixed layer”
•
includes the photic zone
2.
Deep zone
•
the rest of the water column
•
dark and cold with much less productivity
•
includes the aphotic zone

the pycnocline forms a physical barrier between the surface and deep
zones
Biozones
Shelf Versus Basin
Trophic Interactions
•
To understand ocean ecology we need to know how the
autotrophic and heterotropic components are related
to each other (i.e. energy transfer and exchange)

we examine trophic level dynamics
–
trophic levels describe who eats whom
From Plankton to Top
Predator:
Building Marine Food
Webs
From Energy
Conversions
to Food Webs
(Almost) all life is based
on the sun’s energy.
- Sunlight enters
atmosphere.
- Plants turn sunlight into
organic matter.
- This is called primary
production.
- Energy flows in and out
of the earth, but organic
matter is recycled.
Production
•
There are two types of organisms in any given ecosystem:
autotrophs and heterotrophs

autotrophs make their own food (organic matter) from inorganic
nutrients (C, N, P, S, trace metals and vitamins) and either light
or chemical energy, they ‘fix’ CO2
–
they ‘fix’ CO2 via photosynthesis (light E) or chemosynthesis (chemical E,
i.e. H2S)
6 CO2 + 12 H20
C6H12O6 + 6 H2O + 6 O2
light OR
chemical E
–
–
–
autotrophs form the base of the food web (i.e. primary producers) and are
ultimately responsible for all life in the world’s oceans
marine examples include phytoplankton, cyanobacteria, and sulfide
oxidizing bacteria (i.e. at hydrothermal vents)
phytoplankton are the most abundant primary producers in the oceans
Production (cont’d)
•
autotrophs vs heterotrophs (cont’d)
–
heterotrophs consume food (organic matter) that has
already been produced

they derive energy (ATP) from the breakdown of organic
compounds via respiration
C6H12O6 + 6 O2


6 CO2 + 6 H2O + ATP
when there is no light (i.e. at night or in deeper waters)
phytoplankton and cyanobacteria respire the organic
compounds that they produced during photosynthesis
examples of marine heterotrophs include all marine animals
and most marine bacteria
Primary Production
= energy packaged
into life
Plankton = Drifting, tiny
life in the ocean
Phytoplankton = Plantlike Plankton
Primary Production =
Biomass built from
sunlight
Production (cont’d)
•
Productivity is high in the surface waters (i.e. photic zone), due
to ample sunlight for photosynthesis, and then decreases with
depth (i.e. aphotic zone)
Production (cont’d)
•
The critical depth is where total production (PT) equals
total respiration (RT): PT = RT
–
occurs at the 1% light level
Production (cont’d)
•
Productivity is highest in coastal waters and upwelling zones
due to higher nutrient concentrations
Average Global Primary Production (Chl a) March 6-13 2001
Terra MODIS NASA/GES/DISC/DAAC
Biological Productivity in the Ocean
Normal conditions
El Nino conditions
http://www.forces.si.edu/