Lecture 15- Ocean Primary Production I Flashcards
why study primary production?
- Base of the food web
- Essential element of the global carbon cycle
- Represents half of the total global photosynthesis
why is the global carbon a big topic?
it is closely related to our global warming problem
photosyntheis
consumes carbon dioxide gas to form the particulate carbon of algae
respiration
by all organisms produces carbon dioxide gas
difference between photosynthesis and respiration by all of the organisms
is what sinks to the ocean floor
half of oxygen comes from
photosynthesis in the ocean
global carbon cycle- atmosphere
0.5%
global carbon cycle- respiration and decay
0.01%
global carbon cycle- lithosphere
99.5%
Plankton
small organisms that drift with the ocean currents
Phytoplankton
small cells (often single cells but sometimes chains or colonies of many cells) that contain chlorophyll and drift with ocean currents
glucose from photosynthesis
serves as the energy source for all subsequent biochemical reactions
Photosynthesis only depends on
the availability of water, carbon dioxide, and sunlight
Primary production of photosynthesis requires
the uptake of plant nutrients for the construction of complex molecules that are needed to form new cellular components
magnitude of the primary production
depends on the availability of essential plant nutrients as well as sunlight
Net Primary Production (NPP)
- difference between the amount of CO2 consumed by photosynthesis and the amount of CO2 produced by respiration
- also known as the net gain or net loss of carbon within the cell
primary production effectively consumes carbon dioxide and forms
particulate organic carbon that can sink into the deep ocean
primary production
- makes oxygen
- requires light AND essential plant nutrients such as nitrogen, phosphorous, Si, and Fe
phytoplankton
single celled organisms that carry out the vast majority of primary production in the ocean via chlorophyll
diatoms
require silica
Flagellates
mobile so they are able to avoid sinking in calm waters
photosynthetic bacteria
- able to grow at very low nutrient concentrations
- main photosynthesizers
At compensation light level
photosynthesis is on the speed of respiration
photosynthesis increases with
intensity of light but respiration is constant
At light levels below the compensation light level
- phytoplankton cells do not have sufficient light to photosynthesize fast enough to meet their basal metabolic needs
- respiration exceeds photosynthesis
below compensation light level
Negative values of net primary production
At low light level
phytoplankton are light limited
At optimal light levels
phytoplankton are light saturated
At very high light levels
phytoplankton are photoinhibited
compensation depth
depth at which the ambient light intensity is equal to the compensation light intensity
The amount of nutrient needed for growth by an individual phytoplankton cell is proportional to
the cell’s mass or equivalently to the cell’s volume
amount of nutrient that can be transported into a cell is proportional to
the cell’s surface area
smaller cells
can grow better at lower nutrient concentrations
4 Phytoplankton Nutrients of Interest
- Nitrogen
- Phosphorous
- Silica (for diatoms)
- Iron
main source of nitrogen, phosphorous and silica
vertically mixing or upwelling of nutrient rich deep water to the surface
What do you expect to happen to ocean primary production under a global warming scenrtio that enhances only temperatures of the surface layer of the ocean and leaves the deep layer cold (strengthens the thermocline/pcynocline)?
decrease
thermocline
- hold phytoplankton near the sunlit surface ocean
- significant barrier to upward mixing of nutrient rich deep water
- stronger the thermal stratification, the stronger the inhibition of nutrient mixing
Source of Iron
- Main source of iron input to the surface ocean is from dust blowing off of continents
- Not abundant in the deep ocean
Iron Limited Regions
Southern Ocean
Primary production is enhanced
- high light
- high nutrients
