Module 4 Flashcards
The process of photosynthesis is the corner stone of all life.
The bulk of the Earth’s living mantle is green plants (99.9% by weight); only
a small fraction of life consists of animals (Whittaker 1975)
Primary production
The energy fixed via photosynthesis per unit time
GPP (gross primary production)
The energy fixed in photosynthesis – energy lost via respiration
Net primary productivity
▪ Photosynthesis and respiration are both affected by
temperature and light intensity
At metabolic equilibrium
(photosynthesis =
respiration). This is called
Compensation point
Factors that affect conversion of solar
energy to primary production in plants includes:
Latitude
Cloudiness
Dust in atmosphere
Water in atmosphere
Leaf arrangemen
primary production
Leaf area. > Efficiency of gross
CO2 concentration
Factors that Limit
Aquatic Primary
Productivity includes:
Light penetration
Only about half of solar radiation is absorbed in the first meter of water.
Even in “clear” water, only _% of light may reach the depth of 20 m.
5-10
Nutrients limit primary production through their effects on the biomass of
chlorophyll in the phytoplankton.
Nutrients such as _ often limit primary production in the oceans.
Nitrogen and phosphorus
_ is the major nutrient limiting
oceanic primary production
Nitrogen
_ is an essential component of the photosynthetic machinery of the
cyanobacteria that fix nitrogen in the oceans.
Iron
_ may limit diatom production when diatoms are a dominant component of the
phytoplankton
Silica
Areas of upwelling in the ocean are exceptions to
the general rule of nutrient limitation.
Cooler, deeper seawater is nutrient-rich.
Areas of coastal upwelling are sites of high productivity.
–organic carbon produced within an ecosystem
Photosynthesis from aquatic plants
Attached algae
Phytoplankton in open water
Autochthonous
–organic inputs from outside the ecosystem
Dead organic matter from adjacent terrestrial ecosystems
as either dissolved organic matter (DOM) and particulate
organic matter (POM)
Allochthonous
_ is the main limiting factor on a day-to-day basis in lakes.
also limit freshwater lakes.
Solar radiation
is the major limiting nutrient for
primary productivity in lakes
Phosphorus
Chlorophyll concentrations and photosynthetic rates increase with
Phosphorus concentration
Better at fixing atmospheric nitrogen than green algae
Blue-green algae are “nuisance algae”
➢Form floating scums
➢Not preferred by fish or
zooplankton
➢Filamentous
➢Some produce toxins
Eutrophication
Blue green algae (BGA) are photosynthetic nitrogen fixers while green algae are
not.
BGA can fix atmospheric nitrogen using specialized cells called
heterocyst
▪ First to pointed out that nutrient supplies often limit plant growth
“If one of the essential
plant nutrients is deficient, plant growth will be poor
even when all other
essential nutrients are
abundant.”
Liebig’s Law of the Minimum
Methods of measuring
primary productivity
Oxygen Production Method (Light and Dark Bottle)
Harvest Method (Biomass)
Chlorophyll Method (Phytoplankton)
Satellite Method
Carbon Assimilation Method (14C)
Nitrogen
Sodium
Calcium
Magnesium
Phosphorus
Iro
n
Boron
Potassium
Manganese
Vanadium
Sulfur
Zinc
Copper
Molybdenum
Cobalt
Iodine
Chlorine
Plants require these nutrients to grow
–influences of physical and chemical factors on ecosystems
(e.g. temperature and nutrients)
Bottom up control
