ocean primary production Flashcards
(32 cards)
The creation of organic compounds by phytoplankton using light (photosynthesis) and nutrients in the ocean.
ocean primary production
A process that transports carbon from the surface ocean to the deep ocean via sinking organic matter like phytoplankton and fecal pellets.
biological pump
The process by which CO₂ is dissolved in cold surface waters and transported to depth when the water sinks.
solubility pump
What role do aggregates and ballast play in carbon cycling?
Aggregates increase the sinking speed of organic material, enhancing carbon export to the deep ocean.
main controls on ocean primary production
Light, nutrients, seasonality, temperature, and physical ocean structure.
limits production in different seasons: winter
Light limitation
limits production in different seasons: Spring
Light and nutrient availability increase (bloom)
limits production in different seasons: Summer
Nutrient limitation due to stratification
limits production in different seasons: Fall
Mixing reintroduces nutrients
A condition where insufficient light restricts phytoplankton photosynthesis, common in winter or at depth.
light limitation
Which nutrients are important for primary production?
Nitrogen (N), Phosphorus (P), Iron (Fe), and Silicon (Si)
Why is nitrogen often the limiting nutrient?
Because of denitrification in coastal and oceanic environments and low rates of nitrogen fixation.
A microbial process that converts nitrate (NO₃⁻) to nitrogen gas (N₂), removing usable nitrogen from the system.
denitrification
The conversion of N₂ gas into bioavailable ammonia by specialized organisms, often limited by low Fe availability.
nitrogen fixation
High-Nutrient, Low-Chlorophyll areas where Fe limitation prevents full use of available nitrogen and phosphorus.
HNLC regions
The process where deep, nutrient-rich water rises to the surface, enhancing productivity.
upwelling
What is coastal upwelling driven by?
Wind-driven Ekman transport that moves surface waters offshore, drawing deeper water upward
Divergence of surface water at the equator caused by opposite Ekman transport on either side.
equatorial upwelling
What are the major phytoplankton groups?
Diatoms (silica), coccolithophores (calcium carbonate), cyanobacteria, cryptophytes, haptophyta
What determines phytoplankton size and composition?
Nutrient availability, temperature, and predator-prey dynamics.
Why are large phytoplankton important in productive systems?
They promote faster sinking of organic material and support larger zooplankton.
How does primary production vary with latitude? High latitudes……
strong seasonality with spring blooms
How does primary production vary with latitude? Low latitudes….
more constant but often nutrient-limited productivity.
What happens after the spring bloom?
Algae are grazed, nutrients sink below the thermocline, and are unavailable until vertical mixing resumes.
