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55 terms

Primary Productivity

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What is the significance of ocean stratification in relation to primary production?
Strong stratification creates a strong thermocline, which disables nutrients that have sunk to the bottom to come back.
-Also, there is plenty of light for photosynthesis, but phytoplankton cannot migrate up for light and down for nutrients.
When is a thermocline strongest?
In warm weather (like the tropics year round, or the summer at temperate seas).
Why is the thermocline strongest in warm weather?
The cold water at the bottom remains unaffected by heat, while the surface is heated, creating a great difference in density, leading to stratification.
When is there a great phytoplankton bloom (in temperate seas)?
Autumn and spring, when the thermocline decays and there is a great nutrient input, and still light.
Where is there the greatest phytoplankton bloom?
The poles (in the summer), since there is very cold water, so no thermocline, and light.
Describe primary productivity in the Tropical Seas
-nutrients are limited due to stratification
-very little seasonal fluctuations
-reef areas (2% of tropical seas) are exceptions
Describe primary productivity in the Temperate Seas
-seasonal variation
--light limited in winter
--nutrient limited in summer (strong thermocline)
--autumn and spring blooms
Describe primary productivity in the Polar Seas
-light limited in winter
-strong, short summer bloom
Primary Productivity
the production of sugars from CO2
How is primary productivity usually done?
Through photosynthesis (sometimes chemosynthesis)
Chemosynthesis
production of sugars using energy from chemicals (released in deep sea vents)
Why is primary productivity important?
Because all life on Earth is directly or indirectly reliant on it.
Photosynthesis equation:
6CO2 + 6H20 --> C6H12O6 + 6O2

*sun powers reaction
What are limiting factors in the ocean?
Sunlight and nutrients (mainly nitrogen and phosphorous)
What are non-limiting factors in the ocean?
silica (makes many animals' shells), CO2 & H2O
What is the etymology of phytoplankton?
Phyto=photosynthesizing
Plankton= drifter (not good swimmers)
What are phytoplankton?
Microscopic plants that are the dominant primary producers in the ocean (do 90-96% of primary production)
What are the most common phytoplankton?
dinoflagellates & diatoms
Where is primary productivity highest?
coastal regions, because there is so much fertilizer with nitrogen and phosphorous
Biological Pump
phytoplankton remove CO2 from the surface waters and store it in the deep ocean (they consume a lot of CO2 and bring it to the bottom with their bodies when they die)
How might ocean fertilization help remove CO2 from our atmosphere? Will this removal be permanent?
Iron, released through fertilization, increases photosynthesis in phytoplankton, which bury CO2 via the biological pump process.
What are some problems with ocean fertilization when considering it as a means to mitigate global warming?
-hard to control
-needs constant upkeep
-possible damage=irreversible
-disruptions to food "web"
-severe oxygen depletion
-slows bio pump (phytos working harder)
Eutrophication (often algal bloom)
excess nutrients causing a bloom that uses up oxygen and creates a dead zone
*phytoplankton blooms take so much energy & cut off light (become a mass near water's surface), their decay also consumes a ton of oxygen, fishies die
Microbe
a microorganism, especially bacteria, that causes fermentation/ disease
Holoplankton
always suspended in water column
Meroplankton
only spend part of their lives suspended in water column
-eventually gain control of their movement
Benthic
lives on land
Zooplankton
animal plankton, heterotrophic, eat phytoplankton.
*important food source for fish, sharks, baleen whales
Hypoxic
water with low concentration of dissolved oxygen
Heterotrophic
cannot create its own food—must hunt it
Diurnal Vertical Migration
How zooplankton stay below photic zone during the day, migrate up at night
Matter____and Energy ____
Matter CYCLES and Energy FLOWS
The Carbon Cycle
-CO2 becomes sugar through photosynthesis/ chemosynthesis
-phytoplankton are consumed by animals which are consumed by bigger animals which are consumed by us
-phytoplankton die, sink, become rock/ FOSSIL FUEL
*also occurs on land
Photic Zone
the upper most region of the water column where there is enough light for photosynthesis to occur
What is the depth of the photic zone determined by?
-angle of the sun
-suspended particles
Aphotic Zone
zone where light does not penetrate (about 90% of the ocean)
Why do primary producers need nutrients?
to create DNA, RNA, proteins—to keep themselves together
Inorganic (nutrients)
not biologically "useful" by all organisms
Organic (nutrients)
in a form that all organisms can use to make biomolecules and/ or power cells
The Phosphorous Cycle
-there is no atmospheric phosphorous
-phosphate goes from soil to sea (mainly via fertilizer)
-consumed by plants, then plants consumed by animals
-phosphorous is excreted and decayed
*humans have a great affect on this cycle
The Nitrogen Cycle
-most complicated cycle
-inorganic Nitrogen gas is super abundant, but needs to be converted
-converted by nitrogen fixers
-becomes tissue
-becomes detritus
-decomposed
-nitrifying bacteria bring it back to organic form
-denitrifying bacteria re-inorganic it
Nitrogen Fixers
special organisms (mostly bacteria) that convert inorganic nitrogen to organic nitrogen
Why are nutrients limited at the surface?
Because they are used immediately and usually sink when in a dead organism or as waste
*this is all because the ocean is stratified by density
-nutrients rich at depth (because sunk)
-nutrients low at surface (because used up)
How do phytoplankton prevent sinking?
-oil floats (oil is less dense than water)
-they form colonies to increase surface area
-cilia and flagella
-appendages (increasing surface area)
Why is it beneficial for benthic invertebrates to have a planktonic larval stage?
-genetic diversity
-spreads offspring from parents/ each other = NO INBREADING
-colonizing new territory= taking oer the world
Fog
a cloud (condensed water) that touches the ground
How does fog form?
When warm, moisture-laden air cools—>gas condenses into small liquid droplets
Upwelling
when deep, cold (usually nutrient-rich) water is pulled to the surface
-usually wind-driven
Continental Margins
separates ocean from land
-active margin=subduction, deep ocean offshore
-passive margin=spreading, gradual
How does upwelling happen in California?
-wind blows out of the North
-pushes surface water away from coast (Ekhman)
-deep, cold water is pulled to surface
Ekhman Transport
-the net flow of a current is 90 degrees to the right of the path of the wind that drives it (Northern Hemisphere)
-Water at increasing depth will drift in directions increasingly to the right of the wind, until it is moving in a direction opposite to that of the wind.
*Pretty much Coriolis
Explain the weather in the Central Valley
-hot and humid air comes in from the Pacific
-cold, upwelled water condenses water in air and makes fog
-hot air rises into land
Compensation Depth
just above bottom of photic zone—light is at approx 1% of surface's intensity
Nutrient Regeneration
organisms decompose organic matter and return phosphates and nitrates
What factors limit primary productivity?
-sun light
-nutrients
-herbivores that eat primary producers